Keep the charts and measurements with you while you listen. 300Hz of sound is Max what they have. I don't care if there is any other driver who can measure better. Use two or five to compliment it. Make it N-th way speaker which actually performs instead of nostalgia dreck. I congratulate anybody who supposedly heard great Altec system. 515. 803A , Biflex -all great drivers, 416, 414 ? No. Not in application most are used serving as midrange in 2-way.
Since I'm building a similar type speaker, I've been scouring the weeds for a 15" driver to suit my needs too. GPA is out of the question due to cost, so I looked at and modeled (WinISD) drivers from Acoustic Elegance, Beyma, including the 15Mi100, 15P80Fen, and one other. B&C, Radian too. The FaitalPro 15PR400 stood out at least in the modeling, and a lot of people have really liked it over the years, so that's what I chose. F3 of 43Hz in a 135L vented box, and all the other measurements look great. A couple of those others looked super promising but hardly any of them will get below 50Hz. Crossing it with the Rosso 65CDN-T and considering using Troy Crowe's rear covers to get it to cross a bit lower, which should, I hope, help them integrate really well at the xover, hoping it will look good at 700Hz. I'd love to go lower, but The AH425 (shipped today!) really wants to cross closer to 800 according to Martin. I know this doesn't answer the IMD question, but just thought I'd weigh in on some of what I've found.
The last time I spoke with Great Plains Audio, they told me the only difference between the 416-Alnico and the 515-Alnico was the magnet size and strength. I asked about the cone and surround and they said it was exactly the same for both drivers.
Now, back in the vintage days of 1973 and earlier, the 515 could well have been different from the 416. The problem with the vintage, Altec-made drivers is they changed them every few years, so there is no "one" 515 or "one" 416.
Prior to 1973, before Theile and Small appeared in the AES Journal, nobody measured Qts, Vas, or Mms. If the production people wanted to "improve" the driver or cut costs, they just went ahead and did it. As a result, vintage 515's and 416's are all over the place, and not necessarily comparable to current GPA production.
I know this is true for Altec, but I'm pretty sure it's also true for vintage JBL, Jensen, Electro-Voice, or Stephens Tru-Sonic. Before T/S, there were vague theories and rules-of-thumb, but not the precise mathematical modeling T/S made possible.
One of the big breakthroughs in those AES Journal articles were accurate measurement techniques for the critical parameters of Qts, Mms, and Vas. In the first years of T/S, there was a frenzy of measuring every driver they could get their hands on, since no manufacturer specified these parameters ... they didn't know them themselves. It took many years for T/S parameters to be routinely published ... several manufacturers were quite secretive, and this was long before the Internet. You had to know somebody, or take a class and look at the data they had collected on their own.
In 1975, I took a class from Bob Ashley, then head of the AES, about the ins and outs of measuring T/S parameters, and saw a IBM fanfold printout of 12 different Altec 15-inch drivers, all with quite different parameters ... notably, with different Mms as well as different Qts. Altec was all over the place in 1975, and presumably earlier as well.
Now, back in the vintage days of 1973 and earlier, the 515 could well have been different from the 416. The problem with the vintage, Altec-made drivers is they changed them every few years, so there is no "one" 515 or "one" 416.
Prior to 1973, before Theile and Small appeared in the AES Journal, nobody measured Qts, Vas, or Mms. If the production people wanted to "improve" the driver or cut costs, they just went ahead and did it. As a result, vintage 515's and 416's are all over the place, and not necessarily comparable to current GPA production.
I know this is true for Altec, but I'm pretty sure it's also true for vintage JBL, Jensen, Electro-Voice, or Stephens Tru-Sonic. Before T/S, there were vague theories and rules-of-thumb, but not the precise mathematical modeling T/S made possible.
One of the big breakthroughs in those AES Journal articles were accurate measurement techniques for the critical parameters of Qts, Mms, and Vas. In the first years of T/S, there was a frenzy of measuring every driver they could get their hands on, since no manufacturer specified these parameters ... they didn't know them themselves. It took many years for T/S parameters to be routinely published ... several manufacturers were quite secretive, and this was long before the Internet. You had to know somebody, or take a class and look at the data they had collected on their own.
