This is topic ultimate question about subwoofers and power amps required: in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by David Baum (Member # 568) on 05-13-2001, 12:50 PM:
we'be been discussin deeply the various aspects of amp power, nr of subwoofer as a function of sensitivity, room length etc.
As a reminder here is the chart from Dolby 1994 note:Now, the amount of watts required for the SYSTEM ( based on its sensitivity )
CLICK HERE
So, let's take a room length of 15meters for a small sized theater. Dolby says it requires a total of 1600w ( minimum, for the entire subwoofer system). Let's say we use 4 4645C subwoofers, that would say each should receive:
1. 400w minimum
2. 400 REAL watts, thus something like 600w from a class AB (efficiency of about 65%). do you take into account this factor? or the H or G class factor, which has higher efficiency ?
3. 800w from an amp, too allow 3dB of headroom ? (!!)
4. run the amps in bridged mode to increase the efficiency. let's say 2 amps rated at 2x450 each but run in parallel to feed the 4 subwoofers ( providing the amps can go as low as 2ohms without problem )
5. 1600w per woofer, to allow 6dB of headroom but with the gain knob turned 2/3 of the way for instance (in this case, bridged amps and $$ factor is ... no more a factor 
)
6. what's your position on the clip limiters, since they can double the watts feeding the subwoofers ? a 2x300w amp could thus become a 2x500 or 600w amp.
Well, thanks for any comment. Btw, did you try to replace the internal wires of the subwoofers with beefier, say AWG 6 or 8, wires ? would it change anything ?