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Old 29th November 2013, 07:34 PM   #341
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Quote:
Originally Posted by peteleoni View Post
You apparently saw no reason to reinvent the wheel and you did not.
Well, definitely. There are no real high-tech devices in most loudspeakers, yet the basic technologies used are pretty good for what they do.

Linear motors are positionally accurate, so probably the best (open loop) technology for driving the diaphragm or cone. Horns are impedance matching and directional control devices, so good for an interface between the diaphragm and air. Resistors, coils and capacitors, well, those are almost axiomatic. Some capacitor technologies are more linear than others, but most of the differences are in the dielectric. Good poly caps and air-core coils are generally as good as it gets, although I've seen a lot that favor oil-filled caps, and as long as they don't mind the size and potential for leaking, I wouldn't dissuade anyone from going that route for home hifi.

But yeah, I tend to be more in favor of implementing the best technologies available in audio rather than to try and promote a "novel invention." That didn't stop me from making a few new things though, like an injection mold for my H290C waveguide/horns, patented cooling plugs/plates for my hornsubs, etc. So I guess there have been a few cases where I didn't see what I wanted available on the market, so I designed and produced my own.

As for the horns, though, I'm just saying I do see merit in using the OS/EC flare profile - the hyperbola created from a line drawn tangent to an elliptic cylinder or oblate spheroid. I think it provides a nice, smooth transition from compression driver exit to the "main body" of the horn. It gives nearly constant directivity and lowest high-order modes of all flare shapes.

What I don't agree with is the policy of using that flare profile without regard to any other attribute. I've seen some pretty bad horns with that basic flare shape. It's usually because the coverage angle and/or aspect ratio was too small or too large, sometimes exacerbated by using a secondary flare to radius the mouth. It's not that any of those things is bad, in and of itself, sometimes quite the opposite - they're good. But what seems to have been lost on some designers is the fact that not all horns provide good response. Size and shape matters, and not just for directivity, but also for sound quality and smoothness of response.
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Old 29th November 2013, 07:35 PM   #342
gedlee is online now gedlee  United States
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Originally Posted by Omholt View Post
But don't worry, you can contact me. Yup, a self exclaimed expert on small room acoustics.
That's true of everyone around here.

Ps. its "self proclaimed"
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Old 29th November 2013, 07:44 PM   #343
gedlee is online now gedlee  United States
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Originally Posted by boldname View Post
Is there any useful reports on the effectiveness of these that you could tell us about.
There are several patents on this concept from decades ago. It does not prove to be very practical, even though in theory it should work. You could, for example, make a waveguide from a block of foam. That way the HOMs would enter the foam and get absorbed while the direct wave would just move down the axis normal to the foam and not get absorbed (maybe a little).

Trouble is that now this block of foam has to be many times larger than the waveguide which is cut into it - so say about 1 m^3. That is hard to "package" and would cost more than $500 to buy the block of material even before the costs of cutting the waveguide. Ouch! A bit hard for me to see being commercially viable.
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Old 29th November 2013, 08:07 PM   #344
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Originally Posted by gedlee View Post
You could, for example, make a waveguide from a block of foam. That way the HOMs would enter the foam and get absorbed while the direct wave would just move down the axis normal to the foam and not get absorbed (maybe a little).
What would "guide" the wave if the horn is an absorber?
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Old 30th November 2013, 02:36 AM   #345
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I guess once one starts to get wise to "the speaker game" one is faced with a moral dilemma. Bite your tounge or spoil someone's game. Don't know how some of you guys do it, but I really appreciate those who have set me straight with nothing but freinds to lose for your trouble. Much gratitude. If you guys always bit your tounge the would be nowhere to walk.
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Old 30th November 2013, 03:08 AM   #346
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I'll take some solitary opinions of many of the guys who hang here over some collective opinions.
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That's true of everyone around here.

Ps. its "self proclaimed"
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Last edited by peteleoni; 30th November 2013 at 03:14 AM.
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Old 30th November 2013, 04:50 AM   #347
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Noted and interesting: In my room, with both the Sentry III (a 3way CD horn speaker) and the dsp- ed SP-1 (two way CD all horn speaker) you can be virtually on top of them with *zero* loss of driver integration and ideal imaging. I find this very interesting as it may lay a myth aside. The common feature is a similar large HF horn. One hears a lot about driver disintegration and large rooms being required for large horn speakers. I have a feeling this may not always be the case (other than fitting them in (-: ...)
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Old 30th November 2013, 08:24 AM   #348
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Oh and dont stress to much about time alignment dear, its no.big deal....Acoustic Radar.
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Old 30th November 2013, 03:06 PM   #349
gedlee is online now gedlee  United States
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Originally Posted by markus76 View Post
What would "guide" the wave if the horn is an absorber?
Hi Markus - holiday here and not on line as much.

The wave would be guided by the change in acoustic impedance at the boundary. This would not be simple, but it can be analyzed. Its simply a different boundary impedance at the walls - simple to say, very difficult to analyze. So while there would be some form of "guide" it would act very different than a rigid wall. And no I don't have a good feeling for how it would work.

A wave that propagates along a boundary tends to see the boundary impedance as much higher than it actually is. But there is still a small "leakage" into the surface and this will warp the wave front. Its difficult to guess at how much effect this would have.

But the idea of changing the walls surface texture will not result in much effect at all unless the texture is very thick.
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Old 30th November 2013, 05:56 PM   #350
Pallas is offline Pallas  Pakistan
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Originally Posted by markus76 View Post
What would "guide" the wave if the horn is an absorber?
FWIW, as a little project to play with I recently bought a pair of cool-looking vintage B&O mini-speakers with good-condition cabinets but rotten woofers that I'm going to update and use to work on passive crossover design.

That's relevant here because the tweeter is a 1" soft dome from Seas with a conical "waveguide" made entirely out of what feels like a sponge.

Apologies for my wretched photography skills that all of the processing an iPhone 5S can muster barely improve, but here are some pics:

Guide over tweeter in cabinet:
Click the image to open in full size.

Guide out of cabinet, front:
Click the image to open in full size.

Guide rear:
Click the image to open in full size.

Interestingly, most of the pics I see online of the Beovox C75 show a tweeter with a phase plug like structure in front of it, and a plastic waveguide surrounded by the sponge.
Click the image to open in full size.

I ordered Omnimic yesterday because it can do the one important thing FuzzMeasure can't - render polar maps. When Omnimic comes in I'll take some polars of the tweeter in sponge-guide to see what the sponge-guide does, assuming Omnimic works OK over Parallels. Measurements without sponge-guide strikes me as less than useful, because then the tweeter is recessed into a rectangular hole.
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Last edited by Pallas; 30th November 2013 at 05:59 PM.
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