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Old 15th April 2005, 11:34 PM   #1
Ropie is offline Ropie  United Kingdom
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Default Small transmission lines wanted

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.
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Old 16th April 2005, 12:20 AM   #2
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GM's MLTL for the Fostex FE127E is (interior dimensions):

H= 568mm
W= 189mm
D= 116mm

Driver center 225mm from top

Vent 38mm dia X 28.6mm

I haven't built mine yet, but it's supposed to make a nice little speaker.
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Old 16th April 2005, 12:43 AM   #3
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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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Old 16th April 2005, 07:09 AM   #4
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Quote:
Originally posted by purplepeople
I've got one for the W3-593s.
Nice illustration ensen

dave
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Old 16th April 2005, 07:54 AM   #5
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Ditto! Is that in Rhino?
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Old 16th April 2005, 08:32 AM   #6
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ensen
What's the secret to keep it from going all smiley?

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Old 16th April 2005, 10:51 AM   #7
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This is a multi-folded TQWT for the small Tangband w3-817s:
Speaker projects with Tangband W3-817S: Needle and Brick
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Old 16th April 2005, 05:07 PM   #8
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Here's how PMC does it.
http://www.pmcloudspeaker.com/transmission.html
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Old 16th April 2005, 09:17 PM   #9
Ropie is offline Ropie  United Kingdom
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Thanks for all the excellent links and pics.

Quote:
Originally posted by johninCR
GM's MLTL for the Fostex FE127E is (interior dimensions):

H= 568mm
W= 189mm
D= 116mm
JohninCR, these sound perfect and would be a good price. Is there any more info available on them?
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Old 17th April 2005, 08:57 AM   #10
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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.
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