my new way to build a TML

[Roemhild]

Hi @ll


I have got a new idea how to calculate and build a TML. I would like to share my ideas with you.


First thought: TML = vented system

A TML is a vented construction like a Horn, TQWT, BR etc. The big difference is that the line is getting tighter.



Second thought: tuning frequency (f TML)

You find in literature that you should set the tuning frequency on the free air frequency (f s) of the driver. According to other projects from me I thing that you shouldn’t use one frequency for two different parameters.
And I have the feeling that the tuning frequency should be a bit higher than the free air frequency of the driver.



Third thought: starting section (A H) and ending section (A M)

The starting section (AH) has got to be in a certain percentage to the ending section (AM). In the past I have played a lot with 1,6181 (we call it golden cut).




Fourth thought: volume of the line (VTML)

I cases that the line gets smaller the air load on the driver will be higher. Therefore I thing that the volume has to be higher that the volume of a Bassreflex (Vbr). A have made similar notice with my way of building a backload horn.
In order of the starting -, ending area and the length we have a volume. This volume should be emotional 1.5 – 1.6 times higher than the Bassreflex. I have had 1.2 – 1.3 times higher volumes at BL-horns and here we load the horn after the chamber.



Fifth thought: the right driver

A driver for a BR should be the right driver for a TML. Qts around 0.25 – 0.4 should work fine





Starting the calculation:


First we need the optimal BR volume (VBR) and calculate it with the factor.
(-> formula 1)

Simplified we can calculate the tuning frequency (fVTML) of the driver in that volume.
(-> formula 2)



The tuning frequency of the TML length (fTML) should be between the free air frequency (fs) and the tuning frequency (fVTML) of the driver in the volume.
(-> formula 3)
We get the length with:
(-> formula 4)


When we have found out the optimal volume we can calculate the starting and ending sections. All we have to do is to convert the formula for the volume. The requirement is that the sections stand in a certain percentage.
(-> formula 5)
(-> formula 6)
(-> formula 7)

Opening section is than:
(-> formula 8)


Than I have placed the driver at 1/3 of the TML-length and simulated a drive I am playing with right now.

[Roemhild]

first simulation

[Roemhild]

pic.: #1

[Roemhild]

pic.: #2

[Roemhild]

pic.: #3

[Bose(o)]

One small detail and I'll look over the rest for some time before I answer to your thoughts in detail. My problem is, how does the sound get to the "tube"? Or, have you just not cut the necessary wood for the transmission to the tube.

[Roemhild]

Hi Bose(o)


I have planed to place the driver at 1/3 of the lenght as you can see on the picture below.

The lower camber is to adsorption a frequency at 200Hz.

The upper camber is for a fullrange driver (the Coral 8A-70).


I haven't finished the frontplate yet.



regards Till

[RJ]

Do you have these calculations in a spreadsheet program?
I would love to try this design.

[Roemhild]

Hi @ll


I dont know how I can post an excel-sheet but if you give me your email I can mail it to you.


best regards Till

[RJ]

OK, I E-Mailed you my address.
Thanks!