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Joined 2003
Yes, the W26 is a magnesium/aluminum alloy. Relatively speaking, I was actually impressed with the midrange performance since Seas promotes it as a pure woofer. The 18Sound is quite good up through 1k, but all done in by 2k so I'm using steep slopes at 1.5k plus a mild notch filter at 2k.
So the "problem" is the gap between 1k where the midrange starts to go south, and 1.5k where the 11-12" WGs actually provide the desired directivity. (This is really an excuse to play, so I'm not complaining.) The challenge is to bring WG directivity lower, or find a way to take midrange breakup higher...or both to gain a little flexibility in XO choice.
Next for the midrange, is a quad of smaller drivers arranged in a square. The idea is to provide the directivity of a 15", but with the 6k breakup of a 7". Hopefully, the drivers arrive later this week. I now have ribbons in WGs at 950Hz, but the WGs are NG...the second set of WGs are nearly done. If the ribbon WGs don't do the job, I may look Ed up for some large-format compression driver WGs
Jeff,
Subjectively, how do you like the directivity of your horns? HF pattern okay for two or more people listening?
Paul W said:
I don't. That is the biggest drawback of the system. At my 2m listening distance there is only one listening position.
As strongly as I dislike the directivity, it is more than balanced by the sound quality in the sweet spot. It is AMAZING. It does all the hi-fi tricks (superb depth and imaging, detail) AND all of the horn tricks (immediacy, dynamics).
At some stage I want to experiment with a rearward or upward facing driver in parallel (but with it's own amp) above 5kHz. I don't think this extra driver will help the off-axis listening positions, but I can hear the power response problem sitting in the sweet spot and maybe it will help this. This is the one area where the large multicells I used to use are better.
Paul W said:
Next for the midrange, is a quad of smaller drivers arranged in a square. The idea is to provide the directivity of a 15", but with the 6k breakup of a 7". Hopefully, the drivers arrive later this week. I now have ribbons in WGs at 950Hz, but the WGs are NG...the second set of WGs are nearly done. If the ribbon WGs don't do the job, I may look Ed up for some large-format compression driver WGs
Oooohhh! A Legacy Audio design!
Have you futzed with the Edge yet to see what sort of combing cancellation works best?
Which drivers?
Wow.. LOTs to do recently!
New forum name "Paul W Projectmeister"
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Joined 2003
Jeff,
What flare family are you horns? Approximate overall dimensions? Are they flat on axis? Can you tell if the excess directivity is entirely a function of the horns, or does the 1.4" exit play a role?
Please forgive all the questions, but I don't have the opportunity to hear good horns often enough, so trying to develop a sense for the different horn designs.
Scott,
Business travel is way down this year (110k miles in 7 months last year) so more time for speakers.
Yes, the Edge and BDS are part of my standard kit bag. The "4-square" is borrowed from a Scandinavian design I saw a while back. I'm using RS-180's but, because of their eventual purpose, they are really compromised compared to what could be done for dedicated OB mids. The 180's are going into large, extremely stiff, sealed boxes and will become the base/bass modules for new floorstanding side channel speakers...so only a short stint as midrange. If not building WGs at the same time I'd go through a 4-square OB stage but with no shortage of projects, headed straight to the sealed boxes.
What flare family are you horns? Approximate overall dimensions? Are they flat on axis? Can you tell if the excess directivity is entirely a function of the horns, or does the 1.4" exit play a role?
Please forgive all the questions, but I don't have the opportunity to hear good horns often enough, so trying to develop a sense for the different horn designs.
Scott,
Business travel is way down this year (110k miles in 7 months last year) so more time for speakers
. Yes, the Edge and BDS are part of my standard kit bag. The "4-square" is borrowed from a Scandinavian design I saw a while back. I'm using RS-180's but, because of their eventual purpose, they are really compromised compared to what could be done for dedicated OB mids. The 180's are going into large, extremely stiff, sealed boxes and will become the base/bass modules for new floorstanding side channel speakers...so only a short stint as midrange. If not building WGs at the same time I'd go through a 4-square OB stage but with no shortage of projects, headed straight to the sealed boxes.
Ah, now I get it, those W26 are actually from the W18/W22 family, with all the goodies in the motor and phaseplug etc. Still, seeing they are recommended up to 1000 Hz they're not exactly subs... I think the comparison is fair.
Re: Jeff's system - I suspect with a 2nd order X-O at 400 Hz the off axis performance will be heavily affected by directivity issues between horn and omni woofer. You're likely getting severe imbalances including nulls off-axis, due to the mismatch and resulting messed up phase relationships. So it's more than just missing highs or such, it's mangled phase/timing, and that in turn will affect imaging etc. Using that 15" woofer in dipole mode might improve off-axis system performance dramatically. Or, of course, why not go for a 60Hz horn . A barn sized living room might be necessary though
Horn design and measurement. Well, I may sound like a broken record - I just can't afford much playing around with expensive equipment right now and my CNC enabled friend was moving his shop, so I am a bit of a toothless tiger these days - but eventually this horn I was presenting earlier *will* be built and then we'll have at least some idea whether it can go down to 1k or less and keep directivity OK.
