Probably addressed before - subwoofer hum

polkyman

I've got the RMS series 5.1 speaker system. The sound is great.. have no complaints. However, the sub makes a noticeable hum when I've shut everything down. One thing I have noticed is that the subwoofer stays on all the time because the light is always green. The switch in the back has 3 different settings. If the switch is all the way up, the sub is on. If it's all the way down, it's off and the light is red (and no hum is heard.) I don't know what placing the switch in the middle does. Shouldn't the sub power off when the receiver goes off? If so, how do I configure this? Moreover, how do I get rid of the hum? It was suggested to me that I not put the power cord in the same power surge protector that everything else is plugged into and just plug it directly into the wall. However when I tried that, the hum still occurred. I don't think I necessarily have a "bad" sub because from what I've read on this topic, it sounds pretty common. But lately I've been manually switching the sub off so that I don't hear the hum and it's getting tedious. Can anyone help?

Face

You pretty much answered your own question.

Go for the middle.

gvg45

I'm not familiar with your sub, however my sub has the same switch with 3 settings. UP=powered on always, Down=Power off, Middle=standby. The middle setting will power your sub on when your receiver sends a signal to it. When a signal is not sent to the sub for a period of time, the sub will power off.

One thing to mention, when you use the standby setting, be sure on your receiver that the 'subwoofer' output is not set too low otherwise the sub may not pick up the signal and turn on.

engtaz

Some have suggested a cheater plug. Your 3 prong plug from your sub into adapter with 2 prongs out. You have a ground loop problem most likely.

engtaz

Deadof_knight

rca replace the rca cable, with a nicer quality cable, I had the exact same problem with my velodyne at first. does it hum when you pull the rca's out .........if no then replace the rca's

use a different plug sepperate surge protector off of another circuit too

polkyman

My sub power cord only has 2 prongs. I tried turning the receiver on with the sub in standby mode but it didn't turn on with it. Guess I'll check the sub settings on the receiver. I have no rca cables plugged in the sub.. save for one.. a high quality single sub cable that goes from the sub to the back of the receiver.

gvg45

polkyman wrote: »

I tried turning the receiver on with the sub in standby mode but it didn't turn on with it. Guess I'll check the sub settings on the receiver.

Try to adjust your settings on your receiver for your subwoofer to 0db and adjust the gain on your subs amp accordingly.

Face

First, do not plug the sub into the back of your receiver, you'll starve the sub.

Second, I would follow the advice above about adjusting the gain on your sub and receiver.

Third, a better quality signal cable as mentioned also can help. I noticed an improvement going from a name brand cable to one from monoprice.com. According to some, a male to male Y-adapter on the back of the sub to the sub cable can help.

polkyman

Took the sub to HiFi Buys because the manager wanted to take a look at it. He was intrigued when I told him it still hums even when the rca cable is not hooked up to it. They plugged it in at the store and several guys there kept telling me that they couldn't hear anything. I said "Yeah but we're in a huge store with tvs and stereos cranked up all over the place. In my house it's when it's quiet and you can hear it humming. You have to get down and put your ear to it." After they tried that, they said it was very minimal hum which is normal for all subs. They said even the $1,000 subs have some small hum because of the built in amp. So I walked away with the assessment that it was "normal." Sound right to you guys?

gvg45

polkyman wrote: »

Took the sub to HiFi Buys because the manager wanted to take a look at it. He was intrigued when I told him it still hums even when the rca cable is not hooked up to it. They plugged it in at the store and several guys there kept telling me that they couldn't hear anything. I said "Yeah but we're in a huge store with tvs and stereos cranked up all over the place. In my house it's when it's quiet and you can hear it humming. You have to get down and put your ear to it." After they tried that, they said it was very minimal hum which is normal for all subs. They said even the $1,000 subs have some small hum because of the built in amp. So I walked away with the assessment that it was "normal." Sound right to you guys?

Neither one of the two subs I have own (JBL&HSU) make any noise.

dorokusai

Polkyman - The Polk CS crew is on you like bees on honey....a resolution is on the way.

