A7 modified into pseudo 816 - Boom Boom Boom

[altec-man]

Whilst I'm still modifying/restoring my A7 boxes I thought in the meantime I'd try some 825 boxes that had been pseudo modified into 816's, these boxes were laying around and I thought, what the heck, lets try them. I put my 416-8b's,515/802-8D's & N1201-8A's into them. How could anyone think of using these cabs for anything that resembles music is beyond me, the bass was the typical Boom, Boom you get from a box that is way too small for the woofer (high VAS) and tuned way too high (Fb). I even messed around with the tuning with little success.
I am amazed that when people made mention between A7 (825/828) boxes and the 816 all they said was that the bass on the 816 was reduced. What about the Boom, Boom, Boom. Is it me or is this what other have found with the 816 and it's variants.

[Audio_by_Goodwill]

........ lets try them. I put my 416-8b's,515/802-8D's & N1201-8A's into them.

You tried both 416's and 515's? I'm not sure the way you wrote it.

I am amazed that when people made mention between A7 (825/828) boxes and the 816 all they said was that the bass on the 816 was reduced. What about the Boom, Boom, Boom. Is it me or is this what other have found with the 816 and it's variants.

I have a 9864A Engine, which has a woofer section that is based on the 515-GHP and uses the 816VI cabinet. It's been awhile since I've used it, but I don't recall it being boomy.......boomy was when I put a McCauley into an 828. It could be a couple of things. First a cut down 828 isn't an 816 exactly, second my 816VI is different still. If you only tried your 416 it could be that its not suited to the smaller cabinet, and the 515 doesn't mind it?

[GM]

I shortened quite a few 825s and tuned to ~42 Hz with a dual shelf vent they had a much more pronounced stepped response typical of a too small cab loaded with the usual 416s/421s and later, the popular JBL 2235H, so hardly a boom-box response.

That said, in one form or another I tuned all cabs using the 'click' test outlined in the Davis/Badmaieff book to ~critically damp the cab, so they may have had a 'one note' bass line had I tested them in the 'raw' with anything other than a single impulse signal.

GM

[Audio_by_Goodwill]

......That said, in one form or another I tuned all cabs using the 'click' test outlined in the Davis/Badmaieff book to ~critically damp the cab.....

I'm going to have to read that......I don't recall it, even though I've had the book for years.

[GM]

I only kept a later copy, but it's in the 'tuning, damping' section, pg. 77, fig. 4-21b in it.

GM

[Panomaniac]

Is that the battery click test that is somwhere in the Altec lit?
(where oh where?)

[bfish]

I don't remember where I learned it, but it works. The click from a battery should sound like a click, crisp, clean, no overhang. If it whumps, thumps, or otherwise bumps you need to tweak damping. Impulse response on the cheap.

[GM]

Yes, though I only recall seeing it in the Davis/Badmaieff book, which is basically an unofficial Altec one, and in a Weems article circa '56? when I suggested it to a fellow worker to maybe tame his highly resonant concrete pipe speakers without having to stuff them. It worked OK, but with its strong TL modes he could only damp them so much without tearing them apart to add stuffing.

GM

[Panomaniac]

It's also in an Altec tech note from the 70's, IIRC. Will dig around to see if it can be found.

[altec-man]

I'm sorry if I got a bit carried away with the boom, boom expression. What I found was that at certain frequencies in the BW up to 1200Hz certain notes were either nasually or honky. I didn't try the 515C I have as I've found that this woofer needs a box even bigger than what the 416 does, personally I find the 416b the best all rounder for home applications.

GM, I too have that book you mention, will try the damping testing later.