Should I make my 4 x 12 cab a 2 x 12?

[Pink Unicorn Horsey]

I've got a Mesa 4 x 12 Recto loaded with four Celestion Vintage 30s. I know the load of the cab is 8 ohms. I'm not sure the resistance of each speaker but I'm guessing they're 8 ohms a piece. If that's the case, my assumption is that the speakers are wired with pairs parallel (for an equivalent load of 4 ohms) then those pairs in series (for a final load of 8 ohms). Can anyone confirm this?

If that's the case and the speakers are indeed 8 ohms, I should be able to make a 16-ohm 2 x 12 cab by taking out two of the speakers, wiring them in series and putting them in a new 2 x 12 enclosure. I already have a 16-ohm THD Hotplate so making this 2 x 12 makes it possible to use it for not only my Vox but also this 2 x 12 that I'd use with my Mesa DC-5. Only problem is that the DC-5 has one 8-ohm speaker out and two 4-ohm speaker outs. Overloading the DC-5 head won't harm the amp but does affect the tone (probably not in a good way).

Thoughts?

- Keith

 

[The Golden Boy]

Re: Should I make my 4 x 12 cab a 2 x 12?

I don't know of your cab, but if it's 8 ohms and a 4x12 then the speakers are more than likely 8 ohms a piece in a series-parallel (I can't spell "parallel" to save my life) configuration.

So you're basically talking about yanking 2 speakers, putting them in a seperate cab? Wire the two speakers in series and that should be 16 ohms.

 

[Pink Unicorn Horsey]

Re: Should I make my 4 x 12 cab a 2 x 12?

I don't know of your cab, but if it's 8 ohms and a 4x12 then the speakers are more than likely 8 ohms a piece in a series-parallel (I can't spell "parallel" to save my life) configuration.

So you're basically talking about yanking 2 speakers, putting them in a seperate cab? Wire the two speakers in series and that should be 16 ohms.

You just said what I already said.

 

[aleclee]

Re: Should I make my 4 x 12 cab a 2 x 12?

Speakers wired in series sound different from speakers wired in parallel. You may or may not prefer that configuration.

 

[Pink Unicorn Horsey]

Re: Should I make my 4 x 12 cab a 2 x 12?

They do? How so?

Also, how are most 2 x 12 combos wired?

 

[the guy who invented fire]

Re: Should I make my 4 x 12 cab a 2 x 12?

I have never heard that...could you explain the difference in tone?

Speakers wired in series sound different from speakers wired in parallel. You may or may not prefer that configuration.

 

[aleclee]

Re: Should I make my 4 x 12 cab a 2 x 12?

I have never heard that...could you explain the difference in tone?

Series is brighter while parallel is smoother. From a thread on The Gear Page:

What happens is this: two speakers when wired in parallel have half the inductance of one alone, and in series they have double that of one alone (just like resistance). Thus there is a 1:4 difference in inductance between 4 and 16 ohms, with the same speakers. In the OT, the inductance is dependent on the number of turns, but the impedance ratio is the square of the turns ratio - so the 16-ohm winding only has twice the number of turns as the 4-ohm, and only twice the inductance.

Thus, at 16 ohms there is relatively more inductance in the speakers compared to the OT than there is at 4. The OT-speaker circuit is in fact a closed loop around which current flows. Because high frequencies in a circuit are distributed more to larger inductances, at 16 ohms more highs are developed in the speakers than at 4 (the rest are lost in the OT itself).

There is also the effect of series and parallel wiring changing the damping factor of the speakers and the OT-speaker circuit. That's a bit more complicated and I'm not sure I know the various equations... I bet Randall Aiken does though.

 

[aleclee]

Re: Should I make my 4 x 12 cab a 2 x 12?

They do? How so?

Also, how are most 2 x 12 combos wired?

2x12s are typically wired in parallel.

4x12s are typically wired with two parallel pairs connected in series. That configuration also sounds different from two series pairs connected in parallel.

 

[The Golden Boy]

Re: Should I make my 4 x 12 cab a 2 x 12?

I've heard that too. I've never done any messing around with it to decide for myself. I did have a friend wire his 16 ohm 4x12 to 4 ohms and rave about how great it sounded- I couldn't tell the difference. But then again, I didn't pay close attention to how it sounded beforehand.

 

[The Golden Boy]

Re: Should I make my 4 x 12 cab a 2 x 12?

You just said what I already said.

"You keep using that word, I do not think it means what you think it means."

Or maybe:

"You really shouldn't mumble when you talk. Honestly, I can't understand a word you're saying."

Or more likely:

I'm like :duh:

:laugh2: :laugh2:

 

[Naps]

Re: Should I make my 4 x 12 cab a 2 x 12?

http://www.avatarspeakers.com/wiring diagrams.htm

Wireing two 8ohm speakers in series makes 16ohm

Wireing two 8ohm speakers in parallel makes 4ohms

I'm going to guess that your Mesa will have a 4ohm out and the vox a 16ohm out. So, wiring one pair in series and one pair in parallel my be the best option for you. That way you can plug both amps into the 'same cabnet.'

 

[Pink Unicorn Horsey]

Re: Should I make my 4 x 12 cab a 2 x 12?

"You keep using that word, I do not think it means what you think it means."

Or maybe:

"You really shouldn't mumble when you talk. Honestly, I can't understand a word you're saying."

Or more likely:

I'm like :duh:

:laugh2: :laugh2:

Inconceivable!

 

[Pink Unicorn Horsey]

Re: Should I make my 4 x 12 cab a 2 x 12?

http://www.avatarspeakers.com/wiring%20diagrams.htm

Wireing two 8ohm speakers in series makes 16ohm

Wireing two 8ohm speakers in parallel makes 4ohms

I'm going to guess that your Mesa will have a 4ohm out and the vox a 16ohm out. So, wiring one pair in series and one pair in parallel my be the best option for you. That way you can plug both amps into the 'same cabnet.'

Yup, I know the formulas. My Mesa has one 8-ohm output jack and two 4-ohm output jacks. Since my 4 x 12 is an 8-ohm load I just plug it into the 8-ohm jack and I'm good to go. According to the user's manual, I can connect one 8-ohm speaker to each of the 4-ohm jacks since the equivalent load is 4 ohms; this tells me the 4-ohm jacks are wired in parallel.

Any idea if it's safe to plug a single 4-ohm load into only one of the 4-ohm jacks and leave the other jacks disconnected without damaging the amplifier? If so, I could make a 2 x 12 from two 8-ohm speakers wired in parallel and just connect it to one of the 4-ohm jacks.

- Keith