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Multi-Way Conventional loudspeakers with crossovers

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Old 26th April 2013, 11:31 PM   #6031
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Default MOAS etc.

Quote:
Originally Posted by gedlee View Post
There is an entire section in my book on why we don't want mouth reflections and how best to mitigate them with a flare. Nothing that you are saying here is new (to me at least). We don't want any mouth reflections - period.
I know that most of my prose here are a "choir preach" for you or maybe the source of an eye-roll as well; but here, the audience is much more diverse, so I try to keep it understandable to all.
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The best mouth flare differs in the "free" case from the "baffled" case. I only use the baffled case so the Euler curve is not appealing. One can hypothesize on the idea flare into a baffle, but in the end they all look an awful lot like just a radius.
That is Hughes’ approach to the horn neck as well. I thought other methods were preferred.
The baffle is finite as well, so yet another diffraction edge is to be encountered.
Why not integrate the two?
In the case of in-wall installation, where the baffle is materially infinite, spiral segment transform may still be used. Have a look at how they are used in roadway design for some ideas [1].
[1] http://www.oregon.gov/ODOT/HWY/GEOME...wayspirals.pdf
Quote:
In my waveguides, the complete lack of any extraneous impedance bumps on the driver’s electrical input impedance is a pretty good indication that the mouth flare works well.
I am not surprised and suspect the design has a lot of lab-work sweat all over it.
Ear plugs still remain standard issue when working there. See [2] below for a fellow who forgot his.
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There is one frequency at which the reflections at the mouth edges creates a standing wave across the mouth - but not back down the horn - and this results in the axial hole seen in a round waveguide.
How the mouth is handled is critical to any design and the place where I see most horns fail.
Regards,
WHG
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Old 27th April 2013, 08:24 AM   #6032
soongsc is offline soongsc  Taiwan
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It seems that when we look at various design approaches, it's best to evaluate from many expects in terms of measureable result. For example, directivity, distortion, amplitude & phase, CSD, etc.

Up to now, I think wave guides definitely have god potential, but the profile really depends on driver characteristics.
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Old 27th April 2013, 10:13 AM   #6033
AndrewT is offline AndrewT  Scotland
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Is there a difference between a "spiral" and an involute.
Involute - Wikipedia, the free encyclopedia
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Old 28th April 2013, 12:15 AM   #6034
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Default Yes,

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Originally Posted by AndrewT View Post
Is there a difference between a "spiral" and an involute.
Involute - Wikipedia, the free encyclopedia
but it can be a sprial as well.

Logarithmic Spiral Involute -- from Wolfram MathWorld

Last edited by whgeiger; 28th April 2013 at 12:16 AM. Reason: typo
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Old 2nd May 2013, 01:46 AM   #6035
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So considering a 6.5" cone midrange, what size WG would typically offer an ideal directivity match to say 3-3.5khz?
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Old 2nd May 2013, 02:43 AM   #6036
soongsc is offline soongsc  Taiwan
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terrible thought
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Old 2nd May 2013, 12:17 PM   #6037
gedlee is offline gedlee  United States
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Quote:
Originally Posted by mayhem13 View Post
So considering a 6.5" cone midrange, what size WG would typically offer an ideal directivity match to say 3-3.5khz?
You would have to post the polar response of the midrange, otherwise its just a guess. I don't like to guess.
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Old 2nd May 2013, 12:21 PM   #6038
AndrewT is offline AndrewT  Scotland
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How do you use the polar response to determine the parameters of the waveguide?
How much does the resulting WG need to be altered as a result of testing the proposal?
Or does "it Sounds Right" mean it is "Right".
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Last edited by AndrewT; 2nd May 2013 at 12:43 PM.
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Old 2nd May 2013, 01:23 PM   #6039
gedlee is offline gedlee  United States
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The only waveguide parameter that you have at your disposal is the coverage angle (the throat radius is fixed by the compression driver). This is set to match the angle of coverage of the driver just below the waveguides operating band.

The other option, which is what I do, is make a waveguide, measure it and the woofer and set the crossover point at where the two match.

But the question specified the crossover point, at that frequency the "midrange" polar pattern will be fixed, so the only option is to modify the waveguide design to match the midrange at the specified crossover. That's not the way that I would do it.
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Old 2nd May 2013, 01:29 PM   #6040
AndrewT is offline AndrewT  Scotland
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But he is using a cone driver.
Can you convert your description to determining the WG parameters that will suit the polar response of the cone driver?
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