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
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
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.
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
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
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
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
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
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
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
Cheers,
Serg
Therein lies one of the problems of computer modelling. It doesn't tell you how a cabinet will sound, and we're largely in the subjective domain here.
The double vent versions will share the general house-sound of overall smoothness & extension, but have some distinct differences over the single vent cabinet. The latter will sound as you expect -a relatively large reflex cabinet with a vent coupled to a large quantity of air, so the sonic presentation will be on the scale of a horn. It will sound much more spacious than a small-vent cabinet.
The double vent cabinets will both provide an even larger scale to the soundstage. Many find they give superior dynamic punch in the mid & upper bass (don't ask me why, but I've found the same) and a superior depth perspective compared to the single vent cabinet. They will be of slightly higher efficiency too, though the frictional losses of the twin vents will reduce the gains slightly compared to the theoretical 'ideal.' Of the doubled cabinets, the flat fronted version gives all the aforementioned with a relatively easy build. The curved version is harder to construct comprared to the flat froonted type, but adds to the mix rock-solid LF image placement & reduced distortion due to its reshaping of the wavefront & integration of the two mouths.
Hope that helps a bit
Scott
The double vent versions will share the general house-sound of overall smoothness & extension, but have some distinct differences over the single vent cabinet. The latter will sound as you expect -a relatively large reflex cabinet with a vent coupled to a large quantity of air, so the sonic presentation will be on the scale of a horn. It will sound much more spacious than a small-vent cabinet.
The double vent cabinets will both provide an even larger scale to the soundstage. Many find they give superior dynamic punch in the mid & upper bass (don't ask me why, but I've found the same) and a superior depth perspective compared to the single vent cabinet. They will be of slightly higher efficiency too, though the frictional losses of the twin vents will reduce the gains slightly compared to the theoretical 'ideal.' Of the doubled cabinets, the flat fronted version gives all the aforementioned with a relatively easy build. The curved version is harder to construct comprared to the flat froonted type, but adds to the mix rock-solid LF image placement & reduced distortion due to its reshaping of the wavefront & integration of the two mouths.
Hope that helps a bit
Scott
Definitely helps a lot Scott thanks! Being a college student though, I don't think I want to be carrying those large double vents everywhere I move I think I will stick with the Half-chang, unless the Demetris is worthy of consideration. So many choices and so much knowledge in this forum, sometimes its overwhelming
I think I will stick with the Half-chang, unless the Demetris is worthy of consideration. So many choices and so much knowledge in this forum, sometimes its overwhelming 
Given that there are only a couple in existance at present, I very much doubt it. But it's like comparing a hippo with a rhino -beyond the fact that they're both loudspeakers, and have the ability to use the same driver, they're completely different so comparisons are next to impossible. One's a pipe-horn, the other is a BVR. There are plenty of descriptions on the sonic traits of both types, so which a person prefers ultimately will be down to preference and the room they are to be used in.
This is why diyaudio.com is great, thank you for the informative posts!
The extra build complexity of the curvy version is not a deterrent, so I guess I'll have to decide between a curvy full chang and a curvy half chang. I have a feeling that I'll be going with the full curvy chang based on Scott's comments, I just have to see how it will fit in the room.
The slight problem is that I already have three pairs of speakers at my house so I really don't need any more. My father is interested in replacing his late 80's VMPS towers, but the B20FUs will likely not have the amount of bass he is looking for. Hmmm... I guess there's always room for another set of speakers around the place.
I'll keep the site updated on progress, thanks again!
- Matt
The extra build complexity of the curvy version is not a deterrent, so I guess I'll have to decide between a curvy full chang and a curvy half chang. I have a feeling that I'll be going with the full curvy chang based on Scott's comments, I just have to see how it will fit in the room.
The slight problem is that I already have three pairs of speakers at my house so I really don't need any more. My father is interested in replacing his late 80's VMPS towers, but the B20FUs will likely not have the amount of bass he is looking for. Hmmm... I guess there's always room for another set of speakers around the place.
I'll keep the site updated on progress, thanks again!
- Matt
I believe that the fulll chang would sound a little better than the half change, but that the half chang has a higher driver height so it would sound a little better in that way. My only issue with my Harveys are that the driver is too low and putting them on stands does not look right at all. It is deciding on which trade off you prefer, personally I am leaning towards higher driver height (half changs).
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