MicroPRO 2000 "thumping"

Milsivich

I have been troubleshooting this problem for 4 months now, and I have finally established one of two things; either the MicroPRO 2000 is the biggest ripoff of all time, or I have received 3 sets of defective parts in a row.

My Setup:

Parasound NewClassic 2100 pre-amp
Parasound NewClassic 2125 amp
Pair of Polk LSi9's
MicroPRO 2000
Sony turntable
laptop (connected with HRT Music Streamer II, an offboard DAC that hooks up to the USB port)

The Problem:

At low volumes, as low as 8 out of 40, a HORRIBLE thumping noise comes out of the sub. It sounds exactly like the sub is being maxed out, only its volume level isn't even near that of the "room optimizer" setup sequence. It happens on any sort of beat or kick. This effect is extremely obvious to even untrained ears. More minute details are they even on prolonged tones there is an unevenness or a quaver about the sound, and also that the beating of the subwoofer is behind that of the speakers.

Troubleshooting:

I'll lay out everything I have tried, from the top of my system to the bottom. I tried changing the source by playing the same song from my laptop (both with my offboard DAC and a headphones jack to the "mp3 in" feature of the pre-amp) and from my turntable, no change. I tried different cables, including some really nice Monster cables. I hooked up the source directly to the sub (skipping the pre-amp). I tried hooking the sub into the "main out" instead of the "sub out." I have changed the physical location of the sub, even holding it in the air with my hands while it played.

This first MicroPRO 2000 I got I returned because of this problem. The second one I received also had the problem, at which point I personally replaced the amp and the speaker cone with new replacement parts from Polk. They all had the EXACT same problem.

The pre-amp was recently at the top of my list of possibilities, but the problem persists even when I hook the source directly to the sub. Also, other subs sound find from the same pre-amp, as do the LSi9's, which dip almost as low as the subwoofer and sound absolutely delightful.

Conclusion:

I still have no idea what is wrong. I have eliminated all possibilities it seems, but the problem is still shockingly obvious. This is sort of a last ditch effort to see if anyone has any ideas before I just trash the whole thing and start over, which would be devastating considering the time and money I have put into this thing.

Thanks in advance for any ideas!

Mon40CSMM10

Unless the subwoofer amp setting is extremely high, is it possible it's an amp becoming defective? Do you have another receiver you can use to test the subwoofer with? Does it happen at higher volumes?

I had a similar problem with a lower end BSR amplified subwoofer years ago. That was a subwoofer designed for boombox/portable stereo type of devices with lower output volumes. At certain lower volumes, the subwoofer would emit a higher pitched pop sound like port noise when the subwoofer amp dial was too high. Testing showed the volume level was just at the threshold where the subwoofer amp would power on, but was insufficient to keep the amp on for a while. The solution was to use a higher lower volume level.

disneyjoe7

Yes, sounds like subwoofer setting is too high. Most should be around 10 to 11 o'clock.

Milsivich

The volume is 10/40, preamp 25%. This is 1200 watts, 2400 dynamic. Based on those numbers, this should be loud, and it doesn't even get above speaking volume before failing.

codyc1ark

Mitpydayvap wrote: »

One more symptom I forgot to mention about his problem that may help with the diagnosis...when this first started happening, you could hear the thumping when sitting still idling in "PARK" and turning the wheel sharply to the left or right. NOW, it no longer makes the noise while idling in park. We recently changed the fuel filter, and had waited too long to change it, so the engine was straining to get fuel...now its not. This is leading us the think the problem may be power steering pump/system related and connected to the power demands put upon it when turning the wheels sharply. Does that make any sense??

No..

cnh

I reviewed the MicroPro 1000 a while back. Never had "any" problems with it. Certainly nothing like what you describe. Now, as I understand it the only difference between these subs is the ability to adjust the sub with AutoPro/mic room optimizer with the 2000 series. Is it possible that that is the culprit? The mic/adjustment?

Can you just return the sub to whatever its defaults are and run it sans any mic balancing?

I've run the 1000 sub in a mid-sized room between 26-30 out of 40 and never found myself "overdriving" it or getting weird thumping noises. I can't help but think that instead of that auto system "optimizing your system, that it is actually "de-optimizing it" and causing it to be overdriven?

cnh