Mesa Powerhouse 4x10 wiring/impedence change?

[EatMoreCarrots]

I've run a 400+ for a long time so when I got my 4x10 I never thought twice about its ohm rating (the 400+ will put out full power at 2, 4, or 8 ohms). However, now that I am toying around with the idea of picking up a Walkabout (4ohm minimum load recommended), I am wishing my cab 4ohms instead of 8ohms. Short of replacing the speakers or selling it to order a 4ohm version, is there not a way to change it from 8 to 4?

Gathering the facts:

Speakers: I called Mesa and was told the 8ohm 4x10 Powerhouse cabs have 8ohm speakers but that the 4ohm versions have 16ohm speakers (though the Customer Service guy didn't sound exactly sure and said he could check with production). Does anyone have a definitive answer for what the speaker ratings are on these cabs? (I prefer not to go through the process of taking mine apart to measure.)

Wiring: If my cab is full of 8ohm speakers, forgive my lack of wiring knowledge, but does that mean that all 4 are wired in series to make the whole cab = the impedance of a single speaker in the cab? I have read elsewhere that it is possible to rewire this 8ohm cab down to 2ohms (The Mesa C.S. guy I spoke to sort of confirmed this) - would that mean wiring all 4 speakers in parallel? Please educate me on this point.

Initial ideas: Would it not be possible to wire the speakers in series pairs and then wire the pairs in parallel? Would not be the equivalent to pairing 2 8ohm Powerhouse 2x10's to get 4ohms? If this is true (or some other wiring trickery if I've got my terms backwards), would it pose problems with the crossover and horn?

Thanks upfront to everyone who can help educate me on cab impedance! OH - and please, don't litter this thread with comments about it being cool to run the Walkabout at 2ohms. I'm not doing that. (Besides, If I wired this at 2ohms, I'd be unable to pair it with anything else under my 400+.)

[Bass_Pounder]

It is NEVER possible to make a 8 ohm cab into a 4 ohm cab, and vice versa without replacing the speakers.

[RickenBoogie]

Yup, very common question, and the answer never changes. It cannot be done. Besides, the Walkabout through an 8 ohm 410 will sound huge, and you could always add another 8 ohm cab to make it huger. Only other option is to sell your cab, and buy another.

[EatMoreCarrots]

Yea, well... damn it. I figured this was the answer. Thanks for the comments.

However, I'd really still like to understand WHY. And also just be more knowledgeable about how speaker impedance and wiring on these cabs work together to make them 4 or 8 ohms.

[sunbeast]

Four 8 ohm speakers in parallel= 2 ohms
Four 8 ohm speakers in series= 32 ohms
Four 8 ohm speakers in series/parallel= 8 ohms

You can Google search speaker impedance for in depth details!

[BassmanPaul]

I'll try to explain. To get a total of 8Ω there are two ways to go. Four 32Ω speakers, ALA Ampeg, in parallel 32/4 = 8Ω. The other way is four 8Ω speakers, each pair in wired series gives you two sets of 16Ω. Wiring these in parallel 16/2 = 8Ω.

The first example will never be able to reach 4Ω no matter what you do. The second, the only wiring change you can make is to wire all in parallel. That gives you 2Ω. Again no way of getting to 4Ω.

Hope that helps.

Paul

[EatMoreCarrots]

To Sunbeast & Bassmanpaul:
Thank you. That was exactly what I trying to understand. I'm clear now.

Sunbeast:
I've seen your walkabout on the local CL (as well as the classifieds here). I'm very tempted! I also used to rock an 800RB for a long time but that's long gone (for shame).

[sunbeast]

Funny- feel free to come check it out! I owned and loved a 400+ for several years, but I certainly don't miss the weight (and like to be able to get the great tones at low volumes!).

[EatMoreCarrots]

OK BassmanPaul and Sunbeast, I've got a follow-up. Based on the above wiring and speaker impedance knowledge, I am now wondering how it is that 6 x 10 cabs are typically wired to 4 ohms?

[sunbeast]

I believe my Bergantino uses six custom 24 ohm speakers in parallel. I know for sure that Ampeg 810s are eight 32 ohm speakers in parallel...the original thinking behind the all-parallel design was that if one speaker went dead, the rest would still function with only a minimal impedance change

[EatMoreCarrots]

I get the 8x10 ampeg math and I get. And I get your your Bergantino with special impedance speakers... but Mesa only uses either 8 or 16ohm 10's (http://mesa.stores.yahoo.net/10inbasp.html) and I can't figure out what wiring configuration on six 8ohm or six 16ohm speakers would net a 4 ohm 6x10 cab.

[sunbeast]

There isn't a way that I could imagine that would net a 4 ohm load from six 8 or 16 ohm speakers...You could get it with a combination of the two, but then there wouldn't be a balance of power going to each speaker. I wonder if they don't have custom speakers for that cabinet that just aren't listed in their store?

[BassmanPaul]

Many 6x10 cabs have a 5.3Ω terminal impedance from six 8Ω drivers connected in series/parallel.

8Ω drivers are the standard nowadays. in the UK it was 16Ω at one time. 4Ω drivers are also available but are few. If you are a manufacturer you can order whatever specs you need from the driver manufacture. Impedance is just one of those specs.

Paul

[georgestrings]

Originally Posted by sunbeast

There isn't a way that I could imagine that would net a 4 ohm load from six 8 or 16 ohm speakers...You could get it with a combination of the two, but then there wouldn't be a balance of power going to each speaker. I wonder if they don't have custom speakers for that cabinet that just aren't listed in their store?

I have a PH610, and have had speakers replaced under warranty a couple of times - according to what Mesa told me, the speakers in their 610s are application specific for that cab, and different than the ones used in their 410s or 810s...



- georgestrings