Sun, 6:50 am. I can hear my subwoofer. This puts a weed up my arse.

[wgscott]

Wife and (some of the) kids just left, and peace has returned to our abode. I can hear the dog breathing, the refrigerator (when it comes on), and the subwoofer. It is a Rel R218. It is the second one; the first one they eventually agreed to replace as it was a lemon, so I am reluctant to mess around with this again, but this irks me.

 

Briefly, I can unplug all connections to it, and lift the ground (temporarily, for testing purposes only), and it makes NO difference, so I believe I have ruled out ground loops. (I've heard a ground loop (60 Hz here) with this thing before, and this doesn't sound the same.) This is a very quiet but pervasive buzz. I can't hear it with the music on, even very soft piano music. I don't think it goes away, but the point is that it isn't loud enough to interfere. Nonetheless, it bothers me. The only way to quiet it completely is to turn off the power.

 

I've tried putting it behind a brick wall power filter/surge protector. I've turned off EVERY other circuit in the house, simultaneously. I've turned off solar panels (also, the quiet buzz persists in the absence of sun).

 

I'm concluding that this is just inherent to the built-in amp, and that I should have gotten a better sub. I have a velodyne microvee at work that doesn't do this when I bring it home and plug it in on the same circuit.

 

Is there anything to do apart from just sucking it up?

[Speedskater]

So with the AC power plugged in but no interconnect cables it hums?

That eliminates ground loops.

For other subs that need an audio signal to turn on, use a battery powered music source.

You might make an RCA shorting plug. Take a junk interconnect, cut it to about 6 inches and just twist the wires together.

Or you might take it to a friend's house in a different neighborhood and try it there.

[wgscott]

Wrong measurement [deleted]

[wgscott]

So with the AC power plugged in but no interconnect cables it hums?

 

Yes.

 

That eliminates ground loops.

 

That's what I thought. I get it even if I lift the ground.

 

For other subs that need an audio signal to turn on, use a battery powered music source.

You might make an RCA shorting plug. Take a junk interconnect, cut it to about 6 inches and just twist the wires together.

Or you might take it to a friend's house in a different neighborhood and try it there.

 

Yeah. Or I can take it to work, since I don't have any friends (apart from those who don't have electricity).

 

This isn't an automatic turn-on or automatic anything sub. All it has is an on-off toggle switch. I leave it on. Hence the irritation. I can only hear it when the audio is off.

[wgscott]

[deleted]

[elcorso]

Please try it with a cheater plug (ground bypass).

 

If this doesn't solve the problem, invert the AC polarity, still with the cheater plug installed.

 

If both suggestions didn't work you need to go to some technician to repair it, there could some leaking cap inside.

 

Roch

[psp]

+1 on the cheater plug, the sub input must be shorted. No worries unless it STILL buzzes with shorted input.

[tranz]

I have heard this too on some subs, and it is frustrating. Some are 'designed' this way, and I have noticed it more with Class D subs. For my Rel I have had to unplug the LED lights within to drop the noise.

 

If it was not happening before than perhaps a loose wire inside or a noisy source on the AC.

 

1. Any fans or AC running? Have you tried with the fridge off? Have you installed any of those new power saving LED lights...these are insanely noisy due to the switching power supplies in them. Any dimmer switches being used? These can be in a different AC circuit in the house and still have an impact.

 

Try turning off all other AC circuits using the breaker box switches. Then turn on the Sub as the only thing powered up. And slowely add power to other components.

 

2. You could try unscrewing the backplate and (gently) check and tighten some of the little wire clamps inside. Or unplug the LED one.

[new_media]

I just want to know how you get the wife and kids out of the house at 6:50 AM on a Sunday.

 

All I hear is the TV, the mixer, and someone yelling at me to go water the hydrangeas.

[Jud]

Probably a hum from the transformer in the built-in amp.

[4est]

This is possible, DC on the mains perhaps? Is the hum from the driver or the case? You might even feel it on the cone fwiw.

Probably a hum from the transformer in the built-in amp.

[InfernoSTi]

If it was not happening before than perhaps a loose wire inside or a noisy source on the AC.

 

This seems the most important point: if it changed recently, then something has changed that isn't inherent in the design. That could be internal or external, I suppose. But if you rule out the external as you seem to be doing, that means something that was fine is now not fine. That sounds like a warranty issue to me...

 

John

[wgscott]

Please try it with a cheater plug (ground bypass).

 

I did.

Briefly, I can unplug all connections to it, and lift the ground (temporarily, for testing purposes only), and it makes NO difference,

 

If this doesn't solve the problem, invert the AC polarity, still with the cheater plug installed.

 

I haven't tried that, but will next.

 

If both suggestions didn't work you need to go to some technician to repair it, there could some leaking cap inside.

 

Roch

 

Uh-oh.

[wgscott]

+1 on the cheater plug, the sub input must be shorted. No worries unless it STILL buzzes with shorted input.

 

What do you mean by "shorted"? In any case, it still makes the noise if I unplug everything and lift the ground with a cheater plug.

