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  Compression Q&A  

 
I have experimented with Cakewalk but I don't think I fully understand compressor and EQ settings. Can you help? -Shannon


Compression and limiting are simple to understand with just a bit of explaination. Compression is like an automatic volume knob that turns down the signal depending on how you've set the parameters. Commonly the idea is that louder portions of a given signal can be reduced so that the overall level is more even.  This is helpful to (1) lower loud surges and (2) allow the softer parts to become more even (and more audible) with the louder parts -- giving better consistency to the sound.

The first setting is the threshold - which is the point at which the device works. Like the threshold of a doorway is the point at which you step into the other room - it's a "line" you cross over.  Imagine recording a vocal that's going through a compressor - the softer parts of the vocal performace - before the threshold - are not altered by the compressor.  But *after* the threshold (after you step "across" the line), the device begins turning the volume down.

How much it's turned down is determined by the compression ratio. 4:1 compression ratio means that for every four dB of signal that goes into the unit, it turns it down so that only 1 dB comes out. 8:1 means that for every 8 dB that's put in, an increase of 1 dB is what goes out. Often we see a meter reading called "Gain Reduction" which is how much the device is turning the signal down (that's what I prefer to look at on the meters).

The attack time is when (how soon or how fast) the gain reduction unit starts altering the sound. The release time is when (or how long until) the unit stops altering the sound. The slower the attack time, the more the initial signal gets through the unit without being altered. Slower attack times let through more peak (and the immediately trailing) material because it waits longer to start working.

Limiting (which is really just more compression) starts up at 10:1 and goes up from there. Since limiting is really turning down the signal a lot at once, it's faster and mainly used on peaks which are occasional, not constant. Used properly, limiting should be hardly detectable because it's controlling shorter amounts of sound.

Since 2:1 - 6:1 is a more subtle amount of alteration to the sound, it can be used for more containment, for instance on vocals, bass, etc. Stereo mixes, however, don't sound good being overly-contained. In mastering, I'm very careful about keeping the openness to the sound of a mix, so I recommend being carefull about how much you may be compressing the stereo output of your console. If your meters are swinging too far "into the red" check on individual voices and instruments that need the containment. A good mix doesn't have a ton of giant level surprises!

Limiting can serve to keep you out of the red, but often I prefer it used on individual tracks. If you put too much compression or limiting on your mix, un-doing it is more difficult. Limiting and compression is frequently used differently on different songs, so try different settings to see how they work for you (but don't assume you should just turn the knobs up to "10"!). 

Tip: It's a good idea to try stereo buss limiting to make reference CDs for evaluation of what really happens to your sound on commercial systems -- particularly to reference your music with commercial CDs.  Loud-and-limited commercial CDs have been carefully crafted, but there's much to learn by doing it yourself and listening critically. ... just lessen or remove that limiter when you're making your final mix... or stick with Separations and allow the dynamics to speak out musically.) 

Note: If you end up liking a lot of limiting or compressing on your stereo mix, it may be a good idea to leave the limiter or compression on when you make Separations!  It's easy to rely on the way the sound is dialed in when you are pushing the signal up against the limitor or rcompressor.

Caution: You want to notice if it becomes very easy to make it sound too good when using a stereo buss compressor.  Well, the sound can never be too good!  What I mean is that when everything in a mix comes forward a bit, you hear more of everything that you've recorded.  This can be good except when you start to reduce the parts of the sound that need to snap forward.  Same thing with a Finalizer in mixdown. Since it sounds so good, it tends to make you not work as hard at the tracks level to get the mix to be totally exciting and punchy as you want it. Working hard on the mix (within reason) adds a level of excitement to the song. It adds a "performance" element, if you will, to the mix process. When you put more energy into the mix, it somehow comes out more on the cd.

I had great fun mixing through a Finalizer several times, thinking how good it sounded, until I got these mixes in to the mastering room. Right before my ears, what I thought was exciting and vibrant was more soggy in the mastering room.  The Finalizer had enhanced the sound while causing me to overlook some of the detail I normally would. The highs and lows were good, but it wasn't up to the song's potential. Once again, I was reminded thata well advertised gadget often does not take the place of solid basic music-based engineering.

