How to use Martin J. King's software to design a TL loudspeaker?

Status
Not open for further replies.
Jump to Latest
#21
OK, now I see what you are meaning!

You think that the back opening on my drawing is a port (I mean a round port, like on a bass reflex)

But, in fact, it's still the TL itself, the opening of the TL. You can consider it as a second fold

Do you see how the thor is build? my project is the same, the opening isn't a round port, but a rectangular opening. The back plate is simply shorter that the speaker's height
The opening height is the same as 1/5 the speaker's deepht
 
#23
Epsilon is always a dimensionless ratio of driver position. In ML TQWT I input 0.5 because the driver is at half the length. In off-set driver I calculated epsilon by dividing the driver position by the length.

epsilon = driver position / L

epsilon = 6 inches / L = 6 inches x L^-1

There are advantages to both ways of expressing this ratio.

So in your "Thor" clone I would model the line up to midheight of the opening in the back then add a short section to get to the box inside edge and then on last section with an area equal to the opening and a length equal to the wall thickness. I think I did some thing similar for my first TL built with the Focal drivers. Take a look at the pictures in those articles.

Hope that helps,
 
#26
MJK said:
Take a look at Figure 35 in my Focal TL articles. You need to draw a picture like this except point 6 should be at the outer edge of the cabinet opening (outer most dashed line in the figure). This is the situation you want to model.

Hope that helps,
Click to expand...
that's the way I want to go
except that the line will be tapered (the inner bafle won't be at 90°)
 
#27
So all you have to do is change the values of the areas. If you are using the offset driver or ML TQWT worksheet this is only a couple of entries. If you are using the TL Sections worksheet then you can put in areas at discrete positions along the line. I think that the TL Sections worksheet is already set-up for the Focal TL geometry shown in the figure.
 
#29
The TL Sections worksheet is totally general without any "user interface" for easy input of a design geometry like the Offset Driver or ML TQWT worksheets. You have to go in and enter each section geometry by hand. It was my initial model until people started asking for simple input of certain geometries.

It is the basis for all of the other worksheets, the calculations are the same. The other worksheets fill in the individual geometries from the general simple input area on the first page. In the TL Sections worksheet you can model any geometry (folds, restrictions, sudden changes in cross-section or stuffing density, ...) that you can sketch out. It just takes time to enter all of the data for each section by hand.

That is the only difference, it is totally user input dependent.
 
#31
The software assumes a straight line for the TL. At low frequencies this is a good enough model. A fold will usually involve a changing cross-section as you go around the bend. So to model a fold I add short lengths that simulate turning the corner and change the areas at each end to simulate an expanding and then contracting geometry as you round the bend.

For example, look carefully at the geometry I have entered into the TL Sections worksheet and the geometry shown in Figure 35 mentioned above. I think that you will see how I modeled the fold in the Focal TL design. Based on finite element model results I have conluded that this method works very well.
 
#32
Some things I don't understand after having read rbrines's website:



http://geocities.com/rbrines1/Pages/Nature.html

some lines before the 5th graph:


"The most obvious means.... the lenght of the pipe... I chose 60"... not because it's the resonant frequency of the driver"
(Peerless 850122, resonates at 38Hz according to peerless)
60" means 56Hz resonance (1/4 wavelenght)


http://geocities.com/rbrines1/Pages/Non-Resonant_Pipes.html

"Augspurger goes on to suggest that extended bass output is possible at the expense of increased pipe volume. He supplies a second set of "extended" tables. Using the values from Table 2 (extended)..."

where's this table 2?
 
#36
sorry, not this Dave.

Uh...good luck.

My advice is that you shouldn't really sweat it. A million dollars says that your speaker system will be top-notch with or without the graph.

I wonder if Brines is referring to Augspurger's published work. Did you try e-mail to Brines?

Dave
 
#37
I'll try to mail him




I still can't manage to set a proper TL for the driver I chose (Audax HM170G8)

it's Qts=0.35 and Vas=29.19L
so, according to augspurger's optimized alignments, I should go with Vas/Vline=3.10

but 9.4L is soo small, I can't do anything with this




I thought I found a good driver, but it has either a too small Qts or a too small Vas

:bawling:
 
Status
Not open for further replies.
Top Bottom