Have to check my measurements, but as far as I remember the GPA couldn 't reach more than 12K, and it was ugly after 10K.
Mind you the measurement was from listening position about 4 meters away with both channels.
As there is no attenuation on the super tweeter, I am limited my it' s sensitivity.
Mind you the measurement was from listening position about 4 meters away with both channels.
As there is no attenuation on the super tweeter, I am limited my it' s sensitivity.
Dual 15" woofers or supertweeters; it's not an either/or choice. A system like this isn't built to price point: it costs what it costs, and you stop when you're satisfied with the sound. The high-end commercial equivalents are already at the $60,000/pair price point, or higher.
The choice of single versus dual versus horn-loaded woofers mostly comes down to available space. The smaller the room, the less you need the headroom, and the larger the room, the more acoustic watts you'd like to fill the space. A New York or Hong Kong studio apartment is probably too small for any of these variants. Multiple or horn-loaded woofers would be fine for a 500-seat movie theater; that's what Altec sold for neighborhood theaters back in the 1950's, and movies were plenty loud back then. If I had the space for a pair of 9-cubic-foot bass cabinets, I'd certainly use dual GPA 416B-Alnico bass drivers (mostly likely in a side-by-side configuration).
Vgeorge, that's a nice system, and a well-worked-out crossover. You have the satisfaction of knowing it'll sound better than just about anything at an audio show - not only that, the non-audiophile recordings sound great! You may have already found that movies from the 1950's and 1960's have a "rightness" on Altec speakers - not surprising, since that's what was used during the mixdown and audience previews.
The choice of single versus dual versus horn-loaded woofers mostly comes down to available space. The smaller the room, the less you need the headroom, and the larger the room, the more acoustic watts you'd like to fill the space. A New York or Hong Kong studio apartment is probably too small for any of these variants. Multiple or horn-loaded woofers would be fine for a 500-seat movie theater; that's what Altec sold for neighborhood theaters back in the 1950's, and movies were plenty loud back then. If I had the space for a pair of 9-cubic-foot bass cabinets, I'd certainly use dual GPA 416B-Alnico bass drivers (mostly likely in a side-by-side configuration).
Vgeorge, that's a nice system, and a well-worked-out crossover. You have the satisfaction of knowing it'll sound better than just about anything at an audio show - not only that, the non-audiophile recordings sound great! You may have already found that movies from the 1950's and 1960's have a "rightness" on Altec speakers - not surprising, since that's what was used during the mixdown and audience previews.
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Thanks for the graphs, Lynn. They do look great and are hard to argue with. No EQ needed there. Yes, there is a certain openness and naturalness to large format drivers that is seductive. Like electrostatics, but with better dynamics and imaging (on the right horn). Sounds like real music.
I personally don't care about content above 15K - I can't hear it in music. Cut much lower than that, and strings start to lose their warmth.
I personally don't care about content above 15K - I can't hear it in music. Cut much lower than that, and strings start to lose their warmth.
Lynn
I'm considering travelling to RMAF to audition the LTO sound. Since that's the main reason for attending, it would be nice to know the likelihood of the LTO being there for demo. Would you say there's a likelihood of 80 or 90% at this point?
Understanding full well that there is always a chance for a last minute LTO cancellation at the show, airplane flights might be cheaper if purchased sooner rather than later.
I'm considering travelling to RMAF to audition the LTO sound. Since that's the main reason for attending, it would be nice to know the likelihood of the LTO being there for demo. Would you say there's a likelihood of 80 or 90% at this point?
Understanding full well that there is always a chance for a last minute LTO cancellation at the show, airplane flights might be cheaper if purchased sooner rather than later.
The latest information from my collaborator is that he will NOT be exhibiting at the RMAF show. My own loudspeakers (I may call them the LTO Apollo) will probably take six months to build - some time next year, in other words.
If you're going to spend all that money for travel, how about a sunny tropical vacation to audition Vgeorge's system?
Vgeorge, now that I've got your attention, why not consider a 4th-order highpass for the AH425 and a 3rd-order lowpass for the woofers? I've auditioned both 3rd and 4th-order highpass crossovers in the vicinity of 650~720 Hz, and I can assure you the sound is sweeter, more natural, and more relaxed with the 4th-order highpass combined with a 3rd-order lowpass, as counterintuitive as this may seem.
As mentioned earlier, these are low-Q networks that are transitional between Bessel and Linkwitz-Riley 4th-order, and the same low-Q approach for the woofer. You'll need to move the horn back a little more, but only by an inch or so.
If you're going to spend all that money for travel, how about a sunny tropical vacation to audition Vgeorge's system?
Vgeorge, now that I've got your attention, why not consider a 4th-order highpass for the AH425 and a 3rd-order lowpass for the woofers? I've auditioned both 3rd and 4th-order highpass crossovers in the vicinity of 650~720 Hz, and I can assure you the sound is sweeter, more natural, and more relaxed with the 4th-order highpass combined with a 3rd-order lowpass, as counterintuitive as this may seem.
