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-   -   Beyond the Ariel (http://www.diyaudio.com/forums/multi-way/100392-beyond-ariel.html)

Lynn Olson 27th March 2007 08:30 PM

Beyond the Ariel
 
This forum is as a good a place as any for thinking out loud about the successor to the Ariel and ME2's. Since my fall in the terrible Colorado snowstorms of January, I've been recovering, and probably won't be doing any serious audio design until the summertime.

But I can still think and write, and have been making occasional posts in John Atwood's Clarisonus blog. One perennial question I always get is how to build an Ariel with XYZ drivers (and of course a different crossover and cabinet). As mentioned in my Web page, it take me about six months to design a speaker, and isn't something I do on a whim, or something to "use up" some drivers that are lying around.

The Ariel is now about 12 years old, and my tastes have changed a bit in the meantime. No, I'm still not a fan of horns, even though the horns I've heard here in Colorado are some of the best I've ever heard anywhere. Fabulous micro and macro dynamics, but I still have reservations about tonality with classical music, especially the big-scale choral music I enjoy so much.

The speakers design I'm exploring these days are large-diaphragm dipoles - hearing both the Linkwitz Beethovens and the Bastani Apollo was a revelation about the dipole/open baffle sound. Interestingly, both the Linkwitz and Bastani designs get to similar place via completely different methods: Linkwitz with extensive equalization and multi-amping with high-power transistor amps, and the Bastani with extensively modified 12" near-full-range drivers, and a subwoofer and supertweeter to fill out the range.

Both the Linkwitz and Bastani have stunning dynamics - almost in horn territory without the colorations - and the spaciousness and 3-dimensionality of electrostatics. I can see why many Europeans are turning to open-baffle designs: they do things that never happen in conventional speaker boxes.

Of course, there's never a free lunch: dipole speakers have unique design challenges all their own. The most obvious is the tilted frequency response that starts a half-wavelength below baffle width. Linkwitz attacks this with multiple crossovers, multiple drivers, and complex low-level equalization, which straightens everything out again. Bastanis, by contrast, stretches a single 12" driver to its limits, and helps it out below 220 Hz and above 8 kHz with a subwoofer and tweeter.

What I'm contemplating is a bit of both and a little different: a prosound 12 or 15" coaxial driver, with efficiency of about 97 to 99 dB/metre, and a supplemental 12 or 15" driver that comes in below 160 to 250 Hz (switch-selectable to match room characteristics). The upper driver runs full-range, and is acceptable with any Qts. The lower driver has a Qts from a 0.6 to 0.8, and carries the bass in the region where the dipole 1/f effect starts to be significant. Below 80 Hz, bass is carried by stereo subwoofers in close proximity to the dipole array, and the subwoofers are independently powered by their own amplifiers.

The dipole array as I'm imagining it has either 2 or 3 drivers: one full-ranger, of very high quality, and one or two bass-fill drivers, with tapped air-core inductors adjusting the overlap region. Dipoles in particular need to compensated for room-response, due to their unusual radiation pattern, and the inability of the user to optimize imaging and distance from the wall/corner at the same time. By adjusting bass-fill driver overlap and subwoofer levels, the response in the 20 to 500 Hz region can be optimized for the room, without compromising image quality (which is controlled by the mid and HF response of the driver).

Yes, this is very different speaker than the Ariel, although I hope to retain the midrange spaciousness and natural voice quality in the new design, along with a 15 to 20 dB increase in dynamic range.

For the current state of this project (known as the LTO) see here:
http://www.diyaudio.com/forums/showthread.php?p=3189501
And here:
http://www.diyaudio.com/forums/showthread.php?p=3190604


Scottmoose 27th March 2007 08:43 PM

Lynn, I'm sorry to hear you've had a fall -I wasn't aware of that until this post, but you have my very best wishes for a speedy and complete recovery.

You're tuning toward dipoles I find fascinating: quick anecdote, which you might find of interest. I was recently at a local audio meet (including a couple of Ariel owners BTW) where an interesting variation on the dipole was lurking. Powered by vintage 300a drivers from a rather special SET amp, they sang.

