Need help for TL design

[heinz1964]

Hi

Any experts who can help me design a TL?

I intend to use 4 Focal 7K415 bass/midrange drivers I have laying around. I will use an Tangband 4W 1320 bamboo fullrange for the midrange/tweeter. I am not sure about the crossover frequency between these two drivers yet.

I was thinking of placing a Focal on the front and one on the back of the loudspeaker. Each having its own TL enclosure, but only the front will play into the midrange.

I know the Focals are not a classical driver for a TL but I would still like to try. If it does not work it will only cost me the materials for the cabinet.

Dimension for the cabinet. I would like to keep it under 12" ( 30 cm ) wide and under 20" ( 50 cm ) deep. hight is not an issue.

Specs of 7K415:

Fs 32,5 hz
Vas 56 liter
Qts .26
Qes .29
Qms .2,52
Rcc 7,8 ohm
Sd 163 cm2
Mms 16 gramRms 1,3 kg/s

Any ideas?

best regards

Uwe

[planet10]

Download Martin King's alignment tables (and spreadsheet) and start there.

Transmission Line Theory

dave

[Psychobiker]

The man above me has said all that needs to be said.

[bjorno]

Originally Posted by heinz1964

..I was thinking of placing a Focal on the front and one on the back of the loudspeaker. Each having its own TL enclosure, but only the front will play into the midrange..hight is not an issue..Any ideas?..

Hi, here is one idea:

b

[heinz1964]

Hi Bjorno

Thank u for the reply.

I am not used to read the results from Hornrespons.

But as i see it you suggest that:

Front enclosure is a basreflex cabinet where inside length is so long that it acts as a TL and this is transferred to the room via a normal basreflex port.

Back enclosure is more like a standard TL.

But the way you positioned the drivers they will not eliminate there mechanical forces on the cabinet. Can I turn the rear enclosure upside down so that the driver is on top?

How deep is the combined enclosure?

Have you heard of the fuzzy technologie that they use for TL and also for horns in the magazine Hobby HiFi from Germany?

Best regards

Uwe

[Henry8]

I built a TL, based on Dr Bailey's revised design.
The beauty of the TL is that the rear sound is ultilised.
However there are to many variables to deal with ie line length and cavity/or not (which you cant change after building) stuffing material and the amount ( keeping it in place and the ease/problem of altering it in built box) port size etc...
During 8 years of messing i did briefly get a good sound, but do you want to be messing so long, i looked into m.kings info but basically it does not really model a TL to the point where your say 85% done before you cut wood.
I have since moved to closed box designs, these are highly predicatable to model and with the addition of a LTX cct, can offer true bass to whatever frequency you choose.

[pkitt]

If you couldn't use Martin's worksheets to end up with a TL design that needed little or no fiddling with after it was built, then clearly either you didn't learn/understand well enough how to use them, or you have some rather unusual requirements or hearing. I've modeled dozens and dozens of TLs for personal and for others' use, and built 7 designs for personal use, all modeled with Martin's worksheets. Assuming a driver will work well in a TL, I can arrive at an acceptable TL model in literally minutes, and can optimize it in a few hours at most (and it's way more than 85% done). I've never had to tweak anything about a TL after it was built (crossovers excluded). You won't find anything more accurate than Martin's work IMO.
Paul

Originally Posted by Henry8

I built a TL, based on Dr Bailey's revised design.
The beauty of the TL is that the rear sound is ultilised.
However there are to many variables to deal with ie line length and cavity/or not (which you cant change after building) stuffing material and the amount ( keeping it in place and the ease/problem of altering it in built box) port size etc...
During 8 years of messing i did briefly get a good sound, but do you want to be messing so long, i looked into m.kings info but basically it does not really model a TL to the point where your say 85% done before you cut wood.
I have since moved to closed box designs, these are highly predicatable to model and with the addition of a LTX cct, can offer true bass to whatever frequency you choose.

[heinz1964]

hi

I would like to make a closed box but with only 2 7" woofers pr side it will not play loud or deep enough.

If I have to go for a closed box no less than two 10" will do.

Uwe

[picowallspeaker]

I got inspiration from Pkitt's advice on how to use a Seas Aluminium 10" in a tapered TL ,advice given to someone else , and I built something like that...and it works . But Heinz64 worries about mechanical-vibration in the enclosure and he's right ,those forces couple and transfer rapidly to midrange's basket ,so it might be an issue . Instead of putting a new ext suspension to my 10" ,I've also considered the use of two 7-8" one aside the other (up & down ) but it's hardly predictable of how they would interfere each other ,sharing the same acoustic load . BTW All speakers and cabinets put in their equation the backwave
Cool !! The Yin and the Yang.
Again ?

[Henry8]

Originally Posted by pkitt

If you couldn't use Martin's worksheets to end up with a TL design that needed little or no fiddling with after it was built, then clearly either you didn't learn/understand well enough how to use them, or you have some rather unusual requirements or hearing. I've modeled dozens and dozens of TLs for personal and for others' use, and built 7 designs for personal use, all modeled with Martin's worksheets. Assuming a driver will work well in a TL, I can arrive at an acceptable TL model in literally minutes, and can optimize it in a few hours at most (and it's way more than 85% done). I've never had to tweak anything about a TL after it was built (crossovers excluded). You won't find anything more accurate than Martin's work IMO.
Paul

1. I actually conversed with king on the use/application of his worksheet
2. Just because youve built anything does not make you an authority (most people who knock anything up are so pleased it works at all)
3. Quote "assuming the driver will work"???
4. OK so youve optimised it, so it looks good on the screen, did you verify it with acoustic tests or just apply point #2 ???
5 Yes you wont find anything more accurate, but is it accurate at all???


At least you didnt argue with my point on sealed boxes.......