Russ Andrews Microphonic Equipment Placement and Time Smear

Hi-Fi News’ Russ Andrews has a system set up column, “Russ’ Top Tips,” where he has suggested that music listeners should place their equipment rack in between the left and right loudspeakers. Many readers wrote in not liking the idea and Mr. Andrews defends the placement in his latest column (at least the issue available in the US, Feb. 2007, page 98, maybe the UK is a month ahead).

According to Andrews, you need to place your equipment rack dead center and maybe a little nearer the front wall of the front loudspeakers (at least behind the front baffles to avoid imaging interference) because that is the quietest and most in time place in the room when music is playing. Huh? I’m not sure how the spot between the speakers is the quietest (though we could all easily check with an SPL meter), but lets take his word for it. What I have a problem with is his reasoning behind the “quiet” spot: all of your equipment’s internal components (diodes, caps, etc.) are microphonic, meaning they are reabsorbing the sound waves out of time and this is distorting the music. Isn’t that called feedback? Shouldn’t we all be dealing with shrill whines from our loudspeakers that change depending on placement?

Well, no. The distortion is never that harsh. What we need to hear is a muddying, maybe a “time smear,” at worst an echo. Andrews writes that the further away the equipment the worse the distortion, every little electronic part on your amp’s circuit board vibrating away with the music. Are your loudspeakers’ crossover circuits safe because they are inside the speakers?

Microphonic vibrations in all components is where audiophile science gets very pseudo for me (even though I’ve invested heavily in isolation shelves and feet). Audiophile experts, like Russ Andrews, take a problem that normally affects only a few components in your system and apply that same problem to every component equally. Microphonic vibration distortion is a problem for your turntable’s needle and maybe any vacuum tubes in your amplification chain (see the turntable isolated wall shelf and tube ring industries respectively). These are real, audible problems.

Wouldn’t microphonic distortions be measurable by a simple impulse response? At a high enough resolution wouldn’t you see two initial impulses?

If your components were more than 20 ms away (around 20 ft.) from your speakers would you actually hear an echo as that’s the time point when the brain can differentiate between direct and reflected sounds (maybe this only makes sense in the air and not in small vibrations picked up by your amp’s MOSFETs)?

I’m just trying to bring these system tips to their logical conclusions.

Luckily for me, I’m above the problem as my components are in a wall-flush cabinet that protrudes into an adjoining room. All my components are on IKEA Lack end table-top shelves (light and hollow for fast vibration disappation, good according to Andrews) behind solid wood doors. I’m crossing my fingers that out of time bad vibrations aren’t poluting my music system.

One more thing: Don’t even pretend to be concerned about “time smear” unless you listen exclusively to time and phase coherent loudspeakers, the only technology you could hope to reveal these small (if not insignificant) distortions. (My apologies to Mr. Andrews if he owns Vandersteen, Thiel or Quad ESL speakers).

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