Beyond the Ariel

[Cloth Ears]

Lynn,

I'll be very interested in reading anything you put up in the way of ideas... and have been since I first saw one of your Ariel articles in the mid-90's ('97?).

Originally posted by Lynn Olson
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.

Leaving the more complex boxes out of the equation here, with regards the dynamics, do you think this due to the open baffle design itself (the ease of moving the cone only against air in both directions) versus conventional boxes (where the cone moves against an enclosed volume of air and only produces air movement from one side of the cone)?

What co-ax have you looked at with regards the primary driver? Something along the lines of a Tannoy, possibly?

Anyhow, please recover swiftly and post more often !

[Lynn Olson]

Originally posted by Cloth Ears
Lynn,

Leaving the more complex boxes out of the equation here, with regards the dynamics, do you think this due to the open baffle design itself (the ease of moving the cone only against air in both directions) versus conventional boxes (where the cone moves against an enclosed volume of air and only produces air movement from one side of the cone)?

What co-ax have you looked at with regards the primary driver? Something along the lines of a Tannoy, possibly?

Stored energy grossly degrades the sense of realism in every way: it steals dynamics, compresses and distorts the soundstage (which is why I always audition in stereo), and almost flattens the sense of depth completely. It's like MP3 with extra colorations thrown in free.

Unfortunately, there are many many sources of stored energy, particularly in the first few critical milliseconds. Cabinets have standing waves and wall flexing, horns have significant diffraction at the horn mouth (which then travels back down the throat and reflects off the phase plug), and worst of all, cabinet damping materials don't really work well below 500 Hz. All this is quite audible, particularly when you hear the coloration go away. This kind of coloration is the kind of thing you notice in the first few seconds of listening - and we only tolerate it because that's how 99.999% of speakers sound, and have always sounded since the Twenties.

Electrostats store energy too, although far less than direct-radiators in boxes or any horn. Where the electrostat falls down are a series of small mylar-diaphragm resonances between 3 and 10 kHz, which is noticeable on a MLS waterfall measurement (although easily confused by different arrival times from different parts of the diaphragm).

All drivers fall down here, compared to what can be done with plasma drivers. In my experience - speaking for right now, anyway - cabinet colorations are considerably worse than driver colorations, at least with decent-quality modern drivers. With an old-school driver like the Altec 604 Duplex, OK, I doubt that cabinets make a lot of difference. But when coloration levels go down, cabinet coloration becomes much more noticeable, and is very difficult to reduce. Exotic cabinet materials really only help a little bit, and introduce odd new colorations of their own. (It takes magazine reviewers several years to realize a new type of coloration has been introduced.)

As for new drivers, well, I've tried getting OEM Tannoys for many years, with no luck. As far as I can tell, Tannoy only wants to sell complete systems, without the nuisance-factor of the DIY market. Can't say I blame them. So I'm looking at prosound folks like 18Sound, B&C, and Beyma.

[Lynn Olson]

There are some good suggestions in the coax thread going on elsewhere at diyAudio: I spotted this driver from BMS of Germany, who make very serious prosound drivers:

12" BMS Coaxial

The complete list of BMS drivers is here

Now, the specs for coax drivers have to read very carefully. The combined curve is useless; what you want are the separate curves for the woofer and tweeter, paying particular attention to the rolloff region of the woofer. In a high-quality speaker, this needs to be as smooth as possible, both to decrease coloration and assure a smooth phase hand-off to the tweeter. Just because it's a coax doesn't mean you can get away with sloppy crossover design.

Unfortunately, the horn in front the woofer diaphargm creates standing waves, and these create reflections (stored energy, remember?) in that critical 0-1mSec timeframe. The frequency response curves for the woofer tell what you need to know about the potential candidate - can it be reasonably equalized, and will it sound good afterwards? Radical equalization has a way of sucking the life out of the driver, and leaving it alone is a prescription for an annoying coloration that ultimately becomes tiring to listen to.

I mention the BMS 12C362 above because the EQ for the woofer looks pretty simple: a notch filter at 2.2kHz, about one octave wide, and about 5 dB deep. Use a 2 kHz 12dB/oct or 18dB/oct highpass and a shelf filter on the tweeter, and there you go. Note this driver is 98dB/metre, and easily plays up to 124dB. Is that enough dynamic range?

