I was reflecting on this part...and the low price
if you want to go cheap, and still have nice sound, I would suggest not xo/cross it low
so you mean don't cross it at x0, rather cross it about 3kc?
mcm carries this product.
Faital Pro 30W 8 Ohm - Bolt On Compre ion Tweeter Driver | HF100 | Faital Pro
ehh, factory recommended min 2k is safety margin for PA
for hifi 2k should be very good
admittedly, I only have the old one, which might be a little different
but seem to work well with 8uf and 1ohm in series, and 1mH with 10ohm in paralel to ground
edit...looking at spec sheet graph, impedance ressonance starts rising just below 2khz, which might explain why I experience distortion with bigger caps, but with 8uf there is none, it seems
In my limited auditioning of potential 15" drivers, the modern GPA 416-Alnico-16ohm sounded much better than the contemporary JBL equivalent. But they're very different drivers: the JBL has a heavy cone, a 500-watt power rating and 4" voice-coil, and is obviously intended for theater and sound-reinforcement use, while the Altec cone is 25 grams lighter, the voice coil smaller, has a much lower power rating, and is about 2 to 3 dB more efficient.
What surprised me was how smooth the response of the GPA is: a broad, low-Q rise at 1.5 kHz, but well-controlled, with no narrowband peaking, and (very) smooth rolloff above that. Many of the modern 15" prosound drivers have pretty rough response above 1.5 kHz, and sound like it.
The GPA 416-Alnico-16ohms works very well with a 700 Hz 3rd-order Gaussian/Bessel lowpass filter, combined with a Zobel for inductance compensation. Very very smooth response, as good as any of the Scan-Speak audiophile confections, but with 12 dB more efficiency.
A 700 Hz 4th-order highpass, transitional between Bessel and Linkwitz-Riley, is close to the optimum filter for the Radian 745Neo & AH425 Azurahorn combination. Combine the GPA 416-Alnico with the Radian/Azurahorn, and the response in the 500 Hz to 3 kHz region is within +/- 1.5 dB, pretty good for a system that is around 99 dB/meter/watt efficient.
Thanks for the mention of the Celestion 1530; it'll be interesting to see how it compares (by measurement and audition) with the Alnico GPA 416.
What surprised me was how smooth the response of the GPA is: a broad, low-Q rise at 1.5 kHz, but well-controlled, with no narrowband peaking, and (very) smooth rolloff above that. Many of the modern 15" prosound drivers have pretty rough response above 1.5 kHz, and sound like it.
The GPA 416-Alnico-16ohms works very well with a 700 Hz 3rd-order Gaussian/Bessel lowpass filter, combined with a Zobel for inductance compensation. Very very smooth response, as good as any of the Scan-Speak audiophile confections, but with 12 dB more efficiency.
A 700 Hz 4th-order highpass, transitional between Bessel and Linkwitz-Riley, is close to the optimum filter for the Radian 745Neo & AH425 Azurahorn combination. Combine the GPA 416-Alnico with the Radian/Azurahorn, and the response in the 500 Hz to 3 kHz region is within +/- 1.5 dB, pretty good for a system that is around 99 dB/meter/watt efficient.
Thanks for the mention of the Celestion 1530; it'll be interesting to see how it compares (by measurement and audition) with the Alnico GPA 416.
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Lynn,
My only question about the GPA driver is why in this day they would use a 16ohm impedance unless they were expecting the driver to be used in a parallel condition with more than one driver? That is only going to raise the moving mass with the extra voicecoil weight unless that was an intention to lower the fs of the driver through extra mass and an overhung motor design.
My only question about the GPA driver is why in this day they would use a 16ohm impedance unless they were expecting the driver to be used in a parallel condition with more than one driver? That is only going to raise the moving mass with the extra voicecoil weight unless that was an intention to lower the fs of the driver through extra mass and an overhung motor design.
The GPA 416-Alnico is available in both 8 and 16 ohms; your choice when you order. The change in cone & VC mass is very small, most likely a few grams. Voice coils aren't that heavy in comparison to the cone. A bigger change in VC mass would probably result from 3-inch to 4-inch, which substantially increases the radiating area of the VC.