Even riding faders is a very correct form of gain control (like manual compression), and with your ears as the guide, it's a very musical form too. If you are unsure as to whether or not to compress your stereo buss prior to mastering, then make 2 mixes, one with and one without. These two mix versions can be referenceed to the other songs during the mastering process to see what works best.

"Separation mastering totally enhances the sound field. It's a new journey in the way of mastering."
- Ice Green, producer for Gina Green, Ritestep Records

"We had no idea what to expect, but it seemed like the logical thing to do.  You were right.  We had more options, the sound opened up and we're happy with the results." - Rise

"The technology of Separations gives more vitality to the sound - it gives a new experience to my sound."
- Israel Lomeli, Hispanic Rock

"The clarity brought to our album using Separation Mastering was truly eye opening."
- Dan Kaulahao, Deal By Dusk

Q) What type of EQ & comp. for vocals, guitars, bass and drums?

There just isn't a formula, because every musical element is unique and deserves the listening treatment. Eq'ing is a another article in itself. For now, as far as compression, I like 4:1 for vocals and bass, maybe 5:1 for guitars, and generally I don't compress drums unless I'm going for an effect, or it's just needed in the mix. (I do like gating toms slightly.) If the drummer isn't consistent with the volume of his/her playing, I attempt to iron that out at the tracking session, not the mixdown. Sampling and replacing drum notes is an option, but ultimately, it's more of a win for everybody if the player (the source) is held to a higher standard.

As far as getting a professional sound, there is just a learning curve, and every engineer goes through it. I can remember hearing records thinking, "The high end sounds so darn much better than what I'm doing!" Then I'd work and work on the high end, and think, "That record has much better bottom than mine does!" Then I'd work and work on the low end, and then I'd think, "Why can't I get the mids to sound like that record?" And the list goes on. Striving for warmth, clarity, smoothness, width, apparent loudness, mono compatibility, etc... it's just a process. Experience is the only teacher that is one-on-one with you at every moment of your career, and the frustration that goes with it is a valuable component of this process, because it motivates you to *ask* the questions and seek the answers.

Guideline: Generally, one answer comes up again and again. "Less is more." Tweak as much as you can at the source, then progressively less as you go up the next layer up the chain, and so forth. Therefore, doing nothing at the stereo mix buss is right in line with this idea. And...remember Rule #1 - there are no rules. Be as unique as you want to be - don't rivet yourself into any one idea if another one will work better. Sometimes mistakes even lead to cooler ideas. We all experience the mistakes and frustration, so don't be hard on yourself at these times. Just acknowledge your feelings, let them go, and enjoy the ride along the way.

Q) I'm compressing my digital stereo mix with an ART PRO VLA tube compressor before we go into the PC for mastering. The results have actually been pretty amazing. Glancing at your article, this might not be the best way to go. How can I suggest [what you advise] to my engineer when he's the one with the experience and I'm not? If it sounds good to me, should I stick with it, or will it really cause that much trouble later for the duplication house? -Jeremy

There are two things to address: the technical situation, and the communication situation. As far as the technical part, there are no rules! If it sounds good, then that's a step in the right direction. An engineer I know puts a tube compressor on his mixes just because it adds a sound he likes, even if the compressor isn't working more than a half dB. But.... in some cases Studio Monitor Madness could be occurring - the monitors could be masking some loss in dynamics. When in doubt, just compress the appropriate tracks within the mix (like bass, vocals, etc.) and let the mastering engineer do the stereo work.

The duplication house (CD replication plant) will only have problems if you give them a CD with uncorrectable errors or a defective master - they're not concerned with sounds as much as a cassette duplication company (but a good cassette company will be able to handle whatever you give them... it's just easier for them if it's well mastered).

