Newbie question about RMS vs. Peak Power
bixby
difference between RMS and Peak Power? For example, a speaker has 100 watts
RMS and 250 watts peak power. What does this mean? Are there any other
important "terms" I should be aware of when shopping for a powered speaker?
Thanks and sorry for the silly question.
Pooh Bear
bixby wrote:
> I'm shopping for a powered speaker. Can someone please explain the
> difference between RMS and Peak Power? For example, a speaker has 100 watts
> RMS and 250 watts peak power. What does this mean?
It means whatever the manufacturer wants it to mean ! Technically 'peak power'
its exactly twice the RMS figure ( and an entirely useless number except to look
big ) when measured using the same method, so in this case I expect it's like
'peak music power' as used for car audio and we don't want to go there !
> Are there any other
> important "terms" I should be aware of when shopping for a powered speaker?
Maximum spl. Powered speakers only tell you the watts typically - not the
speaker efficiency ( often poor ).
Many cheap powered spekers have optimistic 'watts' figures ( you can't get
inside to measure it so they simply lie ) and don't use the best speakers so the
net result can be very disappointing.
Unfortunately you can't necessarily trust *any* of the figures comning from the
cheap vendors selling the low-grade Chinese stuff so give them a miss. You
should stick to the better well-known brands IMO.
Graham
bixby
Mackie SRM450 or a JBL EON10G2. Instead I'll have to settle for something a
little less expensive. Have you ever heard of a company called SoundTech?
They are an American audio company, and I was eyeing a 12" powered
speaker/mixer called the Revo ST12RXP. It would allow me to plug in a mic
or a guitar, even a drum machine to the lone speaker. For larger gigs, I
could use 2 of these with a mixer and call it a PA. Could you take a look
at the following links and let me know what you think of this speaker?
Thanks alot.
http://www.music123.com/SoundTech-ST12RXP-i152230.music
This eBay auction has some more info and photos and I can probably get it
for around US $229 if I am the only bidder.
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=7379677111&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
--
"Pooh Bear" <rabbitsfriend...@hotmail.com> wrote in message
news:43BB8366...@hotmail.com...
Pooh Bear
bixby wrote:
> Hey, thanks for the info. Ideally if I had the dough I would purchase a
> Mackie SRM450 or a JBL EON10G2.
The SRM450 sounds ok. Haven't heard the Eon.
> Instead I'll have to settle for something a
> little less expensive. Have you ever heard of a company called SoundTech?
Sure. Cheap and nasty.
> They are an American audio company,
I doubt very much is still actually made in America actually.
> and I was eyeing a 12" powered
> speaker/mixer called the Revo ST12RXP. It would allow me to plug in a mic
> or a guitar, even a drum machine to the lone speaker. For larger gigs, I
> could use 2 of these with a mixer and call it a PA. Could you take a look
> at the following links and let me know what you think of this speaker?
No meaningful specification Give it a miss.
SoundTech are a 'bottom feeder' brand.
Graham
bixby
>> and I was eyeing a 12" powered
>> speaker/mixer called the Revo ST12RXP. It would allow me to plug in a
>> mic
>> or a guitar, even a drum machine to the lone speaker. For larger gigs, I
>> could use 2 of these with a mixer and call it a PA. Could you take a
>> look
>> at the following links and let me know what you think of this speaker?
>
> No meaningful specification Give it a miss.
>
> SoundTech are a 'bottom feeder' brand.
Yeah, I suspected so... even their web site is ridiculously amateur and
provides no detailed product specifications. Thanks for your input, I think
I'll stay away.
Ron(UK)
>>
>>SoundTech are a 'bottom feeder' brand.
>
>
> Yeah, I suspected so... even their web site is ridiculously amateur and
> provides no detailed product specifications. Thanks for your input, I think
> I'll stay away.
>
The cabinet used is a common one, Italian I believe, also used by other
companies including FBT, Carlsbro, Studiospares and Studiomaster in one
variant or other. They are pretty tough and with the right drivers they
sound quite passable, however you`ve no idea what driver units Soundtech
are using, I suspect cheap chinese ones. If you must by cheap MI gear,
buy something with a recognisable name to it.
(IMO)
Ron(UK)
--
Lune Valley Audio
Public address system
Hire, Sales, Repairs
www.lunevalleyaudio.com
bixby
could you give this one a looksee and let me know what you think?
http://www.music123.com/Gemini-GX-250-i272460.music
--
"Ron(UK)" <r...@lunevalleyaudio.com> wrote in message
news:dpgpd0$1b7$1...@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
Ron(UK)
> Hi Ron, thanks for your input. Speaking of cheap but recogniseable names...
> could you give this one a looksee and let me know what you think?
> http://www.music123.com/Gemini-GX-250-i272460.music
>
I've no experience of them so I cant really comment other than to say
they look like cheap Chinese knock-off EV SX copies. According to the
manual they are only 100 watts which isnt an awful lot these days.
The only Gemini stuff I`ve seen has been some really awful DJ mixers.
We have something very very similar available here by name of Arena.
Cheap and cheerful, but poor quality. Lots of people buy them and some
are happy with them, they dont sound as good as they look tho.
Personally, I wouldn`t sell them to any of my customers
bixby
just hold out and buy something decent. A Mackie SRM450 is around US $600
or so... I think I could just wait and say I bought something decent.
Thanks for your help.
--
"Ron(UK)" <r...@lunevalleyaudio.com> wrote in message
news:dpgsv8$ev8$1...@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com...
George Gleason
"bixby" <unk...@known.com> wrote in message
news:43bc05ea$0$1661$c3e...@news.astraweb.com...
> Yeah, I think you're right. The more and more I think about it, I should
> just hold out and buy something decent. A Mackie SRM450 is around US $600
> or so... I think I could just wait and say I bought something decent.
> Thanks for your help.
>
I bought some for speaker on a stick announce type stuff and they are
astounding for the money spent
george
bixby
that it is really heavy, and I am just looking for something light and very
portable.
Actually, I found something for my particular use which is more suitable
than the Mackie SRM450... I should have bought one of these a while ago
instead of my accoustic guitar amp - a JBL EON10 G2 Powered 2-Way PA cab.
It's only 23 lbs. and measures 19.4 x 14.0 x 12.1 in. It's not as expensive
as the Mackie, and although it may not sound as good, the EON10 is rated
highly by alot of musicians (mostly soloists). It has a built in mixer so I
can connect a mic, guitar and even a drum machine/cd player all at the same
time. Can also expand with another JBL EON10 and a sub to form a more
complete PA, in this case using an external unpowered mixer. Now to start
saving my pennies!
http://www.zzounds.com/item--JBLEON10G2
Thanks for the info about the Behringer though.
--
"George Gleason" <tbmo...@peoplepc.com> wrote in message
news:uDTuf.4635$M%4.3...@newsread3.news.atl.earthlink.net...
George Gleason
very good sound
george
Pooh Bear
bixby wrote:
> Hi Ron, thanks for your input. Speaking of cheap but recogniseable names...
> could you give this one a looksee and let me know what you think?
> http://www.music123.com/Gemini-GX-250-i272460.music
You chose another cheap brand.
Gemini are known for their 'disco' gear. It's not in the pro-audio category.
Disco gear generally is a very poor relation to pro-audio.
Graham
Pooh Bear
bixby wrote:
> Yeah, I think you're right. The more and more I think about it, I should
> just hold out and buy something decent. A Mackie SRM450 is around US $600
> or so... I think I could just wait and say I bought something decent.
You ought also to take a look at dB powered speakers. e.g.....
http://www.directproaudio.com/product.cfm?directid=56059
Graham
Phil Allison
"Poopie Bear"
> You ought also to take a look at dB powered speakers. e.g.....
>
> http://www.directproaudio.com/product.cfm?directid=56059
>
** Is that an IEC inlet I see on the back ??
Not a pair of dodgy PowerCons as on their " pro install " models.
........ Phil
bixby
I am tired of buying garbage too. Like alot of people, I sometimes react
impulsively and get excited about somethig due to the super low price
compared to the price range of real pro audio equipment. But quality and
performance do come at a price. Another thing about Gemini and SoundTech I
thought about, is that while there is a market for their produts to novices
and or really price concious shoppers, I want to use equipment that will
impress other musicians and audiophiles. I'm glad to have had a chance to
get some input on products from this group, because some of the marketing
these companies use is a little misleading in that they make it sound like
their product is just as good as the top end stuff.
Thanks for the tip on the DB powered speakers. They look good, but for
service and support I think I will stick to a North American brand, Mackie,
JBL or Yorkville. If the DB speakers ever crap out, I don't want to be
shipping them back to Italy! HAHA.
Atek Rools
What wrong with powercons?
Phil Allison
"Atek Rools"
>
> > You ought also to take a look at dB powered speakers. e.g.....
>> >
>> > http://www.directproaudio.com/product.cfm?directid=56059
>> >
>>
>>
>> ** Is that an IEC inlet I see on the back ??
