bracing and lining a bass cab.

[crguti]

I own an Ashdown VS-212 cab, but there was something I didn't like when I got it brand new a year ago. There was too much vibration from the cab to the Ashdown ABM head I had on top. Furthermore, when I connected my ipod through the line-in of my bass head to listen some music, the sound was poor. The mid frequencies were not clear due to some waves cancelations inside the cab.
So I decide to move further and improve this cab by bracing and lining the inside walls (see attached pictures). I used a 3" width of some kind of wood for bracing and 2" of polyester batting (the stuff you find in sleeping bags) for lining.
The improvement was amazing. There is much less vibration and the mid frequencies are much more clear which is very evident when I play music through the cab.
Feel free to experiment with bracing and lining the cab. IMO it offers a real improvement.

[crusty philtrum]

Re: bracing and lining a bass cab.

You need to be careful when adding bracing, because it raises the resonant frequency of the cabinet, which may not be desireable.

[crguti]

Re: bracing and lining a bass cab.

^ Yes, you're correct. It raises the resonant frequency up to a point where it won't flex the panel giving as a result a lower amplitude as well. It's something I should have measured before and after doing the bracing, but the results where pretty cool and I really couldn't notice any detrimental effect. In fact with the lining the amplitude at all frequencies seems to be more even making the bass tighter and punchy with clear mids which is something I really like in a bass cab.
However I'm still waiting for a 6x10 cab and compare it with my 2x12.

[DrNewcenstein]

Re: bracing and lining a bass cab.

Interesting. Wondering if/how choice of bracing material affects the resonant shift, or if it's simply a matter of cabinet panel rigidity (i.e. would 2" diameter PVC pipe sound the same as a 2" wide piece of oak and a 2" wide piece of walnut).

How would using rubber washers between the speaker frame and mounting panel affect the overall tone? Or some sort of floating speaker suspension setup, so the speaker was not directly contacting the cabinet? (though in hindsight I'd be inclined to think that it would sound about the same as if the speaker were simply laying on top of the cabinet, or in the bottom).

If the rattle comes from the edges of the mounting panel losing direct contact with the top and sides, could the edges be tightened up using those little metal tabs you find in some old window panes (haven't busted out a window in 20 years, so I don't know if those tabs are still used)?

Or perhaps rebuilding the mounting panel so it either fits more snugly against the top and sides, or locks into them in a tongue-and-groove type of construction, or has a "gasket" all the way around it made of some sort of foam rubber-type material, like weatherstripping?

Or instead of cross-panel bracing like you've done, reinforce the edges of the panels with wood. But then, you go right back to the question of how wood/material type affects the tone.

[crguti]

Re: bracing and lining a bass cab.

the purpose of bracing is to create a node in the panel (the same as creating an harmonic in a string) giving as a result an increased resonant frequency with less amplitude too. That amplitude will depend of the stiffness of the wall material. AFAIK the material of the bracing doesn't have a big impact (unless you use rubber as bracing), it's more important how you attach the bracing (e.g. type of glue) because it needs to be rigid. You also need a rigid edge to mount the speaker, otherwise you will loss bass.

[crguti]

Re: bracing and lining a bass cab.

Or instead of cross-panel bracing like you've done, reinforce the edges of the panels with wood. But then, you go right back to the question of how wood/material type affects the tone.

as long as it's rigid, the type of material doesn't matter.