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Old 7th November 2007, 07:46 PM   #121
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Scott,

I'm about ready to start cutting wood for a Half Chang w/ FE206E driver. I was going to build a Suzy Chang for my daughter and son-in-law for Christmas, but after hearing Bob's HC, I couldn't help myself!

Looking at the drawings, I am wondering if I can move the front baffle out to the edge of the sides rather than being recessed into the side panels. This will add about 200 cubic inches to the volume of the chamber (3/4 inch depth.) A portion of this will be off-set by the internal braces (and perhaps the damping material as well?) So…

1) Is this volume increase significant?

2) Could I, or should I, compensate by lowering the height of the chamber by an inch? (Figuring that's slightly more than half of the volume increase, with the braces covering most of the remainder.) Or are the ratios of the dimensions critical?

Thanks for your help!
Jim
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Old 7th November 2007, 09:32 PM   #122
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Don't change the length or the tuning frequency will be altered. It's more a short MLTL than a reflex box in this sense. You could move the front panel forward if you wished -I don't think the difference will be especially significant. You just might need a slightly larger resistor on the 206.
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Old 8th November 2007, 06:48 AM   #123
Solve is offline Solve  Sweden
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Would the Half Chang work with Visaton B200?

Solve
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Old 8th November 2007, 07:46 AM   #124
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Quote:
Originally posted by Solve
Would the Half Chang work with Visaton B200?
It works in Lorenna which is a BVR, so it can probably work in a chang... it doubt it wil be the same size as Half thou.

dave
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Old 8th November 2007, 01:27 PM   #125
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Scott,

Thanks very much! I really appreciate your sharing your expertise.

Cheers, Jim
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Old 12th November 2007, 06:40 AM   #126
drongo is offline drongo  Australia
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Default DX3s in Half Chang Box?

Greetings all

I recently acquired a pair of DX3s (before the price hike!). I've put off building cabinets 'cos in part I've been unable to decide what to do with the things. 1st thought was the Bob Brines LT2000 (My FT 1600MIIs are great) The BIB looked good, but so big and unsure how it would sound in my living room? Enter Half Chang - could I just drop the DX3s straight into this box? I note that MJK and BB have both designed cabinets that take both fostex and lowther 8 inchers.

Assuming the cabinet is OK, would I use the BSC described earlier in this thread as a starting point ? My preference would be to cannabalise the 1.5 Mh inductor from the FT1600s.

I have read this thread with much interest. Any advice much appreciated.

-R
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Old 12th November 2007, 12:09 PM   #127
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The Lowther would require a substantial redesign (i.e. a completely new cabinet), though it'd be possible to do one.
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Old 12th November 2007, 01:58 PM   #128
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Scott,

It finally occurred to me: I don't need to change the chamber at all! Just build according to plan like Bob did, then add another 3/4" piece on the front baffle going out to the edges to get the look that I want. And it can't hurt to have the driver on 1.5" of ply rather than 3/4". Total win-win.

Now that I know what I'm doing, I can get started--as soon as I'm finished with the astronomy club newsletter. (Actually, I did cut up some scrap wood to mount the 206s on OBs for break-in.) Good thing I'm mostly retired. No time left for work!

Cheers, Jim
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Old 14th November 2007, 05:20 AM   #129
slomatt is offline slomatt  United States
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Does anybody have first-hand experience in the sound quality differences between a full chang (ie two horns) and a half chang? I'm trying to decide between the two designs for a pair of B20FU drivers, and the half chang is appealing because of the smaller size.

The only two acoustic differences I can think of are that with the half chang there is half the horn area which means the air in the horn will have twice the energy put into it, and since the single horn is closer to the floor the room coupling may be slightly higher and the "sonic bubble" will not be symmetrical around the driver.

But, the above is just theory, has anybody compared the half to full changes using the same driver? Alternatively, can someone with a deeper understanding of the design hypothesize as to potential differences in sound?

Thanks.

- Matt
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Old 14th November 2007, 05:33 AM   #130
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I am having the same dilemma, however I have decided on the half-changs for the sake of a smaller cabinet. There is definitely a decrease in efficiency, but looking at the response graphs it doesn't look very significant (I think 2ish db?). There might be some imaging advantages for the double vent, and for that someone more knowledgeable can chime in

Cheers,
Serg
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