GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.

Post Subject: Insulation et al.Posted by wvdave on: 7/25/2010

I too believe that you will want to insulate the roof itself as a partial means of regulating the thermal equilibrium in what will be the horn 'chamber', previously aka 'the attic'. The insulation on the floor of the attic was not installed under the roof because that was seen as 'heating and cooling unused space when said space was 'just an attic'(i find this to be foolish niggardliness, but that is not relevant here). The uninsulated space will take on the outside temp in the winter and a sunlight enhanced oven effect in summer with temp variations fluctuating thru the day as with the outdoors. This situation can't be good for the horns as a whole or in the elements of their construction. Regulating the thermal environment of such horns may even allow a certain amount of 'tuning' of a sort-don't know, but I would experiment w/it after I had stabilized things as far as possible. Again, I imagine your carpenter has this under consideration(taking the existing floor/ceiling insulation out and venting would allow the chamber to come to thermal equilibrium w/the house[given suitable under roof insulation], whereas leaving the floor insulated along w/the roof would offer the opportunity of treating the chamber as an 'incubator' sort of area for the horns w/its own environment.
Your carpenter does have a task ahead of him in cutting what are a series of angles to construct the horns-thinking before doing is important here, especially w/expensive wood. I had thought to suggest a 'sandwich' of 1" particle board(not the chip stuff, but sawdust mixed w/glue and formed under heat and pressure into sheets 4' x 8' coated on one side w/ spray on automobile undercoating(two or three coats to desired thickness, each cured to desired consistency between applications) then covered w/the birch to make a sandwich, with the birch being the exterior of the horn. The particle stuff is known for low resonance propagation and is very smooth, tough, and relatively cheap-but heavy. At this point I would have suggested cutting up some of just the particle stuff for practice and proof of concept before moving on to the sandwiching, etc.
As always, my ideas are just suggestions from someone not on the scene and they are not meant to impede the progress of those doing the work. I quite simply find this a fascinating project in line w/my own 'playback' interests. I also realize that since I am chasing my own projects of necessity, I may have missed something and be offering little that is relevant. But, onward, in any case.

Rerurn to Romy the Cat's Site