The virtue of calibrating your audio system

It’s amazing what you can learn about the short-comings of your studio setup when you take the extra step of calibrating your monitors and console. After a long several months of integrating an analog console (Soundtracs PC-MIDI 16) into my DAW setup, including installation of patch bays, cabling, and new audio interface (Lynx Aurora 16), and some nice used Genelec 8040a monitors, I finally got around to running some fairly simple and standard calibration tests.

So what is calibration for anyway?
When you are mixing an audio project you make decisions based on the frequencies and loudness of various tracks. Due to psychoacoustic factors (how the brain perceives audio) we are often led to make decisions based on loudness (louder often sounds better) that don’t always contribute to the overall quality of a mix. Many audio engineers agree that listening to mix at high loudness levels is not only bad for your ears, but may not result in a balanced, pleasing mix.

Bob Katz, the renowned mastering engineer (www.digido.com) has advocated the K-System of metering, and this involves among other things having a well-calibrated audio system where the maximum loudness of your monitoring system is set to a known value. Here is what I did last night to get my loudness levels set correctly.

  1. Downloaded the -20 DB pink noise wave file from his site (www.digido.com).
  2. Turned the volume control on my Central Station monitor controller all the way to the right (to zero db), and turned down the trim controls for my main monitors so I would not damage my speakers and ears.
  3. Turned off the right speaker, so I would be calibrating one at a time.
  4. Loaded the pink noise file into Wavelab (any DAW would do), and set it to loop continuously.
  5. Pulled out my trusty Radio Shack digital SPL meter, set it to C-weighting and slow response (per Mr. Katz’s recommendations), and sitting in the listening position, pointed the SPL meter at the left speaker.
  6. Adjusted the trim on the monitor left channel louder and louder until SPL read +83 dB. This becomes the calibrated listening level for maximum loudness, when my monitor controller is set to zero dB.
  7. Turned off the left monitor, turned on the right one, and repeated steps 5 and 6.

The Results, Please!

OK, this was pretty loud, although pink noise is a random noise, and 83 dB is quite tolerable. But I neglected to do one thing. I forgot to disconnect my subwoofer! OK, I have a KRK sub patched in line with the main monitors, and realized that the considerable amount of bass noise I was hearing came of course from the sub, which sits on the floor underneath my workstation.

So I disconnected the sub and hooked the output from the Central Station Monitor A directly into the Genelecs (there is no way to otherwise bypass the sub, unfortunately). Then I reran the calibration again and found that my SPL’s were down considerably, to about 72 dB max. The subwoofer was adding a fair amount of low frequency audio to the mix. This may or may not be a good thing, depending on what you are mixing, but I decided that it would be better to start clean, without the sub.

So I recalibrated and reset the trim levels on the CS so that now I am back to 83 dB for each monitor. Life is good. Loaded a mix I had been working on, and began to immediately notice some ickiness in some of the synth bass lines, violin etc. I had been using plug-in EQ to play with this sound, and now it sounded pretty bad. So I disabled the plug-ins, and basically decided to remix the project from scratch. I noticed that the Genelecs now yielded a more “accurate” mix. I did not need to monitor at 83 dB, I actually preferred setting it the level about 10 dB lower, but when I want to hear it louder, I can now be reassured that my level won’t exceed 83 dB. This will hopefully add more consistency to my mixes, as well as protect my ears…

Next up – calibrating the console.

Analog and Digital Hybrid Studios

I recently gave a talk to the San Manuel Rotary breakfast club where I was allowed to expound on the pros and cons of digital versus analog recording to a group of hungry business persons. Thanks for putting up with me, Rotarian folks, you are great people!

So here is the gist. In the beginning of recording there were wax cylinders, then wire (magnetic recording on actual lengths of metal wire), then finally after World War II, tape. We can thank Studer, the German company that invented tape recording for Hitler, for the format that dominated recording up until the 1980’s. Studer tape machines are still in use in studios around the world, and are considered a kind of gold standard for tape decks.

OK, that brings us to 1982, when the compact disc format was unleashed upon the world. Up until then, analog recording from the tape machines went directly to vinyl. Many of us cherish our collections of old LP’s for their warmth and smooth sound. With the CD came digital recording. Digital is a format where analog sound is converted to numbers, sampled at rates of 44,100 times per second (abbreviated as 44.1 KHz) and higher. At first CD’s were hailed as a revolutionary advance, but soon after the audiophile community began to notice that CD recordings often sounded more sterile or brittle compared to vinyl.

Now the early CD players had rather primitive converters compared to today. A digital-to-analog converter is a chip built into the CD player which translates the numbers back into audio waveforms. Similarly an analog-to-digital converter was used in the original mastering of the CD to get the analog sound from the tape into the computer for burning a CD. Today the converters are not an issue, except in low-end CD and DVD players.

The “Red Book” CD format specifies a much lower resolution (16-bit) and sample rate limited to 44.1 KHz, compared to how music is actually recorded digitally. Most engineers record at 24 bits or higher (more bits means more headroom, that is, greater dynamic range between the softest and loudest sounds). Sample rates of 96 KHz or higher are not uncommon, although there is a raging debate about how important these are. To make a CD we have to reduce the bit depth and modify the sample rate to match the CD format (this involves the technical processes of dither, and sample rate conversion, respectively).

