604 back mounting questions

[rogerh113]

I have not determined the cabinet yet - something like the one you show, the Stonehenge III, or Billfort's version. Probably more tall and narrow than short and squat.

First I am planning to build up a 'test mule' for open baffle to see what that sounds like. I got a 'scrap' piece of 3/4 mdf from a local building site (happen to know the contractor), and with a little effort will put together one open baffle. That should give me a good sense of the sound, and also the trade off with regards to diminished bass. I imagine that it is quite system, room, and design dependent. Based on what it sounds like to me, I will decide on whether I want to proceed with a real open baffle implementation, or move on to deciding on a specific cabinet build. I will also try to find out about TL cabinets as well, just to cover the bases. I've only looked at that a bit, and have been unable to find any plans for TL.

regards -- Roger

[VolvoHeretic]

So, I made a quick diagram showing the 604-8G mounting requirements, sorry I didn't have time to draw the speaker to scale: 604-8G

A knife cut threaded insert for either a 10-24 or a 1/4-20 bolt are the same size; 3/8" dia. x 1/2" deep:
1/2" Brass Slotted Drive Knife Thread Insert with 1/4-20 Internal Thread Size

[GM]

You don't think the 4 bolts leads to more vibration of the speaker frame against the baffle?

Original Altec frames are really rigid, but not so sure about the later cast ones [seen too many damaged ones in prosound apps] and use good quality composite gaskets, so [4] bolts is sufficient for the former and enough folks are fine using [4] with the latter, so your call, though in theory more is better and continuous clamping best overall.


That said, the truly best is none, like was done in the early days of 'subs' where they were floor or stand mounted and the baffles just close with an inner-tube like leather seal spanning the gap. Regardless, the motor brace will go a long ways towards quelling any vibration concerns and supporting the majority of its weight.


GM

- - - Updated - - -

Probably more tall and narrow than short and squat.

I will also try to find out about TL cabinets.......

Everything you need to know about the various TL alignments: http://www.quarter-wave.com/index.html


There's no TL designs for Altec drivers AFAIK, only vented TLs [MLTL] due to driver specs and since tall is acceptable this would be the preferred alignment if vented is desired.


GM

[rogerh113]

Thanks for the mounting graphic.

Good link on TL. I am trying to contain myself until I have a listen to the open baffle. A lot of this stuff is so interesting it can suck you in like a black hole......

regards -- Roger

[GM]

Understood; indeed it can! Got sucked in at age 8 and will probably continue to 'fiddle' with it until I physically can't.

OB definitely is the theoretical ideal loading for point source drivers and why the pioneers used it in large room, cinema apps, but small room acoustics can make it a tough 'row to hoe' getting it right unless the transition from OB to the nether regions is fairly high in frequency, somewhat negating the OB's benefits. Now if the room's walls, ceiling can look like it's made from freeform rubber and just as soft to the touch..........

Anyway, good luck with it and hope you only need a separate driver [ML]TL or other box alignment for the < 80 Hz [or lower] BW.

GM