compression driver impedance question

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ICG

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Done
here my blog about it
Audio by Martin

will have to listen to them, just measured so far.
Been busy this weekend.

Thank you. :)

Audio by Martin Blog said:
the spl gain of the waveguide at 3khz is about 9db!!!

the gain is still about ~3db at 10khz

loading fall like a rock after ~14khz and EQ must be used to compensate.

That pretty much matches the suspected behaviour of the combination. I also expect them to not play relaxed enough to fit sound wise to the horn mids which got so much more headroom. At which spl/power are the distortion measurements?

Received the Celestion CDX1-1445 and the Faital STH100 horn.

here some quick line about them.
Audio by Martin

I really need to burn them in (and the new amp driving them too)

right now, it is very promising at ~4khz crossover point.

way better than my heavy magnesium dome tweeter.

Glad you like it. :) I've read your blog entries (I feel flattered you've mentioned me :eek: :D) and I have to say, the STH100s look amazing in white. For the setup, you have to do some fiddling, not only the frequency response is important, it has to be a good phase match too (and ideally impulse response aswell). The problem is that the sound sources (the drivers) got a depth offset to each other. To compensate for that, you'll have to increase the delay of the channel. For a good matching phase you measure the phase and at the crossover point it should ofcourse show a good addition, to check if the phase/addition works, switch the polarity of the tweeter. That should show a very deep V-notch in the frequency response. If it does not, the phase is off and you have to adjust the delay.

That works the same way for the other speakers/ways but you have to keep in mind, if you've set up one phase alignment and want to adjust the next one, you have to 'move' the already set and matching ways by the same offset.

To give the two 15" independent DSP channels only makes sense if you want to use one in the bass alone and the other to play up to the midrange. The delay of one over the other to 'emulate' the tilt is not suggested, especally if they work into the same enclosure volume (from the photos and what's visible from the construction I expect them to have separate volumes though).
 
Lynn Olson was using the Azura but doesn't anymore. I think you'll find his comments in the JMMCL thread.

Lynn commissioned the Azura AH-425. Bjorn Kolbrek provided the specific application of the LeCleac'h profile, sized to mate with the Altec 288 and provide a nominal cutoff frequency of 425 Hz. It was conceived as a component of the hypothetical ("thought experiment") speakers discussed in the "Beyond the Ariel" thread.

Somewhere along the way, Lynn's friend in another state created a prototype (Lynn doesn't do the actual construction of his designs). Lynn traveled to hear them and was pleased with the horn (by this time, the driver was a Radian 745Neo), but didn't consider the total system to be a finished design. The prototypes were disassembled and the thought experiments continued. Meanwhile, Lynn continues to listen to his Ariels at home while the parts from the prototype sit in his basement.

Meanwhile, I built a full implementation...my own take on the "Beyond the Ariel" concept. I actually have two pairs of Azura AH-425's, one with Radian 745NeoBe drivers and another with Yamaha JA-6681B's. I have developed a preference for the Yammies, but since their diaphragms are unobtainium I have great interest in finding a modern alternative. Lynn hasn't heard my speakers yet, but hopes to make the trip this summer.

Several of our friends have built their own speakers inspired by the Beyond the Ariel thread, often with Azura horn.

In any event, Lynn hasn't abandoned the AH-425's. He simply hasn't yet reached the point of having them playing music in his home yet. I hope that changes soon!
 
g3dahl said:
SNIP<>Meanwhile, I built a full implementation...my own take on the "Beyond the Ariel" concept. I actually have two pairs of Azura AH-425's, one with Radian 745NeoBe drivers and another with Yamaha JA-6681B's. I have developed a preference for the Yammies, but since their diaphragms are unobtainium I have great interest in finding a modern alternative. Lynn hasn't heard my speakers yet, but hopes to make the trip this summer.<>SNIP

That's really interesting Gary!

I wonder about the reasons for your preference.

I think you might be the first user of any Be-diaphragmed compression driver to articulate a rethink.

Are you able to expand any on why ? ( since the Alu dome is now somewhat off the table as to the determining factor ).

:)
 
I started with aluminum diaphragms - first, the Altec/GPA 288's and then the standard Radian 745's. Both sounded unacceptable with strings. Slow sweeps with a signal generator and scope revealed huge narrowband resonances, clearly the result of breakup modes. The magnitude was much lower with the Radians, so I used them for some time while awaiting the availability of beryllium diaphragms.

Beryllium certainly has advantages as a diaphragm material, but other factors seem to come into play as well - surround, phase plug, etc. The Radian 745Neo becomes less flat when equipped with a beryllium diaphragm. I did as much as I could to tame its response in the crossover. Strings ended up sounding quite good, but there was still an element of hardness that had been present in every implementation of a compression driver that I had ever heard up to that point.

The JE-6681B drivers on the AH-425 horns are impressively flat with no equalization at all. They are slightly less clean than the Radian berylliums, but they sound superb with strings and woodwinds (and everything else), even with their aluminum diaphragms...go figure. They are also a bit soft in the highs, but I have not yet found a supertweeter implementation that extends the top end without other sonic penalties, at least in my listening room.
 
long to reply here...

That pretty much matches the suspected behaviour of the combination. I also expect them to not play relaxed enough to fit sound wise to the horn mids which got so much more headroom. At which spl/power are the distortion measurements?
Was at 90db 1 meter
Did the same waveguide for the beryllium tweeter with very similar result.

on my 2nd system (direct radiator cone midrange), it improved things very much subjectively. (maybe better dispersion and less room interaction)
Yet to try it with the JMLC horn.

I do agree that they may not get the same sound as CD but those beryllium 28mm tweeter do extension and decays so good, hard to live without...
The 26mm Ceramic version has more attack but lack refinement.
the 26mm Magnesium lack attack and decays, it's a inferior product for sure.

The angled dual 15" seemed to work. (yes, they are separate air volume inside). Just need to install plywood in front to hide those foam filled BR port...
when playing "pink noise" with microphone at listening position, it was obvious that it created a high Q notch.
variation of the angle to an "optimal angle" lessen significantly the notch
It was 310hz or about from memory.
I just let it at an angle since...

Will have to try both woofer sideway but right now, it isn't working cause the door won't open...
CTC spacing of woofer is a bit bigger that I would like but it's a recycled box and hole were already made...

I do use time delay and adjust phase.
I do it "fullrange" first but once I put EQ and crossover, I always have to recalibrate delays as they usually shift few mS...
very hard to be perfect, change EQ, delays have to shift...

Gary,

Very interesting read about the "beyond the ariel" and Yamaha CD.
Rare that somebody do not prefer Ber driver as well!
I'm eying some TAD4001 4" CD right now.

If the 1" tractrix is the best option, I'll likely buy the B&C DCM50 as it will play lower and I'll cross at ~4khz.
FR seem quite bad though...


Pillover,

thanks for link, will put this supplier on my list :)
 
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