[MJL21193]

Originally posted by Lynn Olson


As for new drivers, well, I've tried getting OEM Tannoys for many years, with no luck. As far as I can tell, Tannoy only wants to sell complete systems, without the nuisance-factor of the DIY market. Can't say I blame them. So I'm looking at prosound folks like 18Sound, B&C, and Beyma.

Have you consiered Eminence? Also worth looking at:http://www.maxspeakers.com/products/fidelity/index.html

They have pro drivers up to 54cm, paper cone, 100+ db.

[Lynn Olson]

The Beyma 12XA30Nd

The thread that discusses some very interesting modern coax drivers is here

The crossover would still need a modest notch filter at 2.2 kHz, and a rolloff at about 6 or 12dB/oct starting at 3~4 kHz to get rid of the HF debris in the woofer. The tweeter doesn't look like it needs a shelf filter, which is a good thing.

[BudP]

Those of you who are thinking seriously about this speaker format might want to read another thread also, assuming you haven't already.

I start you off where the ultra low storage termination information begins and there are two very different methods for perfectly terminating a big driver without a bunch of storage mass.
OHM Acoustics "Walsh F" Speaker remakes


And yes this is a thread here in DIY

Bud

[Irakli]

Welcome back Lynn. Wish you fast recovery

[Cloth Ears]

Originally posted by Lynn Olson
Stored energy grossly degrades the sense of realism in every way: it steals dynamics, compresses and distorts the soundstage (which is why I always audition in stereo), and almost flattens the sense of depth completely.

A fellow audio enthusiast at the Melbourne Audio Club also has found this, but actually as a result of building his last pair of speakers. I don't think they were intended as such, but that is what he thinks now. He says that he has pretty much given up the idea of building anything else and finds box speakers are now far too colored to go back to. He likes to listen to them at the club meets but hasn't heard anything he prefers since the set-up was completed.

A small indication of them is here at Bob F's hybrid ribbon speakers. I'm sure I can get more details if you wish.

I do understand your intent is to use available cone drivers/co-axials, so I won't OT this thread anymore.

[ScottG]

Ah Lynn.. my favorite in the HiFi "world"..

While I'm generally no fan of horns.. consider that a good bit of a cone driver's bandwidth at higher freq.s is in fact horn loaded. The larger the driver the lower the freq.. and the worse it is - bastini's in particular. Just about any coax has a similar reality. Really flat drivers (the manger in particular) of course "buck" this trend to some extent depending on their profile.

Worse still, the "horn" for these cone drivers is moving around.

Heck.. even a baffle acts as a horn.

Also note that most pro drivers have increased distortion at lower spl's near the top of their passband (at higher freq.s) due to larger VC's (when compared to better hifi drivers). Both linear and non linear. Additionally, while they do exhibit less thermal compression.. they often suffer from mechanical compression that won't allow a lower freq. response anywhere near their max spl rating (..not that it should be a problem for anyone in a domestic setting - unless they are insane, or deaf and neighbor-less).

Despite the above.. I'm pretty much lock-step with your views. I just like hi eff. drivers better, more energetic/dynamic and IF they are of lower mass then they seem to offer greater clarity. Also, I've noted that linear decay is critical at least 9-10 db when factoring time - the shorter the better. Oddly though, HOW you achieve a cleaner decay is extremely important. Drivers with high internal loss and only moderate or worse ability to react to change, despite having *overall* cleaner decays (i.e. are "cleaner" further in time and level) sound significantly less clear. Likewise, drivers with acoustic resistance (particularly near time acoustic resistance), often via box stuffing and panel friction, kill ambiance and make the sound more monophonic (and "attached to the speaker").

I however specifically do NOT prefer a dipole pattern above the modal region - it creates a "sameness of sound" from recording to recording.. and in comparision to a really good enclosure falls short on depth. My preference is for a radial in the midrange and a wide dispersion pattern higher in freq. approaching 180 degrees (..when considering the front wall in a listening room). This does make several demands on both the "box" and the driver..

[JoshK]

Great to see you here Lynn! I've been pestering you about the Karna design for months, going on a year. I too am working on OB speakers, namely the Arvo Pärt, or a variant thereof.

If I could, I'd suggest you take a brief read through the "Isiris" thread on htguide.com (under mission possible diy). This is an evolution parrallel to Linkwitz's own evolution from the Pheonix onward. This design, although not set in stone, is taking some tools from the pro audio world in its development.

There may be some useful info in that project that may help guide your own.

Hope you get better quickly!