This is why the SVS has a volume control! The "maximum" volume is 0 which means that 0.75V will drive it to full power. If you set the volume to -10dB, it will attenuate the input signal by 10dB which means you now need 0.75V/(1-0.32) ~ 1.1v to drive it to full power. If you sent the attenuation at -20dB, you would need 0.75V/( (1-0.32)^2) ~ 1.6v to drive it to full power. Et cetera. This is why, when you set things up, you have to "level" the subwoofer (set the volume). Start with a volume of like -30dB and then bring it up until its loud enough, not the other way around (unless you hate your neighbors).OK, so my two cases are:
A90 via XLR -> first sub -> second sub -> speaker amp
A90 via XLR -> speaker amp
A90 via RCA -> first sub -> second sub
In that case multiple subs need more power than one sub. I was wrong about "taking a copy". Yes it sounds obvious but I thought it was possible it worked differently. The output on the sub is the remains of the input.
Interesting, I didn't know subwoofers' input sensitivity was so low.
Forgive a newbie question:
My power amp has an input sensitivity of 4.0V. I need to supply more voltage to the power amp, so how do I know I won't supply too much to the subwoofers (more than 0.75V for SVS)? In both cases at the top of this reply.
I know I won't exceed 4.0V on the power amp because it would be extremely loud (I'm probably getting 2x JBL LSR6332), and I could measure the voltage with a voltmeter if I really wanted to (I have done this in the past with a preamp that has a lot of headroom).
To make an extreme example, suppose I supplied 3V to power amp and I have just one sub. That means in the second case above, surely the sub will be receiving 1.5V, which is too high.
The volume control on an SVS subwoofer is actually a variable gain control not an input attenuator so my example above is not completely accurate but good enough if you don't want to read more. Amplifiers multiply the voltage. So with the volume turned down, the input voltage is multiplied less before its sent to the speaker. Putting 4V into the SVS (with the volume turned down) won't hurt it one bit. I can't find a spec for maximum input voltage (with the gain set correctly) so it can probably handle as much as really high-end preamps put out (in the 10 volt range). On the other hand if you put 4V into it at maximum volume the output would be a painfully loud, distorted mess, that would risk damaging the speaker if it weren't for the built-in protection mechanisms. (Don't try this at home).
I may have over-explained that. The input sensitivity is 0.75V *at maximum volume*. It's higher at lower volumes. Again the key to almost all things in audio is that almost all devices can put out more voltage than the next device in the chain can accept at full rated power. It sounds scary but its not. It's actually necessary for good audio fidelity. There are built-in protection mechanisms so that minor mishaps don't cause thousands of dollars of damage. But the *primary* protection mechanism is your ears. Start with things at low volume/low gain and turn them up slowly. If you can hear audible distortion, turn it back down. That solves pretty much every voltage issue imaginable as long as you aren't using insanely incmpatible equipment combinations.