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Multi-Way Conventional loudspeakers with crossovers

May my problem be diffraction?
May my problem be diffraction?
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Old 11th March 2020, 12:00 AM   #21
AllenB is offline AllenB  Australia
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May my problem be diffraction?
Quote:
Originally Posted by andreaemme View Post
Of course, 'baffle-less' was to be intended 'without' any baffle around.
I think, how can you answer your original question unless you can find the way to produce the least amount of diffraction. This way you can see what is truly the tweeter's fault.
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Old 11th March 2020, 12:28 AM   #22
boswald is offline boswald  United States
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May my problem be diffraction?
There is no magician;

"pay no attention to the man behind the curtain!!"

As Steve likes to remind us, it helps to have an idea.

You have the tools, and have learned to use them, but you need to study what has worked with what components in what conditions. and find satsfactory explanations of why a given technique worked in its instance.

It might help to read a few books that give an overview, remember, you can have a garage full of tools, but lacking an understanding of valve timing, expansion coefficients, etc. you will be unlikely to successfully build a Ferrari V-12.

I'm sorry that it's not plug-and-play, but audio is squishy.
We have waves responding differently to various materials(air, the structure and furnishings of the room), and it all changes with the shapes of the room(and speaker) and wavelengths of the sounds.

Don't be discouraged, it's just not instant.
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Old 11th March 2020, 05:47 PM   #23
joetekubi is offline joetekubi  United States
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Originally Posted by AllenB View Post
This is not how you do it. If you want to remove the baffle you'll want to use a large baffle.
Thank you. Words of wisdom and experience.
Ref: Augsburger, Olsen, Beranek, etc.
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Old 11th March 2020, 06:15 PM   #24
andreaemme is offline andreaemme  Italy
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Quote:
Originally Posted by boswald View Post
There is no magician;
...cut...
It might help to read a few books that give an overview, remember, you can have a garage full of tools, but lacking an understanding of valve timing, expansion coefficients, etc. you will be unlikely to successfully build a Ferrari V-12.
...cut...
Don't be discouraged, it's just not instant.
Thank you! I've already read Vance Dickason's cookbook and D'Appolito's about measuring loudspeakers, can you suggest any other book about crossover design please?

However, I've just found something that certainly is going to become another milestone in my learning way. It's the Michael Chua article on his project Starling TA in which he demonstrates that speakers which are not time aligned have phasing issues which can clearly be heard in the sibilance. I think my project have so two kind of problem, diffraction and time misalignment, maybe more the second one. Time alignment sounds well even when response curve is not perfectly flat, and viceversa a curve perfectly flat can sound harsh and sibylating if not time-aligned.

What exactly is "time alignment"? I can control drivers' phases in simulations, are drivers time-aligned when phases overlap perfectly around crosspoint?
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Old 11th March 2020, 08:00 PM   #25
RobWells is offline RobWells  United Kingdom
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I've got the 2 books you mention above. The D'Appolito one is good but for me personally the best book I've read is Floyd Toole Sound Reproduction

It isn't about building speakers as such but it has really helped me with setting them up once built.

Rob.
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Old 13th March 2020, 08:21 AM   #26
andreaemme is offline andreaemme  Italy
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Regarding Time ALignment theory, I reviewed my measurements and cross-point between SS D2905-9500 and Vifa TC9FD18 and discovered this (measurements took at 25 cm to lower diffraction influences):

SS filtered response:
SS.png

Vifa filtered response:
Vifa.png

total response:
final.png

SS + Vifa overlayed:
Vifa+SS.png

Now I'm even more confused because I don't understand why at cross-point relative phase is quite exactly 180 while tweeter and mid has already inverted polarity and in fact total response if goos at cross-point and doesn't reveal any dip (foolishly I didn't take null-reverse mesasurement).

Please can somebody explain what does it mean this 180 shift?
Thank you very much.
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Old 13th March 2020, 08:36 AM   #27
YSDR is offline YSDR  Hungary
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Quote:
Originally Posted by andreaemme View Post
Please can somebody explain what does it mean this 180 shift?
Are you using an USB mic with ARTA? That would explain the phenomenon. With an USB mic like UMIK-1 or similar, the timing is unreliable from multiple measurements. Of course you can do a reverse null test because it takes just one measurenent instead of two or more.
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Old 13th March 2020, 08:55 AM   #28
andreaemme is offline andreaemme  Italy
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Originally Posted by YSDR View Post
Are you using an USB mic with ARTA? That would explain the phenomenon. With an USB mic like UMIK-1 or similar, the timing is unreliable from multiple measurements. Of course you can do a reverse null test because it takes just one measurenent instead of two or more.
No, I use a Dayton 'normal' mic with an analog preamp and a sound-card for A/D conversion. May it be because I've made single channel measurements? (I wasn't able to make dual channel because of erroneous results)
Thanks
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Old 13th March 2020, 09:12 AM   #29
YSDR is offline YSDR  Hungary
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Anyway, the individual phase rotations looks similar, the combined response is flat and roughly -6 dB at the xo point. I bet the reverse null test would show a deep symmetrical cancellation.
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Old 13th March 2020, 09:40 AM   #30
andreaemme is offline andreaemme  Italy
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Originally Posted by YSDR View Post
Anyway, the individual phase rotations looks similar, the combined response is flat and roughly -6 dB at the xo point. I bet the reverse null test would show a deep symmetrical cancellation.
I was happy of this before to listen but..... sonically result is a ruin
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