Dual Speaker Impedances

[tom daghdha]

If I was to make a 2x15" subwoofer, (for concert application), is it plausible to have it end up at 8 ohms? Eminence don't seem to make anything bigger/better than the Delta 12 in 16 ohms, and wiring two 4 ohm drivers in series would seem to be inviting trouble if one of them blows. Or would this be alright?

[lndm]

If you mean that if one goes open circuit they'll both go silent and the amp will see no load, then yes.

[tom daghdha]

Yeah, that's the point - wiring them in series would could cause them both to fail if one did.

PD and some other manufactuers seem to make 16ohm drivers, so maybe it's just that eminence don't stock them.

[nunayafb]

and wiring two 4 ohm drivers in series would seem to be inviting trouble if one of them blows. Or would this be alright?

Heres how I would look at it: if you might blow a woofer it is not big enough to handle the job, so go bigger and not worry about it.
Also, if one blows while driving two in parallel, you are going to have seiously reduced bass(-3dB from Sd, -3dB from doubling impedance) and this would suck so going bigger would prevent that. If one blows while wired in series(4ohm stable amp) you can bypass it and and not lose any spl, (-3dB for Sd reduction, +3dB for voltage sensitivity 4 instead of 8ohms). Of course you'll be driving the remaining woofer twice as hard.
Unless Im missing something about concert speakers the logic is sound

[tom daghdha]

To be honest, blowing them's not really a likely occurance. I'm not going to be driving them any harder than they're rated, it was just as a possibility.

So if I ran two 4ohm 1000w speakers in parallel, I'd effectively have a 2000w 8ohm cabinet?

Would there be any difference in efficiency compared to any other combination? Wiring speakers in series in cabinets wouldn't be something that would seem instinctively right.

[tom daghdha]

So if I ran two 4ohm 1000w speakers in parallel, I'd effectively have a 2000w 8ohm cabinet?

In addition to this, if I had two 8ohm 1000w speakers and wired them in series, what would be the overall power rating of the cabinet?

I'm sorry about the basic questions, I am usually fairly clued up on live sound and the like but this is just something I want to be sure of.

[pinkmouse]

Originally posted by tom daghdha
PD and some other manufactuers seem to make 16ohm drivers, so maybe it's just that eminence don't stock them.

PD, (and most other pro manufacturers), make 16 Ohm drivers specifically so you can quad them up to give a 4 Ohm load.

In addition to this, if I had two 8ohm 1000w speakers and wired them in series, what would be the overall power rating of the cabinet?

16 Ohm 2000w.

[tom daghdha]

Thanks for that, it was just the power handling I wasn't sure about. In your opinion, would there be any advantage in either configuration over the other? (2 series wired 4 ohm drivers, or 2 paralleled 16 ohm drivers.)

[pinkmouse]

I'd always go parallel. That way, if you lose a driver, you still get sound.

[AndrewT]

Hi,
I think this must have been a typo

if I ran two 4ohm 1000w speakers in parallel, I'd effectively have a 2000w 8ohm cabinet

you did mean 2ohm when in parallel and 8ohm when in series.

I agree with Pinky. Wire speakers in parallel not series.
If the amplifier cannot work efficently into a low load value then drive them independantly with a pair of amplifiers.