Marshall 4 or 8 ohms? question.
James Salazar
I have a Marshall JCM 800 that I run through a Carvin 4x12 cab. I have the
marshall dialed in at 8 ohms bu the Carvin cab says it's wired at 4ohms.
When I switch the Marshall to 4ohms to match the cabs requirements it
changes the tone dramatically and basically sounds like shit and ruins my
tone.
My question is, Will this hurt the amp?
Jim
Chris Terry
If you have a Marshall HEAD, the speaker switch is for 8 or 16 ohms,
so you are kind of screwing up either way with a 4 ohm cab. Rewire
the cab for higher impedance if possible. Like 16. 2 pair of 16 ohm
speakers in parallel, then wire the 2 pairs in series. Right now I
suspect you have 4 16 ohm speakers all in parallel for a 4 ohm total.
You have succomb to the misleading label on the impedance selector
switch, which is 8 or 4 (16) , I think.
On a head it means 16 and on a combo it means 4.
I don't own a JCM 800, so I could be wrong.
That would explain the worse sound when you switch from 8 to 16.
Chris
Skip May
: James Salazar (ter...@qnet.com) wrote:
: I have a Marshall JCM 800 that I run through a Carvin 4x12 cab. I have the
: marshall dialed in at 8 ohms bu the Carvin cab says it's wired at 4ohms.
: When I switch the Marshall to 4ohms to match the cabs requirements it
: changes the tone dramatically and basically sounds like shit and ruins my
: tone.
: My question is, Will this hurt the amp?
: Jim
:
Hi Jim,
While looking through my latest Carvin Catalog last night, I did notice
that Carvin mentions their 4-12 cab is a 4 and 8 ohm box. Vs the Marshall
4-12 box (1960a) I have (a few) here which offer a 4-16 ohm connections in
the mono mode. Both cabs also offer up stereo configs, but that's not
worth going into here.
The end result is that Carvin vs Marshall prob use different combinations
of speaker impedance in series/parallel to get their respective values.
The straight answer to your question is yes. There is potential to hurt
your amp with mis-matched output combination. The flame wars soon to
follow... The bottom line of all this is heat. Any mis-match in the
power transfer from the amp to the speaker(s) ends up as wasted heat,
often back in the power amplifier. Heat is a killer of parts and would
love to dance with your expensive output transformer. So it's best to run
the output transformer tap set to match the cab, or the converse.
All the previously mentioned rules apply. You'll get the max power
transfer when the box's match impedance.
I've seen three or four past posts where the owners of Marshall amp/heads
mention their respective avail outputs as 4&8 or 8&16. This seems weird
as most all my marshall heads offer up 4,8 and 16 ohm outputs. Only one
model I have (3203) has the limited dual selection.
By the way, that Carvin 4-12 is a sweet cab and some of their amps look
very nice. Would be great to demo a few...
cheers
enjoy you amp
skip
nosp...@juno.com
Alan Thompson
Starting with the 900 series, the impedance selector only has two positions -
8ohms and 4/16. It seems that they use the same back panel for combos and
heads, but the 4/16 position is actually 4ohms on the combo (to use with a
matching 8 ohm ext cab), and 16 ohms on the head.
A.T.
Andrew McWhirter
Skip May wrote:
>
> While looking through my latest Carvin Catalog last night, I did notice
> that Carvin mentions their 4-12 cab is a 4 and 8 ohm box.
Is that the same box? Selectable at either 4 or 8 ohms? How can that be? Or
is it *available* as either 4 or 8 ohms (ie with different speakers inside)?
Just curious....I can't see how you could take the same four speakers and wire
them as 4 ohms one way, 8 the other.
And just so you don't have a go at me...I'm talking about the manufacturer's
stated nominal impedance <g>
Cheers
Andrew
--
These opinions are hereby disowned by the company I work for.
******** To email me send to ********
******** Andrew-dot-McWhirter-at-Bigfoot-dot-com ********
Doug
"James Salazar" <ter...@qnet.com> wrote:
>I have a Marshall JCM 800 that I run through a Carvin 4x12 cab. I have the
>marshall dialed in at 8 ohms bu the Carvin cab says it's wired at 4ohms.
