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 Bouncing Off The Floor

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Join date : 2009-09-18

PostSubject: Bouncing Off The Floor   Sat Mar 31, 2012 12:42 pm

Hi Zonees

The old Quad electrostatic speakers (commonly called ESL 57s) were originally made to be either placed directly on the floor or on short wooden feet. This was true also for the later ESL 63.

Then along came Arcici and some others who made stands for the Quads lifting them a couple of feet higher up and some audiophiles went “WOW! What an increase in clarity….”

Not all audiophiles fell for this because Sonic recently read a piece by Dr Robert E Greene on a topic he has repeatedly commented on – the floor bounce.

Sonic has heard Quad ESL 63s mounted on the floor, on low stands and suspended high on the “specialist audiophile stands” and the warmth is gone when they are lifted. They sound thin and coloured in the way some audiophiles think is the way real music sounds.

Loudspeakers when elevated off a floor exhibit a difference in path length – direct sound comes to the listener’s ears and the sound wave also bounces off the floor and arrives at the ears slightly delayed. Put simply, this floor bounce causes a cancellation notch in the 200 – 300 Hz range (right around Middle C says Dr Greene) and causes a thinning out of the upper bass, a loss of impact, indistinct viola low range and weak cello high ranges. Orchestras lose weight and jazz ensembles lose vitality sounding bleached and analytical instead.

Worst off are dynamic speakers whose woofers are mounted high off the floor near the top of their cabinets near the tweeters or with assemblies are raised high on stands like mini-monitors. Some pundits say that floorstanding dynamic speakers are worst off. Basically, if you got a box speaker and if your woofer is off the floor either because of the cabinet or your stands, you will get floor bounce and a 200 – 300 hz notch that will lean your music. How bad is this notch supposed to be? Anything between -3 to -10 dB.

The effect of the floor bounce is measurable I am told, unlike the mythical sidewall first reflection which so many audiophiles talk about.

Line source speakers like the Magneplanars and Martin Logans are relatively but not completely immune from the floor bounce notch.

Some manufacturers have tried to get round the bounce-notch by either mounting the woofers low in the cabinet (but the long distance from the tweeters introduce new problems) or like Salmi and co fire the woofer downward (Gradient from Finland).

I have read a rebuttal to the idea of floor bounce by some saying that everywhere we go, we are encountering floor bounce -- from people speaking standing up, to musicians playing, to sound of car engines. What they fail to see is that all these sources are at different distances heights and have different spectral contents so whatever effect is balanced out and even if not, these are real not reproduced sounds. With loudspeakers in a room the entire signal containing the sound of voices, orchestra and car engines are uniformly subject to the same spectral distortion so the effect is very present and distorts everything.

On the other hands, the researchers at the BBC -- whom Sonic reads much about and admires -- have found that when playing music in damped environments, an increase in realism and "listenability" was achieved when a reflective surface was place ahead of and between the loudspeakers.

Michael – comments on the floor bounce if you please. What is your experience with this and how do you fix it? Does it need fixing?

From Dr Robert Greene’s viewpoint, the floor bounce can be dealt with by some form of absorption on the floor between the loudspeakers and the listener. Some use layers of foam. Others have even dug trenches in their floors. One Spendor owner Sonic knows used pyramidal Thai cushions as absorbers (tis sounded too muddy and acoustically dead to me).

If we look at Tuneland products, we could apply Deco Tunes on the floor between the speaker and the listener. Maybe even tipping them up on the edge nearer the listener to have more volume under the Tune surface and control the pressure wave better.

Maybe Zonees could give their systems a listen and if they hear any leanness they could give the floor bounce a shot with EchoTunes, DecoTunes and see if these fill out the 200 – 300 hz range.

Sonic, after resetting my system and reinstalling my Janis W-1 subwoofer, crossover, Rotel amp along with Space Cones, the bookcase wall moved further back, resetting the FS-PZCs and special DRTs to bring my system back to the set up at end-February meant I had a pair of FS-DRTs spare. I am trying them out now, tipped over in front of the Magneplanar 1.5QRs. The FS-DRTs have their bases attached and their reflective sides facing up towards the ceiling. Having the FS-DRTs bases attached means they are at an angle and there is more volume under the FS-DRTs which may control the pressure zones better.

First impressions are I am getting a fuller instrumental compass in the low midrange, upper bass and a more solid soundstage. Let’s see where this leads.

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