No such thing, it appears to be GPA's attempt to replicate the Altec 288-8G, which I am familiar with and it's nominally flat response out to 15 kHz before it 'falls off a cliff' when on the right horn, but the bottom line is that it's a ~ 5 kHz [or ~9 kHz depending on how one chooses to describe it] design with the extra BW basically just euphonic 'noise' AFAIK made available by increases in materials, etc., WRT diaphragm design, construction.
Maybe the 399's diaphragm is improved enough over the decades old 288's to be OK for most folks with keen hearing, but the driver itself, I doubt it with no measurements to compare with or at least a cutaway to see if its conical horn vent has changed any to extend its BW. There was a time when I enjoyed having top end 'air' on the better recordings, but it's long passed.
Thing is, if not designed for drivers with conical WG inserts, they won't improve over traditional horns.
GM
Ah! Yes, 311-90 is the heavy duty cast version of the 329A, which I like even better. Hate the sectoral horn's vanes!
http://greatplainsaudio.com/wp-content/uploads/2016/06/329A_hfhorn_spec_sheet.pdf
The 311-60 requires such a long LP that I had no use for them, but two perched on top of a 211 horn cab setting on an outdoor stage was something else! Even better if on top of an RCA Ubangi.
Note Altec 288-8G/329 response; doesn't get much, if any, better than this with vintage gear:
GM
Hate the sectoral horn's vanes!http://greatplainsaudio.com/wp-content/uploads/2016/06/329A_hfhorn_spec_sheet.pdf
The 311-60 requires such a long LP that I had no use for them, but two perched on top of a 211 horn cab setting on an outdoor stage was something else! Even better if on top of an RCA Ubangi.
Note Altec 288-8G/329 response; doesn't get much, if any, better than this with vintage gear:
GM
To all,
So is a Yuichi style horn better than an equivalent tratrix from 700-800 to 20k?!
The radials are not 'better', they beam less.
Of all the oldskool horns, the radial variants are still used in many highly regarded speakers; LV Vox series, Augspurger, JMF-Audio HPM etc.
Last but not least, the JBL 4367's waveguide is a modernized (bi-) radial horn and the Everest DD67000's mid-horn is basically an inflated H9800 with roundovers.
Of all the oldskool horns, the radial variants are still used in many highly regarded speakers; LV Vox series, Augspurger, JMF-Audio HPM etc.
Last but not least, the JBL 4367's waveguide is a modernized (bi-) radial horn and the Everest DD67000's mid-horn is basically an inflated H9800 with roundovers.
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The WE aficionados, including Joe Roberts, do not use their vintage horns according to modern standards.
They mount a WE 728B or Altec 414 in an Onken cab, let it run full range and put a WE32A (B, C) on top, which is then 'blended in' to cover the remaining frequency band.
The horn is basically used as a tweeter >3000Hz.
I am not familiar with the old wideband cone drivers, but I am certain this compromise won't work with modern woofers.
Besides, this 'solution' largely ignores most of the principles under discussion in this thread, f.i. matching woofer + horn directivity.
They mount a WE 728B or Altec 414 in an Onken cab, let it run full range and put a WE32A (B, C) on top, which is then 'blended in' to cover the remaining frequency band.
The horn is basically used as a tweeter >3000Hz.
I am not familiar with the old wideband cone drivers, but I am certain this compromise won't work with modern woofers.
Besides, this 'solution' largely ignores most of the principles under discussion in this thread, f.i. matching woofer + horn directivity.
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A narrow opening in general means that there will be wide dispersion at the lower frequencies but much more narrow at higher frequences. I would never consider narrow opening as a good thing.
An interesting modern horn is the 1.4" one from Ciare:
http://oem.ciare.com/pdf_oriz_3.php?info=450
It basically opens up conically in the horizontal axis. And in the vertical axis it opens such that the area follows a hyperbolic rule. It is constant directivity in the horizontal plane and narrowing in the vertical - like the radials do. I have never herad it though. One interesting thing is that its entry angle is the same as the Radian 745's exit angle.
