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Different subs in pairs?

Okay - here's a question that I haven't seen addressed elsewhere. I have a medium to largish room with pretty nice in-walls (a remodel removed my listening space and floorstanders). I am using an REL Britannia B3 as a sub, and while it's very musical and integrates well, I've got two problems. One is that I'm picking up fm over their high level connection. I didn't have that problem until I placed the sub in a better spot and had to stretch out the 3 wire hi level connection which made a nice antenna. Secondly, I want to try to address some room nodes and believe that 2 subs instead of 1 might help me balance things out. I don't need more bass, I need more even bass.

I doubt I'll find another B3 - so I am considering REL's new S3 which has wireless built in (the best connection according to the factory) which would help me address problem 1 - the fm bleed through.

My question: Anyone see a big problem in pairing an REL S3 (or S2) hooked up through their wireless system in the left channel and the Brittania B3 hooked up hi level directly in the right channel? Same signal, routed differently. Two subs w/ essentially the same voice. I think. I'm past worrying about imaging as I'm working with in-walls. And, given the input flexibility, I think I can get each sub to work smoothly with it's respective channel.

I know it's an odd idea, but I like the B3. If not, you'll see it for sale here shortly because I have to do something to fix the two problems I'm having.

Another option is just buy a less expensive pair of subs like the Martin Logan Dynamo 1000Ws or 700Ws which have wireless built in.

Any wisdom to share?
mgrif104
almarg's avatar
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almarg
9,670 posts
 
It might be best to ask REL about whether timing issues would be a concern in the scenario you are envisioning.

Regarding the radio station interference, I suspect that could be eliminated (with no audible side-effects) by putting an inexpensive ferrite clamp around the wires from the existing sub, probably at a point near where they are connected to the amplifier.

I would suggest that you take a look at the ferrite clamps listed here, and select one having an appropriate inner diameter.

If you can hear intelligible audio from the radio station, I suspect that it is AM and not FM which is being picked up, in which case you would want to select from among those listed under the "Low Frequency 200 kHz - 30 MHz" tab on the page I linked to. If the interference is other than intelligible audio, and/or you somehow feel fairly certain that it is indeed FM, select from among those listed under the "Lower and Broadband 1-300 MHz" tab. Or perhaps buy one from each category, and try both.

Assuming that the interference is being heard from your main speakers, and not the sub, I'm envisioning that the radio signal is being injected into the feedback loop of your amplifier, and its AM content is being demodulated as a result of non-linearities in the amp. Which is why I suggest putting the clamp near the amp end of the cable.

Good luck. Regards,
-- Al
zd542
5,339 posts
 
"If you can hear intelligible audio from the radio station, I suspect that it is AM and not FM which is being picked up, in which case you would want to select from among those listed under the "Low Frequency 200 kHz - 30 MHz" tab on the page I linked to. If the interference is other than intelligible audio, and/or you somehow feel fairly certain that it is indeed FM, select from among those listed under the "Lower and Broadband 1-300 MHz" tab. Or perhaps buy one from each category, and try both."

Well, he did say the sub is musical. They do play a lot more music on FM stations.
almarg's avatar
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almarg
9,670 posts
 

:-)

But seriously, the reason for my comment is that I don't see how his amplifier, or the amplifier in the sub, could be extracting music (or any other intelligible audio) from an FM signal.

Best,
-- Al
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swampwalker
5,138 posts
 
If you were going to run two mono subs, then they could be different without, it seems to me, too much concern. If I was running mono subs (which in a way I am) I would want them to be identical for several reasons, not the least of which would be that if you want to even out room modes by having them in different places, you would (I think) want to make sure you are not introducing a second, different set of modes. But I'm no acoustician or speaker designer. Other reasons might include different crossover slope and/or execution, different frequency response, different absolute phase, different interaction with input device (espl if being driven from your amp) Maybe Duke, our resident guru in that area, will chime in. I know he has a multi-sub system that he sells that has identical subs.
mgrif104 OP
351 posts
 
Thanks for the feedback, folks. I only get the radio interfrence through the sub, not the mains. And, I only got it when I moved the sub farther away from my rig such that the cable connecting it was stretched out making an antenna. I've no idea if it's AM or FM, but I'll try the ferrite clamp. Then again, if I do combine one as wireless and the other direct hi level, I can go back to a short length of cable for the one near my rig. Probably still worth getting the clamps.

I'll also ask REL about any timing issues, but given that they have three systems of hooking up a sub, wireless, hi level and LFE, it seems that latency shouldn't be an issue.

Quick update - just picked up a pair of Martin Logan Dynamos to audition at home w/ their wireless system and, of course, the only inputs are RCA into the sub - no hi pass return or full return to the preamp. Given that I'm using a stereo preamp (no 2.1), and that the subs can't take a high level input, I can't use them.

I don't feel like also buying a new preamp. Frankly, I like listening to music, not playing with gear. Looks like ferrite clamps and perhaps an S/3 wireless.
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