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Old 31st March 2008, 06:43 PM   #3251
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Location: Northern Colorado
I've been in communication with Martin Seddon, and can confirm that the rumor Azurahorns are going out of production is NOT true. He is continuing current production of the Azurahorn series. However, one setback has been Australian post no longer ships the AH-340 and the larger horns, requiring FedEx or UPS instead.

When I called FedEx and UPS, the price for shipping a pair of boxed AH-340's from Perth, Australia to Denver, USA was $550USD (FedEx) and $450USD (UPS). Australia post still can ship a pair of AH-550's from there to here at the much more moderate price of about $100USD.

Music Concrete in France has horns with similar profiles, made of concrete composite of course, at about twice the price (shipping included) as the Azurahorns. (The depressed USD/Euro ratio doesn't help here.) The quotes I've gotten from US-made wood horns are well above the Music Concrete price. A big attraction of the Azurahorn is the price is low enough to fall into what I consider the "experimental" range to play with different sizes and compression drivers. Not interested in small-format compression drivers, and don't need their HF extension since I already own supertweeters with complementary high efficiency, very low energy storage, and extension to 100 kHz.

Aside from shipping costs, I'm still going back and forth on the AH-340 vs the AH-550. The AH-340 (24" horn mouth diameter) is almost exactly twice as big as the AH-550 (12" diameter). The book by Newell and Dr. Holland recommends low-diffraction (no kinks in the acoustic path) horns with less than 12" of total length from diaphragm to horn-mouth. The authors point out that horns of this size and profile almost exactly mimic the 12" and 15" Tannoy Dual Concentrics, minus the weird modulation effects of the moving bass diaphragm.

This recommendation points towards the seven-inch-long AH-550, while the AH-340 offers the attractive option of a lower crossover and possibly lower distortion in the 1 kHz region. Essentially, a tradeoff between a 1:2 difference in energy storage (smaller horn, shorter delays, Tannoy dimensions) vs somewhat higher IM distortion from decreased diaphragm loading.
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Old 31st March 2008, 07:22 PM   #3252
CV is offline CV
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Default The arachnophobic approach to driver design

Lynn,
I think you've already decided on drivers, but one interesting thing to note is that the Be diaphragmed JBL 2435HPL has an internal flare rate of 550 Hz and the phase plug exits right at the throat. Perfect match for the 1.5" AZ-550.

A pal and I actually commissioned the above horn from Martin for Vitavox S2, which is also 1.5", but he may be able to supply an adaptor for it to take it down to 1.4" smoothly for the Altecs. I imagine most off the shelf adaptors to be hopelessly imprecise in terms of exact fit/transition.

We also sponsored the 160s... these are impressive looking beasts which should better match the flare rate of a whole generation of older drivers. Can't wait to try them out with the S2 and RCA field coils.

Look at the response plot of the Yamaha JA6681B on the 160Hz horn that's posted on Martin's site for example; never seen anything like it...

Incidentally, that driver has a wonderfully engineered surround formed of beryllium copper fingers which should hugely reduce diaphragm resonance - take a look.

I suspect the main advantage of compression drivers over cones is the omission of the spider; the Yam driver takes it further and removes much of the path for reflection of energy back into the diaphragm at the termination. The Fertin model 7 has similar design features; complex shaped carbon fiber spider (minimal hysteresis??) and a suspension of 3 thin carbon rods - see the fullrange forum for detail on this driver.

Anyway, enough rambling. Good luck and look forward to hearing your updates, as ever.

Best wishes,
Chris
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Old 31st March 2008, 09:02 PM   #3253
Anglo is offline Anglo  Canada
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Default Lynn, where have you been!

...incredible thread!

I really love the way the thread flows and the amount of positive input the members have put in.

For the last 3 years, I have felt alone on an island with my open baffles and a 15" wideband 'till seeing this thread!!

Now, I will post pics soon of the system and my room but here goes by writing.

It is a 3 way open baffle on 3/4 inch russian birchply. I, like what I understood what from Lynn, like very much a 15" wideband driver for the weight it gives to instruments. Some will find this to be exagerated sound, but I find smaller drivers to be anemic. The wideband driver is an EV SP15A that has a 103db efficiency at 1Khz. I have added a fountek ribbon tweeter, the cd pro5i, that has an efficiency rating of 102 db. This is cutoff and I time phased it with the voice coil of the EV, with a mundorf cap of 3.3 mfd. This cuts it off at 5.6 Khz, well out of the critical spot. For bass, I have an Altec 515B on the open baffle and controlled by an active over. I reversed the phase of the Altec from the EV and adjusted the phase of the xover to 90 degrees. The active xover is a 3rd order xover, so I have a phase shift of 360 with the reverse phase and an 18 db slope. Also, it is time aligned with the voice coil of the EV.

The system is triamped, an amp for each driver.

Coherence was and is an important issue for me along with tone, effortless dynamics, agility, feel, textures and harmonic precision.

My shpeal on coherence is that a fullrange driver, such as a Lowther in a properly implimented system is the ultimate in coherence along with Acoustats. However, they are limited in FR and other things. I realise that as long as I am patching sound together again, I will never achieve the absolute coherence of such a driver. After listening to the Lowther in a highly optimised Big Fun Horn, I went back to my place in fear of finding a messy blob of sound. To my surprise, I was impressed that it didn't embarass my 3 way, and that the level of resolution was far superior to that of the Lowther DX4. I also, have better, IMO, development of the notes i.e harmonics.

