Depth Sub "Squeaking" During LFE

My Depth subwoofer has a weird squeaking sound that occurs only during loud low frequency effects passages from DVDs, i.e. stuff that heavily uses the .1 LFE channel, such as crashes, explosions, etc. The level control on the Depth is only set halfway (at 5), and the overall volume of the system is not cranked up outrageously loud, so it doesn't seem as if the sub's amp would be anywhere near the clipping point.

My Depth is connected to the subwoofer output of a Rotel RSP-1068 preamp/processor into the LFE input on the Depth. I temporarily hooked up a HSU sub to the same output from the Rotel, and there's no trace of the squeak from the HSU, so the problem does not appear to be in the signal content coming from the Rotel, it's something inside the Depth.

Anybody experienced a similar problem before with either a Depth or Descent?
Any idea what's causing it?

P.S. I've only had the Depth a couple of months. I just heard this squeaking recently, but it's possible that I had not previously played DVDs with enough LFE to trigger it, so I can't say for sure whether the problem just developed or if I just encountered something that's been lying in wait all along.

Is it a squeak or a whistle? A whistle indicates a leak in the cabinet or driver and the squeak sounds like the driver is reaching the limits of its excursion, i. e. it is physically running out of travel. The Hsu woofers have great excursion limits and stupidly high output levels so this (excursion) may be your issue.

I have previously heard the whistle, indicating an air leak in the sealed cabinet. I was able to correct that by tightening down the screws which hold the amp plate.

This problem is definitely distinct from the air whistle. I suppose it could be from the drivers reaching the end of their excursion, but it doesn't seem like the output is high enough for that to be happening. I live in a townhouse condo with a neighbor on the wall side directly behind the sub, so I tend to keep the volume to modest levels. I would be amazed (and disappointed) if that's as loud as the Depth can go before bottoming out. To get a comparable SPL on the HSU, the volume knob on that sub is only set to about 1/8 of its range, so the HSU is barely being pushed at all.

Nevertheless, I'll have to remove the grill covers on the Depth and watch the drivers in action.

Tighten the driver screws too.

I think they even mention that in the owner's manual. (It doesn't sound electrical. ) If tightening the driver screws doesn't do it, it could be that at long excursions, one of the woofers is contacting something in the cabinet -- like a dangling speaker hook-up wire, or piece of damping material.

Handyman said:

I have previously heard the whistle, indicating an air leak in the sealed cabinet. I was able to correct that by tightening down the screws which hold the amp plate.
Nevertheless, I'll have to remove the grill covers on the Depth and watch the drivers in action.

Click to expand...

nsgarch,
I"ll give a try to tightening the driver screws as well, and if that doesn't do it, I'll open 'er up and take a looky-see inside.
I see from your profile that you also have a Depth. I take it that yours does not make sounds like I am describing.

Well, I haven't used the LFE input on my Depth (no HT), so I can't say what would happen. And I roll off the low freq. at 35Hz, so I'm not driving it that hard. But I play enough loud organ music that I'd think it would tell me if it had a problem, !

Handyman said:

nsgarch,I"ll give a try to tightening the driver screws as well, and if that doesn't do it, I'll open 'er up and take a looky-see inside. I see from your profile that you also have a Depth. I take it that yours does not make sounds like I am describing.

Click to expand...

I just heard the squeak last night on my Depth i during heavy mega bass sequences...while watching Pirates of Carrib. II. I will make sure the backplate is tightened. I had the 35Hz dial to +0.5-1. Overall level is at 5. When i turned down the 35Hz dial to 0, the squeak disappeared. So, at this time, it appears to me that Depth i does not go as deep as ML states. Any other theories??

SQUEAK PROBLEM SOLVED!

When I got home this evening, I tighened up all the driver screws, then I fired up a DVD chapter that was causing the problem, but the squeaking was still there, no different. It was also clear that the drivers were not even approaching their full excursion when it was happening.

Determined to figure this out, I cranked up the volume and moved my ear around the sub until I could clearly hear where the squeak was coming from: underneath the sub. The sound was coming out of the threaded holes for the feet, which in the case of my unit were unoccupied. A couple of weeks after I bought my Depth, I had replaced the standard ML feet with a set of Soundcare SuperSpikes that I had on hand. These were the adhesive version, which just stick on, so I wasn't using the threaded holes for the feet. Apparently, the empty holes were acting like miniature ports for the air pressure inside the cabinet, and when the pressure got high enough, it created a bizarre form of port noise. So, I tighened some 1/4-20 screws into the holes, using rubber washers to ensure a good seal, and voila, squeaking totally gone.

The SuperSpikes are great feet by the way, but if you're going to buy some for your Depth or Descent, get the threaded version, which I'll probably do when I get A Round Tuit.

Strange thing is...i am using the ML spikes. I better check on them tomorrow.

Thanks for investigating the issue.

Strange that ML would have a through hole and expect that screw foot to seal the enclousure. I woud have thought that they would have designed a sealed enclousure with the spikes not part of the box . As in your case , when you do not want to use them you dont have 1/4 inch ports.

C.A.P said:

Strange that ML would have a through hole and expect that screw foot to seal the enclousure. I woud have thought that they would have designed a sealed enclousure with the spikes not part of the box . As in your case , when you do not want to use them you dont have 1/4 inch ports.

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When I had removed the original feet, it never even occurred to me that the threaded holes would go all the way through the cabinet. Maybe with the ML feet/spikes, the cabinet is sufficiently sealed that it doesn't matter.

It does seem strange but here's how it works: the threaded inserts in the bottom of the cabinet that accept the spikes/feet are themselves threaded into a hole in the wood bottom. That hole has to go through the wood to allow the foot sufficient travel for adjustment while still having all its threads engaged for strength/stability. The easiest solution for plugging the hole is a rubber automotive body plug or nylon bolt with a little heavy grease on it. The reason for the grease is that the threaded hole in the metal insert actually has an Allen socket milled right through it for inserting the fitting into the wood. That allows air to still escape around the bolt. So just goop some heavy brake or axle grease in the hole before you attach the foot and that should seal things up.

C.A.P said:

Strange that ML would have a through hole and expect that screw foot to seal the enclousure. I woud have thought that they would have designed a sealed enclousure with the spikes not part of the box . As in your case , when you do not want to use them you dont have 1/4 inch ports.

Click to expand...

Well, i checked all of my Depth i spikes...they are all firmly screwed in. The backpanel looks tight. Still with squeak on heavy bass sequences when i crank my LEVEL pass 5 or my 25 Hz dial past 0.5.

Gonna call my Tweeter guy....