What about interchangeable phase plug idea? I'm planning produce such based on STX D-800-Ti driver. Here's a simplified 3 parts sketch of concentrator with Fresnel phase plug (circular) and OS type throat that could be replaced with conical or cylindrical. Simulations shows merging OS with JMLC mouth to be a good idea.
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IMO the exit angle as well as the phase plug itself already must be seen as part of the horn contour – this is a simple requirement of the diffraction alignment concept.
Comparing an AMT and a compression driver in this respect - it immediately gets obvious, that the part between compression driver diaphragm and phase plug is equivalent to the pleating of the AMT diaphragm
The phase plug of a compression driver does nothing else than bridging the radial distance of that "compression driver pleats" towards a single opening – luckily, such a phase plug is not needed for an AMT on horn.
just my 2ct
Michael
Comparing an AMT and a compression driver in this respect - it immediately gets obvious, that the part between compression driver diaphragm and phase plug is equivalent to the pleating of the AMT diaphragm
The phase plug of a compression driver does nothing else than bridging the radial distance of that "compression driver pleats" towards a single opening – luckily, such a phase plug is not needed for an AMT on horn.
just my 2ct
Michael
I like the way MyEmia works around this problem with their matched horn / driver combo.
The 600hz field coil compression driver uses a LeCleac'h expansion, and has a 6" length from the phase plug with the first 4" of the expansion machined into the driver.
The remaining 2" consists of a wood horn with full rollback.
So the only possible misalignment would be 4" out; and much easier to detect and correct.
(above info mostly copied from MyEmia and hifi heroin blog. )
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Price and availability?
Where can I buy them and how much?BTW
this is my latest:
beautiful Mundorf AMT 2510c.
Seems - on request - they are available as "nude" for dipole horns as well (with considerable cost saving due to missing front plate)
Michael
got mine directly form Mundorf / Holographic Sound Device
Price was a fair EUR 300.- for the pair (excluding VAT) - but I'm not sure if thats been a "special teaser price" for the early bird, so be prepared for possibly some more...
Also, do not expect any comfort or fancy extras for that lowish price - it comes in simple bubble wrap only - very good packed though.
Included is a piece of felt for back dampening of each driver.
There's a fine black mesh that covers the slits and there are the thin wires you see for connection that cant be removed - thats it.
Michael
Price was a fair EUR 300.- for the pair (excluding VAT) - but I'm not sure if thats been a "special teaser price" for the early bird, so be prepared for possibly some more...
Also, do not expect any comfort or fancy extras for that lowish price - it comes in simple bubble wrap only - very good packed though.
Included is a piece of felt for back dampening of each driver.
There's a fine black mesh that covers the slits and there are the thin wires you see for connection that cant be removed - thats it.
Michael
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Replacement part
Is that offered as a replacement part for the normal configuration? Does it have a part number?got mine directly form Mundorf / Holographic Sound Device
Price was a fair EUR 300.- for the pair (excluding VAT) - but I'm not sure if thats been a "special teaser price" for the early bird, so be prepared for possibly some more...
Also, do not expect any comfort or fancy extras for that lowish price - it comes in simple bubble wrap only - very good packed though.
Included is a piece of felt for back dampening of each driver.
There's a fine black mesh that covers the slits and there are the thin wires you see for connection that cant be removed - thats it.
Michael
Yes, it's a solid piece of gear and the distortion plots I've seen published are heaven.
But I don't think this AMT is worth a own thread - only a handful of diyers that are interested in modern AMT and even less that use it actually.
Will be back in the "beautiful swingin' speaker" thread as soon as I got around a dipole horn for this one - which may take quite a while - as I very much would like to check out quarter wave honk by wavelet measurement for the cylinder wave contour I usually do for AMT drivers first.
Michael
Poor measurements of the 425
Why do these CSD of the 425/ Altec look so dirty?
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Azura 425hz horn (drivervault)
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Is it the driver? The measurement location? I would be very disappointed to spend so much on a horn to end up with hashy curves like that.
Why do these CSD of the 425/ Altec look so dirty?
