effect of heat in chamber

Just wondering if enclosure designer's take into account the effects of heat buildup within a scoop chamber, and its effect on air density? The reason I ask this is because (I'm a time served mechanical engineer) the temperature of the air drawn into the combustion chamber of an engine has a direct bearing on it's compression ratio.
In a scoop bin where the diaphragm is acting on the mass of air in the chamber which causes pressure through out the horn to move a much greater volume of air at the mouth will rely on the density of air in the chamber to efficiently couple to the air in the horn.
In the last decade, the power dissipated by modern high power drivers has risen and so has motor temperature. This must have an effect on on enclosure efficiency. Could this also be a factor in thermal compression ?

ive not read much on this, but yes is my opionion, any build up of heat in a chamber will change the compression ratio, i allways warm up my drivers before testing in any prototype im working on, to get a better graph plott of the cab....

I think there would be an equation which would plot a chart for air density in relation to temperature. if that can all be quantified, we would need to find a way of keeping that space cool.
BTW, over a 2 year period we played the same hall, speakerstacks always in the same position, similar crowd numbers etc. When I was operating I could feel a (slight) difference in bassline weight which seemed to be weather dependent! Anyone else experienced this?

I think I remember sound travels better through humid/moist air than dry air. Also, wind or even a high power fan can distort the sound.

there is a white paper on this site that is very interesting.....

Environmental Effects on the Speed of Sound*

I'll have a read.... thanks

valvehead wrote: Just wondering if enclosure designer's take into account the effects of heat buildup within a scoop chamber, and its effect on air density? The reason I ask this is because (I'm a time served mechanical engineer) the temperature of the air drawn into the combustion chamber of an engine has a direct bearing on it's compression ratio.
In a scoop bin where the diaphragm is acting on the mass of air in the chamber which causes pressure through out the horn to move a much greater volume of air at the mouth will rely on the density of air in the chamber to efficiently couple to the air in the horn.
In the last decade, the power dissipated by modern high power drivers has risen and so has motor temperature. This must have an effect on on enclosure efficiency. Could this also be a factor in thermal compression ?

Well I have in my K1 design. The heat starts to dissipate after only a short while. Very pleased with the outcome. This gives me/user a good long term use with minimal degrading in sound and energy. Anything that gets hot will perform less better than it was when it was it's normal working temperature (apart from an oven) EG cars, human beings etc. k1 is a FLH with a sealed chamber. Scoop is a RLH with no sealed chamber. The air gets pushed from the cone and over the magnet assembly and out via the horn, so not as bad. Why are you questioning this? I wouldn't look too much into it if you're designing a scoop. I think your gain for keeping a driver a little cooler in a scoop will give you minimal results. Just concentrate on designing a better scoop rather than working out HOT it is in a open chamber. the Punisher design suffers from thermal problems and users can go through quite a few drivers.

When or how do you determine when a heat sink is necessary in a cab? All the newer CV cabs, B52's, and LAB horn use heat sinks, why not the 1850/186 horn for instance?
www.rockbottommusic.com/b52_folded_sub.jpg
cachepe.zzounds.com/media/quality,85/775...faab57c9234bebc2.jpg
www.pispeakers.com/12Pi_side.jpg

in the proto type stage of a design, if the driver gets too hot in testing, heat sinks can be added, or a pole type heat disperser, not sure of the correct name. Its an ali tube that mounts through the back of the magnet and aids cooling....

So how would one go about testing a folded horn to see if it did need a heat sink or not? Send a 50hz wave thru it for 6 hours, then open it up with oven mitts on the ready? Use it for a 12 hour dubstep rave, with marshmallows on hand for when the cab bursts into flames? Or just play it long and hard until the voicecoil melts into the magnet? :whistle: