Problem with Descent

[babydoc]

I have a Descent subwoofer that begins to "flutter" after a certain on-period, usually an hour or so. I have done the usual things, disconnect, reboot, change cables, change channels. The "flutter" increases with increasing gain and disappears when I put the level below "2" which makes the sub nearly inaudible.
It does not seem to depend on whether there is significant low-bass material playing and it occurs on all 3 drivers.
I have narrowed the suspects down by virture of design to the following:
1. Problem with preamp/gain board (front panel with controls)
2. Amplifier power supply
3. Bad driver

BTW, I run the subwoofer off an auxiliary RCA output from my Pass X0.2 preamp. I have 3 other M-L subs in my system all of which are fine. I also use the "auto-on" feature rather than continuous on setting.

Any thoughts or suggestions?

 

[Diamonds]

Hello-

Why don't you try and trigger that particular sub with speaker wire jumped from your speakers. Then you could rule out a problem with your sub or not. That should work.

Thanks!

 

[Peter Hogan]

I have a Descent subwoofer that begins to "flutter" after a certain on-period, usually an hour or so. I have done the usual things, disconnect, reboot, change cables, change channels. The "flutter" increases with increasing gain and disappears when I put the level below "2" which makes the sub nearly inaudible.
It does not seem to depend on whether there is significant low-bass material playing and it occurs on all 3 drivers.
I have narrowed the suspects down by virture of design to the following:
1. Problem with preamp/gain board (front panel with controls)
2. Amplifier power supply
3. Bad driver

BTW, I run the subwoofer off an auxiliary RCA output from my Pass X0.2 preamp. I have 3 other M-L subs in my system all of which are fine. I also use the "auto-on" feature rather than continuous on setting.

Any thoughts or suggestions?

Hi,
My guess would be that it has a problem in the servo-feedback circuitry. I have a velodyne sub with servo-feedback, and it will go into a full excursion 1-2 Hz resonance if the speaker is removed from the cabinet, thereby losing the cabinets damping effect.

Just my .02,
Peter

 

[JonFo]

To further isolate the problem to the sub, disconnect it completely from the rest of the system and leave it 'on' (turn off 'auto-detect') and see if it goes into oscillation. That would tell you it's completely in the sub.

If it does not do it alone, then feed it signal from something other than your main rig, something simple, like the output from a portable player.

 

[babydoc]

Descent problem

Thanks for all of the suggestions. I have found that it occurs with the sub on and no signal going to it but if the power has been on for about 1 hour. I subsequently called Martin Logan and tech support suggested that it was a probably defective woofer that was creating a message to the servo unit when the servo did not need to be active.
I am in the process of replacing the woofers and will see if that solves it.