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Old 11th January 2013, 04:25 PM   #1
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Default Dual 15" Subwoofer project complete

I've updated my blog with my latest project.

Joseph Crowe's DIY Speaker Building Blog: B&C Sub 215 (Dual 15") project
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Old 11th January 2013, 05:50 PM   #2
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Looks nice, congratulations for the presentations.
You have to love the handles.
It looks like a pseudo Onken Style too.
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Old 14th January 2013, 07:46 PM   #3
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Quote:
Originally Posted by twin turbo View Post
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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Old 14th January 2013, 08:11 PM   #4
OscarS is offline OscarS  United States
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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.

Last edited by OscarS; 14th January 2013 at 08:16 PM.
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Old 14th January 2013, 10:50 PM   #5
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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?
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Old 14th January 2013, 11:06 PM   #6
OscarS is offline OscarS  United States
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Quote:
Originally Posted by Joseph Crowe View Post
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 )
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Old 14th January 2013, 11:47 PM   #7
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I think it's a mis-print because the plans for the SUB 218 shows only 101 db @ 1 watt.
B&C SPEAKERS
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Old 15th January 2013, 02:03 AM   #8
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Quote:
Originally Posted by Joseph Crowe View Post
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?
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
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Old 15th January 2013, 02:11 AM   #9
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Quote:
Originally Posted by Joseph Crowe View Post
I think it's a mis-print because the plans for the SUB 218 shows only 101 db @ 1 watt.
B&C SPEAKERS
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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Old 15th January 2013, 02:50 AM   #10
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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?
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