>When I switch the Marshall to 4ohms to match the cabs requirements it
>changes the tone dramatically and basically sounds like shit and ruins my
>tone.
>My question is, Will this hurt the amp?
> Jim
Yep it sure can. It's not as bad to go from high to low (8 ohm amp to
4 ohm cab) as it is from low to high (4 ohm head to 16 ohm cab for
example) but you are taking a chance.
Doug
Ross Stites
Andrew McWhirter <SeeM...@bottom.NOSPAM> writes:
>Skip May wrote:
>>
>> While looking through my latest Carvin Catalog last night, I did notice
>> that Carvin mentions their 4-12 cab is a 4 and 8 ohm box.
>Is that the same box? Selectable at either 4 or 8 ohms? How can that be? Or
>is it *available* as either 4 or 8 ohms (ie with different speakers inside)?
>Just curious....I can't see how you could take the same four speakers and wire
>them as 4 ohms one way, 8 the other.
>And just so you don't have a go at me...I'm talking about the manufacturer's
>stated nominal impedance <g>
The only way you could do it is to have the 4x12 cab be switchable
between mono and stereo. In mono it's 8 ohms, and in stereo it's
4 ohms on each side (though inside the same cab). Of course, this
could actually be reversed (8 ohms stereo/4 ohms mono) depending
on how it's wired.
Btw, this is how 'modern' Marshall 4x12 cabs are wired, except
they are 8/16 ohms.
Ross
Alan Thompson
I think you've got your info backward. It's safer to put a 16ohm speaker on an
8ohm output (you'll get less power) than to put a 4ohm speaker on the same 8ohm
output.
A.T.
aschuwer
Alan Thompson wrote:
>
> I think you've got your info backward. It's safer to put a 16ohm speaker on an
> 8ohm output (you'll get less power) than to put a 4ohm speaker on the same 8ohm
> output.
When playing at higher volumes, its NOT safe to put a 16 ohm speaker on
a 8 ohm output (tube amp)!
Too less load gives to high voltages in your powertube circuit and power
transformer. One of those can die.
regards,
TS
Alan Thompson
"Too less load"? What does that mean? Besides being grammatically incorrect, a
16ohm load on an 8ohm output is a higher load, higher impedance.
A.T.
aschuwer
Alan Thompson wrote:
>
> "Too less load"? What does that mean? Besides being grammatically incorrect, a
> 16ohm load on an 8ohm output is a higher load, higher impedance.
>
> A.T.
I know,
16 ohm is a higher impedance than 8, but 16 ohms does not "load" the
power amp as much as a 8 ohms.
TS
Ross Stites
aschuwer <asch...@best.ms.philips.com> writes:
>Alan Thompson wrote:
>>
>> I think you've got your info backward. It's safer to put a 16ohm speaker on an
>> 8ohm output (you'll get less power) than to put a 4ohm speaker on the same 8ohm
>> output.
>When playing at higher volumes, its NOT safe to put a 16 ohm speaker on
>a 8 ohm output (tube amp)!
>Too less load gives to high voltages in your powertube circuit and power
>transformer. One of those can die.
Correct. I think what a lot of people don't realize is that a
SS amp is a voltage source, so it wants to maintain a given voltage
to whatever the load is. Too low of load causes it to smoke becuause
too much current is drawn to maintain the voltage. OTOH a tube amp is
a current source. Too high of impedance gives it trouble because
it 'wants' to provide a given current, and the high impedance causes
it to smoke because it tries to provide a higher voltage than
is safe. In both cases, the problem is that more power is being
drawn from the source than can be safely provided. The difference
is how the two react to an impedance mismatch.
Ross
Skip May
: Andrew McWhirter (SeeM...@bottom.NOSPAM) wrote:
: Is that the same box? Selectable at either 4 or 8 ohms? How can that be? Or
: is it *available* as either 4 or 8 ohms (ie with different speakers inside)?
Well Andrew, why don't you stop fishing for an argument and get a hold of
a carvin catalog.
