Subwoofer rumble issue


I’m having a hard time solving a problem that seems to come and go. My subwoofer will rumble uncontrollably when playing records at a higher volume. If I turn the volume down sharply it goes away but when I creep the volume back up it comes back. I’ve tried isolating my turntable as much as possible with diy books, isolation feet, etc. (I don’t want to buy an expensive isolation platform unless that really is the issue.) Any thoughts on what I can do to fix this? Thx!
paulgardner
Haha it’s absolutely a self serving move but it’s cool. Always be closing, right? I’ll consider the springs but we’ll see. Thx
My bad! 🤗. P.T. Barnum says if something is not promoted something terrible happens. Nothing. 
It might be your turntable.  I had a Concept and it was super sensitive to footfalls.  I couldn't walk anywhere near it without the arm jumping around.  Granted, I have springy floors and it wasn't very well isolated, but I've had a number of tables before and after it that didn't have that problem.  I seem to remember issues with what you've described at high volumes also. 

It's surprising and unfortunate, because it does seem to be a solid and well built table.  It may have something to do with the magnetic bearing tonearm design.

There are a number of reports of this issue if you do a web search.  There are also many who love it and report no problems with it.  There seems to be a consensus that it needs to be really well isolated.

I really liked mine and wanted to love it, but it didn't work in my less than ideal setup where many other tables have worked great.  You'll notice I use the word "seems to" a lot in my post, there's obviously some supposition on my part, as I was never able to figure out how to get mine to work satisfactorily in my system and I know many others have that table and love it.  Do you have another table you can try out and see if it has the same issue?
I don’t have another table on hand to swap in to see if it is indeed the Concept that’s causing the issue. I might give the subsonic filter a shot before giving up on the Concept. I really do like it aside from this apparent issue. Time to play the DIY isolation game!