Getting back on track. The springs I've been using lately are just that, springs. Some from eBay, different sizes, are just plain springs. Nobsound are just springs too, only with caps or footers drilled out to hold them in place. Point being they are all bounce, with no damping. Like Max said his engineering indicates an ideal .16 damping.
Didn't seem to matter with speakers. Plain springs under the Moabs worked fine. Under the subs, ditto. Even under the turntable, seemed to work fine- at least at first. Got some more, put them under the power conditioner. Speaker cables, power cords and interconnects are on rubber bands. Virtually the whole system is now suspended, one way or another. Not exactly free to move- a lot of the cables are pretty stiff. They will restrict free movement and at the same time feed vibration into the component. Hard to avoid. But for the most part it is all suspended or if you prefer isolated.
One day I notice this drone or rumble. It happened on a lead-in where there's no signal so I thought it was really bad rumble and my bearing or motor or something was shot. But no. Darn noise would come and go. One time I got up to go check and while walking to the turntable it stopped. Went away. I froze. No rumble. Okay. Went to sit back down, came right back!
Took a very long time to realize this was undamped resonance feeding back into the turntable. At just the right frequency the system would be excited and with no damping it would feed back and amplify until it was just super alarming loud.
Even a small change anywhere in the system would stop it, like me moving my weight around the room. Tried different things, the best so far is to add a 5th leg under the table this one with a very small bit of sorbothane that eliminates the feedback.
Didn't seem to matter with speakers. Plain springs under the Moabs worked fine. Under the subs, ditto. Even under the turntable, seemed to work fine- at least at first. Got some more, put them under the power conditioner. Speaker cables, power cords and interconnects are on rubber bands. Virtually the whole system is now suspended, one way or another. Not exactly free to move- a lot of the cables are pretty stiff. They will restrict free movement and at the same time feed vibration into the component. Hard to avoid. But for the most part it is all suspended or if you prefer isolated.
One day I notice this drone or rumble. It happened on a lead-in where there's no signal so I thought it was really bad rumble and my bearing or motor or something was shot. But no. Darn noise would come and go. One time I got up to go check and while walking to the turntable it stopped. Went away. I froze. No rumble. Okay. Went to sit back down, came right back!
Took a very long time to realize this was undamped resonance feeding back into the turntable. At just the right frequency the system would be excited and with no damping it would feed back and amplify until it was just super alarming loud.
Even a small change anywhere in the system would stop it, like me moving my weight around the room. Tried different things, the best so far is to add a 5th leg under the table this one with a very small bit of sorbothane that eliminates the feedback.