Jean Michel on LeCleac'h horns

[David McBean]

Originally Posted by gedlee

The fact is that if there is no mouth reflection the real part of the impedance of any device with the same throat size will be identical.

At all frequencies - I don't think so...

[Jmmlc]

Hello David,

Anyone can be convinced of that looking at the classical graph on
fig. 2 in Bjørn Kolbrek's paper in AudioXpress.

http://www.audioxpress.com/magsdirx/...olbrek2884.pdf

and comparing the curves for the conical horn and an hyperbolic (e.g.).

This is for infinite horns therefore there is no reflexion at the mouth.

Best regards from Paris France

Jean-Michel Le Cléac'h

[Pano]

Originally Posted by thend

I dont know, maybe the "free air" Fs of this driver is above Fa anyway.

Above the Fa of this horn for sure! That is the interesting part to me.

And a classical compression driver which can reproduce the 130hz without ditortions, I do not really believe.

It probably does not exist. Maybe one of the BMS coax or the old Altec 290 "Giant Voice", or something from ALE. But none are meant to work that low are they?
So it's going to be hard or impossible to match Fa & Fs if you want to play low with a compression driver. Easier for more typical horns sizes.

[Jmmlc]

Hello,

As you know I have no commercial interest in audio but I wanted to point out that my friend Marco Henry has completed a commercial version of a horn systems using 3 Le Cléac'h horns (one upper bass, one low-mid/mid and one mid-high/treble) .

Pictures of that new issue of the "Grande Castine" can be seen on Musique Concrete's website:
http://www.musique-concrete.com/MC/ENGalery.html

Below 80Hz the system is helped with a special subwoofer (not pictured) conceived by Marco Henry (from what I know it uses a large rectangular diaphragms and operates in dipole...)

The "Grande Castine" will be demonstrated soon in an Hifi shop in Paris. I'll let you know when it will be possible to listen to it and where.

The "Grande Castine" (without the subwoofer) uses 6dB/octave crossovers, it is time aligned and its efficiency is around 112 dB/1W/1m. The minimal listening distance is quite small (3 meters) and the sweet spot is large. The 3D image is fantastic. The coherence between the drivers is excellent. Marco told me that it is better to operates the "Grande Castine" inside an auditorium having minimum 50m² area.

Best regards from Paris, France

Jean-Michel Le Cléac'h

[thend]

Anyway, Fs≥Fa is better than Fs<Fa for group delay, because it's the horn which introduce more distortions in time domain.

[gedlee]

Originally Posted by David McBean

At all frequencies - I don't think so...

David

Yes, of course, I should have said "above cutoff". At cutoff there is a mass load, but even this is nearly the same for all shapes with the same throat size (if they are infinite then there is no mouth size). It's the incorrect math from Webster that predicts large differences in the throat impedance for different horn shapes. I showed in the Audio Express article (the second part) how three different horn shapes with the same throat and mouth resulted in an almost idendical response (the differences were due to the different lengths required to get the same throat and mouth areas.) And I also showed how the OS when viewed through Websters approach yields the same answer(incorrect I should note) that is found for the Exponential Horn. In Websters approach it all comes down to wall angle, which is proportional to the Divergence, which is where the mass term comes from.

At any rate, all this arguing about loading is simply not important to me and this IS Jean-Michel's thread so I'll go away.

[Jmmlc]

Hello,

I don't know anyone silly enough to use in the mid a Le Cleac'h horn with a angle of aperture near throat similar to any known OS waveguide. As I said previously in that case such horn should only be used for a (supert)weeter.

Inversely I'll be interested in knowing any OS waveguide having an impedance curve similar to the AH425 or my J321... this simply doesn't exist!

Best regards from Paris, France

Jean-Michel Le Cléac'h

Originally Posted by gedlee

David

Yes, of course, I should have said "above cutoff". At cutoff there is a mass load, but even this is nearly the same for all shapes with the same throat size (if they are infinite then there is no mouth size). It's the incorrect math from Webster that predicts large differences in the throat impedance for different horn shapes. I showed in the Audio Express article (the second part) how three different horn shapes with the same throat and mouth resulted in an almost idendical response (the differences were due to the different lengths required to get the same throat and mouth areas.) And I also showed how the OS when viewed through Websters approach yields the same answer(incorrect I should note) that is found for the Exponential Horn. In Websters approach it all comes down to wall angle, which is proportional to the Divergence, which is where the mass term comes from.

At any rate, all this arguing about loading is simply not important to me and this IS Jean-Michel's thread so I'll go away.

[soongsc]

Originally Posted by Jmmlc

Hello,

I don't know anyone silly enough to use in the mid a Le Cleac'h horn with a angle of aperture near throat similar to any known OS waveguide. As I said previously in that case such horn should only be used for a (supert)weeter.

...
Best regards from Paris, France

Jean-Michel Le Cléac'h

I was actually going to try some simulations with this configuration using a 3" driver.

[tinitus]

I wonder whether showing the flaws of this and that waveguide, is it actually scaring people not to build anything
Sorry to say, but constantly seeking perfection is a dead end
That will never happen anyway
Research is very good, and some of the sims does seem very good
They are indeed very educational and informative
But building it is even better

I dont know, but there seem to be a constant battle about something I dont understand
Would be nice to join forces instead, to encourage people to just do it

Well, pictures by Jean-Michel is a great inspiration, thanks

Personallly, I will start with a couple of cheap waveguide, just to see if theres any point in it
Maybe modify them
Surely not perfect, but at least a try, and a step on the way

Its not WHAT you do, its HOW you do it
It wont get perfect, just better

[Jmmlc]

Hello Tinitus,

Your philosophical words will surely be much appreciated by a large part of the DIYers community.

I participate(d) to many group project and to join forces around a given goal is surely something I consider very positively.

IMHO many discussion threads on DIYAUDIO can be considered as a kind of group project. In a group project technical choices has to be done at a given moment and it is quite normal that different options appear and that strong opposition between the proponents arise. This should not be considered as a fight between individuals even if the character of every of use differs from the other's one...

Best regards from Paris, France

Jean-Michel Le Cléac'h

Originally Posted by tinitus

They are indeed very educational and informative
But building it is even better

Would be nice to join forces instead, to encourage people to just do it

Its not WHAT you do, its HOW you do it
It wont get perfect, just better