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Old 25th June 2009, 08:01 PM   #1
widi is offline widi  Spain
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Default My first measurements Justmls

Hello friends, this is my first time I'm doing measurements justMLS and although I read the manual and I've been looking through the forums, I need your help to know that I am going in the right direction.
The hardware used for measurements is:
Targeta Esi juli@ sound.
microphone preamp M-Audio mobile pre usb.
Behringer EMC8000 microphone.
20W amplifier.
Jig, which I built, designed by John K., this is where the link is: http://www.htguide.com/forum/showthr...6&page=1&pp=35
Images of these measurements are:
http://img.villagephotos.com/p/2009-6/1342104/0

I hope your comments

Thanks in advance.
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Old 26th June 2009, 07:58 AM   #2
widi is offline widi  Spain
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Please someone I might lend a hand, if I'm not doing the measurements?
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Old 26th June 2009, 01:10 PM   #3
Shaun is offline Shaun  South Africa
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It looks right. I'd say that the data below 500Hz is invalid, as that is likely system or other noise. Usually the bottom end is tailed off to reconstruct the actual (theoretical) low end response.

See here Measuring Phase Response of Drivers
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Old 26th June 2009, 03:05 PM   #4
widi is offline widi  Spain
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Quote:
Originally posted by Shaun
It looks right. I'd say that the data below 500Hz is invalid, as that is likely system or other noise. Usually the bottom end is tailed off to reconstruct the actual (theoretical) low end response.

See here Measuring Phase Response of Drivers

Thanks Shaun
May be due to 14uF capacitor that I have to protect the tweeter?.
If something is worth what I put the capacitor in the tweeter's negative not to interfere with the jig.
It is also correct to connect the capacitor?.
Greetings.
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Old 26th June 2009, 07:30 PM   #5
Shaun is offline Shaun  South Africa
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Using the capacitor to protect the tweeter is fine, as long as the reference point is on the driver side of the cap. But, as you have seen, it consequently degrades the signal-to-noise ratio at the lower frequencies. If you are confident of controlling the signal level to the tweeter you could try it without the cap. But I have no experience testing the limits of what drive levels a tweeter can safely tolerate, so I won't make any recommendations. I recently stopped using a series capacitor for frequency response measurements... but only because I discovered that the tweeter was still undamaged after accidentally testing it without the cap a few times.

BTW, I use SoundEasy.
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Old 26th June 2009, 07:57 PM   #6
widi is offline widi  Spain
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Hi Shaun, I do a test without a capacitor protection, and have low signal happens.
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Old 26th June 2009, 08:37 PM   #7
Shaun is offline Shaun  South Africa
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It is not clear what you mean by that statement. Do you want to try saying it another way, or perhaps try posting a pic?
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Old 26th June 2009, 08:49 PM   #8
widi is offline widi  Spain
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What I want to say is that I will try without the tweeter capacitor.

Sorry for not explaining well.
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Old 26th June 2009, 09:37 PM   #9
Shaun is offline Shaun  South Africa
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Just by the way:

I find that generally there is a S/N problem at the very low end, because all the equipment in the test chain usually have a roll-off at the low (so it is compounded). At some point I would like to use a DC-coupled amp to improve matters, or at least an amp that starts to roll off at only around 5-10Hz...
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Old 26th June 2009, 10:58 PM   #10
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Quote:
Originally posted by widi
What I want to say is that I will try without the tweeter capacitor.

Sorry for not explaining well.
As long as you place your reference probe after the capacitor, the measurement will be the same as without it.

Regards,

Dennis
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