Paul, the square and the WG's for the ribbons and all - I thought your rationale had been, if I remember your words, a "smaller package"?
Re: Jeff's system - I suspect with a 2nd order X-O at 400 Hz the off axis performance will be heavily affected by directivity issues between horn and omni woofer. You're likely getting severe imbalances including nulls off-axis, due to the mismatch and resulting messed up phase relationships. So it's more than just missing highs or such, it's mangled phase/timing, and that in turn will affect imaging etc. Using that 15" woofer in dipole mode might improve off-axis system performance dramatically. Or, of course, why not go for a 60Hz horn
. A barn sized living room might be necessary though Horn design and measurement. Well, I may sound like a broken record - I just can't afford much playing around with expensive equipment right now and my CNC enabled friend was moving his shop, so I am a bit of a toothless tiger these days - but eventually this horn I was presenting earlier *will* be built and then we'll have at least some idea whether it can go down to 1k or less and keep directivity OK.
Paul, the square and the WG's for the ribbons and all - I thought your rationale had been, if I remember your words, a "smaller package"?
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Joined 2003
Paul W said:
You are right...the domestic deal is "smaller". So anything less than 6 feet tall qualifies
Whatever the result, it will be a bit smaller.
If you want to get a substantial waveguide/horn going for a ribbon then consider a symmetrical form - i.e. a "flare" that is exactly the same on both sides of the ribbon (..dipole of course). (..something to do with "load" on the ribbon.)
Otherwise you are stuck with only extremely shallow waveguides/horns.
Paul W said:
The horns are Le Cleac'h expansion exponentials - I forget the "T" factor, but I expect they are quite similar to a tractrix in profile. They are 80cm in overall diameter and around 73cm long.
The frequency response is as you'd expect on such a large horn - there is a 6db/octave drop above 5kHz. It's interesting that the EQ filter I use is almost identical to the one Hiraga uses to correct the response of his large multicells. Maybe that is to be expected as they are probably similar in their expansion rates.
While horns that are not constant directivity are always going to be directional above a certain frequency, I think the severity of the directionality is almost entirely due to the length of the horn and seating distance. There is only one seat where you have a line of sight to the phase plugs of both drivers. I need a bigger room, but this isn't going to happen for quite a while.
MBK said:Re: Jeff's system - I suspect with a 2nd order X-O at 400 Hz the off axis performance will be heavily affected by directivity issues between horn and omni woofer. You're likely getting severe imbalances including nulls off-axis, due to the mismatch and resulting messed up phase relationships. So it's more than just missing highs or such, it's mangled phase/timing, and that in turn will affect imaging etc. Using that 15" woofer in dipole mode might improve off-axis system performance dramatically. Or, of course, why not go for a 60Hz horn
It's a good thing I don't listen off-axis!
I'm using a 4th order active XO at 400Hz, but I think it exhibits some off-axis weirdness too being even order. I'm not well studied on crossovers, but that will change soon. Now that the tonal balance of the horn is sounding right I need to pay some attention to the crossover.
I'm sure it exhibits all of the problems you mention, but that excites me as it means it can sound better than it already does! I intend to try JMMLC's phase coherent 3rd order crossover at some stage. The LF are just good drivers thrown in a poor and ill suited but free box (I've blocked up some of the port to "tune" it.) Many problems to fix, but it still sounds amazing!
Jeff
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Joined 2003
Yes, that would really great to try with more room behind the speakers, especially with 270 degree roundovers connecting a double WG. But, it would get very large very quickly. Just a simple 90 degree WG with large RO for now.
That's good to know 'cause my head keeps saying quick-opening CD...but those big horns are works of art! Are you using 1.4 or 2" exit drivers? (I thought you said 1.4, but I also saw a reference to 2"?)
Hi Jeff,
if the directivity mismatch between woofer and horn is the cause (which I believe), then I don't think you can cure the off-axis response via crossover tuning, unless you are very lucky after a lot of trials. Basically a boxed woofer will have omnidirectional characteristics at those frequencies - no falloff off-axis. The horn will have its characteristic directivity, with falloff as a function of angle and frequency. Now if as a function of angle, amplitude decreases, this automatically means that off axis the horn phase is different from the woofer phase, to a varying degree, even if they are perfectly matched on-axis. And of course both angle and frequency will affect by how much.
The easiest way to get the phase of woofer and horn to "agree" more or less even off axis, is to make the woofer to become almost as directional as the horn. From then on a rather simple crossover will do. 4th order active as you already have, seems like a good choice anyway.
