Adwex

Yes, there is a problem. 2 8x10 cabs, at 4 ohms each, will equal 2 ohms when you them both into the amp. I don't know of any amp that can run at 2 ohms.

You could wire the two cabs in series with each other, then they would combine to equal 8 ohms.

tim warner

I was going to ask in another thread but you guys are already started.
I have 2 g12m 16 ohm speakers that I want to hook these up to my 100 watt superlead,
I know I won't be able to (give'er all she's got), but what is the best way to wire these?

Adwex

There is only one way to wire them, in parallel. The result will be 8 ohms.
The max power handling of this combination will be 50 watts. Your 100 watt superlead is quite capable of blowing the speakers if you crank it.

Jimib

If your amp can go to 2ohms then it's not a problem but running two 4ohm cabs on 4ohms could get nasty so no lol ....

__________________
JTM 45 RI
1960 AHW

cadaver_occulta

So 2 8x10 (or 12) cabinets could not be plugged in the same way that 2 4x10 (or 12) cabinets could but plugged in to make a full stack...is that correct? Even if each individual speaker is 16ohms each (which would come out 4ohms?) it shouldn't be done?

Btw, please correct me of any incorrect information, I REALLY dont wanna fry any equipment that I can't afford to replace!!!

__________________
Jeg er Ondskapelsens
Jeg er Antikrist

Jimib

A question myself...
Would it be possible to run a 16ohm cab and an 8ohm cab at 4 ohms? thanks

__________________
JTM 45 RI
1960 AHW

Adwex

If the 8x10 cabs are 4 ohms each (the total is what's important, not the individual speakers), then when you connect 2 of them to your amp, the total your amp "sees" is 2 ohms.

If your amp does not have a 2 ohm setting (and I don't think it does), do not connect the 2 8x10 cabs.

Adwex

No.

A 16 ohm cab and an 8 ohm cab when connected in parallel will equal 5.33 ohms.
I can show the math if you want.

Jimib

right... I thought that it would be ok then at 5.33 considering its not below 4? please excuse my ignorance lol

__________________
JTM 45 RI
1960 AHW

Jimib

Am I incorrect in saying that?

__________________
JTM 45 RI
1960 AHW

Adwex

You MIGHT be ok, but you'll be taking a risk.

You should always match impedance.

Radiokt3k

I have:
1 jcm2000 head with 4,8, and 16 selectable switch.
1 1960A 4x12 cab with 4 G12T-75 Celestions wired in Parallel

Can I come out of the 16ohm mono jack from the head with switch
set to 4 ohms to the cabinet?

Thanks,
John

American Viking

NO.

If you only have one cabinet, it's
16 amp out to 16 cab in
or
8 amp out to 8 cab in
or
4 amp out to 4 cab in

The back of the 1960 cab is clearly marked on the right input, MONO 16ohms. Have the switch set to MONO also. Mismatching the impedance will severely damage your amp.
Even safely running the amplifier at 4ohms from the amp to 4ohms on the cab runs your amp harder and stresses it out for no reason. There is no auditory benefits for running low impedance. Stay at 16ohms and keep your amp happy.

__________________
-I'd rather be a good liver than have one...

Adwex

American Viking speaks the truth...words to live by.

Always match impedance.

Always.

__________________
http://www.youtube.com/MarshallLesPaul

wizard_37

I have a quick question, I am fixing to rewire my cab because the wiring is pretty old and I would like to upgrade it, I was thinking about using thicker wire because the exsisting wire is pretty small, which wire would be the best to use?

Adwex

I used standard speaker wire I got at Radio Shack (or any electronic store).
I think I chose 14 or 12 gauge, I don't remember. 16 would be ok, but like you, I wanted to upgrade. Btw, in case you didn't know, the lower the gauge number, the thicker the wire.

__________________
http://www.youtube.com/MarshallLesPaul

grobinson

so i thought id attach something ive been working on.
16ohm mono / 4ohm mono switching using jacks only and no DPDT switch.

you could use a similar setup (just one switcing jack) to copy the stereo 2x12 input jack plate and just add 2 more 16ohm speakers in parallel to the original two (in two pairs) to get 4ohm mono and 8ohm stereo.


anyway. my diagram.
if someone can take a look at check my wiring and maths is right, i would be happy.
i just boshed this up in photoshop. the green lines mark 'live' signal routes when the jack is put into a socket. the lower switches are all Tip, the upper switches are Sleeve

Attached Images

wiring.jpg (89.0 KB, 27 views)

funkplayer

Greetings and salutations from one of your newest members -

I have a Marshall AVT150H w/1960A (300W)- We pratice in a small space and the sound from the cabinet just blows by me at like knee level. I would like to connect a EV-Force I 8ohm 15" spkr with ti horn as a monitor in front of me. The 1960A cabinet is currently plugged into the 8/4ohm jack from the AVT150H. There is another 8ohm jack on the AVT150H. Can I use this jack to run the EV monitor as well as leaving the 1960A plugged into the 8/4ohm jack?

Mr69bungle

Please help I am trying to convert my 8 ohm MONO cab to a Stereo cab!
I've checked here- Wiring a 4 X 12 Speaker cabinet for a diagram but as this is my first wiring experience and as i don't want to botch it up I thought I'd ask you're advice.

The mono setup is shown in the attached pic which is wired up red wire to A1 and black wire to B1 which from my thinking is Speakers in Series-Parallel?

So I'm just not sure where to connect the mono and stereo wires to get a 4 Speaker Switchable Stereo/Mono setup.

