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B&C 21SW152-4 ... My Funny Valentine has arrived!

6850 Views 69 Replies 12 Participants Last post by  kramskoi
Happy Valentine's Day! Just got the 21SW and the UMIK from MiniDSP. The iNuke 3000 should arrive in a few hours. So $1k in a day I guess

After reading too much about this device, I just couldn't help but pull the trigger. I plan to put the suspension through a similar protocol as the 18SW115 last year (40 hrs at 10Hz / 1" peak to peak). Ricci noted that the Fs and consequent cms were both off specs when fresh. So how long do I beat on it until it gives? I will check Fs with the analyzer before I put it to sine. Can't wait to see if it is as quiet as the 18SW in free air.

Nothing against the RCF, actually I had an LF21N551 on order but it was a 3 week wait, so maybe it was fate to have this thing in my possession. Two of them in 5.5 - 6 cu. ft. should get over the LMS 18", which is the ultimate goal. Yes...I can hear it now...why not just buy an LMS. Short answer? I have my reasons.

I have held off on the 21SW152 because I could not thoroughly understand how it could perform so well past its geometric xmax. The answer? A split-wind inside-outside voice coil. I also wondered how the 21SW115, with a taller coil wind can't post a higher xmax rating than the 21SW152. I think the answer is the sheer amount of BL associated with the 6" VC versus the 4.5" VC in the SW115. Unless I'm missing something.

In my post payment euphoria, I simply overlooked that the 21SW is a 4 ohm driver and the QSC usa900 will only deliver 4 ohm power into 2 channels...not bridged. So guess what? New amp. INuke 1000? Don't even think about it, but I'm not ready to go iNuke 6000, even though a dual-driver cabinet is now on the horizon. After doing some light reading on the iNuke 3000, I decided that it was the best course for now. More to come...

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looking forward to it...

interesting bit about the sw115 and the coil heights. i may look into that one...

Originally Posted by LTD02  /t/1517820/b-c-21sw152-4-my-funny-valentine-has-arrived/0_100#post_24357516

looking forward to it...

interesting bit about the sw115 and the coil heights. i may look into that one...
34 - 14 mm for the SW115 and 30 - 12 mm for the SW152. Flux density 1.15T for the SW115 and 1.2T for the SW152...flux density for the 21IPAL is 1.35T. I think someone seriously needs to be locked up for keeping it confined to OEM. A real shame that is.
The 21IPAL looks great, but the Bl at 19.1 (vs 32.5 on the 21SW152) looks like a lot to give up?
the proper measurement is Bl^2/Re.

rerun the numbers with that in mind and the enormity of the ipal motor will become apparent. :)
I took those Bl figures off the B&C website
Bl by itself is kind of meaningless. square the term and divide by the resistance. then compare those numbers. :)

ipal motor: 19.1^2 / 1 = 365

21sw152 motor: 32.5^2 / 3 = 352

ipal has the stronger motor.

it also has about 50% more excursion capability from the longer coil.

not sure why it is oem only. maybe designed for a specific company that asked for that. who knows.
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I see what you're saying..

I guess that 1 ohm coil does come in handy..

Who would have thought one would ever see a "pro style" woofer with 1 ohm impedance?

That used to be an "exclusive" car audio phenomena, back in the old skool days, with Orion Red & other "cheater" amps
Fs = 35 Hz...cold...

6:30 pm

1" peak to peak @ 10Hz

Since a certain office saw fit to close 1 hour earlier than normal (without notice), I won't get my hands on the iNuke3000 until 10 am tomorrow, which chaps my ### pretty good right now.
So I unbridged the QSC and have it running 2 channel, with the driver on one of them. I'll put the iNuke on it first thing tomorrow (after a free-air measurement). Hopefully I don't toast the QSC before then. It worked out pretty well before with the RCF, but that was 8 Ohms bridged. I have a small, high speed fan blowing through it and it is merely warm to the touch so I figure it will be okay until morning. I need to have the beast in the box by Sunday morning if I am going to have time to dial it in. Otherwise, school assignments will severely disturb the process.

The 21SW is a bit heavier than its little brother at 40lbs. but still pretty light for a 21" driver. Excursion noise is a little higher than the 18 but there is much more cone so it is to be expected. Had to back off the power a little because it is running a little warmer than the 18SW did. I can confirm what Ricci noted about free air excursion, past a certain point, there is no more, accompanied by a doubling sound. I can test this more agressively with the iNuke, but my guess is that the particular peculiarity will persist. More to come...
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Originally Posted by lukeamdman  /t/1517820/b-c-21sw152-4-my-funny-valentine-has-arrived/0_100#post_24359983

I love my two. Seem bullet proof.
Yeah...I was looking through your Othorn thread. Serious business I'd say...

Somehow I think I can get just a bit more from the driver by stretching it out and raising somewhat the CMS. Won't be easy though because it is pretty effin stiff! I'm at 5 hours right now, so still a long, long way to go. I checked out the GR Research article at the time I had the 18SW and that was the impetus for the 2 day burn-in. I just wish that IPAL was available in 4 ohms...or available period for that matter. What a driver!

I can't seem to find that silly ZOD 621D. Where in blue hell did that thing come from? I tried ProSoundWeb and it seems no one has even heard of it. The riddle of ZOD I call it...every search returns old clips from Superman II and "General Zod"
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wait a minute...ipal is only available to manufacturers. zod is a mysterious manufacturer. ipal cone looks like zod cone. no back photo of zod driver. t/s specs look similar.

only thing that seems different is 1 ohm vs. 2 ohm, but the other parameters appears to scale about right, i.e. bl is about 1.414 times higher etc.

that drive would kick some booty in a largish low tuned tapped horn and who would be working on such a thing... hhmmm..... :)
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just stuck in a gh for example, not level matched. light gray curve would be ipal. obviously it could be optimized, but the back of the envelope suggests it would do quite well.
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max spl would look something like this.

essentially, it would be a gjallerhorn on the low end and an othorn on the top end.

i feel like such a dope for not seeing this before.

then again, i'm not sure if any of this is reality.
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After 15 hours continuous ... 29 Hz at 1 hour off sine [10 Hz]

Another 9 hours to go and its done... So the QSC had no problems in the night. What is also noteworthy is that the doubling appears to be attenuated a bit on the edge of the excursion envelope. I will know more later tonight at the end of the burn-in.
I wonder if I should go through this break-in process with mine?

Even after 6 months of some pretty serious use driving with with 5kw amps, their Fs is still ~38hz.

Can anyone elaborate on the effect of a drivers Fs compared to the tuning frequency of a horn? I know you can obviously tune lower than the Fs and be fine to a certain extent, but since the Othorn has a 28hz corner, would it be beneficial to "break in" the B&C's to lower their Fs from ~38hz to closer to 30hz? I'm crossing them at 26hz.
Tapped horns benefit from a higher fs compared to tuning (unlike other horn variants). Because there is no rear chamber, a higher FS than tuning helps control in band excursion peaks. In the othorn the in band excursion peak is around 38hz, so having FS there is likely beneficial.
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