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Old 8th May 2012, 12:59 AM   #21
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Quote:
Originally Posted by bear View Post
Also, while the tests are interesting, I am wondering about the transition between the compression driver's short exit/throat and the throat of the horn. If there is a discontinuity there - the angle changes - then you may have a place where there is diffraction. Might be effecting the distortion and the HF response. Wondering about that.

_-_-bear
As stated in post # 1, I spent a great deal of time an effort insuring all horns have a smooth transition at the throat.

Having tested a few of the drivers on some other horns, I would be quite surprised if you could find another horn with less distortion at similar output levels.

At any rate, all drivers used the same horn type, which has the same or slightly greater throat angle than the drivers.
Any horn traits are equally reflected in all the responses.
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Old 8th May 2012, 01:48 AM   #22
Pano is offline Pano  United States
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Thanks Art - Positive and Negative dB, got it! 0dB is referenced to 4 volts, right?
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Old 8th May 2012, 12:40 PM   #23
Pano is offline Pano  United States
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Art, I'm not sure everyone understands what you've done here, there is a lot of info. It's a very clever test, so let me see if I can rephrase it:

Six different compression drivers were tested on the same model horn. Two crossover points were used, 630Hz and 1250Hz. There was no woofer! The woofer is "virtual" having been edited into the sound files from the original source (low passed).

Art made the recordings of the drivers on the horn, only. Then in software he added the bass from the original file, after it had been low pass filtered to match with the horn. Therefore, the woofer is "perfect" - only the compression drivers change.

The compression drivers were run at different drive levels to test their distortion. That recording was normalized and combined with the bass portion. So everything you hear in the test results is at the same volume, just the drivers and their distortion changes. You would not be able to do this with direct listening! A very clever test.

Does that about sum it up?
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Old 8th May 2012, 01:30 PM   #24
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Great - n - Thanks

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Old 8th May 2012, 07:22 PM   #25
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Quote:
Originally Posted by Pano View Post
Art, I'm not sure everyone understands what you've done here, there is a lot of info. It's a very clever test, so let me see if I can rephrase it:

Six different compression drivers were tested on the same model horn. Two crossover points were used, 630Hz and 1250Hz. There was no woofer! The woofer is "virtual" having been edited in the sound files from the original source (low passed).

Art made the recordings of the drivers on the horn, only. Then in software he added the bass from the original file, after it had been low pass filtered to match with the horn. Therefore, the woofer is "perfect" - only the compression drivers change.

The compression drivers were run at different drive levels to test their distortion. That recording was normalized and combined with the bass portion. So everything you hear in the test results is at the same volume, just the drivers and their distortion changes. You would not be able to do this with direct listening! A very clever test.

Does that about sum it up?
Yes, Pano, that mostly sums it up.

In addition to your summation, test recordings were also made with dual sine wave tones at different drive levels and RTA screens of each have been posted, making it possible to see the distortion you can hear.
Also, an inverse distance test was performed so one can estimate throat SPL at any given test SPL level.

Dual VHF tones (above most human's hearing) were also tested to see if they resulted in lower frequency audible distortion.

All the information is either in the first post, or footnoted at the bottom of post #1 as to where it may be found.

All in all I’m glad I performed the 50.25 hours of testing, but the 84.75 hours it took to mix, analyze, write up and post the findings got more than a bit old. A total of 135 hours of unpaid work in the project, while I had answered my own main questions in the first two days of testing a month ago.

As the hours of mixing and writing slowly unfolded, I often regretted mentioning on line that my “High Frequency Compression Driver Evaluation” was forthcoming .

But as a man of my word, I slogged along until done, with no short cuts, the “Full Monty” has been posted .

I appreciate the thanks and interest shown by the respondents thus far.

Art Welter
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Old 8th May 2012, 08:40 PM   #26
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An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used to compare the output of various HF drivers all fitted to the same type horn.
Ed Kabotie Freedom Songs - DreamCatcher.com

The specifics and SPL level of each music recording are in post #1 "Tests" section.

The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.


Art
Attached Files
File Type: zip 1AdsLo+3.zip (123.9 KB, 12 views)
File Type: zip 1An10630.zip (567.3 KB, 5 views)
File Type: zip 1Ap1063.zip (546.9 KB, 8 views)
File Type: zip 02dsHi+3.zip (211.1 KB, 5 views)
File Type: zip 02dsLo+3.zip (132.1 KB, 4 views)
File Type: zip 02n10630.zip (540.7 KB, 7 views)
File Type: zip 50n1063.zip (564.2 KB, 8 views)
File Type: zip 50p10125.zip (562.2 KB, 8 views)
File Type: zip 52a0125.zip (537.7 KB, 7 views)
File Type: zip 52a1063.zip (522.9 KB, 7 views)
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Old 8th May 2012, 08:51 PM   #27
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An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used to compare the output of various HF drivers all fitted to the same type horn.
Ed Kabotie Freedom Songs - DreamCatcher.com

The specifics and SPL level of each music recording are in Post #1 "Tests" section.
This post contains the last of the sound files listed in Post #1.

The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.

Art Welter
Attached Files
File Type: zip 52a1363.zip (596.3 KB, 12 views)
File Type: zip 52n10630.zip (565.2 KB, 5 views)
File Type: zip 52p10125.zip (560.1 KB, 5 views)
File Type: zip 82n10630.zip (593.3 KB, 8 views)
File Type: zip PAdsMid+3.zip (200.4 KB, 6 views)
File Type: zip PAp312.zip (581.6 KB, 5 views)
File Type: zip PAp612.zip (581.6 KB, 6 views)
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Old 9th May 2012, 04:23 PM   #28
ErnieM is offline ErnieM  United States
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Thanks for all the work!

I've learned quite a bit over the years from your posts. It's a treat to be able to hear direct comparisons in a well thought out controlled test.
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Old 9th May 2012, 05:17 PM   #29
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Quote:
Originally Posted by ErnieM View Post
Thanks for all the work!

I've learned quite a bit over the years from your posts. It's a treat to be able to hear direct comparisons in a well thought out controlled test.
Thank you, Ernie.

Even though I recorded the tests a month ago, the editing allowing the direct comparisons at the same levels was only finished a few days ago.

I look forward to hearing others opinions of the various driver's sound.

Art
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Old 10th May 2012, 07:20 AM   #30
ErnieM is offline ErnieM  United States
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I listened to all the music samples including horn only....and I have to agree with your conclusions. The bms drivers would do well crossed over high. I liked their top end detail. It was a toss up for overall sound between the b&c and ev. They really do sound quite similar when eq'd. Though as mentioned the ev goes louder cleaner.

It would be nice to see how the big BMS and B&C models do. Also 18 Sound of course. Too bad they're all quite expensive...

I did the horn only test awhile ago with my DE250's. It didn't sound so smooth after that.
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