Bracing & Glop

This third section describes the bracing and application of North Creek "Glop" which is used to provide damping to the cabinet side panels.

The North Creek cabinet designs are robust and very well braced. The Parts Express cabinets are very good and a great value but are not as soundly braced. We wanted to have as dead a cabinet as we could afford while basing the design on the North Creek methods. The North Creek designs have extra bracing made of plywood and spaced so as to reduce panel vibrations. We were concerned with the solidness of the Parts Express cabinets and especially the sound of the side panels near the front when rapped hard with the knuckles. We decided to add some additional bracing following the North Creek design concepts. To help determine where the bracing should go we decided to dry fit the drivers and fascia to see how things would line up (see previous post).

We decided to place the brace between the front panel and the original Parts Express center brace. We would follow the North Creek brace format, but would use smaller pieces of wood to keep the area open for the backside of the drivers. We purchased some Poplar 3/4" x 3/4" stock for the side and top brace, and some 1-1/2" x 3/4" stock for the middle brace between the side panels. (The North Creek braces can be seen on pages 2 and 4 of the Kitty Kat drawings. Although this is not strictly the same materials and thicknesses as North Creek suggests, we felt it was much better than doing nothing!

We began by gluing one side at a time the left, then the right, then the top side of the brace. We will install the center brace only after the glop has dried and the crossovers installed and wired. This helps keep the cabinet open during installation.

We cut all the braces to length and marked them as shown below.

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The following photo shows the sides and top brace glued in place and drying in the Kitty Kat cabinets. The cans are used to keep some weight on the braces during drying. Real clamps would have been better but we did not have any that would work around the cabinet shape. These braces were spaced from the front so that they would be behind the woofer motor magnets so as to not interfere.

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This photo shows one of the Casita cabinets with the brace installed and the first layer of glop just after pouring it in. In the North Creek cabinet handbook (See Price list) a recipe for glop is shows and 2 parts soft white glue and 1 part premixed drywall compound. In the Kitty Kat drawings, the exact recipe is not stated, just to 'use the remaining NCMS soft glue.' We also purchased a bottle of Aleen's Tacky Glue on the advice of North Creek in a private email as a suitable substitute for the glue they used to supply.

We created the first layer of glue using 2 cups of glue to each 1 cup of premixed drywall compound. This proved to be a very thin mixture that flowed a lot during the first 30 minutes after application. It was only after working with this thin mixture that we discovered that a 1:1 mixture was more common in the drawings of several different systems on the North Creek site. It took a long time for this glue to harden up enough that we dared to turn the cabinets over and apply to the other side. The stuff is pretty messy and touch to control as it takes a long time to empty a measuring cup! The good news is that it easily cleans up with water.

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This photo is a close-up of the brace and glop in a Kitty Kat cabinet. The glop is messy and drips all over, but it is mostly where it belongs!

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All five boxes were done at one time, requiring a lot of glue and drywall compound which we mixed in a large stainless steel bowl and applied with a 1/2 cup measure. We purposely put more glop in the back half of the cabinet as there is less bracing there and all four sides are constricted which keeps the glue in place. With this relatively thin mixture, the glue flows clear into the corners without effort. The glue was at least 1/4" deep before drying in the back and between 1/4" and 1/8" in the fronts.

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After a few days of drying, it was clear that a bit of help was needed. All five cabinets were then stacked and a small fan was place in front to keep the air circulating. Even with the fan it took a full week to dry hard enough to move ahead with the opposite side.

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The glop for the second side of the cabinets was done in the same was as the first and also required a week of drying with the fan. After this time, we decided to apply the remaining glue and drywall compound to the top even though the North Creek instructions say it isn't necessary due to the small panel size. We used up all the Aleen's glue and a quart of North Creek NCMS glue doing the second side. So we mixed a 1:1 batch with NCMS glue and the last of our drywall compound. This mixture proved to be a lot thicker and indeed had to be troweled into the top spaces both front and back. It also dried in a completely different way than the 2:1 mixture, much faster, and with cracks and fissures opening up. It remains to be seen if this extra amount helps or not, and we may never know, but at least we used up all our supplies with no waste at the end. The glop in the tops can be seen in the next set of photos during the crossover installation.

Please see the next article in the series Installing Crossovers and Wiring

Copyright © 2010 David L. Bytheway