Sub vs Cell Phone (cell phone wins)

[sjca35]

Ever since I swiched from Verizon (CDMA) to Cingular (GSM), my subwoofer has been picking up interference, even when the audio cable is removed. From what I can gather this is "normal".

Unfortunately, what doesn't seem normal is that I get interference even when the phone is on the other side of the room (10+ feet away). I'm not sure, but I'm guessing that due to the poor cell coverage I have at home, the phone (a Treo650) is increasing it's power to compensate and its enough for the subwoofer to pick up (even though I have a shielded cable). It seems that the internal electronics or powercable are picking up the signal.

Anyone know of a decent (say under $500 for an 8") subwoofer which is shielded? The only shielded subwoofers I've been able to find are for computer systems, not home theater. Or some trick to shield my subwoofer short of wrapping it in aluminum foil?

Unfortunately, switching back to Verizon isn't an option...

Thanks,
Aaron

 

[Rob Babcock]

What sub are you currently using?

 

[sjca35]

Cambridge Soundworks BassCube 8S.

http://www.cambridgesoundworks.com/store/category.cgi?category=spk_subwoofer&item=c1bc08se

-Aaron

 

[annunaki]

My SVS does not pick up the GSM interference, but my H/K receiver will from time to time. There really is not much you can do about it. If the phone gets bad reception at home, turn on call forwarding to your home, and shut it off.

 

[sjca35]

My SVS does not pick up the GSM interference, but my H/K receiver will from time to time. There really is not much you can do about it. If the phone gets bad reception at home, turn on call forwarding to your home, and shut it off.

Unfortunately, turning off the phone (or moving it into another room) really isn't an option.

-Aaron

 

[jcPanny]

Speaker shielding

From my experience, speakers and subs are "shielded" by adding a bucking magnet to the magnet of the woofer preventing excess EMI from radiating out from the enclosure and effecting a CRT monitor or other electronics. This will not prevent or reduce the sub's ability to pick up external noise from your cell phone.

That being the case, the Onix X-sub and HSU STF-1 are good 8" subwoofers for $200 and $300 respectively. They sould both outperform your current sub. Both companies have good trial and return policies so you should be able to send it back if you have problems with the cell phone noise.

A power center with filtering capabilities and a better sub cable might also help reduce or eliminate the noise problem.

 

[silversurfer]

My Cingular phone interferes with a lot of stuff in close proximity.....like my desk phone at the office, my car stereo, PC speakers.....

 

[jonnythan]

Cingular phones are the only ones I've ever see that do that. It drives me nuts when on a videoconference or conference call or something.

 

[mtrycrafts]

Unfortunately, turning off the phone (or moving it into another room) really isn't an option.

-Aaron

Before you buy a new sub, or go to that trouble of trying one out, buy an RG-6/59 type video cable as a sub cable. You can add an F connector to RCA for not much and no DIY involved. An inexpensive experiment.

 

[jonnythan]

"my subwoofer has been picking up interference, even when the audio cable is removed."

 

[mtrycrafts]

"my subwoofer has been picking up interference, even when the audio cable is removed."

Yes, but would it pick it up with a shorting RCA plug? I bet not.
So, perhaps a better shielded cable, perhaps that RG type would block it.

 

[sjca35]

From my experience, speakers and subs are "shielded" by adding a bucking magnet to the magnet of the woofer preventing excess EMI from radiating out from the enclosure and effecting a CRT monitor or other electronics. This will not prevent or reduce the sub's ability to pick up external noise from your cell phone.

That being the case, the Onix X-sub and HSU STF-1 are good 8" subwoofers for $200 and $300 respectively. They sould both outperform your current sub. Both companies have good trial and return policies so you should be able to send it back if you have problems with the cell phone noise.

A power center with filtering capabilities and a better sub cable might also help reduce or eliminate the noise problem.

Good to know. I'd be curious to know if anyone has either of those subs (or any other 8" sub) and a GSM phone and not experiance interference. Return policies are nice, but I'd rather have at least some anecdotal evidence that it might solve my problem.

I'm curious why you think a better sub cable or filtering power center might help too? The problem seems to happen w/o the sub cable attached, and my research indicated that filtered power wouldn't help since there are plenty of electronics inside the sub to pick up the GSM signal.

Thanks,
Aaron

 

[sjca35]

Yes, but would it pick it up with a shorting RCA plug? I bet not.
So, perhaps a better shielded cable, perhaps that RG type would block it.

