How to test speaker ohms?
muzician21
"Studio Standard Series". No idea what vintage it is - maybe 80's or
90's.
What's on the back is
SB-80521-1
L81TNK
AFAIK it's a factory speaker. Obviously I want to replace it with the
right kind of speaker. I have a multimeter, how do I test it? Only one
is damaged - it's been torn since I got them at a pawn shop - but do
you think I should replace both sides or is it not likely to make an
appreciable difference?
For sizing purposes, is the speaker size generally considered to be
across the speaker frame - about 4 3/4 " or the exposed portion of
the cone inside the speaker frame - right about 4"?
Thanks
Kalman Rubinson
Well, you can measure the "ohms" in several ways but that is quite
inadequate for selecting a suitable replacement.
Kal
Scott Dorsey
>I want to replace the midrange of a Fisher speaker model ST-440
>"Studio Standard Series". No idea what vintage it is - maybe 80's or
>90's.
I think you want to toss it.
>what's on the back is
>
>SB-80521-1
>
>L81TNK
>
>AFAIK it's a factory speaker. Obviously I want to replace it with the
>right kind of speaker. I have a multimeter, how do I test it? Only one
>is damaged - it's been torn since I got them at a pawn shop - but do
>you think I should replace both sides or is it not likely to make an
>appreciable difference?
The impedance of the speaker is only one of about a dozen parameters
that you need to measure for the driver. Vance Dickason's Loudspeaker
Cookbook has a whole chapter on measuring T-S parameters of an unknown
driver.
>For sizing purposes, is the speaker size generally considered to be
>across the speaker frame - about 4 3/4 " or the exposed portion of
>the cone inside the speaker frame - right about 4"?
Sadly most folks are measuring inside the frame, and including the
surround in the cone size.
Really, though... if this is what I think this is, it's a junk speaker
and not worth the labour to haul it to the dumpster.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Paul
You cannot test the AC ohms of a speaker with an multimeter,
because the multimeter only measures DC ohms resistance.
Phil Allison
"Paul"
> You cannot test the AC ohms of a speaker with an multimeter,
** Yes you can.
> because the multimeter only measures DC ohms resistance.
** That is all you need - then allow 15-20% extra on that number for the
nominal ( usually also the minimum ) AC impedance value.
The DC ohms plus 15-20 % rule applies to any cone loudspeaker ( drivers
only, not systems) - it accounts for the additional resistive losses in
the magnet structure and suspension parts when that speaker is driven with
AC at the frequency of its impedance minima.
..... Phil
WillStG
Well being what they are, they sell for like $25 - $40 a pair
used. So... for cheap and since you already paid for them, you can
try fixing the tear using the paper unwrapped from a couple of teabags
and some rubber cement. After it dries you can color it a bit with
magic marker,
Or just call Fisher Sanyo and ask them
http://sanyoservice.com/partdistributors.htm
Reconing isn't so very hard for DIY, but being what they are you
could just buy another pair on Craigslist for parts - and it would be
better to buy something else, especially for working on music. Modern
speakers are much, much better and 30 year old speakers have to be
dogmeat by now.
Will Miho
NY TV/Audio Post/Music/Live Sound Guy
"The large print giveth and the small print taketh away... Tom Waits
Eeyore
Phil Allison wrote:
Many nominal 8 ohm speakers I've seen measure as low as ~ 5 ohms at DC.
Largely SR/PA types though.
Graham
Eeyore
WillStG wrote:
Excepting Quad electrostatics !
Graham
Phil Allison
"Eeysore
** Those speakers are 6 ohms AC impedance, as sine wave tests conducted at
250 - 400 Hz demonstrate.
The "nominal 8 ohms " value quoted by the makers is NOT derived by
electrical test, but is a *marketing tactic*.
EV started this nonsense in the 1980s, in order to squeeze out a couple of
dB extra sensitivity and so out-spec comparable JBL products - in the eyes
of dim witted customers.
Hi-fi speaker brands often do the same and justify it as "compensation " for
resistive losses in typical passive x-overs.
..... Phil
WillStG
wrote:
If you can find me some for $25 I'll take them - and recone 'em
myself! <g> A little saran wrap, ....
William Sommerwerck
> ** Yes you can.
>> because the multimeter only measures DC ohms resistance.
> ** That is all you need - then allow 15-20% extra on that number
> for the nominal ( usually also the minimum ) AC impedance value.
That's a calculated estimate, not a measurement. There is a difference.