>>
>>
>> Not a pair of dodgy PowerCons as on their " pro install " models.
>>
>>
>
>
** Try doing a GG search on the word in this NG.
The PowerCon is not legally approved by safety authorities for general
appliance use.
It is permitted for use in installations of equipment.
........ Phil
Saxology
RMS power is an "average power" spec. I should be equivalent to .707 * peak
power. So, one might ask, why doesn't it work in this case? Peak power is
a real spec game. Peak, or instantaneous power is the peak voltage x peak
current. The problem is that the mfg might spec peak power in the "sweet
spot" of the speaker. They might spec it at 1kHz for example. Even RMS
gets limited in many specs, to a small frequency band with specific
distortion specs. What I look for is the difference between peak*.707 and
RMS. Since 250w means u should be able to run 175RMS and the spec only
allows 100RMS I would figure it to be an "inexpensive" product or a "hyped"
spec. In general, use the RMS numbers to determine general power between
speakers you are interested in.
Another spec u will see is "program power" or "average power". For an AC
waveform, RMS is defined to be the average. So, if average is specified,
some specmanship is being applied. Program power is something I have never
seen a definition of. It is suppoed to be RMS-like and kind of like
"average for your application" but who knows how each mfg interprets it.
Good luck,
Sax
bixby
good to know and I'll keep that in mind. Another question regarding
specs -- when reading something like the following: 10" Powered Two Way
Aluminum Die Cast Woofer Loudspeaker With 50.5 mm Voice Coil
what the heck is a voice coil and how does size (ie. 50.5 mm) play into
performance?
--
"Saxology" <saxolo...@yahoo.com> wrote in message
news:y21vf.4916$M%4.1...@newsread3.news.atl.earthlink.net...
Pooh Bear
Phil Allison wrote:
The distinction as I understand it is that it's not approved for use on
*domestic* ( home use ) equipment.
Graham
Pooh Bear
Saxology wrote:
> "bixby" <unk...@known.com> wrote in message
> news:43bb74b6$0$1782$c3e...@news.astraweb.com...
> > I'm shopping for a powered speaker. Can someone please explain the
> > difference between RMS and Peak Power? For example, a speaker has 100
> > watts RMS and 250 watts peak power. What does this mean? Are there any
> > other important "terms" I should be aware of when shopping for a powered
> > speaker? Thanks and sorry for the silly question.
> >
>
> RMS power is an "average power" spec. I should be equivalent to .707 * peak
> power.
Actually the 0.707 x peak is the equation for voltage / current.
Peak power is twice RMS. It's only use here is to make an artifically large
number. It can also be confused ( by the maker it seems ) with the old 'music
power' rating too. The number quoted seems to be what was once called 'peak
music power'.
Graham
Pooh Bear
Saxology wrote:
The above is a heap of unadulterated rubbish.
It sickens me to see George and Phildo hound Arny for his 'lies' when his
mistakes are mild in comparison to the above.
I challenge George and Phildo to correct the above post point by point. I expect
PA will do it on his own initiative though !
Graham
Pooh Bear
bixby wrote:
> Thanks for taking the time to write all that. The equation .707*peak is
> good to know and I'll keep that in mind.
It's wrong. In fact I didn't see a single thing that Sax got right. Please
forget everythig he said or you're going to get into trouble with specs.
> Another question regarding
> specs -- when reading something like the following: 10" Powered Two Way
> Aluminum Die Cast Woofer Loudspeaker With 50.5 mm Voice Coil
>
> what the heck is a voice coil and how does size (ie. 50.5 mm) play into
> performance?
The voice coil is what moves the speaker cone. Its the bit that sits in the
mgnet assembly. It works as a linear motor. Voice coil size gives a clue as to
power rating. a 2 inch voice coil is on the small side for a seiour 12 or 15
inch SR speaker. Most used in this application tend to have 2.5 or 3 inch voice
coils.
For a smaller 10" speaker however 2" is quite normal.
It's not something you actually need to concern yourself about directly. It's
used as a marketing gimmick for the most part. Look for factual data like rms
power rating and speaker sensitivity ( dB/W ) or SPL figures and ignore the
marketing froth.
Graham
Phil Allison
"Poopie Bear Faced L I A R "
aka Graham Stevenson
Troll, criminal net stalker and psychopath.
> The distinction as I understand it...
** But YOU do not understand any *fucking* thing.
YOU never have & YOU never will.
Because YOU are a vile, posturing pommy
F U C K H E A D !!
........ Phil
Phil Allison
"Pooh Bear"
** Pigs will fly ......
> I expect
> PA will do it on his own initiative though !
** Saxology has a hide ten times thicker than any African Rhino.
But with less brain.
He is way beyond being defamable.
Be like trying to defame Satan himself.
........ Phil
Ron(UK)
> Thanks for taking the time to write all that. The equation .707*peak is
> good to know and I'll keep that in mind. Another question regarding
> specs -- when reading something like the following: 10" Powered Two Way
> Aluminum Die Cast Woofer Loudspeaker With 50.5 mm Voice Coil
>
> what the heck is a voice coil and how does size (ie. 50.5 mm) play into
> performance?
>
What the heck is a 'two way 10" woofer' Do they mean it has a twin cone?
In which case it`s neither a woofer or a two way speaker, it`s a
compromise.
Ron(UK)
Pooh Bear
"Ron(UK)" wrote:
I assumed the spec was snipped. A true coaxial ( 2 driver ) 10" would likely
sound very sweet though.
Graham
bixby
list. It was written exactly as that.
http://www.music123.com/Gemini-GX-250-i156073.music
--
"Pooh Bear" <rabbitsfriend...@hotmail.com> wrote in message
news:43BCE4B9...@hotmail.com...
Pooh Bear
bixby wrote:
> Guys, actually I copy/pasted the line from the famous Gemini GX-250 spec
> list. It was written exactly as that.
> http://www.music123.com/Gemini-GX-250-i156073.music
Yup.
Badly written vaguely ambiguous spec typical of Gemini and its *resellers*. Not
one item mentioning it's power or SPL at all.
You should also note that outfits that sell disco crap are less likely to be
technically competent too. A decent pro-audio reseller will actually understand
what a spec means and not just spout a load of nonsense.
Graham
Ron(UK)
> Guys, actually I copy/pasted the line from the famous Gemini GX-250 spec
> list. It was written exactly as that.
> http://www.music123.com/Gemini-GX-250-i156073.music
>
The point we're making is that the driver sounds very much like a
cheap chinese 'dual cone' unit. As Graham said a true dual concentric
10" combination would sound very nice indeed, but would cost more than
the whole Gemini speaker.
Personally, I`m not a great fan of Eons btw, the only thing they have
going for them IMO is their light weight. There`s a lot of stuff which
sounds a lot better and is more reliable at a similar price.
Arny Krueger
> Thanks for taking the time to write all that.
Like Graham says, regrettably it was pretty much all wrong.
> The equation .707*peak is good to know and I'll keep that in
> mind.
0.707 is the inverse of the square root of two or 1/1.414 . It is a good
number to remember, but its meaning is different, and Graham corrected it
properly, but briefly.
0.707 times peak is the average value of a sine wave. Think of chopping off
the peaks to fill in the valleys. So, a sine wave with a peak value of 10
volts has an average value of 7.07 volts.
Power is based on the square of voltage, so the power represented by a 7.07
volt sine wave is half that of a 10 volt sine wave.
> Another question regarding specs -- when reading
> something like the following: 10" Powered Two Way
> Aluminum Die Cast Woofer Loudspeaker With 50.5 mm Voice
> Coil
> what the heck is a voice coil and how does size (ie. 50.5
> mm) play into performance?
As you probably know, the voice coil is the portion of a cone speaker that
provides the force that moves the cone around. Mechanically, a larger voice
coil provides a more distributed and rigid source of force that moves the
cone back and forth.
Almost all of the energy that is applied to a speaker is turned into heat in
the voice coil. Therefore it is important that the voice coil be able to
dissipate heat. A larger voice coil can dissipate more heat with less
temperature rise.
Obviously, there are diminishing returns. As Graham said, 50 mm is a good
large voice coil for a 10 in speaker. Anything under an inch would be way to
small.
Arny Krueger
in message news:43BCCFA7...@hotmail.com
This is not the worst piece of advice that Saxology has posted on AAPLS.
That dubious honor has to belong to the following post:
http://groups.google.com/group/alt.audio.pro.live-sound/msg/8b1bde120cc486de
In this post Saxology recommended cleaning the circuit boards of an 02R96 in
an automotive vapor degreaser. That would be a $13,000 (list price) mistake,
more or less.
Saxology has been piling-on George's and Phildo's recent attacks on me time
after time. I suspected there was a reason, and I found it in Google. Back
in 2004 I made the mistake of agreeing with just about everybody else that
Saxology had truely given horrific advice about how to clean up that 02R96.
