[sonicxtc]

Hi,
Well, I bought a sub last night. An SVS 25-31CS PASSIVE sub.
Needing a subwoofer amp, I planned on ordering a plate amp. But, the sub seller had a psb subsonic II and offered the amp portion as a package deal. [He just didn't like the psb and planned to get rid of it.] Okay. I thought this will work fine.

Eastern electric pre-amp. It has TWO sets of RCA outputs. I hooked one pair of the RCA outputs to the sub-woofer inputs, the other runs to the amps feeding the main speakers. [Edit: The 2nd set of outputs feeds the main speakers; the 1st set feeds the subwoofer]. I turned on the pre-amp with all connected, but the main speaker amps OFF, just in case. Well, I can "hear" the sub making some rumbling sounds. The volume control on the sub is doing nothing; the low pass filter IS working as I can hear the pitch of the rumble change.

So, just to be clear: EE pre-amp RCA outputs to plate amp RCA inputs; plate amp speaker wires connected to passive sub.

Below is an image of the plate amp. Please advise on exactly how to connect all this. My main concern is damaging something.

Thank you. Sometimes it sucks being a newbie, but we all have to start somewhere. Amazing, I've been an audio dude for 30 years and never had a sub.

Thanks AC.

[medium jim]

Congratulation on you stepping up to the plate.  I've always found PSB to be more than helpful in the past (when I owned a pair of their speakers) and would contact them for advice or check on their website for wiring diagrams.

Or better yet, some of our technically inclined can take this by the horns and bring up some answers!

Jim

[medium jim]

Geez, there has to be someone who can help a fellow AC member.  Bonus points will be awarded.

Thanks,
Jim

[*Scotty*]

The input impedance on your main amplifier changes when it is turned off. The stated input impedance assumed that the amplifier is turned on. This may change the preamplifier's behavior when it tries to drive the load presented by the sub.
 Subs, when played alone basically kind of just rumble. Most music with the exception of organ music seldom presents a sub with a pure tone of a specific frequency. Much of the time a sub is reproducing the low frequency overtones of instruments whose fundamental frequencies are outside the bandpass of the sub-woofer. When you are listening to a sub-woofers output all by itself you won't really hear a complete audio waveform and the sound is not one that is encountered when listening to live acoustic music.
 
Here is a link to the sub-woofers owners manual in pdf doc form from the PSB website.
http://www.psbspeakers.com/content/111103153019-Subsonic_II_and_III_Owners_Manual.pdf
This should help.
I would power up the main amplifier and proceed to dial in the sub-woofer's level and crossover point. I would not plug and unplug the RCA cables with the sub-woofer plate amp powered up.
My SOP is to ALWAYS make all low level IC connections in and out of equipment as well as speaker connections, with all gear in a powered down condition.
 In addition if I am turning equipment off and on instead of leaving it powered up all the time, I ALWAYS observe a turn on sequence. Sources;CD,tuner,phono-stage, first. Next preamp and wait long enough for the circuitry to stabilize, perhaps as long as 2min. by the clock. Last to turn on is the power amp or amps.
Scotty

[sonicxtc]

Hi Scotty,

Thank you for the feedback. I just powered up everything...sequentially. AND, that's great advice.

All I hear is the "rumble." I flipped the phase switch and that makes it "louder." Sub woofer volume does not seem to impact the overall volume.

I also switched the outputs just to see if there's an issue with one set of pre amp outs, but both feed the main speakers just fine.

IF you were WIRING this from scratch, what would you do? Did I miswire something? I am going pre-amp output to the subsonic II "input from pre-amp," then plate amp's speaker wires ("internal" from the plate amp)  to the subwoofer.  Logically, I don't see another way to wire this, but obviously, I am missing something. EDIT: I've also swapped interconnects and power feeds.

 

Please advise. Thank you.

[*Scotty*]

So let me understand this. Everything is powered up,main amp and plate amp and there is no sound from the main speakers.
Scotty

[sonicxtc]

So let me understand this. Everything is powered up,main amp and plate amp and there is no sound from the main speakers.
Scotty

Hi, THANK YOU.
There's full sound from the main speakers. They are FINE. The subwoofer just produces a vague "rumble"-- you can "hear" the rumble, feel the downfiring sub driver moving and there's a top vent outputting "air."

[medium jim]

Sonic:

Stupid question, did you test the sub and plate amp before buying them? I'm assuming you did, if so how did you test the plate amp?  Was it wired to the sub you bought or to the PSB?

How are you wiring the speakers?  Are you wiring from the amp to the subs via the plate amp and then from there to the main speakers?  Or are you going to the sub via the preamp sub out?

