Turntable feedback


I was listening to a record on my Rega planar 3 which sits on a 1 inch thick slab of granite which sits on 4 metal vibration isolation points which sits on a tabletop made of a slab of solid hickory that is 1 1/4” thick. Yet through all that I had bass feedback. The feedback went away when I turned the volume down a bit. It was not that loud. I’m thinking the bass energy went right to the turntable and not up from below. Any thoughts on getting to the root of the problem? Subwoofer is a Goldenear which is powerful but I don’t like bass to be unnatural sounding so it is not booming at all.  I like it for its detail not punch. 

The turntable is in a corner nook so I wonder if there is a standing wave in the nook that could be transferring directly to the platter. Has anyone else had this problem?

Thanks
schmitty1

Showing 2 responses by glennewdick

Best recommendation I can give in your situation is get a wall mount for your table. And get it out of the corner. 

that said;

 I have tried cones and they do nothing to help, one member recommended Iso acoustic footers and I'll second that, it's what I use to very good effect. Just make sure you get the right sized ones for the weight of your table-slab-system that will be supported by them. Also over damping can cause you to lose detail and sound gets sort of muddy so be careful. 

I also use a large granite slab 3" thick and 165lb and without isolation it will transmit small vibrations regardless of what other think (sorry geoffkait but my experience dictates otherwise, not to take anything away from your huge experience) its "ringing" in the resonant frequency of the particular piece you have. That's dictated by the dimensions. 

Maybe ringing is not the correct term but there is vibration transfer in granite that could be described as ringing that's why you need some isolation, IMO of course. example my case; with out isolation if I tap the slab I can here it clearly in the speakers, no music playing tone arm on the rest. I say its ringing because the tap decays over time not a single short sound. the decay rate is quite fast but noticeable. with the Iso Acoustic footers I still get a slight noise but it has no decay and is much attenuated almost undetectable.  So with the Iso Acoustic footers I get the benefits of the mass and isolation as well. 

 I believe from my experience Isolation and the granite mass need to be done together for best performance, sand box is great idea too if you have the space. who doesn't like to play in a sand box, right?

 Another consideration is how much mass do you want swinging away at the top of your stand. Depending on how high your stand is it's a factor that I have encountered that needs to be addressed, think pendulum here. 

Remember your Rega is designed to be a low mass table so adding mass will not help it do what it was engineered to do, correctly. you may find it sound best right on the wood top. Or better get-make a wall mount. 
if you want stone that has a natural damping feature get slate. costly though. 

I've been through all this over the last couple years as I put together my Garrard 301. I was originally going to go with a stone, probably slate, but its quite expensive to get and harder to work with.  I finally settled on Bamboo ply layered.  I had a slight issues with my granite slab transferring noise to my table when it was on pin points. I tried hard, I tired soft isolation schemes ( many of each type) I eventually forked over the cash for the Ios Acoustic footers and problem solved. I even took the granite slab out but the loss in detail was not worth it so I found another solution in the Iso Acoustic Orea.  my tables 100lb'ish sitting on that dam 165lb slab lol I don't have rumble issues lol. bad back defiantly.