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