Going on the advice of "How to Get Better Sound", I placed my TT platform on the side wall about 3 feet from my left speaker. Because my sound room is on the second floor and I have a suspended floor, I built a suspended platform, out from my wall using appliance springs and tie-down straps/metal cables, so it basically "floats." This worked great, until I added another JL Fathom 13 sub. I couldn’t even turn the subs on, due to low frequency feedback that would build on itself. I tried the inner tube trick, the sandbox trick-everything I could think of to no avail. I finally moved my turntables to between the speakers. I’m sure, some of you are thinking-what a moron-everyone knows that and I would agree. It took me several trial and error positions, to find this place, where no room nodes are effecting the playback. I think in the long run, acoustical energy has a huge effect, on the playback, specially at high volume levels. As far as cones go, I was a skeptic. I have a Theta Miles CD player I dearly love and only use analog outs on it. I had to utilize thick foam, so the low frequency would not effect the playback. (too much low frequency for the room size) I placed four cones, one under each corner of the CD player and was amazed to not have anymore low frequency pick-up. Maybe I will try just three cones in the future. I know you said you can’t move your equipment, but as mentioned above, sometimes just a little change, can have a huge effect on your sound. Room nodes can be neutralized some, with room treatment. As a matter of fact, I think proper room treatment, used in the proper way, will give most of us better sound, than an equipment upgrade. I’m a believer in Dennis Foley’s technique and products. If you haven’t tried them, or are not familiar with them, go to his web sight "Acoustic sounds."
Feedback through turntable
My system consists of a McIntosh C2300 preamp, MC452 amp, MCD500 SACD player, VPI Aries 3D with Ortofon Cadenza MC cartridge, Manley ChinookSE phono stage, PS Audio P5, Sonus faber Cremona Auditor M speakers and REL B1 Sub bass system. My issue is with turntable use only; SACD has no issues. On my pre when volume is +55 (peak at 45watts) I start to get feedback through the turntable - a sort of low freq sound, back off volume and it goes away. My Auditor M speaker is about 3 ft away and in front of turntable. I do have a rumble filter (KAB) installed between preamp and phonostage to help with sub woofer pumping. Due to room layout I cannot rearrange the setup/move turntable. My turntable is on a 2.5" block of wood and that sits on 4 isolation blocks via spiked feet. Any thoughts how I can eliminate this problem? Harry Weisfeld with VPI states he has 4 15" woofers (JBL Everest) near his Prime Signature setup with no issues at all. Why am I having this problem and how can I eliminate it? Thank you in advance for all feedback.