Geddes on Acoustic Lever

[jzagaja]

Dear Dr. Geddes,


Can you give some insight into practical Acoustic Lever (AL)? It is meant to be an alternative to bass horn. Speak software that simulates such enclosure doesn't work with non-US Windows and even then it does not load databases and projects with AL so it's useless.

How should we calculate those three volumes, compliances and masses?

What is known driven diaphragm should be slightly smaller then driver and radiating slightly bigger. Maximum ratio 2:1. I'm most interested in rear AL so that we extend bandwidth rather than gain efficiency.

[jzagaja]

Earl come on

[PeteMcK]

I wouldn't expect Earl to give away info. that would compromise his intellectual property;
a close read of the patent (& paper?) should allow you to make an educated guess...???

[jzagaja]

No problem but he sells Speak that helps with AL but it doesn't work and isn't supported anymore.

[thadman]

Originally Posted by jzagaja

Dear Dr. Geddes,


Can you give some insight into practical Acoustic Lever (AL)? It is meant to be an alternative to bass horn. Speak software that simulates such enclosure doesn't work with non-US Windows and even then it does not load databases and projects with AL so it's useless.

How should we calculate those three volumes, compliances and masses?

What is known driven diaphragm should be slightly smaller then driver and radiating slightly bigger. Maximum ratio 2:1. I'm most interested in rear AL so that we extend bandwidth rather than gain efficiency.

Fundamentally, it is a transformer, so it should function similar to the bass horn.

I believe Dr. Geddes' research with regards to Acoustic Levers can be found in his book "Audio Transducers".

Here is a link to an article published by Dr. Geddes ("The Acoustic Lever Loudspeaker Enclosure").
http://www.aes.org/tmpFiles/elib/20091201/12118.pdf

[MaVo]

I am just a little curious... This acoustic lever sounds like such a great thing, but why has noone ever build one and posted about it?

[J.R.Freeman]

From what I can see, the device above appears to operate in a similar fashion to how a contemporary automotive hydraulic brake system works. The trade-off is excursion at the input for increased force at the output. An interesting concept, perhaps its goal is to better couple the driver's cone to the air-filled universe. A sort of mechanical impedance matching.

I would wonder at the mechanical losses imposed by such a system? That schematic, which I think is supposed to be the equivalent circuit expressed in electrical terms, is missing some resistors!

Jim

edit: having just Googled the device name, I now realize that it is Mr. Geddes design. I will shut up then and let him explain it, should he chose to do so! :P

[gedlee]

Originally Posted by jzagaja

Earl come on

Impatient aren't you. Mind if I go out for the evening? And "useless" - SPEAK works fine for me, and I don't "sell" it any more, so I don't support it. Finally, everyone else is correct, there is plenty of literature out there about it. Read that first and then ask your questions.

But extending the bandwidth won't work, that's not the levers strength. Improved efficiency is and trying to make it do anything else is going to be a dead end.

Nothing is going to beat a direct radiator for bandwidth. All designs are efficiency/bandwidth tradeoffs.

And it is just like a brake system and if you used fluid inside instead of air it would work even better!

[gedlee]

Originally Posted by MaVo

I am just a little curious... This acoustic lever sounds like such a great thing, but why has noone ever build one and posted about it?

We built several years ago at Ford. They were written up in SAE articles on automotive subs. They worked great. Reliability of the lever itself could be an issue because it gets a pretty good workout.

[tinitus]