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Powering compression drivers

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Bogdan85 View Drop Down
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    Posted: 24 January 2023 at 2:57pm
Hi guys!

We are switching our compression drivers to 2 x BMS 4594ND 1.4" COAXIAL 16 + 16 ohm with manufacturer ratings of:

Sensitivity 118 dB
Nominal power handling 150 | 80 W
Max power handling 300 | 160 W
Bandwidth 300÷7000 | 6000÷22000 Hz

They also say: The large diaphragm excursion of max. +/-0,8 mm results in high output and increased power handling up to 1.300 W peak.

So.. I got some questions as me and my crew still have a lot to learn :)

What kind of power should the amp have to give it enough headroom? The driver has high sensitivity so I guess it doesn't need much to get loud, but the 1300 W peak got me wondering. Also, how do I approach setting a limiter on this? I'll get a pro to do it and time align/eq the new speakers, but I'd like to know the best approach anyway 

Also, for the mid section we use double 12" rated at 1000W and we are powering them with 1500W at 4 ohm from a channel of a Matrix STR 3000. We have 2 matrix amps so would it make sense to power the 1000W double with 3000W of the amp bridged at 8ohms just to give it more headroom?

Thanks!
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csg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2023 at 5:06pm
I use the same driver in one of my larger cabs.

For limiters i use

Way. Mid. High
RMS 29 / 21 volts 1 second attack 4 seconds release
Peak 100/ 72 volts 2 millisecond attack 64 milliseconds release

Above based on 16/16R drivers.

My smallest amp channels are good for 145V peak but anything that can offer clean peaks of 105V or greater will be fine.
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2023 at 5:20pm
this guide should help:

its possible to drive the transducer with a very high voltage (the 1300W figure) without it failing instantly but it will not last long.  To achieve high maximum SPL with signals like M-noise (which has a high crest factor in the HF) it can be beneficial to use amplifiers around 1kW on the compression driver however you need both a peak and an RMS limiter and you may even need an excursion limiter for the low end of the transducer. 
https://meyersound.com/product/panther/#overview (you can see the high power pascal modules in this speaker for the HF and 12" are the same).   
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Bogdan85 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bogdan85 Quote  Post ReplyReply Direct Link To This Post Posted: 25 January 2023 at 12:54pm
Thanks for the help guys!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 25 January 2023 at 1:12pm
worth pointing out that if your operating near the LF limit of 300HZ the horn you will need is massive and you will risk damage operating at high voltages and lower than the horn+driver combo is capable of.  An appropriately set -24dB/octave (4th order) high pass filter will protect the driver.  You can find where the excursion starts to rapidly increase by performing lower level THD sweeps and finding the point where it starts to increase with decreasing frequency.
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Conanski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 25 January 2023 at 3:11pm
Originally posted by Bogdan85 Bogdan85 wrote:

We are switching our compression drivers to 2 x BMS 4594ND 1.4" COAXIAL 16 + 16 ohm with manufacturer ratings of:

Sensitivity 118 dB

What kind of power should the amp have to give it enough headroom? 

What SPL is the rest of the system capable of generating? The bottom line is you only need enough output from the CD's to produce a balanced sound with the rest of the system and given thier high sensitivity it is entirely possible that requirement could be an almost insignificant amount of power by PA standards. For example if the average SPL of the sound system was 130db the CDs would only need 16w to keep up, but you would use a 160w amplifier to allow 10dB of peak headroom.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bogdan85 Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2023 at 2:36pm
Originally posted by kipman725 kipman725 wrote:

worth pointing out that if your operating near the LF limit of 300HZ the horn you will need is massive and you will risk damage operating at high voltages and lower than the horn+driver combo is capable of. An appropriately set -24dB/octave (4th order) high pass filter will protect the driver. You can find where the excursion starts to rapidly increase by performing lower level THD sweeps and finding the point where it starts to increase with decreasing frequency.

Not gonna go that low, but will keep in mind to check that. We're going to use them in the paraflex 2x12" mid/tops crossed around 800hz probably and fitted inside with a line array type waveguide or on top using 18sound xr1464


Originally posted by Conanski Conanski wrote:

What SPL is the rest of the system capable of generating? The bottom line is you only need enough output from the CD's to produce a balanced sound with the rest of the system and given thier high sensitivity it is entirely possible that requirement could be an almost insignificant amount of power by PA standards. For example if the average SPL of the sound system was 130db the CDs would only need 16w to keep up, but you would use a 160w amplifier to allow 10dB of peak headroom.

This makes things easier to get in perspective, thanks. 

We have a stack of 4 x superscoops(Void v18 - 1000w) and 4 x es18(BMS 18S430V2 -1200w) and we're changing the mid/tops to 2 x double 12" paraflex with BMS 12S430-500w as drivers. We'll have to check if this also can keep up with the rest, but at the levels we are usually playing, we didn't have problems in the older boxes and in the new ones they should be louder. 

I figured that with our system the CDs will not have to work very hard as it's not very big and usually we can't play it at 'war' levels anyway, as we kind of lack locations for that around here, but I didn't know much about setting limiters in place and was curious if the amp we have is appropriate for the job headroom wise. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2023 at 2:41pm
So what amplifier do you already have for the HF section?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bogdan85 Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2023 at 4:57pm
Originally posted by Conanski Conanski wrote:

So what amplifier do you already have for the HF section?

Ha.. knew I forgot something :))

We have a Crown XLS 602 that we used with the old CDs and a Matrix STR 3000 that we have as a backup for the mids(powered by another Matrix). This are our options for now to power the 2 x BMS 4594ND 16+16 ohm CDs.  Would appreciate any advice for future upgrades in this department also. If it would make sense to have the same make of amps for mids and highs.. I saw a Matrix STR2400( 2 x 720w at 8ohm) reasonably priced, if the Crown is too small for the task. 

Crown ratings: 
8-ohm Stereo (per channel) 370W
4-ohm Stereo (per channel) 600W
2-ohm Stereo (per channel) 840W
8-ohm Bridge-Mono 1,200W
4-ohm Bridge-Mono 1,680W
*1 kHz Power: refers to maximum average power in watts 
at 1 kHz with 0.5% THD.




Edited by Bogdan85 - 30 January 2023 at 7:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 31 January 2023 at 4:54am
At 16ohms the XLS602 would produce about 185w/ch which is perfect.
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