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Multi-Way Conventional loudspeakers with crossovers

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Old 21st August 2010, 06:45 PM   #7271
g3dahl is offline g3dahl  United States
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From what I have seen of the polars on the AH-425 (Augerpro's and my measurements with the GPA driver, and Bjorn's BEM simulations), I'm pretty comfortable with the 700 Hz crossover. The polar pattern is set by the horn, not the driver, so I don't feel like I am operating in the dark. Both the horn and woofer are at soft parts of their dispersion curve, so I don't think it's especially critical. Of course, I could be mistaken. I'm more concerned with trying to stay about an octave away from the AH-425's lower limit and the TD15M's issue at 1.5 kHz and above.

The horn mouth reflections are easily seen in the wavelet graph, and I wouldn't be surprised if it improved with the use of beach towels and/or pipe insulation, but there's going to be a reflection from the top of the TD15M cabinet anyway, even if I take steps to minimize its effect. I'm going to work with them in their current form and evaluate the results with my ears.

I do wonder about one thing, though. The wavelet ripples at 0.6 ms intervals correspond to distances of about 8 inches. The depth of the AH-425 on axis, without the driver, is 10 inches. The inside wall of the horn measures about 16" from the bugscreen to the edge of the mouth, so I'm not sure of the exact mechanism that is causing the 0.6 ms ripples.

Also, I was surprised at the comment about the AH-425 measuring "poorly" (on the referenced LeCleac'h horn thread). Can someone point out a horn/driver combination that measures better under similar conditions?

I don't like what I see above 10 kHz, of course, and am placing blame on the Radian. I don't know of any 1.4" driver that does better, though; any driver that size is in breakup mode by that time. And all of the other driver/horn combinations I have seen measurements of have a much lumpier response in the 700 - 10,000 range (let me know if I'm missing something). Lynn still believes that my G3 ribbons will be useful here, but if they don't work out, there are other drivers out there that are good at the top octave.

Gary Dahl
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Old 21st August 2010, 08:01 PM   #7272
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I know what you mean Gary, I just prefer to have my own measurements with the actual devices I'm going to use. I especially like to have good details on what's going on far off axis--something no one posts. Personally I wouldn't worry too much about the stuff over 10kHz.Click the image to open in full size.
If I didn't have a graph of that top octave issue, I wouldn't know there was one. YMMV, however it may not.

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Old 21st August 2010, 08:11 PM   #7273
g3dahl is offline g3dahl  United States
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Hi Dan,

Which horn/driver combo is that?

Gary Dahl
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Old 21st August 2010, 08:27 PM   #7274
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Don't know. I believe the tweeter may be made by Vifa and the waveguides by EAW. The speaker is a Mackie HR624 mkII.
Click the image to open in full size.
Mackie HRmk2 Applications

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Old 21st August 2010, 08:41 PM   #7275
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Quote:
Also, I was surprised at the comment about the AH-425 measuring "poorly" (on the referenced LeCleac'h horn thread). Can someone point out a horn/driver combination that measures better under similar conditions?
Hello Gary

Depends of you design criteria. It's not a CD horn so in that respect there may be better but CD is not part of design criteria so it's a moot point. I wouldn't worry about. Get it up and running to hear what's going on. Over 10k
you are going to get some loss of detail put the overall upper octave balance shouldn't be that bad on axis.

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Old 21st August 2010, 08:59 PM   #7276
mige0 is offline mige0  Austria
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Quote:
Originally Posted by g3dahl View Post
I do wonder about one thing, though. The wavelet ripples at 0.6 ms intervals correspond to distances of about 8 inches. The depth of the AH-425 on axis, without the driver, is 10 inches. The inside wall of the horn measures about 16" from the bugscreen to the edge of the mouth, so I'm not sure of the exact mechanism that is causing the 0.6 ms ripples.

Gary Dahl
My guess: its possibly not from the horn.
Have you done those measurements with the horn hanging on a string from ceiling?
If not, maybe you repeat in such a setup to make sure no reflecting surfaces whatsoever are close by (you horn mount, the mid speaker cabinet ...)


Michael

Last edited by mige0; 21st August 2010 at 09:10 PM.
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Old 21st August 2010, 10:01 PM   #7277
Elias is offline Elias  Finland
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Hi,

From the horn honk thread one of the best performers was Jean-Michel's J321 + TD2001

Click the image to open in full size.



Compare this to my test with 20€ Peerless dome in a test baffle:
Click the image to open in full size.

Baffle edge diffractions can be seen at about 0.6ms, 1ms and 2.5ms,


Consider also an attempt to remove baffle edge diffractions and hang the tweeter in free air by wires from the ceiling: And now there was diffractions from wave travelling around the tweeter itself.
Click the image to open in full size.



One cannot escape diffraction with little effort only! It will allways be there with certain amount.

- Elias


Quote:
Originally Posted by g3dahl View Post
...
Also, I was surprised at the comment about the AH-425 measuring "poorly" (on the referenced LeCleac'h horn thread). Can someone point out a horn/driver combination that measures better under similar conditions?

I don't like what I see above 10 kHz, of course, and am placing blame on the Radian. I don't know of any 1.4" driver that does better, though; any driver that size is in breakup mode by that time. And all of the other driver/horn combinations I have seen measurements of have a much lumpier response in the 700 - 10,000 range (let me know if I'm missing something).
...
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Old 21st August 2010, 11:57 PM   #7278
doug20 is offline doug20  United States
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Originally Posted by g3dahl View Post
Also, I was surprised at the comment about the AH-425 measuring "poorly" (on the referenced LeCleac'h horn thread). Can someone point out a horn/driver combination that measures better under similar conditions?
FWIW, Paul W. built a pretty good MTM speaker that had rave reviews during a DIY event in Atlanta.

It uses the 18sound wavguide (XT1464)/1.4 CD (ND1460A). I think its breakup was up past 14KHz.

The measurements are here.

HTGuide Forum - View Single Post - The Raptor ... a 10" MTM

Last edited by doug20; 21st August 2010 at 11:59 PM.
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Old 22nd August 2010, 01:26 AM   #7279
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by g3dahl View Post
...

I do wonder about one thing, though. The wavelet ripples at 0.6 ms intervals correspond to distances of about 8 inches. The depth of the AH-425 on axis, without the driver, is 10 inches. The inside wall of the horn measures about 16" from the bugscreen to the edge of the mouth, so I'm not sure of the exact mechanism that is causing the 0.6 ms ripples.

...
Gary Dahl
45 deg tangent point before the lip is how far from the horn throat on axis?
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Old 22nd August 2010, 01:55 AM   #7280
g3dahl is offline g3dahl  United States
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Quote:
Originally Posted by doug20 View Post
FWIW, Paul W. built a pretty good MTM speaker that had rave reviews during a DIY event in Atlanta.

It uses the 18sound wavguide (XT1464)/1.4 CD (ND1460A). I think its breakup was up past 14KHz.
Those measurements look great. I remember looking at that driver, but the manufacturer's curve didn't look nearly so good. Is that an unequalized measurement?

If so, and if it is compatible with the AH-425, it would definitely be worth a try!

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