> I challenge George and Phildo to correct the above post
> point by point. I expect PA will do it on his own
> initiative though !
Google shows that Phildo and George fell down in their self-appointed roles
of *AAPLS protectors of truth* when Saxology gave the earlier horrific
advice, as well. They just aren't reliable.
Atek Rools
where it written peak = 2x rms? now that rubbish!
Arny Krueger
news:1136479530.4...@f14g2000cwb.googlegroups.com
> Pooh Bear wrote:
>> Peak power is twice RMS. It's only use here is to make
>> an artifically large number. It can also be confused (
>> by the maker it seems ) with the old 'music power'
>> rating too. The number quoted seems to be what was once
>> called 'peak music power'.
> where it written peak = 2x rms? now that rubbish!
The peak voltage of a sine wave is 1.414 times its RMS value.
If you use that peak voltage, as irrelevant as it is to audio waveforms, to
compute peak power which some marketing types seem to be prone to do, you
end up with:
Peak Power = 2x RMS
Don't get me started about what's wrong with this! ;-)
I'm sure Graham knows...
GregS
Peak will go up of course with a unregulated power supply amplifier. How
long the power remains in the burst region is up to a number
of factors including special design. Very real. Peak is peak,
however I have also seem peak to peak!
greg
Pooh Bear
Atek Rools wrote:
In the text books you clown.
If you knew something about maths you could work it out for yourself too.
Graham
Atek Rools
Pooh Bear wrote:
> Atek Rools wrote:
>
>
> > where it written peak = 2x rms? now that rubbish!
>
> In the text books you clown.
>
> If you knew something about maths you could work it out for yourself too.
with respect to speakers? why is not always this way then? I see
loudspekers with very higher peak than 2x rms figures. others not so
much.
seems dumb thing to assume. some manufactures may intend "peak
transient" power.
Pooh Bear
GregS wrote:
You're talking about a different kind of 'peak'. What you're referring to has traditionally
been called 'music power', the wattage that can be produced briefly before the power supply
'sags' under load.
Today this may sometimes be measured as 'toneburst rating'.
And yes PMPO ( peak music power output ) is used for car audio for example. It's a way of
inflating the numbers for marketing purposes. In this case both the peak value of the output
( the arithmetical 2 x rms ) is taken in addition to the toneburst figure ! An utterly bogus
figure.
Graham
Pooh Bear
Atek Rools wrote:
> Pooh Bear wrote:
> > Atek Rools wrote:
> >
> >
> > > where it written peak = 2x rms? now that rubbish!
> >
> > In the text books you clown.
> >
> > If you knew something about maths you could work it out for yourself too.
>
> with respect to speakers? why is not always this way then? I see
> loudspekers with very higher peak than 2x rms figures. others not so
> much.
The peak = 2 x rms is a mathematical relationship for sinewaves..
> seems dumb thing to assume. some manufactures may intend "peak
> transient" power.
This is why use of the word peak can be very misleading.
Graham
TimPerry
> "Pooh Bear" <rabbitsfriend...@hotmail.com> wrote in message
> news:43BC3B3E...@hotmail.com...
>
> >> Hi Ron, thanks for your input. Speaking of cheap but recogniseable
> >> names...
> >> could you give this one a looksee and let me know what you think?
> >> http://www.music123.com/Gemini-GX-250-i272460.music
> >
> > You chose another cheap brand.
> >
> > Gemini are known for their 'disco' gear. It's not in the pro-audio
> > category.
> > Disco gear generally is a very poor relation to pro-audio.
>
> I am tired of buying garbage too. Like alot of people, I sometimes react
> impulsively and get excited about somethig due to the super low price
> compared to the price range of real pro audio equipment. But quality and
> performance do come at a price. Another thing about Gemini and SoundTech
I
> thought about, is that while there is a market for their produts to
novices
> and or really price concious shoppers, I want to use equipment that will
> impress other musicians
why? why not get stuff that works reliably?
>and audiophiles.
can't be done: audiophiles are only impressed by themselves.
I'm glad to have had a chance to
> get some input on products from this group, because some of the marketing
> these companies use is a little misleading in that they make it sound like
> their product is just as good as the top end stuff.
>
that's what the marketing department is there for.
> Thanks for the tip on the DB powered speakers. They look good, but for
> service and support I think I will stick to a North American brand,
Mackie,
> JBL or Yorkville. If the DB speakers ever crap out, I don't want to be
> shipping them back to Italy! HAHA.
>
>
think global economy: if a product or system has no proprietary components
it can be maintained as long as the needed standard components can be
obtained.
example: at one point in the past a Turbosound system was greatly desired in
the US as being "the one to have". being a UK company didn't stop a lot of
imports or sales.
presently Nexo (a French company) has found wide acceptance among touring
acts.
bixby
Of course, I totally agree. What I meant is that they will be impressed
knowing I am using reliable and quality gear, not some cheap knockoff.
Rodney
bixby wrote:
> I'm shopping for a powered speaker. Can someone please explain the
> difference between RMS and Peak Power? For example, a speaker has 100 watts
> RMS and 250 watts peak power. What does this mean? Are there any other
> important "terms" I should be aware of when shopping for a powered speaker?
> Thanks and sorry for the silly question.
Have a look at the paper in the following link.
Rodney
John Corbett
<ar...@hotpop.com> wrote:
> 0.707 times peak is the average value of a sine wave. Think of chopping off
> the peaks to fill in the valleys. So, a sine wave with a peak value of 10
> volts has an average value of 7.07 volts.
Arny seems to have confused average and rms values.
Over a complete cycle, the _average_ value of a sine wave is zero.
The average of the _absolute value_ of a sine wave, i.e., a rectified sine
wave, is (2/pi) times the peak amplitide. That is about .637 times peak,
and is what you would get by "chopping off the peaks to fill in the
valleys" for just the positive half-cycle of the original sine wave.
The _rms_ value (sometimes called effective value) of a sine wave is
(1/sqrt(2)) times peak, or about .707 times peak, but you won't get that
by "chopping off
the peaks to fill in the valleys" of the original sine wave.
Pooh Bear
John Corbett wrote:
> In article <LYqdnfI5VtO5gCDe...@comcast.com>, "Arny Krueger"
> <ar...@hotpop.com> wrote:
>
> > 0.707 times peak is the average value of a sine wave. Think of chopping off
> > the peaks to fill in the valleys. So, a sine wave with a peak value of 10
> > volts has an average value of 7.07 volts.
>
> Arny seems to have confused average and rms values.
>
> Over a complete cycle, the _average_ value of a sine wave is zero.
For voltage that's true but not very helpful
For power that's totally untrue.
Yey another idiot.
Graham
Arny Krueger
news:corbett-0601...@0.0.0.0
> In article
> <LYqdnfI5VtO5gCDe...@comcast.com>, "Arny
> Krueger" <ar...@hotpop.com> wrote:
>
>
>> 0.707 times peak is the average value of a sine wave.
>> Think of chopping off the peaks to fill in the valleys.
>> So, a sine wave with a peak value of 10 volts has an
>> average value of 7.07 volts.
> Arny seems to have confused average and rms values.
I think that would be exactly right, my answer above was based on some
erroneous and incomplete memories.
> Over a complete cycle, the _average_ value of a sine wave
> is zero.
That would be a very ludicrous and pedantic solution to the problem.
> The average of the _absolute value_ of a sine wave, i.e.,
> a rectified sine wave, is (2/pi) times the peak
> amplitide. That is about .637 times peak, and is what
> you would get by "chopping off the peaks to fill in the
> valleys" for just the positive half-cycle of the original
> sine wave.
As compared to the previous ludicrous and pedantic answer, this would be a
proper and relevant solution to the problem.
As a check I made a spread sheet of the values of a sine wave and as I
increased the number of points I watched the result become asymptotic to the
value given above. This confirmed the number I worked out using the
integration I learned in first semester calculus some 40-odd years ago.
> The _rms_ value (sometimes called effective value) of a
> sine wave is (1/sqrt(2)) times peak, or about .707 times
> peak, but you won't get that by "chopping off
> the peaks to fill in the valleys" of the original sine
> wave.
Agreed, my answer about average values was an error.
My confusion came from the fact that most common (non-true-RMS) voltmeters
actually measure the average value of the signal, but are calibrated to
present the equvalent RMS value, presuming the signal is a sine wave. This
works for measuring sine waves, but it does not give a reasonable result for
more complex waves, which includes a lot of audio applications.
Every once in a while it's good to get back to basics.
Skeeter
> I'm shopping for a powered speaker. Can someone please explain the
> difference between RMS and Peak Power?
Rather than fill up this post with math, please accept that the advice
given be a few knowledgeable posters is correct when they tell you that
RMS spec is half of the Peak Power spec.