I chose 16 ohms because there is a possibility I will build a dual-15 version of the new speaker. 3 dB gain in efficiency, 6 dB gain in headroom, several dB drop in IM distortion, at the expense of a bigger (and heavier) cabinet. One driver might have a slightly different crossover than the other; if I build this version, I'd experiment with that.
As for tube amp vs transistor amp, this loudspeaker is optimized for tube amps: low-Q crossover and low-Q bass alignment that are not too sensitive to source impedance (damping factor). The design-center of the assumed source impedance for the loudspeaker is in the 0.5 to 1.5 ohm range.
I chose 16 ohms because there is a possibility I will build a dual-15 version of the new speaker. 3 dB gain in efficiency, 6 dB gain in headroom, several dB drop in IM distortion, at the expense of a bigger (and heavier) cabinet. One driver might have a slightly different crossover than the other; if I build this version, I'd experiment with that.
As for tube amp vs transistor amp, this loudspeaker is optimized for tube amps: low-Q crossover and low-Q bass alignment that are not too sensitive to source impedance (damping factor). The design-center of the assumed source impedance for the loudspeaker is in the 0.5 to 1.5 ohm range.
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There are three versions of the speaker that I've considered (in the last couple of years): single 15" driver, two 15" drivers, or single driver with front-horn loading. The gotcha with the horn-loaded version is that horns that go down to 60 Hz are BIG ... and even bigger if you want the horn not to have any folds in it. (Folds make it very difficult to reach the 700 Hz crossover of the AH425 horn - and if the horn goes lower, say 500 Hz, it has to be bigger as well.)
So it's a question of dynamics: is 15" enough, or am I willing to live with a cabinet twice as big? I'm hoping to build my own prototype this year, so I'll find out.
I've listened to the first prototypes built in Dallas, and the dynamics from the Radian 745Neo & Azurahorn are stupendous. The direct-radiator 416 was impressive too, but not quite in the same league as the horn system. Plenty of old-school studio monitors have been built with twin 15" drivers, so that's definitely a consideration.
I've been down this single versus twin-driver road before, with the Ariel. I'd heard a predecessor that was built with a single 5.5" Vifa midbass, and it just didn't have enough dynamic range. Pretty-sounding, smooth and attractive, but very petite in character. The improvement going to twin drivers was really substantial, taking the speaker from the minimonitor category to a decent full-range speaker, and efficient enough to be used with moderate-power triode amplifiers (which was a design goal).
There's a reasonable possibility, based on the difference I heard with the Ariel, that the 6 dB jump in headroom would transform the speaker from a pretty good 15" direct-radiator to a system that is more comparable to a all-horn system ... but without the size and issues with horn-folding.
So it's a question of dynamics: is 15" enough, or am I willing to live with a cabinet twice as big? I'm hoping to build my own prototype this year, so I'll find out.
I've listened to the first prototypes built in Dallas, and the dynamics from the Radian 745Neo & Azurahorn are stupendous. The direct-radiator 416 was impressive too, but not quite in the same league as the horn system. Plenty of old-school studio monitors have been built with twin 15" drivers, so that's definitely a consideration.
I've been down this single versus twin-driver road before, with the Ariel. I'd heard a predecessor that was built with a single 5.5" Vifa midbass, and it just didn't have enough dynamic range. Pretty-sounding, smooth and attractive, but very petite in character. The improvement going to twin drivers was really substantial, taking the speaker from the minimonitor category to a decent full-range speaker, and efficient enough to be used with moderate-power triode amplifiers (which was a design goal).
There's a reasonable possibility, based on the difference I heard with the Ariel, that the 6 dB jump in headroom would transform the speaker from a pretty good 15" direct-radiator to a system that is more comparable to a all-horn system ... but without the size and issues with horn-folding.
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Another option would be the use of a short straight horn, similar to Dr. Edgar's 80Hz straight or Volvotreter's 70Hz conical. Since this type horn will only load down to the mid-bass frequencies, anything bellow will need to be augmented by sub(s). This could have the possible advantage of locating the subs at their optimum positions which most of the time is different from that which is optimum for the mains.
http://www.volvotreter.de/pics/conical_horn_setup_14.jpg
The GPA 515-16G would be a shoe-in for such a horn.
http://www.volvotreter.de/pics/conical_horn_setup_14.jpg
The GPA 515-16G would be a shoe-in for such a horn.
