Hi All
I recently refreshed a pair of Klipsch Tangent 500 that were coming apart at the seams. I glued and clamped them back together, and noticed that they are of inferior construction to the pairs of Heresy II, and Quartets that I also own. The cabinet material is thinner and the boxes sound much more hollow and resonate more when tapped. Anyway, I came up with a very effective damping method for the panels that is very simple, cheap and completely reversible. I will attach drawings, as it is much easier to show what it looks like than explain it.
I recently refreshed a pair of Klipsch Tangent 500 that were coming apart at the seams. I glued and clamped them back together, and noticed that they are of inferior construction to the pairs of Heresy II, and Quartets that I also own. The cabinet material is thinner and the boxes sound much more hollow and resonate more when tapped. Anyway, I came up with a very effective damping method for the panels that is very simple, cheap and completely reversible. I will attach drawings, as it is much easier to show what it looks like than explain it.
Stick, square and memory foam
I did this between the sides in two places, and between the bottom and top and the front and back in one place each, for a total of 4 braces. The "squares" were actually of various shapes, and I placed the stick in a place where it was not centered in the square. I also varied the thickness of the memory foam so that the pressure on the cabinet wall would vary in different places. I think that this method should create an area where the cabinet has a double wall with a vibration absorbing layer between. This area is different from the rest of the cabinet wall and is very inert. I figure it should break up the resonances of the panel and absorb vibrations. It also ties the two sides of the cabinet together with a damping assembly that stiffens the structure but doesn't pass vibration through it well. This method also adds a substantial amount of mass to the cabinet walls, as memory foam is heavy. There are two issues. One is that it takes up some internal volume, and the other is that it exerts outward force against the cabinet wall, so the cabinet must be sturdy. I used memory foam, 2 by 2s and plywood, but it could be made out of almost any material for the stick and squares, and the sandwich could be some other squishy stuff, or combinations of squishy stuff. What do you folks think about this?
I did this between the sides in two places, and between the bottom and top and the front and back in one place each, for a total of 4 braces. The "squares" were actually of various shapes, and I placed the stick in a place where it was not centered in the square. I also varied the thickness of the memory foam so that the pressure on the cabinet wall would vary in different places. I think that this method should create an area where the cabinet has a double wall with a vibration absorbing layer between. This area is different from the rest of the cabinet wall and is very inert. I figure it should break up the resonances of the panel and absorb vibrations. It also ties the two sides of the cabinet together with a damping assembly that stiffens the structure but doesn't pass vibration through it well. This method also adds a substantial amount of mass to the cabinet walls, as memory foam is heavy. There are two issues. One is that it takes up some internal volume, and the other is that it exerts outward force against the cabinet wall, so the cabinet must be sturdy. I used memory foam, 2 by 2s and plywood, but it could be made out of almost any material for the stick and squares, and the sandwich could be some other squishy stuff, or combinations of squishy stuff. What do you folks think about this?
Bracing. Yes, that's it. I haven't seen it done this way though. I have done it the way that Brett suggests, several times, as have many. This has a different result. The cabinet is less resonant than with regular bracing, which moves the resonant frequency to some other higher resonant frequency in a very unpredictable and fairly permanent fashion. This method does this non permanently, also dampens vibration and can be tuned by moving the positions of the squares, varying the squishy stuff and changing the stick length if you don't like the result you get the first time. That is not possible with regular bracing.
I wouldn't bother using this on a new cabinet build, and would use regular bracing and appropriate materials to produce an inert cabinet. However, for an existing speaker, it can be done through the driver cutouts, in situ, with very little time and effort. The last time I braced the poor cabinet of an existing speaker the regular way, it took a lot of effort and a very long time to complete.
I checked out the KEF ls50. It looks similar to what I did. The KEF brace goes from panel to panel and has a different material sandwiched between the brace and the wall. The KEF brace seems to be cross shaped with flared ends instead of a stick and two squares. It would appear that it is built into the cabinet when it is manufactured. My bracing method can be installed into most existing commercial speakers after the fact, through the driver cutouts. It completely deadened the cabinets of my Tangent 500s. The cabinets are now noticeably more inert than previously, and the speakers sound better as well. I judge them using my Heresy II as references. Before the fix, I preferred the Heresy II over the Tangent 500 by a wide margin. Now, I still prefer the Heresy, but it's close. The Heresy have a nicer midrange and treble, but the Tangents have bass.
Thanks for the info midrange, and for the encouragement. I read the LS50 white paper. Very interesting stuff in there. Most significant to this thread were their findings with regard to regular bracing not reducing the amplitude of cabinet resonances relative to the driver, and their finding that the frequency was moved up towards the ear's most sensitive region. The results of regular bracing are shown on figure 9 (page 11) of the white paper. Figure 10, on the same page, shows the KEF brace result. Brett, do check the white paper out. It's findings correspond to my own extremely unscientific ones.
Now what I need to figure out is how to apply this concept to the exterior walls of my recently acquired 1976 Klipsch La Scala speakers. I was loath to glue in the brackets that most people use on them. Other than a capacitor refresh, they are all original, and I want them to remain this way. The brace would have to go from the sloped walls of the doghouse to the side panels. I guess I could use something more rigid and sticky on the slopes plane and use the foam on side panel side. Any ideas would be appreciated.
Somewhat off topic, but related as it regards the use of memory foam, is the damping of midrange horn resonances with foam. In the Tangent 500s, I cut sheets of memory foam and wrapped the midrange horns with thwm. I then used sturdy string and tied the foam layer down to the horn exterior. This completely deadens the resonance of the horn, and is also completely reversible.
Have used threaded rod and large flanged nuts.
Cut the rod to the approximate length with the flanged nuts screwed onto the rod.
Put the rod in the cabinet and back the nuts up to the end of the rod. You can put adhesive under the flanged area of the nut before you tighten it to make it more permanent.
Can be installed in very tight spaces which I like.
Last time I used it was in a large rectangular ported enclosure that had noticeable movement of the port panel. You could use threaded wood inserts too instead of flanged nuts.
Cut the rod to the approximate length with the flanged nuts screwed onto the rod.
Put the rod in the cabinet and back the nuts up to the end of the rod. You can put adhesive under the flanged area of the nut before you tighten it to make it more permanent.
Can be installed in very tight spaces which I like.
Last time I used it was in a large rectangular ported enclosure that had noticeable movement of the port panel. You could use threaded wood inserts too instead of flanged nuts.
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