I've updated my blog with my latest project.
Joseph Crowe's DIY Speaker Building Blog: B&C Sub 215 (Dual 15") project
Joseph Crowe's DIY Speaker Building Blog: B&C Sub 215 (Dual 15") project
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Joseph,
In your blog you wrote:
"The great thing about the B&C plans are very high maximum SPL (140db) and great low frequency extension, and great efficiency (103 db/1watt)."
Looking at the speaker plan you reference, it does have those peak specifications, evidently taken at around 1800 Hz where the BC15PS100 has a 5 dB peak.
The actual 2 volt one meter sensitivity in the sub range above Fb to 100 Hz is 96-98 dB as their chart clearly shows.
Excursion limited SPL for the dual 15" cabinet would be around 124 dB, up around 100 Hz it should do around 128 dB at it's thermal limits.
Cheers,
Art
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that right there is exactly what I just use formulas for T/S-based 1W/1m sensitivity.
If IIRC, the expression is 112.2 + 20*log (2.77e-7*Vas*Fs³/Qes). No BS marketing gimmicks.
If IIRC, the expression is 112.2 + 20*log (2.77e-7*Vas*Fs³/Qes). No BS marketing gimmicks.
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Using WinISD I get 97 db with two drivers for the 15PS100, and 99.2 db with the 15NW100 both at 1 watt. Maximum SPL for the 15PS100 is 129 db @ 1,400 watts (700 x 2), the 15NW100 shows 132.2 @ 2,000 watts. The published maximum long SPL from B&C is 134 db. B&C is close on the Maximum SPL, but I'm not sure where they are getting 104 db @ 1 watt. BS marketing?
you could call it that, simply because they are not disclosing at what frequency/frequency range the measurement is made. To me, that is deceptive because many people think that it will do 104 dB with 1watt at any frequency from DC to light (even if they don't know what that means 😛)
Joseph,
Your simulations agree with the frequency response graph B&C shows with the plans you used.
As I already mentioned in post #3, the 103 dB sensitivity would be correct at 1800 Hz, where the speaker has a 5 dB peak.
Unfortunately, many manufacturers do use peak values that are far out of the intended pass band for the subs intended use.
I would not call it marketing BS, since the FR chart clearly shows what the level is at frequencies of interest.
What does WinISD say the maximum excursion is for the 15PS100 at 1,400 watts ?
How many watts will the cabinet take without the 15PS100 exceeding Xmax?
Art
That 2x18" sub is 101 at 100 Hz, but 97.5 at 40 Hz, and about 94 at 35 Hz.
One of those eighteens in my Keystone sub design will do about the same level.
Art
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Joseph Crowe's DIY Speaker Building Blog
fig.1 Max calculated SPL for 1 loudspeaker@1m (± 8.00 mm) (does not account for thermal effects), look at first column for one speaker, SPLt=127.9 dB, V=59.03 V (Note: Suggested Design Sub Limit 35 Hz).
fig.2 Also I think they used this formula for T/S Xmax (I give the link).
XMAX.HTM --- Part of Manual for Driver Parameter Calculator --- by Claus Futtrup.
How does B&C calculate the Xmax (excursion) specification, and what is Xvar?
fig.1 Max calculated SPL for 1 loudspeaker@1m (± 8.00 mm) (does not account for thermal effects), look at first column for one speaker, SPLt=127.9 dB, V=59.03 V (Note: Suggested Design Sub Limit 35 Hz).
fig.2 Also I think they used this formula for T/S Xmax (I give the link).
XMAX.HTM --- Part of Manual for Driver Parameter Calculator --- by Claus Futtrup.
How does B&C calculate the Xmax (excursion) specification, and what is Xvar?
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This is the alignment used
2xB&C 15 PS 100, VB = 300.0 L, FB = 40.0 Hz, 97.5 dB2.83Vm.
F3=36Hz F6=33Hz F12=28Hz F24=20Hz
30 Hz -13.5 mm cone displacement
I would prob. go to this one (lower freq.).
2xB&C 15 PS 100, VB = 300.0 L, FB = 32.3 Hz, 97.5 dB2.83Vm.
30 Hz -4 mm cone displacement / 25 Hz - 13.5 mm.
F3=33Hz F6=29Hz F12=24Hz F24=17Hz 😀
2xB&C 15 PS 100, VB = 300.0 L, FB = 40.0 Hz, 97.5 dB2.83Vm.
F3=36Hz F6=33Hz F12=28Hz F24=20Hz
30 Hz -13.5 mm cone displacement
I would prob. go to this one (lower freq.).
