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Old 30th March 2013, 06:21 PM   #231
WrineX is offline WrineX  Netherlands
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but the foil is glued to the mylar then you plate it with tool. you use glue to keep hte shape?
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Old 30th March 2013, 07:17 PM   #232
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It is only in the ends.The alu is so thin it cant keep the shape.
I place the tool with the diaphragm in a oven at 170' for 20 minutes.
When the tool is cold ,I split it in two ,and glue the ends .

Bernt
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Old 30th March 2013, 10:21 PM   #233
WrineX is offline WrineX  Netherlands
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nice, verry nice. im looking forward to more of these amt's and the measurements of the new ones
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Old 1st April 2013, 04:14 PM   #234
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This is it:
[IMG]Click the image to open in full size.[/IMG]
Maybe the last?
Measures fine too:
[IMG]Click the image to open in full size.[/IMG]
Black is THD red 2`Harmonic.
Now I have to make one more.It sounds good too.

Bernt

Last edited by båndsei; 1st April 2013 at 04:16 PM.
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Old 1st April 2013, 04:47 PM   #235
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Quote:
Originally Posted by båndsei View Post
Black is THD red 2`Harmonic.
Now I have to make one more.It sounds good too.
Impressive
You should figure out why the distortion increases above 4kHz before you relax and stop building and only listen.
In real life the distortion are not decreasing above 9kHz like your measurement indicates.
The displayed measurement of THD will decreasing with frequency due to the way it is calculated.
With my AMTs this decreasing amount of THD shows up as the THD are falling with frequency even if the THD in real life are steady.

Your measurement indicate - THD are 30dB down at 9kHz - but I expect THD are much higher than your measurement - specially above 9kHz...

If you figure out what causes the distortion then you can relax.
The distortion can even be caused by the amplifier you use....

Last edited by RayCtech; 1st April 2013 at 05:01 PM.
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Old 1st April 2013, 06:19 PM   #236
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I use this measurement to calm me down:
[IMG]Click the image to open in full size.[/IMG]
Its the same conditions,measured with Holm Impulse.
Still, I will try another amp,and a dome tweeter for testing.

Bernt
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Old 1st April 2013, 06:27 PM   #237
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Quote:
Originally Posted by båndsei View Post
I use this measurement to calm me down:
Its the same conditions,measured with Holm Impulse.
Still, I will try another amp,and a dome tweeter for testing.

Bernt
Yes there THD decreases from 2.5kHz...
Due to the harmonics are removed step by step due to the mathematics....
So truth is => a even level of THD will show up as decreasing level above 2.5kHz... If THD shows up as a even level or increases with frequency then there are trouble..

Attached a picture showing (wrongly low distortion) THD (2nd and 3rd) of my AMT.. I understood that this was not possible, but in reality the THD was slowly decreasing up to above 20kHz.
Attached Images
File Type: jpg THD limit.jpg (104.1 KB, 307 views)

Last edited by RayCtech; 1st April 2013 at 06:37 PM.
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Old 3rd April 2013, 05:43 PM   #238
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Here is a measurement at the same conditions,for Aurasound 2" inverted dome:
[IMG]Click the image to open in full size.[/IMG]
You are right RayCtech,there are some distortíon over 5Khz.It is not the measurements tool.I have tried to change amp to a classD too.No difference,just a bit more 2`Harminic.

Bernt

Last edited by båndsei; 3rd April 2013 at 05:46 PM.
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Old 3rd April 2013, 06:19 PM   #239
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Quote:
Originally Posted by båndsei View Post
You are right RayCtech,there are some distortíon over 5Khz.It is not the measurements tool.I have tried to change amp to a classD too.No difference,just a bit more 2`Harminic.

Bernt
Looks like +20dB 2nd and +30dB 3rd harmonic before the measurement limitations fades out (down) at 9kHz.

The fact that both 2nd and 3rd harmonic are behaving identical in the measurement above 9kHz are strange as the 3rd harmonic should have decreased in level due to the measurement bandwidth limitation - at a lower frequency than the 2nd harmonic.

The 18kHz peak in the SPL measurement may indicates some kind of breakup / oscillation...
And may be the cause for the rising distortion....?

I have observed breakup / oscillation / resonance in diaphragms, in the metal / magnet assembly, in the "folding" cassette.
The breakup / oscillation / resonance in the metal / magnet assembly have I observed in branded AMTs, and then the metal / magnet assembly will emit a high frequency sound if you hit / tap it with something hard.. I have measured the emitted SPL level up to 60dB in branded AMTs that are caused by this breakup / oscillation / resonance in the metal / magnet assembly....
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Old 3rd April 2013, 07:11 PM   #240
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Here it is with 3`Harmonic
[IMG]Click the image to open in full size.[/IMG]
[IMG]Click the image to open in full size.[/IMG]
Look`s good I think.

Bernt
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