816 advice please

Hi all you good people, I'm new to your site and although a lot of the technology and some terminology goes over my head I feel that you put good sound first and foremost.

Now I hope I'm doing this right but I would like some advice.

I got bitten by the altec bug after a visit to the repair man with, what I realise now, a substandard tube amp. He has homemade 816s with big tractic horns and tiny tweeters and it all plays effortlessy and wonderful. So I'm going to make some for myself.

I can get a pair of altec 3156s and my question is, would this be a bad idea? I know that 515 Gs are what most would recommend and with some patience I could find a pair.
But are the 3156s totally ruled out?
For the horns my friend the repairman suggests 288-16G. The crossover talk goes above my head and thats all in his hands. Happily I'm saved from venturing further into the hifi male-cow-excrement swamp and looking forward to real music listening.

Yours
Kieran C

Oh yes, one more question, what is the radius on the curved walls of the 816 opening?

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Oh yes, one more question, what is the radius on the curved walls of the 816 opening?

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I made mine with the same 30-31/32 inch radius as the 828 and 817 flares. I've never seen a drawing that was fully dimensioned for the 816, so i don't know if this is right or wrong, but it worked for me.

AN11 is here: CPC Production Services - Altec Lansing

And says yer right....

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Originally Posted by kieran casey

... Happily I'm saved from venturing further into the hifi male-cow-excrement swamp and looking forward to real music listening...

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ROFLMAO!

You are, however, teetering on the brink of said swamp. ;)

Welcome! You'll fit in fine here.

Don't know about 3156s in 816s, but it seems like I remember someone saying they'd done it. Be patient, someone here knows.

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Originally Posted by bowtie427ss

I made mine with the same 30-31/32 inch radius as the 828 and 817 flares. I've never seen a drawing that was fully dimensioned for the 816, so i don't know if this is right or wrong, but it worked for me.

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I've never seriously considered building any, so I never paid much attention to that aspect of the plans..... from what I've read on horns they're conical, parabolic, hyperbolic, or quadratic. I didn't know Altec used a simple radius, which I assume approximates a section of a parabola. I just looked at the plans for the 825, and sure enough it's 30& 31/32..... seems like kind of an odd measurement to me. The sheet for the 211 doesn't specify at all, and the 815 plans don't give a radius, but rather a width every 4 inches. Unfortunetly, I don't seem to have 816 plans...... lost them during a hard drive mishap about 2 months ago :-(

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Originally Posted by Audio_by_Goodwill

... from what I've read on horns they're conical, parabolic, hyperbolic, or quadratic...

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...or exponential, which is what most pre-MR Altecs were at least an approximation of. Expos exhibit a doubling of cross section area at regular intervals of length, the "speed" of which is determined by the flare rate. Since both 828s and 816s share the same horn flares, but have different CSAs due to differing "flat" sides (parallel vs non), either one or both may not be "true" expos.

Still, it stands to reason that a radius could be exponential, depending on the radius' dimensions and the flare rate.

Disclaimer; consider this explanation comes from a guy that told his algebra teacher no one cared what x equaled...

i just set a sound guy up with some 828's loaded with 3156's... they rock! if you put your hand on the cab, it feels like its going to expload. lots of pressure. but the 816 has less volume and much smaller venting, of course. probably not the best driver but they work. if you look up the 3156 in the search area of this forumn you'll see thats was originally used as a br cabinet woofer. as to the actually why it might work in a mildly horn loaded cabinet, ill leave for someone else to explain

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Originally Posted by bfish

...or exponential....

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THAT's the one I couldn't think of...... I knew there should have been 4 before I threw on the more modern quadratic!

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which is what most pre-MR Altecs were at least an approximation of. Expos exhibit a doubling of cross section area at regular intervals of length, the "speed" of which is determined by the flare rate. Since both 828s and 816s share the same horn flares, but have different CSAs due to differing "flat" sides (parallel vs non), either one or both may not be "true" expos.

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One of theses days I hope to understand horns well enough to build one...... classical horn theory any way. I always knew the horizontal (when looking at something like an 825) was important, but what about the vertical..... which is of course needed to have an area.

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Still, it stands to reason that a radius could be exponential, depending on the radius' dimensions and the flare rate.

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My thoughts, having had some higher math, is that a constant radius is probably a good approximation over a limited distance....... for example, if you look at a small enough piece of a curve it can be approximated as a straight line.

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Disclaimer; consider this explanation comes from a guy that told his algebra teacher no one cared what x equaled...

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That could have been the result of several things...... Firstly, being the way math is taught.... too abstract...... or more recently too application based (called integrated math). There really needs to be a balance. Secondly, not all teachers are created equal. Thirdly, I suspect you felt there were fish to be caught, and time was wasting :-)

The 515 is really the best for horn loaded Altec Cabinets especially the new 515 by GPA. Although the 416 was used also . Relying on Thiele Small Parameters. The 3156 was designed to be in the 8156 cabinet; it's a resonator speaker.

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forgot to add..my 816's are loaded with 418-8h mi speakers

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if you put your hand on the cab, it feels like its going to expload.

