Altec 515Cs (Great Plains Audio) - 16 ohm ($1,675 shipped to CONUS)
New in box Altec 515C drivers from Great Plains Audio. These are the 3rd and 4th drivers built by Bill.- The drivers have been stored in a dry, non-smoking Colorado home and have never been installed. We "swept" them from 20 Hz to 1KHz to ensure there's no voice-coil rub.
- The slight scuffing on the label of s/n 1113-0202 is how the driver was delivered.
- These will be double-boxed (and of course, enclosed in plastic) to ensure safe shipping
The Azzolinas have sold, so I removed them from this post.
Thanks for looking!
Thom (more photos on the web page above, but scroll down for a few)
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Hi,
Has your experience with these drivers been consistent with GPA's published TS parameters? I'm asking primarily because the old Altec 515s seem not well designed for a moderate reflex box, while the GPA specs have a much higher Q and a lower vas than GPAs published specs on the 416.
In the end, these model nicely in <6cu ft. That's big, but not the "horns only" or "10-12cu ft one hears about with the older 515s.
Very interested in these and why I'm asking, but really thinking of using them in a "smaller" box.
Best
Max
Has your experience with these drivers been consistent with GPA's published TS parameters? I'm asking primarily because the old Altec 515s seem not well designed for a moderate reflex box, while the GPA specs have a much higher Q and a lower vas than GPAs published specs on the 416.
In the end, these model nicely in <6cu ft. That's big, but not the "horns only" or "10-12cu ft one hears about with the older 515s.
Very interested in these and why I'm asking, but really thinking of using them in a "smaller" box.
Best
Max
Hi Max,
I'm not the fellow to answer your question in a meaningful way. I'll ping Lynn and have him chime in on this thread. Thanks for checking in!
... Thom
HI Max, I'm the owner of the Alnico 515's, which were once-upon-a-time part of the "Beyond the Ariel" project. My idea was to use 416's in a larger vented box (7~8 cubic feet) with 515's in a compact (2.5 cubic feet) closed box sitting directly above the vented boxes. Since both 416's and 515's use the same cone these days, there would be no sonic conflict between the two, and they could specialize in different parts of the spectrum with little or no crossover between them. That concept would still work, by the way, and would have efficiency in the bass horn range without the huge size.
Back in the old Altec days (up to the mid-Seventies) Altec would change the bass drivers without notification to the user community. So there is no "one" 515 or 416, but many. Once Altec started using T/S methodologies in the mid-Seventies, this stabilized somewhat, but then repeated corporate takeovers destroyed the company in the Eighties and Nineties, leading to the sale of the Altec name and branding to a Taiwanese company in the Nineties. The Oklahoma City repair station stayed in business, reconing and recharging old drivers, and then, using the original tooling and staff, went into production. The rest, as they say, is history.
I had been pestering GPA to build drivers with Alnico magnets for more than ten years, and they finally agreed, which is why the serial numbers are #3 and #4 (GPA reserved #1 and #2 for themselves). The serial numbers on my 416's are the same. Unlike the 1950's and 1960's versions, the cones of the modern 515's and 416's are the same, the only difference is the magnet size ... which is huge on the 515's. So the modern T/S specs are wildly different from the measured specs on truly vintage 515's, but again, if you collect 20 different vintage 515's, they'll all be different unless they were manufactured at the same time. I believe the cones of the vintage ones were as light as 55 grams, while the modern ones are 70+ grams, which is still light by modern (JBL 2256H) prosound standards.
When the first prototypes were auditioned in Dallas some time back, I was startled to find the JBL 2235H and the Alnico 416's were totally different in sound, and mostly in the upper bass and lower midrange. This shouldn't happen; that's the flat response region of the driver, well away from breakups, and distortion is very low in a well-designed 15-incher. But it was very audible and obvious. So I joined the Alnico/Altec camp at that point. Fortunately, GPA continues to make Alnico magnet drivers, very similar to #3 and #4 that Thom and I am selling here.
As for T/S specs, yes, I would trust the data GPA is publishing. And they stand behind their products, so if anything goes wrong, they will recone them to current-production spec, so they driver will be identical to what rolled off the line a week ago. As for demagnetization of the Alnico magnets, they've been sitting in a box in my climate-controlled basement here in very dry Colorado for the last ten years. To the best of my knowledge, demagnetization requires a sharp mechanical shock or electrical overdrive for several minutes, neither of which has occurred to them. I doubt the charge of the magnets dissipates over ten years, otherwise truly vintage drivers (50+ years) wouldn't work at all. Worst case scenario, they might need to be re-magnetized by GPA, but I doubt they'd fade that much in ten years time. But GPA is there if you need them.
Do they have collector value? Well, maybe. They are the first Alnico drivers made by GPA/Altec in many decades, and Altec fans have accepted them as the "real thing". They are not made in South Korea or China, but in Oklahoma City by Altec staff on Altec tooling. So they are not reproductions, but re-issues.
