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Old 2nd October 2004, 07:29 PM   #1
weidok is offline weidok  Netherlands
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Default Building ML TL with Fostex FE 167 E

Hello

I planning to build a ML TL with the fullrange 6"speaker from Fostex FE 167 E.
The dimensions will be height= 39" depht= 11'and wide = 7 1/2" and a port which will be round 3" and 2 1/2" long 1 1/4" from the bottum,

BSC will be L= 0,3 mH, C= 3,9 uF and R=4,7 ohm.

do i need any other correction network?

who has any ideas and who can help me ?
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Old 2nd October 2004, 11:35 PM   #2
MJK is offline MJK  United States
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You will probably need a Zobel to make the BSC circuit work correctly. Where did you get the values for the circuit? The values don't look correct to me, maybe I am wrong.

Hope that helps,
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Old 3rd October 2004, 03:07 PM   #3
weidok is offline weidok  Netherlands
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Martin

I used a crossoverdesign exel spreadsheet 2.03 from internet tried to design a bsc network without a zobel..

What do you suggest for a better bsc and zobel..

are the demensions correct??

ytzen
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Old 3rd October 2004, 06:34 PM   #4
MJK is offline MJK  United States
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Quote:
I used a crossoverdesign exel spreadsheet 2.03 from internet tried to design a bsc network without a zobel..
Why leave out the Zobel? The Zobel is what makes the BSC circuit resposne predictable and adjustable at high frequency.

Quote:
What do you suggest for a better bsc and zobel..
The Zobel and BSC circuit I used for my ML TQWT should be closer to the correct values for your geometry. The FE-164 and FE-167E are similar so I would start with values as follows.

Zobel :
6.8 uF in series with 10 ohms.

BSC :
2, 3, 4, or 5 mH inductor (probably a 3 mH would be best) in parallel with a 4 to 8 ohm resistor.

The BSC circuit would be adjusted base on your amp and room placement. Without measurements all you can do is try different values until you get the combination that works best. I think your 0.3 mH inductor is diffinitely too small and I don't think the FE-167E will need the 3.9 uF cap to help the high end. The high end should be adequate. Again, trying the values is the final test.

Quote:
are the demensions correct??
I don't know, how did you arrive at these dimensions? Do you have some simulation results? Without some analysis I don't know if this is a good geometry or not.
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Old 3rd October 2004, 07:48 PM   #5
weidok is offline weidok  Netherlands
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Martin

The geometry is from a ml tl with the Fostex FE 168 sigma ?
I see now the height must be 40 "
and the port is to short i think !!!

Just saw Rob Brines has even better plans with the same speaker that i want to use.. and yes he also uses a zobelnetwork

Sorry but i have no simulation results at all
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Old 4th October 2004, 12:12 AM   #6
MJK is offline MJK  United States
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I am sure Bob Brines' design is very good. I think it would be a safe bet to follow his plans to the letter. I have read many good reviews and comments about his FE-167E ML TL design. You cannot go wrong with his design.
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Old 4th October 2004, 02:43 AM   #7
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Interestingly enough, my latest set of MLTL's for the FE167E does not use a zobel. Martin has been using a cap across the BSC filter, which changes the step filter into a low Q notch filter. The reason for doing this is to bring back some of the high frequency response that goes away with the step filter.

I found, at least with my cabinet, that by removing the zobel, the rising impedance of the driver does indeed cause the BSC filter to fail at high frequency and bring up the top end. This may be a little hot for some, but since I listen somewhat off-axis anyway, it is about right. 2mH||6ohm.

I'm not suggesting this is a silver bullet, but it does seem to work in this case.

Click the image to open in full size.

Black=On Axis, Red=30deg off, Blue=60deg off, Gray=unsmoothed on axis

Bob
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Old 4th October 2004, 11:16 AM   #8
MJK is offline MJK  United States
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I have also tried removing the Zobel and notice the same increased high frequency response that is shown in your plots. This can be very effective. The only downside is the loss of adjustability and the changing response as you adjust the parallel resistor in the BSC circuit. If it works then that is the simple and low cost (less parts) solution. But leaving the Zobel in, and using a cap in the BSC circuit, allows for a greater amount of adjustability in the high frequenct response. Either method can work well and they are easy circuit configurations to try.
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Old 4th October 2004, 06:39 PM   #9
weidok is offline weidok  Netherlands
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Martin and Bob,

Thanks i will try both options with and whitout a zobel..
Where can i find more reviews with the Fostex Fe 167 E
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Old 5th October 2004, 04:15 AM   #10
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Quote:
Originally posted by MJK
FE-167E ML TL design
I've heard a couple variations of Bob's ML-TL and these are good... a no brainer to just build his design.

dave
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