The RMS spec is more meaningful because it describes the maximum
continuous power that you should expect the amplifier to deliver. Peak
Power is the maximum INSTANTANEOUS power that the amplifier can provide
for a brief instant of time.
Regardless, the RMS or any other power spec doesn't mean a whole lot
until you can know how much power is available across the range of
audible frequencies that you will be expecting to hear from your
speakers. This is what a Frequency Response specification is used for.
For a general purpose, full range amplifier it should describe how
linear the amplifier will provide power across the audible range,
normally 20Hz to 20kHz. The Frequency Response specification only is
meaningful if it specifies how much variation in dB can we expect over
the 20-20k range.
ie: 100 watts RMS, 20Hz to 20kHz +/- 0.1dB
The above tells me that I should expect the amplifier to deliver a
maximum of 100 watts continuously (100 watts RMS) without noticeable
peaks or dropouts of power delivery (+/- 0.1dB) across the audible
frequency range (20Hz to 20kHz).
Without this type of accountability from the manufacturer, it is simply
a crapshoot as to what the hell you are getting.
NOW PLEASE NOTE that all that I have provided above deals with power
amplifiers. NOT SPEAKERS. Speakers do not make power, they use power
to make sound, it's a different perspective on specs when dealing with
speakers.
Powered speakers become a little confusing because they are an
amplifier and a speaker, thus they are two components in one package.
> For example, a speaker has 100 watts RMS and 250 watts peak power.
> What does this mean?
>From the explanation above, it means that this manufacturer is not
describing anything meaningful to you at all. It looks vague and
misleading to say the least.
> Are there any other important "terms" I should be aware of when shopping for a
> powered speaker?
Yes!!! The speaker should have the following specs
1) Frequency response of the speaker's output qualified within +/- 3dB
at low and high Sound Pressure Levels.
2) Maximum Continuous Sound Pressure Level at 1 or 2 metres. (you can
figure real levels at longer distances by subtracting 3dB every time
you double the distance given in the spec)
3) Mono amped, bi-amped, or tri-amped. Having separate amplifiers for
each speaker driver is preferable for cleaner sound with more headroom.
4) High Frequency Dispersion angles are good to know. Usually the
broader, the better in full range, small speakers. It makes FOH
speaker positioning less critical when the highs are dispersed fairly
evenly. Narrower high frequency dispersions are normally used for
"long throw" tweeter horns in large systems.
5) Speaker/Amplifier protection devices. Very good to have. Range
from active, or passive limiters/filters, light bulbs, power resistor
circuits, circuit breakers, or fuses, etc... Circuit breakers and
fuses are the least desirable as when they go... the music stops.
6) Nice to have EQ and/or volume trim adjustments. Because it is an
amplified speaker, it is handy to have some general volume and
frequency trimming adjustments.
7) Mic and line inputs is a good thing to have for some situations.
8) Line outputs are great for interconnecting speakers when required.
9) Nice to have some type of clipping indicator like an LED or light
bulb to signal when the amp is getting stressed.
10) Pole mounts, handles, weight, construction materials, grilles,
dimensions, etc... you will need to know how you can handle, setup and
generally deal with the speakers.
There's more that I likely will think of later, but I think this is a
good start. There is a lot of opinions about voice coil size, magnet
type, cast or stamped speaker basket, etc... it's really of no general
consequence if the speaker is a good design that is of quality
manufacture. Post any further questions and I'll try to keep my eyes
open.
> Thanks and sorry for the silly question.
There are no silly or stupid questions... just those that do not get
asked, eh?
Cheers,
Skeeter
John Corbett
<rabbitsfriend...@hotmail.com> wrote:
> John Corbett wrote:
> > Over a complete cycle, the _average_ value of a sine wave is zero.
>
> For voltage that's true but not very helpful
It is actually very helpful---see below
>
> For power that's totally untrue.
Nonsense.
>
> Yey another idiot.
>
> Graham
The statement about a zero average value for a sine wave is solid
mathematical fact. It does not depend on an interpretation as voltage or
power, and the claim that it is true only for voltage but not power is
absurd.
Consider a pure sine wave signal at fixed frequency f with peak amplitude A > 0.
We can write the instantaneous voltage as a function of time,
V(t) = A sin(wt)
where w = 2 pi f is the angular frequency.
The average value of V is zero, as you acknowledged.
Now consider two situations:
(1) For a reactive load, the current has the form
I(t) = B cos(wt)
and it too has an average value of zero.
Note that there is a quarter-cycle phase shift between V and I.
The instantaneous power is then
P(t) = V(t) * I(t)
= (A sin(wt)) (B cos(wt))
= A B sin(wt) cos(wt)
= (1/2) A B sin(2wt)
by an elementary trig identity.
So in this case instantaneous power is a sine wave with amplitude AB and
frequency twice that of the original voltage and current.
The average of this sine wave is zero, as it should be. Recall that there
is no power dissipated in a purely reactive load.
(2) For a resistive load, the current will have the form
I(t) = V(t) * (1/R) = A sin(wt) * (1/R) = (A/R) sin(wt) = C sin(wt)
Note that for a resistive load the current and voltage are in phase and C = A/R.
Now the instantaneous power is
P(t) = V(t) * I(t)
= (A sin(wt)) (C sin(wt))
= A C [ sin(wt) ]^2
= A C (1/2) [ 1 - cos(2wt) ]
= (AC/2) - (AC/2)cos(2wt)
using another elementary trig identity.
Note that this is not just a sinusoidal wave---there is a constant term as well.
Now take the average. The average of the cosine term is zero, but the
constant term gives the average power, namely, AC/2 or ( (1/2)*A^2 )/R as
we expect.
Arny Krueger
> In article <43BEC3CC...@hotmail.com>, Pooh Bear
> <rabbitsfriend...@hotmail.com> wrote:
>
>> John Corbett wrote:
>> > Over a complete cycle, the _average_ value of a sine wave is zero.
>> For voltage that's true but not very helpful
> It is actually very helpful---see below
>> For power that's totally untrue.
> Nonsense.
>> Yey another idiot.
You forgot the pedantic part. ;-)
>> Graham
Note to Graham:
Agree with Corbett and it seems to shut him up real quick. ;-)
John Corbett
<ar...@hotpop.com> wrote:
> "John Corbett" <cor...@stat.umn.edu> wrote in message
> news:corbett-0601...@0.0.0.0
> > In article
> > <LYqdnfI5VtO5gCDe...@comcast.com>, "Arny
> > Krueger" <ar...@hotpop.com> wrote:
> >
> >
> >> 0.707 times peak is the average value of a sine wave.
> >> Think of chopping off the peaks to fill in the valleys.
> >> So, a sine wave with a peak value of 10 volts has an
> >> average value of 7.07 volts.
>
> > Arny seems to have confused average and rms values.
>
> I think that would be exactly right, my answer above was based on some
> erroneous and incomplete memories.
>
> > Over a complete cycle, the _average_ value of a sine wave
> > is zero.
>
> That would be a very ludicrous and pedantic solution to the problem.
Not at all. As I wrote elsewhere in this thread in reply to Pooh Bear,
the fact that the average value of a sine wave is zero is an integral (!)
part of how we compute average power for both reactive and resistive
loads.
Also, remember that the average of almost any waveform is its DC
component; this works precisely because all the sinusoidal components have
zero average over whole cycles.
It is far from a ludicrous and pedantic observation.
>
> > The average of the _absolute value_ of a sine wave, i.e.,
> > a rectified sine wave, is (2/pi) times the peak
> > amplitide. That is about .637 times peak, and is what
> > you would get by "chopping off the peaks to fill in the
> > valleys" for just the positive half-cycle of the original
> > sine wave.
>
> As compared to the previous ludicrous and pedantic answer, this would be a
> proper and relevant solution to the problem.
The only ludicrous answer is yours; of course any correct answer will
appear proper and relevant compared to what you had written.
>
> As a check I made a spread sheet of the values of a sine wave and as I
> increased the number of points I watched the result become asymptotic to the
> value given above. This confirmed the number I worked out using the
> integration I learned in first semester calculus some 40-odd years ago.
Now _that_ is ludicrous---spreadsheet asymptotics!
>
> > The _rms_ value (sometimes called effective value) of a
> > sine wave is (1/sqrt(2)) times peak, or about .707 times
> > peak, but you won't get that by "chopping off
> > the peaks to fill in the valleys" of the original sine
> > wave.
>
> Agreed, my answer about average values was an error.
>
> My confusion came from the fact that most common (non-true-RMS) voltmeters
> actually measure the average value of the signal, but are calibrated to
> present the equvalent RMS value, presuming the signal is a sine wave. This
> works for measuring sine waves, but it does not give a reasonable result for
> more complex waves, which includes a lot of audio applications.
Almost correct---remember that the so-called average-responding meter is
averaging after rectifying. Then it presents about 1.11 times that
average (absolute) value as the RMS value.
