Monitoring For Mastering

[oldbobd]

Loudness Levels For Listening

Sound pressure is measured in decibels on a "SPL" scale where 0dBSPL is the threshold of hearing and 140 dBSPL is so loud that the sound becomes pain. Conversation levels are at about 65 dBSPL, and people generally listen to music between 70 dBSPL and 90 dBSPL, with a rock concert running 115 dBSPL sound pressure levels.

Most music is listened to between 70 dBSPL and 90 dBSPL. If we use 70 dB SPL as a guide and get things sounding "right" (regarding loudness), the product will also sound good at 90 dB SPL. If we adjust things to sound "right" for 90 dBSPL playback, it may not sound as "right" when played back at 70 dB SPL.

There is a "Compression Factor" in hearing where the ear starts to compress the sound that's heard - and this compression factor starts really affecting things at 90 dBSPL and higher playback levels (according to my ears). Everything may sound good to you at 90 dBSPL but some instruments can start getting lost when the music is played 20 dB softer.

Monitor Calibration Signal

Many tests are done on monitors with "pink noise" that has equal energy per octave.  This of course is much more accurate than using a single-frequency test tone. One recommended method is to set the pink noise out at 83 dB SPL as measured by a sound level meter with C weighting (which is the flatest response of the meter). It's not a bad standard.

But when we listen to well-balanced music, we don't hear "equal energy per octave" coming out of the speakers - we hear music.  Izotope published "guides" with their Ozone spectrum analyzer that define two opinions of a "pleasing balance" of high-to-low-to midrange energy in music.  Both of these guides show a drop-off of high frequency energy beginning at about 2 kHZ. The "6 dB Guide" has the energy dropping off at the rate of 6 dB for every octave above 2 kHz, a guide that has been around for decades. The second guide drops off at the rate of 3 dB per octave, is called the "pink guide" and is susposed to represent the energy of high end on many modern releases.

So if I wanted to calibrate my monitors, I would use pink noise that was filtered at about 4.5 dB per octave roll-off on the high end (an averaging of the two Izotope guides)  and then set them to a cetain SPL level with a sound level meter.
 
Sound Level Meter Readings

You want to set the monitors to be at 70 dBSPL with the sound level meter.  Unfortunately you would want to have something called "B Weighting" on your meter which adjusts the meter to be sensitive to the frequencies the way the ear is at 70 dBSPL.

Unfortunately meters that have "B Weighting" cost upwards of $500.  The good news is that you can "average" the C and the A weighting settings and come very close.

A New Approach?

I don't think that the two different methods (83 dBSPL with pink noise & C weighting) and the methiod I described are going to result in that much difference in monitor calibration. 

Most people, however, don't calibrate their monitors but sometimes use a sound level meter so see how loud the monitor speakers are.  Just like I stated in the "calibration", you want to run your speaker levels so music reads out 70 dB SPL B weighting - Sometimes, in rock in paticular, this is awfully close to the 83 dB C weighted reading, but often it isn't for the music I usually encounter

Bob

From the text, Loud And Clear - Motown Heritage Mastering, by Bob Dennis - now slated for Labor Day 2009 Release

[Dino Ziogas]

Great tip OldBob!

I must add that the SPL calibration level depends also on the room and if you're into near- or mid-field monitoring. For nearfield monitoring in smaller rooms 83dBSPL is usually too high. Something like 77 or 79dB is more tolerable.

[Silent Bob]

I'll second that.  Sometimes I mix in this huge room with these JBL monitors from Europe.  83dB in my own 14x16 control room is almost uncomfortably loud but at this room, 85dB seems almost not loud enough.

Interesting post!

[oldbobd]

I'll second that.  Sometimes I mix in this huge room with these JBL monitors from Europe.  83dB in my own 14x16 control room is almost uncomfortably loud but at this room, 85dB seems almost not loud enough.

Interesting post!

I don't understand - when is 85 dB not loud enough?

[Silent Bob]

Well, what I mean is in that big room, 85dB doesn't seem to be nearly as loud as 83dB in my room.

[oldbobd]

Great tip OldBob!

I must add that the SPL calibration level depends also on the room and if you're into near- or mid-field monitoring. For nearfield monitoring in smaller rooms 83dBSPL is usually too high. Something like 77 or 79dB is more tolerable.

I basically don't use mid-field monitoring - most of my monitoring is near field (24" away from speakers to 72" away).  I understand the importance of monitoring in larger rooms for film sound, but I'm not that convinced that for most music releases, they will be listened to in cars or at computers.  If it sounds good near-field, it should sound good in a larger listening room. 

Larger listening areas where being away from the speakers more take a lot of space and a lot of treatment to construct - this means $.  I'd rather spend my $ on other toys than a great listening enviornment.

I don't find 83 dBSPL that loud.  It would seem to me thast 83 dBSPL is 83 dB SPL.  I primarily read out what the SPL level for music playing is, rather than calibrate with pink noise.  83 dBSPL C weighting is about 70 dB SPL A weithed within 3-4 dB.  In my tests 70 dBSPL with B weighting is about equal to 79 dBSPL C weighted


bob

[angela14]

Thank you for sharing with us your post about monitoring for mastering. It is a great information. I find it useful.





_________________
Home security systems 

[pyrael]

You know I just had a hearing test last week. the doctor told me that 85dB is the point where damage starts to occur. Any idea on how they are measuring that? Personally I would like to know how to dial in my monitors for safe listening being that I already have suffered a hearing loss in the 2k to 8k range which explains quite a bit about why my EQing is sometimes skewed.

