Small transmission lines wanted

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Ropie

Ropie

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Joined 2003
I'm looking for transmission line designs with small dimensions. I remember seeing a page somewhere on the net with a number of commercial designs, from the 70s I think, but I just can't find it anymore. I'm fairly sure they weren't IMFs, though they may have been a related company. Anyone have any ideas??

Failing that, any small diy TL designs would be of interest. Nearly all that i have seen have been at least 900mm high. I'm looking for something ideally no higher than about 750mm, depth is not really an issue but width would ideally be minimal. Or would it be possible to take an existing taller design and just add another fold?

Thanks :)

BTW, Dave, the Leak Sandwiches I went to see following your advice were no good unfortunately - one damaged cone and they were ceramics anyway.
 
purplepeople

purplepeople

Member
Joined 2003
I've got one for the W3-593s. It is OD 9" x 9" x 5" using cheap 3/4" board. The line is about 24" long.

I'm still working on the BSC circuit so it is not finished but hooked up to the old Philips AG9016 that my Dad gave me, it sounds great. Not deep bass, but lots of it. When it's done, it will get posted.

:)ensen.
 

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purplepeople

purplepeople

Member
Joined 2003
Kind words, Dave. Thank you. I disable smilies in my post. My guess is that replies must also check the 3rd box.

Yes, the 3D model was done in Rhino. The image is merely a screenshot function. I left out the dimensions from clarity.

Ropie: This is as cheap as it gets. The drivers were on clearance from www.acoustic-technologies.ca. The baffle step circuit may turn out to be the most expensive part of the project. I'm still working on the calculation and plan to mount it outboard so as not to mess up the internals.

As it stands, the two upper sections are stuffed with polyester fill from a dollar store blanket. The line tapers from 3" x 3.5" (75mm x 85mm) to 1" x 3.5" (25mm x 85mm) over the 24" (600mm) internal length, which will match the 100Hz Fs of many TB drivers, including the popular W3-871s. I used Martin J King's venerable TL cookbook for the driver offset. Even though the driver does not contact the upper fold for vibration control, the baffle and box are so small that even the cheap pine I'm using turns out quite rigid. It's currently assembled with about 40 drywall screws each, and may never get adhesive.

The outer dimensions are 9"H x 5"W x 9"D (225mm x 125mm x 225mm). I played with the configuration, length and driver offsets until I had something that is almost perfectly symmetrical on the front view.

:)ensen.
 
Ropie

Ropie

Member
Joined 2003
:) ensen,

It's a really good looking speaker, and thinking about it, would look great on a sand-filled plinth of approximately the same dimensions, maybe a bit taller. The only trouble for me is that Tangbands are very hard to find in the UK and I'd have to dice with high shipping prices and import duty, etc.
 
purplepeople

purplepeople

Member
Joined 2003
The line as designed will not work for any of the 3" Fostex drivers as they seem to be either Fs=140. The line is tuned for Fs=100, which is a very common spec for the TB drivers. I haven't tried it with other drivers but TLs are supposed to be very forgiving of different specs as long as the Fs is about right. For example, I've tried an older discontinued TB-FM69 driver I had lying around and it wasn't too much different on first impression.

If you need to shorten the line for the higher Fs of the Fostex drivers, you can mess with the thickness at the wide end or the u-turns.... and then move the driver offset to compensate.

:)ensen.
 
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