Nothing fancy at all. Cheap Eminence Beta 15 bass driver mounted fairly close to the floor, XO to a Fostex FE167E at ~180Hz. Series XO, utilising the natural roll-off of the drivers. The baffle is relatively narrow, roughly 16in, triangular side-pieces forming a semi U frame, roughly 12in deep at the bass, tapering to nothing at the top. Sonics were downright staggering. For the megre price, I've heard little that gets close. Easy 40Hz, seemless transition. I went hunting for the XO, and I flat couldn't find it. Design was by JamesD, who frequents the World Designs forum, and has much fancier & most expensive acrylic versions -effectively a very highly modified version of the original Quasar using a 12in Supravox bass unit and AER MK1 up top. Bass isn't really dipole in radiation pattern in this layout, but it certainly sounds like it, and the things can be used close up to a wall or in corners will little degredation. Don't ask me how or why -it's beyond me! Looks like you're working in the same direction -I look forward to seeing what you come up with!

Best regards
Scott

planet10 27th March 2007 09:05 PM

Lynn,

A speedy recovery to you...

The theme of a full range (or coax or full-range with super-tweeter) are becoming quite numerous, and the appeal of no box can become addictive.... it will be interesting to see your take on this challenge.

dave

SY 27th March 2007 10:04 PM

What advantages do you (or anyone else) see over large-panel ESLs?

Variac 27th March 2007 10:07 PM

Hey Lynn, welcome back!

I didn't realize that you are a member here.

I used to write you often about the Ariels with my newbie ideas and questions. You always answered and in fact took the time to consider my ideas and also explain why they might have problems or why a few of them were OK. Still have some of your e-mails. Thank you for that.

I had a lot to learn, so never built the Ariels, but probably cost you a fortune just for the number of times I visited your sites!

I ended up making the Basszilla speakers by Dick Olsher, with different 15" bass drivers, the Fostex 208SE in an open baffle, and the Aurum Cantus 2si ribbon tweeter. I managed to get him into discussions also, and I believe had some minor influence into the drivers he used and I built the tilting baffle he used as a testbed.

A lot of fun speaker projects have appeared recently and I 'm glad you are going to share your thought processes here.

Variac

planet10 27th March 2007 10:42 PM

Quote:

Originally posted by SY
What advantages do you (or anyone else) see over large-panel ESLs?
You can use small amps?

dave

Zen Mod 27th March 2007 10:59 PM

Quote:

Originally posted by SY
What advantages do you (or anyone else) see over large-panel ESLs?

Quote:

Originally posted by planet10


You can use small amps?

dave


bigger fuses have more dynamics :devilr:

SY 28th March 2007 01:54 AM

p10: Volts are cheap.

planet10 28th March 2007 02:07 AM

Quote:

Originally posted by SY
p10: Volts are cheap.
but not as sweet. And certainly not as frugal-phile cheap.

My whole hifi could almost fit into the sales tax of the amps needed to drive my last ESLs and they weren't as pleasant as my current 4 & 5W babies.

dave

Lynn Olson 28th March 2007 02:44 AM

More thoughts and comments on electrostats
 
Quote:

Originally posted by SY
What advantages do you (or anyone else) see over large-panel ESLs?
Stupendous dynamics combined with big-as-the-outdoors spatial and out-of-the-box quality. Normally, electrostats have that wonderful free-and-easy open-air quality that is so wonderful and so characteristic of electrostats. The nearly-massless diaphragm is part of that, but the absence of box coloration is a bigger part. Try putting electrostats in a box - of any kind, any shape - and see just how much of the wonderfulness disappears.

Parenthetically, I've been informally test-auditioning mid and midbass drivers in an IEC-style baffle for years - in fact, that's how I chose the drivers for the Ariel, as well as using the IEC baffle for a measurement platform. It just never dawned on me the rolloff problems could be conquered in a successful way by "working the problem" as Linkwitz and Bastini did.