So you're saying if the problem goes away with the shorted plug then I need a "better" shielded cable? Assuming that works, what would you recommend? I'm not sure I could pick a "RG type" if it jumped out of the packaging and bit me. Currently I have a monster cable (yeah, i know, over priced for what you get, but it's all the store had).

Thanks,
Aaron

 

[mtrycrafts]

So you're saying if the problem goes away with the shorted plug then I need a "better" shielded cable? Assuming that works, what would you recommend? I'm not sure I could pick a "RG type" if it jumped out of the packaging and bit me. Currently I have a monster cable (yeah, i know, over priced for what you get, but it's all the store had).

Thanks,
Aaron

I would say yes, to the shorting plug, not just a cap over the input. But I wouldn't test that first unless you had one left over from something.

RG 6 or RG59 cables are what you see on Cable TV from the wall to the set.

Premade comes with F type connectors, ones that screw on. There are adapters to make it into RCA ends, not expensive. This whole thing should be relatively inexpensive. Does that Monster not block the interference?

 

[sjca35]

I would say yes, to the shorting plug, not just a cap over the input. But I wouldn't test that first unless you had one left over from something.

RG 6 or RG59 cables are what you see on Cable TV from the wall to the set.

Premade comes with F type connectors, ones that screw on. There are adapters to make it into RCA ends, not expensive. This whole thing should be relatively inexpensive. Does that Monster not block the interference?

Yes, the monster cable is shielded. As I said earlier, the problem also occurs when the audio cable is disconnected from the subwoofer. It seems that the sub is picking up the interference from either the powercable or internal electronics.

 

[mtrycrafts]

Yes, the monster cable is shielded. As I said earlier, the problem also occurs when the audio cable is disconnected from the subwoofer. It seems that the sub is picking up the interference from either the powercable or internal electronics.

A disconnected interconnect still leaves wires and leads on the other side of it, inside the unit where the signal gets a piggy-back ride and boom, it interferes That is why I mentioned a shorting plug so that could not happen. If it still does, it has another pathway for sure.
I doubt the power line would do it as the amp should have proper filtration?

 

[markdi]

some sub plate amps have a enclosure that has 5 wood panels(your sub enclosure)and 1 metal plate.

I would make a faradays cage style shield and connect it directly to the shield of the rca cable(using a fine mesh screen material if airflow is needed)

then I would build a cable that would better use the stray signal immunity of the differential input of the amp.

- what wavelengths/frequencys do cell phones transmit on these days.

put rf bypass caps and chokes on the power cord and on both ends of the rca cable and the wires to the sub driver

if this did not work then I would use my tektronics tds 794d scope to find the semiconductor picking up the signal and mod/fix the amp.

my car stereo(600 watts rms - installed in 1993 still works great)had tons of ignition and alternator noise.
I tried a lot of things to solve my noise problem such as isolating amplifing and inverting the noise signal 180 degrees then mixing it back into the input amps - this worked pretty good but I wanted better than 110db snr.
next I built a circuit - a little amp that amplified the signal(12 volts peak to peak at full volume) then I modded the input amplifiers - lowered their gain - problem solved.

 

[majorloser]

My Cingular phone interferes with a lot of stuff in close proximity.....like my desk phone at the office, my car stereo, PC speakers.....

My Nextel does the same crap. Can't leave it near my computer speakers or near the dashboard in the car.

My Verison phone............no problem. And it even has service that works!

 

[Mark Seaton]

Cingular phones are the only ones I've ever see that do that. It drives me nuts when on a videoconference or conference call or something.

This is a well known problem in the pro-audio install world and one that is dealt with regularly in videoconferencing. Nextels and Blackberry's are also some bad offenders. The problem can often come down to internal wiring. In video conferencing systems the worst culprit is often the microphones and few inches of wiring between the actual mic capsule and the connector. Inside a subwoofer is problem the same deal, where most plate amps, especially cheap ones, are on an open plate and probably have plenty of areas with non-twisted or shielded cable there to work as a nice little antenna.

If you are getting a noise without the cable plugged in, I would first check grounding on the outlet you are plugged into, and then maybe try the shorting plug idea, but I suspect you'll need to find another subwoofer to solve the problem.

 

[Josuah]

I helped my friend set up a Hsu STF-2, I have a Velodyne SPL-1200II and two SVS 16-46PC+ subs, and have never had any problems with my Cingular GSM phone interfering with any of them.

My phone also does not interfere with the crappy Cambridge Soundworks "subwoofer" I have on my computer.