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Old 11th October 2006, 09:32 PM   #1
type is offline type  United States
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Default Just got a pair of FR125s

I just got a pair of CSS FR125s drivers. I want to put them in a sealed cabinet. I was planning on using the recommended design but if I'm going with a sealed speaker shouldn't the internal volume be smaller?
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Old 11th October 2006, 09:38 PM   #2
2litre is offline 2litre  United States
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type,

Have you checked out the Planet_10 website?

There is a nice chart that gives 5 differnt sized boxes, the expected Q of the the system and the expected frequency responses for each.

http://www.planet10-hifi.com/

Look in the Box Plan Library.

R/

Jim
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Old 11th October 2006, 09:51 PM   #3
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I have them now in a ~5 liter sealed and still feel they're a bit boomy and undetailed. Probably no longer a problem with box, but the driver.
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Old 12th October 2006, 05:46 PM   #4
inrank is offline inrank  United Kingdom
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i found them to be just right in a 11L sealed box.

no boom at all.

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Old 12th October 2006, 08:12 PM   #5
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Quote:
Originally posted by Landroval
I have them now in a ~5 liter sealed and still feel they're a bit boomy and undetailed. Probably no longer a problem with box, but the driver.

The boom's the box, 5 liter is too small, so you get boomy bass. The lack of detail could be the driver, it slightly rolls off above 10kHz - I find it smooth others undetailed.

best, LC
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Old 13th October 2006, 10:36 PM   #6
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Yes, I agree a bit. The 8 liter vented (or aperiodic) is a bit better, but I don't like the sound of the driver that much. It leaves so much stuff out (not only from the top octave).
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Old 14th October 2006, 08:20 AM   #7
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Theres a hole in the response between 8k and 11k which I filled in by using a graphic equaliser type circuit, which I could post if anyones interested. The treble seems to improve with running in.
I wonder if the boom is caused by air leaking past the phase plug. Since there is no dust cap there is no air seal. Perhaps OB is the best for this driver.
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Old 14th October 2006, 10:04 AM   #8
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Quote:
Originally posted by consort_ee_um
Theres a hole in the response between 8k and 11k ....
Your drivers broken in? Mine don't show that on a sweep
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Old 15th October 2006, 02:54 PM   #9
Vikash is offline Vikash  United Kingdom
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Quote:
Originally posted by consort_ee_um
Theres a hole in the response between 8k and 11k which I filled in by using a graphic equaliser type circuit, which I could post if anyones interested. The treble seems to improve with running in.
I wonder if the boom is caused by air leaking past the phase plug. Since there is no dust cap there is no air seal. Perhaps OB is the best for this driver.
Yes, I'm interested in the circuit. I can confirm the dip at 9.6Hz, the problem compounded by the peak at 6.5Khz which effectively shows a 9db drop over that 3kHz bandwidth.

I'm trying to decide on some parallel notch filter values for the 9.6kHz peak and also to flatten out the 700-2k region. The two notches should bring it down to +/- 3db from 60Hz-20kHz or better.
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Old 16th October 2006, 10:03 AM   #10
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Here is the circuit. Its basically a graphic equaliser circut with a Higher Q than normal. IC1B, R4, R5 and C1 are a simulated inductor or gyrator circuit, and R1,R2 would be the pot in a graohic equaliser. C2 is a 470pF in parallel with a 39pF
I tried other bandpass circuits but they did horrendous things with the phase. With this you can change the centre frequency easily with C2 and the gain peak with R2.
I had to move the frequency up from the centre of the trough so that the filter skirt did not amplify the 7kHz peak, but I ended up with a surprisingly flat response and the phase was linear as well.
You can have more filters by connecting another R1-2,R4-5,C1-2 and IC1B across points A and B and if you make R1 small and R2 big you will get a notch.
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