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Multi-Way Conventional loudspeakers with crossovers

Geddes on Waveguides
Geddes on Waveguides
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Old 17th August 2017, 05:50 PM   #7691
gedlee is offline gedlee  United States
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Quote:
Originally Posted by miero View Post
Can you explain a little bit why do you not recommend this, if we are considering scenario with a passive crossover, please?
Let me soften my statement to: "I would prefer to not lower the efficiency of the woofer." I can see that there might be good reasons to do that, but my preference is to not do so. I could envision changing this position.

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Originally Posted by mabat View Post
I know you will be disappointed but it's just some interpolation of the input data. So the more angles you measure the more resolution you have. I don't remember exactly how it's done and I know it is not really correct but it helps me to see some things more easily anyways. It is still nice enough tool for me
Polar maps are an essential tool in good loudspeaker design. I will not take any design serious that does not show this kind of data. (Un-normalized as you and I do. Normalization obscures almost everything that one is looking for.)

That said, there are good and bad ways to do this. What happens when you interpolate polar data is that it tends to average out the diffractions because they are dips that change in frequency with angle - kind of like arcs in the response (the classic example of this can be seen in my simulation of a vibrating cap in a sphere in polarmap on my website.) Resonances, which do not change with angle get shown quite readily even with interpolation. This is why in your example the resonances are shown quite effectively, but the diffractions are not seen.

My technique avoids this problem since no interpolation is done in an angular sense. The radiation "modes" are extracted and then the polar response is reconstructed at whatever angular resolution one wants. There is some interpolation in frequency but none in angle (we have 1000's of frequency points, but typically only a few angular ones.) This technique is the same as that Klippel is currently using in his new system. He does this in three dimensions and I only bothered with two, but the techniques are otherwise identical. (And both derive from the work of Prof. Weinriech at Michigan in the 50's.)
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Old 17th August 2017, 07:12 PM   #7692
badman is offline badman  United States
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Originally Posted by gedlee View Post
Let me soften my statement to: "I would prefer to not lower the efficiency of the woofer." I can see that there might be good reasons to do that, but my preference is to not do so. I could envision changing this position.
Similar idealism about preserving bass efficiency here, but as you say, there are good reasons to try it- maybe you want a dB or two extra bump around Fc or want to manage amplifier load, or the padding can smooth the impedance to simplify XO design.

Pads integrate well into series crossover design, too, which some prefer (regardless of perceived/analyzed value of different XO topologies), always nice to have options.

In this case, I'd rather have a better top end, I generally prefer smaller diaphragmed drivers crossing higher for that extension/smoothness, but I'm still in my 30s, it may be less of an issue for our older friends with more HF losses in hearing.
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Old 17th August 2017, 09:41 PM   #7693
Paul W is offline Paul W  United States
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IIRC (it's been a long time) adding series resistance to a woofer raises the Q, which usually requires a larger box.
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Old 17th August 2017, 10:51 PM   #7694
ScottG is offline ScottG  United States
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IIRC (it's been a long time) adding series resistance to a woofer raises the Q, which usually requires a larger box.
-it's particularly useful for free-air/dipole midbass designs where the low-pass uses a cheaper inductor (smaller gauge windings with more resistance) to net a bit more gain lower in freq.. (..starting of course with a more efficient driver with a Qe typically around .5.)
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Old 17th August 2017, 10:54 PM   #7695
badman is offline badman  United States
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Originally Posted by Paul W View Post
IIRC (it's been a long time) adding series resistance to a woofer raises the Q, which usually requires a larger box.
Higher Q lower Vas I believe, so box size can remain similar.
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Old 17th August 2017, 11:17 PM   #7696
gedlee is offline gedlee  United States
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The only thing that changes is the Qes, all other parameters will stay the same. Only Qes contains Re.
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Old 19th August 2017, 06:40 PM   #7697
larsaskogstad is offline larsaskogstad
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Hello, new to this forum.

gedlee: Just came by the NA12 design but noticing you dont sell anything anymore ?

Where do I get the waveguide/"horn" from? Where should the crossover be on that design? Would you let me know?

Sent you an mail earlier today.

- Lars
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Old 19th August 2017, 06:56 PM   #7698
jcx is online now jcx  United States
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Default people are now printing them

3D printing 1/2 of a waveguide
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