★★Reflex Designs for PD/PDN 2450 ★★ - diyAudio
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Old 22nd September 2015, 10:17 AM   #1
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Default ★★Reflex Designs for PD/PDN 2450 ★★

Well the band is wanting to be unique so we can get
2...PD 2450
2...PDN 2450

Specs seem the same just weight difference. ..
For ease of building can do 10-16ft3/driver front loaded with vent..
We will mate these with 8 JBL 2241 tuned to 40hz allowing these 4 badboys to handle the heavy 30's hz..
Power will be Lab Gruppen FP6400
I have 2 FP6400 currently


Any ideas or comments welcomed
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Old 22nd September 2015, 01:20 PM   #2
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If you're only after a 10Hz bandwidth, I'd go for a 4th order bandpass, with the port pointing at the driver's magnet for lots of ventilation.

Make sure vents are big enough to keep air velocity reasonably low.

Chris
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Old 22nd September 2015, 02:16 PM   #3
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30 to 80
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Old 22nd September 2015, 05:24 PM   #4
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Quote:
Originally Posted by mclsound View Post
Well the band is wanting to be unique so we can get
2...PD 2450
2...PDN 2450

Specs seem the same just weight difference. ..
For ease of building can do 10-16ft3/driver front loaded with vent..
We will mate these with 8 JBL 2241 tuned to 40hz allowing these 4 badboys to handle the heavy 30's hz..
Power will be Lab Gruppen FP6400
I have 2 FP6400 currently


Any ideas or comments welcomed
The 2241 has an Fs of 35 Hz, an Xmax of 7.62 mm, Vas of 311 L.
The PDN 2450 has an Fs of 31.48, an Xmax of 10.62mm Vas of 369.15L, not a whole lot of difference.

Given the same tuning, (with a larger box) the approximate 3 dB Xmax advantage of the PDN 2450 (requiring twice the power) would only gain 3 dB overall, hardly noticeable.

If you tune them lower, say 32 Hz, their output level will drop at least 3 dB, so their LF output level in the 32 Hz range will be about 6 dB less than the 2241 SPL in the 40 Hz range, about half as loud.

Did you measure excursion to see if your present box Fb actually is actually 40 Hz?
Why not tune the 2241's to 35 Hz if you want more "heavy 30's"?
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Old 22nd September 2015, 06:34 PM   #5
GM is offline GM  United States
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Just happened to be looking at 24" today for lower tunings, so FWIW, scaled the PD2450 TH back to its published Fs and compared it to a vented alignment of the same total net Vb [Vb+Vv] = ~334.4 L using R.Small's recommended ~865 cm^2 minimum vent area for an unflared pipe, though didn't take the time to convert the rectangular duct to an equivalent [multiple] pipe vent, so the BR's net Vb might be more in reality if you go this route.

GM
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File Type: gif PD2450 ~32.37 Hz BR Vs TH [~334.4 L net].gif (19.5 KB, 271 views)
Attached Files
File Type: txt PD2450_32hz_TH.txt (962 Bytes, 19 views)
File Type: txt PD2450_32hz_BR.txt (939 Bytes, 11 views)
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Old 22nd September 2015, 08:14 PM   #6
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130 db at 30hz
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Old 22nd September 2015, 11:46 PM   #7
$$Maan is offline $$Maan  Denmark
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This is for the looks?
It sounds really silly for the job & your back!
More efficient boxes with more efficient drivers, after all 2241 are oldies, they sell much better than they perform imho:-)

With that many drivers at play horns could be worth considering
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Old 24th September 2015, 12:35 AM   #8
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Thanks for the reply guys
GM..got 4...2450 coming...I figure 16 ft3 each should do the job..and 1900w each from the 2 lab gruppen fp6400 should suffice..

The 2241 are not the best for lower 30s but good for 40s...
I looked at other 18s but at 30 hz they all average 80db and the 2450 around 91..92db and over 100db at cutoff of 80hz
Nice measurements
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Old 24th September 2015, 04:19 AM   #9
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The BC18PS100 does just fine in 253l 29hz port. Not trying to say its better but it does well for a slightly lower tuning but only 8mm Xmax. I will be getting a pair of these soon.

Just a thought is all.
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Old 24th September 2015, 09:39 AM   #10
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I looked at the bc drivers but I have JBL 2241 and some 2240 for typical 18 inch performance. .
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