Ricci's dual B&C 21SW152 build thread. - diyAudio
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Old 5th April 2010, 08:10 PM   #1
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Default Ricci's dual B&C 21SW152 build thread.

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



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. 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.
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Old 5th April 2010, 08:10 PM   #2
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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.


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Old 5th April 2010, 08:11 PM   #3
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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.



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Old 5th April 2010, 08:11 PM   #4
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600L 27hz TH



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Old 5th April 2010, 08:12 PM   #5
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Last one...


370L 30HZ TH

I sort of like this one due to the size, but I don't know how realistic it is to actually build this cab. It loses a lot of efficiency, but it still beats out the vented by 3db over most of the range in a cab nearly the same size.


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Old 6th April 2010, 05:04 AM   #6
tb46 is offline tb46  United States
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Default 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,
Attached Images
File Type: jpg 2010_Apr05_21SW150_compound.jpg (30.6 KB, 48 views)
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Old 6th April 2010, 03:32 PM   #7
tb46 is offline tb46  United States
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Default Chambered TH

Hi Ricci,

I'll attach a chambered 400L TH (about the same as your 370L).

Regards,
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File Type: jpg 2010_Apr06_21SW150_chambered_TH.jpg (34.8 KB, 42 views)
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Old 6th April 2010, 05:10 PM   #8
tb46 is offline tb46  United States
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Default 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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File Type: jpg 2010_Apr06_21SW150_chambered_TH_600L.jpg (49.5 KB, 34 views)
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Old 6th April 2010, 06:18 PM   #9
soho54 is offline soho54  United States
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Quote:
Originally Posted by tb46 View Post
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.

Last edited by soho54; 6th April 2010 at 06:32 PM.
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Old 6th April 2010, 07:07 PM   #10
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Thanks TB46.

It seems that the main concern is keeping the compression down. I've not modelled any compound horns yet. I'll give it a shot and see. So far I'm leaning towards trying the small TH or just ported. I'd like to keep the size closer to 400l than to 600L.
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