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B&C 21SW152 and 21DS115 long term power handling
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logsquared1 View Drop Down
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    Posted: 16 September 2017 at 9:15pm
Anyone using the 21SW152 or 21DS115?  I have been using the 152's in a tapped horn for a few years on a crest 9001 (2200 W) with no problems.  I have also run the 152's from a bridged 9001 (6600 Wrms) on a few shows with live music. The SPL is amazing with the amp bridged.  Im not sure of the longevity on a bridged 9001 for trap, edm, etc. 

I am currently putting together a system for use at small to medium festivals.  At the moment i am designing a bent horn for 50-150hz that will use the 21DS115.  I have completed the prototype and am pleased so far with the sound.  Next I will be designing a 25-50hz box for under the bent horn.  It will most likely use the 152's.

Im probably going to use k20's on the bent horns and maybe the subs, but may stick with the 9001's on subs.

Now that I am moving up to modern amps I am wondering how to best set the long term limiters.  The idea of having 225 peak volts is really exiting and the drivers can certainly take it.  However the average level of this new dirty trap and bass music is very compressed and $300 recones is not sounding fun.  
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Points: 7845 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2017 at 11:04pm
They can certainly take tons of power, but, how long they will last, it is a different question. Pushing lot more then 2KW per driver will for sure start exhibiting power compression and you wont get much louder from that point even if you push 4KW to them.
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Originally posted by MarjanM MarjanM wrote:

They can certainly take tons of power, but, how long they will last, it is a different question. Pushing lot more then 2KW per driver will for sure start exhibiting power compression and you wont get much louder from that point even if you push 4KW to them.

One of the reasons I am so excited about the newer amp is the ability to have large voltage swings and limit the average power to keep driver heating down.  Should give more confidence when running hard.  

The box i built for the 21DS115 needs 160Vrms to even reach xmax in the passband.  Anything less would be wasting the driver.  For EDM in the past we undersized the amps and hard limited the subs for driver protection.  This I believe hurts the dynamics of the system.  Its always some guesswork to match the drivers and amps.   Hopefully, with the new amps I can find the balance without cooking too many speakers.
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Average power will be very dependent on the music material. Heavily compressed music will have bigger average power no mater which amp you use and how much headroom you have. 
I did some goa trance gig a week ago, the leds on the midhigh boxes were basically lit all the time with very little dynamic. Had to reduce a lot to prevent blowing up the HF. 
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logsquared1 View Drop Down
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Found this last night on powersoft's website: http://www.powersoft-audio.com/en/downloads/technical-notes/804-how-to-setup-limiters/file

Very interesting read.  They show some experiments that are pretty eye opening with regard to power compression.

They recommend ~1/3 AES for their "truepower" limiter.  That would put the 21DS115 at 566 watts. 
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a 21" for 50-150 Hz in a horn? why would you want a 21" to cover that area? cone area is not important in front loaded horns. i would use a 15" for that range.
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Originally posted by corell corell wrote:

a 21" for 50-150 Hz in a horn? why would you want a 21" to cover that area? cone area is not important in front loaded horns. i would use a 15" for that range.

The 21DS115 is not a "normal" 21". 

 Im not sure what you mean "cone area not important" ?  More displacement should equal more SPL?  Am i missing something?
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You dont need that much cone area for 50-150hz, you will not really achieve more output and you would probably get a better sound with a 15". The price difference should also be quite significant
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Sure. But finding 15" with so much power and cone excursion for mildly unloaded horn is very hard. But 18DS115 should be better for that task. I do agree that 21" for 50Hz horn sounds like something is not right. The 21" could even not move enaugh and burn the coil edges soon.
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Originally posted by logsquared1 logsquared1 wrote:

Originally posted by MarjanM MarjanM wrote:

They can certainly take tons of power, but, how long they will last, it is a different question. Pushing lot more then 2KW per driver will for sure start exhibiting power compression and you wont get much louder from that point even if you push 4KW to them.

One of the reasons I am so excited about the newer amp is the ability to have large voltage swings and limit the average power to keep driver heating down.  Should give more confidence when running hard.  
.

You can still damage the driver by creating an offset which will lead to the voice coil rubbing against the magnetic plate.

Best Regards,  
Elliot Thompson
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Originally posted by turbo7 turbo7 wrote:

You dont need that much cone area for 50-150hz, you will not really achieve more output and you would probably get a better sound with a 15". The price difference should also be quite significant

Simulations are saying otherwise.  Also, I A/B tested my prototype against 3 X HD215's eq'ed to match as closely as i could get.  The hd's are loaded with EV DL15X's (EBP = 140).  The single 21 had no less "punch" than the 6 X 15's.  Sound quality was very good.  Obviously the the 6 15's were louder but not by much.  And the 21 when not eq'ed went at least 10 cycles lower.  

Originally posted by Crashpc Crashpc wrote:

Sure. But finding 15" with so much power and cone excursion for mildly unloaded horn is very hard. But 18DS115 should be better for that task. I do agree that 21" for 50Hz horn sounds like something is not right. The 21" could even not move enaugh and burn the coil edges soon.

The 18DS115 looks like a nice woofer.  However, the 21 is a much more efficient driver.  I should have mentioned I plan on using the box as a general purpose sub down to 40 cycles for non EDM gigs.  The extra surface area should be helpful here.  Good point on the possible thermal problems if the cone is not moving enough.  That kind of goes back to my original post..... What long term power are people putting to these things?

Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by logsquared1 logsquared1 wrote:

Originally posted by MarjanM MarjanM wrote:

They can certainly take tons of power, but, how long they will last, it is a different question. Pushing lot more then 2KW per driver will for sure start exhibiting power compression and you wont get much louder from that point even if you push 4KW to them.


One of the reasons I am so excited about the newer amp is the ability to have large voltage swings and limit the average power to keep driver heating down.  Should give more confidence when running hard.  
.

You can still damage the driver by creating an offset which will lead to the voice coil rubbing against the magnetic plate.

Best Regards,  


Not sure I follow.

Anyone have any real world experience with the 21DS???
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Well it all depends exactly on the loading, content (program power), cone excursion, cooling, cone pressure and more.

I do own one piece of 21DS115, and while I'm more likely to use full excursion more often, I now feed it 1400-1500w (mildly clipping amp).
If I was to use its maximum thermal capabilities, I'd go 2500w with DSP and clever limiter. I know people feeding 3000w or more into 21SW152. The coil surface area is not much bigger here, even with 6" coil. And those speakers handle it when driven right.
As I said, it all depends.
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