Technically, what separates the 416's and 515's from modern prosound drivers are magnetic gaps close to saturation (like a Lowther or AER), underhung voice coils (very unusual in the prosound world), lighter cones, and the distinctive damped cloth surrounds. All of which makes them unsuitable for 500-watt amplifiers in movie theaters ... which is where the JBL 2235 comes in.
Back in the old Altec days (up to the mid-Seventies) Altec would change the bass drivers without notification to the user community. So there is no "one" 515 or 416, but many. Once Altec started using T/S methodologies in the mid-Seventies, this stabilized somewhat, but then repeated corporate takeovers destroyed the company in the Eighties and Nineties, leading to the sale of the Altec name and branding to a Taiwanese company in the Nineties. The Oklahoma City repair station stayed in business, reconing and recharging old drivers, and then, using the original tooling and staff, went into production. The rest, as they say, is history.
I had been pestering GPA to build drivers with Alnico magnets for more than ten years, and they finally agreed, which is why the serial numbers are #3 and #4 (GPA reserved #1 and #2 for themselves). The serial numbers on my 416's are the same. Unlike the 1950's and 1960's versions, the cones of the modern 515's and 416's are the same, the only difference is the magnet size ... which is huge on the 515's. So the modern T/S specs are wildly different from the measured specs on truly vintage 515's, but again, if you collect 20 different vintage 515's, they'll all be different unless they were manufactured at the same time. I believe the cones of the vintage ones were as light as 55 grams, while the modern ones are 70+ grams, which is still light by modern (JBL 2256H) prosound standards.
When the first prototypes were auditioned in Dallas some time back, I was startled to find the JBL 2235H and the Alnico 416's were totally different in sound, and mostly in the upper bass and lower midrange. This shouldn't happen; that's the flat response region of the driver, well away from breakups, and distortion is very low in a well-designed 15-incher. But it was very audible and obvious. So I joined the Alnico/Altec camp at that point. Fortunately, GPA continues to make Alnico magnet drivers, very similar to #3 and #4 that Thom and I am selling here.
As for T/S specs, yes, I would trust the data GPA is publishing. And they stand behind their products, so if anything goes wrong, they will recone them to current-production spec, so they driver will be identical to what rolled off the line a week ago. As for demagnetization of the Alnico magnets, they've been sitting in a box in my climate-controlled basement here in very dry Colorado for the last ten years. To the best of my knowledge, demagnetization requires a sharp mechanical shock or electrical overdrive for several minutes, neither of which has occurred to them. I doubt the charge of the magnets dissipates over ten years, otherwise truly vintage drivers (50+ years) wouldn't work at all. Worst case scenario, they might need to be re-magnetized by GPA, but I doubt they'd fade that much in ten years time. But GPA is there if you need them.
Do they have collector value? Well, maybe. They are the first Alnico drivers made by GPA/Altec in many decades, and Altec fans have accepted them as the "real thing". They are not made in South Korea or China, but in Oklahoma City by Altec staff on Altec tooling. So they are not reproductions, but re-issues.
Technically, what separates the 416's and 515's from modern prosound drivers are magnetic gaps close to saturation (like a Lowther or AER), underhung voice coils (very unusual in the prosound world), lighter cones, and the distinctive damped cloth surrounds. All of which makes them unsuitable for 500-watt amplifiers in movie theaters ... which is where the JBL 2235 comes in.
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Thanks Lynn. This is very helpful. I have a pair of 120L boxes cut for 15" woofers. I currently have older Jensens (P15LL) in there and wanted to try something current production. If I use the TS parameters provided by GPA, I get some numbers that I like, namely an F3 in the mid sixties and more importantly, an F10 of 35 hz. With my poorly damped SET and placement right up against the wall where this system lives, that sounds good to me as long as speakers are sensitive enough to "come alive" with a couple of watts. When I've tried this same recipe with newer JBLs, it doesn't work.
The cut out of these is a bit bigger than the old Jensens, so let me measure in the AM...
Cheers
The cut out of these is a bit bigger than the old Jensens, so let me measure in the AM...
Cheers
Hi Max,
I suspect you've been through the Great Plains site, but since it's a bit difficult to navigate, I'm attaching the 515C datasheet for you. I've verified the physical dimensions.
I've messed around with both front and rear mounting, and if you have any questions about dimensions and such, let me know. I'm guessing you'll have to get the router out to enlarge the cutout.
... Thom
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Hi Max! Thom has the GPA 515 drivers over at his place (he's a nearby neighbor and fellow audio enthusiast) and is a whiz at shipping and packaging.
Your intuitions on cabinet size are correct. Zero-feedback tube amps typically have a Zout around 2 ohms, or put differently, a damping factor of 4. This will raise the Qes and Qts quite a lot, since driver damping is mostly supplied by the amplifier, not the spider or surround. The 2nd-order LF closed-box rolloff is gentle enough that room lift will offset much of the rolloff of the bass system, going lower than you might expect. An in-room F10 of 35Hz, with a tube amp, sounds perfectly reasonable.
