I'm trying to set up my new Sub and speakers. I've got a set of Polk RMS 10's and a Polk PSW 10. I'm running a Yamaha HTR 5750. I've got the crossover set to 100 hz in the AVR which I think is right for these speakers. I'm trying to set up the sub now am wondering what the difference between the volume control on the back of the sub and the level control in the AVR setup menu is. Which one should I adjust when using an SPL meter to balance speakers?

Thanks,

they both adjust the level of the signal (volume) going into your sub's amp. try 75% on both to start and then adjust both to match the other speakers. I like to leave the sub's input level a little high and then adjust the AVR's sub level with my harmony remote as needed. You wouldn't want one cranked and the other really low.

I would have to disagree with a 75% setting to start as a general rule. I set my preamp at 0 or just above that. So that would be flat, or at 50%, depending on how you look at it. Someone once advised me that for a THX receiver/preamp, it is optimized at 0. I just go a notch above that because I figure that with a high output voltage from the preamp, the sub's amp has an easier job of it.

I've read very technical reviews of preamps and receivers where they have tested the line level sub for output voltage at clipping. So that is an issue. Clipping = bad.

I set the amplifier's level as low as possible to reduce the distortion. I find that I rarely can get above 25% on the plate amp.

I imagine that some amps might function better turned up more than that. Can't imagine why. I notice that my Krell subwoofer's owners manual says to set it at a certain point, which I vaguely remember surprising me as being high.

I too would disagree with the 75% starting point. This seems generally too high. First, I would check the manual for your sub and see if the manufacturer has a recommended starting point for the level control on the sub amp. Start there. If there is no recommendation, start at about 25%. Then do a calibration of the sub and speakers. If the calibration yields a strongly positive setting, turn the sub amp up and repeat the calibration. Continue this process until you get a setting on the sub that yields a close to "0" dB setting on the receiver, (within about +/- 3). This will be appropriate to ensure that the sub comes on using the "Auto-on" feature, but that you're not over- or under-driving the sub amp.

Craig