Woofer sucking in and out

Its an isolation problem as other have mentioned - keep experimenting to find the location that causes the least disturbance. Understanding how the sound waves radiate from your speakers based on how you set them up will help alot here. Keep it away from the sound waves as best as possible.

What type of clamp or weight are you using. Before spending big dollars on rings get one of these. Used with the rubber washer under the lp it will flatten the record edge to ensure it touches the platter all around.

http://www.needledoctor.com/JA-Michell-Record-Clamp?sc=2&category=421

If you are using a weight alone in the middle it will make the lp ends go up as well.

A filter is a band-aid as other have mentioned and not a fix.

Good Luck

Cool responds. I am only using Thorens weight at the middle. Most of my LPs are used so the arm is moving up and down some times! I will have a look at rings and weights than. Thanks.

Rodman, Thanks for the info. Very useful! Ah.. Has anyone used those heated device to flatten a wrapped disc?

They do work, but- the good ones are not cheap, timed cooling and all that: (http://drhifihousecalls.com.au/New%20Equipment/Furutech/Furutech%20Record%20Flattener%20DFV-1/Furutech%20Record%20Flattener.htm) It can also be done, in the oven, between two thick pieces of glass(with extreme care). (http://www.radiodismuke.com/forum/index.php?showtopic=670) Happy experimenting!

BTW: I think someone mentioned this, but- a record weight(just in the middle), will cause the circumference of some thinner vinyl records to lift off the mat. If there is an acoustic feedback issue, this will exasperate it. The one mentioned by Ct(with the black felt washer under the label), addresses that nicely, as long as it can clamp to your spindle. Mine is tapered, and I have a thicker than stock mat. I can't use a center clamp, as a result.