Pooh Bear
John Corbett wrote:
> In article <43BEC3CC...@hotmail.com>, Pooh Bear
> <rabbitsfriend...@hotmail.com> wrote:
>
> > John Corbett wrote:
>
> > > Over a complete cycle, the _average_ value of a sine wave is zero.
> >
> > For voltage that's true but not very helpful
>
> It is actually very helpful---see below
>
> >
> > For power that's totally untrue.
>
> Nonsense.
>
> >
> > Yey another idiot.
> >
> > Graham
>
> The statement about a zero average value for a sine wave is solid
> mathematical fact.
But completely unhelpul still.
> It does not depend on an interpretation as voltage or
> power, and the claim that it is true only for voltage but not power is
> absurd.
No it's fact.
Power is a 'square term' e.g V^2/R or I^2xR
Therefore it always has a positive value.
If you think about it *negative power* makes no sense.
If you managed to draw an alternaive conclusion from your 'maths' you simply made a
mistake.
Graham
Pooh Bear
Rodney wrote:
That's a decent read. Well presented.
Graham
Phil Allison
"Skeeter"
>
> Rather than fill up this post with math, please accept that the advice
> given be a few knowledgeable posters is correct when they tell you that
> RMS spec is half of the Peak Power spec.
** That is simply false.
You have confused the "peak power" rating with the term " watts peak " ( =
watts based on the peak value of a sine wave, not its rms value. )
> The RMS spec is more meaningful because it describes the maximum
> continuous power that you should expect the amplifier to deliver. Peak
> Power is the maximum INSTANTANEOUS power that the amplifier can provide
> for a brief instant of time.
** There are any number of amplifiers, both domestic and pro audio types,
that are designed to deliver short bursts of power well above the continuous
rms value for significant periods of time. This enables them to reproduce
typical music signals without clipping distortion at the same output levels
as amplifiers of *much higher * continuous power rating.
One example is the Jands SR3000:
Sine wave power = 750 wpc @ 4ohms ( 55 volts rms)
Peak power ( sine wave burst) = 2200 wpc @ 4 ohms ( 94 volts rms.)
The 2200 watt rating is based on repeated 20 cycle, 1 kHz sine wave bursts
and the rms value used to calculate the watts figure. That could also be
given as 4400 watts peak @ 4 ohms (133 volts peak ).
BTW:
In the case of a powered speaker system, the makers ought to supply a
maximum SPL figure in dBs that the box can produce cleanly.
But while ever the market is remains obsessed with electrical watts instead
of actual, usable sound that will never happen.
......... Phil
Phil Allison
"Poopie Bear faced LIAR "
> Power is a 'square term' e.g V^2/R or I^2xR
>
> Therefore it always has a positive value.
** True *ONLY* when the load is a pure resistance.
In the general case, instantaneous power = V . I
where V and I can be positive or negative at any instant.
The average value of V . I over some period is the power level.
With a reactive load ( ie loudspeakers) V . I can be positive or negative
and if the load is a pure reactance the average value is zero for any whole
number of cycles.
> If you think about it *negative power* makes no sense.
** Makes perfect sense when you allow that power can flow to and from a
load.
........ Phil
Phil Allison
"Pooh Bear"
> Rodney wrote:
>>
>> http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definition'
>
> That's a decent read. Well presented.
>
** It is full of dumb technical errors, false assertions and half truths.
IOW John Mayer's marketing drivel.
.......... Phil
Pooh Bear
Phil Allison wrote:
I really didn't fancy bringing complex impedance into the discusssion. Much as
it indeed does apply to loudspeakers.
Graham
TimPerry
> > why? why not get stuff that works reliably?
>
> Of course, I totally agree. What I meant is that they will be impressed
> knowing I am using reliable and quality gear, not some cheap knockoff.
>
>
if it gets you gigs, go for it
if it makes you happy, go for it
if it gives you "return on investment", all the better
we all like quality tools. sometimes the cheap 88 cent screwdriver works
fine.
BobFli...@spamnomore.ca
wrote:
I wish you told me that BEFORE I downloaded it!
Phil you need to write an internet book!
"Audio Technology" by Phil Alison!
BobFli...@spamnomore.ca
wrote:
>
>"Skeeter"
>>
>> Rather than fill up this post with math, please accept that the advice
>> given be a few knowledgeable posters is correct when they tell you that
>> RMS spec is half of the Peak Power spec.
>
>
>** That is simply false.
>
>You have confused the "peak power" rating with the term " watts peak " ( =
>watts based on the peak value of a sine wave, not its rms value. )
>
>
>> The RMS spec is more meaningful because it describes the maximum
>> continuous power that you should expect the amplifier to deliver. Peak
>> Power is the maximum INSTANTANEOUS power that the amplifier can provide
>> for a brief instant of time.
>
>
>** There are any number of amplifiers, both domestic and pro audio types,
>that are designed to deliver short bursts of power well above the continuous
>rms value for significant periods of time. This enables them to reproduce
>typical music signals without clipping distortion at the same output levels
>as amplifiers of *much higher * continuous power rating.
>
>One example is the Jands SR3000:
>
>Sine wave power = 750 wpc @ 4ohms ( 55 volts rms)
>
>Peak power ( sine wave burst) = 2200 wpc @ 4 ohms ( 94 volts rms.)
Does this spec mean that the amplifier power supply dropped down during the
continuous test? And the burst left the voltage up twice as high?
That would mean that a square wave continuous test would drop the voltage even
more, giving a lower than double 'peak music power' rating?
Wouldn't this mean the amp has a poor supply? Needs more capacity?
Or perhaps the signal is just lost in the output drivers... I once tested a
power amp stage with both 30 amp transistors, and 16 amp transistors, and the 30
amp jobs could produce twice the continuous output before clipping, which
surprised me a bit!
>The 2200 watt rating is based on repeated 20 cycle, 1 kHz sine wave bursts
>and the rms value used to calculate the watts figure. That could also be
>given as 4400 watts peak @ 4 ohms (133 volts peak ).
>
>
>BTW:
>
>In the case of a powered speaker system, the makers ought to supply a
>maximum SPL figure in dBs that the box can produce cleanly.
NOW yer talkin!
Phil Allison
<BobFli...@spamnomore.ca
"Phil Allison" wrote:
>
>>** There are any number of amplifiers, both domestic and pro audio types,
>>that are designed to deliver short bursts of power well above the
>>continuous
>>rms value for significant periods of time. This enables them to reproduce
>>typical music signals without clipping distortion at the same output
>>levels
>>as amplifiers of *much higher * continuous power rating.
>>
>>One example is the Jands SR3000:
>>
>>Sine wave power = 750 wpc @ 4ohms ( 55 volts rms)
>>
>>Peak power ( sine wave burst) = 2200 wpc @ 4 ohms ( 94 volts rms.)
>
>
> Does this spec mean that the amplifier power supply dropped down during
> the
> continuous test? And the burst left the voltage up twice as high?
** Basically - yes.
That is how "burst power" amps work.
> That would mean that a square wave continuous test would drop the voltage
> even
> more, giving a lower than double 'peak music power' rating?
** No, the amp has a big toroidal PSU that supplies a solid +/- 75 volts
AND a soggy +/-150 volts.
The output stage operates with these 4 DC supply rails like many QSCs,
Carvers etc etc.
> Wouldn't this mean the amp has a poor supply? Needs more capacity?
** You are missing the point.
The SR3000 is only 2RU high & weighs 19kg - yet can equal the performance
on LIVE MUSIC of a much bigger conventional amp. It is also low cost
design with no fancy technology.
Plus it uses lots of Motorola TO3 devices - no "flat earth" rubbish.
Just happens to be an absolute PIG to service though !
........ Phil
Saxology
>> > I'm shopping for a powered speaker. Can someone please explain the
>> > difference between RMS and Peak Power? For example, a speaker has 100
>> > watts RMS and 250 watts peak power. What does this mean? Are there
>> > any
>> > other important "terms" I should be aware of when shopping for a
>> > powered
>> > speaker? Thanks and sorry for the silly question.
>> >
>>
>> peak
>> power.
>
> Actually the 0.707 x peak is the equation for voltage / current.
>
> large
> number. It can also be confused ( by the maker it seems ) with the old
> 'music
> power' rating too. The number quoted seems to be what was once called
> 'peak
> music power'.
>
>
That was poohbear who said 2x. That is wrong. If he knew enough math he
would integrate the power equation over time 0 to infinity and would
discover that the integral drops out a 1/sqr rt of 2 which yields the .707
factor. Do the math poopoo, and shut up with that bs you dribble. You need
to get a clue before telling others I am wrong. In fact, you use BS hifi
jargon. My facts are exact. .707 = 1/1.41414 (2^.5 = 1.41414).
Fool.
