gam@amdahl.UUCP (G A Moffett) (12/29/85)
I would like suggestions on what kind of speaker stands to buy to
prevent noise from speakers to travel thru the floor (I life on
the second floor). My speakers are 11" x 13" and about 1.75 feet
tall. I don't recall how many watts they are but it is a "medium"
number.
I would also like to take this opportunity to encourage people whose
floors are the opposite side of other people's ceilings to be
considerate of what noise their speakers on floors could produce for
their neighbors, and do things to ensure your stero does not disturb
them.
--
Gordon A. Moffett ...!{ihnp4,cbosgd,hplabs}!amdahl!gam
~You tell me it's the institution...
Well, you better free your mind instead (shoo-be-do-wap ...)~alw@mit-eddie.UUCP (Alan Wu) (01/03/86)
<chomp> As an apartment dweller, I heartily endorse the idea of isolating speaker cabinets from the frame of the building (usually the floor). In my building at least (7-story steel, reinforced concrete and brick) mid and high frequencies don't get transmitted very well from one apartment to another. But low frequencies, including heavy footfalls and mid to low bass, travel quite well once they get into the frame of the building. As for footfalls, my wife and I always change to cushioned sandals as soon as we get home, both for noise reasons and to leave the street dirt at the door. Contrary to what some people believe, walking around barefoot in an apartment produces very strong coupling of low-frequency sound into the floor (at least the way most people seem to walk). When I first moved in, I had some problems with sub-sonic feedback from my speakers to my turntable. I also noticed that even quite modest levels of bass would couple right into the floor. From what I remember of physics, the basic construct needed is a mechanical low-pass filter. The filter has to pass "DC" (zero frequency) because you need to hold your speakers up (lacking a zero-g environment :-) ). But you want to attenuate anything higher in frequency than say 3 Hz or so. Lacking any detailed specs on mechanical compliances, damping factors and such, I resorted to a little trial and error. What I now use is a stack of 3 large double-corrugated cardboard boxes of the type DuPont Chemical uses when they ship half a dozen 5-pint bottles of nasty stuff like sulfuric acid (i.e. they don't want to take a chance on the bottles breaking in shipment). They're fairly sturdy, but have a higher mechanical compliance and damping than say wooden crates. Each of the boxes is packed with maybe 40 or 50 pounds of little-used books. What I end up with is a 3-pole low-pass mechanical filter, more or less. My speakers (Allison Three) are each placed on top of one of these setups. The Allisons are inverted so that the woofer is located in the corners of the room right near the ceiling, and the midrange and tweeter are right about ear-level. (For those of you who are not familiar with the Allison Three, this is an alternate speaker placement recommended by Allison Acoustics. This corner placement is NOT suggested for speakers not designed for it, since it will otherwise result in exaggerated bass. One of the reasons I picked the Threes is their ability to produce excellent sound while perched in the corners of a very crowded apartment). The whole setup allows me to play the stereo as loud as I wish, with excellent bass and imaging, without imposing my music on the neighbors. In the process of "consulting" for other neighbors and friends, I have found that dry cellulose sponges, rubber balls sliced in half, typewriter pads, and molded-paper eggcrate dividers have the right combination of mechanical compliance and damping. I'm sure that you could find other low-cost easily-available materials that could do the job as well. Besides speaker isolation, these materials and methods are equally applicable to the problem of turntable isolation. The reason I am retaining the extensive cross-posting to net.whatever is that I think this "technology" needs to be distributed to a fairly wide set of people. It is not covered much in the audio publications, since it doesn't encourage the sale of this or that exotic hardware or accessory. But I suspect that there are other readers out there who would benefit themselves and/or their neighbors by applying some of these simple ideas. I suggest sending any follow-up to net.audio or sending email to me (no flames, please). --Alan