Here are pics of prototype cabinets in the X-baffle design in 'real' wood 
I finally worked out the construction details and the compression chamber issues.
The box on the right is the one I will go with, although, aesthetically, I would prefer it be 3 or 4 inches shorter. I may do that in the final build.
This is prototype #6. I'm can say with certainty that foam works great for prototyping. Other than an increase in resolution and tightened bass, the overall sound did not change from foam to wood. I'm working on stuffing right now. Without it, they "honk" on vocals. Stuffing made a world of difference. I don't know the exact amount yet.
How do they sound? I think great. They have a huge soundstage. It's hard to find a sweet spot (I don't know if that is a good thing or a bad thing). Beaming issues are minimal that I can tell. Highs are sweet and crisp. Mids are as expected from this driver (excellent) Bass is a lot better than I expected. Put them right into a corner, and they actually got boomy on some recordings (I think this is an issue of bracing more than anything).
H x 45 inches, W x 16 inches, D x 12 inches. Baffle angle is 36.5 degrees.
I finally worked out the construction details and the compression chamber issues.The box on the right is the one I will go with, although, aesthetically, I would prefer it be 3 or 4 inches shorter. I may do that in the final build.
This is prototype #6. I'm can say with certainty that foam works great for prototyping. Other than an increase in resolution and tightened bass, the overall sound did not change from foam to wood. I'm working on stuffing right now. Without it, they "honk" on vocals. Stuffing made a world of difference. I don't know the exact amount yet.
How do they sound? I think great. They have a huge soundstage. It's hard to find a sweet spot (I don't know if that is a good thing or a bad thing). Beaming issues are minimal that I can tell. Highs are sweet and crisp. Mids are as expected from this driver (excellent) Bass is a lot better than I expected. Put them right into a corner, and they actually got boomy on some recordings (I think this is an issue of bracing more than anything).
H x 45 inches, W x 16 inches, D x 12 inches. Baffle angle is 36.5 degrees.
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I will certainly use baltic birch at a minimum. The front baffles as they now stand are quite dead even with 1/2 inch (18 mm?) MDF. This is due to the internal bracing. The curved back will have to be thicker or better braced as it still resonates quite a bit at the bottom. I'm still working on how best to overcome that. So I'm thinking 1/2 inch material for the front and 3/4 for the back.
Curving the back was the hardest part of construction. I thought I could bend a 1/2 inch piece of MDF that size. HA!. No way with one person and a bunch of clamps. I had some 1/4 inch plywood that I doubled up that barely worked (look at all the screws in picture #2). To do a curved back, I will have to either build a form and pre-curve the back or laminate thinner peices. 1/8 ply should be quite easy, using epoxy for glue. I could also do a V-shaped back, but the curve looks too cool to not have it.
The other option is solid wood. It can be done with this design. The only problem I see is attaching the top. I have some air-dried quartersawn maple that would work very nicely. I always thought clear pine would make nice-sounding speakers too, but that's just a guess.
All in all, I'm quite happy with the sound so far.
Doug
Curving the back was the hardest part of construction. I thought I could bend a 1/2 inch piece of MDF that size. HA!. No way with one person and a bunch of clamps. I had some 1/4 inch plywood that I doubled up that barely worked (look at all the screws in picture #2). To do a curved back, I will have to either build a form and pre-curve the back or laminate thinner peices. 1/8 ply should be quite easy, using epoxy for glue. I could also do a V-shaped back, but the curve looks too cool to not have it.
The other option is solid wood. It can be done with this design. The only problem I see is attaching the top. I have some air-dried quartersawn maple that would work very nicely. I always thought clear pine would make nice-sounding speakers too, but that's just a guess.
All in all, I'm quite happy with the sound so far.
Doug
"Bremertones" Well, that's a lot better than "Prototype #6"
In summary, I chose this design trying to get the benefits of OB and BLH together. I started with Fostex's recommended enclosure for this driver, using the internal dimensions of their box. The internal line length is 77'ish inches, and the compression chamber is 1,560'ish cm2. (sorry, my notes are in the shop).