Face

My PSW10 doesn't have a noticeable hum either.

polkyman

Well I certainly appreciate everyone's help. I've been starting to think that I've been too anal about this. In all honesty, the hum is very slight... you only hear it when the room is quiet. Still, it's enough to be annoying. They had my exact sub hooked up and on display at HiFi Buys and it too had the exact same hum. The reps there kinda looked at me like I was crazy when I told them they had to actually put their ear directly to the sub because of all the competing noises in the store.

If there is a solution, I will be very surprised since it hums simply by plugging the power cord in (without the subwoofer rca cable hooked up.) Even plugging it in by itself in the wall.. it doesn't matter.

polkyman

Oh and here is what the sub looks like - RM6750 series

Bill Ayotte

My Sunfire Super Junior (About $1200-$1500) had a real noticeable hum before I replaced the stock power cord with a Signal Cable Magic Power Cord......I actually A/B'd it when I got the cord because I was pretty sure that it still hummed, I just wasn't close enough....Dead silent. I also use a Monster clean power outlet adapter....The one that plugs over the outlet that they make for subs.....basically comes with a long screw, so you take the short one out of your outlet, plug this thing in, then secure it to the outlet....Works for me.

polkyman

Bill Ayotte wrote: »

My Sunfire Super Junior (About $1200-$1500) had a real noticeable hum before I replaced the stock power cord with a Signal Cable Magic Power Cord......I actually A/B'd it when I got the cord because I was pretty sure that it still hummed, I just wasn't close enough....Dead silent. I also use a Monster clean power outlet adapter....The one that plugs over the outlet that they make for subs.....basically comes with a long screw, so you take the short one out of your outlet, plug this thing in, then secure it to the outlet....Works for me.

Is it difficult to replace a power cord? Do you have links for it and the Monster clean power adapter?

[Deleted User]

Hello Polkyman,
Thanks for posting on the Forum, I'll try and offer some useful information. I believe there are two types of sub-woofer noise that are fairly common. One is a low level buzzing sound that comes from the area, of the sub-woofer, and is not effected by the unit's volume control. This is called "transformer lamination noise" and is caused by the building and collapsing magnetic field that surrounds the core laminations of the AC power transformers. It is usually very low level and isn't heard during operating of the sub-woofer. The second type of noise is more of a humming that comes from the woofer cone and is controlled by the unit's volume control. This kind of noise can be caused by external things, such as light dimmer switches, certain lighting devices and even wireless alarms. The test for this is to try and bring the sub-woofer to another area of your house, with no connecting cables or wires. Then see if there is any change in the humming level.
From what you have described, I believe you are experiencing transformer lamination noise. If you have a very quiet room and are particularly sensitive to this type of sound it could be a problem. It might be a good idea if you telephoned me at 1-800-377-7655 extension 891 and lets compare notes and see if something can be done.
Regards, Ken

polkyman

Kenneth Swauger wrote: »

Hello Polkyman,
I believe you are experiencing transformer lamination noise. If you have a very quiet room and are particularly sensitive to this type of sound it could be a problem. It might be a good idea if you telephoned me at 1-800-377-7655 extension 891 and lets compare notes and see if something can be done.
Regards, Ken

Thanks! I just might do that.

Deadof_knight

Oh dear god here we go with the power cord talk again ....just so we know Im a believer its the nons that I have a problem with .....shhhhhhh maybe they wont see this thread....

dlh

polkyman wrote: »

Well I certainly appreciate everyone's help. I've been starting to think that I've been too anal about this. In all honesty, the hum is very slight... you only hear it when the room is quiet. Still, it's enough to be annoying. They had my exact sub hooked up and on display at HiFi Buys and it too had the exact same hum. The reps there kinda looked at me like I was crazy when I told them they had to actually put their ear directly to the sub because of all the competing noises in the store.

If there is a solution, I will be very surprised since it hums simply by plugging the power cord in (without the subwoofer rca cable hooked up.) Even plugging it in by itself in the wall.. it doesn't matter.

I just bought my set today and the sub behaves exactly the same way, no input cable connected, barely audible hum with my ear next to the speaker. Hum disappears when sub powers itself down or when the power switch is flipped. I've moved it around to different circuits in the house and it behaves the same way.
It doesn't sound like lamination noise to me; I guess it could be lam noise coming through the speaker cone. Maybe the only way to find out is to remove the amp and listen to it directly. I bought mine at Circuit City and would bet that if I take it back, they won't hear it either