Martin Logan Descent Issues

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Freecrowder

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New to the board. I'm a repairer and have a friends Descent in to figure out any problems. I really don't think there is much wrong with it that I can tell. He did complain that when he turns it on it sounds like it is "wheezing" and it does. What it is doing is at power up after a couple of seconds all three woofers move out to what looks like max excursion. When they return to neutral the box pressure vents out of the threaded inserts located in the bottom of the speaker. Is the excursion on woofers normal at power up? The inserts are not sealed and are open to the box. I temporarily plugged them and the wheezing stops but it still goes through the excursion at power up. When I play it it sounds good to me and it also looks like it operates well with test signals down to 26 HZ.

Anyway is there any exsperts on this forum for this sub?
 

cabinum

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I don't have anything like that happening with my Descent i. Does anything look suspect on the board? They're known for failures . . .
 

Robert D

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My Depth i developed a problem somewhere. It randomly makes a large popping sound, the 3 woofers are all activated and make a sharp popping sound. It will then make a static sound. After a bit it's gone and may not return for a year.

That can happen even if it's not receiving a signal, with the receiver turned off.
 

ejspain

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New to the board. I'm a repairer and have a friends Descent in to figure out any problems. I really don't think there is much wrong with it that I can tell. He did complain that when he turns it on it sounds like it is "wheezing" and it does. What it is doing is at power up after a couple of seconds all three woofers move out to what looks like max excursion. When they return to neutral the box pressure vents out of the threaded inserts located in the bottom of the speaker. Is the excursion on woofers normal at power up? The inserts are not sealed and are open to the box. I temporarily plugged them and the wheezing stops but it still goes through the excursion at power up. When I play it it sounds good to me and it also looks like it operates well with test signals down to 26 HZ.

Anyway is there any exsperts on this forum for this sub?
I have an old Descent (not being used) and also experienced the full excursion (randomly) at power up. After about 6 or 7 years, it finally started to show signs of decline where the sub would rattle....even when not pushed very hard. I finally figured out it was coming from only one of the woofers so I called ML to see if I could purchase a single woofer. And not to my surprise, I couldn't. I still have the sub. Planning to set it up in a small listening room with my old Aeon i...seems to be ok long as I don't drive it too hard. I recently turned it on after not using it for about a year, and the full excursion thing happened but no other noises.
 
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Robert D

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I'm hoping their new Balanced Force subs don't develop these problems. I went ahead and bought the 220 and it's fantastic. My Depth i is in the basement on the gaming rig.
 

Freecrowder

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Appreciate the feedback EJ. So not to belabor point but at one point you know that when you powered up and did not experience full excursion but did develop that at a later date? Thanks for the feedback
 

ejspain

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Appreciate the feedback EJ. So not to belabor point but at one point you know that when you powered up and did not experience full excursion but did develop that at a later date? Thanks for the feedback
yea it didn't always do this. Started noticing the "full-excursion" thingy about 6 years in....a year or so after she said I had enough of this home theater business so she was retired...(but I didn't totally give up)...this was the most I'd ever spent on a sub ($2700 in 2005) plus it sounded really nice when it was new. Personally I think I over-drove it. 2004 was essentially my introduction into seriously investing in HT and spending $6k on two subs was out of the question....besides (in 2004 - "as a beginner")....who the heck needs two, three or four subs right??? NADOS (Never Again Do One Sub) :cool::cool::cool: Now I know I'm about to be killed but I'm gonna say it anyway - although I LOVED (and still do) my Descent (with its 3 - 10's), it doesn't shake a stick at the 1100X's. Ok I'm out😝
 

Leporello

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I have an old Descent (not being used) and also experienced the full excursion (randomly) at power up. After about 6 or 7 years, it finally started to show signs of decline where the sub would rattle....even when not pushed very hard. I finally figured out it was coming from only one of the woofers so I called ML to see if I could purchase a single woofer. And not to my surprise, I couldn't. I still have the sub. Planning to set it up in a small listening room with my old Aeon i...seems to be ok long as I don't drive it too hard. I recently turned it on after not using it for about a year, and the full excursion thing happened but no other noises.
Do you or anyone here happen to know if those woofers have built-in accelerometers or position sensors? Something that would be used in a feed back loop? A faulty one of those could very likely be the cause.
 

ejspain

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Do you or anyone here happen to know if those woofers have built-in accelerometers or position sensors? Something that would be used in a feed back loop? A faulty one of those could very likely be the cause.
no idea
 

Freecrowder

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that is a good point. they do have a feedback connection on the speakers. I do not know if they are accelerometers or what type. I know that I have seen some FB that just use another voicecoil. It's a good point though, if the FB element was bad or flaky it could definitely cause a problem like that.
 

Robert D

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that is a good point. they do have a feedback connection on the speakers. I do not know if they are accelerometers or what type. I know that I have seen some FB that just use another voicecoil. It's a good point though, if the FB element was bad or flaky it could definitely cause a problem like that.
Yes, the woofers are a certain type that has some kind of control like that. I cant remember what it is or it's name. It's a type.
 

Leporello

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New to the board. I'm a repairer and have a friends Descent in to figure out any problems. I really don't think there is much wrong with it that I can tell. He did complain that when he turns it on it sounds like it is "wheezing" and it does. What it is doing is at power up after a couple of seconds all three woofers move out to what looks like max excursion. When they return to neutral the box pressure vents out of the threaded inserts located in the bottom of the speaker. Is the excursion on woofers normal at power up? The inserts are not sealed and are open to the box. I temporarily plugged them and the wheezing stops but it still goes through the excursion at power up. When I play it it sounds good to me and it also looks like it operates well with test signals down to 26 HZ.

Anyway is there any exsperts on this forum for this sub?
I never realized the threaded inserts are openings to the air in the enclosure. Mine did not come with spikes. I guess I should plug them. Got mine on eBay and it was packaged poorly, so that was the least of my worries.
 
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