Question about spl gain adding new subs.


Silver Member
Username: Fandim

Reno, Nevada United State...

Post Number: 595
Registered: Jun-05
Going to just use generic numbers, for easy math etc and figuring in this question..

Ok, so if you double the power to a subwoofer, you'll gain roughly 3 dB, correct? Also, if you add another subwoofer, with identical power to the first (assuming no cancellation or phase, etc..) there is also a 3 dB gain, correct?

So my question being.. If you have a subwoofer, with 1000 watts, and add another subwoofer, on the same amp.. (assuming it's like a JL 1000/1, or PG Xenon 1200.1, puts out the same at all impedances..) That would mean you're cutting the power in half to your first subwoofer, and given half to the 2nd..

So, basically would this setup be the same volume?? I.E. You would have a -3dB for halving the power, but then gain +3 dB for adding a 2nd subwoofer with double the power?

Reason I was wondering, is because I have six 12's, rated for 300 watts RMS each.

I have them all on a Xenon 1200.1 amp, and Just four of these subs, could utilize the full 1200 watts. So would 4 of these subs be just as loud as all 6? Since if I took two out, the power distribution would give extra power to the other 4?

Just wondering about this.. Thanks. :-)


Gold Member
Username: Southernrebel

Monroe, Louisiana USA

Post Number: 1865
Registered: Mar-04
here is how adding subs works....

say you have 500wrms (ex: jl 500/1) and 1 500w sub, and your SPL is 135dB (generic #'s).

-if you add another identical sub and each sub gets 250wrms, this system will theoretically be +3dB louder than the single sub system.
(this is because when you add another sub, your system becomes more efficient)

-if you have 2 identical subs and get a second amp (double the power), you will see a +6dB gain over the 1 sub-1 amp system.


Silver Member
Username: Fandim

Reno, Nevada United State...

Post Number: 596
Registered: Jun-05
Ahh, ok. Thanks Marshall, read someone here post recently that it was a 3dB gain adding a second sub only if you gave it the same amount of power.. Didnt think that was correct, but had me confused for a second.

Thanks Marshall.

Silver Member
Username: Fandim

Reno, Nevada United State...

Post Number: 597
Registered: Jun-05

Was james post there that had me confused for a sec. Jonathan cleared it up tho as well.
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