Peavey 212m stereo ohm's question

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LhKramerLunatic
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Peavey 212m stereo ohm's question

Post by LhKramerLunatic » Sat Aug 18, 2018 8:56 pm

so i picked up a early 90's or late 80's peavey 212m stereo cab

it has to 16 ohm sheffield 1230's....cant find the wattage on them,but thats not my trouble.

now the jack panel has stereo jacks at 16 ohm's and 8 ohm mono jack

if i pull out one and add a wgs retro 30 at 8ohm and disable the other 16 ohm 1230 what wld i select for the head?

wld i plug into the 8 ohm mono jack thats connected to the 1 wgs 30 @ 8 ohms and put the xxx head at 8 or 4?

cause i thinkin the imput jack board wld be changin the 2 16s to one 8 ohm load?

or will it cause the whole steup to change to 4 ohm mono and 8 ohm stereo with 2... 8 ohm wgs retro 30's when i get the other on in it?

now im really confused,lol...........any help wld be great
1986 lefty Focus 6000
1992 ibanez 170L

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_xxx_
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Peavey 212m stereo ohm's question

Post by _xxx_ » Sun Aug 19, 2018 5:25 am

Didn't quite get your explanation, but when you have no exact match, the impedance setting on the amp should always be set lower than the speakers.

That said, mixing speakers with different impedance is a big no-no :nono

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gtrjunior
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Peavey 212m stereo ohm's question

Post by gtrjunior » Sun Aug 19, 2018 7:17 am

I understood it to mean that he will be running only one Retro 30 in the 2x12 cab and disabling the the stock speaker.
I’m no expert but I believe that you should plug into the mono input and run the amp at 8ohms. Be sure to completely unplug the other speaker.

That said, I’m not really sure why you would want to do this?
If it were me, I’d just get two speakers with matching impediances and wire them up as needed. If you don’t play a stereo rig, then just wire them up to be mono and have at it.
Whenever I have wired up a cab, I always need to refer to a diagram. I can never remember which was is Series and which is parallel.

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SWANTECH
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Peavey 212m stereo ohm's question

Post by SWANTECH » Sun Aug 19, 2018 8:02 am

The simple answer is this.
If you are only using 1 speaker just buy a 16 ohm speaker. Then select 16 ohm on your head.
This will alow you to add another 16 ohm speaker in the future if you would like.
Joe in Detroit
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LhKramerLunatic
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Peavey 212m stereo ohm's question

Post by LhKramerLunatic » Sun Aug 19, 2018 8:30 am

Yea i new it was gonna go badly after i posted this,lol

1.. speakers were toasted

2.. i have a brand new 8 ohm retro 30 layin around,so that only give me a single speaker to use,so i can put it in and leave the stock one unpluged,as jts a mismatch.

3..its fills the hole till i can get another 8 ohm retro 30

4.. so i want to play around with the cab,but it had the 16 ohm stereo taps and 1 8ohm mono tap.

Whats happens to this setup when u change the spreakers to 8 ohm instead of 16 ohm?

I know it sounds dumb in my first thread,but i cldnt decide on how to try and explain it,.

The internal jack board does something right?
2 16 ohm speakers in stereo and then 8 ohm mono

What happens when u xhange to 8 ohm speakers in the same setup?

I wld just elimnate the jacks and the circuit board and wire in 2 taps ala orange or mesa style,but i dont have any of that stuff at the moment and was just gonna use it with 1 soeaker till i get around to permantly fixin it.

5..I like 8 ohm speakers best.

Sorry it shld be a simple thing,but my head keeps gettin in the way!!
1986 lefty Focus 6000
1992 ibanez 170L

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SWANTECH
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Peavey 212m stereo ohm's question

Post by SWANTECH » Sun Aug 19, 2018 8:35 am

To calculate parallel cabs, or speakers here is the math.
It is simple to memorize.
A + B = C, divided by A x B = C.
Using this formula.
Here is an example.
Speaker A is 8 ohms.
Speaker B is 8 ohms.

A (8) + B (8) = C (16)
A (8) x B (8) = C (64)
64 / 16 = 4
Select 4 Ohm on your head.
Now look what happens when you start mismatching ratings.
A (8) + B (4) = C (12)
A (8) X B (4) = C (32)
32 / 12 = 2.666
This is really bad.
Just an FYI.
People do this all this time with bass cabs and wonder why the cabs and amps blow up.
Be very careful when buying used bass amps, and cabs. Bass players miss match stuff all the time.
Just an FYI.
Hope this helps.
Joe in Detroit
85 Striker 100ST Blk (1st E. Guitar)
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86 Focus 1000 Blk (FS)
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LhKramerLunatic
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Peavey 212m stereo ohm's question

Post by LhKramerLunatic » Sun Aug 19, 2018 8:39 am

I know that with the cab working correctly i wld set the head accordly.....

16 ohm stereo

8 ohm mono

But if u change the soeakers inside ur cab to 8 ohm

What does the standard conversion become inside the cab now?

8 ohm stereo..?

4 ohm mono..?

Of course one speaker will only be workin at the time,but i will just use the proper stereo tap its hooked too....

Untill i can add another 8 ohm retro 30 and wire in new taps wired correctly.

Just dont want to fry my xxx head...

Sorry for the headaches fellas and thx for the help,lol
1986 lefty Focus 6000
1992 ibanez 170L

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gtrjunior
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Re: Peavey 212m stereo ohm's question

Post by gtrjunior » Sun Aug 19, 2018 8:46 am

If it were me I’d just eliminate the stereo wiring and set it up mono.
That is of course unless you plan on using a stereo setup. I personally, in 30 years of playing guitar have never used a stereo setup. So for me it’s unnecessary. YMMV.
Here’s the diagram I refer to for the wiring.
https://static1.squarespace.com/static/ ... 2/2x12.jpg

LhKramerLunatic
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Peavey 212m stereo ohm's question

Post by LhKramerLunatic » Sun Aug 19, 2018 9:19 am

LMAO!!!

im an idiot,ive got stop thinkin so much,lol...

Got it figured out thx Fella's for all the help.
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_xxx_
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Peavey 212m stereo ohm's question

Post by _xxx_ » Sun Aug 19, 2018 9:41 am

You are thinking too much :toast

Just remove all the old wiring and connect your single speaker to the input jack and set the impedance accordingly. When you get a second one, it goes like this:

Series:
R = R1 + R2

Parallel:
R = (R1*R2)/(R1+R2)

... as Swantech explained above. Mismatched speakers can only be wired in series (say 8 + 4 = 12 Ohm) and then you set the amp to 8 Ohm, that will also work but you will have like ~70W max instead of 100. Not a problem unless you play with volume on 10 all the time.

Also be careful not to reverse the phase, otherwise you will pull the speaker membrane inside when hitting a note, which is bad.

Always use a thick speaker cable between the amp and the box, otherwise you may fry both.

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