[dkordonowy]

Hello all,

I've had my Force XL for a while now (6 months?), and love how it has accentuated my mains.  Twice now however, I've heard a low buzzing emanating from the sub while the rest of the system is powered off.  The first time I heard it was about two weeks ago, and as I was going on vacation for a week, I powered off the sub and left.  When I got back, no buzz.

Now however, the buzzing has come back.  I just powered off the unit.  If I immediately power on the sub the buzzing comes back, so I think that I would need to let it "sit" for a while for the buzzing to stop again.

My question is: what is causing the buzzing?

It sounds like it is coming from the subwoofer.  Unplugging the RCA cables doesn't help.  I've got it plugged into a surge protector.  I've made sure that there are no other cords lying parallel to the power cord on its way to the outlet. 

Here's my system, if it matters:

Denon DVD-1930ci
Yamaha RX-V2600
Thiel 1.6
ACI Force XL (connected via RCA cables from the main pre-outs of the Yammy)

Thanks for any help that any of you can provide in debugging/fixing the problem,

dkordonowy

[NewBuyer]

Does the buzzing come from the speaker cone itself, or does it sound like a mechanical buzzing from inside the box, like a buzzing transformer perhaps?

[dkordonowy]

Does the buzzing come from the speaker cone itself, or does it sound like a mechanical buzzing from inside the box, like a buzzing transformer perhaps?

I'm thinking mechanical buzzing.  I put my hand on the woofer and really couldn't decide whether or not I could feel it moving, so I'm thinking it wasn't [moving].

[Mike Dzurko]

Occasional a Force XL or Titan XL will develop a slight mechanical hum. The windings on the transformer have heated up and cooled down and have shifted ever so slightly and now are causing the hum.

It is simple to eliminate the hum. First, unplug the amp and let it set 5 minutes to allow all the energy stored in the capacitors to dissipate. Remove the six screws that hold the amp to the cabinet. You will notice that the round, torroidal transformer is held in place by a bolt that runs through the middle of the transformer and is terminated with a Phillips head in the middle of the heatsink area on the outside of the amp. You will need to loosen the nut with a wrench while holding the screw with a Phillips head screw driver. With the nut loose, rotate the transformer about 1/4" to the right or left and tighten the nut down onto the transformer. Secure the amp back into the cabinet, plug it in and you are ready to go.

 

[dkordonowy]

Occasional a Force XL or Titan XL will develop a slight mechanical hum. The windings on the transformer have heated up and cooled down and have shifted ever so slightly and now are causing the hum.

It is simple to eliminate the hum. First, unplug the amp and let it set 5 minutes to allow all the energy stored in the capacitors to dissipate. Remove the six screws that hold the amp to the cabinet. You will notice that the round, torroidal transformer is held in place by a bolt that runs through the middle of the transformer and is terminated with a Phillips head in the middle of the heatsink area on the outside of the amp. You will need to loosen the nut with a wrench while holding the screw with a Phillips head screw driver. With the nut loose, rotate the transformer about 1/4" to the right or left and tighten the nut down onto the transformer. Secure the amp back into the cabinet, plug it in and you are ready to go.

Thanks!  I'll try this when I get back from my business trip and report back...

[NewBuyer]

Mike, do you think it could perhaps be DC on the user's AC line? I've read this can cause intermittent transformer buzzing (mechanical), I recall PS Audio sells their UPC-HB that they say fixes this problem with transformers. What do you think - would such a thing even be a possibility with the Force XL?   

[Mike Dzurko]

Mike, do you think it could perhaps be DC on the user's AC line? I've read this can cause intermittent transformer buzzing (mechanical), I recall PS Audio sells their UPC-HB that they say fixes this problem with transformers. What do you think - would such a thing even be a possibility with the Force XL?   

I've learned that nearly anything is possible. Only way to know for sure would be to try something like the UPC and see if that takes care of it.

[krikor]

Mike, do you think it could perhaps be DC on the user's AC line? I've read this can cause intermittent transformer buzzing (mechanical), I recall PS Audio sells their UPC-HB that they say fixes this problem with transformers. What do you think - would such a thing even be a possibility with the Force XL?   

I would agree that this is definitely a possibility.  I've noticed that my pair of Force subs (which I believe are electrically identical to the Force XL) sometimes exhibit a slight buzzing from the transformer and not the driver, as far as I can tell.  It only occurs during certain times of the day and more frequently during the summer when everyone's AC is running.  It is also clearly evident when my wife is upstairs drying her hair ... this drove me nuts diagnosing the problem as the buzz kept coming on and off before I realized it was linked to the hair dryer.

The buzz always emanates from both subs, not one or the other, which further indicates that it is not a transformer problem but a mains line issue.

BTW: In addition to the PS Audio UPC/HB, diycable.com sells an RFI/DC filter that should also remedy this problem.  I haven't tried it yet, but may pick one up in the near future after I've completed a few of the other projects I've got sitting unfinished.

http://www.diycable.com/main/product_info.php?cPath=21&products_id=536

[NewBuyer]

That RFI/DC filter from diycable looks interesting. Nice find! Also much less expensive than the now-discontinued PS Audio UPC-HB.

Mike I'm wondering please, does the Force XL have any internal circuitry intended for blocking DC on the AC line? I think some manufacturers will just use a capacitor for this, but I'm not sure.

I still have much to learn about these things. 

[Mike Dzurko]

Mike, do you think it could perhaps be DC on the user's AC line? I've read this can cause intermittent transformer buzzing (mechanical), I recall PS Audio sells their UPC-HB that they say fixes this problem with transformers. What do you think - would such a thing even be a possibility with the Force XL?   

I would agree that this is definitely a possibility.  I've noticed that my pair of Force subs (which I believe are electrically identical to the Force XL) sometimes exhibit a slight buzzing from the transformer and not the driver, as far as I can tell.  It only occurs during certain times of the day and more frequently during the summer when everyone's AC is running.  It is also clearly evident when my wife is upstairs drying her hair ... this drove me nuts diagnosing the problem as the buzz kept coming on and off before I realized it was linked to the hair dryer.

The buzz always emanates from both subs, not one or the other, which further indicates that it is not a transformer problem but a mains line issue.

BTW: In addition to the PS Audio UPC/HB, diycable.com sells an RFI/DC filter that should also remedy this problem.  I haven't tried it yet, but may pick one up in the near future after I've completed a few of the other projects I've got sitting unfinished.

http://www.diycable.com/main/product_info.php?cPath=21&products_id=536

You're right, it's the 60Hz noise that causes the transformer to buzz. A good conditioner will virtually eliminate it.