George's Pro Sound Company
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:grnbhc$mmv$1...@news.motzarella.org...
it involves passing aknown level signal and a known resistence measureing
the voltage diffrnece between when the known resistence is in line and not
way tomuch bother for me
I use a device I bought fromParts Express the WT3 speaker tester
george
Mike Rivers
> I want to replace the midrange of a Fisher speaker model ST-440
> "Studio Standard Series". No idea what vintage it is - maybe 80's or
> 90's.
> AFAIK it's a factory speaker. Obviously I want to replace it with the
> right kind of speaker. I have a multimeter, how do I test it? Only one
> is damaged - it's been torn since I got them at a pawn shop - but do
> you think I should replace both sides or is it not likely to make an
> appreciable difference?
Chances are it's 8 ohms, but if you measure the DC resistance and
double it, you'll be in the right ballpark. You can make it FUNCTIONAL
by replacing it with a speaker that's about the right impedance and fits
in the hole, but it will never sound like the original (which might be a
good thing). But if you do this, buy two and replace the speaker in
both of the boxes so at least they'll match.
There are many things other than impedance to consider, and those
speakers are probably not worth trying to optimize. They wren't that
good to begin with. If you want to salvage anything from your purchase
you might consider getting a book on speaker building and use the boxes
to house a proper set of drivers. Or sell them on eBay and buy some
decent speakers. ("Has slight tear in one cone but I'm sure it can be
repaired easily")
--
If you e-mail me and it bounces, use your secret decoder ring and reach
me here:
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
(mriv...@d-and-d.com)
Phil Allison
"William Sommerwanker"
>Paul
>>Phil Allison
** Paul used the words: " test the AC ohms of a speaker " - but he was
totally clueless.
The OP ( even more clueless than Paul) simply wanted to identify the
impedance of a small speaker for replacement purposes suing a multimeter.
Now, the actual impedance of any cone speaker can only be shown by a graph
or series of graphs, since it is not a single number and depends on many
variables - none of which matter a HOOT when all you want to know is the
impedance rating for replacement purposes.
Then, some ASD fucked CUNT called Sommerwanker butts his POINTY
anencephalic head in and a spews a pile of vile PEDANTRY all over the
place.
Go drop dead - Wanker !!!
...... Phil
Laurence Payne
<muzic...@yahoo.com> wrote:
Take out the bad unit and show it to a shop that sells replacement
drivers. Buy a couple of whatever they recommend. They won't be very
expensive. Install them. If they sound good, fine. If not, buy some
more speakers. Yours are worth spending a little time and money on,
but only a little.
Scott Dorsey
>
>You cannot test the AC ohms of a speaker with an multimeter,
>because the multimeter only measures DC ohms resistance.
No, although you CAN measure the DC resistance and do some handwaving and
say the impedance at 1 KHz is probably more or less about 1.5 times the
DC resistance. This is usually enough to get you into the ballpark if you
know the speaker is rated for a common impedance.
But, sadly, the impedance is only one of a whole lot of things the original
poster needs to know to replace the driver.
Scott Dorsey
>
>Many nominal 8 ohm speakers I've seen measure as low as ~ 5 ohms at DC.
>Largely SR/PA types though.
That's still more or less within range, if you know it's a standard
load. If you see 5 ohms DC, you know it cannot possibly be a 4 ohm
speaker, and it almost certainly isn't a 16 ohm speaker, so it's probably
an 8 ohm speaker.
GregS
There are speakers that have that 6 ohm nominal Z. Common in todays
consumer market.
Z is probably the least important spec the guy will need.
Efficiency and resonance, and physical size are more
important. I was loking for some cheap looking units of about 8 ohms.
Here Loook..
http://www.mcmelectronics.com/browse/Midrange/3829617
GregS
Whenever I replace something its usually to BOTH sides if not
an identical replacement. Even that, it needs checked for
uniformity.
greg
George's Pro Sound Company
"GregS" <zekf...@zekfrivolous.com> wrote in message
news:grnnkr$6d3$2...@usenet01.srv.cis.pitt.edu...
except when you put a 4 ohm loudspeaker on a passive crossover designed for
a 8 ohm box it doubles the value of the crossover point
so if it was crossing over at 1800 with a 8 ohm speaker it will now be
crossing over ar 3600
with a 4 ohm load
george
Anahata
> when you put a 4 ohm loudspeaker on a passive crossover designed
> for a 8 ohm box it doubles the value of the crossover point so if it was
> crossing over at 1800 with a 8 ohm speaker it will now be crossing over
> ar 3600
> with a 4 ohm load
> george
It depends on the crossover network, but even a simple 2nd order LC
network has a nominal crossover point independent of load (The frequency
where the impedance magnitudes of L and C are the same). The drive unit
impedance will have an effect but it will be second order.
