audio-talk

one of my sons just sent me this. I haven't read it through yet, but it looks interesting:

https://news.mit.edu/2022/low-power-thi ... eaker-0426

Its interesting, but probably not for us

They tested their thin-film loudspeaker by mounting it to a wall 30 centimeters from a microphone to measure the sound pressure level, recorded in decibels. When 25 volts of electricity were passed through the device at 1 kilohertz (a rate of 1,000 cycles per second), the speaker produced high-quality sound at conversational levels of 66 decibels. At 10 kilohertz, the sound pressure level increased to 86 decibels, about the same volume level as city traffic.

Ignoring all the cringeworthy units used in the article like measuring weight in dimes and power in "smidgeon" and the above passing voltage "through" something.

If you want to use a flat surface as a radiator AER has had a real audiophile solution for some years https://aer-loudspeakers.com/aer-bbx/

Its not cheap at around €3600.00 per unit but it is very good.

James

I remember seeing that. Have you heard one?

Yes, once in Dubai of all places on their Goldie open baffle with their sub-woofer below 180Hz so on a plexiglass panel about the size of a Quasar. It was close to sound of the AER BD drivers in the same demo room but the sub-woofer didn;t match them for speed or timbre. I haven't heard them on a plasterboard wall but I'm told they are similar but with better bass reproduction potentially down to 20Hz. They use a DSP processing box to eq the response in the room. Here is an AER customer review https://aer-loudspeakers.com/customer-r ... x-exciter/

ciao

James

Intriguing

Does anyone remember the NXT cardboard pyramid speakers?
I had a pair around 2002 I think. They were surprisingly good, considering they were about £30 with an amp!
I think my pair ended up going off to uni with eldest son. They were easy to transport because they folded flat.
Anyway, I think that was the earliest example of the exciter on a flat panel? It seems the mit is an evolution where the exciter is also a flat panel.

Yes had those Max, they were surprisingly decent.

Max N wrote: ↑Thu Apr 28, 2022 10:17 pm Does anyone remember the NXT cardboard pyramid speakers?
I had a pair around 2002 I think. They were surprisingly good, considering they were about £30 with an amp!
I think my pair ended up going off to uni with eldest son. They were easy to transport because they folded flat.
Anyway, I think that was the earliest example of the exciter on a flat panel? It seems the mit is an evolution where the exciter is also a flat panel.

earliest example 2002? where were you in 1970’s?

Well, I was in Peterborough in the 1970's, but I don't think there were NXT speakers then.

Nick wrote: ↑Fri Apr 29, 2022 10:33 am Well, I was in Peterborough in the 1970's, but I don't think there were NXT speakers then.

I found this when searching for NXT speakers start date.

"The whole thing kicked off in the late sixties/early seventies with Poly Planar speakers and of course the original polystyrene diaphragm Yamaha NS series, which at least had a metal chassis, but no edge suspension."

*

This AES paper https://www.aes.org/e-lib/download.cfm?ID=21014 quotes a 1926 US patent (H. W. Joy, “Diaphragm,” US Patent 1,611,454 (1926 Dec.)) as the earliest reference to a flat panel loudspeaker design...

BTW I have notes that the earliest cone dynamic loudspeaker patent is two years earlier i.e. 1924 although I can't find my reference to it and Wikipedia states

The dynamic speaker was invented in 1925 by Edward W. Kellogg and Chester W. Rice issued as US Patent 1,707,570. Apr 2, 1929.

I should state that non-dynamic loudspeakers were being developed by Edison et al from about 1880 - mainly mechanical acoustic horns of one form or another

I can't find a copy of the Joy patent and I've run out of energy this morning... more to come if their is interest...

ciao

James

I stand corrected.

pre65 wrote: ↑Fri Apr 29, 2022 11:04 am

Nick wrote: ↑Fri Apr 29, 2022 10:33 am Well, I was in Peterborough in the 1970's, but I don't think there were NXT speakers then.

I found this when searching for NXT speakers start date.

"The whole thing kicked off in the late sixties/early seventies with Poly Planar speakers and of course the original polystyrene diaphragm Yamaha NS series, which at least had a metal chassis, but no edge suspension."

*

Those are the ones I remembered. Our science teacher had them. Probably 1970/71. Not too bad.

Nick wrote: ↑Fri Apr 29, 2022 10:33 am Well, I was in Peterborough in the 1970's, but I don't think there were NXT speakers then.

They never made it into the Laskies catalogue. I think they were either in melody maker or exchange and mart. The only two comics I read at the time. But my science teacher had them, however Im pretty sure they were readily available from one or other of above comics. on same page youd have found Eagle oval drivers with two tweeters on a metal flat bar centrally in front of the woofer centre. Thata and military surplus flying jackets! Makes you think of carpet baggers the film!