In 1975, I took a class from Bob Ashley, then head of the AES, about the ins and outs of measuring T/S parameters, and saw a IBM fanfold printout of 12 different Altec 15-inch drivers, all with quite different parameters ... notably, with different Mms as well as different Qts. Altec was all over the place in 1975, and presumably earlier as well.
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I should mention I bought the GPA 416 Alnicos several years ago ... in fact, the serial numbers are 0003 and 0004, the first they produced (the first pair were set aside for in-house reference).
The price has gone up threefold (!) since then, so I appreciate the mention of the Beyma 15MI100 and FaitalPro 15PR400 drivers. Note the outer frame and bolt circle diameter are slightly smaller than the Altec/GPA 416/515, because of course they are. These things are never directly interchangeable.
The price has gone up threefold (!) since then, so I appreciate the mention of the Beyma 15MI100 and FaitalPro 15PR400 drivers. Note the outer frame and bolt circle diameter are slightly smaller than the Altec/GPA 416/515, because of course they are. These things are never directly interchangeable.
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I only commented on vintage variants. I think interest in Altec picked up significantly after Shindo became an almost cult object in US. Its worth to notice that Shindo would not use GPA variants and Shindo importers insisted many times the speakers sound
"nothing like Altecs" They better not with those prices and appalling sound of original Altec speakers. But looking at pictures of Altec club it mostly contains gentlemen in 70-90 age bracket. Happy to bring back a glance of good old days of their youth. Nothing wrong with that. My own vintage pick would be ElectroVoice. Light years ahead of Altec
"nothing like Altecs" They better not with those prices and appalling sound of original Altec speakers. But looking at pictures of Altec club it mostly contains gentlemen in 70-90 age bracket. Happy to bring back a glance of good old days of their youth. Nothing wrong with that. My own vintage pick would be ElectroVoice. Light years ahead of Altec
No interest in Shindo at all. My interest in Altec dates from the late Nineties, in combination with my push-pull triode DHT amplifiers. These are the Amity, the Karna's, and now the Blackbird amplifiers, with outputs in the 16 to 25 watt range.
The old-school Altec sectoral horns are not of interest either. It's the 15" drivers, with their underhung voice coils, and near-saturated gaps, that have my interest. That setup is quite unusual these days, and provides very linear performance ... as long as the VC stays in the gap. This was confirmed by Joseph Crowe's IM measurements, something I did not expect to see. Drivers with underhung voice coils definitely sound different, especially in the large-format 15" size.
I admit if Wolf von Langa was selling 15" drivers, I'd also be interested, but I'd expect the price to be pretty frightening, perhaps making GPA Alnico look reasonable in comparison.
Working with Bjorn Kolbrek (on the AH425 Azurahorn) has showed me that horn design has come a very long way from the horns of the Sixties and Seventies. Compression drivers are better too.
The old-school Altec sectoral horns are not of interest either. It's the 15" drivers, with their underhung voice coils, and near-saturated gaps, that have my interest. That setup is quite unusual these days, and provides very linear performance ... as long as the VC stays in the gap. This was confirmed by Joseph Crowe's IM measurements, something I did not expect to see. Drivers with underhung voice coils definitely sound different, especially in the large-format 15" size.
I admit if Wolf von Langa was selling 15" drivers, I'd also be interested, but I'd expect the price to be pretty frightening, perhaps making GPA Alnico look reasonable in comparison.
Working with Bjorn Kolbrek (on the AH425 Azurahorn) has showed me that horn design has come a very long way from the horns of the Sixties and Seventies. Compression drivers are better too.
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You may remember the time when we communicated within a private forum I asked Wolf for you the same question and he answered that it is up to you to contact him for any request.
The advantage of FC drivers is that you have many drivers only by adjusting the current but it burns away a lot of heat.
I have found some older measurements of the A1500 simply varying the FC current 2.0A, 2.5A, 3.0A, 3.4A (no damping in a large open baffle wave guide).
With less current = less efficiency there is a more even fr. If you use a stronger motor then you gain level in the midrange but loose level in the lower registers.
