A Copernican View of the Turntable System

Observations of Direct Sound Pressure on a Tonearm

The recent posts have been great, informative and enlightening for me. Thanks guys. TBone - looking forward to your results as well …

Sorry for the long post.

I was curious, so I tried to create a direct air borne problem before it became a structure feedback problem just to see if possible. Two TT’s together on the side wall directly opposite the firing of one of my speakers. Everything u wouldn’t want to do to get direct airborne feedback with a TT I did. The first TT is no more than 6 feet away from the drivers of my speaker. Before I tell u what happened let me say I have played around quite a bit already with this air pressure phenomenon but from the other end.

I have experimented with my air bearing arms to see how the air pressure affects them as it comes out of the air bearing. I learned what their maximum PSI threshold is. Go past this point and they start to resonate from not being able to handle the PSI. Keep just under it and you have magic happening. Anyway above this threshold they resonate and can’t hold the cartridge/stylus in the groove properly anymore. A loss of detail happens. Your $$$$$ TT rig starts sounding like a $$ rig. No surprise right ?

So I thought what the hell, this is going to be more fun than yelling at the cartridge so I let loose on them hoping to make the tonearms/cartridges show some signs of sonic deterioration. I played big music at well over 100 db. What happened?

Well first thing is not what I could hear but feel because my listening chair was vibrating. I then went over to one of the speakers and felt the sound anchor stand holding up the 110 lb speaker. The heavy metal SA stand was resonating. They are spiked to the basement concrete slab. My room is closed 12 X 24 FT. with speakers in nearfield firing down the length. The side walls were also resonating. But what about the music ?

Nothing – NADA – the music and tonearms were fine as far as I could hear. So in my case with this little experiment I heard no direct sound pressure effect on the tonearms. If you don’t believe me.

Ask this Audiogon member if he is worried about Direct Sound Pressure from the Speakers ?

So based on this I agree with what Henry said. The airborne feedback is changing (mutating) into structure feedback. Its going into the walls, the floor, the racks the gear. Everywhere. Structure Feedback is the audiophiles version of “VIRUS” movies. Go ahead put up a shield - its going there too - now u will have something resonating next to your precious $$$$$ tonearm - does this make sense ? I dont know I didnt try it but I'm also not going to Home Depot to buy plexiglass or something else to surround the TT either. I've heard enough.

Structure feedback is there but until you discover it no matter how small a problem it may be and correct it as Pryso's experience tells, you may not even realize its there. This has to be one of the leading causes of why gear may sound good at the dealer, but then people bring it home and it sounds different ?

This experiment was good for me because it gave me a better idea on the limits of what my room are. My racks isolate ok to well above 100 db so below that where I actually listen I am fine for now. Could they be better - definitely - maybe I will ask Don to build me a nicer rack ?

But I think I need a new listening chair first?

Thoughts ?

Forgot to mention I have some very serious structure feedback issues at the TT in the other location - old building, suspended floors. Am looking at buying a TT shelf or building one for there. I sympathize with those of you with suspended floors.

Dear Chris, This remind me about this Jew who was complaining about his shoes:'they are killing me'. His answer about the cause was that they are too small. But when asked why he buys too small shoes his answer was: 'it feels so good when I put them off'. BTW I think that you have some other 'structural problems'. 'the other location' imply that you can use the 'other one' without 'structure feedback issue'.
Regards,

Hi Nikola
As long as I stayed in my chair it was very nice but loud - the vibrating chair added to the effect :^) . But sustained levels would not let me enjoy this hobby for very long. It did however start feeling like a shoebox at those levels when I got up to check the gear, walls, etc...

Yes the other building has many problems. Adding vinyl there exposed many of them. It will be a challenge.
Cheers

Addendum. Dear Chris, you made an important discovery without knowing what you discovered. Otherwise you would at least pronunce: Heureka. There is no way to value anything without comparison. Even 'better' assumes some, not to mention 'the best'. Alas your method is to expensive: two or more 'locations' are not attainable for the most of us. So I have a proposition which is even cheaper than Halcro's concrete arm pod. Buy the cheapest MM cart you can find ( I have some from East Germany) and
use it by every listing session for one hour and then switch to whatever other cart you own. You will be suprised with the result. BTW such results seems to be the 'basics' in psychology.

Regards,