Ricci's dual B&C 21SW152 build thread.

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Sorry in advance. This is going to be a long post. :eek:



Last Thursday I got a twitchy index finger and ordered a pair of these drivers after looking at them for a long time. The other contender's were 18Sound's 21NLW9600 and the TC Sounds PA5100. I could not seem to locate the 18Sound and the pricing would've undoubtedly been much higher. I was thinking about trying the TC when I found an incredible price on the B&C. $579.95 plus $25.50 shipping each. $605.45 shipped. That's a little over $100 cheaper than anywhere else I'd seen them. Had to purchase a pair while the getting was good.

http://www.bcspeakers.com/PDF/PRD/21SW152.pdf

Here if anyone is interested. They have some other B&C stuff for cheap as well.

Buy B and C 21SW152 Professional Speakers for $579.95

It's a ghetto looking operation but apparently they've been in business for a long time and have a good rep. I guess I'll find out. :rolleyes: The drivers are due to arrive tomorrow.


These will be used in a PA type manner usually in a fixed location for drum reinforcement, some bass guitar and music playback, but they may ocassionally be dragged out for duty at local concerts, so they can be big but have to be manageable by just 2 guys. 600L is the limit I decided on. I'm only looking for full response from 100-120hz or so down to 25-30hz at which point they'll be hpf'd. Maximum loudness and fidelity over that range is the order of the day. I've got a few preliminary ideas for the cabinets these will go in, but I'm undecided still. Part of me wants to go for a regular old ported build because it's simple, relatively small and I could run the cabs up quite a bit higher than 120hz if there was a need for it. The other part says to try a horn build, whether to try a TH or a FLH though? Each approach seems to have some advantages.

I'll post my current simulations below. All sims are in 4.0pi space (anechoic) I'll be using a bridged Crest 8002 on each drive which is rated at 4000w into 4ohm. The RE of the driver puts the minimum impedance of any of the cabs in the 3.5ohm range which should end up near 4ohm minimum in reality. 117v is just under 4Kw into the minimum impedance. The amp should be able to easily deliver more voltage into the higher impedances (rated at 130v peak per channel).


I'm looking for constructive criticism guys. Give me some input :) Got something that looks better than the sims that I have? Post it up please.
 
Ported


Interestingly the peak near port tuning is much more pronounced in HR than with Unibox or WinIsd. I'd like to make that a little smoother, but I feel it may not be so pronounced in reality and it is already going to be very difficult to fit enough port on these drives without making the cab smaller. I figure about 75sq in of port is the minimum for these drives, which is a 10" port. This is a 27.5hz tuned 10cu ft (283L) cab with 117v input.


21sw152ported275.jpg

21sw152ported275FR.jpg

21sw152ported275displacement.jpg
 
FLH

This is a rough sim that I've got. 600L 30hz. I'm not an expert at horns by any stretch so let me know if something is glaringly wrong. I'm not sure how feasible this is to build in reality either, I'll deal with that later. The compression ratio is 4-1 which may be too high for a 21" drive? I can switch to a 3.36-1 compression ratio without too much change to the cab size/response. Again this is at 117v in.



21sw152preliminary30hzFLH.jpg

21sw152preliminary30hzFLHFR.jpg

21sw152preliminary30hzFLHdisplaceme.jpg

21sw152preliminary30hzFLHimpulse.jpg

21sw152preliminary30hzFLHphase.jpg
 
How about a compound horn?

Hi Ricci,

We played around a little with the 21SW150 in the collaborative and the PA (screamer) TH thread early in 2009. I think you are on the right track with your simulations. In the tapped horns it generally helps the impulse response to either set S1=1 after you have basically optimized your simulation, and/or to try increasing S5 to a larger value without altering any of the other parameters (for these changes, and in general, I recommend using all four sections in Hornresp, it's there, it's free, ...... :)). The frequency response of the 21SW150 simulations responds well to even small amounts of series inductor (e.g.: Rg=.1 / Le= add 2mH). There seems to be a difference in the driver parameters from a year ago, I would not spend too much time in Hornresp without having measured the actual drivers. Also, one type of enclosure that David McBean has added to his loudspeaker wizard seems to find little use: the compound horn enclosure, I'll attach a quick try for reference.

