Congratulations on the construction and installation of your horns. May your pleasure at the results reward your effort and expense. I find their installed appearance even more geometrically striking than anticipated and I suspect now that some of the design choices I wondered about earlier can be attributed to a conscious or instinctive design eye.

As for the horn/drywall joints, basic ideas have been covered but here are some further thoughts:

1 - Settling:
In addition to vibration, remember the house framing is going to settle under the weight of the horns and the horns themselves will bend and warp a little as they respond to their own weight and the temperature and humidity in the attic – (they are not waterproofed on the exterior). This settling is going to expand the gaps over time and you may want to anticipate this.

The idea to keep the horn free of the wallboard/joint compound with a gap covered by some trim or thin fascia (face board) that is free to move with the horn but unattached to the wall probably can work even with serious settling.

2 – TRANSLUCENT silicone fill
For fairly thin gaps you can fill with translucent silicone AFTER painting. The color passes through the translucent material, which should be invisible for this use. You don’t paint over this so the poor paint adhering properties of the otherwise excellent silicone material is not a problem – it’s why they sell this stuff.

3 – Scoring or precracking
Create a deliberate crack and keep the horn and wall separate. You can create a thin straight and virtually unobtrusive gap by filling to the horn and scoring with a razor blade or utility knife and straightedge. If you are fussy, you can do this again after painting and slice through the paint with an even thinner slit. This should eliminate the tendency for unattractive irregular cracking where some cracking is inevitable. Deal with any widening gaps later.

4 – Accented foam stuffing
It you decide to use a fairly wide gap with some foam or other expandable material there is the option of giving this gap a distinctive appearance instead of trying to make it unobtrusive. You can loosely wind a colored ribbon or some interestingly textured material around the foam creating a contrasting border. The right person with good taste could make this work for others it’s an artsy-crafty flourish.

Cheers,
Robert

RF at Ona wrote:

Congratulations on the construction and installation of your horns. May your pleasure at the results reward your effort and expense. I find their installed appearance even more geometrically striking than anticipated and I suspect now that some of the design choices I wondered about earlier can be attributed to a conscious or instinctive design eye.

RF at Ona wrote:

In addition to vibration, remember the house framing is going to settle under the weight of the horns and the horns themselves will bend and warp a little as they respond to their own weight and the temperature and humidity in the attic – (they are not waterproofed on the exterior). This settling is going to expand the gaps over time and you may want to anticipate this.

Bill wrote:

A thought. Why not super-insulate the top of the attic against the roof with 20-30 inches of fiberglass insulation or 12 inches of foam and leave the space around the mouths of the horns open to allow circulation of air around the horns. Would probably cut your energy bill and at the same time keep the drivers at room temperature. Othwerwise they'll be very cold in the winter and hot in the summer.

Bill, hold on. Are you saying that moisture can go across the plywood? The whole point of plywood is that is has layer of wood mixed with layers of glue and as I undusted the glue is not transparent for water. Baltic Birch plywood that I use all marked with MR grade (moisture-resistant) as it made with Carbamide glue – I was told that it is water- resistant. I am certainly under presumption that plywood is much better barriers for moisture then regular wood. I would not want to have river of moist running outside of the horn but I do not think that condensation will be able to go across the horn. Of cause I might be wrong…

What I would need to do it to monitor the state of sand that is use around the horns. The sand shall be dry in there now. If I see that sand got most then it will be a sign. Or perhaps even better - I can buy in Radio Shake for $20 a remote temperature miter with humidity sensor:

http://www.radioshack.com/product/index.jsp?productId=2049773#