Ideas for Altec 620 bass cabinet bracing

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I'm starting on a 620 build.

The original design only used a single front to rear a few battens placed on walls.

I'm thinking of adding two or possibly three 'shelf' braces (with holes cut out) and placed at 1/3 or 1/4 distances.

Any thoughts on this type of application?

How important would you say is to have non parallel walls/baffles on the inside?

See this thread of a 620 build with two shelf braces.

My version of 620 cabs for Altec 605B




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Joined 2010
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Discussions on the Elsinore thread dealt with panel bracing (and i'm sure its been on other threads, too) and the conclusion was vertical bracing of large panels is best. Which doesn't mean that your horizontal braces aren't relevant but it might make sense to install vertical battens between them, and that big, unbraced, back panel should definitely have vertical bracing. Back when Jensen made their big coaxials, and triaxials, in big boxes, they reached the conclusion that dividing the big panels into tall narrow panels was the best way to reduce resonances.
Joined 2008
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That's possibly a different scenario. Panel resonances are one thing. The cabinet fundamental mode (the breathing mode) is a significant issue that may be best dealt with in ways other than vertical runners. It may also be less of an issue in a tall narrow cabinet, whereas panel resonances may be less of an issue in a bass cabinet.
Thanks...finished these today.

Back panel sits across numerous baces....poly glue ensures strong build.

Sounding very good...playing with MiniDSP. Have minor eq from 20-50Hz...and adjusted xover from 1200Hz to 1100Hz. Using 36db BW slopes.

Probably needs more height off floor.

Wool bats on 3 internal walls.


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Joined 2008
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Glad to hear you can start listening.

The picture of your tweeter gives more scope on the range of these cabinets (which I assumed would be less). You can test the effectiveness of your cabinets using a stethoscope. I can get greater sensitivity using a valve (from an engine), maybe a screwdriver and a glass? I'd also use many times the stuffing, but that's a matter for the individual.
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