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Romy the Cat


Boston, MA
Posts 9,540
Joined on 05-28-2004

Post #: 1
Post ID: 14687
Reply to: 14687
Superbly interesting effect: Suspended decoupled floor delay
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Last night I was experimenting with integration of ULF and midbass and was playing relatively loud. The ULF woofers is at second order at 35Hz and the were located outside of my listening room, in the next room with a large wale between then, but divided under the floor with a solid concrete load-bearing wall. I have not year installed the jacks properly under my listening room floor. I have 5 of them and I will do it later on.

I played very loud and I clearly felt that floor was vibrating. I wrote about it before and I very much hate this effect. However, what was VERY surprising that the bone vibration this time did not bother me at all. Generally I am very much disturbed by bone transmitted vibration but this tile I had practically no negative feelings.

I know that among with some sane people there are plenty of idiots who read my site and reading it they feel that I “so in love with my own audio” that I do not recognize problems.  Well, there is a reason why call them idiots – because they try to apply own primitive behavioral pattern to guess the “convenient truth” about me. OK, the hope the idiots stopped reading. Kdfsdjfjdf sdosdfgijfo eoergjeojeg ogeoe sdfojrtiowdgt…..

Discard the last sentence. That was to assure that the idiots do not read anymore. The realty why my suspended floor “sounds” in a way it sounds is much more interesting. I made a number of experiments last night and realized that I have a very fascinating setting with my floor.  Here is an illustration what is going on, read below the image with explanation.

Suspended_floor_delay.JPG

My main MF speakers “AA”, located on the suspended floor of my listening room do not shake floor too much. The midbass horns “BB” do shake but they are “hanging” on the other side of the solid wall to which the floor is suspended. The ULF section “CC” do shake as well but it also sit on the other floor that is suspended to a different side from the listening room. So, the vibration does not propagate itself from right suspended surface to the left suspended surface (listening room). Still the listening room’s floor vibrates. Considering that I have in the room a LOT of pressure generating devises I concluded that the vibration of the listening room’s floor come from air pressing the listening floor. The pressure is building in the room, makes the listening room’s floor to act as a diaphragm and forces it to vibrate. Now is the kinky part. The airborne vibration does not travel as fast as the vibration transmitted across solid surface. The air in the room acts as a buffer that introduces the vibration propagation delay. I did measure this deal and it is huge in length – over 200mc. It is understandable why – the compliance of floor is very high and air need to be compressed in the whole room to push floor down. So, with this huge delay the leading edge or pulse has a direct floor vibration event. Instead a very loud pulse has a few very small “aftershocks” in over 200mc. This completely set mind to discard the event of vibration as there is no direct association between the original sonic effect and the vibration aftershock that might be felt on the floor. The Precedence Effect and Haas Effect describe the events that under 30-50ms. With such a huge delay as I have the sound and the vibrations feel absolutely unrelated and therefore the vibrations feel more like random, none-harmonic vibrations.

I think I still will put the jacks under the floor and will lower or get rid of the vibration’s amplitude (which is VERY low as now and indicate itself ONLY at VERY loud sound) but I would tell you honestly that even to have such disassociated vibrations does not affect me negatively. 

This is very interesting discovery that made me to think about other things. OK, tell me that I am crazy but here is a theoretical question: if the associated vibrations affect us but the unassociated do not then why we USE this idea for intentional shaping of the unassociated vibrations. I am talking about a shaker devise that  read the signal and vibration pattern from a surface, process the result and inject in real time into the surface own  version of contra-vibrations that would be either in contra-amplitude  or with harmonic offset that would stress that unassociated effect.

Rgs, Romy the caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
Page 1 of 1 (1 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Midbass Horns and Real Estate...  Just a youtube video......  Horn-Loaded Speakers Forum     247  1503236  07-26-2009
  »  New  Romy The Cat's new Listening Room..  Won't be the last time he makes that trip!...  Audio Discussions  Forum     478  1879956  03-28-2010
  »  New  Macondo’s Midbass Project – the grown up time...  Vitavox 15/40...  Horn-Loaded Speakers Forum     455  1987520  05-20-2010
  »  New  Macondo’s lowest channel...  Good highs...  Horn-Loaded Speakers Forum     148  952797  09-15-2010
  »  New  How to USE “Resonating Oops” in loudspeakers..  I will do it when I have time....  Horn-Loaded Speakers Forum     183  1032249  02-28-2007
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