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Bass distortion-Playing LP's only,,,,please help

VPI Prime----Ortofon Black Quintet (low output moving coil cart)-----Plinius Koru Phono Pre( loading at 20 ohms/gain at 66 db)-----Parasound Halo Integrated -----Martin Logan Montis speakers which have powered bass cabinets.

Using any other source component I have absolutely no issues. When I play an LP and increase the volume past 10 O'clock which is a little loud....but not ridiculously loud-I at times get this huge wave of bass distortion. I do have bass controls on the Montis's...and I have turned them down into the negative, but I still get what I previously described occasionally. 

Any and all help would be appreciated. This doesn't always happen, but its frequent enough to drive me crazy.

Thanks in advance.

krelldog
stereo5's avatar
stereo5
6,428 posts
 
I am willing to bet you are getting some feedback. Can you remove the grill and observe if the woofer is oscillating abnormally? If it is, its a feedback problem. I had this problem with my Scout and now my Prime. My turntable is on top of a rack on a solid 3 inch thick maple air dried platform which is sitting on a sandwich material I bought from Mapleshade. I still got it. I bought a KAB Rumble filter for 180.00 and put it through the tape loop. Now the problem is solved and I haven’t lost any bass quality. You should hear how subteranian it goes during some songs on Amused To Death.  I could rattle the fillings out of someone's teeth!
krelldog OP
323 posts
 
Wow.... I have never heard of a rumble filter....but it sounds spot on to my issue. My bass cabinets aren't accessible,so I can't confirm the rumble. However for 180 bucks its worth a try.... thanks guys.
lewm
13,170 posts
 
Krelldog, Better to move either your turntable or probably just one of your woofers (if they are separately housed).  Though the rumble filter will probably do the job, it's another item in the signal path that probably you could get along without.  Filters are not entirely transparent.
mofimadness's avatar
mofimadness
4,993 posts
 
@krelldog...these were/are known also as subsonic filters.  I'm sure you've owned at least one preamp or phono stage that had one.  They used to be pretty prominent on preamps, but not so much now.
moonglum
619 posts
 
Good advice above Krelldog but one other thing worth trying : the Montis active bass will (I presume) have a bass roll off control. I've always felt with MLs bass output that "less is more". Try introducing a few dbs cut (say -4 setting on each or whatever you feel is appropriate) and see if it solves the problem and whether you can live with it?
All the best
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