I just purchased a pair of DIY sealed Dayton 18's with an EP4000 amp. I have an older Denon avr that I'm using , I'm splitting the sub out and running to the amp, very low bass output, I've got the level on the avr sub out all the way up. I can turn the gains all the way up on the EP and still not a lot of bass. I then switched to an Onkyo avr, much better output. I believe the volts put out on the sub out from the Denon is very low, the Onkyo is better, but I'm still putting the gain all the way up on the EP most the time, no clipping though. Am I correct on the issue that it is the voltage? Any way to boost the signal. Thanks for any help. I am now a believer in the DIY route for subs, these are very good.