By contrast, bass horns have very sharp cutoffs, and a bass horn with a true 40 Hz cutoff is insanely large. And vented cabinets drop off 4th-order, so they are mostly gone 10 to 15 Hz below the intended box tuning (Fb). A minor advantage of a closed box is (much) better control of VLF excursion, which is very desirable for drivers with underhung voice coils. (The linear travel region is rather short with underhung voice coils.)
VLF excursion is mostly a problem when LP phono playback is combined with a vented-box speaker, with undamped tone arm-cartridge resonance typically in the 8 Hz region. That's when you see woofer cones bouncing. 8 Hz tone arm resonances can also result in temporary core saturation of the output transformers. Not a problem for digital, of course.
(A quick walkthrough of VLF excitation when playing records. Record warps, mostly in the vertical plane, shock-excite the 6 to 8 Hz arm-cartridge resonance, which can be as large as 8 to 10 dB in magnitude. If not filtered out in the phono preamp, this 6 to 8 Hz pulse train is amplified right through the electronics chain, challenging the output transformers with out-of-passband energy. Vented loudspeakers have very low power-handling below the box tuning frequency, similar to the driver hanging in free air. The 6 to 8 Hz shock excitation is not directly audible, since vertical record warps play back as out-of-phase at very low frequencies, so mostly cancelled at the listening position. But the resulting IM distortion from the bass driver is NOT cancelled.)
As for subwoofers, if desired, it would have to be set very low, with a lowpass filter no higher than 40 Hz, otherwise too much overlap will occur. The effective passband with a SW would be 20 to 40 Hz at most.
Your intuitions on cabinet size are correct. Zero-feedback tube amps typically have a Zout around 2 ohms, or put differently, a damping factor of 4. This will raise the Qes and Qts quite a lot, since driver damping is mostly supplied by the amplifier, not the spider or surround. The 2nd-order LF closed-box rolloff is gentle enough that room lift will offset much of the rolloff of the bass system, going lower than you might expect. An in-room F10 of 35Hz, with a tube amp, sounds perfectly reasonable.
By contrast, bass horns have very sharp cutoffs, and a bass horn with a true 40 Hz cutoff is insanely large. And vented cabinets drop off 4th-order, so they are mostly gone 10 to 15 Hz below the intended box tuning (Fb). A minor advantage of a closed box is (much) better control of VLF excursion, which is very desirable for drivers with underhung voice coils. (The linear travel region is rather short with underhung voice coils.)
VLF excursion is mostly a problem when LP phono playback is combined with a vented-box speaker, with undamped tone arm-cartridge resonance typically in the 8 Hz region. That's when you see woofer cones bouncing. 8 Hz tone arm resonances can also result in temporary core saturation of the output transformers. Not a problem for digital, of course.
(A quick walkthrough of VLF excitation when playing records. Record warps, mostly in the vertical plane, shock-excite the 6 to 8 Hz arm-cartridge resonance, which can be as large as 8 to 10 dB in magnitude. If not filtered out in the phono preamp, this 6 to 8 Hz pulse train is amplified right through the electronics chain, challenging the output transformers with out-of-passband energy. Vented loudspeakers have very low power-handling below the box tuning frequency, similar to the driver hanging in free air. The 6 to 8 Hz shock excitation is not directly audible, since vertical record warps play back as out-of-phase at very low frequencies, so mostly cancelled at the listening position. But the resulting IM distortion from the bass driver is NOT cancelled.)
As for subwoofers, if desired, it would have to be set very low, with a lowpass filter no higher than 40 Hz, otherwise too much overlap will occur. The effective passband with a SW would be 20 to 40 Hz at most.
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Thanks guys--my cut out is 13 3/4" and apparently these require 14 1/8", so I'm 3/8" too small.
Not too big of a deal as there's a big accordion surround on the Altec and not on the Jensen; as long as the gasket is big enough, maybe I don't need to do anything.
A bigger issue will be the size of the frame and the front to back size of the driver.
Will open and measure. Appreciate all your insights and help.
Not too big of a deal as there's a big accordion surround on the Altec and not on the Jensen; as long as the gasket is big enough, maybe I don't need to do anything.
A bigger issue will be the size of the frame and the front to back size of the driver.
Will open and measure. Appreciate all your insights and help.
Hi Max,
Unless you have some intricate cabinetry that's not obvious from the outside of the box, the depth of the 515Cs when rear mounted is 7". I've validated all of the measurements against the spec sheet. The driver frame is also as advertised: 16" diameter.
As far as the mounting bolts, depending on how accurately you drilled the mounting holes for your drivers, you might get away with the same holes.
The Altec mounting holes are oval-shaped (3/4" long), so you wouuld be able to mount the drivers with 1/4" bolts on a bolt circle anywhere from 14-1/4" to 15-3/4".
... Thom