Cabinet 816-A For 421-8H Series II

[stratsrus]

I would like to build a set of 816-A cabinets from the factory Blue pirnts. I recently came across some 7 ply marine grade plywood. The problem is that it comes in sheets of 2' by 4 '. The blue prints call for 26" from front to back. Would it effect the cabinet that much to shave 2" off this measurement, holding all other measurements the same? It seems to me if I brought the speaker forward two inches, I would have the same cubic mass behind the speaker and the cabinet would still be tuned. I plan on using two of these for a biamped pa for a band with a 421-8H series II or 515B's in them and 288-16G's on top through 511E horns. I would welcome any suggestions.

[AllanCT]

Just a couple of simple suggestions.

Have someone preferably an Altec guy from this site model the box you intend to build 2" short on some design software.

I personally would build those panels with regular plywood to the Altec recommended sizes.
I don't like building boxes once, let alone twice!

One other minor detail is marine grade plywood while bulletproof and strong is also very very heavy for PA use and mobile use. For free I'd take all I could get but make sure you have well balanced handles.

Other than that sounds like a good project and the right choice of woofer.

[marcuswilson]

If you shorten the horn section of the cabinet, the horn response will be compromised.
Why do you want to build an 817? It's not a great box.
I would suggest building a ported front loaded cabinet using the T/S data modeled in a speaker design program. You get almost as much output, less frequency anomalies and it will be half the weight and size. You will get twice as many in a truck and twice the sound.

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Two inches will be a BIG departure, as far as I can tell. I calculated the reflex volume of the 816 as approximately 145L; shaving two inches will reduce the reflex volume by approximately 18L, an appreciable fraction.