What Rob Bastini brought to the table were prosound efficiencies of 97 to 99 dB/metre, instead of the audiophile efficiencies of 87 to 89 dB/metre of the Linkwitz designs, or the even lower 82 to 85 dB/metre of electrostats. I can tell you, that changes everything, combined with the insane headroom of prosound drivers.

Typical audiophile drivers start to exhibit dynamic compression from voice-coil heating at levels as low as 95 ~ 98 dB - and of course, 98 dB is nearing the danger zone for most electrostats. By contrast, prosound drivers, especially those designed for studio-monitor use, are quite happy with 115 to 125 dB. Once you get used to horn dynamics, you become very aware of just how compressed most audiophile drivers sound in comparison. Horns, unfortunately, still sound like horns, although the very best have diminished the coloration quite considerably.

(Where I get into wrangles with horn enthusiasts is their assertion that horn coloration has been eliminated for all practical purposes, or doesn't matter to "true" audiophile. Uh, not to me, and I design speakers for my own enjoyment, not the marketing department of Harmon International.)

The truly memorable part of listening to the Bastani was the combination of wide-open spaciousness and sound that had physical impact. Usually, you get one or the other, but not both. Horns, after all, aren't known for wide-open spatial qualities, with the soundstage only rarely extending beyond the speakers. Dipoles with prosound drivers have both qualities.

Some people prefer a restricted soundstage, and consider extra-width and extra-deep effects artificial. I don't - I've worked in surround sound since 1973 (the Shadow Vector patent and prototype with Audionics) - and know the difference between artificial and genuine reproduction of spatial characteristics. A good dipole, whether electrostatic or dynamic, plays the recorded ambience as recorded, not in a fake-reverb kind of way.

This is because the brain/mind/hearing system assigns sound into different processing "slots": 0-1 mSec is used for localization, 1-25 mSec is used for assigning ambient qualities (how big is the space), and anything delayed more than 25mSec starts to sound like an echo. So measures to reduce diffraction and stored energy in any kind of speaker are worthwhile, since most of the stored energy is going to fall into the 0 to 1 mSec interval, where it damages the sense of localization. Room reflections, including the first one off the floor, are benign - in fact, the floor reflection, although troublesome to measure, actually assists localization.

This is why dipoles don't "create" ambience, the simply allow you to notice what's on the recording. If you're listening to a 1944 Toscanini recording, it's going to sound as dry as the Sahara Desert. Chamber music sounds just like musicians playing in a small, lively room. Symphonies sound like they're in big halls, as they should, although running the solo mikes up and down is really obvious and silly-sounding, since the lucky instrument zooms forward and then scurries away once it leaves the spotlight.

The most noticeable - and unique to prosound dipoles - is the sheer sense of presence of big-sounding instruments like piano and kettledrums. These things sound real, not hifi. Electrostats just don't have the gigantic dynamics these instruments require, and with horns, you don't get that sense of the sheer size of the instrument, although you get the loudness. And to my ears, the audiophile line arrays sound artificial, overhyped, and incoherent. (Not surprising; when you have a multitude of drivers delivering the sound at slightly different arrival times - think of the path-length differences - the sense of impact and coherence isn't going to be there, thanks to the arrivals being smeared over that critical fisrt millisecond.)

Anyway, if anyone reading this little thread is truly ambitious, try the dipole thing with a 15" paper-cone Tannoy, and prepare to be amazed. The less you hear the cabinet, the better a driver is going to sound. If the driver is truly great, you won't hear it's full potential in a box - any box, I don't care what wonder material it's made of.

P.S. I broke my leg on January 7th, and I'm finding out These Things Take Time. The really awful part lasted less than a day, and since the surgery on January 8th, I've been pain-free, gradually recovering, transitioning from a cast to a removable boot, and more and more proficient in gizmos like walkers and crutches. The X-rays on the February 20th and March 20th still showed a break, but one gradually decreasing in size. I'm hoping (fingers and toes crossed) that the next one on May 1st shows the break all gone, so I can start using a cane to get around.


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