421-8H Series II

[Strat2805]

I have a pair of 421-8h series II Speakers that I want to use in a bi-amped pa system with 511E horns and 288-16G drivers. I need to build a set of cabinets to the Thiele Small parameters of the 421-8h series II speaker. There are several software packages that calculte the box design, but when I try to use them, they ask for attributes other than those listed on this website. I simply do not know enough about it. I want to make a simple box design with the speaker front mounted and a bass port on the bottom front pannel, similar to the Yamaha S115V. Does any one know what specs I should use for my design?

[cclark65]

Here is a listing of what the 421 series were used in:

http://www.lansingheritage.org/image...ers/page09.jpg

You should be able to find cabinet specs somewhere for them, and get a good start there. Here are a few altec plans:

http://www.lansingheritage.org/html/...ltec-plans.htm

[Todd W. White]

For a modest fee, the T/S parameters for your speakers can be measured for you as one of the services provided by Iconic Mfg. Co.

[GM]

Typical PA tuning dictates a fairly high tuned, somewhat underdamped alignment, so based on some old measured specs I have, a ~2.92ft^3 cab tuned to ~55Hz works for me: 22" x 17.187" x 13.75" inside dims with a 6" dia. x 3.25" vent.

Some folks will accept more 'ringing' than me to get more midbass efficiency, so you may want to try it first with just a 6" diameter hole cut in the baffle (3/4" min. assumed).

GM

[Strat2805]

What dimensions would you use if the port was vented and not round, similar to the vent on a 816-A?

[GM]

A square of the same area, though of course it can be a rectangle up to a ~9:1 aspect ratio, but testing different vent lengths is a pain compared to a round tube.

GM