I then played around with different mockups in 1/2 inch foam until I came to this basic design, doing fast-switching near-field A:B testing extensively. There is much to be discovered yet, though. I can say this with certainty that the V below the driver "livens" up the sound considerably. If you leave the V on top of the driver (see left speaker in Post #1), the sound is too "live," for this driver anyway.
I'm very happy with the use of 4-inch ABS plastic pipe to mount the driver. It's a perfect fit. Drilling the hole was quite an adventure. The increase in music resolution was quite noticable over a box-type compression chamber. The volume of the ABS pipe accounts for about half the total volume of the CC, with the rest being a V-shape inside the cabinet. I will attempt to find or build a more 'elegant' solution on my final build, but it will be circular.
Here is a photo with the top off. The small stuffed V in the front is the rest of the compression chamber. The backwave exits downward from the driver about 8 inches, goes up to the top (see the middle baffle), and then goes downward again at the back of the cabinet to the bottom, exiting the vents. I originally tried a two-part line (like Terry Cain's BIB), but it misses something. Doing it in three three parts just sounds better to me.
In summary, I chose this design trying to get the benefits of OB and BLH together. I started with Fostex's recommended enclosure for this driver, using the internal dimensions of their box. The internal line length is 77'ish inches, and the compression chamber is 1,560'ish cm2. (sorry, my notes are in the shop).
I then played around with different mockups in 1/2 inch foam until I came to this basic design, doing fast-switching near-field A:B testing extensively. There is much to be discovered yet, though. I can say this with certainty that the V below the driver "livens" up the sound considerably. If you leave the V on top of the driver (see left speaker in Post #1), the sound is too "live," for this driver anyway.
I'm very happy with the use of 4-inch ABS plastic pipe to mount the driver. It's a perfect fit. Drilling the hole was quite an adventure
. The increase in music resolution was quite noticable over a box-type compression chamber. The volume of the ABS pipe accounts for about half the total volume of the CC, with the rest being a V-shape inside the cabinet. I will attempt to find or build a more 'elegant' solution on my final build, but it will be circular.Here is a photo with the top off. The small stuffed V in the front is the rest of the compression chamber. The backwave exits downward from the driver about 8 inches, goes up to the top (see the middle baffle), and then goes downward again at the back of the cabinet to the bottom, exiting the vents. I originally tried a two-part line (like Terry Cain's BIB), but it misses something. Doing it in three three parts just sounds better to me.
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I don't really follow the OB part.
That rear pathway looks like some kind of torture chamber. Don't stick your arm in there.
Are the pathways of equal cross sectional area, so it results in some type of MLTL, or are those interior panels angled? Have you plugged the dimensions into MJK's spreadsheets?
With those size panels you definitely need some bracing and until you do so, you won't know what kind of bass you're getting, because I think you've got some resonance mixed in.
Other than bracing, my only recommendation would be to try a large piece of foam as a front baffle around the driver. I believe your tonality will flesh out quite a bit with deeper 1/2 space launching of the front wave. It will make for a good easy A/B comparison for you.
That rear pathway looks like some kind of torture chamber. Don't stick your arm in there.
Are the pathways of equal cross sectional area, so it results in some type of MLTL, or are those interior panels angled? Have you plugged the dimensions into MJK's spreadsheets?
With those size panels you definitely need some bracing and until you do so, you won't know what kind of bass you're getting, because I think you've got some resonance mixed in.
Other than bracing, my only recommendation would be to try a large piece of foam as a front baffle around the driver. I believe your tonality will flesh out quite a bit with deeper 1/2 space launching of the front wave. It will make for a good easy A/B comparison for you.
John,
OB as in a wider front. Probably a bad analogy, but I don't know how else to describe it. It is what it is.
Yes, the rear pathway is nasty. I had to use the nail gun to get the second layer of plywood to hold its curve, but the shortest nails I had were 5/8 inch, hence the 1/8" proud. Remember, this is only a prototype.
The pathways are equal, as are Fostex's. I tried doing the figures for angling the internal baffles to get closer to an exponential increase, but my math skills are sorely lacking in that respect. I just wanted to get the darn things built to see if I had something or not. Ideally, I would like them angled. I have not used MJK's spreadsheets yet. Perhaps I should, but I like what I hear so far.
