how to obtain a very high SPI using piezo transducers

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Ankh - 26 Jun 2005 08:09 GMT

posted cross
uk.rec.audio,rec.audio.pro,rec.audio.tech,rec.audio.opinion,rec.audio.misc,alt.sci.physics.acoustics,

I am wanting to reach 130+ DB using super tweeters or horn drivers
using 1kH - 25kH variable ultrasonic transducers or tweeters.

firstly, i've looked at three sound devices, and want some input re
these.

#1 is cheap & low power consumption;
http://amazing1.com/parts.htm (MOTRAN)

#2 is a full supertweeter, with voice coil
http://www.electronicheadquarters.com/detail_id94310.aspx

#3 is just a driver, is expensive, but offers the highest SPI;
http://www.midi-classics.com/h/h28484.htm

any idea as to what the power consumption of #1be?

the horns;
http://www.cinematech.info/manuals/Sound/Speakers/JBL/pub/components/23525354.pdf
are quoted as having maximum 115DB sensitivity.
What sort of SPI should I expect from coupling #3 with such a horn?

when #3 is quoted as just 2000 watts max, without giving any other
operating RMS value, should i expect that the driver can operate
continuously at 2000watts?

& is it possible to have only 3DB difference between #2 & #3, when
there is so much difference in the power input?
I was thinking that maybe the SPI values they quote are sometimes too
generous or sometimes too conservative.

How is it possible that the in-car alarm & even keychain personal
protection noise-makers are in excess of 130DB?
Can this have a lot to do with the construction of the siren housing?
and that they warble, rather than are variable?

in going above 120DB, my thinking is to couple some devices together.

one thought is to use the big ear parabola to focus an array of
devices or horn output.

The other thought is to use a simple array of devices together
pointing in a similar direction.

The other thought was to couple several drivers together into the
construction of a unity horn like device

any thoughts about coupling horns?

would i lose power in coupling multiple drives into a unity horn?
& is there any specific mechanics applied in distance and placement in
the arrangement of the drivers that is good or bad for obtaining the
optimal output?

I've also been thinking about constructing an air transducer. does
anyone know of any good source of info re the construction of piezo
transducers?

All comments and criticism welcome
grrr@post.com

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Scott Dorsey - 26 Jun 2005 12:55 GMT

>I am wanting to reach 130+ DB using super tweeters or horn drivers
>using 1kH - 25kH variable ultrasonic transducers or tweeters.

Try a compression driver into a sealed tube. You're going to have to
work out some sort of labyrinth to avoid standing waves, but a JBL
horn driver going into a sealed tube should have no problem producing
that sort of level for a few inches.

>How is it possible that the in-car alarm & even keychain personal
>protection noise-makers are in excess of 130DB?
>Can this have a lot to do with the construction of the siren housing?
>and that they warble, rather than are variable?

They are very narrowband. It's easy to build something with a lot of
output if you don't want to to be narrowband. The Mallory Sonalert is
typical of these devices.

>in going above 120DB, my thinking is to couple some devices together.

If you double the amount of devices, you get a 6 dB improvement. It
takes a huge array to get much improvement, and of course now you get
interference issues.

>one thought is to use the big ear parabola to focus an array of
>devices or horn output.

This doesn't mkae it any louder, it just makes it directional.

>All comments and criticism welcome
>grrr@post.com

What are you trying to do? You want 130 dB a few inches away from the
driver in a sealed box for transducer testing? Or you want it fifty
feet away? The latter is much more difficult to do.
--scott

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"C'est un Nagra. C'est suisse, et tres, tres precis."

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Ankh - 07 Jul 2005 05:48 GMT

Hey, this stuff takes years to respond to, so bear with me..

Many thanks for the input.

now, how do i couple 5x 4-input adapters, that go from one inch thread
to just the one two inch throat, but using 1&3/8inch-thread drivers to
power just the one two-inch throated horn?
Would that sound too crazy?
Or should I stick to 5x separate horns?

I don't know the accoustic dynamics too well.
I'm guesing that the wave forms are spreading out like a shockwave,
and can only propogate a few inches. or something.

I'm also looking at Lecleac'h curves.

thanks

>>I am wanting to reach 130+ DB using super tweeters or horn drivers
>>using 1kH - 25kH variable ultrasonic transducers or tweeters.
[quoted text clipped - 31 lines]
>feet away? The latter is much more difficult to do.
>--scott

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Scott Dorsey - 07 Jul 2005 13:56 GMT

>now, how do i couple 5x 4-input adapters, that go from one inch thread
>to just the one two inch throat, but using 1&3/8inch-thread drivers to
>power just the one two-inch throated horn?

With a Y connector machined out of aluminum.

>Would that sound too crazy?
>Or should I stick to 5x separate horns?

It seems like a silly idea to me, but Altec did it. You get all sort
of alignment issues at high frequencies.

>I don't know the accoustic dynamics too well.
>I'm guesing that the wave forms are spreading out like a shockwave,
>and can only propogate a few inches. or something.

There is a nice discussion of this in the AES Speaker Compendium.

But if you put it into a horn, it's not in a sealed tube any more.
The secret to getting high levels is to keep the driver and the
thing you're exciting in a sealed tube.

You still have not explained what you want this for.
--scott

Signature

"C'est un Nagra. C'est suisse, et tres, tres precis."

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Ankh - 07 Jul 2005 05:49 GMT

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Clyde Slick - 26 Jun 2005 13:16 GMT

> posted cross
> uk.rec.audio,rec.audio.pro,rec.audio.tech,rec.audio.opinion,rec.audio.misc,alt.sci.physics.acoustics,
[quoted text clipped - 59 lines]
> All comments and criticism welcome
> grrr@post.com\

Does all this have something to do with Gitmo?

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Natural Science Forum / Physics / Acoustics / July 2005

how to obtain a very high SPI using piezo transducers