As mentioned earlier, these are low-Q networks that are transitional between Bessel and Linkwitz-Riley 4th-order, and the same low-Q approach for the woofer. You'll need to move the horn back a little more, but only by an inch or so.
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Thanks Lynn.
After I posted I also thought that for the cost of travel, I could buy some of the parts.
This project looks magical enough that it may make sense to build it twice; the first time with any ol' 4.5 - 6.5 ft3 cabinet and then a second time to exact specs once the specs are finally released.
So I'm thinking, why not buy all of the parts and get started?
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I would certainly keep the door open to building the bass cabinets twice; that's pretty much I've had to do with every speaker I've designed. The first demonstrates proof-of-concept, but usually has several things wrong with the sound. The second cabinet is an opportunity to get it right, and improve the visuals as well.
What I've learned from the first prototypes is a minimum cabinet width of 25", having the centerline of the horn at listening height or a few inches above (this is about 40" for me), and a couple inches of air-space between the top of the bass cabinet and the bottom edge of the horn.
The vent on the prototype was a full-height vent going up the side of the cabinet, similar to half of an Onken or Planet10's Fonkens, and I've decided I'll get deeper and a more felt bass by moving the vent to the floor, similar to the Ariels. The best subjective box tuning was between 30 and 35 Hz, a bit lower than standard T/S alignments for the Altec/GPA 416B Alnico.
Just between you, me, and the lamppost, I think it's possible the latest GPA 416B Alnico might have a bit more powerful magnet than the ceramic version of the 416, since it has about 1~2 dB more efficiency and the Qts is a bit lower than the old-school 416 spec. Since the 416 and 515 share the same cone, surround, and spider, that takes the current-model Alnico 416 part of the way towards a traditional Altec 515, which is just fine by me.
For the real efficiency nuts who intend to horn-load the bass driver, yes, GPA also makes a true-blue Alnico 515. This GPA driver has the biggest and most powerful magnet of all, and the highest efficiency (I'm guessing 2~3 dB more than the Alnico 416).
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I have done direct comparisons between the Beyma TPL-150 , and LeCleac'h Fc 400hz with Vitavox S2 driver, in the frequency range above 1,2khz. ( which should compare and be quite close to LeCleac'h 320hz horns with Altec or Radian drivers ) The Beyma has its strengts not specially in the treble, but in the higher midrange , above 1,2khz. Result : i sold the S2, and kept the Beyma, which sounds much more natural, wonderfully neutral, with a correctness in timbre, specially of voices, which is phenomenal. Taking off the cap behind, and using it bipol, has brought more holographic 3d dimensionality into the picture. Dynamics isn't lacking either, with 103db/wm ( with wave guide ) , it integrates well with the other horn channels. It really transmits the illusion of a big orchestra, ore a singer being right in front. Compared, voices with S2/La horns were sounding colored, and like squeezed out of a tube. Interestingly, i did found out about these characteristics only after making direct comparisons. Before , i was sure i was having a great result and correctness of timbre as well. The listening experience is confirmed by the technical aspect of air motion transformer technology, which permits lower distortion than any compression driver , and so more fidelity of reproduction. This paper explains, why the Beyma sounds so good.
Focus on: Beyma
at this thread, information i have collected about the Beyma :
Beyma Tpl-150 - Audio Voice Acoustics
many are discovering the superiority of this topology, and integrating the Beyma in their horn setups , like Tuyen :
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Angelo
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Hello,
Everybody should know that the name "La horns" was given to the "Le Cléac'h horns" by Romy-the-Cat...
Angelo, I yet told this to you, if your S2 sound coloured with the 400Hz Le Cléac'h horn it is either your building of the horn was not correct or the S2 has some problem (this is often the case with S2).
When Lynn says the AH425 horn is not coloured and sounds like an electrostatics, there is very few reason to not believe him, he has proven to have a listening ability that very few have.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Everybody should know that the name "La horns" was given to the "Le Cléac'h horns" by Romy-the-Cat...
Angelo, I yet told this to you, if your S2 sound coloured with the 400Hz Le Cléac'h horn it is either your building of the horn was not correct or the S2 has some problem (this is often the case with S2).
When Lynn says the AH425 horn is not coloured and sounds like an electrostatics, there is very few reason to not believe him, he has proven to have a listening ability that very few have.
Best regards from Paris, France
Jean-Michel Le Cléac'h
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I found a cabinet shape suitable to Lynn's description.
I also found that getting the driver as-close-to the top of the cabinet as possible eliminated half of the internal resonance ripple that occurs around 6-900 Hz. Sloping the top of the cabinet front to back affects that.
The cabinet above is for a 12" driver. My next effort will be for a 15" driver. I'm putting a "JBL 2236" together per GordonW's recipe over on AK
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