My room, is 13 * 19 and is covered in russian birchply 1/2 inch. Velvet curtains on both ends, 1st 3 reflections aborbed and some absorption ever 2 feet.

I ask, since this Lynn's thread is basically based on the exact system I have except for the precise drivers mentioned, how you would first approch tuning this system for the better. Aspects such as energy storage, EnABL and diffraction methods amongst other ideas.

Tuning these beasts has been a lonely place for me, until seeing this thread, all inputs are more than welcomed. I have always wanted knowledgeable open baffle enthousiast help me improve my system.

Hopefully someone will respond to this post and I hope this post goes with the wonderful flow of this thread and not a thread fart. If it isn't right, I can repost it elsewhere.

Thanks,

Steve
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Old 31st March 2008, 09:57 PM   #3254
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Despite my woo-woo reputation, I mostly use instrumentation during the first part of a loudspeaker project, and listen to pink-noise, not music. I use MLSSA (or any other MLS system) and tune and/or modify the individual drivers for most rapid settling time (less than 1 mSec if possible), and then impulse-align the whole system after I am reasonably satisfied that the individual drivers are close to optimum performance.

Subjective fine-tuning happens after I am reasonably satisfied with the time and frequency domains, and is in small degrees, typically 1/2 dB trims between the drivers, as well as rolloff-slope optimization (which alters the polar pattern at crossover frequencies).
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Old 31st March 2008, 11:09 PM   #3255
Anglo is offline Anglo  Canada
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Hi Lynn

Don't know if your last response was directed at me, but if it was I guess you are implying that without measurements you don't see anything to point to to "fine tune" my system.

I can get my measurements redone by my buddies with measuring devices...

How can I measure such a thing as diffraction?

Cheers

Steve
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Old 1st April 2008, 01:27 AM   #3256
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I'd go with the smaller horn - the big one will beam and get in trouble on top, the ribbon won't mate well with it either. The smaller horns sound better with a compression driver

PS - have a real odd ball pair compression drivers here that's making me grin = some old cerwin vega phenolic 4" with 2" exit - really smooth and wonderful with strings - crossing in 500 with 12" tractrix, dies after 3 k but ohhhh the mids are dreamy
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Old 1st April 2008, 08:55 AM   #3257
Jmmlc is offline Jmmlc  France
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Hello Lynn,

IMHO there is nearly no more diffraction with the Azura 340Hz horn than with the Azura 550Hz. A FEM simulation using hornresp will demonstrate it. (Also the mesured impedance curve is very smooth compared to the same driver on other horns, this is due to low difraction and refelected waves from the mouth to the throat).

For my own there is another reason why I prefer the larger horn it is because it's reactance is quasi null above 700Hz when the reactance of the 550 will still be non negligeible at 1000Hz.

Then about the increased directivity, that's a very personnal taste...

Best regards from Paris,

Jean-Michel Le Cléac'h


Quote:
Originally posted by Lynn Olson

Aside from shipping costs, I'm still going back and forth on the AH-340 vs the AH-550. The AH-340 (24" horn mouth diameter) is almost exactly twice as big as the AH-550 (12" diameter). The book by Newell and Dr. Holland recommends low-diffraction (no kinks in the acoustic path) horns with less than 12" of total length from diaphragm to horn-mouth. The authors point out that horns of this size and profile almost exactly mimic the 12" and 15" Tannoy Dual Concentrics, minus the weird modulation effects of the moving bass diaphragm.

This recommendation points towards the seven-inch-long AH-550, while the AH-340 offers the attractive option of a lower crossover and possibly lower distortion in the 1 kHz region. Essentially, a tradeoff between a 1:2 difference in energy storage (smaller horn, shorter delays, Tannoy dimensions) vs somewhat higher IM distortion from decreased diaphragm loading.
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Old 1st April 2008, 01:30 PM   #3258
ion is offline ion  Sweden
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Quote:
Originally posted by Jmmlc
Hello Lynn,

IMHO there is nearly no more diffraction with the Azura 340Hz horn than with the Azura 550Hz. A FEM simulation using hornresp will demonstrate it.
Now, hornresp doesnt use Finite Element Methods does it?
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Old 1st April 2008, 01:53 PM   #3259
Jmmlc is offline Jmmlc  France
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Hello,

A recent feature of Hornresp is the simulation of the wavefronts.

This is in:
[Tools]
[wavefront simulator]

I guess the calculation is done like in a wavetank simulator by Finite Elements Method...

But I may be wrong.

That wavefront simulator is a quite powerful tool to see the effect of the reflected waves from mouth to throat (but you need to wait something like one minute for the wavefield to stabilize).


Best regards from Paris, France

Jean-Michel Le Cléac'h


Quote:
Originally posted by ion


Now, hornresp doesnt use Finite Element Methods does it?
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Old 1st April 2008, 03:23 PM   #3260
ion is offline ion  Sweden
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Jmmlc, Ok, my hornresp may be a bit out of date. In that case I stand corrected. Time for an upgrade then
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