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Marc HENRY wrote:

For this Musique-Concrete horn system called "Grande Castine" (it was developped in Saint Cast Le Guildo, Britanny, France, from were females inhabitants are called "Castines" ) i prefered a modified 60Hz Le Cleac'h cylindrical horn, with a "decompression" ratio of 1/1,4. the goal is : no cabinet sound, no bass reflex sound, high efficiency, a cutoff low enough to use an active infra-bass cabinet for the first octave, and a resonable size (1m*1m*80cm) it is fully usable from 60 to 250Hz. actual drivers are ALtec 515-16G

Well, I did not know that you have a second bass channel. Surely it is better direction to build bass. Are your first octave cabinets sealed? If so then you are in “open bottom” environment and it is, as I fell, is the best way to go. Or course if you have a dedicated first octave channel then for you upperbass you did not go, as most of the Morons would, for 515B or 515E type of driver buy you smartly went for 65Hz 515G. The 515G in 60Hz horn would do very nice… but… there are a few “buts”:

You need to unload the unnecessary bass out of this 515G driver, use 25Hz -30Hz high pass

Your 60Hz horn with that very large throat doe not load the driver down to 60Hz. You might disagree with me but make an experiment. Put 515G in an open baffle and RTA response. Then ran the same RTA from the same position with 515G horn-loaded. Now you will see where you horn will have equalization. Wherever plus 6dB boost stops from horn it will be the threshold what your 515G will start to run as a direct radiator.

I understand why you went for double driver in bas horn – to keep the thing shorter but I found it too much comprise to pay.

Marc HENRY wrote:

the mid is a 220Hz 2", with modified Radian 950Pb high-mid-treeble is a modified BMS 4540

Hm, the BMS drivers. I dealt with them in past, was not successful.

http://www.romythecat.com/GetPost.aspx?PostID=2855

There is guy who run a little own ass-kissing sweatshop http://www.bd-design.nl and he claimed that he used “modified BMS”. When I popped up at his site once and asked him about the modifications he was extremely not responsive. Ironically I was not ask what he modified (and I was under heavy suspicions that HIS modification worth nothing) I just asked him to name what dissatisfied him in the sound of the default BMS driver. He become very irritated, banded me from his site and if I am not mistaken he deleted my questions… become I “behaved badly at other forums that he read”. Interesting that I did not do anything bad at his site beside juts asking him why (sonically) he decided to “modify” his BMS drivers. Apparently the little sweatshop-running, frighten piece of shit felt that the questions were too highlighting the BS that he would like to keep secretive from his idiotic customers. Anyhow, I do not insist but if you wish to share your thighs about the BMS drivers modifications (and I do not encourage you to spill you secrets if you have any) then feel free to do so.

Marc HENRY wrote:

crossover : active 18db, 250Hz for the bass passive, 300Hz 6db for mid passive, 4000Hz, 6db for high.

Very good. May I suggest you something? You are not the subject of “Stop having a fear of horn vignetteing” rule:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=6147#6147

as you have large PARALLEL surface ahead of your tweeter. Why don’t you try to do what I did in my Macondo – use tall ribbon. With all other arguable advantage and disadvantage of Ribbons a tall ribbon would act as a line-array dramatically decrease the vertical radiation pattern – it is exactly what you might  need with your “Grande Castine”.  If you are interested you might read about the line-arrays:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=3013#3013

 … the type of the tweeter I use:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=2974#2974

 … and the thoughts that lead me to end up with what I ended up with:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=3766#3766

Marc HENRY wrote:

The problem with this bass horn is a great sensitivity to room acoustic.  not very surprising for an open baffle ! if there is any resonance in the room, bass become less "slamy", and fusion with other register is less good.

Yes, you are right. Open baffle is superbly affective tool to fight the room problems, however the dipole has on intrinsic problems – the type of the bass it produces:

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=1045

Also, I disagree conceptually that you try “curing” room by topology of speaker.  I am pitching very different philosophy. If you interested then you might read it here:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=4421#4421

Marc HENRY wrote:

several evolutions are coming : custom made drivers, an "open-cabinet" for the bass horn, a quite heavy all passive-all symetrical crossover...and an active bass cabinet for the 25-60Hz area.

Interesting, keep showing what you will end up with. I will promise  to keep criticizing everything – it is looks like my specially :-) BTW, why the crossover should be “quite heavy”? Why do not do passive line level and forget about all problems with crossovers. Do not repeat my mistakes when I orders expansive air-core 8ga coils. There are many reason what it did not and should not work.

Marco, sorry for many links but I did not want to write again that was said formerly…

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