Dilemma regarding preventing standing waves...

[lunchmoney]

I'm going to be gluing my front baffles on my Tritrix Towers soon, but before I do so I have an opportunity to glue in a support brace (probably just below the drivers)... this seems like a good idea, for two reasons...

1. To increase rigidity of the cabinet, to keep the walls from flexing

2. To help break up any standing waves that might form

Sounds like a good plan... HOWEVER...

...if I glue in the brace, it might prevent me from being able to experiment with stuffing the lower region, something a number of people have mentioned might be important given the tall configuration of my speakers.

I suppose the brace could be small enough in cross section such that I can reach my hand in around it to experiment with stuffing, but then would the brace be broad enough to help prevent standing waves?

Whaddya guys think?

Also, what does a standing wave sound like? What do you listen for to see if it's a problem?

Here are some pix of the speakers:









Thanks for your help!

[lunchmoney]

I should add that I have tested them out, by clamping the front baffles on with some thin weatherstripping to seal them... they sounded great, but a little boomy in the low end... this might tighten up when the baffles are actually glued on, so it might be a non issue.

[augerpro]

Now I'm no expert on this so someone correct if I'm wrong, but I think you typically want a mound of stuffing in the center of the cab to reduce standing waves by slowing the velocity of the wave. I would think have this stuffing on top of this brace (assuming it's the typical shelf with holes cut in it) would work just well-or better- than it sitting on the bottom of the box. I mean push come to shove if this is what you had to do it should be ok...The only problem I see is if you make the stuffing too thick and dense, and it creates an impedance that keeps the woofer from "seeing" the whole box.

[dmalphur]

Brandon is correct, for the fundamental resonance mode the velocity will be highest at the middle of the long dimension. One problem I see is that the port is located close to the center as well and you would have to make sure the stuffing wouldn't block the port.

A good compromise would be absorption located at one third of the box depth, because it would be at a location of non-zero velocity for both the fundamental and second resonance of the lengthwise dimension. How you could ensure that the material stays there I'm not sure; it is more simple to just stuff the material at the bottom of the enclosure and if that works then it works.

-David

[Carl V]

agree, you need to brace that enclosure. How you
want to go about that is up to you. Window frame,
U shaped... etc., And you need more than one & don't place
them with any sort of symetry...stagger those modes. I most
often do a verticle & one or two horizontal. You can use 1"x2"
oak boards to stiffen up the pannels as well...glue them diagonally
across those long expanses. & glue them along the end grain.

If possible start stuffing & measure your impedance at Fb.
And of course use your ears.

[lunchmoney]

Ok, so here's how I ended up bracing them and stuffing the bottom. The two braces are perpendicular to each other.

The third picture has red arrows showing where the two braces are (duh).