: Just curious....I can't see how you could take the same four speakers and wire
: them as 4 ohms one way, 8 the other.
: And just so you don't have a go at me...I'm talking about the manufacturer's
: stated nominal impedance <g>
:
: Cheers
: Andrew
: --
Try looking through Carvins' catalog first, then get back to us when you
have something serious to add to the original topic.
skip
nosp...@juno.com
Alan Thompson
Now I'm really confused. This has caused me to re-evaluate all of my long-held
beliefs, and even my reason for being. I will now join a Polka band!
A.T.
Andrew McWhirter
Skip May wrote:
>
> : Andrew McWhirter (SeeM...@bottom.NOSPAM) wrote:
> : Is that the same box? Selectable at either 4 or 8 ohms? How can that
> : be? Or is it *available* as either 4 or 8 ohms (ie with different
> : speakers inside)?
> :
> Well Andrew, why don't you stop fishing for an argument and get a hold of
> a carvin catalog.
Not fishing for an argument, it's genuine question. And since I'm
> : Just curious....
I won't bother getting a catalogue (if I even could find someone in Oz who
sells Carvin).
> : I can't see how you could take the same four speakers and wire
> : them as 4 ohms one way, 8 the other.
> : And just so you don't have a go at me...I'm talking about the
> : manufacturer's stated nominal impedance <g>
>
> Try looking through Carvins' catalog first, then get back to us when you
> have something serious to add to the original topic.
>
> skip
> nosp...@juno.com
Ummm...Skip, I don't have anything to add to the original topic (can't even
remember what it was), and that is why I changed the subject. 'zat ok?
It was a serious comment. It seemed to me that your post was suggesting
that the same 4 x12 box could provide 4ohm or 8ohm nominal, and I wondered
how that could be. You being the expert on speaker impedances and all...
Larry
My Bel Air has an impedance switch on the back of the amp. I think it's
in case you use _other_ speakers than what comes in the combo...
-Larry
Andrew McWhirter <SeeM...@bottom.NOSPAM> wrote:
> Skip May wrote:
> >
> > While looking through my latest Carvin Catalog last night, I did notice
> > that Carvin mentions their 4-12 cab is a 4 and 8 ohm box.
>
> Is that the same box? Selectable at either 4 or 8 ohms? How can that be? Or
> is it *available* as either 4 or 8 ohms (ie with different speakers inside)?
>
> Just curious....I can't see how you could take the same four speakers and wire
> them as 4 ohms one way, 8 the other.
>
> And just so you don't have a go at me...I'm talking about the manufacturer's
> stated nominal impedance <g>
>
Mike Teague
>Skip May wrote:
>>
>> : Andrew McWhirter (SeeM...@bottom.NOSPAM) wrote:
>> : Is that the same box? Selectable at either 4 or 8 ohms? How can that
>> : be? Or is it *available* as either 4 or 8 ohms (ie with different
>> : speakers inside)?
>> :
>> Well Andrew, why don't you stop fishing for an argument and get a hold of
>> a carvin catalog.
>
>Not fishing for an argument, it's genuine question. And since I'm
>> : Just curious....
>I won't bother getting a catalogue (if I even could find someone in Oz who
>sells Carvin).
>
>> : I can't see how you could take the same four speakers and wire
>> : them as 4 ohms one way, 8 the other.
>> : And just so you don't have a go at me...I'm talking about the
>> : manufacturer's stated nominal impedance <g>
>>
>> Try looking through Carvins' catalog first, then get back to us when you
>> have something serious to add to the original topic.
>>
>> skip
>> nosp...@juno.com
>
>Ummm...Skip, I don't have anything to add to the original topic (can't even
>remember what it was), and that is why I changed the subject. 'zat ok?
>
>It was a serious comment. It seemed to me that your post was suggesting
>that the same 4 x12 box could provide 4ohm or 8ohm nominal, and I wondered
>how that could be. You being the expert on speaker impedances and all...
I own a carvin 412T 4x12...
The switch takes you from 8 ohm MONO to 4 ohm per side STEREO..
--
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