I'm thinking that maybe i have to connect the stereo wires to red C1 and black D1??? is that right or do i have to do something different???

Please help - thanks in advance P

Attached Images

	WIRING 1 LABELLED1.JPG (73.3 KB, 17 views)
	INSIDE LABELED1.JPG (80.2 KB, 13 views)
	BACK PLATE LABELLED1.JPG (69.5 KB, 8 views)
	G12 LABELLED1.JPG (63.5 KB, 9 views)

Adwex

First thing you need to realize is that the ohm values written on the jackplate will be wrong, it is intended to be used with 16 ohm speakers, not 8. It will work electrically, but the cab will not be 4/16 ohms mono or 8 ohms stereo, it will be 2/8 ohms mono or 4 ohms stereo.

In order for the system to work correctly, each half of the cab needs to be wired in parallel. When the switch is set for mono, the internal circuitry in the jackplate connects both sides in series. When set for stereo, both sides are separated from each other.

That's the theory of how it works, I could look closer and help with the actual connections if you want.

__________________
http://www.youtube.com/MarshallLesPaul

Mr69bungle

Thank you for your reply.

Yes i appreciate that the Ohms printed on the back plate would be different.

Oh right i didn't realise it would be 4 Ohms stereo - is there anyway to wire it up as 16 Ohms stereo? 2 x 8 ohm speakers = 16 ohms?

If you could specify which connectors need to go where ie. A1, B2 etc that would be awesome

Thanks again for you help

Bigger connection picture to follow

Mr69bungle

Photo attached of existing wiring and terminals marked up A1-4 etc.

Thanks in advance
P

Attached Images

WIRINGLABELLED 1.JPG (93.4 KB, 10 views)

Adwex

In order to have it wired for 16 ohms stereo, you would have to wire each half of the cab in series. As I said before, the switch on the jackplate when in mono connects both sides in series, so then you would have 32 ohms mono, with all 4 speakers wired in series.

The whole problem with all this is that you have 8 ohm speakers, not 16's. It'll work, but it's unusual, so the markings on the jackplate will be wrong, and you won't be able to use the cab in mono by itself.

__________________
http://www.youtube.com/MarshallLesPaul

Adwex

Just for clarity, could you also indicate the + and - terminals on the speakers.

__________________
http://www.youtube.com/MarshallLesPaul

Mr69bungle

Oh i didn't realise that the 8 ohm speakers would be a problem - is there any way around it? Different wiring?

I wanted to use it with two separate signals going to a 16 ohm (or 8 ohm) 2 speaker configuration on 1 side and another 16 ohm (or 8ohm) 2 speaker configuration on the other side.

I originally saw it here - Wiring a 4 X 12 Speaker cabinet

in the Cabinet Wiring Options sections about half way down
it said this:-

Mono/Stereo in same cabinet
4 Musical Intrument Speakers. Mono/Stereo selectable by using a Switch.

Option 1
4 - 4 ohm speakers = 8 ohms to each channel if run in Stereo, 4 ohms in Mono mode.

Option 2
4 - 8 ohm speakers = 16 ohms to each channel if run in Stereo, 8 ohms in Mono mode.

is that right or are they wrong??

Thanks again

Mr69bungle

I've checked the Polarities and marked them up - hope this helps.

Thanks
Porl

Attached Images

WIRINGLABELLED POLARITY.JPG (94.2 KB, 11 views)

Mr69bungle

Is it possible to do the wiring as the attached diagram suggests?

I found this on the net and wondered if it was a solution to my problem as I have 8 ohm speakers?

Mono/Stereo in same cabinet
4 Musical Intrument Speakers. Mono/Stereo selectable by using a Switch.

**Option 2**
4 - 8 ohm speakers = 16 ohms to each channel if run in Stereo, 8 ohms in Mono mode.
Is this in your opinion correct? I really don't know


The Right channel jack is completely disconnected when in Mono Mode. Do Not alter this configuration (you risk doing serious damage to your power amps if wired differently).

Mouser Electronics Sells 1/4 inch phone jacks that have a built in DPDT switch - the switch contacts are electrically isolated from the 1/4 inch Jack connection (they have to be in order for you to wire this correctly) - Marshall used this type of Jack/Switch to automatically set the speaker selection mode. They are expensive and prone to failure over time, however, using them often simplifies set-up of your rig. If you decide to use these, the Mono/Stereo switch functionality would be associated with the Right channel, where when nothing is plugged into the Right channel, the cabinet is operating in Mono Mode.

WARNING: Never run a Tube Type power amp to the Right channel if the switch is set to Mono mode - it will damage the output transformer.

NOTE: If you want Tweeters or Piezos in this configuration, you will need 2 of them, 1 per set of Woofers. This is because the speakers can be operated as seperate channels, using 2 completely different power amplifiers. The Tweeters or Piezos will be wired in parallel with the Woofers. The same arrangement as the above Dual Impedance systems.

WARNING: The Left and Right jacks cannot be mounted on the same metal plate (serious damage to some power amps will occur if you do this). Use a seperate jack plate for each channel, mounted on a non-conductive surface

Thanks for all your help so far

Attached Images

4sp_stereo_mono.gif (12.2 KB, 6 views)

Mr69bungle

Hi can anyone please help? With the wiring question above please? I need advice..
Cheers

Mr69bungle

I'm going to have a go after thinking it over - i'll let you know how i got on

uncletiki

Is it a BAD thing to drop 1 G12M 25Watt speaker into a 4x12 cab with 3 G12T 75 Watt speakers if there all the same ohms? I could use that as my main record speaker. That would save me some cash.