Thanks for the kind words. Funny that you're the fastest builder here, while I'm one of the slowest.
From what I've read here: http://www.diyaudio.com/forums/subwoofers/136411-karlson-dipole-sub-would-do-any-good.html
Rudolf got his point (in post#8) that the Karlson slot in a sub doesn't matter. I tend to agree (despite I'm not willing to), because the large wave lengths related to the physical size of the aperture.
So, my goal will be maximizing the upper usable range of a dual 18" KaZba (what a name, BTW). I wish it can be useable up to 300 Hz or so to have some midrange magic of the K (according to freddi)...
Another big problem from that and above. Since dual 18" is very big already, so line array (above that physically) is not feasible. Side by side is not good, either.
I've been thinking some 'planar' arrays, like the followings:
http://www.diyaudio.com/forums/multi-way/90804-large-midrange-ob-scott-g-10.html#post1953221
http://www.diyaudio.com/forums/mult...ontrolled-dispersion-tripole.html#post4097732
or even this: http://www.diyaudio.com/forums/full-range/164797-200-x-2-drivers-what-do-2.html#post2160121
I was told, multiple small midrange driver can be very good.
However, all those are massive, so I'm still thinking....
From what I've read here: http://www.diyaudio.com/forums/subwoofers/136411-karlson-dipole-sub-would-do-any-good.html
Rudolf got his point (in post#8) that the Karlson slot in a sub doesn't matter. I tend to agree (despite I'm not willing to), because the large wave lengths related to the physical size of the aperture.
So, my goal will be maximizing the upper usable range of a dual 18" KaZba (what a name, BTW). I wish it can be useable up to 300 Hz or so to have some midrange magic of the K (according to freddi)...
Another big problem from that and above. Since dual 18" is very big already, so line array (above that physically) is not feasible. Side by side is not good, either.
I've been thinking some 'planar' arrays, like the followings:
http://www.diyaudio.com/forums/multi-way/90804-large-midrange-ob-scott-g-10.html#post1953221
http://www.diyaudio.com/forums/mult...ontrolled-dispersion-tripole.html#post4097732
or even this: http://www.diyaudio.com/forums/full-range/164797-200-x-2-drivers-what-do-2.html#post2160121
I was told, multiple small midrange driver can be very good.
However, all those are massive, so I'm still thinking....
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CLS,
What about orienting the dual 18in facing each other in push pull sort of like typical slot loading setup (allows narrow front profile) and having K aperture facing front for where slot would normally be? Backside could also go through similar K aperture from a manifold box.
Thanks for pointing me out to Freddi's earlier thread on K dipole and Ron E's very similar design. His does not have the Z so can't be called a KaZba
. It was Freddi who gave me the idea and inspiration for the K dipole as well.
What about orienting the dual 18in facing each other in push pull sort of like typical slot loading setup (allows narrow front profile) and having K aperture facing front for where slot would normally be? Backside could also go through similar K aperture from a manifold box.
Thanks for pointing me out to Freddi's earlier thread on K dipole and Ron E's very similar design. His does not have the Z so can't be called a KaZba
. It was Freddi who gave me the idea and inspiration for the K dipole as well.
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I must have been thinking along these lines when I drew this up. Probably was for FF125K and did not require too large a Vb nor low a Fb. I never fleshed out the concept more.
Yeah, we discussed this concept on several occasions on Gregg Baker's (eeehaah) old forum. At least a couple people have tried various K/OB hybrids, AFAIK.
What I am most curious about is would there be any excursion reduction compared to a equivalently sized unfolded OB, or another folded type like an H baffle.
I addition to the advantages previously mentioned, I would add:
- small size compared to an equivalent unfolded open baffle
- air mass should raise effective Qms slightly, making specs of some drivers more OB appropriate
- (possibly) reduced excursion?
I was thinking a single 15", in sort of a shallow Klam. There wouldn't be 2nd harmonic cancellation of the double driver dipole, but nevertheless I think it'd be worth a try sometime. Never got around to it myself. This was in part inspired by Magnetar's 'Rosie'. Here was my idea posted a few years ago:
What I am most curious about is would there be any excursion reduction compared to a equivalently sized unfolded OB, or another folded type like an H baffle.
I addition to the advantages previously mentioned, I would add:
- small size compared to an equivalent unfolded open baffle
- air mass should raise effective Qms slightly, making specs of some drivers more OB appropriate
- (possibly) reduced excursion?
