Any way to stop sub-woofer hum? What speakers do not hum?

davidstone28 · Post by **davidstone28** » Wed Jan 05, 2005 4:32 pm

The sub-woofer of my TDK S80 speakers makes a very noticeably hum when turned on.

Is there anyway to remove this hum?

If not, do all sub-woofers hum? What subwoofers don't hum?

hofffam · Post by **hofffam** » Wed Jan 05, 2005 6:57 pm

Hum is not normal for subwoofers (nor any other audio equipment). Most hum is related to the power line frequency (60 hertz in the US). Hum occurs when the power line intrudes into the amplification circuitry. It could be simply poor design (like cheap equipment), cables with a broken shield, or a defect.

wooglin · Post by **wooglin** » Wed Jan 05, 2005 7:53 pm

Worse than the quality of the power coming in through your mains, the hum is likely more a result of EMI from surrounding equipment. Whenever I put my cell phone or blackberry next to my speakers I get audibles.

If you can't eliminate the EMI, you may want to try a shielded cable between your PC and the speaker/amp.

davidstone28 · Post by **davidstone28** » Wed Jan 05, 2005 8:17 pm

It still hums even if I have it on the floor underneath my (wooden) desk

chiahaochang · Post by **chiahaochang** » Wed Jan 05, 2005 9:12 pm

I noticed my previous speakers hummed a lot when I had them plugged into a battery powered outlet of my UPS. I moved the plug to a seperate surge protector and it quieted down. So, if you've got it plugged into a UPS, you may want to try a different outlet/powerstrip.

sthayashi · Post by **sthayashi** » Wed Jan 05, 2005 10:56 pm

I was going to tell you to try using a cheater plug, but I just realized you're in the UK and may not have a cheater plug.

On a North American outlet, there's three holes: Hot, Neutral, and Ground. A cheater plug takes a plug designed for all three, and removes the ground part.

My subwoofer manufacturer, Hsu, recommends doing this for their subwoofers. I don't know if you can do something similar in the UK.

Alternatively, you could try running type of wire from a metal part of the subwoofer to the chassis of your computer or amplifier. I've done this when I created a ground loop between my amplifier and two computers, and it works.

Here's a site that goes into more details.

Rusk · Post by **Rusk** » Wed Jan 05, 2005 11:41 pm

I agree with what sthayashi said.

Also, flouresecent lights can cause hum. And, you might try moving your subwoofer away from the back wall a bit. That might help.

Most of the built-in amplifiers in these subwoofers are PWM, or pulse width modulating, amplifiers. That is essentially what computers do. That makes them more susecptible to interference from computers. They use this type of amlifier because it is very efficient and inexpensive.

I agree with sthayashi's suggestion that you try to eliminate the ground. But I don't know if you can do that in Britain. I'm not familier with British mains. In the US we have two types of plugs: those with two prongs (without a ground) and those with three prongs (with a ground). With an adapter that sthayashi mentioned, you plug a three prong plug into it and it only puts out two prongs, which you plug into your mains. They are very inexpensive. But like sthayahsi said, I don't know if you can do that in Britian or not.

You might try a conditioning surge protector from Monster Cable. I don't know if Britain has Radio Shacks--I believe it does--carries them, as well as other places.

I know those speakers were well-received in the UK publication Hi-Fi World. Do you like their sound?

Anyway, let us know how you are doing with your problem.

Regards

meglamaniac · Post by **meglamaniac** » Thu Jan 06, 2005 1:13 am

Does it hum if you unplug it from the computer, leaving it powered on but with no audio connection?

As for removing the ground, to my knowledge there is nothing on sale in the UK like cheater plugs. We have had earthed power since fairly early in the last centuary, and it is illegal to install unearthed power sockets or systems, and anyone doing so is also liable for any death or injury their installation causes.
For the second reason more than the first, it is highly unlikely such a plug would be sold even if it was not classed as illegal.

However, the sub looks to be plastic cased to me, so in all probability the earth pin on the plug will not be connected. While power systems are legally required to be earthed, sheilded equipment such as plastic cased kettles etc can be left unearthed as there is no possible risk of shock, and all new buildings are required to have trip switches installed instead of fuse boxes so it's pretty much impossible to electrocute yourself anyway.

Easiest way to find out: assuming you're okay with doing so, open the plug and have a look.

CoolGav · Post by **CoolGav** » Thu Jan 06, 2005 1:49 am

Could be a ground loop, so rather than removing the earth connection to the mains, solder in a resistor (10k) on the "ground" of the incoming signal. Alternativly use a DI box with a ground lift or plug the subwoofer into the same power block as whatever it's being fed the audio from.

Tyrdium · Post by **Tyrdium** » Thu Jan 06, 2005 1:50 pm

You know, if you wanted to build your own cheater plug, you could probably just buy an extension cord and lop off the ground pin...

greeef · Post by **greeef** » Thu Jan 06, 2005 7:04 pm

Make sure none of your audio cables are running parallel to any power cables for a start - only cross at 90 degrees.

ddrueding1 · Post by **ddrueding1** » Thu Jan 06, 2005 9:18 pm

Tyrdium wrote:You know, if you wanted to build your own cheater plug, you could probably just buy an extension cord and lop off the ground pin...

Seconded. I do this quite a bit in the US...just grap the ground ping and rip itoff with pliers.

meglamaniac · Post by **meglamaniac** » Fri Jan 07, 2005 1:19 am

Tyrdium wrote:You know, if you wanted to build your own cheater plug, you could probably just buy an extension cord and lop off the ground pin...

Nice try, but no cigar I'm afraid!
UK power sockets are gated - the earth pin is slightly longer and goes in first, releasing the locks on the other two holes. This is to stop kids sticking fingers/objects/etc in any hole but the safe earth, and also just for general safety.
So it's actually physically impossible to insert a plug with no earth pin unless you modify the socket.

Numbers · Post by **Numbers** » Fri Jan 07, 2005 6:24 am

OK, that whole power line & speaker line thing.... It's true in only about 1% of the cases. You can run power lines and speaker lines together and not have any noise, trust me, I've done car audio for years. It's basically a VERY rare instance that turned into superstition, then techno-bullshit.

Anyways, I'm going to ask a simple question, because nobody else has... is there a gain control knob on the sub? You might need to turn it down a bit, if there is one. That should cure the hum. Also, try disconnecting it from the computer and seeing if the hum is there. If it still is after both of these tests, you have a faulty product.

Lwood · Post by **Lwood** » Fri Jan 07, 2005 7:26 am

I have heard that switching to an external sound card, such as the Soundblaster Extigy or some of the new Soundblaster Audigy products can be very effective because it removes all sound circuitry from the EMI mess inside a case. I can't remember my source on this, so don't go buying one of these products looking for a magic bullet, but it might be something to consider if easily available.

nosferatu · Post by **nosferatu** » Fri Jan 07, 2005 7:42 am

This sounds like the problem I (still) have with my Klipsch sub. Does the power cord go directly from your power outlet into the sub? If so it could very well be the power transformer. I am going to modify my sub so the transformer will be taken out of the housing of the sub.

I never had humming with my creative labs set, but that has a separate power supply i.e. 230v from the wall to the PS and then I, I assume, 12v to the sub.
As a test, I placed the sub on top of the power supply and it resulted in the same humming sound as my Klipsch sub.
I hope this is not cause of your problem, because if it is, you will have to sacrifice your warranty to solve it.