The biggest problem with digital audio today is not that it is inferior, but that it is too good! It really does record what is out there with astounding clarity. However that clarity includes all the warts of a poorly treated recording room, irritating resonances of some instruments (such as the violin!), etc.

So what does this have to do with a digital-analog hybrid studio?

Sometimes we would rather view life through rose-colored glasses. With audio we often prefer the more “rounded” warm sound of analog tape/console circuitry (which actually adds some pleasing harmonic distortion), to the often clinical sound of digital. That being said, there are ways of making digital sound better, and I have explored many of these. Aside from software plug-ins, which attempt to simulate analog warmth, there are other approaches which take advantage of real analog hardware.

One trend in recent years has been to go all-digital, recording directly from a microphone or instrument into a pre-amplifier, and then into the computer via a “digital audio interface”, basically an A-D convertor hooked up to the computer via Firewire, USB, PCI card, etc. This is assuming that the musician/engineer is recording any kind of live instrument or voice to begin with. Much of today’s electronic dance music is made entirely “In the box” using plug-ins and software synthesizers running in a piece of software often called a DAW (Digital Audio Workstation), such as Protools, SONAR, Ableton Live, Cubase, Logic, etc. (I prefer to use the term DAW to refer to both the software and the computer hardware).

But – A counter-revolution is underway, fueled by a conspiracy of old school guys and young engineers who record bands or themselves playing real, actual hand-on musical instruments. This approach acknowledges the advantages of digital audio for editing, applying signal processing (compression, EQ, pitch correction, etc.) while at the same time trying to get as much of that old-school analog sound as possible.

There are many ways to approach this:

  1. Record into the DAW, then send your final stereo mix out to analog processors for sweetening, then convert it back into digital for the final mix. Devices are available called summing boxes that allow you to take the converted audio, run it through a tube pre-amp, compressor, eq device, etc. before routing it back into the computer.
  2. Record using a console, then into the computer. Consoles were mandatory in the older days, but now most small, project or bedroom studios cannot afford them, or even have enough space for one. Basically a console (or “desk” as it is often called) is a series of channels with faders and knobs, preamps, EQ, routing capabilities, etc. with as few as 8 and as many as 100’s of channels, each capable of recording an instrument or vocal simultaneously. Some consoles are entirely analog, some are digital, and some both. Old school analog consoles can often be found used for a “song” (I paid $500 for mine, it cost somewhere around $8000 in the 1980’s). Use the high quality analog circuitry of the console as front-end to your DAW to get some of that sound we strive for.
  3. Even more radical, get a used tape machine, record through the console to tape, and then dump the tape tracks into the DAW for final editing and processing.
  4. Any combination of the above, where you involve real analog hardware. For example some engineers advocate taking digitally recorded mixes, sending each track or group of tracks out the D-A converters into separate channels of the console, then letting the console produce the final stereo mix (“analog summing”), then sending that back into the computer. This is similar to #1 but involves the sound introduced by the analog circuitry of the console, where the console electrically “sums” or combines the separate tracks into a stereo mix.
  5. You can also take stereo or even individual tracks that were recorded entirely in digital, and send them out the tape machine and then back into the computer. This uses the tape machine as a kind of effect processor. Tape is known for its relative warmth, a byproduct of way that tape stores electrical information. That is topic for another blog entry, however.

Any or all of these approaches can be found in the modern-old school digital-analog hybrid studio. I am sure having fun implementing mine. Everything old is new again…..

So what’s this new age studio business anyway?

Without trying to sound too pompous or airy-fairy about it, we have entered a new age in many different ways, but not the least in how music is produced and consumed. Since the advent of and widespread use of microcomputer technology, the first decade of the 21st century has seen a phenomenal growth in amateur and professional music-making. It seems like everyone who is a musician of any stripe has a “studio”, or knows someone who does. I am no exception here.

I got started recording in 2002 with a (not too inexpensive) M-Audio Delta 66 audio interface and a small Behringer (no comments please!) mixer, and SONAR 2.0, a full featured DAW (Digital Audio Workstation) software product. This was soon followed by a few cheap Chinese-made mics, and a keyboard for generating synthesized sounds (Alesis QA 6.2, still a favorite), and additional software for “mastering” my own mixes.

Let me add that my only recording experience prior to that was in several Tucson studios as a performer on local band CD projects, in the 1990’s. That, and a compilation tape made for an art project at Stanford in 1968, using an old Ampex reel-to-reel with sound-on-sound capabilities (how i wish I had kept it!). And I remember a tiny, old reel voice recorder that my folks got me when I was a child, and wondering why my voice sounded so strange (we all feel that way the first time).

So recording my own musical ideas was like stepping off a chasm, not knowing where I would end up. The result was my first solo CD, Barn Jazz, Vol. I, released in August 2003. I sold several hundred copies and that was it. I was hooked.

So back to that bedroom studio, if you are trying to record your own music or your band, what do you look for in a studio, and how can you tell if you are wasting your time with your friend’s rig? That is one subject I will return too often, but leave you with the following critical success factors, not necessarily in order:

  1. The Engineer (technique)
  2. The Producer (musicality)
  3. The Room (acoustics)
  4. The Gear (quality)
  5. The Players (groove)
  6. The Tune (listenability)