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Yes, just what I found. I made 160Hz Le Cleac'h horns for LM555 drivers crossed over at about 300hz and this works just great with my Vitavox K15/40 bass horns. (and can even get somthing close to time alignmernt with them hanging over the back). A pair of Onkens with TD15M drivers came up and have been setting these up for my son with 420 horns / JA6188B drivers . This seems a much more natural combination. Hard to imagine one could possibly want 2 x 15" drivers per side - already awesome in the bass compared to the bass horns. Why bother with bass horns at all? Just that what bass there is comes from nowhere - it makes music.
An externally hosted image should be here but it was not working when we last tested it.
martin
Forgot to add, that by horn loading the mid-bass driver it will definitely match the dynamics of the compression driver/Azura horn combo and it will also raise the sensitivity of the speaker to the 104-5 dB/w level. This might have the side benefit of simplifying the crossover high-pass for the RAAL tweeter. I am basing this (and I could be wrong) on the rising response of this ribbon, that happens to put it at around 104dB at 7KHz which if I remember correctly is the crossover point.
Well, Martin, I take your comments very seriously, since you're the first person in the world to have heard the AH425! I didn't get to actually hear the AH425's until I heard the prototypes in Dallas, which was more than a year later.
I find your bass horn vs TD15M comment especially interesting. You've been listening to your bass horn setup for many years; subjectively, how does it compare to the single TD15M in the Onken cabinet? I can imagine integration with the AH425 might be better with the TD15M, since the direct-radiator effortlessly goes up to 700 Hz. Time-alignment is also a lot easier; just move the AH425 back and forth a few inches.
But I'm surprised to hear a single TD15M might be better in the bass range than a well-engineered bass horn; bass horns can have truly stupendous bass when done right. My main reservation about them is the sheer size; they won't fit into my living room, which kind of limits my interest.
P.S. I found that optimum time-alignment of the AH425, at least with the crossovers I was using, was with the outer edge of the AH425 about 1/2" in front of the front panel of the bass cabinet, and about 2" to 3" of vertical clearance between the lower edge of the horn and the top of the bass cabinet. The imaging was surprisingly sensitive to front-back alignment; 1/4" movements were easily audible, as well as measurable.
One of the great virtues of a free-standing horn is the ease and precision of time-alignment. Also really spacious sound with very deep images ... frankly, the best I've heard from a high-efficiency system. You probably heard that too.
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The Onken cabinets came available when the guy who had them decided he wanted bass horns like mine (1/4 WL 50Hz T=60) for his GoTo system. We compared TD15M and also his GoTo SG38WN 15" drivers on the bass horns and in the Onken cabs. We both preferred the horns for natural presentation - the Onken cabs went deeper and had more power, but at the expense of some overhang. I had thought I would do him a swap (I wanted more bass and to follow along with this thread), but in the end I couldn't bring myself to let the horns go. The guy built himself some bass horns to my design, and I took the cabs for my son. Unfortunately not enough room to bring them here to play with the set up, and have not yet had the chance to do this at my son's place.
It's an interesting question if adding more direct radiator drivers to bring up the sensitivity to horn levels will emulate the bass horn control (that's a laugh - they measure dreadfully), while keeping the bandwidth advantage. And as you say, it is particularly the upward extension you need: you can get flat looking rta response with a 420 horn and 600Hz 12dB cross over - but subjectively I find the low mid range LM555 horn sounds a lot more richly satisfying. My friend with GoTo mid range drivers finds the same thing. Even Lowthers sound better (in low mids). Unfortunately bass horns just don't go high enough. Or low enough. But what they do do is very very good.
martin
Richard Heyser used to say that one quarter inch of time alignment was critical.
It is good to see someone else confirming this.
I just remembered that with a digital cross over (dbx driverack pa) the 420 horn actually worked very well with the bass horn, and I had it set up like this for a long time (mainly with a Lowther on a long 2.3m bass horn that also had good upward extension) - but when I abandoned multi amping, a simple 12dB best guess passive cross over and no time alignment really had problems. I guess a wideband mid range horn is a lot more fogiving and takes away the need to know what you are doing with cross over design.
martin
martin
