Any successful/unsuccessful tales of loading a large Coax in a front horn?

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I've heard Altec 15" coax in the A7 box, which would be a sort front horn. Works well. Loads to about 200Hz, IIRC.

Have also heard Lowther fullrange in a big horn. Seemed to work extremely well. The Lowther shout was absent, which is good.
 
What I have is a pair of these Electro Voice EJ1 horns and 12" Tannoy dual concentric drivers out of the V12's. I'm thinking of mating them up - Once I get them together and do some measuring I'll get a better idea of what I'll need to do to get them tuned in with the crossover. What I'm afraid of is the 12 may not go up high enough to meet the compression treble due to the increased loading of the low mid in the horn. If i can get it right it may be a lot of fun to listen to. 🙂

EV EJ1 Theater horn

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CCsQFjAE&url=http%3A%2F%2Fwww.electrovoice.com%2Fdownloadfile.php%3Fi%3D971761&ei=7VEbVdydF4WkgwSaw4CADw&usg=AFQjCNEPO7YUosfVB8EiopOFUrO4ruKqoA&sig2=eFsJBj5zRPUAa7ZWTbA1tw&bvm=bv.89744112,d.eXY&cad=rja
 
Pano said:
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Have also heard Lowther fullrange in a big horn. Seemed to work extremely well. The Lowther shout was absent, which is good.
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Second that. (but I guess the available headroom is still not enough for POOH... )


About the (massive) EJ1, would it be feasible to modify it into a (big) Synergy horn?
 
The V12's have enough headroom for me when used with my current bass system - they are actually very nice drivers and could use some better cabinets. Not fully loaded horn headroom but close.

I think the synergy horns need to be exact to really work right. Hacking up these horns and guessing on the results may be a disaster for me. The Tannoys are easy and a point source to begin with. The horn throat is beautifully molded and fits a 12 with no compression or diffraction so I'm going to give it a go before hacking them up. 🙂
 
Pano said:
I've heard Altec 15" coax in the A7 box, which would be a sort front horn. Works well. Loads to about 200Hz, IIRC.
Click to expand...

+1, though it sounded s little 'pinched' to me, so when someone wanted a FLH for the 604, the large conical WG I recommended proved a winner according to him. Wish I still had all my old correspondence to see who it was, though do remember it wasn't a poster on any the early audio BBs or web forums.

It was huge, loading to a 120 Hz XO to mate to a centralized mono 'sub' system IIRC.

GM
 
POOH said:
Like a Tannoy 12 or 15 ? By loading I mean down to the upper bass or under 200 cycles.
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There is a very real point where "horn loading" a cone driver is a misnomer.
search out a radiation resistance curve and note where the knee is relative to the driver size. Beyond that point, there is no acoustic gain from horn loading although one can control directivity to a higher frequency but one risks radiating higher order stuff once the cone is acoustically much larger.

A second issue is the hf source at the center and how much of an acoustic discontinuity the transition produces and this is probably the main reason most speakers are not coax drivers.
Best,
Tom
 
Tom, that is exactly what I suspect may be the problem with what i'm going to do. The top end of the horn may not load the 12 (or not enough motor in the 12) to get it out to where it will mate with the coax high frequency. it will be easy enough to actually find out since the horn is already built. I plan on putting it together Saturday. as far as the transition in the coax itself between drivers the Tannoy is the best I've had my hands on. thanks
 
Flaesh, i already have the drivers and horns I mentioned earlier (as well as some early Synergy type horns of Tom's) so I'm more interested in working with what I have then spending money on other projects. My multi-way horn system I have been working on for 20 years is excellent - i've just the itch to try something different and maybe downsize
 
Tom Danley said:
There is a very real point where "horn loading" a cone driver is a misnomer.
search out a radiation resistance curve and note where the knee is relative to the driver size. Beyond that point, there is no acoustic gain from horn loading...
Click to expand...
Tom, where would be a good place to look for this info? Know of any charts or perhaps software that would show this?
 
Pano said:
Tom, where would be a good place to look for this info? Know of any charts or perhaps software that would show this?
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Hi Pano
There are a lot of things about horns that I have not seen written anywhere, this limitation being one of them.
You can model MANY things with AKABAK which deal with the actual dimensions and not the theoretical perfect case. While sort of pain to learn (and I only use part of what it can do), it is free and there are tutorials out there.

Remember the old days when they used to say a 30Hz bass horn would have a mouth about 10 feet in diameter or that the low cutoff was approximately where the mouth was 1 wavelength in circumference?

The reason is that at about 1 wl in circumference, one has reached the knee in the radiation resistance curve for a horn.
Beyond that point, making the horn mouth larger and larger offers no improvement in efficiency (but can confine the radiation angle which can appear to be gain in efficiency but isn’t).

But what that curve didn’t say was that there was no point or gain from having a mouth smaller than that.

A generalized curve from the interweb;
http://www.cummingsdesign.com/Benwin/images/Figure1.jpg

The unspoken thing in that curve is that at the upper frequency end, there is no additional horn loading once the radiator is already large enough to have reached that knee.
The importance of this became crystal clear trying different sized drivers in the Unity and Synergy horns, here, a 5 inch cone driver can efficiently drive a horn up to about 1000-1200Hz or so. Size matters when playing with these acoustic resistances.

The real point of a horn (so far as efficiency goes) is to couple the acoustically small driver far to the left of center of that graph to the big end’s constant radiation resistance to the right side.

As a result, it is entirely possible to “horn load” a cone driver and get little or no increase in electro-acoustic efficiency and the same thing is what (one of the things) governs the efficient band of most compression drivers.

I was asked to write about loudspeakers a good while back, in a book I have had past editions of for ages. I wouldn’t have accepted otherwise (I am not a writer) and even with Doug’s help, it was something like passing a watermelon through ones colon when finished.
The past edition had a superb, very encompassing chapter on loudspeaker’s so I tried to explain more and spent some extra time things like back emf and on horns if interested (and I did write about this issue as I recall). Anyway, it’s the 5th edition of “Handbook for Sound Engineers”
Best,
Tom
What’s new out your way?
 
Thanks Tom for the thorough answers. :up:
I don't understand too much about horn loaded cones, so always good to get more info. I suppose that Hornresp could be helpful, too.

Tom Danley said:
Remember the old days when they used to say a 30Hz bass horn would have a mouth about 10 feet in diameter or that the low cutoff was approximately where the mouth was 1 wavelength in circumference?
Click to expand...
I suppose that I still live in that world. :xeye: But again, cones seems different.
What’s new out your way?
Click to expand...
Gotten away from horns at the moment, gone Open Baffle. Works well in the lava tube cave I have for a listening space.
 
In hornresp, making sim of cone driver and mid horn (with big throat) almost always gets a very narrow response.

Shrinking the throat might help with the higher range but efficiency suffers. Hard to get a decent response on the screen.

In reality, the response is not like that. In such cases, hornresp can't properly predict the response of the driver itself which is not supported by horn.
 
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