Regards,
 

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  • 2010_Apr05_21SW150_compound.jpg
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TH Losses

Hi Ricci,

Just one more thing. Tom Danley mentioned that Hornresp does not account for losses at high power levels, and there seems to be a general scheme that works e.g.: in the TH-SPUD: S1 about 1/2 Sd, S3(S4) about Sd and S4(S5) about two times Sd. This results in a bit larger response variations, but may be something to keep in mind.

Regards,
 

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  • 2010_Apr06_21SW150_chambered_TH_600L.jpg
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Hi Ricci,
there seems to be a general scheme that works e.g.: in the TH-SPUD: S1 about 1/2 Sd, S3(S4) about Sd and S4(S5) about two times Sd. This results in a bit larger response variations, but may be something to keep in mind.
In the TH-Spud the S1 is equal to ~Sd, S2 is ~Sd x.5, and S3 would be ~Sd x1.75.

With four segments change S3 to x1, S4 x1.5, and S5 to x2.
 
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Cant believe I wasn't around when you posted this.
Just got finished building 4 Apache H15's (TH's)
I have a TH for these subs. Here is the HR date:

ID=23.40
Ang=2.0 x Pi
Eg=60.00
Rg=0.00
Fta=4.03
S1=336.00
S2=880.42
Con=10.00
F12=0.00
S2=880.42
S3=5000.53
Con=500.40
F23=0.00
S3=5000.53
S4=6000.00
Con=54.00
F34=0.00
S4=0.00
S5=0.00
L45=0.00
F45=0.00
Sd=1680.00
Bl=32.60
Cms=6.30E-05
Rms=10.70
Mmd=437.80
Le=1.30
Re=3.30
TH=2P
Vrc=0.00
Lrc=0.00
Ap1=0.00
Lpt=0.00
Vtc=0.00
Atc=0.00
Com=FlipC -TH 221 Clone B&C 21SW150 4 Ohm 1500w 15mmXmax 60v

Good down to 18Hz at 125.5 DB !
130 DB at 20 hz.
Design has plenty of room to play with power also though that is at a respectable power level for such big drivers.

Something I will build myself one day! I cant afford to right now.
 
soho54
A bit give an take there.
I went on the assumption of having a small dip. Seemingly they get filled in the real world.

I did another where the Impedance is exact to the DLS TH 221.
Though the output isn't the same. Not good at all really. I am left to think that DLS has something not so easy going on inside of their bigger TH's.
 
Hey guys. I've got the 8ohm versions. Here is the PDF. I put a dmm to the drivers last night and they both come out exactly at 6ohms. the modeling doesn;t appear too much different.

View attachment 21SW152-8.pdf


Here are some notes I reported over at AVS.

I also free air tested both to see if there were any issues. I decided to push them fairly hard in the mean time. They are really clean and noise free up to what looks like about the rated xmax 25-30mm p2p they start to make some suspension noises past there and a good amount of air noise from the motor. I pushed them on up to maybe 40-45mm p2p at which point there is a large amount of self noise from the suspension and motor vents. The amount of air coming out of the back of the motor is very impressive. Should be some good gap/vc cooling going on there.

Interestingly I was using a single channel of a QSC PL9.0 during this free air test and a 10hz sine as it provided the most excursion with the least amount of volume. The single PL9.0 channel hits hard clipping before the speaker gets in any danger of bottoming. Figuring that it's probably about a 9ohm load at 10hz that should be somewhere north of 1600w of a 10hz sine wave in free air producing about 40mm p2p. It appears that these are not an easy driver to get into excursion trouble which makes me happy, as I was worried about that if used in a sealed alignment with LT(which a lot of people talk about). The suspension appears to rapidly put the brakes on at around 20mm one way judging by the behavior of the last couple of volume increases. I'd guess that you'd have to break something in the suspension before reaching 30mm and hitting the back plate.
 
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