[wgscott]

I have heard this too on some subs, and it is frustrating. Some are 'designed' this way, and I have noticed it more with Class D subs. For my Rel I have had to unplug the LED lights within to drop the noise.

 

That's a great idea. The LED bugs me. I have a piece of electrical tape over it.

 

If it was not happening before than perhaps a loose wire inside or a noisy source on the AC.

 

It has been like that from day 1, as was the previous one (until it stopped working completely).

 

1. Any fans or AC running? Have you tried with the fridge off? Have you installed any of those new power saving LED lights...these are insanely noisy due to the switching power supplies in them. Any dimmer switches being used? These can be in a different AC circuit in the house and still have an impact.

 

All of the above, BUT it persists if I turn off every other circuit in the house and turn off everything on the remaining circuit except the sub.

 

Try turning off all other AC circuits using the breaker box switches. Then turn on the Sub as the only thing powered up. And slowely add power to other components.

(I did.)

 

2. You could try unscrewing the backplate and (gently) check and tighten some of the little wire clamps inside. Or unplug the LED one.

I am currently taking some testosterone supplements in preparation.

[wgscott]

I just want to know how you get the wife and kids out of the house at 6:50 AM on a Sunday.

 

All I hear is the TV, the mixer, and someone yelling at me to go water the hydrangeas.

 

Grateful Dead bootlegs.

[wgscott]

Probably a hum from the transformer in the built-in amp.

 

Unfortunately, I think you are right. I cannot feel it on the speaker.

[wgscott]

This is possible, DC on the mains perhaps? Is the hum from the driver or the case? You might even feel it on the cone fwiw.

 

I can't feel it on the driver/cone. But absence of evidence isn't evidence of absence. I can't seem to measure it.

 

I am embarrassed to admit I have no clue how to detect DC on the mains, or what to do about it.

[wgscott]

This seems the most important point: if it changed recently, then something has changed that isn't inherent in the design. That could be internal or external, I suppose. But if you rule out the external as you seem to be doing, that means something that was fine is now not fine. That sounds like a warranty issue to me...

 

John

 

It has been like this since day 1, as was the previous sub, for which this was a warranty replacement. Given the ordeal Rel put me through the first time, I would rather stick a treble fish hook through my eyeball and sprinkle salt into the wound than go through their warranty claim torture again. I wish I had just gotten my money back on this thing.

[InfernoSTi]

I'm sorry, that kinda sucks. Sounds like you have some ideas on the cause but that leaves you with the fact that you might perhaps find the cause yet have not good solution. When you find products that don't have irritating faults, it is stuff like this that makes you appreciate them even more.

 

Again, sorry for the hum, that is a reasonable thing to irritate you...all of us would reach our limit at some point.

 

John

[sandyk]

Have you tried it with an RCA plug at the input that has a short circuit across it, and no cable connected ?

 

Regarding internal LED indicators . Unlike external LED lighting with cheap and nasty switched mode power, normal indicator LEDs are quiet devices , and may even be used as low noise voltage references. The problem arises when they are connected right at the output of the power supply before additional smoothing. The LED wiring should be routed away from sensitive areas of any design.

[wgscott]

Have you tried it with an RCA plug at the input that has a short circuit across it, and no cable connected ?

 

No. Isn't that dangerous (for the sub)? Also, it has two RCA inputs and a speaker-level input. Is doing this on one sufficient?

 

Regarding internal LED indicators . Unlike external LED lighting with cheap and nasty switched mode power, normal indicator LEDs are quiet devices , and may even be used as low noise voltage references. The problem arises when they are connected right at the output of the power supply before additional smoothing. The LED wiring should be routed away from sensitive areas of any design.

I don't know which it is.

[sandyk]

No. Isn't that dangerous (for the sub)? Also, it has two RCA inputs and a speaker-level input. Is doing this on one sufficient?

 

I would expect the inputs to the amplifier to be capacitor coupled. Try it with 2 shorted RCA plugs, or with a resistor of say 1Kohm mounted across them. on your normally used inputs, but don't switch on power until after they have been inserted. This should give you some idea as to whether the noise is internal or externally caused.

If the lack of a LED indicator doesn't bother you, then it's easier to leave it unplugged.

[Jud]

Unfortunately, I think you are right. I cannot feel it on the speaker.

 

Any idea where the amp/transformer is located? Try putting your hand/ear on various parts of the enclosure to see if you can localize it.

[beanbag]

To short the input is very simple. Hook a short RCA cable up to the inputs, and then on the other end of the cable, use a metal object to touch the inner pin to the outer. The noise should go down by half if you have both R and L inputs.

 

No, the stupid LED circuit isn't going to affect things.

 

To check for DC on the mains, use a voltmeter in DC mode.

 

Otherwise, you have to go inside the box and start poking around. For example use the AC mode on the voltmeter to measure any signals across the woofer wires.

 

If this sounds scary, I suggest you take this sub to work and have a grad student look at it. Some of them might have good electro-mechanical aptitude.