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

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#83
Cal Weldon said:
I'm guessing the ringing is much worse with the cast aluminum horns than with something like the 1803's?

Oops, OT again, sort of.
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I had the 1503 and they rang a bit- not tar filled but tar coated- also had the Dukane 803 that were very heavy tar filled with 2" throat for JBL drivers. They were better.

The multicells are cool but they sounded funny sitting as close as I have to. Like little fingers of beam shooting out at me.

An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
 
#84
As I said before, I am not concerned about the horns ringing. I'm lucky if I'm putting a full watt into the Altecs at full tilt, and 1 watt is not going to be enough to get these horn ringing. And if they did, they're not going to be ringing louder than the music coming out of them. I have never heard any ringing coming from these horns, so as far as I'm concerned, this is a non-issue for me.


Now what I am concerned about is the mouth edge diffraction issue. Just from draping the towels over the top edge and sides, I hear a difference, or rather an improvement. This is what I'm concerned about.

So with this issue, I am thinking that closed cell foam would be a better choice than open cell foam to mount on the edges of the horns. If this is the case, would 0.75"W x 0.50"H closed cell weather stripping be large enough to cut down on the mouth edge diffraction?

And IF I do this, would it be better to put the weather stripping around each sectoral section, fins included?
 
#86
Magnetar said:



Ok - Enjoy!!
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Hey, sorry, but it's not my fault everyone is going on about something I never mentioned.

My horns do not have welds in the fins, just black silicone. Apparently they are the later ones that Altec produced to eliminate this so-called "ringing". Hence why this is a non-issue to me.

I've ONLY been asking about the mouth edge diffraction issue which everyone has been seemingly avoiding.
 
#88
I'm not even sure what that means. 😕

As for edge diffraction, I doubt anyone is avoiding it, most of us just don't know. All I know is that the towels works for me, the little pipe insulators did not work as well.

Way back when there were some Iwata horns that used a series of slots along the edge of the horn lips to ease the impedance transition. Mr. Iwata had developed the edge slots for bullet train tunnels in Japan. But I can't find any trace of documentation for this method.

Earl Geddes has also discussed using open cell foam inside the horn throat to kill "High Order Modes" or HOM. A different matter, but a similar problem. I think you're going to have to experiment some to find what works best. I would, too, but my OB/horn rig is down for the moment. My feeling is that the bigger and softer the area of treatment, the better the results. Like felt rings for tweeters. But that's only a guess. There was a photo of foam on the fins just a few posts back, right?
 
#90
panomaniac said:
I'm not even sure what that means. 😕

As for edge diffraction, I doubt anyone is avoiding it, most of us just don't know. All I know is that the towels works for me, the little pipe insulators did not work as well.

Way back when there were some Iwata horns that used a series of slots along the edge of the horn lips to ease the impedance transition. Mr. Iwata had developed the edge slots for bullet train tunnels in Japan. But I can't find any trace of documentation for this method.

Earl Geddes has also discussed using open cell foam inside the horn throat to kill "High Order Modes" or HOM. A different matter, but a similar problem. I think you're going to have to experiment some to find what works best. I would, too, but my OB/horn rig is down for the moment. My feeling is that the bigger and softer the area of treatment, the better the results. Like felt rings for tweeters. But that's only a guess. There was a photo of foam on the fins just a few posts back, right?
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Hmm, so you think that possibly the larger open cell foam might work better? I guess that would be right as the open cell stuff would be more likely to absorb the hash where the smaller closed cell foam would only reflect it elsewhere or not even phase it.

Then if I go with the large 1x1" open cell foam, what kind of tape should I use on the horns to attatch the foam? I'm thinking something in the lines of carpet tape. It's kind of like double-sided masking tape and not as ultra-sticky as typical double-sided 3M tape. I want this stuff to be easily removeable if need-be and not peal the paint right off the horns.

Ya know what I mean?! 😀
 
#92
I've seen and heard felt used in horn throats with very good results. It's a technique that dates back to the 30's at least. But I've never seen it on the edges. Oh, wait - yes. Some of the later Altec coax horns had foam, IIRC. Also maybe JBL and I think even Peavy do it. SOmeone here will know.

AFAIK, the idea is to make a gradual transition from the hard surface of the horn into the softness of the air. In other words, make the impedance transition as smooth and gradual as possible. My thoughts were to perhaps use window screen or some other mesh in progressively thinner layers as it moved away form the horn lip. I did a bit of experimenting with that, results were inconclusive.

It going to be trial and error to get the best results. It seems that anything that eases the impedance transition helps, foam, towels, slots, fur, etc. Find what works best will be the hard part. Don't forget to fill those big empty spaces at the top and bottom of the horn mouth. They have to be doing nasty things back and forth with the baffle.

To change the subject a bit, how is your crossover point working for you Chops? Have you tried any other points? I guess on the Rane you can't unlink the x-over frequencies or slopes, right? Just wondering if an underlapped x-over would sound good on your rig - or simply another frequency. Have you played around with that, or do you plan to?
 
#93
I'll have to see what we have in felt as well I suppose. I'll let you know what I come up with.

As far as xover point, I'm at 1kHz now and things seem to be pretty good. Unfortunately, I can't unlink the freq and slopes, but I'm working on that as well. I'm planning on upgrading to a Behringer DCX2496 to take care of that. 😉
 
#95
hey Brett

Thanks for posting that link. I read it last year sometime (I think; my memory ain't what it used to be) and for the life of me I couldn't find it again. Great bunch of condensed info on OS waveguides. I think I'm gonna buy a lathe. 🙂

Allan
 
#96
AJ said:
hey Brett

Thanks for posting that link. I read it last year sometime (I think; my memory ain't what it used to be) and for the life of me I couldn't find it again. Great bunch of condensed info on OS waveguides. I think I'm gonna buy a lathe. 🙂

Allan
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Cheers.
I'd love a lathe too but I'm so short on space it'd probably need to be in my bedroom.

Is your shed finished yet?
 
#97
Yep. The shed be built and holding up nicely in the nasty weather. I was looking at a small lathe this week that would handle WGs up to ~10" in diameter for a mere 300 bucks. I'd still have to buy the cutters and rig up a template aparatus, but I think I could do it for about 500 bucks. I'd have to re-awaken my retired machinists skills. 🙂
 
#98
AJ said:
Yep. The shed be built and holding up nicely in the nasty weather. I was looking at a small lathe this week that would handle WGs up to ~10" in diameter for a mere 300 bucks. I'd still have to buy the cutters and rig up a template aparatus, but I think I could do it for about 500 bucks. I'd have to re-awaken my retired machinists skills. 🙂
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Sounds good to me. Let me know when it's running so I can place my order.
 
#100
Thanks Brett,
It's very much the Jack's work that I'm going off of. He and I had a few emails back and forth.

Also the work of Mr. Iwata back in the 70s-80s.

I do agree that small foam is not going to do the job. The transition area needs to be large.

Chops. Looking forward to learn about what you find when you get the Behringer 24/96. It should be very handy indeed in getting things dialed in.
 
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