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If you can bear to part out an Ampex speaker-amp, you have a great starting point for an excellent infinite-baffle system. The speaker in that little cabinet has a lot of extension ability and if it's mounted in a shallow closet's door, for instance, it puts out a LOT of bass and a lot of volume with that little 10W tube amp, or so I've been told. The early red-vinyl cases contained speakers designed by James Lansing and built by Ampex itself. Later models have different (but better lower-bass) speakers made by JBL for Ampex. -- Tom Fine ----- Original Message ----- From: "Randy A. Riddle" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, February 08, 2013 8:35 PM Subject: Re: [ARSCLIST] Passive radiator loudspeaker was Mono but Out-of-Phase > Reminds me of the prof in my college Physics of Sound course that > brought this tiny little speaker - a common 1" or so thing from a > transistor radio - into class one day, saying it was his great new > hi-fi. He plugged it in and, of course, you could barely hear it at > all. > > Then he walked into another room and brought out this huge circle made > of plywood that was about as tall as he was with a tiny hole in the > center. He placed the speaker in the hole and - voila - nice hi-fi > sound. > > rand > > On Fri, Feb 8, 2013 at 6:42 PM, Michael Biel <[log in to unmask]> wrote: >> From: Don Cox <[log in to unmask]> >>>>> Electrostatic speakers have no enclosure. They are not infinite baffle >>>>> unless installed in a will. >>> >>>>> Infiniet baffle is a technical term that means none of the sound from >>>>> the back comes to a listener in the front. >> >> On 08/02/2013, Lou Judson wrote: >>>> Strictly speaking, yes. However, a large baffle can be very near to >>>> infinite in practice. Frequencies down to about 80 Hz can be controlled, >>>> and below that, in most living rooms there are so many complications from >>>> room effects that it is hard to say what is happening to the sound. >>> >>>> For example, in my teen years I put speakers in the walls of the >>>> living room that had the attic behind them. Infinite baffle. No front >>>> vents. <L> >> >> I used to describe it in class by pretending to mount a driver on the >> classroom door. If the door was open there would be cancellation of the >> front and back waves. Close the door and we hear only the front -- and >> annoy everyone in the hall. Now, if the door is not sealed at the >> bottom, the slot is the bass reflex opening. If you want a round hole, >> remove the door lock. In an old building if there was a transom above >> the door, we could tune the opening. Now if we open a window and the >> classroom next door have their door and windows open, that could be a >> labyrinth reflex opening (Bose???) >> >> I sometimes used a closet to explain acoustic suspension speakers since >> we could "seal" a closet. Then I dragged in a horn tweeter from an >> Altec A-7 and blew their minds telling them that this huge heavy >> cast-iron monster was a tweeter. Then came the explanation of the horn, >> and the horn/labyrinth reflex woofer mounting of the A-7. >> >>> Strictly speaking, unless your attic was infinite in volume, this is >>> another "large baffle". >> >> I also discussed mounting the driver on a window, then the great >> outdoors was a real infinite baffle! >> >>> And can one speaker act as a passive cone for >>> the other (if the big drum is all in one channel, for instance) ? >>> Don Cox [log in to unmask] >> >> In my case I was in mono! But in discussing multi-driver systems I >> explained that the backs of the other drivers had to be sealed or in a >> separate box so that they are not affected by the rear compressions of >> the woofer. >> >> Mike Biel [log in to unmask] >