chrismercurio said:
From the Onken thread ...
IslandPink said:
Is that what you were thinking of?
As for the Audax ... um, well, I heard them a long time ago, back in the late 70's, and I thought they were reasonably good drivers that didn't require a lot of equalization. As I recall, they had very short Xmax, and were essentially midranges requiring a 200~300 Hz crossover for satisfactory performance.
In terms of smoothness and freedom from resonance, the Vifa 5.5" drivers in the Ariel are significantly flatter, have an extremely well-behaved rolloff region, and very rapid decay characteristics. But the efficiency is nearly 10 dB less, not a small difference. And using drivers in arrays does NOT give the same performance as a single, higher-efficiency driver. Just hassling with a pair of drivers added many months of hassle to the Ariel project - and that was with drivers that are as close to technically perfect as anything I've ever used. The prospect of using 2 or 4 drivers that are rougher, and have more pronounced breakups in the 3~10 kHz region, is very unappealing. The current fashion is brute-force 24 dB/octave crossovers (or ignoring the coloration), but I don't want to go down that path.
I tend to have strong go/no-go reactions to drivers. If I hear something special - an especially lyrical midrange, HF, or bass (in that order), I take note and try to find out what's going on that makes it special. I basically discount other people's opinions - sorry, no offense to anyone here - unless I know them and their taste personally. So I give weight to Gary Pimm, John Atwood, and Alexander, although I think Alex and I have different tastes in the midrange.
I haven't heard the new Jean Hiraga 604 Duplex, for example. The last time I heard a traditional 604, the midrange was one of the most colored and aggressive-sounding I ever heard, so the magnitude of the task facing Mr. Hiraga was enormous. On the other hand, he is one of the most experienced audio designers in the world, and has excellent tastes musically - so if anyone could pull off the near-impossible, it would be him. I wouldn't even attempt what he's done.
Sometimes I wonder why anyone listens to me. I'm a pretty lazy designer, and try and use the most linear devices I can find (flattest response, least energy storage, etc.) so I can concoct something around that. I kind of admire folks who visualize a Platonic Ideal of a loudspeaker, and work from the top down to bring the realization to the physical world. I just look for the prettiest pebbles on the beach, and make something around them.
More along the lines of a deluxe version of this:
http://www.6moons.com/audioreviews/auditorium232/solovox.html
I am curious about Gary's enclosure though. Do you have any pictures of that? I like the links to the Jensen enclosures.
Thank you,
Chris
http://www.6moons.com/audioreviews/auditorium232/solovox.html
I am curious about Gary's enclosure though. Do you have any pictures of that? I like the links to the Jensen enclosures.
Thank you,
Chris
There are some pix in the Issue 20 article of Positive Feedback magazine. Dave Robinson, the editor, lets me get away with an over-the-top style - so it ended up as a mashup of film noir, science fiction, and audio. Portland still looks a lot like the 1936 pix, by the way - just add water glistening on wet pavement, and the Chandler mood is already set. (Many inside jokes for the entertainment of the Portland Triode Society - all the locations are real.)
The last I saw of Gary's system (a couple of years ago), the mids were in open-ended boxes filled with Bonded Logic Ultratouch insulation, made from recycled blue jeans. This stuff has none of the scratchiness of fiberglass, and has very good broadband acoustic absorption. Think of a 1-cubic-foot wedge of the stuff in the mid and bass enclosures, and you get the picture. He also used a lot of rope caulk to quiet down the stamped-metal frames of the Beta 8's.
The crossovers are low-Q, low-order passive networks between the ribbon tweeters and the Beta 8's, and active Behringer lowpass for the damped-dipole W-baffles for the subwoofers. The subs use pairs of 15" drivers for each channel, and the heavily-modified Behringer is kept out of the mid/high signal path - all it does is EQ the woofs for the room and roll them off before the W-baffle goes into its first mode.
The last I saw of Gary's system (a couple of years ago), the mids were in open-ended boxes filled with Bonded Logic Ultratouch insulation, made from recycled blue jeans. This stuff has none of the scratchiness of fiberglass, and has very good broadband acoustic absorption. Think of a 1-cubic-foot wedge of the stuff in the mid and bass enclosures, and you get the picture. He also used a lot of rope caulk to quiet down the stamped-metal frames of the Beta 8's.
The crossovers are low-Q, low-order passive networks between the ribbon tweeters and the Beta 8's, and active Behringer lowpass for the damped-dipole W-baffles for the subwoofers. The subs use pairs of 15" drivers for each channel, and the heavily-modified Behringer is kept out of the mid/high signal path - all it does is EQ the woofs for the room and roll them off before the W-baffle goes into its first mode.