I was thinking a single 15", in sort of a shallow Klam. There wouldn't be 2nd harmonic cancellation of the double driver dipole, but nevertheless I think it'd be worth a try sometime. Never got around to it myself. This was in part inspired by Magnetar's 'Rosie'. Here was my idea posted a few years ago:
Ah, more interesting ideas are popping up
Greg's shallow Klam makes me think, how the orientation of the baffle's slant (related to aperture) influence the sound?
I mean, in a (normal) Karlson, the baffle's slant makes the shallowest point (of the cavity) pointing at the widest part of the aperture. In a Klam, it's the opposite -- the deepest point of cavity is in line with the biggest opening.
And, how do we define the path length for the resonance of 1/4 lambda? Or is this the wrong question?
IG's "X" baffle is brilliant ! I think it'd be very helpful to smaller drivers.
X, Merging the slot (of SLOB) and K-aperture is difficult. I've thought of that for a while and yet to have any good enough idea. The look is just not right. Oh well, I know the statement seems unscientific, but maybe not... (The looks, I mean, are in the views of logic instead of the finish.)
BTW, quite some years ago, I saw in the TV that Lockheed's fighter won the bid because the representatives of NAVY thought their plane looked right. And it'd fly right when it looks right. (At least it's a part of the whole decision. It becomes F-35 later.) On the other hand, the Boeing's proposal looks bad. (I felt the same way, too.) It lost the bid, despite it probably has better engineering overall. I'm not sure...
Interesting, huh.
Greg's shallow Klam makes me think, how the orientation of the baffle's slant (related to aperture) influence the sound?
I mean, in a (normal) Karlson, the baffle's slant makes the shallowest point (of the cavity) pointing at the widest part of the aperture. In a Klam, it's the opposite -- the deepest point of cavity is in line with the biggest opening.
And, how do we define the path length for the resonance of 1/4 lambda? Or is this the wrong question?
IG's "X" baffle is brilliant !
I think it'd be very helpful to smaller drivers. X, Merging the slot (of SLOB) and K-aperture is difficult. I've thought of that for a while and yet to have any good enough idea. The look is just not right. Oh well, I know the statement seems unscientific, but maybe not... (The looks, I mean, are in the views of logic instead of the finish.)
BTW, quite some years ago, I saw in the TV that Lockheed's fighter won the bid because the representatives of NAVY thought their plane looked right. And it'd fly right when it looks right. (At least it's a part of the whole decision. It becomes F-35 later.) On the other hand, the Boeing's proposal looks bad. (I felt the same way, too.) It lost the bid, despite it probably has better engineering overall. I'm not sure...
Interesting, huh.
8 inch woofers arrived
These $10 buyout 8 inch woofers from PE (I believe they are "Bravox" brand as that is the box they came in) arrived. They have a cheap look and feel to them as can be expected for a $10 8 inch driver, but they measure very closely to advertised specs on PE website. All four units were pretty consistent with about 89 dB sensitivity, about 37 to 40 Hz fs, and Qts of 0.51 to 0.54 and Vas of about 1.5 cu ft. I think they should work well for the KaZba. Now I have some good TS params to start modeling in Akabak.
http://www.parts-express.com/wfr800gs-8-poly-cone-rubber-surround-woofer-8-ohm--299-343
Here is the DATS v2 screenshot:
These $10 buyout 8 inch woofers from PE (I believe they are "Bravox" brand as that is the box they came in) arrived. They have a cheap look and feel to them as can be expected for a $10 8 inch driver, but they measure very closely to advertised specs on PE website. All four units were pretty consistent with about 89 dB sensitivity, about 37 to 40 Hz fs, and Qts of 0.51 to 0.54 and Vas of about 1.5 cu ft. I think they should work well for the KaZba. Now I have some good TS params to start modeling in Akabak.
http://www.parts-express.com/wfr800gs-8-poly-cone-rubber-surround-woofer-8-ohm--299-343
Here is the DATS v2 screenshot:
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Cheap is often appropriate of OB. I'm looking forward to seeing how this project works in real life.
One thing I've noticed is that mass really seems to help OB, more than most speaker types. I remember once swapping out a ply baffle with an identical but heavier one of MDF, and getting a surprisingly big improvement. That being so, I'm a little concerned about foamcore for this app, but who knows. You can always pile some books on top.
It might work if you high-passed the center of the flower, and low-passed the petals. Even then, you'd have some lobing issues, but it might be fun.
