Speaker Very Quiet Until Turned Up Loud Enough

I have a speaker (Yamaha HS7) that was working fine when I left for work this morning, but tonight when I came home and turned it on it as playing very quietly. It's just the right speaker. The left speaker is fine and both run into the subwoofer which then runs to the computer. However, it turns out that if I turn the volume up loud enough past a certain point, the speaker momentarily distort at the volume that it should be and then "snap" into working properly. I can then turn the volume down to normal listening levels and it will continue to work properly unless I turn the speaker down too quietly. This is repeatable. These speakers are pretty new (2 or 3 years old). Does anyone have any idea of what the conceptual problem might be with the speaker?

EDIT: It seems there is a range of volumes just below the volume where the speaker snaps into working properly where the speaker will cut in and out between distortion and silence.

EDIT: Okay, it's not the speaker. The issue followed the right audio cable from the PC that plugs into the subwoofer so it's either the cable itself or my soundcard.

That's a common problem when the Speaker Protection relay in the amp/receiver develops oxidation on the contacts. Start by swapping the speakers left/right to confirm it is the speaker or the amp/receiver.

If it is the speaker protect relay in the amp/receiver, find it and see if you can get the cover off of it. Drag a piece of contact cleaner (preferably Deoxit) soaked paper between the contacts.

After it followed the subwoofer end of the input cable to the sub around, I can't seem to get it to reproduce the issue again. I wanted to reproduce the problem so I could swap the computer end of the cable around to make sure it's the cable and not the soudncard but I can't get it to happen again.

Okay. Now it's following the speaker around and not the cable anymore. What the hell? Last time it followed the cable around. I guess it's time to start swapping the amp/receiver/sub output cables to see whether it's the speaker or the sub. I'd much rather have it be the sub.

EDIT: Yeah, I think you're right. The problem is the sub/amp/receiver.

I got the service manual. The issue is in the right channel. Is the issue more likely to be the filter switch or phase switch?

EDIT: actually, SW501 and SW502 aren't relays, just manual toggles. They're never switched so could they still be the issue? The only relay is RLY401 but that is for the sub speaker. The "mute" switches (Q301/2/3/4) are driven by the sub relay driver it looks like they are listed as transistors in the parts list.

It turns out it was SW501, the lowpass filter cutoff. I guess the pole for the right speaker got oxidized. Switching it back and forth once got rid of the issue...for now...

dknguyen said:

It turns out it was SW501, the lowpass filter cutoff. I guess the pole for the right speaker got oxidized. Switching it back and forth once got rid of the issue...for now...

Click to expand...

Yes, contact oxidation can cause the problem you observed.
At low voltages it acts like an insulator, but higher voltages can punch through the oxidation.
At certain voltages, only the voltage peaks of the sound waveform may get through, causing an odd type of distortion.

crutschow said:

Yes, contact oxidation can cause the problem you observed.
At low voltages it acts like an insulator, but higher voltages can punch through the oxidation.
At certain voltages, only the voltage peaks of the sound waveform may get through, causing an odd type of distortion.

Click to expand...

I've never observed that from a device before just sitting in my house in dry conditions, unswitched. Was fine that morning and just started happening the next time I turned it on after work. Over the next 2-3 days the volume required to "punch through" just kept getting louder and louder. Is there anything I can actually do about that? I don't want to have to open up all my speakers and subs, and then open up each switch and relay (if it's even possible) and apply some protectant to it. I'm actually kind of surprised those switches are directly in the signal path and didn't realize they were until I got the service manual. I thought they just toggled some control signal to something elsewhere.

Small squirt of WD40 in each switch, and work it back and forwards a few time, job done.

WD40 tends to be far better for such purposes than expensive 'switch cleaners', and we used it professionally for decades at work.