help designing an martin king TL

[matjans]

hello,

thanks everybody who helped me choose a driver for my diy speakers (fostex fe206e it will be). Still new here I need som more help (sorry ), this time designing a cabinet.

After reading a lot of posts on the martin king TL speaker, the Jericho horn and other stuff I decided to go with the King TL. I want to build a straight one, no slanted walls.
On Bob's speaker stuff site I found a lot of useful info. however, win2k doesn't seem to get along with mathcad8 so i can't use martin kings worksheets.

can anybody help me designing a King TL cabinet?

(btw: for those interested: finished my all black gate & riken ohm gainclone today. Sounds pretty good!)

Matti

[GM]

I did some sims awhile back. Since this driver requires substantial series resistance and has a low Xmax, don't expect it to be all that efficient or have much linear LF output.

This one will require baffle step correction or placement against a wall:

3ohms series R:
rp = 1.25"
Lp = 4"
Density = 0.25lbs/ft^3

L (in)
24.157

cross sectional area (in^2)
60.087

suggested (width)
9.860

suggested (depth)
6.094


driver down from top (in)
10.068

Fb (Hz)
~34

---------

This one you should be able to get by without less BSC and/or move it away from the wall somewhat:

6ohms series R
rp = 1.25"
Lp = 3"
Density = 0.25lbs/ft^3

L (in)
30.889

cross sectional area (in^2)
87.381

suggested (width)
11.891

suggested (depth)
7.349

driver down from top (in)
12.687

Fb (Hz)
~34

Since the driver will be well below ear height when seated, extending the pipe down the appropriate amount to get the driver up leaves a nice sized cavity to mass load the cab with kitty litter/sand/whatever. I also recommend a heavy top to further mass load it, as well as a driver brace, such as this tunable one: http://melhuish.org/audio/images/press-screw.gif

Please let us know now it sounds/actual amount of stuffing/tweaks required if you choose to build either one.

HTH,

GM

[matjans]

hmm ok, do you feel the fostex should use another type of cabinet? a horn maybe?

edit:

forgot to mention that if this works but lacks bass i might add a subwoofer later.

/edit.

[GM]

If max SPL capability/lowest distortion is desired. There's nothing wrong with either of these designs, it just depends on how loud you want them to play down low and how large/complex a cab you can tolerate.

Either of these are tuned low enough to blend well to a sub around 80Hz if desired.

GM

[matjans]

ok thanks i think i'll go with something based on your first option (i'm a student with not *that* much space in my room so...)

[MJK]

On my website there is an unlinked design for the Fostex FE-206E and FE-207E drivers.

http://www.quarter-wave.com/FE_206E_ML_TL.pdf

http://www.quarter-wave.com/FE_207E_ML_TL.pdf

which is essentially my Lowther ML TL with a six inch long vent. This design has been built with both the FE-207E and the FE-206E.

For the FE-206E, the correction circuit was modified to become a 3 mH inductor in parallel with a 10 ohm resistor instead of the values shown for my Lowther project (4mH inductor and parallel resistor). The Zobel was unchanged. This design is being driven by a tube amp and the DIYer has reported he is very very happy.

Hope that helps,

[at]

I built the MLTL on my holidays to Martin's specificiations. On a first listen, the Fe 206e sounded painfully bright and thin with a lack of bass response. After about 2 hours, the brightness slightly decreased and the bass marginally improved.

However, after building the correction network that Martin describes a DRAMATIC change to the sound occured. The brightness greatly reduced, and the bass was more noticeable. Whilst not earth shaking, the bass is tight and punchy. I am running an EL34 amp in triode mode, so I dont expect there to be strong bass anyway.

Overall, the sound is even, and seems to have a flat response through most of the frequency range. I still find the driver a little bright, but I am comparing this with my last speakers which contained Dynaudio drivers that are very smooth. Listening to both CD and vinyl is very satisfying with the new speakers, and I have got my motivation back to explore my collection after a few years with an inefficient and overly smooth Dyn speaker.

The project was easy to build, lots of fund, and quite cheap (AUD $700). I might play with the correction network a little to finalise the speakers to my tastes.

Thank you Martin for the easy to follow plans and indepth description on your website. You have another convert to MLTL !!

[kelticwizard]

Originally posted by matjans

On Bob's speaker stuff site I found a lot of useful info. however, win2k doesn't seem to get along with mathcad8 so i can't use martin kings worksheets.

can anybody help me designing a King TL cabinet?
Matti

A couple of issues about Martin's worksheets.

Let MathCAD8 install itself the folder it wants. DO NOT create a folder for it and install it in there. It installs itself into Program File/Mathsoft or whatever-let it do so.

Yes, I know it has a Browse feature for installing, but I speak from experience, it will mess things up if you use the Browse.

A) Use the English version of Excel. You can switch whatever version you use of Excel to the English version-there is a method people can explain. Very easy.

B) A period must be used to demote decimals. The comma for the decimals will render MathCAD 8 inoperable with Martin's worksheets. This can also be changed by the user.

C) Do you have Norton Anti-Virus? It will mess things up unless you disable the scripting feature individually. Merely disabling Norton Anti-Virus will not-repeat will not-solve this problem. The scripting function must be turned off individually-then it will work.

Once you turn off the scripting function individually, things will work very well.

An illustration of how to turn off the Norton scripting funtion is here:
Transmission line, Help needed

Repeat-merely disabling Norton will not get the job done. If you have Norton and you want to use MathCAD with Martin's worksheets, the scripting function must be turned off individually. It takes about 30 seconds.

Here are some more threads on how to get Martin's worksheets going:

Difficulty Installing MathCAD with Win98SE Read from post #21 onward,

MathCad


Good luck!