The fact remains that using a 4 ohm unit where an 8 ohm one is expected
still won't work very well: the balance between them won't be right, and
the impedance/frequency curve of the whole box will be even more wonky
than usual.
--
Anahata
ana...@treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
GregS
>On Fri, 10 Apr 2009 12:01:51 -0400, George's Pro Sound Company wrote:
>
>> when you put a 4 ohm loudspeaker on a passive crossover designed
>> for a 8 ohm box it doubles the value of the crossover point so if it was
>> crossing over at 1800 with a 8 ohm speaker it will now be crossing over
>> ar 3600
>> with a 4 ohm load
>> george
>
>It depends on the crossover network, but even a simple 2nd order LC
>network has a nominal crossover point independent of load (The frequency
>where the impedance magnitudes of L and C are the same). The drive unit
>impedance will have an effect but it will be second order.
>
>The fact remains that using a 4 ohm unit where an 8 ohm one is expected
>still won't work very well: the balance between them won't be right, and
>the impedance/frequency curve of the whole box will be even more wonky
>than usual.
>
Well it probably will not work well, but the nominal Z is not important.
You have to know the exact graph of Z to know what the Z is at for
some desired crossover. The order of the crossover is also very important
to driver damping. You can get some really bad plots from some crossover
using another driver with different stories. Unless you get real lucky,
replacing it will cause some kind of grief. Its highly unlikely that the
level matching will be on or the phase will be slightly off. Many speakers will have
level controls, and sometimes that will be enough to compensate, but level controls
often also change the plot.With the name of the manufacturer in mind, the
crossover probably does not have any impedance compensation or
response compensation. Everything is built into the drivers and simple
crossover. Remember the driver can also cause an added pole depending on
the phase shift.
greg
Rich Grise
If it's really just a tear, and not a hole, you can repair the cone with a
little fingernail polish and toilet paper.
Good Luck!
Rich
GregS
It was not clear if the speaker made sound, or if it really made any
noticable difference in output in the first place. I assumed it
didn't work at all. Its not really necessary to mend the pieces together.
Often a dab of rtv will be all thats needed.
greg
Paul
As the other poster said, your method is a very rough
guestimate.
My point, Dumbshit, was that the impedance of a speaker is
measured with
AC, not DC.
Phil Allison
"Paul the Puke "
>
> > You cannot test the AC ohms of a speaker with an multimeter,
>
> ** Yes you can.
>
> > because the multimeter only measures DC ohms resistance.
>
> ** That is all you need - then allow 15-20% extra on that number for the
> nominal ( usually also the minimum ) AC impedance value.
>
> The DC ohms plus 15-20 % rule applies to any cone loudspeaker ( drivers
> only, not systems) - it accounts for the additional resistive losses in
> the magnet structure and suspension parts when that speaker is driven with
> AC at the frequency of its impedance minima.
As the other poster said, your method is a very rough
guestimate.
** No one here said that - you lying, fucking puke !!
The method is very accurate.
> My point,
** You had no point - you stupid cunthead.
Dumbshit, was that the impedance of a speaker is
measured with AC, not DC.
** Irrelevant to the Q being asked - fuckwit.
Folk have been using multimeters to test speaker impedances ever since they
both existed.
ASD fucked shit brains like YOU are not about the stop them.
So Fuck Off and Die.
..... Phil
Phil Allison
"Anahata"
>
> It depends on the crossover network, but even a simple 2nd order LC
> network has a nominal crossover point independent of load (The frequency
> where the impedance magnitudes of L and C are the same).
** The term " nominal crossover point" = meaningless drivel !!
Cos the word "nominal" means " in name only ".
In *reality*, a 2:1 impedance mismatch with a x-over filter has DRAMATIC
effect on its performance and the load impedance seen by the driving
amplifier in the region of the crossover frequency.
> The drive unit impedance will have an effect but it will be second order.
** That is utter BOLLOCKS.
Eg An under loaded LC x-over filter turns into a series tuned circuit -
it then has a VERY low input impedance at the resonant frequency and
MULTIPLIES any input signal by many times creating a huge peak in the
response around that frequency. Very bad news.
..... Phil
Eeyore
Phil Allison wrote:
> "Eeysore
> Phil Allison wrote:
> > "Paul"
> >>
> >> > You cannot test the AC ohms of a speaker with an multimeter,
> >>
> >> ** Yes you can.
> >>
> >> > because the multimeter only measures DC ohms resistance.
