Trying to Understand Monitor Calibration

[98bpm]

Hello out there. I'm trying to understand how to properly calibrate my pairs of monitors in my home project recording studio. The pieces aren't coming together for me and I'm very green when it comes to audio recording as my experience is mainly in MIDI production.

I've looked at SOS articles, web articles, and YouTube videos about how to do this, but it seems like I'm missing something and I hope someone can help me.

I have a pair of Alesis M1 Active monitors as my primary speakers and a pair of Tannoy Reveal 502 powered monitors for my secondary pair. I'm using Cubase 8 Pro and want to be able to switch between them as I study how to record and mix.

The articles I've read, suggest using pink noise to calibrate the monitors and I found a noise generator that I use on my iPad for that purpose. I also found a SPL meter to use on my iPhone to check decibels.

Here's my setup:
iPad pink noise to -----> Mixing Console
Mixing Console Main Output to ----> MOTU 828x audio interface Analog Input 1&2
MOTU 828x audio interface to ----> iMac running MOTU CueMix FX & Cubase Pro 8
MOTU 828x audio interface Main Outs to ----> Alesis M1 Active monitor pair
MOTU 828x audio interface analog out 7&8 to ----> Tannoy Reveal 502 monitor pair

Here's what I get:
I start the pink noise generator on the iPad with it's output level at 0dB and raise the master L/R fader on the mixing console to 0dB and boost the trim on the channel for the iPad so I get a console level meter reading of 0dB.

I look at the Analog 1&2 input level within the CueMix FX software for my audio interface and have the fader set at 0dB as well. The CueMix FX software Input Trim is set at 0 for Analog In 1&2. However, the pink noise is peaking at about -8dB. Cubase is about the same level. I've read that 0dB in analog is supposed to be the same as -24dBFS in digital, so I don't know why the input is so high. I could cut the Input Trim within the CueMix FX software by 16 and that will give me the -24dBFS, but with the input trim being so low, I think I'd have to boost the gain levels on my console to get a decent recording level - but I get more hiss from the mixer channel. I don't understand.

Within CuMix FX, I turn up the Main Volume (Monitor Level) feeding the Alesis M1 monitors to Max. I start the SPL meter and set it for C-weighted and Slow response. I power on the one monitor and turn the level dial until the SPL meter reads 80dB (the recommended level according to most sources) and repeat for the other monitors.

Results:
When monitoring content through the audio interface on either monitor pair, I get an SPL reading between 83dB and 90dB (depending on source content). However, when I monitor from Cubase 8 and lower the main bus fader in CueMix FX, the output level I get from Cubase peaks at only 71dB on the SPL meter.

Another confusing piece of information is that some suggested that the pink noise generator be set to output at -20dB, but again, this lowered the level on my console so low, that I had to boost the channel's trim level all the way up to get a 0dB meter reading, so what was the point of that?

Please help me! What's the proper way to do this?

[Hugh Robjohns]

It's late and I'm not going through your post in detail tonight... I think a substantial part of your difficulties is confusion over decibel readings in analogie and digital systems... But everything you need to know is here:

http://www.soundonsound.com/sos/may14/a ... toring.htm

I'll give a more detailed response tomorrow...

H

[98bpm]

Thank you for the link. I'll give it a read and look forward to your thoughts when you have more time. Need all the help I can get!

[Hugh Robjohns]

I start the pink noise generator on the iPad with it's output level at 0dB and raise the master L/R fader on the mixing console to 0dB and boost the trim on the channel for the iPad so I get a console level meter reading of 0dB.

There's lots of 0dBs here, but they all refer to different things. Is the output from the iPad analogue? If so, does the 0dB output level refer to 0dBu, 0dBV or something else?

More importantly, what does a console level reading of 0dB mean? Again, 0dBu, 0dBV, 0VU (which might be 0dBU or +4dBu depending on the mixer)?

There is lots of scope for confusion here -- dB by itself is just a ratio, not an absolute level. To make it absolute, we need a reference point which is normally denoted by the suffix letter.

And then again, noise is a spikey signal whose peak level bears no obvious relationship to its RMS level -- the latter being the only relevant aspect for speaker alignment.

I look at the Analog 1&2 input level within the CueMix FX software for my audio interface and have the fader set at 0dB as well. The CueMix FX software Input Trim is set at 0 for Analog In 1&2. However, the pink noise is peaking at about -8dB.

Okay, so you've sent the analogue output from the console into your computer interface. Digital levels are referenced to the clipping level, so I think you're talking about a received level of -8dBFS.

This level isn't much help for calibration, I'm afraid because, as I said, you're using a (spikey) noise signal but measuring it on a sample-peak meter. To make any meaningful decisions about signal levels you need to use an RMS meter.

It is for this reason that in the Monitor Wizard article I mentioned previously, I recommend using a noise signal file from the BlueSky website which has a known RMS value.