Paul W said:
It seems I have seen this several years back...
IIRC, that's a great piece of work for a speaker design competition (with maximum weight limit of 100kg). It's composed by a Raven ribbon tweeter, 4 * 7inchers in a diamond shape open baffle (with Raven in the center), & 4 *15inchers in a V-shape open baffle...
I searched on google for a while just now but found nothing.
Does anyone else remember this?
Dear ScottG,
I have read your ideas on manufacturing a horn in posts 169 and 171; a structure of the horn essentially comprising a shell and a material for filling the shell. I will term the filler material – a kernel.
The manufacturing process, building the shell first and than filling it with the kernel, is, however, rather involved as you have concluded.
I have been considering the same structure, and I believe that I have a good method for building it, but by an inverse process: the kernel firs and then adding the shell around the kernel.
I was wondering what material would you recommend for the kernel, considering that I need to be able to shape it using basic tools, saws (circular and band), grinders, routers, and the like. Could you suggest a thickness of such kernel for the appropriate property, which I understand to be non-resonant, and sound absorbent (to prevent the sound leaking from inside to outside)?
Thank you,
M
I have read your ideas on manufacturing a horn in posts 169 and 171; a structure of the horn essentially comprising a shell and a material for filling the shell. I will term the filler material – a kernel.
The manufacturing process, building the shell first and than filling it with the kernel, is, however, rather involved as you have concluded.
I have been considering the same structure, and I believe that I have a good method for building it, but by an inverse process: the kernel firs and then adding the shell around the kernel.
I was wondering what material would you recommend for the kernel, considering that I need to be able to shape it using basic tools, saws (circular and band), grinders, routers, and the like. Could you suggest a thickness of such kernel for the appropriate property, which I understand to be non-resonant, and sound absorbent (to prevent the sound leaking from inside to outside)?
Thank you,
M
mefistofelez said:
Then this depends on the type of horn (conical and non-conical).
If its conical then definitely use the lathe approach (typically from "butcher block" maple). Alternatively you can make it from plaster or cement (for that I'd contact Jean Michael). Note that you don't even need to purchase a "real" lathe if you decide to do it with wood.. You can always make your own lathe (do a web search for that if you are interested).
If its NOT a conical horn.. well then thats VERY difficult.. The reason is that its difficult to hand shape a horn with a high degree of accuracy (particularly because its difficult to measure it with accuracy).
OK then, IF you go the "shaping" route..
2 methods here:
1. Continue to use the shaped "kernel" material (as you put it). Basic Surfboard construction. Do a web search on that for more details.
2. Remove the "kernel" material. Probably a very hard modeling clay. After setting up a binder material like fiberglass on the modeling clay, and then applying resin and waiting for it to "set-up"/dry, remove the clay.
You can improve accuracy with a flare cutout (a 2d negative) of the throat expansion and mouth round over. At least 2 flare cutouts - one vertical and one horizontal. (..of course if its elliptical then you have problems near the "corners" of the horn flare when using a simple 2d negative.) ..push the cut-out flare into the horn mouth and if the horn walls match the flare then everything should be OK.
2 critical things about a horn and "dampening"..
1. The horn needs to have a VERY stiff (high tensile strength) wall construction - resin (depending on the type) can easily accommodate this requirement.
2. The horn's walls should be "moderately" thick to avoid resonating.. say 1/4 of an inch near the driver and about double that near at the mouth edge expanding in thickness as you move from driver to mouth (..assuming no "kernel"). If you do have a "kernel", well that depends on the material - IF its the foam used in surfboards then perhaps 3 times that amount or more.
If you need to dampen a horn after its built.. this is the stuff:
http://www.sunsetent.com/Categories/quakesecure.html
I don't mean to be a dick, but stiffness and tensile strength aren't the same thing. Stiffness is a quality that is proportional with the modulus of elasticity, and is basically the resistance to deform when a load is applied. Tensile strength is the measure of how much tensile load there can be before the material yields.
</material science 101>
I think it's just stiffness you want, not tensile strength.
</material science 101>
I think it's just stiffness you want, not tensile strength.
Dear ScottG,
thank you for the detailed answer, however, I am afraid that I sitll failed to communicate my question.
The horn will comprise an inner "kernel" and an outer "shell".
For the "shell" I was condidering either fibreglass/kevlar or veneer (built to about 0.125 inches on each surface - inner and outer of the "kernel").
My question is what material and thickness would be best for the "kernel".
M
thank you for the detailed answer, however, I am afraid that I sitll failed to communicate my question.
The horn will comprise an inner "kernel" and an outer "shell".
For the "shell" I was condidering either fibreglass/kevlar or veneer (built to about 0.125 inches on each surface - inner and outer of the "kernel").
My question is what material and thickness would be best for the "kernel".
M
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