The Bradford Baffle - Original Acoustic Suspension Speaker?

[Guest linedrive]

This is from a very strange ad in the January, 1960 issue of Audio magazine. Does anyone have knowledge of this thing?

http://www.classicspeakerpages.net/dc/user_files/1534.jpg

[tysontom]

>This is from a very strange ad in the January, 1960 issue of

>Audio magazine. Does anyone have knowledge of this thing?

>

This was one of numerous ads and claims made through the years, claiming of "breakthrough" technology, that simply died on the vine. I don't believe this particular company existed for very long. Usually these unscientific claims were made because of professional jealousy of successful designs in the market place.

--Tom Tyson

[Guest linedrive]

Thank you for the information, Tom.

What a place to advertise such nonsense, too! Audio magazine's strength was its technical expertise - specialists in the field frequently presented their state-of-the-art work in its pages.

In fact, this issue has a piece by Edgar Villchur, clarifying his explanation of the acoustic suspension principle from a previous Audio article, and pointedly answering some of his critics from the infinite baffle - bass reflex camp.

His explanation of air-spring linearity, and adiabatic and isothermal pressure changes is brilliantly written, and easily understood by the layman. I feel smarter, just having read it!

[dynaco_dan]

Hi Ted;

Must have been a real hot seller back then.

It is not a brand that I have ever heard of before, but, then again, I live in Canada, The Great White North.

[Andy]

Yes there were many types odd speaker add ons as well. Back in the 1930's Zenith console radio's had a beehive shaped cover called "The Acoustical Adapter" which sealed the back of the speaker. A friend of mine has a 16 tube Zenith with this adapter, and I'll admit the sound is pretty impessive for a 1938 radio.

Also of interest....in a 1962 court ruling, AR's patent was found to be invalid because of one that Harry Olson and John Preston of RCA had gotten in 1949. In Edgar Villchur's own words, he said the following...... "the centreal feature was a compliant-mechanical-rim suspension design. There was no general claim for a system that had a speaker mechanism with a free air resonance frequency substantially below it's optimum operating resonance, and which therefore required a small enclosure. That's what acoustic-suspension is, but the judge, who was totaly non technical, ruled against us. I guess I feel vindicated by the fact that the Smithsonian Institution, in it's exhibition on the history of technology, shows two speakers; a bass reflex unit and a AR-3."

[Guest Rod H.]

Never heard of the company, but it sounds like they may have been describing an aperiodic enclosure, or something with similar characteristics.

Rod

[pmsummer]

It's ads like that (but not that ad) that caused Paul Klipsch to make those Bullsh*t buttons he famously handed out.

[Guest SherwoodFool]

Excuse my ignorance, But what is the difference between an Aperiodic design & an AS. Dynaco is the only co. that advertised Aperiodic's. At the time I never thought about it.

Russ

[tysontom]

>Excuse my ignorance, But what is the difference between an

>Aperiodic design & an AS. Dynaco is the only co. that

>advertised Aperiodic's. At the time I never thought about it.

>

>Russ

Russ, the "aperiodic" design was a bass-reflex variation with a highly damped port (filled with fiberglass). It was carefully tuned, and the speaker produced decent, relatively flat bass response, but distortion was higher than an equivalent acoustic-suspension design. Some efficiency was sacrificed to get less peaky response, but some of the advantages of a bass reflex enclosure were retained. There were other variations of this enclosure type, but the most famous example is the Seas-designed Dynaco A-25.

The acoustic-suspension system is fully sealed, of course, and uses the compliance of the entrapped air as a restoring force (90% in original AR speakers, for example) for the woofer cone. In this application, air is more linear than the mechanical springs (spider and surround) of the speaker, and the distortion is very low -- a hallmark of all properly designed acoustic-suspension speaker systems. In an aperiodic speaker, the restoring force for the cone is primarily the mechanical parts of the speaker, with air resistance providing only a small part of the restoring force.

--Tom Tyson

[RoyC]

The term "aperiodic" was also used to describe later designs suggested by the high end driver manufacturer, Dynaudio, through the use of one or more "variovents" in speaker cabinets. These were approx 4" disks stuffed with fiberglass. A small boutique speaker company, Audio Concepts Inc (www.audioc.com), actually produced some nice speakers utilizing the concept.

No sound was supposed to be produced by the "vents", and internal cabinet air pressure was still utilized as a part of the design, though to a lesser degree than in an acoustic suspension system. The vents were meant to reduce the pressure at certain low frequencies.

Roy

[Guest SherwoodFool]

Thanks.

-Russ