I've read that 0dB in analog is supposed to be the same as -24dBFS in digital, so I don't know why the input is so high.

The SMPTE alignment recommendations are for the analogue reference level to align with -20dBFS )with TONE, not noise). The standard analogue reference level in the US is 0VU, and 0VU is usually aligned at +4dBu. Consequently if you do the sums, 0dBu would align to -24dBFS... but the proper reference alignment is +4dBu = -20dBFS -- the point being that there should be 20dB of headroom above the nominal reference level.

The reason your noise signal appears to be so high is because you are using a sample-peak reading meter, rather than an RMS one. You should check your basic system level alignment first using pure sine-wave tone signals because they read correctly on all types of meter.

Again, there are suitable reference level tones on the BlueSky site.

I start the SPL meter and set it for C-weighted and Slow response. I power on the one monitor and turn the level dial until the SPL meter reads 80dB (the recommended level according to most sources) and repeat for the other monitors.

The SPL meter is an RMS-reading meter designed for use with a pink noise test signal, and the C-weighting and slow average is correct. The target SPL is dependent on the size of your room (I've listed typical values in the Monitor Wizard article), as well as the headroom margin you are working with in your DAW.

Please help me! What's the proper way to do this?

To align your monitors, download the BlueSky pink noise and tone files, and follow the instructions in the Monitor Wizard article.

To align your mixing console to your interface, use a tone source through the console and adjust the computer interface's input sensitivity so that tone at the reference level from on your console (0dB on its meters) produces the required reference level in your DAW (-20dBFS).

Hope that helps.

H

[98bpm]

Firstly, let me say thank you so very much for taking the time to address my questions. I know I said a lot in my post, so your response is very much appreciated. I do feel like I'm off to a much better start. I went to the Monitor a Wizard article you mentioned as well as the two other articles mentioned at the beginning of your article. As a subscriber, I don't know how I missed this.

I downloaded to sound files mentioned in the article and have a question about the best way to get the tones to the mixer. Would I use the analog out on the CD player / recorder and connect it to the mixer on an available channel pair or use the 2 Track In on the mixer? I want to assure that the -20dBFS RMS sound files on the CD don't get boosted or cut going from the CD player to the console.

Also, I was wondering if the volume level on the audio interface's output dial going to the interface Main Out (connected to my Alesis M1 monitors) should be turned all the way up. Is that ideal or would it be a problem?

Thanks again!

[Hugh Robjohns]

I downloaded to sound files mentioned in the article and have a question about the best way to get the tones to the mixer.

Your first post said that the monitors were driven directly from the interface. That being the case, the mixer is completely irrelevant as far as the monitor line-up is concerned. Just follow the directions inthe Monitor Wizard article.

If you subsequently want to align the mixer's meters with your interface/DAW digital operating level, you just need to send tone (not noise) through the mixer from any convenient source (CD player, iPad etc). With the tone turned up to read the reference level on the mixer meter (0VU, 0dBu or whatever it is...) adjust the interface input level control to get the appropriate reading on your DAW meters (eg -20dBFS). Job Done!

Also, I was wondering if the volume level on the audio interface's output dial going to the interface Main Out (connected to my Alesis M1 monitors) should be turned all the way up. Is that ideal or would it be a problem?

It really depends on the gain structure of your monitoring chain. I normally keep the interface level turned up fully, and then use a monitor controller between interface and speakers. Set the monitor control to the reference level (typically with the volume knob around 2 o'clock) and adjust the speaker input sensitivity controls to achieve the desired acoustic reference level.

H

[98bpm]

Thanks Hugh. I had been thinking about getting a monitor control/switcher, but I changed my mind when I learned about the Control Room features in Cubase 8 that allows that kind of control. Your article makes a good case for getting one anyway. I've got my head wrapped around this pretty good now, so I'm on my way.

Cheers!

[Exalted Wombat]

I think you'd be foolish not to have a physical volume control/mute switch on your desk. Not all listening needs to be at a carefully calibrated level. You can go expensive, or you can get a Nanopatch.

[The Elf]

^^^+1!!!

I use Cubase Control Room extensively, but I definitely wouldn't want to be without a physical, in-line volume control for my monitors.

I've been hit by a couple of the 0dBFS speaker/ear-shredding shrieks of a computer crashing in the past and I never want to be far from a volume control in case it happens again any time in the future!

[98bpm]

If I may, I'd like to ask one last question on this subject. I followed the instructions in the Monitor Wizard article, but had to skip step 3 (I don't own a physical monitor control - Yet, that is). At this point, all I have is the Control Room Level dial within Cubase. So should this be set to the reference level of -20dB before I proceed to step 4? By default, the dial is set at 0dB when you open the control room. I ask because I went through the steps with the Control Room Level dial set at the default 0dB and the end result was very comfortable, but not much more volume to pump beyond that point, and I can tolerate volume higher than that. Sorry for sounding like a rookie, but I am when it comes to recording.