One thing I've noticed is that mass really seems to help OB, more than most speaker types. I remember once swapping out a ply baffle with an identical but heavier one of MDF, and getting a surprisingly big improvement. That being so, I'm a little concerned about foamcore for this app, but who knows. You can always pile some books on top.
It might work if you high-passed the center of the flower, and low-passed the petals. Even then, you'd have some lobing issues, but it might be fun.
Actually, my mini KaZba prototype has taught me that even with two little 3.5 in drivers, this OB concept generates a lot of pressure and really flexes the cabinet - causing noticeable buzz and vibrations. This tells me that the dual 8 inch will have to be something heavy like plywood at least. I am not going to bother with it in FC.
I've watched 3/4" plywood wings including Baltic birch deflect quite a bit: in regular vented Karlson and in a sealed rear chamber klam- that's why Transylvania went to 3/8" allthread through the front tying to reflector then back panel as any wing movement introduced undesirable modulation of the midrange. I'm not sure how to effectively brace the recent klam12 - maybe two dowels tied to one point on the "top" plate.
those buyout Peerless 8's other than Re aren't way far off from X's woofs - the Peerless will probably do a 2K5 xover
those buyout Peerless 8's other than Re aren't way far off from X's woofs - the Peerless will probably do a 2K5 xover
An externally hosted image should be here but it was not working when we last tested it.
I'm thinking the range of 300-3kHz, or 500-5kHz, with the central one covering this whole range while the outer 6 playing the bottom half of the range. It's said to have (more or less) constant directivity by decreasing radiating area with rising frequency. Will have to play with the xover by trial & error, if I really build it.
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Not to OT too much, get back to the Karlson.
I remember seeing somewhere someone reinforced the inner side of Karlson slot with something like plaster. Not sure if there's any frame or ribs inside the structure. The curvy surface looked solid. Can't find it now.
A small part similar to that can be seen in the left photo of this post: http://www.diyaudio.com/forums/multi-way/99491-lets-discuss-karlson-2.html#post2218844
And on the right, yes, the Forsman. Can't skip that when talking about dipole karlson, I guess. Pity there seems very few reviews on that.
Looks like solid wood in Forsman's wings. Beautiful, but far beyond my woodwork skill.
And, here's another enthusiast of dipole Karlson: Index
CLS,
You may have some comb interference with the hexagonal array of they go up that high. You will have a phasiness when walking around or moving your head a bit. But maybe with circular symmetry it's not as bad as a linear array of widely spaced 6.5inchers ?
Thanks for the link on the Forsman - Freddi pointed that out to me too. Nice looking speaker. I wonder if a large 12in dia PVC sewer pipe can be cut with jigsaw to achieve similar curved K for a dipole?
You may have some comb interference with the hexagonal array of they go up that high. You will have a phasiness when walking around or moving your head a bit. But maybe with circular symmetry it's not as bad as a linear array of widely spaced 6.5inchers ?
Thanks for the link on the Forsman - Freddi pointed that out to me too. Nice looking speaker. I wonder if a large 12in dia PVC sewer pipe can be cut with jigsaw to achieve similar curved K for a dipole?
I was wondering when someone would bring up snkby. I didn't understand what the goal was at the time he was posting those builds, but I get it now.
FWIW, if you wanted to make a fancy version of these, plywood half cylinders can be purchased from this company.
FWIW, if you wanted to make a fancy version of these, plywood half cylinders can be purchased from this company.
Progress on dual 8in KaZba
I made some good progress with the build using triple laminated foam core and cardboard sandwich. This time the layers are bonded with 3M spray contact cement (77 Fastack). Installed the drivers and took some baseline measurements without K aperture and got surprising base extension (40Hz -3dB) as an H frame Z baffle. The top end extension does indeed reach a 750Hz XO. I tried it as a FAST with the Nautaloss trapezoid baffle (shown here with a Tang Band W4-1310SB provided courtesy Godzilla). Box internal dimensions are 12in wide x 18in tall x 9in deep.
I made some good progress with the build using triple laminated foam core and cardboard sandwich. This time the layers are bonded with 3M spray contact cement (77 Fastack). Installed the drivers and took some baseline measurements without K aperture and got surprising base extension (40Hz -3dB) as an H frame Z baffle. The top end extension does indeed reach a 750Hz XO. I tried it as a FAST with the Nautaloss trapezoid baffle (shown here with a Tang Band W4-1310SB provided courtesy Godzilla). Box internal dimensions are 12in wide x 18in tall x 9in deep.
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