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Multi-Way Conventional loudspeakers with crossovers

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Old 7th April 2010, 07:17 PM   #4171
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Venture an opinion on how any of this would perform? Just wildly curious. Inspired by the ER18RNX, the MCM H-65 waveguide curves, and perhaps a bic pen. I'm having fun with Sketchup lately and am getting carried away.


Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.

Last edited by peace brainerd; 7th April 2010 at 07:32 PM.
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Old 7th April 2010, 07:35 PM   #4172
gedlee is online now gedlee  United States
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It appears to be aimed at omni-directional radiation. I am not a fan of this type of design.
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Old 8th April 2010, 12:18 AM   #4173
soongsc is offline soongsc  Taiwan
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Lots of diffraction!
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Old 8th April 2010, 12:17 PM   #4174
Rudolf is online now Rudolf  Germany
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Quote:
Originally Posted by mige0 View Post
who's to explain where *exactly* those CD behaviour can be found in the (new) SUMMA polar plot ...
Just overlay a high lighting frame on the CD area in that plot
Click the image to open in full size.

Michael,

I would call the red area above "CD". The 90 response is only 5 dB off from the 15 response (to which the curves are normalized IMHO) at the right end of the area. I believe that's not shabby at all.

The light red area would be "CD" for me too - up to about 50.

I know that you would ask about that notorious 3 kHz on-axis dip next. Let me answer with the response of two "CD" devices which are NOT waveguides, but dipoles:

First my own two Dayton ND20FA tweeters mounted back-to-back. Response is taken at 15 intervals up to 90 (red) and normalized to the power response (green line):

Click the image to open in full size.

Second "cuibono" with his baffleless B&G Neo3 and TB midrange below:

Click the image to open in full size.

In both cases you can see CD up to the on-axis-dip and beaming above that dip. The frequency of the dip is a function of the dipole length. I can show you horizontal measurements of a non-symmetrical setup for the Daytons with NO sign of that dip at all - but the vertical measurements are really bad.

With dipoles you can do a lot more experiments with CD behaviour than with WGs - its just another piece of baffle (or no baffle at all) against building a whole new waveguide. And my guess after those experiments, measurements and simulations is:
That dip is not a fault of an individual driver or baffle contour - it must be an integral part of a CD device IMHO. I know how to move that dip above 15 kHz in a dipole, but that would call for something like a real point source - useless because of the total lack of power. I know how to make that dip disappear, but it will always result in a severe loss of CD in the vicinity.

Since the dip vanishes with going off-axis, it is obviously the result of symmetry. I wonder, if Earl could give an easy-to-understand explanation (no mathematical formula please ) where it derives from.

Rudolf
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Old 8th April 2010, 03:08 PM   #4175
gedlee is online now gedlee  United States
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"CD" does not have a standardized definition, which is what allows people to define it at will. No loudspeaker could ever be completely CD across its entire bandwidth unless it was a pure omni and even that would be a design challenge.

"CD" is a target, some speakers get closer than others. And I need to point out once again that when talking about CD we need to also define the design angle intent.

Quote:
I wonder, if Earl could give an easy-to-understand explanation (no mathematical formula please ) where it derives from.
Not all the figures come through on my browser, so I am not sure what you are refering to. I would suggest that if you want me to look at data, that it be only a 50 dB scale and no more. Its simply too hard to tell anything on these huge scales that are often shown.

As too someone else's rudness being my problem, wow that's arrogant! People like that do not deserve a response.
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Old 8th April 2010, 03:33 PM   #4176
Rudolf is online now Rudolf  Germany
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Sorry, I couldn't edit post #4174 any longer, so here are the missing figures:

Click the image to open in full size.

Click the image to open in full size.
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File Type: gif summa_1.gif (27.1 KB, 311 views)
File Type: gif DaytonND20 b2b.gif (28.6 KB, 307 views)
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Old 8th April 2010, 04:24 PM   #4177
gedlee is online now gedlee  United States
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Then the dip that you are refering to is the axial dip on my waveguides? I've explained this many times, but I'll do it again.

No matter how gradual the trnsition from waveguide to baffle there will be a diffraction at this edge. In the Abbey two things happen at the same frequency. The first is the diffraction and the second is a standing wave across the mouth caused by this diffraction. These two things will always occur. Now at some frequency the diffraction from the edge will cause a cancellation directly on axis since the distances from the edge to the axial point are exactly equal only precisely on-axis. This is why it goes away off axis and why you don't see it in non-circular mouths either. In the Abbey the standing wave across the mouth also happens to have an effect directly on-axis and in the Abbey this coccurs at the same frequency as the diffraction hole. This is why the Abbey is a worst case for this axial hole. In all the other waveguides the two effects occur at different frequencies.

This axial hole will also not be seen in any waveguide that has HOM. Thats because the HOM will fill in this hole since they are at different phases than the primary mode. Only a highly coherent single mode wavefront will exhibit this hole. Its like the center spot in the shdow zone of an optically illuminated circular disk. Unless the light is coherent this spot will not be evident.
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Old 8th April 2010, 04:49 PM   #4178
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Quote:
Originally Posted by Elias View Post
You are obviously wrong. My data is 1/3 octave wavelet smoothed. Your plot shows only a poorly executed design of a 2-way box.

- Elias
Well, then most 2-way speakers are poorly executed designs. What make and model is the speaker you showed?
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Old 8th April 2010, 05:17 PM   #4179
mige0 is offline mige0  Austria
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Quote:
Originally Posted by gedlee View Post
IF the axial response does not fall then the device cannot be CD, its that simple.
Quote:
Originally Posted by mige0 View Post
That's plain wrong - as I've shown....
##################

Quote:
Originally Posted by gedlee View Post
"CD" does not have a standardized definition, which is what allows people to define it at will.
....
"CD" is a target, some speakers get closer than others..

Well spoken *in the end*, Earl
Your hindsight - assuming you feel yourself included in that bunch of people that define CD applying to their design "at will" - being actually the end of any discussion in that department IMO....





Michael
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Old 8th April 2010, 05:26 PM   #4180
mige0 is offline mige0  Austria
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Rudolf, I've seen your beautiful work on back to back tweeters .

The point on your highlighted areas is that there is - and must be - some tolerance to what we call CD.

Nothing gets "more true or the *one* truth" on earth by simply preaching / repeating any of these silly mantras. ("IF the axial response does not fall then the device cannot be CD, its that simple." - that is)


Michael
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