Beyond the Ariel

[john k...]

What I have presented is pretty much the standard stuff in acoustic texts and is correct. The only argument is whether the sound pressure actually behaves as indicated, doubling when the acoustic space is reduced by 1/2. That is reasonably correct for a reduction in space form 4Pi to 2Pi. As we know we see a 6dB increase in SPL above the baffle step. That the efficiency increases is also a direct consequence of the doubling of the pressure. It's a well know result.

The problem is that this relationship of doubling the pressure each time you cur the space in 1/2 doesn't apply at infinitum. As an example, consider the usual equation for efficiency of a driver. It states that efficiency is proportional to Sd^2, increasing by 6dB each time Sd is doubled. So if we start with a driver with 1% efficiency doubling Sd 7 times would yield an efficiency of 128%. Obviously this can't happen.

The problem is that the assumptions in these relationships break down. So when we start to get to extremes we need to go back and look at the problem differently.

[john k...]

Originally posted by KCHANG


Let's go back to more popular topics, such as which drivers should be used.

Cheers,

Kurt

Now there's a topic that keep running in circles.

[mige0]

Hi

Originally posted by john k...


Now there's a topic that keep running in circles.

Its like dancing the waltz, isn't it ?




JohnK thanks for the IM plot at post #2895

http://www.diyaudio.com/forums/showt...55#post1378055

Its also useful for tweeters – do you have a excel calculation sheet for this as well ?

When calculating for the Seas Excel Millenium for example, the X=1cm @ 50Hz would translate to X=0,5mm @ 1000Hz which is well within the "linear" range of that tweeter giving roughly 100dB in SPL with its 7cm2 of Sd.
Not an unusual value at normal listening levels.

At ~ 8KHz - a range of 3 octaves up – we would get an IM of around -40dB ( = 1%), correct?


Greetings
Michael

[john k...]

Originally posted by mige0
Hi






Its like dancing the waltz, isn't it ?




JohnK thanks for the IM plot at post #2895

http://www.diyaudio.com/forums/showt...55#post1378055


When calculating for the Seas Excel Millenium for example, the X=1cm @ 50Hz would translate to X=0,5mm @ 1000Hz which is well within the "linear" range of that tweeter giving roughly 100dB in SPL with its 7cm2 of Sd.
Not an unusual value at normal listening levels.

At ~ 8KHz - a range of 3 octaves up – we would get an IM of around -40dB ( = 1%), correct?


Greetings
Michael

You are correct for the excursion, but the frequency ratio would be 8k/1k = 8. At a frequency ratio of 8 the IM would be about -28dB, or closer to 4%. Of course, this assumes pistonic behavior. Also it should be noted that Xmax is just a physical value; (voice coil length - gap height)/2. It has very little to do with whether the driver is linear or not at that excursion.

[angeloitacare]

hi Lynn

your system might lead in this direction :

http://www.audioasylum.com/forums/hu...12/129890.html

[Lynn Olson]

Yes, I noticed that that post too. What I'm most interested in is a LeCleac'h profile horn/waveguide for the two contemplated midranges: 1.4" compression driver, and 6" studio-monitor cone driver. Since I'm not using a basshorn with its intrinsically limited bandwidth, I have the luxury of a considerably smaller mid horn crossing over anywhere from 600~800 Hz.

I really, truly, dislike horn coloration, and cannot ignore it, no matter how hard I try. Karna dislikes it even more, if that was possible - she doesn't even consider any system with that type of coloration to be musical. I can listen around the coloration for a while, admiring the other virtues of the system, but it spoils the long-term listening pleasure.

The reason I'm still considering a horn/waveguide midrange is there are several studies that claim that horn/waveguides with modern profile designs that are axisymmetric and are also 1 foot or shorter in length have no audible horn coloration. So they say. AES studies claim a lot of things that don't agree with my perceptions at all, so this claim may be true, or it might not. Dunno.

The other reason I'm considering a horn/waveguide is my experience with multiple direct-radiator drivers is there is a price to be paid in coherency, particularly in the midrange. Multiple drivers seem to work fine in the bass, where wavelengths are large anyway, but they fall down badly in the midrange, with a phasey, diffuse sound that lacks impact. I spent a lot of time on the Ariel improving the coherency of the sound, and it's a hassle I don't want to do again, especially with a 3-way system, which have much more serious problems with overall coherency.

The AudioKinesis system I heard at the RMAF had very low horn coloration - I don't know if I'd say it was zero or not. The Emerald Physiks had more than I can accept and I found the HF reproduction harsh and raw-sounding, with lots of driver breakup. I've heard Avante-Garde Duos and Trios at many different shows and in several different homes and consider them to have very strong horn coloration (JBL class) and quite mediocre-sounding drivers as well - the cone breakup of the mid driver was quite obvious, and the system cried out for a decent pro midrange. The AG's would sound much better if the mid and HF drivers were better-quality - less breakup, smoother out-of-band response, all the usual desirable things.

In terms of low horn coloration, the AudioKinesis is the lowest I've heard so far - and it had a reasonably small waveguide and a very good compression driver. The superb 10" TAD Alnico midbass certainly didn't hurt, either. My suspicion is the higher the efficiency, the better the drivers have to be - the colorations that remain are more audible than murky-sounding low-efficiency drivers.

My sensitivity to horn coloration is much higher than most audiophiles from what I can tell, so I'm guessing the majority of the readers of this forum would be happy with a high-quality horn mid and horn HF unit.

