Most rugged midrange compression driver

[BillyDoc]

Good morning Gentlemen!

I'm trying to develop a test chamber with a very high level internal acoustic environment (140 dB, 2Hz - 8KHz) and can't seem to locate a midrange driver that can survive it. Right now I have eight Pyle Pro PBD832 mounted to provide the range from 300 Hz up . . . and they lasted exactly 5 seconds at 138 dB.

The Pyles were under power at 225 watts (they're rated at 1000, but the amp can only develop 225), so I don't think I'm electrically heating them to destruction.

I have an extra Pyle and just took it apart to see what was inside and found a very lightly made plastic voice coil/diaphragm structure with what looks like brass tabs to bring power in. The slot that the voice coil is normally in was filled with some sort of brown oil, and if I didn't know this was a new driver I would have thought the thing was burned up, but it must be some sort of ferromagnetic damping liquid.

I think what is happening is that the acoustic energy from the low frequency drivers (4 Kicker Solo18, driven at 14,000 watts each in a 60 cubic foot chamber) is backing up the horns and ripping up the voice-coil assemblies in the Pyles.

At this point I'm pretty much limited to some driver with a 4 hole bolt pattern on a 4" circle.

Does anyone have any thoughts? Know any really rugged drivers?

Thanks!

BillyDoc

[BillyDoc]

How about the BMS 4592ND-MID? It's right pricey, for sure, but will it take some abuse? Does anyone have experience with it?

[Pano]

How about the stuff made for public address, like the EV, Atlas, Dayton, MCM, etc. They are made for mids and are rugged. They don't go much above 8KHz, tho. Generally they use phenolic diaphragms.

They are screw, but adapters are not expensive.

[BillyDoc]

Good idea, panomaniac! I'll look into those today. 8KHz is high enough for my purpose.

[bear]

what is the purpose of this??

Making hamster ears bleed??

Getting 140dB even nearfield is a non trivial exercise. Figure out the power handling of the driver & the sensitivity and then add in the power required to make the requisite power levels and you will quickly see the problem.

If you look online you can find some solutions to this problem that were used for very very narrow bandwidths in LOUD environments (aircraft carriers for example). They look like V-12 race engine intake manifolds. Anyhow at one time I ran across some things about this - and saw a cool piece on ebay at one time made for the military...

I doubt that any of these standard issue consumer compression drivers will permit you to reach 140dB, even in a closed box... even an array of them, maybe with a sufficient number... then you have some issues with interference... but...

So what is this for??

_-_-bear

PS. if you clip the amp, you will quickly destroy most drivers at that level... and NO WAY is that Pyle compression driver rated at 250watts... much less 1000. Something wrong with that picture.

PPS. Ok I looked it up - they DO rate it for 500watts RMS... seems impossible to me. Ferrofluid or not.

[bear]

And they are only rated from 800 Hz up... derate as you go below that frequency by a lot, assuming the diaphragm can physically do it (unlikely)...

Community Light & Sound used to make an 8" diameter diaphragm midrange compression driver....

Also, what sort of horn did you try to use to make 300Hz?? How did you load these drivers??

[BillyDoc]

Hi bear,

Only modest amounts of blood have been lost so far, mine during construction! But I'm happy to report that we did succeed in achieving 140 dB with a flat spectrum from 4Hz to 8KHz for six seconds. After about five runs the mids all got very quiet, however. We also have very good control of that spectrum, down to third octaves.

The purpose is a "Noise Stress Test Chamber" to be used to stress-test equipment that is deployed near a rocket launch. At about 50 feet the noise level is over 160 dB, but the top 20 dB can be eliminated with sturdy cabinetry, leaving the internal equipment at the lower sound level. The six seconds is because the rocket should be gone by the end of that time. If it isn't the noise level is often way higher, for a brief period. A big "boom" in other words.

I think the voice coil assemblies are going to be "consumables" for this machine.

BillyDoc

[Pano]

You're welcome! They may not be what you need, but at least it's worth a look. Remember, most of them are for 70V systems, so you'll have to bypass the 70V transformer.

You may find that nothing will stand up to your use. Back in the old days, they used to build manifolds and use 2 or more drivers to achieve higher spl with compression drivers. Take a close look at the speakers hanging off the choppers in Apocalypse Now. They are using 12 drivers on a single horn! (like Bear's V-12)

[Pano]

Thinking about your insane rocket launch levels, you may be on to something with the bass coming back up the horns to destroy the diaphragms.

We need to get GM onto this thread, he has built some super loud warning horns.

[BillyDoc]

bear,

I missed your question about what horn, they were all Selenium HL14-50 2" Exponential Horns, 45x45 4-Bolt.

I'm still looking for PA drivers, the best I've found so far is a MCM rated at 100 watts. Which has me thinking about a manifold, panomanic. I do have a space problem though.

BillyDoc