-Sax
Saxology
>
>
> GregS wrote:
>
>> In article <dOqdnbE5d5_...@comcast.com>, "Arny Krueger"
>> <ar...@hotpop.com> wrote:
>> >"Atek Rools" <atek...@yahoo.com> wrote in message
>> >news:1136479530.4...@f14g2000cwb.googlegroups.com
>> >> Pooh Bear wrote:
>> >
>> >
>> >>> Peak power is twice RMS. It's only use here is to make
>> >>> an artifically large number. It can also be confused (
>> >>> by the maker it seems ) with the old 'music power'
>> >>> rating too. The number quoted seems to be what was once
>> >>> called 'peak music power'.
>> >
>> >> where it written peak = 2x rms? now that rubbish!
You are correct.
>> >
>> >The peak voltage of a sine wave is 1.414 times its RMS value.
1/1.414141 = .707 so, we agree. Poopoo is lost.
>> >
>> >If you use that peak voltage, as irrelevant as it is to audio waveforms,
>> >to
>> >compute peak power which some marketing types seem to be prone to do,
>> >you
>> >end up with:
<snip crap>
All functions can be written as a sum of sines, therefore the .707 factor
applies to all audio, period. Well, with the exception of hifi audio where
pig shit in the ear seems to rule the air waves.
-Sax
Saxology
<snip>
>
> In the text books you clown.
Name the book.
>
> If you knew something about maths you could work it out for yourself too.
I do, and you are simply wrong.
Go to the post with the sine wave equation and integrate it over time.
>
> Graham
>
-Sax
>
Saxology
>
>
> Saxology wrote:
>
>> "bixby" <unk...@known.com> wrote in message
>> news:43bb74b6$0$1782$c3e...@news.astraweb.com...
>> > I'm shopping for a powered speaker. Can someone please explain the
>> > difference between RMS and Peak Power? For example, a speaker has 100
>> > watts RMS and 250 watts peak power. What does this mean? Are there
>> > any
>> > other important "terms" I should be aware of when shopping for a
>> > powered
>> > speaker? Thanks and sorry for the silly question.
>> >
>>
>> RMS power is an "average power" spec. I should be equivalent to .707 *
>> peak
>> is
>> a real spec game. Peak, or instantaneous power is the peak voltage x
>> peak
>> current. The problem is that the mfg might spec peak power in the "sweet
>> spot" of the speaker. They might spec it at 1kHz for example. Even RMS
>> gets limited in many specs, to a small frequency band with specific
>> distortion specs. What I look for is the difference between peak*.707
>> and
>> RMS. Since 250w means u should be able to run 175RMS and the spec only
>> allows 100RMS I would figure it to be an "inexpensive" product or a
>> "hyped"
>> spec. In general, use the RMS numbers to determine general power between
>> speakers you are interested in.
>>
>> Another spec u will see is "program power" or "average power". For an AC
>> waveform, RMS is defined to be the average. So, if average is specified,
>> some specmanship is being applied. Program power is something I have
>> never
>> seen a definition of. It is suppoed to be RMS-like and kind of like
>> "average for your application" but who knows how each mfg interprets it.
>
> The above is a heap of unadulterated rubbish.
<snip>
prove it. you haven't a clue. Show the equation where u perform RMS
calculation and get .5peak. Just show it. Stop the drivel and prove your
point. Stop quoting marketing dudes and hifi magazines.
-Sax
> Graham
>
Saxology
unfortunately it agrees with me. They didn't get peak=2xrms. They came up
with the 1/sqrt2 which is .707 as I stated.
-Sax
Saxology
"Rodney" <wha...@comcast.net> wrote in message
news:1136507970....@o13g2000cwo.googlegroups.com...
thanks Rodney.
-Sax
>
Saxology
"Skeeter" <harpm...@sympatico.ca> wrote in message
<snip>
>
> Rather than fill up this post with math, please accept that the advice
> given be a few knowledgeable posters is correct when they tell you that
> RMS spec is half of the Peak Power spec.
> Cheers,
> Skeeter
well now skeeter, you just go right ahead and do that. It is wrong, but you
just run along your merry way. la la la la la la
personally, I use the facts. period. the paper presented in the thread
shows the correct information. Poo was wrong.
-Sax
Pooh Bear
Saxology wrote:
You are *talking out of your ARSE* Sax ! See this document posted by another
contributor to this thread for example......
http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definition
" So what about peak power? Peak power is a special case where Ppeak = Epeak *
Ipeak. For a sinewave, this is always twice the average power. "
I suppose you're going to say Meyer is wrong too ?
Stop spewing your ignorance in full view of those who know better.
If Phildo and George had any integrity they would hound you like Arny too.
Graham
Pooh Bear
Saxology wrote:
> All functions can be written as a sum of sines, therefore the .707 factor
> applies to all audio, period.
This is a classic example of " alittle knowledge is adangerous thing "
Sax doesn't understand that power is a 'square term' and that 0.707 squared is
0.5 so there's a *2:1* difference between peak and average ( so called rms )
power.
Graham
Pooh Bear
Saxology wrote:
> <snip>
> >
> > In the text books you clown.
>
> Name the book.
I assume that means you've never read one !
Any credible electrical or electronic text book will explain it. Take your
pick.
Graham
Pooh Bear
Saxology wrote:
> you haven't a clue. Show the equation where u perform RMS
> calculation and get .5peak.
I'm the pro-audio designer with 30+ yrs experience in the trade and you're just
spouting gibberish.
Graham
Pooh Bear
Saxology wrote:
> "Pooh Bear" <rabbitsfriend...@hotmail.com> wrote in message
> news:43BF00FC...@hotmail.com...
> >
> >
> > Rodney wrote:
> >
> >> bixby wrote:
> >> > I'm shopping for a powered speaker. Can someone please explain the
> >> > difference between RMS and Peak Power? For example, a speaker has 100
> >> > watts
> >> > RMS and 250 watts peak power. What does this mean? Are there any
> >> > other
> >> > important "terms" I should be aware of when shopping for a powered
> >> > speaker?
> >> > Thanks and sorry for the silly question.
> >>
> >> Have a look at the paper in the following link.
> >>
> >> http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definition'
> >
> > That's a decent read. Well presented.
> >
> > Graham
> >
>
> unfortunately it agrees with me.
It certainly doesn't. In any event agreeing with you would simply be wrong.
> They didn't get peak=2xrms. They came up
> with the 1/sqrt2 which is .707 as I stated.
> -Sax
Which part of
" So what about peak power? Peak power is a special case where Ppeak = Epeak * Ipeak. For a sine awave, this is
always twice the average power."
do you *NOT UNDERSTAND*. From the *link you just referred to* !
Graahm
Pooh Bear
Saxology wrote:
You can thank Rodney for illustrating I'm correct !
Graham
Pooh Bear
Saxology wrote:
> "Skeeter" <harpm...@sympatico.ca> wrote in message
> <snip>
> >
> > Rather than fill up this post with math, please accept that the advice
> > given be a few knowledgeable posters is correct when they tell you that
> > RMS spec is half of the Peak Power spec.
> <snip>
>
> > Cheers,
> > Skeeter
>
> well now skeeter, you just go right ahead and do that. It is wrong,
No it isn't !
> but you
> just run along your merry way. la la la la la la
>
> personally, I use the facts. period. the paper presented in the thread
> shows the correct information. Poo was wrong.
> -Sax
*You're* the one who's wrong. Maybe it hasn't managed to get inside your thick
skull yet.
Graham
Saxology
what poopoo doesnt know is that the squared term is inside the integral, not
outside. show your math fool. The paper presented shows the proper answer.
-sax
Saxology
nice try arni-gram, you have no proof. period.
-sax
Saxology
are you stupid? look at what u posted. you are really clueless.
-sax
Saxology
you are bose designer.... a hifi fool at best. learn to read. your 30 year
old skills have faded pro fool. you tangled with me once before and got
slapped, you are in for another. just go away and realize that you have
goofed. only a fool, like arni carries the stupidity further.
-Sax
Saxology
ok arni-gram, point out where they show rms=.5peak. point it out, go ahead
and try.
you are an idiot. I've know it for quite a while but you usually stay quiet
enough so it doesn't bother me. show your equations to prove peak=2rms. go
ahead. i call your bluff arni2.
-sax
Saxology
-sax
Saxology
i call you out again, shoe the equation to prove your point arni2. you
can't, you are wrong. either put up or shut up now arni-poopoo.
next thing you know you'll be sending lawyers like arni never did?
your just not amusing enough to reply to. post your equation, or go away
old man.
-Sax
Pooh Bear
Saxology wrote:
Just in case you missed the content of the thread it was about *power*.
The ratio of peak to average *power* for a sinewave is 2:1.
The ratio of peak to rms *voltage* or *current* for a sinewave is 1.4142..( sqrt
2 ) :1 ( or 0.707 for rms/peak if you prefer to express it that way )
In this thread it has been *power* that has been discussed.
Maybe you simply misunderstood what was being discussed ?
Graham
Peter Larsen
bixby wrote:
> I'm shopping for a powered speaker.