Jim

[*Scotty*]

Okay, here's another stupid question, what do you expect the sub-woofer to add to the sound of the existing system? All sub-woofers more or less rumble along with the music. If they are rumbling and the sound they produce is disconnected from the rest of the spectrum reproduced by the main speakers there is some kind of integration problem.
Scotty

[medium jim]

*Scotty*

I think the term rumble is a bit harsh, I still think subs are musical for the most part.  I agree that it may be an integration issue and the gain needs to be dialed back to where it meets the roll off of the mains.

Sonic, do you have a SPL meter?  If so, a rather simple thing to do is to measure the SPL (sound pressure level) of the sub 3 feet away and then turn off the sub and measure the SPL of the mains at the same distance.

The sub should only be about 3db more than the mains as the starting point and then fine tune to taste from there.

Jim

[sonicxtc]

Sonic:

Stupid question, did you test the sub and plate amp before buying them? I'm assuming you did, if so how did you test the plate amp?  Was it wired to the sub you bought or to the PSB?

How are you wiring the speakers?  Are you wiring from the amp to the subs via the plate amp and then from there to the main speakers?  Or are you going to the sub via the preamp sub out?

Jim

Thanks Scotty and Jim.
I tested and heard the SVS sub at Chuck's house being powered by a receiver. It sounded great. It worked fine. Yes, it was musical and it integrated with the main speakers and sounded great.

Yes, the PSB sub worked fine, too. This is the very plate amp which powered the PSB sub. Chuck just removed the plate amp portion of the PSB sub. The plate amp has "built in" wires to feed from the amp to the driver.
WIRING. The wires run as follows. Pre-amp RCA outputs to plate amp RCA inputs marked "R/L input from pre-amp," then the "built in" speaker wires of the plate amp to the SVS sub's speaker connections.

Hope that answers your questions. So, when I say "rumble" I mean it is not music, it is not working properly. I KNOW it sounded great when set up properly at Chucks. Unfortunately, I did not have time to test the plate amp at his house. Just trying to diagnose the issue. THANKS.

I believe A) the wiring is incorrect or B) the plate amp is not working. I have every reason to believe the sub is fine. Granted the sub was transported on its side, but it was very well cushioned. 

Thanks. I await your input.

[medium jim]

Sonic:

Try the old school hook-up, wire the speakers from the amp to the sub using the push open speaker tabs on the subs and then to the mains.

If you have an integrated, run the speaker outs to the sub and then to the mains.

It's worth a try.

Jim

[*Scotty*]

This may sound like a dumb idea, but you might try to get Chuck to come over and trouble shoot the install. It is kind of hard to have the amp break between your house and his. It is also fairly simple to hook the amp up correctly. My only remaining idea is that perhaps there some kind of problem with the ICs you are using to connect the preamp to plate amp. It is also possible that for some unknown reason the plate amp is oscillating, which would produce the constant rumbling from the sub.
Other than this I have no idea what could be happening. Sorry.
Jim's idea might answer the question regarding the potential flakiness of the IC's.
Scotty

[JRace]

That amp does not have speaker level outputs for the mains.

[medium jim]

That amp does not have speaker level outputs for the mains.

Not necessary, if you wire old school as I suggested and as Scotty noted, it will also ferret out any bad IC's. 

I would also douche the rca inputs with contact cleaner....

The idea of the guy who sold them to you to suss out the problem is a good one. 

Jim

[medium jim]

Just another thought, is the speaker compatible with the plate amp, e.g., is the amp wired for a dual coil driver and the driver only a single coil? 

Jim

[sonicxtc]

Hi everyone. I updated the picture hoping to clarify everything. Any suggestions would be welcome. Thank you.

[DaveC113]

Sounds broken to me. Also, if your cutoff freq is too high it tends to integrate with the speakers worse. I use 50 Hz and recommend the lowest setting you can get away with without leaving a gap in the freq response.

Try putting on some House/Techno, and if the sub isn't filling out the boom-boom-boom of the steady bass notes you've got a problem.

[sonicxtc]

Sounds broken to me. Also, if your cutoff freq is too high it tends to integrate with the speakers worse. I use 50 Hz and recommend the lowest setting you can get away with without leaving a gap in the freq response.

Try putting on some House/Techno, and if the sub isn't filling out the boom-boom-boom of the steady bass notes you've got a problem.

The good news as of 60 seconds ago: The subwoofer itself it NOT broken. I brought it upstairs. I'm using it as the "left speaker" powered by an integrated amp. It plays music. So, it's EITHER the way I have it connected in the main stereo OR it's the plate amp itself.

Thanks for the reply Dave.

[DaveC113]

The good news as of 60 seconds ago: The subwoofer itself it NOT broken. I brought it upstairs. I'm using it as the "left speaker" powered by an integrated amp. It plays music. So, it's EITHER the way I have it connected in the main stereo OR it's the plate amp itself.

Thanks for the reply Dave.

Yeah, I meant the plate amp sounds broken, sorry for the confusion...