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Azura 425hz horn (drivervault)
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Is it the driver? The measurement location? I would be very disappointed to spend so much on a horn to end up with hashy curves like that.
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Hello Sendler,
As you can see by the frequency response curves taken at different angles from axis, there is a very smooth variation of the shape of one curve to the other.
The main point is that there is NO off axis attenuation of the little peaks and holes in the curve (if the horn reduces by 20dB the mean level around a given frequency off axis you should have also some decreasing of the amplitude of the artifacts). So we can interpret this, as the artifcats are due to the driver itself.
Imagine you linearize the on axis curve, then you'll obtain very smooth off axis responses and this is because the Le Cléac'h horn itself has very little reflections (from mouth to throat or other sources of reflections). Many on axis response curves of different Le Cléac'h horns have been published and most of them are the smoothest you can find.
Remember also the Driver Vault's remark:
"The compression driver is a GPA/Altec 288-16H. I would have liked to test it with the standard DE250, but I didn't have an adaptor."
Now, you may find in the following discussion the wavelet graph obtained by Alias on a Le Cléac'h horns (Fc = 320Hz) using a TAD TD2001 compression driver.
http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted-27.html#post2120819
and then compare it to to many others horns
http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted-30.html#post2122769
and finally please, read Elias's conclusion:
"Also the Le Cléac'h J321 has -25 dB reflections, but of course they are less in numbers compared to others! Maybe it's the total amount that counts? The human perception contains an integrator."
Lynn Olson possess now many different measurements made with the AH425 loading many different 288 and also some JBL drivers. I hope some day in the near future they will be shown on the thread "beyond the Ariel".
http://www.diyaudio.com/forums/multi-way/100392-beyond-ariel-656.html#post2034289
The results obtain with the Altecs are very different from one 288 to the other and there is actually some discussion with GPA to try to identify the source of the problem.
Best regards from Paris, France
Jean-Michel Le Cléac'h
As you can see by the frequency response curves taken at different angles from axis, there is a very smooth variation of the shape of one curve to the other.
The main point is that there is NO off axis attenuation of the little peaks and holes in the curve (if the horn reduces by 20dB the mean level around a given frequency off axis you should have also some decreasing of the amplitude of the artifacts). So we can interpret this, as the artifcats are due to the driver itself.
Imagine you linearize the on axis curve, then you'll obtain very smooth off axis responses and this is because the Le Cléac'h horn itself has very little reflections (from mouth to throat or other sources of reflections). Many on axis response curves of different Le Cléac'h horns have been published and most of them are the smoothest you can find.
Remember also the Driver Vault's remark:
"The compression driver is a GPA/Altec 288-16H. I would have liked to test it with the standard DE250, but I didn't have an adaptor."
Now, you may find in the following discussion the wavelet graph obtained by Alias on a Le Cléac'h horns (Fc = 320Hz) using a TAD TD2001 compression driver.
http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted-27.html#post2120819
and then compare it to to many others horns
http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted-30.html#post2122769
and finally please, read Elias's conclusion:
"Also the Le Cléac'h J321 has -25 dB reflections, but of course they are less in numbers compared to others! Maybe it's the total amount that counts? The human perception contains an integrator."
Lynn Olson possess now many different measurements made with the AH425 loading many different 288 and also some JBL drivers. I hope some day in the near future they will be shown on the thread "beyond the Ariel".
http://www.diyaudio.com/forums/multi-way/100392-beyond-ariel-656.html#post2034289
The results obtain with the Altecs are very different from one 288 to the other and there is actually some discussion with GPA to try to identify the source of the problem.
Best regards from Paris, France
Jean-Michel Le Cléac'h
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Yes indeed. I was speaking with a friend of Lynn's just the other day and he told me the same thing. Probably from the same set of tests. Looks like there is a problem to be fixed.
I don't know what your listening impression is, but there will be some harsh sound caused by the what probably is the diaphragm breakup mode righ before high end roll off.
You will also sense some loss of image focus in the mid range.