The thread has about a gazillion suggestions, so I will leave that to
those that know the products they suggest.
> Can someone please explain the difference between RMS
> and Peak Power?
Yes, the wording peak power is meaningless unless it comes with a
statement saying for how long and with what duty cycle. In the context
of an amplifier it is simply tne power the amp would produce at whatever
defined load until the supply voltage drops.
> For example, a speaker has 100 watts RMS and 250 watts
> peak power.
We have to take this as two cases, a multiway loudspeaker and the
loudspeaker units one by one.
> What does this mean?
It means that the manufacturer would not like you to use an amplifier
larger than 250 watts RMS on the loudspeaker if indeed a multiway and
used for GP music.
The usual asumption is then that the long term average will not exceed
25% of the amplifiers rated output, in other words that the peak to
average ratio is at least 6 dB, another wording you may encounter is
that the crest factor is 6 dB.
Some asumption about output power spectrum is also made when such a spec
is made, to know which: ask the manufacturer. Some power specification
standards as I vaguely recall this do come with a frequency
disttibuition asumption, but it may fit chamber music better than it
fits rock.
Loudspeaker units must be evaluated in the context of what is probable
in the frequency range they are designed for and in the context of their
thermal time constant, ie. how good their cooling is and for how long
they will retain heat.
Bass units tend to cool themselves by design, something that leads to
the interesting paradox that their powerhandling CAN be much better at
50 Hz than at 500 Hz. It is fairly easy to get cone midrange units
sturdy and able to tolerate very large peak powers, but they have less
cooling area than bass units, and long term powerhandling does depend
not only on how much heat the voice coil can tolerate, but also on the
cooling area and the ventilation of the gap.
Ferrofludics is an interesting way of improving the cooling of the voice
coil by (thermically) coupling it better to the magnet, but units in
high power use may need an annual oilchange job.
It starts getting really interesting to use ferrofludics in the context
of dome units, also remembering that most compression drivers contain an
inverted dome unit because they must have a small physical movable mass
and thus also have a small thermal mass of the movable parts.
Consequently the heat increase from occasional power bursts is much
larger than for a larger unit.
Read the spec very carefully if a small dome unit, including any small
compression driver, is spec'ed with a powerhandling that has 3 digits in
it. The wording "integrated programme" may assume that the unit is used
via a cross-over, in which case the actual RMS powerhandling may have a
digit less rigthmost than what is printed on the rear of the unit. Otoh,
as example, some manufacturers, for example Dynaudio, specify the
permitted duration of a 1 kWatt power impulse in the units usable
frequency band.
> Are there any other important "terms" I should be aware of
> when shopping for a powered speaker?
When you buy a powered speaker the two main specs are frequency range
with specified tolerance and max spl at 1 meter. Peak and RMS power are
not your concern, they are the manufacturers concern.
When you buy an unpowered speaker then efficiency is MORE important than
powerhandling, a 10 dB more efficient loudspeaker box with 6 dB less
powerhandling than the alternative will still be 4 dB louder.
Notice that max recommended amplifier can be as small as some fraction,
say 25%, of claimed RMS powerhandling in case of wide band instrument
loudspeakers in open back cabinets.
> Thanks and sorry for the silly question.
Not a silly question, a very good question to ask.
Having an amp that is big enough to never clip and some contraption that
with certainty prevents it from clipping is a good strategy. This too,
as the loudspeaker efficiency, is the problem of the designer when you
purchase a powered box, but asking what happens when it is overdriven is
a good idea, as is wearing ear protection (otherwise you will be unable
to hear even major distortion due to masking, the standard yellow EAR
plugs are good in terms of protective capability and possibly an
excellent choice for such quests) and actually listening to how the
stuff sounds overdriven.
Kind regards
Peter Larsen
--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
BobFli...@spamnomore.ca
wrote:
>
Right, I didn't realise it had a 'switch class' mode... clever idea.
>The SR3000 is only 2RU high & weighs 19kg - yet can equal the performance
>on LIVE MUSIC of a much bigger conventional amp. It is also low cost
>design with no fancy technology.
>
>Plus it uses lots of Motorola TO3 devices - no "flat earth" rubbish.
You mean those 'modules'! :)
Arny Krueger
news:2KJvf.6069$M%4.5...@newsread3.news.atl.earthlink.net
> All functions can be written as a sum of sines,
Agreed. All real-world audio signals can be analyzed and represented as a
sum of sine waves with harmonic frequencies. However, the phases of those
sine waves will vary depending on the signal being represented as a sum of
sines.
> therefore the .707 factor applies to all audio, period.
Wrong. When real world sine waves are summed they can have various phasing
depending on the signal. The peak amplitude of the sums of sine waves will
therefore vary significantly, depending on their phase.
For example, the amplitude of the sum of a tone and its third harmonic
varies by several dB depending on whether the third harmonic is in-phase
with the fundamental, or out-of-phase with the fundamental, or somewhere
in-between.
Since we generally can't control the phase of the sine waves that make up
the audio signals we encounter in live sound Saxology, your presumption
would lead to clipping that would surprise and mystify you.
Graham and I know what to expect from sums of sines and set our systems up
accordingly, thus avoiding any such surprises and mysteries.
Arny Krueger
news:corbett-0601...@0.0.0.0
> In article
> <NsKdnU7YFqL_RSPe...@comcast.com>, "Arny
> Krueger" <ar...@hotpop.com> wrote:
>
>> "John Corbett" <cor...@stat.umn.edu> wrote in message
>> news:corbett-0601...@0.0.0.0
>>> In article
>>> <LYqdnfI5VtO5gCDe...@comcast.com>, "Arny
>>> Krueger" <ar...@hotpop.com> wrote:
>>>
>>>
>>>> 0.707 times peak is the average value of a sine wave.
>>>> Think of chopping off the peaks to fill in the valleys.
>>>> So, a sine wave with a peak value of 10 volts has an
>>>> average value of 7.07 volts.
>>
>>> Arny seems to have confused average and rms values.
>>
>> I think that would be exactly right, my answer above was
>> based on some erroneous and incomplete memories.
>>
>>> Over a complete cycle, the _average_ value of a sine
>>> wave is zero.
>>
>> That would be a very ludicrous and pedantic solution to
>> the problem.
>
> Not at all. As I wrote elsewhere in this thread in reply
> to Pooh Bear, the fact that the average value of a sine
> wave is zero is an integral (!) part of how we compute
> average power for both reactive and resistive loads.
>
> Also, remember that the average of almost any waveform is
> its DC component; this works precisely because all the
> sinusoidal components have zero average over whole cycles.
>
> It is far from a ludicrous and pedantic observation.
>
>>
>>> The average of the _absolute value_ of a sine wave,
>>> i.e., a rectified sine wave, is (2/pi) times the peak
>>> amplitide. That is about .637 times peak, and is what
>>> you would get by "chopping off the peaks to fill in the
>>> valleys" for just the positive half-cycle of the
>>> original sine wave.
>>
>> As compared to the previous ludicrous and pedantic
>> answer, this would be a proper and relevant solution to
>> the problem.
>
> The only ludicrous answer is yours; of course any correct
> answer will appear proper and relevant compared to what
> you had written.
>
>>
>> As a check I made a spread sheet of the values of a sine
>> wave and as I increased the number of points I watched
>> the result become asymptotic to the value given above.
>> This confirmed the number I worked out using the
>> integration I learned in first semester calculus some
>> 40-odd years ago.
>
> Now _that_ is ludicrous---spreadsheet asymptotics!
>
>>
>>> The _rms_ value (sometimes called effective value) of a
>>> sine wave is (1/sqrt(2)) times peak, or about .707 times
>>> peak, but you won't get that by "chopping off
>>> the peaks to fill in the valleys" of the original sine
>>> wave.
>>
>> Agreed, my answer about average values was an error.
>>
>> My confusion came from the fact that most common
>> (non-true-RMS) voltmeters actually measure the average
>> value of the signal, but are calibrated to present the
>> equvalent RMS value, presuming the signal is a sine
>> wave. This works for measuring sine waves, but it does
>> not give a reasonable result for more complex waves,
>> which includes a lot of audio applications.
>
> Almost correct---remember that the so-called
> average-responding meter is averaging after rectifying.
> Then it presents about 1.11 times that average (absolute)
> value as the RMS value.
Just goes to show John that you don't know how the use of the words "are
calibrated" above included that effect. I'll bet you've never calibrated a
meter by hand.
Arny Krueger
http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definitionMotherhood and applie pie. I wonder if Corbett could come up with somepedantic exception to it.>> " So what about peak power? Peak power is a special case>> where Ppeak = Epeak *>> Ipeak. For a sinewave, this is always twice the average>> power. ">> I suppose you're going to say Meyer is wrong too ?In essence, that's what Saxy is doing below.>> Stop spewing your ignorance in full view of those who>> know better.> are you stupid? look at what u posted. you are really> clueless. -saxThis sort of deinal of the obvious, name-calling and posturing in the faceof an obviouis evience is known on Usenet as "Pulling a Phildo" or "Pullinga Gleason".
