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PostPosted: 09 Jan 2009, 09:27 
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Joined: 09 Jan 2009, 07:52
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I'm setting myself up a home theatre, and I've long been lurking here, planning a diy 5.1 setup.

My plans change constantly, but recently I've come to the conclusion that there will be only one way I can get a center channel going. And that is, to sneak it in between the HTPC on the left and my receiver on the right, centered below the screen.
The screen is just a pice of chimney I'm projecting onto, and the gear is standing on a cabinet inside the old fireplace.
There's no space for an MTM, I can't use (or build) a soundbar, in fact my option are very limited as I'm renting and my SO requires invisible gear. Yes, I did consider those bige transparant horns, but I decided I value my life too much.
I've got about 20cm space, and both htpc and receiver are about 17cm high. So my idea was to build a small speaker, 17 * 17 cm square, with about a cm underneath for silicon dampers.

Obviously a small closed enclosure would do, but I got it into my head to make it a folded transition, using the full depth of the cabinet (about 42cm for the silverstone LC16M htpc)

Image

I'm thinking about using a fostex FE 107E full range driver, which is 10cm across, pdf datasheet is here http://www.lautsprechershop.de/pdf/fostex/fe107e.pdf

Has anyone seen any enclosures like this? I'm thinking if I can find something similar I can just adjust the depth of the cabinet to get the transmission line right.
Am I pushing my luck with such a small baffle?
Is the end of the transmission line too small?
Is it even going to be long anough at about 80cm?
I once had more of an idea of what a THX speaker required, but I'll prolly work towards a 80hz crossover to the sub. Looking at the data sheet 80hz is also the point where the Fostex needs a bump

I'm not asking for someone to do the math for me, just if anyone can give me advise before I continue with the design.
Cheers!


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PostPosted: 09 Jan 2009, 13:35 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi L2GX, welcome to the forum.

That looks interesting. Unfortunately I have never seen a design along those lines. What software did you use and how do the results look?

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PostPosted: 11 Jan 2009, 06:05 
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Joined: 09 Jan 2009, 07:52
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http://www.t-linespeakers.org/projects/yves/index.html

This is my inspiration, since he gets 40hz quarter length wave with stuffing I hope I can get 80 hz with half the transmission length. Obviously his speaker has a baffle wraparound effect as the port exits in the back. Mine exiting in the front shortens the tl even more...

I'm still trying to wrap my head back around speaker calculating, I mailed the designer to see which sheet he used. If all else fails I'll start with M.J. King's sheets and then go into mathcad.
Either way I'l have to order the driver and run it a while before I do the final measurments on it. Then I can design a bespoke enclosure.


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PostPosted: 12 Jan 2009, 11:24 
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I'm not familiar with doing the math by hand, but there are alignment tables on Martin's site:
http://www.quarter-wave.com/TLs/TL_Theory.html
Sorry I can't be much more help than that.

I found that after breaking the driver in for a couple of hours near max excursion the T/S parameters did not change much with continued break in.

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