My friend Gary Dahl has completed a series of tests on the AH-425 Azurahorn and 3 different GPA 288's and two different Radian 745P's. They were measured at 24" from the horn mouth, which might account for the noticeable variations from Augerpro's measurements.
I need to ask Gary's permission before posting them in this forum, but I can tell you they are very flat - in fact, they look like plane-wave tube measurements, instead of a horn. Based on what I've seen, there is no need for notch or shelf filtering with the audio band, which should greatly simplify the crossover.
There is no on-axis hole, and the family of off-axis responses are all tightly correlated with the on-axis measurement. In terms of dispersion, the 16.5" Le Cleac'h horn resembles an idealized 4" direct radiator, with no sharp cutoff at the edge of the nominal 90-degree beam, and no discontinuities within the beam. As mentioned in other forums, this is not a "constant-directivity" horn in the usually accepted meaning of the term, but it does have very smooth dispersion characteristics, with a "soft" edge, unlike SR or movie-theater horns.
The agreement between Bjorn Kolbrek's BEM simulations (which were used to design the AH-425) and the measurements of the physical driver and horn are as close as I've seen for any horn system. I'm very pleased with the way the AH-425 project has turned out, and would like to thank Jean-Michel Le Cléac'h, Bjorn Kolbrek, Martin Seddon, and Gary Dahl for all of their insight, proposals, designs, and hard work.
I need to ask Gary's permission before posting them in this forum, but I can tell you they are very flat - in fact, they look like plane-wave tube measurements, instead of a horn. Based on what I've seen, there is no need for notch or shelf filtering with the audio band, which should greatly simplify the crossover.
There is no on-axis hole, and the family of off-axis responses are all tightly correlated with the on-axis measurement. In terms of dispersion, the 16.5" Le Cleac'h horn resembles an idealized 4" direct radiator, with no sharp cutoff at the edge of the nominal 90-degree beam, and no discontinuities within the beam. As mentioned in other forums, this is not a "constant-directivity" horn in the usually accepted meaning of the term, but it does have very smooth dispersion characteristics, with a "soft" edge, unlike SR or movie-theater horns.
The agreement between Bjorn Kolbrek's BEM simulations (which were used to design the AH-425) and the measurements of the physical driver and horn are as close as I've seen for any horn system. I'm very pleased with the way the AH-425 project has turned out, and would like to thank Jean-Michel Le Cléac'h, Bjorn Kolbrek, Martin Seddon, and Gary Dahl for all of their insight, proposals, designs, and hard work.
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I think it would be interesting to see the difference. Please also indicate the type of signal used for the measurements in case you do post them. While close measurements like that are good for finding certain problems, I would think a distance to mouth diameter ratio of 5 or more would resemble response closer to listening situations.
No, never. I mostly listen to all kinds of jazz and instrumental classical.
Here are measurements of 288 in lecleach horn; on axis at 1m no smoothing, with (passive) equalization, with eq at 30-degree.
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Here is something to give you a quick idea of what we have seen so far -- one of Lynn's Radian 745PB-8 drivers on an Azurahorn AH-425. The response of both of his drivers look very closely matched, with most of the wrinkles in the same spots except above 10 kHz. I ran curves using both MLS and swept sine signals, and saw very little difference.
My expertise is music, not measurement science. I have been learning what I can as a hobbyist, and have been fascinated by the capabilities of ARTA but have much to learn about its proper use.
Measurements from greater distances will likely have to wait until summer, sorry!
My original hope was that the Azurahorn would work without a tweeter, but I have given up on that. My current plan is to run the horns from about 1 kHz to 8 kHz, with B&C D35's above and TD15M's below.
Gary Dahl
My expertise is music, not measurement science. I have been learning what I can as a hobbyist, and have been fascinated by the capabilities of ARTA but have much to learn about its proper use.
Measurements from greater distances will likely have to wait until summer, sorry!
My original hope was that the Azurahorn would work without a tweeter, but I have given up on that. My current plan is to run the horns from about 1 kHz to 8 kHz, with B&C D35's above and TD15M's below.
Gary Dahl
