Getting around the limitations of JavaSound on OS X - Page 5 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #41 of 171 Old 01-26-14, 04:57 PM
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Re: Getting around the limitations of JavaSound on OS X

I have seen minidsp's notes but they don't answer my specific questions.
Did you try the Umik-1 yourself with OSX?

Max level is Value "1" and 40.5 dB, I will try tomorrow how this looks.

I have an (uncalibrated) SPL meter that I can compare (Voltcraft Sound Level Meter).
Did I understand correctly that the Umik-1 should be compared at 1000Hz against the SPL meter (C-weighed)
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post #42 of 171 Old 01-26-14, 05:14 PM
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Re: Getting around the limitations of JavaSound on OS X

If you have the ability to run REW in a VM, then you could compare the result on the two OS for yourself. I'll see if I can get a chance to do that today. I've been assuming that setting Soundflower to "1" and System Preferences all the way up will give unity gain at those points.
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post #43 of 171 Old 01-27-14, 07:28 AM
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Re: Getting around the limitations of JavaSound on OS X

Thanks, good to know I'm not the only person having a Umik-1 with OSX

With the setting as mentioned I read a very high SPL in a more or less quiet room.

Which leads me to my other issue, there is a big difference between my SPL meter A weighed and Z weighed (both readouts of 55 dB and 98dB in a quiet room).

This is because the Umik-1 seems to pick up a lot of low frequencies, there is about a 40 dB difference in SPL level between below and above 200 Hz, I have seen this when I did a measurement sweep with my amps switched off (so again in a quiet room).

See waterfall that I did previously.
Any ideas?

.
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post #44 of 171 Old 01-27-14, 07:33 PM
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Re: Getting around the limitations of JavaSound on OS X

Hi again, I'm not sure that you can (usefully) run a measurement sweep with your amps switched off, as REW won't be able to calculate a proper impulse response. If you are measuring ambient noise, use the RTA function. Bear in mind that USB mics are probably not the best tool for this anyway, as they are not as quiet as phantom powered mics and an external soundcard. Quiet mics = expensive...

With regard to the SPL level reported by UMIK-1, with the pink noise generator and the SPL meter, I got the same reading on the Mac with the Soundflower input level set full up (as shown in tutorial), as on Windows in a VM. I don't have a calibrated SPL meter to compare them against for absolute accuracy, the point is that the result on a Mac is the same as on Windows.

Note that the generated SPL under Windows was 3 dB higher (with the same setting in the Generator), I'm not sure why but didn't bother to track it down as it has no effect on the mic calibration/SPL reading.

Quote:
eTwin wrote: View Post
-1- System Preferences - Sound - Soundflower (2ch) - Input volume
Leave full up as shown in tutorial - http://johnr.hifizine.com/2013/02/ro...ut-workaround/.
Quote:
-2- Audio Midi Setup - Umik-1 - Sliders
As instructed by REW, set to 0 dB.
Quote:
-3- Audio Midi Setup - Soundflower - Input - Sliders
This is the same parameter as #1 above.
Quote:
-4- Audio Midi Setup - Soundflower - Output - Sliders
This is on the output side and has no effect on the mic calibration.

Hope this helps

Last edited by HifiZine; 01-27-14 at 07:51 PM.
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post #45 of 171 Old 01-29-14, 11:22 AM
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Re: Getting around the limitations of JavaSound on OS X

Hi thanks a lot (again), I think I'm getting closer.

- For me it didn't really work with a virtual machine, maybe my machine (mac mini 2011) is too slow (delays and time outs)

- In Audio Midi Setup - Soundflower - Input - Sliders I have them all full up now at 1 (40,5 dB)

- The Audio Midi Setup - Soundflower - Output - Sliders DOES influence my mic readout, so left them all three at 1 (0dB)

- What bothers me most is not so much the absolute level but more the difference in level between low and high frequencies, this is what my RTA looks like in a more or less silent room with settings as described above. Is this normal behavior? What would this normally look like?
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Last edited by eTwin; 01-29-14 at 11:31 AM.
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post #46 of 171 Old 01-29-14, 02:39 PM Thread Starter
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Re: Getting around the limitations of JavaSound on OS X

That's pretty much normal - try switching to an RTA view rather than spectrum for a less alarming presentation.
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post #47 of 171 Old 01-29-14, 04:35 PM
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Re: Getting around the limitations of JavaSound on OS X

Quote:
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That's pretty much normal - try switching to an RTA view rather than spectrum for a less alarming presentation.
Ok, so this looks right, then I don't have to worry sending back the microphone?

I still see the difference of about 40 dB, where does it come from?

I can understand there is a noise floor but why is this so much higher in the low frequencies?

Does this mean that I have to measure at about (50 + 60 =) 110dB to be able to see meaningful RT60 figures or am I mixing up things now? (ok, I know, I have to start reading the docs now )
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post #48 of 171 Old 01-29-14, 05:33 PM
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Re: Getting around the limitations of JavaSound on OS X

REW gives you T20 and T30, which is an estimated RT60. See: http://www.hometheatershack.com/room...html#rt60group

Quote:
- The Audio Midi Setup - Soundflower - Output - Sliders DOES influence my mic readout, so left them all three at 1 (0dB)
You're right, sorry, Soundflower seems to have only one volume control. I was thinking of SoundflowerBed (since I was using HDMI output)
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post #49 of 171 Old 01-30-14, 12:09 PM Thread Starter
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Re: Getting around the limitations of JavaSound on OS X

Quote:
eTwin wrote: View Post
Does this mean that I have to measure at about (50 + 60 =) 110dB to be able to see meaningful RT60 figures
No, make your measurements at a comfortable listening level. RT60 values are based on the slopes of filtered and processed versions of the impulse response, high signal levels are not required.
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post #50 of 171 Old 02-06-14, 05:31 AM
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Re: Getting around the limitations of JavaSound on OS X

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No, make your measurements at a comfortable listening level. RT60 values are based on the slopes of filtered and processed versions of the impulse response, high signal levels are not required.
Ok, I did and attached it, name is "Amp_At_-10dB.mdat".

The sweep was through both front speakers.
To my ears it was quite loud but I understand the message "Low signal level" should be ignored in this setup.

Does the mdat file seem like a valid measurement?
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