I like what horns do well - effortless dynamics and vivid tone colors - so I'm looking for folks that could build a LeCleac'h profile waveguide for the 1.4" midrange compression driver and the prosound midrange cone driver. By keeping the dimensions compact, restricting the bandwidth of the mid horn, and choosing a wide-dispersion low-diffraction profile (and I can measure this, not guess), I'm hoping the coloration falls below subjective audibility. I'm keeping my fingers crossed on this one, and hedging my bets with a quartet of direct-radiator mids.

P.S. When I mentioned 120 dB SPL headroom many posts ago, I wasn't referring to the entire frequency band. 120 dB at 30~55 Hz requires a mammoth basshorn or a wall-sized infinite-baffle array, and that's way beyond my goal. "Conventional" soffit-mounted studio-monitor dynamics will be plenty good enough.

[Brett]

Originally posted by Lynn Olson
Yes, I noticed that that post too. What I'm most interested in is a LeCleac'h profile horn/waveguide for the two contemplated midranges: 1.4" compression driver, and 6" studio-monitor cone driver. Since I'm not using a basshorn with its intrinsically limited bandwidth, I have the luxury of a considerably smaller mid horn crossing over anywhere from 600~800 Hz.

{snip}

I like what horns do well - effortless dynamics and vivid tone colors - so I'm looking for folks that could build a LeCleac'h profile waveguide for the 1.4" midrange compression driver and the prosound midrange cone driver. By keeping the dimensions compact, restricting the bandwidth of the mid horn, and choosing a wide-dispersion low-diffraction profile (and I can measure this, not guess), I'm hoping the coloration falls below subjective audibility. I'm keeping my fingers crossed on this one, and hedging my bets with a quartet of direct-radiator mids.

Lynn have you contemplated the Azura horns?
http://www.azurahorn.com/

Also wondered if you'd seen these.
http://audioheritage.org/vbulletin/s...ad.php?t=12126
http://audioheritage.org/vbulletin/s...ad.php?t=12967

[Tom Danley]

Hi Lynn, John, All

“I really, truly, dislike horn coloration, and cannot ignore it, no matter how hard I try. Karna dislikes it even more, if that was possible - she doesn't even consider any system with that type of coloration to be musical. I can listen around the coloration for a while, admiring the other virtues of the system, but it spoils the long-term listening pleasure.”

Lynn I understand, some of the most hideous sounding speakers I ever heard were horn loaded.
On the other hand “horn coloration” is not something, which necessarily always goes with horns.
I would urge you to look into Bill Woods conical shape horns, conical horns can be essentially a spherical section in their radiation if driven by a point source (an origin too small to have its own directivity).
Also, not all drivers are equal obviously and if you look at most phase plug designs, one sees that many produce a converging wave at the summation point, while to drive a horn, it should be a diverging wave front.
Drivers like the BMS 4550 (for one) and some 18Sound drivers have a structure which produces a compatible diverging wave front at the driver exit.
Earl’s HOM’s are produced when the dimensions are such that there is directivity, while the sound is also required to change direction.
Loading a conical horn, even a huge one (who’s angle is constant) with a proper wavefront or small source, doesn’t have these issues.
On the other hand, larger exponential, Tractrix and other curved wall horns (except for Earl’s which has the slowest change possible) automatically produce some of these effects as the radiation angle narrows with frequency, no matter what driver is used.

Since your obviously in the mood to get something going (and hopefully your leg is better etc) I would suggest an experiment.
Get a bms 4550 driver (it’s a good one) and make a conical horn, no more than say 60 degrees angle, about 12 to 18 inches across and if your liking the sawdust, make the outer 1/3 of the horn, radius into an angle about 1.4 times greater than the main wall angle.
This nulls the narrowing in the pattern that normally happens as one approaches the pattern loss frequency (at the low end of the response)

Unlike most direct radiators, this will not produce flat response yet.
Measure the horn and derive and apply the eq needed to flatten it out.
Do this electronically first as making a passive electrical filter that does this AND accommodates the drivers impedance curve is more difficult.
EQ here is ok as what your fixing is then fixed in magnitude and phase.
This driver will be happy with a high pass filter above say 500Hz in the home, use at least a 2nd order filter.
Mate this to a lower range system and give it a listen.
Handling the upper half of the range, flattened out, your ear should not recognize it as a horn.

Kchang (is that amazing little full range driver demo I heard once Kurt?), John, there is an upper limit to mutual coupling which seems to reach an asymptotic point around 25-30% efficiency, while a large speaker array may appear to be higher than this due to forward directivity.

I wish I had some experience with these open baffle bass speakers but to be honest I haven’t ever played with them and for some time I have been focusing on horns and horn drivers.
I would guess the ideal driver for that is pretty different than those for sealed or vented boxes though. The difference would be that less motor strength is needed, as one would want a Qt that is greater than one I would think.
If you can model the “ideal driver”, which I assume John and others can, you might be able to interest Eminence in making a purpose built driver for it. Jerry built up a driver for a DIY project I did some years back so it isn’t unheard of anyway.
Best,

Tom Danley

[pdan]

Tom,

I don't think a conical is esoteric enough for Lynn.


"........ make the outer 1/3 of the horn,radius into an angle about 1.4 times greater than the main angle wall', I picture this to mean a double conical horn; is this correct?


Cilla

[Paul W]

Drivers like the BMS 4550 (for one) and some 18Sound drivers have a structure which produces a compatible diverging wave front at the driver exit.

Tom,
Which 18Sound drivers are you referring to?
Thanks,
Paul