if it works leave it alone. heck the nicotine might just give you that authentic 1950s night club ambiance as they warm up.
Cleaning Altec H.F. Compression Driver Diaphram/Voicecoil
I'm in the process of restoring a pair of A7's . During inspection of the diaphragm on the 806A driver I noticed the front side facing the bugscreen was yellowish in color compared to the clean bright (aluminum) backside. Years of cigarette smoke. would it be worth cleaning the surface and if so what would be the best solution. I don't want to damage them.
if it works leave it alone. heck the nicotine might just give you that authentic 1950s night club ambiance as they warm up.
Sonic Barbarian
Yea, I think your right. I best leave well enough alone. It's gonna be hard enough to revamp this pair of A7's considering all the different and sometimes conflicting info from the internet. Heck, just today i've spent hours on whether or not or how to damp the cabinet, and to correctly port them. The 811B/806A will be mounted inside (looks like a factory brace).
Yeah, they're so old/used that the alum has long since work hardened [brittle], so cleaning might 'brighten' them up to the point of Symbiotik shrillness/'bite' [ugh!].Originally Posted by Phil-G
GM
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For a variety of reasons, though often due to cost cutting, Altec changed driver, cab build specs, hence your predicament, especially if trying to keep them period correct, so which series/model cab and ideally need the speaker's 391xxx date codes and if it can't be found, then the ones on the components?
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
After inspecting the other 806A i found the diaphragm all cracked up. So i will just order some replacements from GPA, part # 34852 is the recommended one I think. They did such a great job on re-coning my 416A recently (which had a fried coil) that I am sending my other one (which has a slight sagging cone) in so the two will have a better sound match. Now to tackle the Boxes (825's i beleave). These had a vinyl cloth skin glued on that was curling up all over and pealed right off with ease. Yuck what a mess.
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I just had another thought. Since my wife forbids these Monsters, her words, ever coming into the house what if I found some used cabs or built another cabinet more pleasing to her liking. The smaller the better. Any recommendations which cabinet would produce the best sound with these 416A woofers and 806A/811B horns.
There is a way.
It's not a scary monster after all is it? if you want the 511 horn enclosures let me know
Last edited by Phil-G; July 31st, 2020 at 05:15 PM.
Sonic Barbarian
Wow! those are beautiful and i bet they sound as good as they look. Not being that well versed on all the altec terminology, the 511's are the top HF horns? Is that what you were referring to? Hopefully one day and a lot of mending my pair will look,, well,, not exactly as nice as yours but maybe half way decent. This is what I found today while stripping them. They are VERY beat up..
Had forgotten how nice these look!
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Well maybe if you show her what they can look like.
Do you know a good car body shop?
Sonic Barbarian
Personally would just roughen, flatten them up and 'skin' them with 1/2" no void plywood, letting a thick layer of glue fill any imperfections.
Re a smaller cab, the 416A is fundamentally an 803B, which is optimized for the 825 horn cab's ~12.56 ft^3? net volume [Vb], ~62 Hz tuning [Fb], so at a glance, the obvious choice except for tuning to actual Fs to get the most BW out of it.
That said, the pioneers decreed that a vented Vb = Vas/1.44 tuned to Fs yielded the widest gain BW, best overall transient response for a given Vb, so ~510.7 L/1.44 = ~354.28 L /~12.51 ft^3, ergo now we know how the 825 cab's [Vb] was determined and what is required for a tube system's high output impedance.
All that said, T/S assumes no output impedance unless factored in, so assuming only a small amount for wiring, XO, then ~[20*510.7*0.25^3.3] = ~105.29 L / ~3.72 ft^3 [Vb] tuned to ~[0.42*23.5*0.25^-0.96] = ~37.35 Hz [Fb].
With a 5" dia. x 7.28" long vent, Hornresp calcs a 75 W peak power down to ~30 Hz.
Of course this assumes measured specs from ~45 yrs ago, so best to measure yours or have GPA do it for you and use the formulas to find the most correct [Vb, Fb] and calc a new vent length.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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