Here's My Usher/Altec Horn Loaded Open Baffles...

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#64
Roofing is my livelihood but I hadn't ever thought of incorporating it into speakers. I was just curious.

The type IV EPS (styrofoam) might be an interesting idea but 1/4" will be hard to handle without breaking. Can you even buy 1/4"?

#30 felt I think you will need multiple layers.

Bitumen based will be smelly. Big gas off with it.
 
#66
Hi Cal,

I totally forgot about the out gas smell from Bitumen - thanks for the reminder! 😉

I don't know if I can find 1/4 inch Styrofoam but there should be something around similar. Gee - I would hate to cut up a bunch of tops off of egg cartons. :clown: The guys at the local grocery got a little mad the last time I tried!! :bigeyes:

Hmm - I'll need to look around and see what I can find. It only needs to be strong enough to support the baffle and that weighs in at around 5 - 10 lbs. (2 - 5 kilo).
 
#68
#69
Cal Weldon said:
Hi Chops,

You only need to damp one of the lips. The sectoral fins couple the other. There is very little ringing in any other part of the horn.

Use wet towels. 🙂
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My 511B horns ring very little when thumped. Even less now that they are mounted to the baffles. I highly doubt any ringing could be heard over the music being played as it would have to be fairly loud to make them ring in the first place. I have had these horns for nearly two years now and not once have I heard any ringing coming from them.
 
#70
As for the foam or felt, I would not be doing it for isolation reasons. If anything, it would be an attempt to eliminate baffle defractions and reflections.

As it is, the 0.75" MDF baffles and 2x4 bracing seems to be doing a pretty good job of keeping vibrations down to a minimum.

Think of my foam/felt idea like using foam and/or felt around a tweeter on some speakers.
 
#73
chops said:
My 511B horns ring very little when thumped.
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Did you tap them on the lips? That's where you get the ringing. The sides just seem to thud, not really ring. The mounting flange doesn't really damp the lips.

I highly doubt any ringing could be heard over the music [/B]
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I agree, I think the cowbell nickname is overrated.

and not once have I heard any ringing coming from them. [/B]
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Nor have I when music was used to excite them.

I just use a bag of wet sand to hold them in place as much as reduce the ringing. Mine aren't securely fastened, just resting on cradles and a slot board.
 

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#74
For me, it's not so much the ringing as it is edge diffraction. There is something not good going on where the sound leaves the horn mouth. There is probably something else happing in the gaps and spaces between the back of the horn flare and the front of the baffle. Putting some soft material there sure helps.

But oh well, I've told a number of people about this before, including Chops, I even started a whole thread about it - but almost no one seems to take it seriously or even care. Too bad. I simply do not understand the reluctance to trying such a simple, reversible mod, but it's their loss, not mine. :scratch:
 
#75
My understaning is that it's a mouth edge diffraction issue as the wavefront hits the edge, there is an impedance discontinuity and some of that enegy returns to the throat. The towels would create a diffuse edge and reduce and absorb this I would think. Try it with towels (duct tape the lower one on) and maybe try an aesthetic version with cotton waste sewn into a sausage shape like a door draught excluser. With a bit of thought there would be ways to design this in so it looks 'factory'.
 
#77
Brett said:
My understaning is that it's a mouth edge diffraction issue as the wavefront hits the edge, there is an impedance discontinuity and some of that enegy returns to the throat. The towels would create a diffuse edge and reduce and absorb this I would think. Try it with towels (duct tape the lower one on) and maybe try an aesthetic version with cotton waste sewn into a sausage shape like a door draught excluser. With a bit of thought there would be ways to design this in so it looks 'factory'.
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Between restoring the Klipsch Cornwalls back to factory spec (getting them ready to go on the market) and doing a few other chores around the house today, I've managed to take some towels and drape them around my horns. This is what I've come up with so far...

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I have to admit, I do believe there's an improvement. I can't really pin-point it, but there is a difference.

What I'm thinking about doing is going to the local Ace hardware store and picking up some weather stripping. They have it there in 1x1", and less than 2 bucks! Not to mention I can get it for 20% less since I work there! 😀 It's soft open cell foam and I can somehow stick it to the inside rim of the horns. If I do this, would it also be wise to line it along the vertical edges of the sectoral fins as well, or jsut around the lips? Can I go with smaller stripping and still have it be effective?
 
#78
chops said:
I have to admit, I do believe there's an improvement. I can't really pin-point it, but there is a difference.
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There you go, Chopper! That's the trick. You're right, it's hard to put finger on the change. Do both top and bottom, you'll get twice the effect but it will still be hard to define. Listen to it for a few days with 4 towels in place, then take them off. You'll really notice.

What I hear is that the sound is drier, more matte. Sounds like something is missing. Since there is nothing directly in the path of the sound wave - what is missing can only be bad. Can only be stuff that doesn't belong in the signal. -- Like distortion.

Not sure what your plans on insulation are, but the idea is to make the transition from horn to open air less abrupt, as Brett mentions. Filling up those dished out cavities can't hurt, either. I did try that round black foam insulation that is used on pipes. Covered it with faux fur and put it on the edges of the horn lips. I don't think it worked nearly as well as the towels. So it may be that the transition area need to be large.


BTW, I don't remember ever seeing an OB rig that was WMW with a horn. Would that be WHW? So you may be trail blazing after all, Chops!
 
#80
Neat project!

I would recommend Mortite rope caulk, 2-3 layers pushed tight on the 511's exterior. It will make a difference. There is a ringing going on with the music, (i have used 511, 203 (best altec imo), 311, 811 nad multi-cells) you'll notice it once it's gone. Also mount the horn with 2-3 layers of mortite. That should cut the ringing down a bit more.
 
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