sub amp ohm/wattage question

[nebrunner]

I have a mono amp that does 1000 watts at 4 ohms. If I have 3x 4ohm subs, A, B and C, all wired in series, what ohm load would the amp see and what wattage would each sub get? 12 ohms and 111 watts?

Same situation but you wire sub B and sub C to each other in parallel, then that in series with sub A. What ohm load and wattage would that result in?

[nebrunner]

another scenario:

B and C wired in series to each other, then this is wired in parallel with A.

how much wattage would go to each?

[BobDolez]

another scenario:

B and C wired in series to each other, then this is wired in parallel with A.

how much wattage would go to each?

Resistors in series:

RTOTAL = R1 + R2 + R3 + ...

Resistors in parallel:

1 / RTOTAL = (1 / R1) + (1 / R2) + (1 / R3) + ...

In your last one, you would add you B + C = 8
and put in parallel with A 4
.... so
1/8 + 1/4 = 3/8....
inverse 8/3 or 2 2/3 ohm total load.

Assuming 1000 W @ 4 ohm... This would give you approx.1.5 X 1000 (1500) watts total @ 2 2/3 ohm.

Your power split would be squirrelly with one leg being 4 ohm and the other being 8 ohm....
Your current for speaker A will be double of speakers B and C....
A 1000 W
B 250 W
C 250 W


I'm tired... so I hope my memory/math is up to par.:peeping:

A perfect amplifier with 100 W @ 8 ohm would do 200 W @ 4 ohm, but that is not always the case. As you lower the load on an amplifier, you're also demanding more current to produce more watts. Some amplifiers are built to handle this.. others, not so much. There are plenty of articles about the subject with a bit of googling.

[dane]

Bob your math all looks good to me at first glance. But more important are the warnings at the END of your post that should be at the beginning. :) Few amps double into half the load. Not all amps that can take 4ohm are even stable into 2ohm.

FOUR subs would be an easy situation here; two groups in parallel where each group has two subs in series. Each series leg would double to 8ohm, and the two legs of 8ohm in parallel would half back down to 4ohm, a perfect load for the amp. That's also assuming that the four subs presented identical loads (same make/model). Differing types of subs in that combination may not provide such a clean setup because different drivers and cabinet combinations present different loads at different frequencies, creating a potential imbalance (over frequency) across all the subs.

All three in parallel is most certainly a bad idea (unless you know your amp is stable into close to DC), and the 1-2 series-parallel combination is equally wrought with potential problems (IMO)..

Better to go with two in series (8ohm) or get a fourth and do a series-parallel group into 4ohm in this case..

Alternatively, sell the amp and get a three-channel amp? :)

..dane

[nebrunner]

Selling it isn't an option right now, I need to try to make the best with what I have got, at least in the short term.

How about just letting them all stay in series. 12 ohm load, that should be easier on the amp, not harder...right?

[dane]

12ohm load will certainly work and put a lot less stress on the amp. You'll get a little less power out of the amp, but will certainly not damage anything that way.

..dane