3"or 4" driver with very good dispersion and high xmax? - Page 42 - diyAudio
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Old 28th February 2014, 11:52 PM   #411
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This is unfortunately (one of) the problems inherent to driver testing -the lack of industry-standardised test equipment, methodologies and definitions.
And the lack of an anechoic chamber in every backyard.

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Old 1st March 2014, 02:12 AM   #412
dewardh is offline dewardh  United States
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And the lack of an anechoic chamber in every backyard.
That is a minor annoyance, isn't it.

I'm fortunate in having access to a "quiet room" that permits a 25 ms gate, but it involves working around the facility schedule and trucking in and setting up (and then removing) all the gear, including 12' pole stand and all the rest. And a modest fee. It only gets done if it matters . . . I wouldn't bother testing a driver other than on the baffle it's going to be used with, for example, since that's the only data that can't be accessed elsewhere that is of any real use in the design process.
 
Old 1st March 2014, 02:15 AM   #413
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Where in Berkeley did you find a quiet room? I think Etcheverry Hall has a huge underground room where the teaching nuclear reactor used to be
 
Old 1st March 2014, 03:04 AM   #414
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You don't need an anechoic chamber for accurate measurements. By gating, taking nearfield measurements and splicing nearfield and farfield data, you can get quite an accurate picture of the frequency response. These techniques have been well documented in several texts. In fact, a gander around the internet should produce enough information for anyone to learn the techniques. For those who believe otherwise, please educate yourself.
 
Old 1st March 2014, 03:11 AM   #415
dewardh is offline dewardh  United States
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Where in Berkeley did you find a quiet room?
The ballroom at the City Club (gets some traffic noise from Bancroft), and the Large Assembly Room at FCCB. Both at night, of course.

Last edited by dewardh; 1st March 2014 at 03:20 AM.
 
Old 1st March 2014, 03:18 AM   #416
dewardh is offline dewardh  United States
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By gating, taking nearfield measurements
Where do you place the microphone to get 60 degree "nearfield" measurements on a dipole?
 
Old 1st March 2014, 03:48 AM   #417
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Nearfield implies omnidirectional response. Dipole response in the HF is no different than directional response from regular forward firing speakers. If you have directional response in the low frequencies, outdoor measurements or ground plane techniques could be used. You can raise the speaker off the ground as well to get clean reflection-free response.
 
Old 1st March 2014, 07:08 AM   #418
dewardh is offline dewardh  United States
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Nearfield implies omnidirectional response.
Yes, that's the theory, isn't it.

But what we're talking about here is taking off-axis measurements of real devices to determine when . . . scratch that, "when" is always . . . to determine how they deviate from what "theory" dictates. When you are making real measurements of real drivers the first thing that goes out the window is "theory" . . . that's why we measure, after all.
 
Old 1st March 2014, 11:42 AM   #419
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Marcus must have the patience of Job.

Why has this gone on for 400 posts? Round and round... If the man wants only data, give him data or don't post (this post doesn't count).
I agree but it's obviously too much to ask for. As a result moderation will close this thread.
 
Old 1st March 2014, 12:02 PM   #420
Mooly is offline Mooly  United Kingdom
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As this thread has been causing much work for the moderation team lately, this thread is now closed.
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