[alexis]

Re: the physical volume knob, as the OP has Cubase, might consider a Steinberg UR28M interface if the I/Os work out well. Integrates very well with Cubase when recording audio, and has a big knob easy to reach, which even if you don't use it much is very nice to know is there at the ready (and can be very handy when relief/protection is needed in a hurry)!

[98bpm]

Thanks for the recommendation, alexis. I hadn't seen the UR28M before. Spotted the Behringer Monitor2USB which is more in my price point, especially since I already have an audio interface. The Behringer isn't out yet, though.

[ef37a]

Thanks for the recommendation, alexis. I hadn't seen the UR28M before. Spotted the Behringer Monitor2USB which is more in my price point, especially since I already have an audio interface. The Behringer isn't out yet, though.

I am no "Behringerphobe" I have had a few of their products* and generally been happy with them (even the BCA2000 was very good but just not reliable.Third failed unit still in loft)but monitoring is just about THE most important thing you do and I would wait until SoS have pronounce that Berry controller TOTALLY transparent before including it in your monitor chain! In truth, I can't see that happening. I am "ideologically" opposed to passive controllers but at that sort of price point I see no alternative.

I calibrated my Tannoy 5As by the simple process of generating pink noise at -18dBFS in Audacity and controlling the level in a small mixer that takes a feed from my 2496 sound cards. I set the LEDs on the mixer for -20 (vu?) and adjusted the front level controls on the Tannoys for 83dBC on a cheapo, 15quid, Maplin meter. This is too loud for day to day work so I simply marked the pot positions then backed them off to around 70dB. Son, (when here!) can simply crank things back to the reference for checking a mix. Suits us!

*I began to warm to Behringer about the time of the X32 but lost faith when Uli "bottle it" and am now even more enraged because they are back to their old ways with a shameless copy of the Blackstar HT-5 amplifier.

Dave.

[Hugh Robjohns]

So should this be set to the reference level of -20dB before I proceed to step 4? By default, the dial is set at 0dB when you open the control room.

This confusion stems from another misunderstanding of decibels. The DAW's operating reference level (to give optimal headroom when tracking and mixing) is -20dBFS -- an absolute level, hence the suffix to identify the fixed reference.

The volume control in the monitor control panel is a relative level control -- hence no suffix -- with its normal operating position at 0dB or unity gain.

The idea is that with the volume knob showing 0dB, you should get the desired reference acoustic level from your studio speakers. You can then adjust the volume up or down from that reference level as necessary, but can always get back to the calibrated reference precisely.

Regarding the comments about 'tolerating more level' -- first, you generally get better balanced mixes when auditioning at lower levels (although the mixing process is harder!), and secondly, bear in mind that tracking and mixing in the DAW with a reference of -20dBFS means that you have a very generous headroom margin to accommodate transients. When you 'master' your tracks and remove that (now unnecessary) margin -- or if you audition commercially mastered tracks -- the level will be around 20dB louder anyway! The fact that the Cubase control room monitor panel shows attenuation on the volume knob is handy in this context because the amount you need to turn the level down to get back to something approaching your reference acoustic level is an indication of how compressed the track is.

@Dave -- setting your monitors to an acoustic reference level of 83dBC in a typical UK domestic room is madness -- as I explain in that monitor wizard article. I'm not surprised you had to recalibrate to a much lower level for day-to-day use.

H

[The Red Bladder]

This whole thread (which I have only glanced at - I ain't reading all that!) reminds me of the old German technicians' saying "Wer viel misst, misst Mist!"

(He who measures a great deal, measures sh1t!)

If I want to set up speakers for a very critical mastering session, I get some previously recorded and first class music that I like in the same genre and alter things like subs and highs, mids and lows until it sounds good to me. (Cue Nicki Minaj's 'Purpleprint' tracks and crank it up!)

Someone somewhere is over-thinking something!

[Hugh Robjohns]

There's an old English saying too, "He who wades in without knowing what the discussion is about often talks sh1t!"



Experience is a wonderful thing, but not everyone has enough of it to be confident at setting up a monitoring system unaided.

H

[The Red Bladder]

Well, I really would expect someone to provide me with an executive summery of this thread!

[ef37a]

There's an old English saying too, "He who wades in without knowing what the discussion is about often talks sh1t!"



Experience is a wonderful thing, but not everyone has enough of it to be confident at setting up a monitoring system unaided.

H

......And,..
http://www.atmos.washington.edu/~robwood/teaching/451/Lord_Kelvin_quote.pdf

Dave.

[98bpm]

Any chance of SOS giving a review of the Behringer Monitor2USB in the near future? It looks like a knock off of the SPL 2Control shown in the Monitor Wizard article, but less than half the cost. Just wondering if it's worth waiting for.

[Hugh Robjohns]

I believe we are waiting for one to arrive for a review in the not-too-distant future...

H