I had a meeting with my carpenter and he pitched me two interesting ideas

1)      Because we built ¼ of horn then the curve is relatively small. So, after do some circulations he asked me: why my triangle might not have two flat perpendicular sided and one curved side? I think that if the area of each distance from throat is the right one then it shall not be a problem.

2)      After calculating the chords of horn curve he proposed that it would be much better of he built first a paper-made prototype of the horn, let say 10:1, I call it “maket” Then he feel he will be more accurately shape the chords of curve and the pattern of transition peace (BTW, we know how the transition will be done now). After we play with the maket then the full size horn will be just subject of multiplication by 10

The caT

Romy the Cat wrote:

PS: is work Maket used in English?

This is a complicated subject.

While building the horn I would need to know what the size of back chamber to make.  Usually the initial size of driver diameter plus two depth works very nice. It makes big chamber that eventually might be minimized to tune the resonance frequency properly.  I do not have the Jessie’s luxury to build metal, high-precision, calibrate back chamber. My back chamber will be simpler and I will be using acoustic foam to minimize the side tuning the resonance frequency to the horn rate.

http://www.romythecat.com/Forums/ShowPost.aspx?postID=2991#2991

There is however a kink in my situation.  I really would like do not open and close the Back Chamber and do not staff it with filler while the horn in attic. I would like to do it while the horn at ground level BEFORE the horn will be lifted up and slide into the wall. My horn is 1.4 size and after it will be installed it will “see” the ceiling of my cathedral room. It means that the volume of the air from my cathedral ceiling pitch will be added to the mass of the air in the bell of the horn mouth, changing the rate of throat reactance and consequentially driving the resonance frequency away.

So, there are 3 options to deal with it.

1)       Set the resonance frequency after the horn are lifted up and installed. I do not want to do it – too little room will be left in attic between the horns and large center air unit.

2)      Make a maquette (thanks coops) measure that deviation of load between floor and cathedral ceiling and to presume that the delta will be the same for large horn. I do not want to do it as well as I feel it will be very inaccurately. The large horn will behave very different.

Romy the Cat wrote:

Where to buy inexpensive birch plywood? There are American, Canadian, Russian and Chinese birch plywood. I would like to go with Russian – much better quality, but it got pricy nowadays. I would like to pay for ¾ sheets of 4 by 8 no more than $40-$45 in case of mass buy. If any of you know in your jurisdictions a sores to get cheap Baltic birch then let me know – I might arrange shipping. Still, I would like to get the plywood in New England and to pick up it locally

Ok, the source for my Baltic Birch is found. It is in NH (means not sales tax), it is just 30 min from my house (I can pick it up). They have in stock “clear face” Baltic Birch of ¾ and at the price that is more or less reasonable.

http://www.pjclbr.com/

I think I will be loading with Russian Birch on Saturday. If everything will be as I planed then next week the project will be on it’s way.

msaudio wrote:

Every frequency above 80 cycle's should be coming from the front of your listering position, next to macondo.