f(xo) of Augspurger mains?

[ChrisKoehn]

Hi everyone,
as there are no Augspurger-designed control rooms in the immediate vicinity of Hamburg (the next would be in Amsterdam, as far as I know, and that's a six-hour drive...) I don't have the chance to measure one of G.A.'s famous mains... but after checking this old post:

http://www.audioheritage.org/vbulletin/showthread.php?19390-Augspurger-Horn-Pictures

(thank's for the pics, Glen!) I started to wonder about the general concept of the design.
I was told by a colleague that f(xo) of the "standard", current, G.A. monitor is ~1600Hz, depending on customer/room requirements... well, this seems rather weird in a dual-woofer design with a 4'' diaphragm driver... at least to me. The rather smallish dimensions of the horn however show that f(xo) might be somewhat higher than with Kinoshita/Hidley, Westlake, TAD, "pre-stage-accompany-ribbon" Yanchar/Sierra and the like of custom mains...
let alone JBL's (in my personal opinion correct) decision to exclusively use 1'' drivers in studio
monitors, even in two-way-designs (4320, 4430). But if there is such a thing as an authority on control room/mains design, its George Augspurger, so he certainly gave the Monitors he is standing for with his very name a thought or two....
Any comments?
kind regards,
Chris

[Mr. Widget]

Can't comment on the crossover frequency issue other than in my experience most horns are crossed over lower than ideal. In my experience bumping the crossover frequency up a bit is almost always preferable... or use a larger horn.

On the subject of 1" vs. 2" exit drivers, I tend to disagree with your premise. In my experience having lived with both from JBL and TAD, the 1" drivers are an economic compromise. The 2" exit drivers always have a more relaxed and natural sound... not that 1" drivers can't sound very good, it is simply that in every application the larger drivers sound better. I also advocate a super tweeter of some type. I do not think either compression driver really is ideal without one, though with Be diaphragms you can sometimes get away without a super tweeter.

Widget

[ChrisKoehn]

Widget,


thanks for the reply! Ahhh... the old „large vs. small format“ debate...
I am somewhat reluctant to argue about „sound“ in any other setting than the two of us sitting in the same control room listening to the same material thru the same monitors (as you know, one man's „brilliant“ is another man's „harsh“...); the concept of „sound“ as a whole cognitive and conscious experience is, in my opinion, by far too complex and much too subjective to have any more substance than a „personal opinion“ (in the context of newsgroup exchange in written form, that is).


But anyhow, even the (much easier to communicate here) realm of acoustic measurements isn't really helpful (and I'm generalizing here...) : 3''- 4'' dia. diaphragms have less mid frequency distortion, 1-3/4'' diaphragms have less hi frequency distortion, large diaphragms have lower usable f(xo), small diaphragms have better hi frequency extension, large drivers got higher max. SPL, small drivers are a lot cheaper... and so on...


There are quite obviously two „camps“ of design „philosophy“ (oh, how I hate to use this term in such a context...),


the „large format camp“ (Shozo Kinoshita, George Augspurger, and Mr. Widget, for example)


and the „small format camp“ („Don“ Keele, Earl Geddes, and ChrisKoehn, for example)....


With both sides having commercially sucsessful products and critically acclaimed peer reviewed papers to their merit.


My personal bias towards single woofer/1-3/4'' diaphragm designs certainly stems from me having worked with 4430 mains for over 15 years, so any dual woofer/4'' diaphragm loudspeaker system sounds „wrong“ to me, simply because it doesn't sound like the system I have learned to compare to other systems as a „default“.


Supertweeters... hmmm.... the 077 and it's successors are among the most elegant designs in the history of electroacoustics... and their application in system design among the most ugly... How do you properly integrate any driver at f(xo) of 6 to 8 kHz? The diameter of the unit alone is >= lambda, so
in any real world system you get to >>lambda... and that to improve performance at frequencies where most people in pro audio, whether from the orchestra pit, the tour band, or the control room, are stone deaf anyway! (my hf-hearing, by the way, is still rather ok for a music man in his forties...lucky basterd, me...)


...Oh, we're off-topic, aren't we?:blink:


Luv,
Chris

[Mr. Widget]

You can add Greg Timbers and John Meyer to the large format camp...

as for super tweeters... I always go for ~10KHz or even higher if possible. There is no way not to have some comb filtering and the higher up they are the harder that is to hear.

On the topic of HF breakup and smaller diameter compression drivers... use Beryllium. :D



...Oh, we're off-topic, aren't we?:blink:
Always!


Widget

[CONVERGENCE]

Hi everyone,
as there are no Augspurger-designed control rooms in the immediate vicinity of Hamburg (the next would be in Amsterdam, as far as I know, and that's a six-hour drive...) I don't have the chance to measure one of G.A.'s famous mains... but after checking this old post:

http://www.audioheritage.org/vbulletin/showthread.php?19390-Augspurger-Horn-Pictures

(thank's for the pics, Glen!) I started to wonder about the general concept of the design.
I was told by a colleague that f(xo) of the "standard", current, G.A. monitor is ~1600Hz, depending on customer/room requirements... well, this seems rather weird in a dual-woofer design with a 4'' diaphragm driver... at least to me. The rather smallish dimensions of the horn however show that f(xo) might be somewhat higher than with Kinoshita/Hidley, Westlake, TAD, "pre-stage-accompany-ribbon" Yanchar/Sierra and the like of custom mains...
let alone JBL's (in my personal opinion correct) decision to exclusively use 1'' drivers in studio
monitors, even in two-way-designs (4320, 4430). But if there is such a thing as an authority on control room/mains design, its George Augspurger, so he certainly gave the Monitors he is standing for with his very name a thought or two....
Any comments?
kind regards,
Chris

The XO point in the original design was 700 HZ. The tweeter at 10K. The JBL woofers replaced by TAD .These could use more pounding.They sound similar to JBL.

.....................

[ChrisKoehn]

The XO point in the original design was 700 HZ. The tweeter at 10K. The JBL woofers replaced by TAD .These could use more pounding.They sound similar to JBL.

.....................

Thanks, C.
Yes, this seems a rather "standard" approach for a three-way monitor with 2'' Driver + Supertweeter.
With G.A.'s more recent two-way monitors, however the horn itself just seems too small to
offer proper loading and pattern control down to the usual 500 - 800 Hz f(xo) for large format compression drivers:

http://www.proaudiodesign.com/image.php?type=P&id=182

but maybe i am simply wrong on that...:confused:

regards,
Chris