2xB&C 15 PS 100, VB = 300.0 L, FB = 32.3 Hz, 97.5 dB2.83Vm.
30 Hz -4 mm cone displacement / 25 Hz - 13.5 mm.
F3=33Hz F6=29Hz F12=24Hz F24=17Hz 😀
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Box Volume
To be fair the internal volume is smaller than the projected 300L, closer to the ideal size/int. volume for both drivers. I calculate each (x2) handle box to be ~23.6 centimeters by 20 centimeters by 12 centimeters. (= 5.664 liters)
Fb/Internal Volume 300 L - 12 L = ~282L
To be fair the internal volume is smaller than the projected 300L, closer to the ideal size/int. volume for both drivers. I calculate each (x2) handle box to be ~23.6 centimeters by 20 centimeters by 12 centimeters. (= 5.664 liters)
Fb/Internal Volume 300 L - 12 L = ~282L
Inductor,
The B&C 15PS100 has only 8mm Xmax, how many watts/volts does it take for a pair to hit that above Fb in a 300L 40 Hz Fb box?
Art
Inductor,
My Portuguese is no good, but it looks like with 60.42 volts (912 watts in to four ohms) this design will hit Xmax at about 53.6 Hz at 128.1 dB, power compression ignored.
That's 4 dB better than my guess in post #3 which was based on B&C's 100L 40Fb single driver cabinet which shows a excursion limit maximum 1 meter SPL of only 118 dB, the extra 50L per driver makes a difference!
Thanks,
Art
My Portuguese is no good, but it looks like with 60.42 volts (912 watts in to four ohms) this design will hit Xmax at about 53.6 Hz at 128.1 dB, power compression ignored.
That's 4 dB better than my guess in post #3 which was based on B&C's 100L 40Fb single driver cabinet which shows a excursion limit maximum 1 meter SPL of only 118 dB, the extra 50L per driver makes a difference!
Thanks,
Art
yea, tuned around 40hz (assuming not much going in below that), you can hit serious serious spl's with 8mm drivers............
But based on that driver and box, you are 9db down around 30hz.
I'd call that a deep woofer, not a subwoofer.
But really good for a PA subwoofer (high spls for hours).
In a home for a subwoofer looking for depth extension, I'd like to see ported F3 at or below 27hz........... maybe 30hz F3 for a sealed.
Others like even lower F3's, but I'd rather not trade ported F3/tuning of 20hz for the excursion and the more often information around 30hz.
Then again a 3ft3 20hz ported epic 12 still stays under its xmax of 23mm with 600 watts (wow) from 20hz upwards.
Norman
But based on that driver and box, you are 9db down around 30hz.
I'd call that a deep woofer, not a subwoofer.
But really good for a PA subwoofer (high spls for hours).
In a home for a subwoofer looking for depth extension, I'd like to see ported F3 at or below 27hz........... maybe 30hz F3 for a sealed.
Others like even lower F3's, but I'd rather not trade ported F3/tuning of 20hz for the excursion and the more often information around 30hz.
Then again a 3ft3 20hz ported epic 12 still stays under its xmax of 23mm with 600 watts (wow) from 20hz upwards.
Norman
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Norman,
One can certainly afford to go much lower in a home theater than a PA situation where transport, storage and set up space dictate cabinet size, and in smaller venues, power is often inadequate.
The chart below illustrates what going from a 38 Hz Fb to a 28 Hz tuning in the same box size does (driver is a BC18SW115-4)-it would take almost two times the drivers, boxes and power for the 28Hz Fb to reproduce the 40-55 Hz range where most of the low stuff in pop music lives.
The 28 Hz tuning actually is only louder than the 38Hz tuning below 34 Hz, very near the low B on a five string bass.
I have found 35-38 Hz tunings to be the best compromise between output and extension now that the usual low string on a bass has gone from 41 to 31 Hz.
Art
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28hz tuning sounds better than 40hz to my ears, smoother. Less thunk thunk sounds. Hard to explain.
Hello, I am looking into building my own dual 15 reflex cab, I looked at Joseph's link for I am not seeing the plan for this cab, can you help please? Also, since this is a BNC design, would I be able to other woofers like Eminence kilomax Pro?
I guess B&C has updated their website and the link no longer works.
I've attached the plans for you.
In order to verify that the Eminence Kilomax will work you'll have to model it in WinISD and see the resulting frequency response.
I've received countless compliments on how well this sub sounds from a sound quality standpoint. It has great pitch definition, very clean and tight sounding.
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