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Multi-Way Conventional loudspeakers with crossovers

Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?
Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?
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Old 12th September 2019, 04:13 AM   #2911
ScottG is offline ScottG  United States
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Quote:
Originally Posted by camplo View Post
You guys are alright by me....
-don't just settle for the "optimized" result.

Play with volume and vent freq.. A LOT.
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Old 12th September 2019, 04:21 AM   #2912
mabat is offline mabat  Czech Republic
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Originally Posted by Ro808 View Post
Widening of the wavefront is not the purpose of an OSWG. I guess minimizing/elimination the narrowing, the on-axis null and interferences at the mouth were areas of concern.
Dr. Geddes has opted for an asymetrical mouth, whereas mabat optimized the throat to mouth transition.
Please, correct me if I am wrong.
It is the need for smooth termination and I suppose that holds for every horn. There should not be an edge, IMO. Then we can talk about the degree of edginess. Curve such as clothoid offers virtually none - you won't find any order of "edge" there. There will still be a mismatch of curvatures at a (flat) baffle junction however. Ideally the baffle would match curvature around the horn as well, although I'm still not sure that unbaffled but rolled-back horn would be better. At least for an infinite baffle this final curvature mismatch doesn't seem to make much trouble. "Inside" the horn it will be much more important.

Last edited by mabat; 12th September 2019 at 04:31 AM.
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Old 12th September 2019, 04:31 AM   #2913
AllenB is offline AllenB  Australia
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Originally Posted by mabat View Post
for every horn.
Some horns keep opening continuously, and yet they terminate very well. However there is a downside when it comes to fitting them into a room.
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Old 12th September 2019, 04:35 AM   #2914
mabat is offline mabat  Czech Republic
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Yes, that I would call a smooth termination. Only the room gets in the way
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Old 12th September 2019, 04:39 AM   #2915
GM is offline GM  United States
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Pretty much, that's what it's designed for.

'808' ?

Unless it's changed, full size cinema uses a 120 Hz XO Vs HT's 80 Hz, so ~30 Hz Fs driver is fine, ditto adding true subs, but when I responded earlier I was just answering Qs in auto mode.

But seems I saw where you're planning to use a 700 Hz XO on a driver best suited to ~ 500 Hz and maybe only ~350 Hz if planning on using all its Xmax.

I've never had the luxury of > ~ 4 mm, so frequency modulation distortion [FMD] might be an audible issue, i.e. the cone/surround distortion Scott mentioned, especially in a quiet setup like you plan.

GM
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Old 12th September 2019, 05:11 AM   #2916
camplo is offline camplo
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GM did you just use sarcasm....lol.
I say 630hz but if I try 500hz and like it, I won't likely change it....you have to think, I really want the horn to play to 200hz, so of course I am going to push the limits or at least try. At the 70-90db of normal listening the xmax is about non existent. When I'm modeling at 116db, the sealed 15M hits 3xmax at 90hz, so to follow the 3xmax best practice for critical listening, I'd cross no lower, I thought 100hz made sense.

HXDXW
84x14x23

I intend to put the mid point between the horn and mid woofer at ear level which is 48" (sitting in my fav chair) and the width of the front baffle matches the 23" of the horn, and the depth has been minimalized, causing less resonance on the most important plane.
OMG is this really coming together, shipping as soon as next week you guys, then I'll stare at the drivers for another month before enclosures get done lol!

GM - yeah 808....you know, the bass drum sound from the roland 808, the booom booom you heard and just about every rap song ever?



So here's a thing, can you guys name off some reference material you like to use for home theater system appraisal??

Last edited by camplo; 12th September 2019 at 05:22 AM.
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Old 12th September 2019, 05:29 AM   #2917
docali is offline docali  Germany
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Originally Posted by gedlee View Post
I stated that wrong above. No linear function of x could become infinite in a finite x, so it would likely be something like a Tan function, but still pretty simple.

But I agree that this kind of waveguide termination makes a lot more sense than a simple radius - which has an instantaneous change in slope at the junction. I wish that I had thought of this before.
Such a modification of the horn contour is at least known since more than 50 years. Manfred Harsdorff, Zeiss Ikon, filed a patent about the modification of the exponential horn and imho in a more coherent way by modifying the original horn formula to receive a smooth termination into the mounting plane and to shorten the horn. He also provided a figure of the resulting impedance curve.
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Old 12th September 2019, 05:35 AM   #2918
AllenB is offline AllenB  Australia
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Originally Posted by mabat View Post
Yes, that I would call a smooth termination.
Does it depend on how much (enough) axial distance you have to design the waveguide?
Quote:
Only the room gets in the way
Directivity is the purpose of a waveguide.
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Old 12th September 2019, 05:46 AM   #2919
docali is offline docali  Germany
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Originally Posted by mabat View Post
It's exactly a clothoid (aka Euler spiral), i.e. a curve that has linearly increasing curvature along its length. It is actually quite hard to compute with

Euler spiral - Wikipedia

I believe there are other options of suitable curves - even a whole classes of splines. I chosed clothoid. The first one who suggested it to me was Dr. Bohumil Sıkora, Czech audio guru (I think he has an account here as bobolix). It was the BEM simulation that helped me to realize how much of the horn contour this curve can really take.
It is actually quite easy to compute the Cornu spiral. For this you need to solve the Fresnel integrals which can be solved by a simple series expansion, so a single loop in the program code. The problem with this series expansion is that it tends to diverge for larger angles but I have found that this does not play a role for this use case as the determining function angle remains in a region where the series expansion converges very fast.

I am curious about the observation field view (wave fronts) of your big wave guide you presented from lowest to the highest frequencies. Can your wave guide be used as free-standing? It seems that the simulation uses the infinite baffle trick which hides many of diffraction issues, so we are able to assess this.

Quote:
Originally Posted by whgeiger View Post
1) At the point of inflection the radius of curvature of both curves should match.
2) You can implement this profile, and others as well, with a single fairness curve. [1]
3) Check out the profiles generated by shape optimization regimens. [2]
4) The declining curvature in the throat, gently spreads a higher pressure wave front.
The increasing curvature at the month mitigates lower pressure wave reflectance.
WHG
Thanks for sharing this! The Bezier Curves look really promising for some uses I have in mind but I need to dig into this bunch f formulas
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Old 12th September 2019, 05:53 AM   #2920
mabat is offline mabat  Czech Republic
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I also looked at how to incorporate the termination flares into one equation for the whole countour (and I'm talking about OSWG) but is it not really nedeed - it's only a matter of convenience. For me the OS contour is a must as I can't stand beaming sources anymore - the collapse of stereo image, etc. Once you get used to a properly done constant and narrow directivity, there's no way back. So the question for me is how to terminate OSWG the best possible way and I see no much better way than how I do it now. That's all.

Quote:
Originally Posted by docali View Post
I am curious about the observation field view (wave fronts) of your big wave guide you presented from lowest to the highest frequencies. Can your wave guide be used as free-standing? It seems that the simulation uses the infinite baffle trick which hides many of diffraction issues, so we are able to assess this.
It is not a "trick", it is an examination of the waveguide for that conditions, i.e. without the influence of a particular box. It's allways better to start with a better waveguide itself.

Of course you can use it free-standing and it will get much worse. No point about that. You could make a roll-back then, i.e. to let the spiral continue (and maybe even change the scale around the circumference which is quite easy to do). I would have to prepare a complete 3D simulation for that. I have it on my list but not quite on the top.

Last edited by mabat; 12th September 2019 at 06:18 AM.
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