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Old 15th February 2013, 07:15 PM   #21
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Quote:
Originally Posted by Kindhornman View Post
Cal,
Have you done a sweep across the cells or just an individual cell?
No sweeps, sorry.
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Old 15th February 2013, 07:22 PM   #22
Pano is offline Pano  United States
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Come on Cal "When you're with a sweep you're in good company!"

Chim chiminey
Chim chiminey
Chim chim cher-ee!
A sweep is as lucky
As lucky can be
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Old 15th February 2013, 07:48 PM   #23
steve71 is offline steve71  Australia
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Quote:
Originally Posted by GM View Post
Around 180 Hz.

GM
Thanks GM! So from that plot it looks like 90 deg horizontal dispersion at 300hz. Can I assume that ._._. line represents the -6db point?

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Originally Posted by Cal Weldon View Post
If you need polar plots then befriend GM. He's our best resource here.
I've learned so much from GM's posts over the years. He help me a ton with my current bass horn. Back then I had a relative visiting that taught me a lot about wood working, so I kind of had a dead line with the design.
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Old 15th February 2013, 08:02 PM   #24
steve71 is offline steve71  Australia
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Originally Posted by weltersys View Post
Bass horn beam width at 300 Hz will be largely dependent on the horn throat angle, not the mouth angle.
My PA uses optional waveguides which extend the 26.5 wide 90 degree horn to 53 inches wide.
The dispersion remains a uniform 90 degree pattern, the waveguides extend pattern control about an octave lower.
This is just the type of info that I need. But it also makes me realize how little I know about horn design.

I guess with a simple conical horn, the mouth area will affect the throat angle, which is what I was seeing with hornsrep.

So if it's the throat angle, that determines pattern control, is there a formula to determine horizontal dispersion as a function of throat angle. Or can I simply go of what horns rep models, but know that I can change the expansion rate of the conical horn (after the throat) to achieve a smoother response without affecting the horns pattern?

And finally, since GM's plot shows a 90 deg horizontal pattern control from the 1003, I shouldn't have to extend the flair past the mouth. Except of course if I wanted to avoid diffraction from the non-smooth termination of the horn mouth into free air.

BTW I really appreciate the help! I'm learning a lot here.
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Old 15th February 2013, 08:19 PM   #25
steve71 is offline steve71  Australia
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Originally Posted by Kindhornman View Post
Weltersys,
The use of the wings you are talking of would also lower the effective loading of the horn mouth and this would be another advantage of using such extensions.
I think I understand what your saying. Basically you'd be loading the CD to a lower frequency. But if the horn already loads to 180hz and I'd be crossing higher, would it be necessary?

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Originally Posted by Pano View Post
Having "Been there, Done that" you'd have to define "nice".
To sum up a few years of work and pulling my hair out:
  • Q: Why would you want to cross that low?
  • A: Because I want to cover as much as I can with the horn.
  • Q: Why with the horn?
  • A: Because it sounds better than the woofer.
  • Q: Does it really? Or do you just think it does?

I found that it does not. That is probably not entirely the fault of the horn, the compression driver is important, too. Even with the robust Altec phenolic drivers like the 291 "Giant Voice" running that low does not sound great. Remember that at some point output will drop and distortion will skyrocket. You want to stay far away from that point, unless you are using very steep crossover slopes, which have their own problems.

After a lot of experiment, measurement and listening, I've found that 1.4" drivers are just better sounding crossed at ~600Hz or higher. Although they will play lower on the right horn, you do need the extra octave (or more) below the crossover point to stay out of high distortion. Even if they will play down that low, you probably don't want to use it for high fidelity.

Honestly, most good 15" woofers sound better in that range than the compression drivers. Placing the crossover point where it actually sounds best, not where we hope it will sound best, is best practice.
It took me years to learn that.
I had always thought that I could cross lower since the 1003 was a 300hz horn and a was using a steep x-over slope and this was for home use. But I don't claim to be correct, I didn't take an measurements etc. With the active crossover, I just did an A/B comparison and the 300hz x-over was noticeably better sounding. But that could just mean my bass horn had issues playing up past 300hz. I never did get around to bracing it properly.

My crossover is a three way active digital unit (Gauss 1502 on top, then the 288 and then the 515G), but I guess I could do a front loaded 10" horn to cover 600-200hz and then *passively* cross to a folded bass horn under that. A folded bass horn should be good to 200hz, right?

What do you guys think of that approach? Come to think of it, time alignment might be a problem using an passive x-over with two horns of vastly different path lengths... hmmmm. Comments?

Are their any existing mid/midbass horns designs that will cross well to the 1003 at 600hz? I would rather build from an established design, than try to reinvent the wheel
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Old 15th February 2013, 08:30 PM   #26
steve71 is offline steve71  Australia
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Originally Posted by Kindhornman View Post
I didn't want to get into a verbal joust so I kept my mouth shut. In pro-audio PA applications this is why I originally developed cone driver mid-range horns to cover this region. The sound of a compression driver that low at any kind of level is just not a nice sound.
Sorry if my post came across as argumentative. I was just speculating as to why we had two different experiences.

I don't know enough about horns to argue anything.

My ideas for these speakers are not set in stone. I would like to use a lot of what I have laying about, but apart from that I'm going to do what you guys suggest. If I question something, it's not because I think I'm right and you're wrong, I'm just trying to understand and learn.

I'm lucky enough to have a pretty big budget with this project, but that doesn't not automatically make me knowledgeable, or grantee a great out come.

I'm going to be building 6 or 7 of these speakers, so I want to get it right.
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Old 15th February 2013, 08:31 PM   #27
steve71 is offline steve71  Australia
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Quote:
Originally Posted by Pano View Post
Come on Cal "When you're with a sweep you're in good company!"

Chim chiminey
Chim chiminey
Chim chim cher-ee!
A sweep is as lucky
As lucky can be


As long as my drivers don't go "chitty chitty bang bang"
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Old 15th February 2013, 08:47 PM   #28
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Old 15th February 2013, 09:04 PM   #29
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Default altec mid bass horn

Quote:
Originally Posted by steve71 View Post
.....Are their any existing mid/midbass horns designs that will cross well to the 1003 at 600hz? I would rather build from an established design, than try to reinvent the wheel

Hi there S: The Altec A7 used a bass horn attached to the 15-inch driver with an 8-inch slot, and was produced to be used with either 800 or 500 cross 0ver to a compression loaded aluinum horn. The plans are available by googling-up Altec A7 VOT, look down the page aways for the dimension drawing. ...regards, Mchael...PS, I built one in 1960's.
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Old 15th February 2013, 09:17 PM   #30
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The Altec A7 was the original Voice of the Theater and for its time was a good design. We have come a long way from just trying to reproduce a simple movie track from behind a screen. Yes they were good for what they were, we wouldn't have gotten where we are today without them. But I don't think you are going to see to many A7 enclosures with a single 311 horn on the top used for high end music reproduction these days. The low frequency output of the ported horn enclosure wasn't really a great design as the port output could not really keep up with the horn gain on the 15" bass speaker. That is why they also had the A2 with a much larger enclosure and two 15" speakers.

As for a folded horn going up to 200 hz that should be an easy thing to accomplish. A three way horn system with a cone driven mid-range is going to sound much more musical and the vocal range will be much better than you will get using the compression driver down that low. This is what we all remember as the horn sound, there wasn't much you could do to get rid of that shout from the horn in the lower frequency range. I'm not one for conic horns myself, but that is more of an individual thing. I don't think that in a home system that the so called constant directivity is really that much of an issue. I will stay with exponential or hyperbolic expansions myself.
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