A disadvantage is the narrow beamwidth.
Regards
Charles
http://oem.ciare.com/pdf_oriz_3.php?info=450
It basically opens up conically in the horizontal axis. And in the vertical axis it opens such that the area follows a hyperbolic rule. It is constant directivity in the horizontal plane and narrowing in the vertical - like the radials do. I have never herad it though. One interesting thing is that its entry angle is the same as the Radian 745's exit angle.
A disadvantage is the narrow beamwidth.
Regards
Charles
The OS throat is probably the best 'compromise' (no pun intended) and Dr. Geddes deserves all respect for the invention by working out the maths behind it.
The magic of the OS is - what I like to refer to as, "the pull-out trick".
In simple words: the throat pulls out the wavefront at high frequencies, even those at the wavelength is smaller than the throat circumference.
As a result there's no beaming all the way up to 20k.
Due to the short throat there's hardly any loading of the driver below, say 800-1000Hz.
Is this problematic? Dr. Geddes doesn't think so, but I would still be interested in a "1P to the power of 1.4" OS throat
The magic of the OS is - what I like to refer to as, "the pull-out trick".
In simple words: the throat pulls out the wavefront at high frequencies, even those at the wavelength is smaller than the throat circumference.
As a result there's no beaming all the way up to 20k.
Due to the short throat there's hardly any loading of the driver below, say 800-1000Hz.
Is this problematic? Dr. Geddes doesn't think so, but I would still be interested in a "1P to the power of 1.4" OS throat
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It's both, because the change in area is dictated by the change in curvature, aka flare rate.
However, these may vary in the horizontal versus vertical plane for asymmetrical horns, mostly with diffraction slots.
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Hi, i could not say which one is better but i've heard many radial variant ( from TAD TH to Yuichi clone) with different CD ( from Tad, Jbl 2450, Das K8, Radian) in different listening space ( professional control room to small untreated domestic room) used in different philosophy ( from passive to dsp FIR processed) and they all have a certain 'flavor' in common.
I don't know if it is the horn, the 2" cd or both but all shared some attribute about dynamic and 'full' sound. That said i've never found them very pleasing to MY ears in the high range ( including the Tad 2" cd).
I've found too that where and how they are crossed and to which driver and configuration have impact on the overall presentation: for example the tad 16XX 15" give a 'cardboard' sound in the 800hz area which really bother me.
The twin horizontal 12" make for a very small sweetspot which i dislike.
The one i liked the most was with MTM of 15" Davis carbon driver with a dsp processed filter. No cardboard sound and larger horizontal sweetspot despite a more pronounced vertical one. Much less variation with listening volume ( the passive one i've heard had this in common: once you push them the image rendering 'shift' in the stereo if i can say).
All in all i think this more a preference thing about the trade off: can you stand longterm the high ( signature sound) or not.
Ro808: thank you for jericho's and sm80 review!
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while we are on the topic can I ask one more question:
I often see flare rate specified as a frequency, ostensibly the cut off frequency of a horn with that flare rate. Is there a mathematical formula for this or is it just a heuristic?
To me a "narrow opening" means that horn is narrow at the mouth, i.e. that the dimension of the mouth is small compared to a length. Then the beamwidth will narrow rapidly from low to high frequencies - not a good thing.
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Sure, the curvature effects the area expansion, although less than the starting area for determining rate of expansion
If using area expansion as the definition of flare rate:
Isn't the highest flare rate at the throat where curvature is lowest?
And the lowest flare rate at the mouth where curvature is highest?
I think this is why I get confused when flare rate is interchangeably used to describe both area expansion and curvature...since high and low descriptors get swapped...
You're welcome!
It was the SH96HO (instead of the SM80) btw
Thank you for sharing your experience with the TADs and Yuichi!
It occurred to me the JMF Audio 40HTS200 16" carbon coned woofer (posted yesterday), may very well be the result of a cooperation between JMF and Davis...