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Low weight compression drivers

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Hemisphere View Drop Down
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    Posted: 24 June 2013 at 8:59pm
Posting in 12v as I think the issue of finding quality drivers at sufficiently low weight is one we come up against a lot here.

I just bought a BMS 4524 for a project as it was advertised in the spec sheet as being 665g - in reality it weighs in closer to 790 which was a little disappointing but still very good. That's with a ferrite magnet though, and presumably at some stage a production model actually weighed 665g unless it's a misprint, so with neodymium and a minimised excess chassis it's concievable that compression driver technology could produce a driver with 113dB sensitivity and response from 1,000Hz up at less than 400 grams, which is pretty nuts! 

But I don't think anything like this exists at the moment.

Another winner I noticed from BMS is the 4593nd which gives response from 300Hz at silly dB/Watt and weighs about 2kg. Prohibitively expensive for most projects though, something like 500 pounds. 

Are there any other good options for light compression drivers around?
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 25 June 2013 at 3:00am
Celestion CDX1425 are minuscule, 390g, good for 3k+ only though
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Post Options Post Options   Thanks (0) Thanks(0)   Quote login4 Quote  Post ReplyReply Direct Link To This Post Posted: 25 June 2013 at 6:35pm
http://www.amazon.co.uk/Pyle-Pro-PDS222-25-4mm-Compression-Drivers/dp/B004HJ5BU4


maybe, not used it my self but been tempted for portable stuff

or 


anyone heard these?



Edited by login4 - 25 June 2013 at 6:44pm
CELTIC SUBSONIC SOUND SYSTEMS
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 25 June 2013 at 8:14pm
They look very similar to the Celestion device, but with threaded throats rather than a flange mounting. I've heard the Celestions and they sound very nice on an ellipsoidal type horn.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2013 at 1:04pm
Looks interesting but Pyle Pro has a bad name for making and selling junk, maybe they produce some good stuff too but I've read a lot more bad than good, and the 12 pound including postage price point isn't exactly reassuring, but at the same time for that price, probably worth a gamble!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2013 at 1:14pm
Originally posted by login4 login4 wrote:

http://www.amazon.co.uk/Pyle-Pro-PDS222-25-4mm-Compression-Drivers/dp/B004HJ5BU4


maybe, not used it my self but been tempted for portable stuff


I've been wanting to try that out as well in a mini CD or radial horn for the Boominator


Edited by Saturnus - 26 June 2013 at 1:14pm
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bitSmasher View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2013 at 11:56pm
Throwing the idea in to the mix, for discussion... Bill Fitzmaurice uses plastic piezo tweeters, cut and melded in to an array:
http://billfitzmaurice.net/DR280.html

I'm yet to hear them or even read a decent (relatively) objective review or see measurements (BFM polarises people, it seems)... but the piezo array would definitely be light. And for relatively low power applications, it might be OK?
Unfortunately the cost to source the parts here makes it too expensive for me to build one just for the sake of it.


Edited by bitSmasher - 27 June 2013 at 12:01am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 27 June 2013 at 2:02am
Cripes, are piezos that expensive in Australia? They're like $4 here (says currency converter) 

It's not too difficult to make piezos sound good but what surprises people is how loud they aren't, once you've got the feed to them properly filtered to cut the frequencies they don't play well (anything under 5k) and damp the system resonance (series resistor+parallel resistor = L pad). I used 10 Motorolas in a craptastic cable-tied spherical-section array to match up to a 12" Toa PA horn in the first incarnation of my 12v system, and the horn itself was being fed from a network with a big insertion loss (deep midrange dip filter to stop it sounding like a PA horn!). 
BUT once you get enough of them together, and sort all that filtering out they sound like tweeters, not piezos, and can actually reproduce music in a pleasing fashion.
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bitSmasher View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 27 June 2013 at 5:20am
Originally posted by studio45 studio45 wrote:

Cripes, are piezos that expensive in Australia? They're like $4 here (says currency converter)
About that here too, just buying 20+ is more than I'd like to spend on a throwaway experiment... but I'll easily spend that much on a weekend's boozing Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 27 June 2013 at 8:03pm
I considered piezos when selecting components but the weight difference vs quality compared to the 4524 made it no contest really. I can imagine having all that extra headroom + high end quality, and mounted to a proper horn with a far lower crossover point (looking at around 1000-1200hz), will be invaluable in cases where voice needs to be projected with high intelligibility over long distances.

Edited by Hemisphere - 27 June 2013 at 8:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SMP Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2013 at 12:29am
re PZT's the material they are made from is a Lead Zirconite in wafer form. they are essentionally purely capacitive as a load for an amp and cause slew rate limiting. adding several or banks of them worsens this behaviour. a reasonable network which can make them behave better as a load presented to the amplifier needs  little more than just a Capacitor and a blocking resistor despite what the app notes from Motorola will tell you. a standard 12dB or 18dB Oct filter with the PZT element loaded via an auto TX with suitable loading resistors helps a great deal by decoupling the load which as mentioned is almost purely capacitive thus preventing the slew rate problem which is more so the cause of the bad performance of the Amp/PZT interface.

another factor to consider is the efficiency of PZT's compared to electromagnetic transducers even if you get them to sound ok the relative efficiency is a further issue to cause problems though careful design of the aforementioned network can minimise this to some extent
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2013 at 5:16pm
Hemisphere, I presume you have seen the BMS 4547nd :)

Tony
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
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