> >>
> >> ** That is all you need - then allow 15-20% extra on that number for the
> >> nominal ( usually also the minimum ) AC impedance value.
> >>
> >> The DC ohms plus 15-20 % rule applies to any cone loudspeaker ( drivers
> >> only, not systems) - it accounts for the additional resistive losses in
> >> the magnet structure and suspension parts when that speaker is driven
> >> with
> >> AC at the frequency of its impedance minima.
> >
> > Many nominal 8 ohm speakers I've seen measure as low as ~ 5 ohms at DC.
> > Largely SR/PA types though.
>
> ** Those speakers are 6 ohms AC impedance, as sine wave tests conducted at
> 250 - 400 Hz demonstrate.
It's ages since I ran a plot, so it's a bugger to remember. Note that the
cabinet will influence actual AC Z too.
> The "nominal 8 ohms " value quoted by the makers is NOT derived by
> electrical test, but is a *marketing tactic*.
>
> EV started this nonsense in the 1980s, in order to squeeze out a couple of
> dB extra sensitivity and so out-spec comparable JBL products - in the eyes
> of dim witted customers.
>
> Hi-fi speaker brands often do the same and justify it as "compensation " for
> resistive losses in typical passive x-overs.
And now you get home hi-fi and especially 5.1 systems where the speakers are
actually rated at 6 ohms nominal to extract that extra dB or so.
Graham
Eeyore
George's Pro Sound Company wrote:
> "GregS" <zekf...@zekfrivolous.com> wrote in message
Only with a first order crossover. As the fliter order increases, the
difference will be less, but the filter damping suffers, so the response will
still be affected.
Not to mention a GOOD crossover compensates for the T-S characteristics of the
driver ( especially voice coil inductance ).
Graham
Eeyore
GregS wrote:
> Anahata <ana...@treewind.co.uk> wrote:
> >On Fri, 10 Apr 2009 12:01:51 -0400, George's Pro Sound Company wrote:
> >
> >> when you put a 4 ohm loudspeaker on a passive crossover designed
> >> for a 8 ohm box it doubles the value of the crossover point so if it was
> >> crossing over at 1800 with a 8 ohm speaker it will now be crossing over
> >> ar 3600 with a 4 ohm load
> >
> >It depends on the crossover network, but even a simple 2nd order LC
> >network has a nominal crossover point independent of load (The frequency
> >where the impedance magnitudes of L and C are the same). The drive unit
> >impedance will have an effect but it will be second order.
> >
> >The fact remains that using a 4 ohm unit where an 8 ohm one is expected
> >still won't work very well: the balance between them won't be right, and
> >the impedance/frequency curve of the whole box will be even more wonky
> >than usual.
>
> Well it probably will not work well, but the nominal Z is not important.
> You have to know the exact graph of Z to know what the Z is at for
> some desired crossover. The order of the crossover is also very important
> to driver damping. You can get some really bad plots from some crossover
> using another driver with different stories. Unless you get real lucky,
> replacing it will cause some kind of grief. Its highly unlikely that the
> level matching will be on or the phase will be slightly off. Many speakers will have
> level controls, and sometimes that will be enough to compensate, but level controls
> often also change the plot.With the name of the manufacturer in mind, the
> crossover probably does not have any impedance compensation or
> response compensation. Everything is built into the drivers and simple
> crossover. Remember the driver can also cause an added pole depending on
> the phase shift.
All the more reason to use active crossovers and bi / tri amping.
Graham
Eeyore
Paul wrote:
> "Phil Allison" <philalli...@tpg.com.au> wrote:
> > "Paul"
> >
> > > You cannot test the AC ohms of a speaker with an multimeter,
> >
> > ** Yes you can.
> >
> > > because the multimeter only measures DC ohms resistance.
> >
> > ** That is all you need - then allow 15-20% extra on that number for the
> > nominal ( usually also the minimum ) AC impedance value.
> >
> > The DC ohms plus 15-20 % rule applies to any cone loudspeaker ( drivers
> > only, not systems) - it accounts for the additional resistive losses in
> > the magnet structure and suspension parts when that speaker is driven with
> > AC at the frequency of its impedance minima.
>
> As the other poster said, your method is a very rough
> guestimate.
>
> My point, Dumbshit, was that the impedance of a speaker is
> measured with AC, not DC.
I once did a sweep of a driver without thinking, cone downwards on the bench.
Turning it cone up made a visible difference to the plot. This is because the
speaker is doing mechanical work.
Graham
Eeyore
Rich Grise wrote:
I tend to use PVA as the glue. More flexible.
