2. speakers
  3. 127732-477

Materials to reduce sidewall flex & vibration ?

I am wishing to reduce sidewall vibration without adding reinforcement 
within the cabinet. I'm curious about fiberglass and other products that can attach/bond 
permanently to the sides yielding the highest stiffness to weight ratio.
ptss
bdp24's avatar
bdp24
9,792 posts
 
meerzistar is correct. Doubled wall panels and internal bracing is the best, most effective way to combat enclosure resonance. The sound produced inside the enclosure makes it expand, like a balloon being inflated. Bracing prohibits the enclosure walls from flexing outward in response to the internal pressure created by the drivers moving inward. And doubled panels stiffens the enclosure walls, reducing their ability to flex and thereby create sound.
ptss OP
1,964 posts
 
But, panels 'inside' the enclosure change the internal volume-
an area carefully calculated to work with the drivers used - to provide the right 'damping' for the drivers. This is why I am focused on the exterior.
meerzistar
232 posts
 
Thats why I suggested dowels, they take up less internal vol.. If I were to add sheet it would be on the outer sides. Dowel braces may not decrease internal volume whereas you can hear any difference. I found this to be true, although results can and often do vary. You could also think of it as the lesser of two evils.

Whatever measures are taken if the scales happen to tip far enough I might even consider making new boxes with more volume to compensate for planned bracing, thicker walls, mdf or hdf.

You may wind up doing that sooner or later anyway. Until then no experience is bad experience here.
bdp24's avatar
bdp24
9,792 posts
 

Yeah, the extra panels attached to the outside of the enclosure. For the interior, an alternative to wooden dowels is threaded steel rods, inserted into the enclosure through holes drilled into opposing enclosure walls, each rod screwed into opposite ends of a threaded coupler. The rods can be adjusted until they are tight enough to prevent outward panel movement. A locking nut can be threaded onto each rod, tightened right up against the wall interiors, thereby preventing inward panel movement. The rods can span the height, width, and depth of the enclosure, one set for each pair of opposing panels.

When I built my 4 cu.ft. sub enclosures, I built them double-walled, an enclosure-within-an-enclosure. I left 1/2" space between the two, maintaining the space with 1/2" "ribs". I then filled the space with #60 Silica sand. VERY effective wall damping! There were very large loudspeaker enclosures so designed and built in the 1950/60's, before Acoustic Research's introduction of the acoustic suspension principle killed them off.

meerzistar
232 posts
 
Threaded bar with poly locks is a great idea.  

Baffle diffraction would be another concern if the widths or edges is altered. Or by using stone or composite tile, that sort of thing. Even slight changes can negatively effect how well the speakers image. 
More to discover