Another great thing about Bonded Logic is the price. Since it is marketed to home builders its very reasonably priced unlike the "special" audio grade stuff. I agree that the ST and NRC numbers for the material are excellent. I will look up the issue after I go home. Long day today,
Chris
Chris
I really like this picture - it's astonishing that downtown Portland still looks so much like this. Entirely appropriate to the 1935 vintage of the Western Electric 300A/B and the WE 86 and 92 amplifiers with Class A PP and Harmonic Balancer topologies. It's a good question which amplifier the "Liberty Theatre" used - the 92, 86, 43, RCA, or maybe it was a burlesque theatre. Probably not the latter - Broadway was the main street back then, and still is today.
The image quality of the Speed Graphic that was probably used for this picture had nothing to apologize for, either. The 16 x 20 print from the Oregon Historical Society that I scanned for this pix looks really good.
The image quality of the Speed Graphic that was probably used for this picture had nothing to apologize for, either. The 16 x 20 print from the Oregon Historical Society that I scanned for this pix looks really good.
Attachments
Lynn Olson said:
Yes, still the same. (Quite an impressive system, BTW. Clean, clean, clean).
Here is a link to a very good group of tables showing Absorption Coefficients and NRC for many, many materials. Roxul, Bonded Logic, Owens Corning, etc.
http://www.bobgolds.com/AbsorptionCoefficients.htm
There are, but I'm not at liberty to share the data. I can report the measurements in the time and frequency domains for the Azurahorn AH425 and Altec/GPA 288 compression driver look very, very good. As reported elsewhere, the T=0.707 JMMLC horn is nowhere close to constant-directivity, but on the other hand, the data shows that it requires little to no equalization. Since I've been planning on using a supertweeter all along, the absence of CD is not a major concern. I'm still not 100% sold on the subjective qualities of CD horns, but that's a matter of personal taste.
I've been reflecting about what I want to accomplish, and the primary focus, more than ever, is minimum stored energy (combined with generous headroom). In measurements, stored energy appears as the "clutter" that appears after the initial impulse, or the extended ridges that appear in a CSD measurement. The AH425 & 288 are in the right ballpark from the preliminary data I've seen, and the first subjective reports.
I am working on a novel enclosure that is transitional between a "pure" dipole open-baffle and Gary Pimm's quasi-cardioid cotton-filled boxes with the rear panel open. That boxes store energy is well known - but classical dipoles also have the backwave diffract around to the front after a 1~2 mSec delay. This is also undesirable, although not as bad as the extended resonant signature of a closed box. I'm experimenting with lossy structures that aim for moderate (6~12 dB) attenuation of the backwave while avoiding mass-coupling effects on the midbass driver (which degrades efficiency, HF response, and transient response).
The Great Plains Audio Alnico 414's look like keepers - I'm now deciding between using a single or a pair per side. The pair has the charm of 101 dB/metre efficiency, and more headroom. Early tests indicate the AH425/288 works well all the way down to 600 Hz, so that gives more flexibility in the choice of the midbass drivers.
Healthwise, it's a matter of gradual improvement. I now have a personal trainer and work out at the gym three times a week - the goal is to improve symmetry of the muscles, and improve walking and running (which I was able to do for the first time a few weeks ago), and going up and down stairs with better safety. It's true, just like audio, the last 10% takes 90% of the work, time, and effort.
I've been reflecting about what I want to accomplish, and the primary focus, more than ever, is minimum stored energy (combined with generous headroom). In measurements, stored energy appears as the "clutter" that appears after the initial impulse, or the extended ridges that appear in a CSD measurement. The AH425 & 288 are in the right ballpark from the preliminary data I've seen, and the first subjective reports.
I am working on a novel enclosure that is transitional between a "pure" dipole open-baffle and Gary Pimm's quasi-cardioid cotton-filled boxes with the rear panel open. That boxes store energy is well known - but classical dipoles also have the backwave diffract around to the front after a 1~2 mSec delay. This is also undesirable, although not as bad as the extended resonant signature of a closed box. I'm experimenting with lossy structures that aim for moderate (6~12 dB) attenuation of the backwave while avoiding mass-coupling effects on the midbass driver (which degrades efficiency, HF response, and transient response).
The Great Plains Audio Alnico 414's look like keepers - I'm now deciding between using a single or a pair per side. The pair has the charm of 101 dB/metre efficiency, and more headroom. Early tests indicate the AH425/288 works well all the way down to 600 Hz, so that gives more flexibility in the choice of the midbass drivers.
Healthwise, it's a matter of gradual improvement. I now have a personal trainer and work out at the gym three times a week - the goal is to improve symmetry of the muscles, and improve walking and running (which I was able to do for the first time a few weeks ago), and going up and down stairs with better safety. It's true, just like audio, the last 10% takes 90% of the work, time, and effort.
Lynn Olson said:
Then how are you feeling about the non-CD AH425 horn? It should be a lot more neutral than a typical horn. And that 288 is a great driver. =)
It would be nice to see some CSD plots from various amps and preamps. As a sort of baseline. They must be around somewhere...