[Silent Bob]

Different people have different ideas about where hearing damage starts.  OSHA says 93dB SPL A weighted for 3+ hours or something like that but I KNOW I get fatigued pretty quickly at those levels so I don't agree with them.  I think more like 90dB SPL C weighted is more reasonable.  Then again, it changes for the individual so perhaps 85dB SPL is "playing it safe".  I can listen to 83dB SPL C all day if I wanted and be a little fatigued, so a lot of those estimates are also based on time.  For instance, 130dB will cause INSTANT hearing damage while 100dB may take a few minutes.  Frequency response makes a big difference too.  Perhaps they should take individual measurements for hearing loss over 32 bands or something and record them separately.

[Johnny]

This thread played out too quickly to suit me. There's much to be said concerning this subject (but don't worry,
I'm not going to say much): I have a friend, well intentioned but inexperienced, he prefers to talk instead of
record. Nonetheless, he had his panties in a wad about buying such and such monitors because he had some
idea in his head that they HAD to be "flat". This went on for some time. I finally invited him into Good Intentions,
my humble little corner of the world and sat him in the sweet spot. I put on a test CD and began running tones
for him. "Tell me where my monitors peak," I said. He sat silently until around 7kHz. "There," he said. (heh, heh.)
I continued until his ears ran out at about 16k. "Hear that?"  ..."No."     "Well, dude, your ears just petered out,
so why pay an extra thousand bucks for sounds you can't hear?" My reasoning was that 1) his ears weren't flat
and 2) his ROOM wasn't flat. If his monitors went down to 8Hz, his room wouldn't.

I don't do boom and tinkle and my ears dip around 8k. I don't work any lower than 42Hz (bass low E) and rarely
above 12.5k. Why then, methinks, waste all of that energy reproducing freqs I can't even hear anyhow? My
recordings have plenty of "air" and bottom end. Besides,I can't hear the fundamental at 42. I cut off at 30Hz
and at 16k. I feel it gives the audible frequencies more room in the final mix. Do you fellows think that I'm
out of my mind or not? Bear in mind that I record at 7.5 ips and I don't have a lot of headroom to play around
with so I try to make the most of what I have. Most "critics" that I run my CDs by can't believe that I'm going
direct from tape. 

[Silent Bob]

No, you're basically right.  I think it's important to have as flat of a monitor system as possible, but not if the bill infringes on the acoustic environment.  My monitor system is not that great, no doubt about it.  But it lets me hear problems as low as 20Hz and as high as 18KHz.  I could have spent twice as much money on my monitors for maybe 1dB flatter frequency response, but I sunk that money into some DIY acoustic treatment which made about a 12dB difference.

The concept that a room can limit bandwidth is a misnomer.  There can be many spikes & dips in the response throughout the room, but the bandwidth within that room is theoretically limited only to anything greater than DC.  The air itself can absorb sound, but you're talking .5dB per meter at 20KHz and I doubt your subject sits more than 2 meters away from the monitors.

[Dino Ziogas]

Just to add. As far as frequency response of most decent modern monitors is concerned, they'll mostly "flat" - ok their voicing might vary from make to make but frequency response flatness to the last .1dB isn't that big a deal. The human ear learns how to adjust [that's why reference CDs are a good practice].

However it's the time domain [impulse] response that\s important. If the consecutive kick hits can't be accurately reproduced because the monitor is sluggish ,it gets smeared and all your mixing decisions go out of the window because our brains can't compensate for time domain problems as well as freq ones...

[Silent Bob]

If the consecutive kick hits can't be accurately reproduced because the monitor is sluggish ,it gets smeared and all your mixing decisions go out of the window because our brains can't compensate for time domain problems as well as freq ones...

Which is why it irritates me to no end why all these monitors have 4th order crossover networks in them.  MAJOR smearing outside the stop band range.  There's absolutely no reason to use any more than a 2nd order filter, yet there they are.  However, this reminds me that our mind's ear is super sensitive to dynamic distortion, far more than frequency response or harmonic distortion.  Case in point, it may seem like 50 watts is plenty to drive a near-field monitor.  In reality, 80 watts per channel (RMS at 3% THD) is BARELY cutting it.  You may never hear any harmonic distortion, but a lack of headroom in the amplifier will cause a loss in transient response, making you feel like the music is soft.  This may make you crank up the level higher than you should but it'll also make you EQ and compress the signal differently.  Of course, not all amplifiers are alike.  Class G or H amplifiers take it one step further with switching power supplies.  If for instance a transient passes, the power supply gets drained so a transient following the first will be at a much lower level.  Again, this makes for a very compressed sound.  In the case of a continuously hot signal (loudness war any one?), the actual output level can sag & clip even well below the rated limit of the amplifier.  This has lead to a lot of manufacturers using class D amplifiers which run at max peak amplitude all the time, but since it's pulse width modulated, the only contributing factor is sheer frequency response of the system.  That almost eliminates dynamic distortion and yields a much more "tube-like" sound which has aso been found to have very little dynamic distortion compared to typical op amp design.

[oldbobd]

Just to add. As far as frequency response of most decent modern monitors is concerned, they'll mostly "flat" - ok their voicing might vary from make to make but frequency response flatness to the last .1dB isn't that big a deal. The human ear learns how to adjust [that's why reference CDs are a good practice].

However it's the time domain [impulse] response that\s important. If the consecutive kick hits can't be accurately reproduced because the monitor is sluggish ,it gets smeared and all your mixing decisions go out of the window because our brains can't compensate for time domain problems as well as freq ones...

One thing that I have noticed is that any type of powered (biamplified, triamplified) speaker seems much better on transient response than any speaker that has internal passive crossover networks.  It's gotten to the point that I just don't want to listen to speakers that aren't powered.


bob

[ghprod]

Hi bob, thanks for tips ..

some one tell me, u can go with lower SPL to get precission on low freq, and more SPL to get high freq

regards

thanks