I posted this in the Cap S thread but thought I could benefit from the collective wisdom in this thread..
I have two JTR Cap S subs that are installed in a baffle wall. They feed into a custom Sub Eq and the Sub Eq feeds into an Onkyo PR-SC885 SSP.
The right hand side sub stopped working and Jeff replaced the amp and returned the Cap S back to me last Friday.
Two issues though..
1) The returned Cap S (right hand side) sub has a low frequency hum. Left hand (original) Cap S sub no hum. The hum is audible directly in front of the 18" driver. It is most noticeable when you are close and directly in front of sub. From 10+ feet away it is less noticeable but you can still faintly hear the low frequency hum that almost sounds like a dryer machine is running in the next room. No hum when power off. I also performed the following troubleshooting steps ,
1a) Instead of the same surge protector used by other Cap S sub, I plugged in suspect Cap S direct to the same outlet circuit No difference.
1b) From the Sub Eq box , i swapped Subs to opposite XLR outputs. No difference.
1c) From the Sub Eq Box, I put in one sub at a time and tried both XLR outputs. No difference. Meaning left hand sub by itself had no hum but right hand sub by itself had hum.
1d) Now this is where it got interesting. I removed the Sub Eq box from the equation by plugging in XLR of the right hand Cap S sub directly to the Onkyo SSP. I expected there to be hum but there was *none* ! I tried test tone to make sure Cap S sub worked and it did.
My acoustician / installer who made the Sub Eq for me thinks there is a system interaction causing ground loop issue occurring between the Cap S with the new replacement amp and the Sub Eq.
I also noticed the back panel of the Cap S amp has slightly different markings than the original. There might be some revision changes to the amplifier compared to my original Cap S amp?
I called Jeff last week and left him voicemail but did not hear back yet.
2) Today myacoustician / installer re-measured and the frequency response looks quite different. The green curve is the left (and original) Cap S. The black curve is the Cap S with replacement amp.
The acoustician tried to Eq the gaps out but it made the sound a little worse (overall sound was a bit flat) and decided to back off. His feedback is that it's like I have two different subs now. His suspicion is that it is a DSP profile is different with the new amp. With the above said, the overall sound now is not bad at all. But the the fact that I know the response curves are so different does bother me because both subs are not operating as best as they could be. I called Jeff today again, left him a voicemail and sent him an email with the above but have not heard back yet. I was not too happy that I had to send back the Cap S sub the first time on my own dime and I really don't want to have to send it back again.
What would you guys do at this point?