VTL - a few questions

[setting son]

Hi all,

A couple of newb questions re the Jordan VTL cabinet:



Why is the line not 'squared off' below the angled chamber as shown here?:




And also, how is the distance of the driver from the top of the cabinet calculated

Thanks,

Lee

[bobhayes]

At the low frequencies the transmission line is designed to operate, the extra panel you suggest would make negligible difference to it's performance.

I think the driver has been positioned equidistant from sides and top of the enclosere for asthetic reasons, although there may be an acoustic reason for this too. (implementing baffle step compensation perhaps)

There is a good bit of information on E.J.Jordan's website. and if you require further information, you can contect him too.



http://www.ejjordan.co.uk.html

[Colin]

Keeping the internal baffle at an angle reduces the number of parallel surfaces inside the top chamber, so it should sound better than a flat baffle (fewer strong resonances).

If determined to make it square, calculate the volume of the chamber as it is part of the design. It establishes the region where the line decouples from the chamber (above a certain frequency, the line ceases to laod the drive unit and the driver behaves as though it is loaded by the chamber alone - reducing dips and peaks in mid-range response).

Given that the VTL is a balanced design refined over several prototypes, I'd stick with it as published. The only change you could make is to the position of the driver so that it is not equidistant from top and sides - this is for almost certainly for visual reasons rather than acoustic.

(This is the cue for someone to give a more technical answer than that second paragraph.)

[setting son]

Thanks for the info guys, much appreciated.

[Dumbass]

Have you considered the MLTL-31 and MLTL-48 designs?

The VTL was designed before reliable simulation software was available for transmission line enclosures. The MLTL designs go lower and flatter.

The nice thing about the VTL, in my opinion, is the wide baffle, but you could very easily add a false baffle to the MLTL designs. Another nifty thing with the VTL is the stand and the downward venting, but again you could alter the MLTL designs to do exactly that. If you went that route, I would try scale drawings and or models to verify the visual aesthetic.

[Colin]

You could modify the MLTL designs to have a similar wide baffle to the VTL, as long as you keep the cross sectional area the same as the original MLTL designs. (They're actually similar to the VTL.) With a 12 inch wide enclosure, you'd be free to have the vent firing to the side, with plenty of space around the port inside the cabinet.

The only problem with a wide MLTL is that visually it would be imposing - you need to have them tall to get the driver high enough.

[matt kite]

One more question regarding dimensions of the VTL... Can anyone confirm if the 18cm dimension for the position of the angled baffle is measured internally or externally? The published drawing suggests external, but that means the line expands from 8.8cm to 11cm at the bottom bend before reducing to 7cm. Positioning the angled baffle at 18cm internally would seem to make more sense but the drawing is open to interpretation. Any help appreciated before I start cutting and glueing.

Matt

[matt kite]

One more question regarding dimensions of the VTL... Can anyone confirm if the 18cm dimension for the position of the angled baffle is measured internally or externally? The published drawing suggests external, but that means the line expands from 8.8cm to 11cm at the bottom bend before reducing to 7cm. Positioning the angled baffle at 18cm internally would seem to make more sense but the drawing is open to interpretation. Any help appreciated before I start cutting and glueing.

Matt

[Colin]

I think it's meant to be internal.

Good luck with the build.

[matt kite]

Thanks Colin. The more I look at it, the more it seems to make sense to measure the 18cm internally. That's what I'll go with.