Gary is doing great work with that cotton insulation. I saw some of the new configuration recently. Didn't hear, just saw. Interesting stuff- if you'll excuse the pun!
Glad to know you are actually running. Best of health to you.
First Glad to hear you are feeling better. At our age it is a long road, hope things continue to go well.
Sounds like your found the compliment of drivers. Sounds like the Horn is meeting your expectations. If you go with the 2 414's is the plan still to run 1 all the way up the the xover for the 288 and roll the other off an octave lower?
Sounds like your found the compliment of drivers. Sounds like the Horn is meeting your expectations. If you go with the 2 414's is the plan still to run 1 all the way up the the xover for the 288 and roll the other off an octave lower?
Lynn Olson said:
Then what is the point of this massive thread if there won't be any data presented to support any conclusions that are (maybe?) presented?
I don't see the correlation here... Not that CD is required to use a super tweeter per se, at least if that's not in your philosophy, and especially since most super tweeters are not CD, but it would still be a good idea to match the directivities so you don't have drastic changes in the timbre of the indirect sound.
IslandPink said:
We've been doing that is the Fonken/miniOnken for years.
http://www.planet10-hifi.com/fonken.html
If just used at low frequencies it wouln't have as much impact on diffraction as it does when uses in a FR box.
dave
planet10 said:
Dave,
It's insullation for 4" stud bays 1st, and cheap highly effective loudspeaker damping second. It also squishes down very well. I haven't tried to squash it to .5", but I bet you could get it down to a third of its normal thickness. I would try for you but the unit that I bought is completely populating a pair of 10.5 cubic foot MLTL's that GM and Jay Fisher designed. It really is too big for me visually, but the sound!
Best,
Chris
John Sheerin said:
The data that Lynn referred to isn't his, so we'll have to wait until he either makes his own measurements or receives permission from the other party. I am glad to hear encouraging news, even if things aren't moving quickly.
I now have my horns and drivers, and am hoping to have some measurements on the AH-425 and GPA 288-16H completed within the next week or so.
Gary Dahl
John Sheerin said:
The impulse and frequency-response data I've seen was from one of my collaborators, and he requested that it not be re-republished. As a courtesy to him, I am honoring his request. He expects to measure higher-quality data in the next few weeks. I expect to be doing my own MLSSA and ARTA measurements in the future, and these will be published here and on the Nutshell web-page.
I've been thinking about the importance of directivity recently. Case in point: the Quad ESL57, by any standard, has a pretty wacko frequency vs directivity pattern, far less well-controlled than modern Floyd Toole-designed speakers from Revel and the Harmon International group.
The distinguishing feature of the ESL57 is very low stored energy - from the cabinet (there isn't any), and from the diaphragm (which is very light and non-resonant). As a result it has extremely quick and non-resonant energy-decay characteristics.
Do I hear "drastic changes in the timbre of the indirect sound" from the ESL57? No, I don't. I hear a speaker that is more natural and realistic-sounding than nearly any contemporary speaker. It has obvious headroom limitations - 95 dB max under any condition - but within that constraint it is a superb loudspeaker. To my ears, at least, it's one of the very few speakers that can occasionally fool you into thinking it's the real thing.
The Ariels were specifically designed to mimic the sound of stacked ESL57's - they were designed for Mike Spurlock in Portland, who owned a pair of stacked Quads at the time. People who own Quads are surprised by how close the Ariels sound - well, that's not an accident. It was designed in. But the Ariels and Quads have radically different directivity patterns. What they share are similar energy storage patterns, and a similar direct-arrival frequency response.
I'm aware the modern consensus is to design speakers that have a tightly-controlled frequency vs directivity characteristics - preferably, not too wide, not too narrow, and constant with frequency. THX standards combined with Floyd Toole's research have steadily driven the industry in this direction over the last 15 years.
This is where I part company with modern speaker design. I just don't agree. My first priority is minimum energy storage, followed by flat response at the listening position, and then (in this project) ample headroom. Fortunately, as a retired guy, I don't have to report to a boss at Harmon International or comply with THX standards, or make the reviewers at $tereophile or Absolute $ound happy, so I can design speakers and amplifiers as offbeat and idiosyncratic as I like.
P.S. Planet10, yes, a scaled-up Fonken seems like a good candidate for the 414, for those who want to avoid the hassle and complexity of a bi-amped dipole system.
panomaniac said:
I know exactly what it is... after getting a sample about a tear ago, we bought a bale of the 3.5". It is lovely stuff, but most of our speakers need about the same density but 1/2" thick.
I have a bat downstairs i'm going to be using in a midTL i'm doing.
When we got it, we were told there was nothing thinner, if they have brought out some that would be very helpful. Edit: just went and looked, they now have 3/8" which would be useable, but the Al foil is something that would have to be worked around.
dave