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 ?
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 ?
Why leave out the Zobel? The Zobel is what makes the BSC circuit resposne predictable and adjustable at high frequency.
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.
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.
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
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
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.
Black=On Axis, Red=30deg off, Blue=60deg off, Gray=unsmoothed on axis
Bob
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.
An externally hosted image should be here but it was not working when we last tested it.
Black=On Axis, Red=30deg off, Blue=60deg off, Gray=unsmoothed on axis
Bob
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.
Cement board here in the US is a ceramic based material 1/4" thick that is used in (typically) home construction to put tile on, such as bathrooms, kitchens, etc.. I've used it in building TLs and highly recommend it to reduce cabinet vibrations. Other materials can be substituted if it is the same thickness, or you account for the thickness in your internal volume. Granite tile, ceramic tile or other types of floor tile can be used. A good construction adhesive can be used to attach it to the inside of the cabinet panels.
weidok said:
Timn8ter has it right. The brand I use is "Hardi-Backer", though this information is probably of little use outside North Amaerica. I used to recommend ceramic tiles, but the Hardi-Backer is much easier to cut to size.
Yes, double the top and line it with cement board, tile, whatever. You will be amazed at the difference this makes in the amout of vibration -- and sound -- coming from a thin top panel.
Bob
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