On Fri, 2 Feb 2007, ronan mcallister wrote: > > On 2/2/07, Gene Heskett <gene.heskett@xxxxxxxxxxx> wrote: >> >> The individual pipe may not, but the harmony or beat between two 32 foot >> pipes can easily reach considerable energy levels well below 20 hz. Even >> the 16 footers can 'shake your guts' at the right close harmony notes. >> Our own organs 16 and 32 foot pipes rank each other across the backdrop A 32 ft pipe is still only at 16-17Hz, not 5Hz >> >> They can be built, and in much smaller cabinets than the famous Altec >> Voice of the Theater sizes which were actually built huge for efficiency. No. They are built huge to bring down the resonance of the speaker in the box. Even with zero frequency resonance of the cone itself ( which is of course never the case), the frequency goes as the square root of the the area of the cone squared times atmospheric pressure divided by the mass of the cone times the volume of the box. The smaller the box, the higher the frequency. Those speakers i believe tended to be horns for efficiency, but the horn cutoff was probably still about 50Hz. You cannot get good bass out of a small box, no matter how to tweak it. (Or ratehr if you are happy with one note bass, then you can design a Helmholtz resonator at whatever freq you want, but that is not a speaker.) >> We once rebuilt the relatively small box the Bozak floor model came in, >> about 28" tall by 24" wide, 15" or so deep, an infinite baffle design. >> Replacing the 10" B305 driver with a B305AL which had a 2" throw, >> stiffening up the box with cross bracing till it clicked like marble when >> tapped with a mallet anyplace on it, and added about 3x the normal sound >> absorber material inside it. Cook used to make some 78 rpm lp's intended >> as demo records for us 'hi-fi' peddlers to use, and one of them had >> several tracks of percussion solo's. The tympani track was a favorite to >> demo that speaker with as it went on for about 45 seconds, then you could >> hear the squeak of the peddle linkage as he let the drum skin go slack >> after the last strike at the end. A normal OOTB speaker did the squeak >> and that was the end. With the rebuilt box, the room went up and down >> several times after the squeak. This was 47 years ago, using a 30 watt >> McIntosh amplifier, or a Dynaco of about 20 watts. That speaker still had a resonance at about 20Hz probably, and with that sized box the resonance in the box was far higher. Note that your exponential horn, which has a mouth diameter of about 15ft and the speaker was almost certainly less than 2ft, which implies and exponentiation of 2, Since the length is 17', the cutoff frequency is 1/2pi 8'= 1/48' which is about 20Hz. Ie, your horn speaker will produce very little sound below 20Hz. To get 5Hz requires a horn about three times as large. At 5 Hz the wavelength is 64 meters-- about the size of a football field. ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
