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Multi-Way Conventional loudspeakers with crossovers

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Old 8th January 2019, 02:58 PM   #701
mark100 is offline mark100  United States
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Join Date: Dec 2010
I figure you've already tried this...but just in case (haven't read enough of thread, sorry )

have you run a transfer of the dual channel outputs, one channel against the other...?
That's my standard 'sound card test'....
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Old 9th January 2019, 06:35 AM   #702
dch53 is offline dch53  Australia
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Join Date: Jun 2015
Location: Perth, Western Australia
Default Calibration of Soundcard Input Channels

Hi,

I'm new to ARTA, trying to see if it will meet my simple requirements for measuring amplifier frequency response and performing spectrum analysis. It could well be overkill.

I have my Juli@ soundcard setup in loopback mode; left and right outputs connected to left and right inputs. The card is setup as "ASIO 2.0 - ESI Juli@" with input channels 1/2 in Audio Devices Setup.

A test of the soundcard as per para 4.2 of the ARTA Handbook produces the result attached. Looks good and can be improved significantly by reducing the level.

I've completed para 1.5.1 Calibration of Soundcard Output Left Channel.

In para 1.5.2 Calibration of Soundcard Input Channels, the manual says: "Press the button 'Generate sine (400Hz)' and monitor the input level at bottom peak-meters".

The meters show no activity at all.

This is odd because the Juli@ control panel shows inputs and outputs at full scale.

What am I missing here?

The handbook talks about various measurement setups. I think I'd be looking to use the "Semi dual channel" setup which as I understand it eliminates soundcard artifacts from the measurements.

Is it required to tell ARTA which setup is being used? If it is, I haven't seen any mention of it.

Thanks.
loopback spectrum.pngJuli control panel.png

Last edited by dch53; 9th January 2019 at 07:00 AM.
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Old 9th January 2019, 07:35 AM   #703
thimios is offline thimios  Greece
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I have the same sound card, are you attach an a.c voltmeter to sound card line out.
Are you looking at the right chanel?
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Old 9th January 2019, 09:06 AM   #704
dch53 is offline dch53  Australia
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Quote:
Originally Posted by thimios View Post
I have the same sound card, are you attach an a.c voltmeter to sound card line out.
Are you looking at the right chanel?
Thanks for replying.

According to my True RMS DMM, with the output level set to -3dB, I'm getting 5.357V on both the left and right outputs.

I have the left and right outputs connected to the left and right inputs respectively.

I went through the instructions again. Nothing on the metres when I click Generate sinus (400Hz) but there is when I click Estimate Peak Input mv.

I've attached a screenshot.

Soundcard and Microphone Calibration.png

Another thing I've noticed is that in the Audio Devices Setup dialog, if I click the Control Panel button alongside "ASIO 2.0 - ESI Juli@", nothing happens.

I'll carry on through the manual.
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Old 9th January 2019, 09:23 AM   #705
thimios is offline thimios  Greece
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Check the windows mixer settings.
Maybe something is in mute position.
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Old 9th January 2019, 09:44 AM   #706
dch53 is offline dch53  Australia
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Quote:
Originally Posted by thimios View Post
Check the windows mixer settings.
Maybe something is in mute position.
Do the Windows Playback and Recording devices need to be set the same as the Soundcard Input and Output channels in ARTA?

I've been leaving the Windows Playback and Recording devices to Speakers and Microphone respectively.

Where the manual says "Set the left and the right line input volume to maximum" I assumed that was referring to the soundcard.
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Old 9th January 2019, 05:09 PM   #707
DualTriode is offline DualTriode  United States
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Default Standard error

Quote:
Originally Posted by Dkalsi View Post
Can anyone help me with the following issue I'm having with ARTA:

I'm trying to take gated measurements of a Woofer. I performed 4 measurements with the mic on axis with the woofer.

For all 4 measurements, no settings were changed: The mic location was kept the same, the speaker location was kept the same, same gating, same software settings....same everything.

However, my low-frequency response changes with every measurement. Anyone know why this would be the case?
Hello All,
Santa brought me some Test Tech for Christmas. I am looking to see if there is a standard input sweep voltage for measuring T/S parameters?

I do know about the issues you are talking about regarding testing woofers at low frequencies. You are windowing your sample time to exclude reflections. Using this time window the number of samples decreases as the frequency goes lower. With this decreasing sample size the statistical results will vary each time through. This is called Standard error. It is a sample size thing.

Thanks DT
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Old 11th January 2019, 07:04 AM   #708
ergo is offline ergo  Estonia
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http://www.sbacoustics.com/index.php...le/-/view/191/

SB acoustics whitepaper suggests "For a typical mid-woofer, the voltage should be about 1 V (rms)
at the resonance frequency. "
__________________
Ergo
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Old 11th January 2019, 09:03 PM   #709
rich08 is offline rich08  Slovakia
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Quote:
Originally Posted by ergo View Post
http://www.sbacoustics.com/index.php...le/-/view/191/

SB acoustics whitepaper suggests "For a typical mid-woofer, the voltage should be about 1 V (rms)
at the resonance frequency. "
I use this method, even though I described it here somewhere,
just use a 25 ohm serial resistor. I want buy 150 ohm rezistor, as use in SB Acoustics.
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Old 13th January 2019, 03:20 PM   #710
dch53 is offline dch53  Australia
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Default ARTA spectrum analysis for dummies

Hi. I need an "ARTA spectrum analysis for dummies".

I'm familiar with sampling frequency and Nyquist but my University engineering days were many years ago.

My question is, what are the best settings of sampling rate, FFT size and Window for amplifier testing?

Fs of 44100 should suffice if I'm only interested in frequencies up to 20kHz.

Below are 2 spectra of a piece of equipment. One with Fs 44100, FFT 16384, Window Kaiser 5 and Linear averaging (which seems to give the best result) and the other with Fs 192kHz, FFT 131072, Window Kaiser 5 and Linear averaging.

Why are they different? In particular why do the higher Fs and FFT result in artifacts at odd harmonics that aren't present in the other one?
Loopback spectrum -30dB 230mV earthed mu metal shield.pngLoopback spectrum -30dB 230mV FS 19200 FFT 131072.png
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