Graham
Paul
The stupider people are, the angrier they get!!
I can see the smoke from here!
BWAHAHA!
Phil Allison
"Eeysore"
>
> I once did a sweep of a driver without thinking, cone downwards on the
> bench.
> Turning it cone up made a visible difference to the plot. This is because
> the
> speaker is doing mechanical work.
** Face down, the speaker was being loaded by a ( more or less) sealed
enclosure of LESS than 1 litre volume.
No wonder the impedance curve was NOT the same as for "free-air" !!!
The correct procedure for finding the Fs of a driver involves dangling it
from the roof on a string.
..... Phil
Phil Allison
"Paul the Retarded PUKE "
** No one here said that - you lying, fucking puke !!
** You had no point - you stupid cunthead.
** Irrelevant to the Q being asked - fuckwit.
Folk have been using multimeters to test speaker impedances ever since they
both existed.
And no ASD fucked shit for brains PUKE like YOU is about the stop them.
Paul
+BWAHAHAHA!
William Sommerwerck
> impedances ever since they both existed.
You cannot properly measure impedance with a DC device.
George's Pro Sound Company
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:grpvt7$9ll$1...@news.motzarella.org...
>> Folk have been using multimeters to test speaker
>> impedances ever since they both existed.
>
> You cannot properly measure impedance with a DC device.
>
here is how to use a VOM to measure impedance of a unknown but working
speaker, it does involve injection of signal
http://zekfrivolous.com/sub/usenet/pierce/impedometer.html
george
William Sommerwerck
> >> impedances ever since they both existed.
>> You cannot properly measure impedance with a DC device.
> VOM read both ac and dc
> here is how to use a VOM to measure impedance of a unknown
> but working speaker, it does involve injection of signal
> http://zekfrivolous.com/sub/usenet/pierce/impedometer.html
A multimeter (see above) does not provide that signal.
George's Pro Sound Company
the multimeter is doing the measurments.
I am simply showing that a VOM is a useful tool that can be used to measure
impedance
you do not need a fancy occiliscope/signal gen rig a amp passing noise
such as between radio stations is sufficent
I use the Part Express /Dayton WT3 for my impedance measuments but years of
in feild service to commercialsound system required that i understand how to
get the most out of a VOM
link to the WT3
http://www.daytonaudio.com/wt3.html
>
>
Phil Allison
"William Sommerwanker CUNT HEAD "
> Folk have been using multimeters to test speaker
> impedances ever since they both existed.
> You cannot properly measure impedance with a DC device.
** You made that same fucking asinine remark already.
CUNT HEAD !!
.... Phil
Phil Allison
"William Sommerwanker CUNT HEAD "
> Folk have been using multimeters to test speaker
> impedances ever since they both existed.
> You cannot properly measure impedance with a DC device.
William Sommerwerck
only at a distance) with people who, at the very least, need someone to talk
to.
"Phil" (that's a Hitchhiker joke), do you think I'm actually bothered by
your remarks?
George's Pro Sound Company
I don't know anyone besides you that hasn't killfiled the aussie scumbag
george
>
>
Richard Crowley
>I want to replace the midrange of a Fisher speaker model ST-440
> "Studio Standard Series". No idea what vintage it is - maybe 80's or
> 90's.
> What's on the back is SB-80521-1 L81TNK
>
> AFAIK it's a factory speaker.
You are almost certainly correct. They tended to use OEM custom
drivers for mass-market consumer goods back in the day (just as is
the custom today).
> Obviously I want to replace it with the right kind of speaker.
You have not stated any motivation for this. In the likely opinion of
most people here, you have a speaker that is not worth any effort
to repair.
As others have observed you cannot measure AC impedance with
a device that measures DC resistance. And AC impedance is only
a small part of the picture. Your chances of finding an exact replacement
depend on finding another set of speakers and cannibalizing the driver.
Else you have no practical way of finding an exact (or even close)
replacement. Fortunately, the speakers likely aren't worth the effort
anyway.
Phil Allison
"Richard Crowley = yet another PITA wanker "
>
> You have not stated any motivation for this. In the likely opinion of
> most people here, you have a speaker that is not worth any effort
> to repair.
>
> As others have observed you cannot measure AC impedance with
> a device that measures DC resistance.
** Shame how you and the other two fuckwit, autistic pedants are 100% wrong
in the case of cone loudspeakers.
Nobody needs your posturing BULLSHIT shoved down their throats either.
And nobody give a flying fuck what idiots like you think.
So piss off.
...... Phil