Calibration clarification

paullambert100

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Hello,

I have read the manual and have a question about the calibration process. I wondering if during the calibration process you need to keep your speakers plugged into the outputs? On my Apollo arrow I only have two outputs so I will loose one speaker since I am supposed to disconnect one of them to free up a line out to create the calibration loop? Please advise! Thanks for your time
 

John Mulcahy

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No, the calibration is for the electrical path so the speaker is not needed or used.
 

paullambert100

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Thanks john! And the cable needed to make the loop would be a regular instrument cable?
 

John Mulcahy

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Sure, that's fine. With high performance interfaces like the Apollo offerings the main purpose of the loopback calibration is to make sure there isn't any monitoring active, there's nothing that really needs correcting in the interface response.
 

paullambert100

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Thanks for your help!
 

paullambert100

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Hi John,

I'm sorry to bug you again but I have tried to calibrate the file but am not getting the input level hot enough even with the input level maxed on console (uad). In REW preferences, I have selected the "output device" and "input device" as Universal Audio Thunderbolt. I have selected "1" as the input and "1" as loopback input. I then have an instrument cable attached to the Mic/Line 1/L running into the output 1/L. In console, I then turn the monitor on channel 1 to "off" and then run the calibration. The output is giving me a solid 12db but even after increasing the input 1 input gain I can only get the input 1 gain to show about half that volume in the vu meter in REW. Do you or anybody else have an idea what I might be doing wrong? Thanks!!!
 

DanDan

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Soundcards and Interfaces are generally electrically excellent, so no need for Calibration. Be careful with Driver software like Console. You do not want to route/monitor your measurement mic on your speaker!
 

paullambert100

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Hi all and thanks for your reply dandan! I ended up figured out the issue before I caught your response. I didn't have the output set to L duh! I do have another quick question. I have a cal file for my Sonarworks reference mic that I'm using with REW. I'm assuming that I am supposed to upload the cal file in the "cal files" section of REW. However would I create a new cal file upload for the mic or would I replace the cal file that now says "Universal Audio" (which was part of the sound card cal file I generated)? I have attached a picture reference in case that is more clear. Thanks again for any help.
 

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DanDan

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For simplicity and certainty I advise you to remove the soundcard Cal File and completely abandon that venture. The Sonarworks comes with two Mic Cal Files afaik. One is for use with SW only. The other is for use with third party software, in this case REW.
Downloading the microphone calibration files
If you need to download the actual calibration files for any reason (using an offline computer, using the XREF 20 mic with third-party software, storing them for backup purposes, etc.), they are also available to download on our downloads page here. Simply enter your Microphone ID as shown in the image below - this will download a .zip package consisting of two files:

  1. Microphone calibration file for 30° off-axis measurements in .swmic format (Sonarworks software native format) to be used with Sonarworks Reference 4 Measure app.
  2. Microphone calibration file for 0° on-axis measurements in .txt format for third-party use.
 

DanDan

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"Can you justify why sound card calibration is a useless undertaking?"

No, because that is not a view that I hold or state. I do however consider it unnecessary, most particularly for newbies. The extra layer of complexity is often coupled with third party driver software for the Interface. The newby will enter a whole world of pain Donnie.... I think the fact that USB Mics work is evidence enough that a second channel is unnecessary.
 

paullambert100

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cough.. I did spend 2 hours trying to figure out how to calibrate properly lol... Can you please help me with one more question. I watched the AV NIRVANA video "beginners Guide to room eq" and the presenter mentioned to measure at 80-85 decibels. I also sent my first measurement to GIK who said my noise to floor ratio was a little low especially in the low end. Can you please explain how I make sure I get the floor ratio high enough or hit that 80-85 decibels? I'm assuming my output volume was too low so would I need a SPL reader and placed at my listening position and then adjust my output volume until it's around the target 80db mark? Or is there a way to do this without the SPL meter? Thanks for your help! Very much appreciated.
 

DanDan

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You are welcome. I used to assume that a good loud sweep was necessary to achieve a good Signal to Noise Ratio. Given a ambient say 40dB background noise from fans etc. one might think a 90-100dB Sweep is necessary to see a full RT60. No. The sweep is not wideband at any instant so is not competing with wideband noise. 75dB is sufficient. I still go for 80 ish out of habit. There are great iOS Sound Level Meter Apps. Soundmeter X by Faberacoustical. studiosixdigital.com https://www.cdc.gov/niosh/topics/noise/app.html
 

paullambert100

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Thanks again!
 

paullambert100

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Hi,

I have retaken the measurements and used the niosh app at listening position to confirm that the output is 75-80db during "Check levels". The strange thing I'm finding is that after REW gives me the green "LEVEL OK" and when I start the measurement the head room is in red at 5db for the left speaker and in green at 12db for the right speaker. I'm curious if I'm doing something wrong or can there really be that much discrepancy in the room? I'm using Neumann KH 120 speakers and made just the eq is flat on both speakers and the settings are the same. I am also not quite sure to make of the "noise floor" graph in the distortion section. I have attached the mdat file and screen shot in case anyone is interested in taking a look. As always thank you for your time.
 

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paullambert100

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Thanks! Would you also have any insight into why when I "test levels" and get an "Ok Level" check but end up going into 5db (red) when doing the actual measurement (this seems to only happen to the right speaker)? It seems to be trigged by the low end of the sweep. Thanks again!
 

DanDan

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Paul, plse don't take this the wrong way. The REW Manual is a really excellent piece of work. An education in itself. The app has become very rich in features, dense, with consequent difficulty in driving it. I do wish for a 'Lite' version to send to my clients so that I can 'be there' acoustically. Within the App there are some great basic Acoustic, even Electroacoustic, Tools. A very well specified Signal Generator, with probably the smoothest manual sweep around, using frequency follows cursor. A very well capable SPL Meter....... RTA, etc. Place your iSLM central. Play Pink Noise on one speaker, then the other. That will tell you if they, and the monitor controller, etc. are all working at equal volume. I am not sure what you are describing, but you can sweep a sine wav down and listen for distortion on the Red Light speakers. You are equipped. I often mantra Test Trumps Theory. But it also Trumps us guessing stuff that you can prove on the spot.
 

John Mulcahy

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The right speaker has a big modal peak at around 49 Hz which will reduce the headroom as the sweep passes through that frequency.
 

paullambert100

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Thank you dandan and john. I agree and have read the manual but will go back and reread. It is a well written one. And john may I ask one more question? In regards to this modal peak? Is this a room issue (as in the right side of the room is resonating this way and causing this peak) or a software / issue? I am using the exact same preamp input/output settings and mic placement. All I am doing is changing the output from L to R in rew. Thanks so much
 

John Mulcahy

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Modal resonances are a property of the room. The speaker location determines how it excites a modal resonance, from maximally to not at all. The mic location will similarly affect how much the mode contributes to the response.
 

paullambert100

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Thank you very much!
 
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