Arny Krueger
news:428hk0F...@individual.net
> "Pooh Bear"
>> Rodney wrote:
>>>
>>> http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definition'
>>
>> That's a decent read. Well presented.
>>
>
>
> assertions and half truths.
Post them, Phil.
Phil Allison
"Arny Krueger"
>>
>>>> http://www.meyersound.com/support/papers/Power_Ratings_Tech_Note.pdf#search='rms%20peak%20power%20definition'
>>>
>>> That's a decent read. Well presented.
>>>
>>
>> ** It is full of dumb technical errors, false
>> assertions and half truths.
>
> Post them, Phil.
** Posting " dumb errors, false assertions and half truths " is something
I leave to others.
Like you and Poopie.
......... Phil
bixby
info. That was a long post, appreciate your time. It's a learning
experience for me.. so it'ss probabably take me a few more reads to fully
absorb your post :) But it's here along with the rese for the usenet record.
I notice there are some people in this ng kind of going at at each other --
knowledge/competitive wise. Whoever is right or wrong, you all still have a
strong knowledge of audio and acoustics and I feel like I've walked into a
university class! All the talk and mumbo jumbo mathematecal equations are
pretty impressive, even if you don't understand it right away.
Cheers.
--
"Peter Larsen" <SPAMSHIEL...@mail.tele.dk> wrote in message
news:43C02267...@mail.tele.dk...
Peter Larsen
> Hi there Peter. Wow, this thread really balooned.
Yes.
> Thanks alot for all the info. That was a long post,
> appreciate your time.
[bowing] Thanks, I felt it relevant to post something more to the point
of what you asked about .... O;-)
> It's a learning experience for me.
We are all newbies at something. Notice how I write this - rather terse
- followup. I use netscape 4.7 as newsreader because it makes it ease to
write like that. Microsofts products are aimed more at the corporate
market, where it is often relevant to just write an email reply at the
top and leave the lot dangling below. Add a third party expansion pack
called OE Quotefix to your Outlook Expresss and it will instantly become
a much more usable newsreader.
> so it'ss probabably take me a few more reads to fully absorb your post :)
That is expected.
> But it's here along with the rese for the usenet record.
Hmm ... yes.
> I notice there are some people in this ng kind of going at
> at each other -- knowledge/competitive wise.
It is process called "peer review" .... O;-) .... remember that this is
by definition a loud newsgroup O;-)
> Whoever is right or wrong, you all still have a
> strong knowledge of audio and acoustics and I feel
> like I've walked into a university class!
That is the nicest thing that has been said about this newsgroup for
very long time, thank you. It is to some extent an after hours bar where
people come directly from a very noisy environment and thus speak very
loudly. Supplement with alt.sci.physics.acoustics, occasionally
something interesting happens here, and with rec.audio.tech - for the
very same reason.
> All the talk and mumbo jumbo mathematecal equations are
> pretty impressive, even if you don't understand it right away.
It was most certainly a question that spawned all kinds of detailed
information.
> Cheers.
Peter Larsen
> Have a look at the paper in the following link.
Thanks Rodney, nice to hear from you.
> Rodney
Saxology
poo, given a new year, and after reading my last posts, i take back the
bose crack, the arni crack, and the other name calling stuff. I don't want
to be an aapls name caller... too easy to do and adds nothing to the thread.
I am going to reform my methods.
I was talking voltage and current, or, the constant current with varying
voltage model. Well, i obviously didnt get my point accross very well.
Small fever the last few days didnt help. Regardless, I take back all of
the nasty crack stuff. Happy new year!
-Sax
Pooh Bear
Saxology wrote:
Ok, that figures ! I thought there must be a simple misunderstanding.
> or, the constant current with varying
> voltage model. Well, i obviously didnt get my point accross very well.
> Small fever the last few days didnt help.
I'll bet.
> Regardless, I take back all of
> the nasty crack stuff. Happy new year!
Cheers !
A Happy New Year to you too.
Graham
Greg Cameron
Phil Allison wrote:
> ** There are any number of amplifiers, both domestic and pro audio types,
> that are designed to deliver short bursts of power well above the continuous
> rms value for significant periods of time. This enables them to reproduce
> typical music signals without clipping distortion at the same output levels
> as amplifiers of *much higher * continuous power rating.
Hi Phil. Any experience with output capabilities of the older Crest Pro
series amps? I've always been surprised that one Crest 7001 is able to
power 4 of my double 18" boxes loaded with either EVX-180B's or TAD
1801 drivers to maximum output, when the amp's rated output on paper
would be anemic for the power rating of those drivers. The spec on that
amp says it will put out 1700 watts bridged into a 4 ohm load @ 1kHz
(.02%THD+N) or 1600 watts 20-20KHz (.05%THD+N). I realize when pushed
into mild clipping that the power is greater. But 8 of those 18"
drivers has a total rms rating of 4800 watts (600 watts rms per
driver). Now I also understand that running said drivers at their
lowest frequency capability will reduce their power handling
capability. Interestingly, other amps of similar power spec to the
Crest 7001 will not do the same job. The only conclusion I can come up
with is that the Crest must be doing something that other amps can't
unless you use models that have power ratings closer matched to the rms
or 2x rms rating of the drivers. Before I was using the single Crest
for up to 4 boxes, I was using Mackie M2600 amps, and I had to use one
amp per box bridged to accomplish the same output. It's just such a
discrepancy. I was also informed that other amps of similar output spec
of the Crest by manufacturers such as QSC, and even the newer Crest Pro
series (x002) didn't have the same punch.
This same 4 box setup had been tested with the Crest 8001 by the box
designer, but it was capable of over-driving them before hitting clip.
And it's not a huge jump in output (2800 vs. 1700) when talking about
that particular compliment of drivers and their rms rating.
> In the case of a powered speaker system, the makers ought to supply a
> maximum SPL figure in dBs that the box can produce cleanly.
>
> But while ever the market is remains obsessed with electrical watts instead
> of actual, usable sound that will never happen.
I could not agree more. I'd much rather have a box that can put out 130
dB at 500 watts of input then one that puts out 126dB at 1000 watts. It
would also be wonderful if the specs indicated what the actual measured
max SPL was instead of using calculations, AND gave actual outputs at
several frequency points starting with the lowest usable frequency. In
my book, that would be the 3dB down point.
Greg
Rodney
enlighten him. I'm sure he will be greatful to you, a world class
technical expert, for correcting his errors.
Rodney
bixby
this thread. Wow, lots of terrific information. I appreciate all the time
you guys took in replying, and sorry if I didn't respond personally to any
of the posts but I did read every one of them.
Phil Allison
"Rodney"
** Must be a long time fan of Hermann Goering .
His famous brag re the incompetence of the RAF...
" .... you can call me Meyer .... "
>I encourage you to contact John, his last name is Meyer, directly and
> enlighten him.
** Mr John Meyer can come right here to be " enlightened "
* free of charge* any time he damn well pleases.
That would be high entertainment indeed.
> I'm sure he will be greatful to you,
** I very much doubt that JM would enjoy having his very many short comings
revealed to the world.
Calling his flawed and misguided *press release* by the grandiose title
"Tech Note" is just for starters.
> a world class technical expert,
** Something he is not and you are not.
Do a Google search.
The posturing, bearded dude is utterly unqualified in audio electronics.
....... Phil
Phil Allison
"bixby"
** Ever thought of going into politics
I reckon YOU are a natural.
....... Phil
Bob Urz
Phil Allison wrote:
> "Rodney"
>
> ** Must be a long time fan of Hermann Goering .
>
> His famous brag re the incompetence of the RAF...
>
> " .... you can call me Meyer .... "
>
>
>
If that's the case, maybe Phil should called "Oscar meyer".........
>
>
>>I encourage you to contact John, his last name is Meyer, directly and
>>enlighten him.
>
>
>
> ** Mr John Meyer can come right here to be " enlightened "
>
> * free of charge* any time he damn well pleases.
>
> That would be high entertainment indeed.
>
>
You got one point Phil. Your both internationally known......
>
>
>>I'm sure he will be greatful to you,
>
>
>
> ** I very much doubt that JM would enjoy having his very many short comings
> revealed to the world.
>
> Calling his flawed and misguided *press release* by the grandiose title
> "Tech Note" is just for starters.
>
>
>
>>a world class technical expert,
>
>
>
> ** Something he is not and you are not.
>
> Do a Google search.
>
> The posturing, bearded dude is utterly unqualified in audio electronics.
>
Lets see, Meyer sound. Internationally know with products all over the
world.
Phil Allison, over 1 million satisfied repaired toaster customers.....
Tough choice.........
Have a gday Phil!
Bob
>
>
>
> ....... Phil
>
>
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----