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How to fix woofer pumping

Hello,
Looking for a little assistance/advice. I recently noticed some pretty severe "woofer pumping" while playing at a fairly high level. I don't think it's feedback, as it will not "run away" and get worse, just seems to suck the power out of the base. My system is in a fairly open room, system pics are accurate placement, but the gear has changed a bit. Last changes were getting rid of a ML 32 pre and replacing it with a VTL 7.5 plus the Ayre P-5xe phono pre. The ML had a rumble filter, which I used, the Ayre does not. System:
Clearaudio Champion 2
Clearaudio Titanium
Wall mounted with granite
Any help is appreciated.
128x128putty
srwooten's avatar
srwooten
694 posts
 
Check your cart alignment.
atmasphere's avatar
atmasphere
11,793 posts
 
Putty, if the mechanical resonance of the arm/cartridge arrangement falls outside of 7-12Hz, you will have problems. I don't recall my arm theory all that well but on one side of that window you can get pumping effects. The resonance is a product of the effective mass of the arm, and the compliance of the cartridge (which would be too high if you have pumping). Intuitively, it seems to me you will need to reduce the mass of the system somehow, or go to a cartridge that has a stiffer cantilever.

The *other* thing that can cause pumping is weak filter caps in the electronics. If this is the case you should be able to maintain the effect for a few seconds or indefinitely upon lifting the arm off the LP. Try that before anything else.
fnupacreek
4 posts
 
Putty, you might check out the cartridge database, they have a wealth of info and helpful calculators. There is info on cartridge and arm compatability there.
http://www.cartridgedb.com/
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