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That's "lost" energy that went into the speaker system as an electrical signal from the amplifier, but isn't exiting as sound pressure. This is where the 825/828 benefits significantly from sturdy internal bracing. What you're feeling with your hand is input power being lost in the form of kinetic energy and heat, in a perfect world you should be feeling that energy on your chest and pant legs 20 or 30 feet out in front.

Just my .02.........................

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Originally Posted by bfish

Since both 828s and 816s share the same horn flares, but have different CSAs due to differing "flat" sides (parallel vs non), either one or both may not be "true" expos.

Still, it stands to reason that a radius could be exponential, depending on the radius' dimensions and the flare rate.

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Right, over short distances it can be closely approximated with just a constant radius or even a series of straight sections, though working out the optimum bend points requires a bit more horn design knowledge, so the 825/828 are half size ~55 Hz exponential (flare factor ('T', aka 'M') = 1)/~110 Hz actual, IOW it's a section sliced out of a larger, longer expo horn. Since the 816 has the same throat area, axial length and side wall radius terminating into a smaller mouth it will have a T = < 1 or moving towards hyperbolic (T = 0.5), so we tend to call any flare between the two a hypex, then define it by its flare factor T (M).

I've never bothered to work out any of the parallel wall horn's flare factors or seen them published, so all I can say about the lot is that I highly recommend going to the extra effort of cloning an 825/828 horn for HIFI/HT apps due to its much smoother response, especially when wings are used, and adding its slanted bottom plate to the dual driver designs. Note that if wings are used in the home that bass traps are normally required behind them due to the cavity resonances that occur in a typical room.

GM

The early 515 and 416 are very similar and can be successfully used in direct-radiator cabs or horn cabs. The post-515E models of the 515 are specifically tailored for horn cabs. Very large motor and very light moving mass.

The 3156 is a direct-radiator woofer. Although this type of woofer can be installed in horn cabs and it handles lots of power, it can suffer from artifacts. There can be a distinct "coffee can" sound in some rooms. I would not run the crossover above 800Hz.

There are a dozen or more 816s loaded with 3156 woofers in the Lazy E arena (Guthrie, OK) and they seem to do all right in this large space.

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Originally Posted by valhallax

forgot to add..my 816's are loaded with 418-8h mi speakers

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That's a driver I don't hear much about..... what was it's position in the Altec Line-up.... or asked in another way, why did Altec need the 418, when it had the 421?

The A-6 could be a good choice. There's a theater up here ;1446 seats, with 5 A-6.
35mm and 70 mm projectors.

http://www.altecpro.com/pdfs/vintage...r%20System.pdf



Air conditioned projection booth, equipped with two 35 mm / 70 mm projectors (Century with laser reading system - reverse scanning) Avec
Size of projection screen
Height: 6.25 m (20' 6")
Width: 12.80 m (46' 0")

Installed with motorized winch on line set # 18
Speakers Altec A6 (5).
Surround speakers Bose 402 (24)
Amplification: Dolby sound system CP 200

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Originally Posted by Audio_by_Goodwill

...why did Altec need the 418, when it had the 421?

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421s are best in LF apps, bass guitar, synth, etc. 418s are more of a full range, not as good in the 2nd octave as 421s, but better up higher. 421s were ferrite, 418s (and OEM 422s) were all AlNiCo. As long as you have the box for them, 418s will do everything a 417 does and then some.

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Originally Posted by Audio_by_Goodwill

... Thirdly, I suspect you felt there were fish to be caught, and time was wasting :-)

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Bullseye! Only back then they wore skirts.

(Although there was some similarity if you didn't wash your hands...) :D

Many thanks for the response,
I'm hoping I can get 515s for the project and avoid having to fix the magnetic field by adding another magnet to the 3516s. Though I believe that this would actually improve their sound.
It turns out that my repairman actually visited GPA and met the folks there and talks very warmly about it all.
Kieran

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Originally Posted by bfish

421s are best in LF apps, bass guitar, synth, etc. 418s are more of a full range, not as good in the 2nd octave as 421s, but better up higher. 421s were ferrite, 418s (and OEM 422s) were all AlNiCo. As long as you have the box for them, 418s will do everything a 417 does and then some.

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Ok, that makes sense....... does the 421 have a 12" analog?

Nope. The bottom end likes big. ;)

There was a 15" OEM ~equal though, the 423.

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Originally Posted by valhallax

forgot to add..my 816's are loaded with 418-8h mi speakers

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Resurrecting ancient thread; sorry.

Are you using these for performance speakers, pa or music? How do they sound? I have some MI 15" by another famous old line pro audio company. They have a bit less bass than the 418 though. I'm beginning to be a little discouraged about cramming my Mod 19 dream into my minuscule shop.

Everybody must be outside playing today. The place is deadsville.

Thanks
Dan

actually, i use the 418's two different ways. in the 816 cab i often run them full range , as side fills or in guitar monitor applications. or in my as-101's... where ive obtained incredeble spl's with them. they are extremely effecient thus play very loud