I agree on bracing. The front pieces are quite dead now, even at louder volumes. The back does vibrate quite a bit at the bottom because the brace on the back only goes down halfway.
I understand your foam recommendation. I have considered it, but figured I would try it this way first. Wouldn't the 1/2 space launching be off the angled baffles already? That is, unless they are set back too far to count. Thanks for the input. This is still very much a work in progress.
Doug
OB as in a wider front. Probably a bad analogy, but I don't know how else to describe it. It is what it is.
Yes, the rear pathway is nasty. I had to use the nail gun to get the second layer of plywood to hold its curve, but the shortest nails I had were 5/8 inch, hence the 1/8" proud. Remember, this is only a prototype.
The pathways are equal, as are Fostex's. I tried doing the figures for angling the internal baffles to get closer to an exponential increase, but my math skills are sorely lacking in that respect. I just wanted to get the darn things built to see if I had something or not. Ideally, I would like them angled. I have not used MJK's spreadsheets yet. Perhaps I should, but I like what I hear so far.
I agree on bracing. The front pieces are quite dead now, even at louder volumes. The back does vibrate quite a bit at the bottom because the brace on the back only goes down halfway.
I understand your foam recommendation. I have considered it, but figured I would try it this way first. Wouldn't the 1/2 space launching be off the angled baffles already? That is, unless they are set back too far to count. Thanks for the input. This is still very much a work in progress.
Doug
Taperwood said:
IB or infinite baffle (quasi IB would be better).. not open baffle (which is VERY different in that it refers to free-air dipole operation).
Questions about the pvc pipe:
1. Is it short termination? (i.e. does it extend only a bit into your labyrinth?)
2. Have you placed stuffing in it or is it "bare"?
Scott,
The pipe is flush with the baffle in the back. In other words, it is notched in a V shape. I drilled the hole, slid the pipe in and positioned where I wanted it, scribed the back, and then cut it on a bandsaw (nervewracking), and then used files, etc., to clean it up.
On these speakers, I extended the pipe 1 inch beyond the small V in front to give it as much volume as possible. If you made the pipe the entire CC, it would extend well into the speaker, almost to the back, blocking everything.
There is no suffing at all behind the driver at this point. I refer you to the photo of the top. The stuffing in the small V at the front is dead air. There is a V-shape block down 4-5 inches to terminate the CC at its appropriate volume.
I wish I could spend all day futzing around with these, but life keeps interfering. I'm happy with the overall design, and now I am ready to try these small tweaks that are being suggested.
Doug
The pipe is flush with the baffle in the back. In other words, it is notched in a V shape. I drilled the hole, slid the pipe in and positioned where I wanted it, scribed the back, and then cut it on a bandsaw (nervewracking), and then used files, etc., to clean it up.
On these speakers, I extended the pipe 1 inch beyond the small V in front to give it as much volume as possible. If you made the pipe the entire CC, it would extend well into the speaker, almost to the back, blocking everything.
There is no suffing at all behind the driver at this point. I refer you to the photo of the top. The stuffing in the small V at the front is dead air. There is a V-shape block down 4-5 inches to terminate the CC at its appropriate volume.
I wish I could spend all day futzing around with these, but life keeps interfering. I'm happy with the overall design, and now I am ready to try these small tweaks that are being suggested.
Doug
Taperwood said:
I've suggested something like this numerous times.. but like many things I've suggested it doesn't seem to get "through". The concept is a laminar air flow. You can improve this further by waxing the inside of the pipe to give a smoother lower resistance surface. You could also stuff the pipe with drinking straws (which also reduces resonant behaviour - though it may not be a problem with your "v" termination), but sometimes reflections can be a problem from the honeycomb drinking straw end (..which can be cured via a silicone borscilate paint compound).
Anyway.. Nice Job!
John,
Taking the block out is certainly worth trying, but then I would be shooting in the dark as to where to stop. Right now, I'm trying to get the best sound out of what Fostex recommends, using their volumes and lengths, etc, but I'm definitely open to all suggestions. I'm without a decent amp right now, but I will try your foam suggestion as soon as I can. I think it's a good idea worth pursuing.