With less current = less efficiency there is a more even fr. If you use a stronger motor then you gain level in the midrange but loose level in the lower registers.
some more data:
With 1500mA you get a low efficient open baffle woofer and with 3000mA a higher efficient woofer for a closed box or bass reflex.
Anyway if you prefer an underhung vc then why not look AE woofers? The LO series has been named after you? I have ordered a HE version of the LO15 perfect for tube amps with a little bit stronger motor and slightly higher qts. And the AE woofers have extremely low inductance. Disadvantage, that prices increased drastically a few weeks ago.
With 1500mA you get a low efficient open baffle woofer and with 3000mA a higher efficient woofer for a closed box or bass reflex.
Anyway if you prefer an underhung vc then why not look AE woofers? The LO series has been named after you? I have ordered a HE version of the LO15 perfect for tube amps with a little bit stronger motor and slightly higher qts. And the AE woofers have extremely low inductance. Disadvantage, that prices increased drastically a few weeks ago.
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Yes , that's what I 've got on microphone too. Nice flat response well beyond 1kHz. Unfortunately for whatever reason you can't hear it. At least I couldn't. There is no low mid articulation and a low end isn't really well controlled either A lump of warm midbass is all one gets. With AH425 realistically useful from 800Hz I doubt anyone used to smaller well behaved cones can accept this sort of compromise. I often wonder about "converts" like late Art Dudley who were reasonably happy with pretty much stock Altec Valencia. But seeing Klipsch classic series enjoying a big comeback for what just yesterday was considered a Redneck Riviera speaker range maybe it's not surprising after all.
I don't have any recommendations and since you already have GPA 416 and you heard Gary's implementation and liked it good enough there is no reason to look for anything else. With your experience I'm sure you can assess particular driver pretty fast without much evolved effort. I only commented on vintage application of that driver and my own superficial efforts to assess it. and some other amateur's designs You must know that hardly anybody in that business is honest with opinions. In the room everybody loves your "sound" and drinks your wine . Once they leave it's a different story. I think you have done your service to DIY community three fold already and you're going to a DIY heaven with your shoes on . No obligation to contribute further with a design to please masses. Contact von Langa or use your well deserved reputation to acquire purely unobtainum spectacular drivers only a narrow insiders club knows and make your dream speaker. For Yourself. The rest can eat their hearts
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The 416 is an excellent driver……but man, is it expensive!……..i become a bit of a pragmatist when we’re talking over $400 for a single drive unit of any type………..which leaves me with the Faital Pro 15PR400……..at less than half the cost of the 416. Is it a ‘better’ performer?….sure………is it more than twice the improvement?………..i can’t relate to that equivalency when it comes to music……….the song itself is still the greatest limiting factor. if the 416’s were $500, I’d be on the waiting list for a pair yesterday.
And then there’s the JBL2260…….there’s something about the midbass dynamics that IMO, NO DRIVER can compare to. I’d not dare cross them any higher than 600hz for critical listening use though…….and I would still whole heartedly recommend them for any modern multi way design.
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" Use TAD 4001s and call it a high end day"
What a funny times we're living in . Few years back everybody was dropping them like hot potatoes since they were harsh , in yer face , no depth to the image , unusable for any but TH4001 horn ...
I had no idea GPA 416 are $3000 a pair now. I bet they sound so much better to most people already ...
What a funny times we're living in . Few years back everybody was dropping them like hot potatoes since they were harsh , in yer face , no depth to the image , unusable for any but TH4001 horn ...
I had no idea GPA 416 are $3000 a pair now. I bet they sound so much better to most people already ...
Yeah, there's been some GPA 416/515 wannabe spec wise pop up from time to time, but don't recall any with a close enough clone of its curvilinear diaphragm that makes its trademark extended HF response with 'heart attack fast' transients and without it they're just 'pretenders to the throne'. 
Cough ..cough ..Yeah, there's been some GPA 416/515 wannabe spec wise pop up from time to time, but don't recall any with a close enough clone of its curvilinear diaphragm that makes its trademark extended HF response with 'heart attack fast' transients and without it they're just 'pretenders to the throne'.