Multi-tone audio testing?

[Devon Howard]

Hello all. Newbie here. Listened to multi tone for first time today (seven, from 20 Hz to 6k) and was startled by how much the proportions varied as I moved about the listening room. It's a very quick test of overall response, more revealing than white/pink/brown noise. Generator was the mediapunk iPhone app. Not knowing much physics, I set frequencies according to known musical pitches rather than harmonic obscurities!

 

[pkane]

By popular demand, I started a beta-test thread for my multi-tone analyzer software:

https://www.audiosciencereview.com/...t-multitone-loopback-analyzer-software.27844/

 

[Music1969]

Hi @pkane

I am trying multitone measurement with my ADI-2 feeding Cosmos ADC.

I know for a fact I'm doing something wrong because this is nothing like Amir's APx555 but can you spot what could be wrong?

Looks really wrong < 600 Hz

 

[pkane]

Hi @pkane

I am trying multitone measurement with my ADI-2 feeding Cosmos ADC.

I know for a fact I'm doing something wrong because this is nothing like Amir's APx555 but can you spot what could be wrong?

Looks really wrong < 600 Hz

View attachment 193301

View attachment 193300

Switch to Rectangular FFT Window and no overlap. Or use Chebyshev 200 window with 87.5% overlap and see if it looks any better. To get a better resolution at lower frequencies, you can also try to increase FFT size.

 

[Music1969]

Switch to Rectangular FFT Window and no overlap. Or use Chebyshev 200 window with 87.5% overlap and see if it looks any better. To get a better resolution at lower frequencies, you can also try to increase FFT size.

Thanks!

I just noticed Amir's was tested with 32bit PCM192kHz

I wonder if he did 16/44.1 or 24/44.1 it would look like mine above.

With 24/384k it gets better for me (still some things to improve).

Rectangular wasn't as good as this.

 

[pkane]

Thanks!

I just noticed Amir's was tested with 32bit PCM192kHz

I wonder if he did 16/44.1 or 24/44.1 it would look like mine above.

With 24/384k it gets better for me (still some things to improve).

Rectangular wasn't as good as this.

View attachment 193304

Better. But 44.1k should also work. Here's rectangular window @ 44.1kHz:

And here's Chebyshev window @44.1kHz:

 

[Music1969]

Better. But 44.1k should also work. Here's rectangular window @ 44.1kHz:
View attachment 193323

And here's Chebyshev window @44.1kHz:
View attachment 193321

Ok will try now.

With REW, I'm getting decent expect results like this but occasionally as I'm viewing the spectrum I see (like for J-test below):

For 9 of 10 seconds I have the perfect expected J-test result but 1 in 10 seconds I get this.

Is this normal using spectrum RTA ?

Or should it be fairly constant without such (glitches?)

 

[Andysu]

462 tones from speakers:

View attachment 60374

x12 fbq 2496 per channel of , way too much bit would neatly get the eq of the speaker/s mic up closely nicely tuned ironed out , like sandpaper on wood to even out the imperfections of each speaker driver but 12U of each x12 i guess like having a once cray supercompter as this would take up a lot of rack tower cabinets , i think their is a peq that can cover all those bands and maybe a lot more at very, very cheap price as even with x12 fbq would cost new £ 2220 , just to get the any speakers drivers near close flat within fractions of dB

you can only dial in 20 peq each ch or loop ch a to b then you have 40 ch but still can only dial certain about of peq bands . i not gone though all the peq bands see how many there are there is a lot . but for 15.12.6/8 of fbq in my system would be staggering £ 77,700 , yikes !

 

[Music1969]

Hi @pkane

I don't seem to be able to get rid of this downward slope from 20 to 100Hz

Have you ever seen something like this in REW?

I'm using Cosmos ADC at PCM38kHz

cc @IVX

 

[Music1969]

Ok I needed a much larger FFT, the max !

 

[Music1969]

Struggling with why my dBFS signals are so low.

In REW I set RMS dFBS to the most to avoid peak going over 0 dBFS, around -10dBFS

 

[thulle]

Struggling with why my dBFS signals are so low.

dBFS input depends on voltage of the input signal and the voltage setting on your ADC.

 

[pkane]

Struggling with why my dBFS signals are so low.

In REW I set RMS dFBS to the most to avoid peak going over 0 dBFS, around -10dBFS

Change the range input in Cosmos ADC if the output voltage from your DAC is not matching the ADC input.

 

[Music1969]

Change the range input in Cosmos ADC if the output voltage from your DAC is not matching the ADC input.

Ah shit - good point.

If I wanted to know the actual range of signal above noise/distortion from multitone , the plot above gives approx. 90dB range (140dB minus 50 dB).

If I match voltages, the range will be identical right? It's just the absolute numbers will be different?

And also SNR and THD+N calculations will still be the same?

And also - how to do? In REW itself?

 

[pkane]

Ah shit - good point.

If I wanted to know the actual range of signal above noise/distortion from multitone , the plot above gives approx. 90dB range (140dB minus 50 dB).

If I match voltages, the range will be identical right? It's just the absolute numbers will be different?

And also SNR and THD+N calculations will still be the same?

And also - how to do? In REW itself?

Mostly the same. Remember that ADC isn't perfect and may have different THD+N at different input levels. Considering that Cosmos is adjusted by Ivan to perform best at -0.5dBFS, I assume you'll get best performance out of it if your input matches that range. But the differences aren't going to be major if ADC is measuring at -10dBFS.

If you want to scale the maximum value on the REW plot to 0dB. just select dBc display option.

 

[Music1969]

Considering that Cosmos is adjusted by Ivan to perform best at -0.5dBFS, I assume you'll get best performance out of it if your input matches that range.

Thanks!

How to do it? I need to install those special files that adjust interpolation filters etc, right?

 

[pkane]

Thanks!

How to do it? I need to install those special files that adjust interpolation filters etc, right?

No, the range settings are on the bottom of the ADC, little toggle switches. Just select the pattern that best matches your DAC output voltage. Use a wooden toothpick or something that isn’t going to scratch or damage the switches — they are plastic, so be careful applying any force.

 

[Music1969]

No, the range settings are on the bottom of the ADC, little toggle switches. Just select the pattern that best matches your DAC output voltage. Use a wooden toothpick or something that isn’t going to scratch or damage the switches — they are plastic, so be careful applying any force.

Oh shit, I didn't even look at the underside.

Thanks for the scratching/damaging tip !

I'll need to think hard how I do this

 

[Music1969]

So my Cosmos ADC is already set to 4.5V

My DAC outputs fixed maximum 4.3V, so it would appear there's nothing for me to change?

Or should I reduce it on the ADC (even though my DAC spec is 4.3V) so that 0dBFS tone does play at -0.5dBFS

If my DAC spec is 4.3V and Cosmos is set to 4.5V already, why is 0dBFS file I created 10db down below 0 ?

 

[pkane]

So my Cosmos ADC is already set to 4.5V

My DAC outputs fixed maximum 4.3V, so it would appear there's nothing for me to change?

Or should I reduce it on the ADC (even though my DAC spec is 4.3V) so that 0dBFS tone does play at -0.5dBFS

If my DAC spec is 4.3V and Cosmos is set to 4.5V already, why is 0dBFS file I created 10db down below 0 ?

Keep it at 4.5v.