Cabinet from Old Altec Literature

[airboss]

As I've mentioned before, I'm not quite able to squeeze a Mod 19 build into the space I'm allotted by the family at this time. So I've been looking over what's out there, fooling around with boxplot and generally sifting through things to come up with a solution.

I had picked up the old Loudspeaker Enclosures, Their Design and Use by Altec many years ago (the prices I wrote in the margins are amusing).

Anyway. Real simple here; it looks like the offset of the horn back from the front of the cabinet in this design would be identical in terms of phase accuracy as the Mod 19 considering that the Mod 19 used the front mounting 416B and this cabinet uses the 416A which rear mounts. Is this a correct interpretation?

Given that, considering the smaller size and the difference between centers vertically I am thinking that the N1201A would still be the appropriate crossover for this box. I'm using the 416A the 808-B and the 811B horn.

Does anyone have any experience with this cabinet? It looks like maybe very close to some of the commercial offerings from Altec at the time for home use. The above mentioned text also suggests that the ideal volume for the 416a is 7.5 cubic feet with a standard (non-ducted port). This as you can see is a ducted port.



Anyway, your comments would be appreciated.

Dan

[bfish]

That box was for an 800Hz XO'd 806, so a 1200Hz XO needs less offset, and your ~1/2" longer 808 body lessens the offset even more. Use the exact M19 offset, compensated for rear-mounted woofs, and you should be good to go.

[Todd W. White]

Looks like one of the portable systems - a 1218, if I remember right.

[Old Guy]

Looks like one of the portable systems - a 1218, if I remember right.

That was my thought

[bfish]

5.65" voice coil offset (center of woofer front plate to center of 808 rear plate) will get you half-wave offset at 1200Hz. (as opposed to 8.475" for 800Hz).

[airboss]

5.65" voice coil offset (center of woofer front plate to center of 808 rear plate) will get you half-wave offset at 1200Hz. (as opposed to 8.475" for 800Hz).

There it is. That nails it rather than trying to find a 416B to measure compared to my A models. I got to thinking last night that there may be some clever ways to front load the A model too. I'm thinking some very low durometer buna rubber glued into a route in the baffle, backed by a plywood support ring on the inside of the baffle and brass thread inserts into the wood for 10/24 or 10/32 screws. The only difference I see really is the bumps in the back side of the frame ring. Let those sink gently into a soft rubber and set the support screws with a torque screwdriver. Seal for leaks. Observe proper offset. I've found generally, through the years with guitar cab building that front mounting does sound noticeably different.