TL-box for BG20 Visaton

[xrk971]

Originally Posted by Gost22

Hi xrk971!
This picture is very small please give the increase.
thank you!
Cheers!

The image can be found in this thread: Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks?

Link to picture here: http://www.diyaudio.com/forums/attac...s-bib-vifa.jpg

It is only an example with a different driver. You need to run the BIB calculator for the BG20 to get the dimensions and location of driver (from top), and length of diagonal divider.

[Gost22]

Hi
How do I find the dimensions of this TL-box in the sketch?
thank you!

[Scottmoose]

By learning about quarter-wave speaker design, and then designing it. That's a conical horn (sometimes rather inaccurately called a TQWT) by the way rather than a transmission line.

OK, these are the basics of what you need to do:

-The total axial length of the horn should be set according to the desired tuning frequency and the degree of taper you wish to employ.

-The degree of taper you wish to employ should (theoretically) be established by the bandwidth you wish the enclosure to operate over. The greater the degree of taper, the wider the resonant bandwidth, but all other things being equal, the longer the horn will need to be for a given tuning frequency.

-The driver location along the horn must then be be set according to the length and taper of the horn to minimise unwanted harmonic resonances.

-The total volume of the enclosure needs to be established according to the volume compliance of the drive unit, its Q, and the desired tuning frequency.

-The cross sectional area of the vent depends on the desired tuning, whether you wish to mass-load the horn, or whether you simply want to use it to help filter off some unwanted pipe harmonic resonances. Assuming you wish to keep it simple, just set it to = the Sd of the driver.

-You will then need to damp the enclosure appropriately. The quantities and location of the damping material will vary depending on the alignment you have used.

[Scottmoose]

OK, I had a couple of minutes so here are some (more) dimensions for you, for a Weems style folded conical horn like the one you drew above.

Please don't ask me to draw a diagram. I don't have the time (or talent). If you don't know what some of the words mean, a very little searching / research will give you the answers, and you might get a better understanding.

This is based on a T/S max-flat volume alignment assuming the parameters on the Visaton website. All dimensions are internal. I assumed 3/4in building material.

-Cabinet height = 40.25in
-Width = 12in
-Total internal cabinet depth = 19.5in
-Throat depth = 4in
-Taper ratio = 1:4
-Height of vent = 2.75in
-Zd (distance of the centre of the drive unit from the throat) 31.125in
-Top of internal baffle centred equidistant from the internal top, back and front
-Line the front and top of the box around the fold with damping material. This should be continued for 10in down the back of the enclosure. Adjust to requirements from there. A removable back to the cabinet would be useful to allow easy stuffing adjustment.

[Gost22]

Hi scottmoose!
You speak for horn with BG20-Visaton, I want I design the TL-box or the WIBAQ: TABAQ design with this speaker BG20!
Here's horns see to draft BG20 !
Best Regards!

[Scottmoose]

-The drawing you show in post 12 is technically a type of horn, since it expands toward the terminus. It is sometimes known as a Weems Pipe, or, rather inaccurately, a TQWT or TQWP. I have given you dimensions for the type of enclosure that you asked for. Are you now saying you don't want that after all?

[Gost22]

WIBAQ design see figure down

[Gost22]

Originally Posted by Scottmoose

-The drawing you show in post 12 is technically a type of horn, since it expands toward the terminus. It is sometimes known as a Weems Pipe, or, rather inaccurately, a TQWT or TQWP. I have given you dimensions for the type of enclosure that you asked for. Are you now saying you don't want that after all?

Mr. Scottmoose, all right now, I realized that you're talking about the sketch up!
thank you!

[Scottmoose]

Yes, that's what I was talking about.

The TABAQ is just an MLTL for a particular set of small drive units. WIBAQ is just a similar type of MLTL for a different drive unit. GM, in post 5, gave you the dimensions for just such an enclosure.

To translate GM's nomenclature for you: it is a simple rectangular box. Like the TABAQ.

L = length. The internal height of the enclosure.
CSA = Cross Sectional Area of the cabinet in square inches. Multiply the internal width of the cabinet by the internal depth of the cabinet. It needs to add to the figure he provided, or very close.
Zdriver = the distance the centre of the drive unit should be from the internal top of the box.
Zport = the distance the centre of the vent / port should be from the internal bottom. He told you it should be as close to the bottom as possible.
Dport = the diameter of the circular port used in inches.
Lport = the length of the port in inches.

[xrk971]

Originally Posted by Scottmoose

OK, I had a couple of minutes so here are some (more) dimensions for you, for a Weems style folded conical horn like the one you drew above.

Please don't ask me to draw a diagram. I don't have the time (or talent). If you don't know what some of the words mean, a very little searching / research will give you the answers, and you might get a better understanding.

This is based on a T/S max-flat volume alignment assuming the parameters on the Visaton website. All dimensions are internal. I assumed 3/4in building material.

-Cabinet height = 40.25in
-Width = 12in
-Total internal cabinet depth = 19.5in
-Throat depth = 4in
-Taper ratio = 1:4
-Height of vent = 2.75in
-Zd (distance of the centre of the drive unit from the throat) 31.125in
-Top of internal baffle centred equidistant from the internal top, back and front
-Line the front and top of the box around the fold with damping material. This should be continued for 10in down the back of the enclosure. Adjust to requirements from there. A removable back to the cabinet would be useful to allow easy stuffing adjustment.

That was awfully nice of you to run a sim of the hand sketched box for the OP. The design looks really good. I don't know if Gost22 realizes how much we are going out of our way to provide suggestions and actual dimensions because it looks like he may just go with another design or driver.