I originally intended to build the Buschorn II (sp?) with these drivers, and the first thing I did was build a prototype of that, but even my first effort in the X-baffle sounded better to me, richer, more fuller, so I started playing around with that design instead, just to give everyone some perspective.
Scott,
Did you suggest that to me? If so, that's why it didn't get through Anyway, if you looked at a piece of ABS, the inside is so smooth, it's shiny. I'm not sure wax would make any difference. I could try some stuffing in the pipe, behind the driver, or even in the V part of the CC to see what happens. Not sure what I would be listening for though.
Doug
Taking the block out is certainly worth trying, but then I would be shooting in the dark as to where to stop. Right now, I'm trying to get the best sound out of what Fostex recommends, using their volumes and lengths, etc, but I'm definitely open to all suggestions. I'm without a decent amp right now, but I will try your foam suggestion as soon as I can. I think it's a good idea worth pursuing.
I originally intended to build the Buschorn II (sp?) with these drivers, and the first thing I did was build a prototype of that, but even my first effort in the X-baffle sounded better to me, richer, more fuller, so I started playing around with that design instead, just to give everyone some perspective.
Scott,
Did you suggest that to me? If so, that's why it didn't get through
Anyway, if you looked at a piece of ABS, the inside is so smooth, it's shiny. I'm not sure wax would make any difference. I could try some stuffing in the pipe, behind the driver, or even in the V part of the CC to see what happens. Not sure what I would be listening for though.Doug
Taperwood said:Scott,
Did you suggest that to me? If so, that's why it didn't get through
Doug
Don't know.. I *think* the last time I went into detail on this is on Shin's Percieve (part 1) in the loudspeaker forum section. ..though I've probably mentioned it a few times on the fullrange section.
Stuffing should increase resistance and subjectivly "suck the life" out of the drivers. (the closer the stuffing to the driver, the worse the effect.) Waxing and polishing the tube may provide a small gain in subjective detail by decreasing the resistance marginally - though the greatest limitation at this "level" is the resistance provided by the suspension which should become more compliant with age/use. (..oddly enough I actually prefer the suspension on the cheaper fostex drivers IF excursion isn't required - in fact I think they are some of the best low x-max suspensions ever produced. .. well not the spider, but definitly the surround.) If the surface is already "slippery", then I wouldn't bother waxing and buffing.
Scott,
Just this afternoon I tried stuffing in the CC. I tried it directly behind the driver and also just in the V-shape part, both a lot and a little bit. You are right, the life is completely sucked out. It was like sticking your ear up to a midrange driver (well, not that bad but close). My wife stuck her head in the room and said "there's something wrong with that recording."
However, it seemed that vocal resolution was better, but I don't know if that was because it was so forward or something else going on.
Doug
Just this afternoon I tried stuffing in the CC. I tried it directly behind the driver and also just in the V-shape part, both a lot and a little bit. You are right, the life is completely sucked out. It was like sticking your ear up to a midrange driver (well, not that bad but close). My wife stuck her head in the room and said "there's something wrong with that recording."
However, it seemed that vocal resolution was better, but I don't know if that was because it was so forward or something else going on.
Doug
Taperwood said:
If your wife says that then you KNOW something is wrong. Funny thing is that it will actually measure better on a CSD plot. This is another classic case of measurements leading to a WRONG conclusion. This could have to do with the altered behaviour being wrong in the microsecond range and not the millisecond range. In otherwords every CSD plot I've seen is millisecond, not microsecond - and so it won't really be visible.
I bet another thing occured:
..centered imaging remained about the same (maybe better, maybe worse - likely moved forward near the plane of the speakers), but off center imaging probably sounds a lot closer to the speakers (perhaps even as if its comming from the speakers).
The cleaner vocals was likely a product of removing ambiant information from the track and leaving just the vocals/instruments. (..kinda like scrubbing out the sound stage.) My guess is that there would be very little change for tracks with close mic vocals and little or no hall-sound/reverb (..possibly a little better).
The funny thing is that topic seems to be restricted to the fullrange forum. The other so-called "progressive" forums dealing with "real" speakers never seem to talk about this (..except for the question "what happened to imaging depth?").
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