In the tricky area of communicating a preference with your engineer, you have to keep balance in the chemistry that you've developed with your technical personnel. I use the "donut" theory - say something positive, then introduce the challenging part, then say something positive again. Also one of the best ways to diffuse the energy is to come right out front and say, "I've gotten some ideas from an outside source that may be different from what we've done together for a while. I'm a little uncomfortable about bringing these things up, because I appreciate your work, and I'm not into stepping on anybody's toes, especially yours. I don't even know if these new ideas are good ones or not, but I'd like to know if you'd be open to trying some things. They may be cool, they may not be cool. I'd like your opinion, and for the sake of stretching what's possible, I'd like to experiment with some changes. What do you say?"

The "how can I suggest otherwise" could also go like this: "Fred (a.k.a. your engineer), I'm loving the results we're getting so far. And as a curious sound person, I've read an article by a mastering engineer that discourages compression, although he doesn't state this as a hard and fast rule. Given my budget, do we have any room to experiment with leaving the stereo compression off the next tune to begin with, and then doing a separate version with it in?"

Hopefully Fred's response would be to accommodate your request. The thing to be careful of is that once the compressor is in, there could be some level increase that seems to be enhancement. *Buyer Beware!* The key is to listen to both the compressed mix and the uncompressed mix *at the same level*. You may have to lower the compressed version to really go side-by side, but when the volume level (use your ears, not just meters) matches, then see if the difference is really better. Often, I don't compress, I only limit the peaks to get the CD hot.

Important: While the particular song you're working on now may sound good compressed, in the context of the *whole cd*, it may not need as much compression, or it actually may need more. When I master a project, I like to hear the context of the whole project... the entire personality of the cd. One song influences the others... even the order can have an affect on how much processing different songs will eventually have. But if you've compressed it while you're in the studio... wrapped up in the moment... and you find that it's tooooo much later on - guess what? Tough luck (or go back and remix).

Another great advantage to professional mastering is that you can take home the mastered CD with you and listen to it... compare it to other CDS and on several systems. Then, if changes need to be made (like less compression or more compression), then you can go back and in a relatively short time, make the change you prefer... and have a better product that you're happier with for years to come.

Q) I am interested in a compressor for mastering my music but I do not know if it is worth it to spend more money on an elaborate compressor like the Cranesong or the Summit just to get only 10-15% better sound quality than if I buying a cheaper compressor with similar or with slightly less specifications than from the "High End" compressors.

Specifications don't always tell the tale. I tried a [highly rated] compressor that many mastering engineers thought was great at that time. I didn't care for [that] compressor, so I took it back and tried six others. The one I picked wasn't the most expensive. In time, that [highly rated] compressor wasn't used at other mastering studios either, and the one I picked gained in popularity. Specifications are a good staring place, particularly when it comes to being on a budget.

The music I compose is cinema/documentary, classical/ballet and is from synthetic sounds.

Clean and quiet and musical will be the best, and the high end units will sound better. More open and smooth. However there may only be a 10% difference. It depends on your customer and how much of a difference it will make to them and to the buying public. If it's just too much for what they will or won't hear, then I'd say save your money and look to some better speakers (unless you're very very happy with them already). I think great speakers, power amps and cables can make as much or more difference.

I have some R & B songs that I want to mix down the music without vocal, so I can sing them live. My uncompressed mixes sound low level and transient using Digital Performer.

Hard disc recordings for the most part have a more "vacant" less solid sound than analog. Look at the waveform and you'll see much spikier looking peaks than the fat, more rounded analog version. If you cut your drum tracks on analog and transfer to hard disc you'll get more wallop on the bottom end.

What would be some good compression settings that I could apply to the stereo mix here to go right out and sing live with it. When I've tried to do this on my own, it takes some of the punch out of the music. -Jeffery


Punch comes from the excursion (distance of movement) of the speaker. Too much compression usually results from the threshold being set too low (acting too soon) and just causing a blend. What you really want is more fatness in the peaks, and more apparent contrast in the dynamic range (higher peaks, lower lows) but still keeping the track full-bodied. A limiter might be the ticket, enabling you to bring the overall mix up without curving down too much musical information. A 10:1 ratio or more with a fast attack and release time would be a good staring place, but you'll just need to experiment to match your exact musical program.

NOTE: In the May 2003 Mix Magazine issue (a must-have issue), there's an article called "Stop Mousing Around" where they have about 6 paragraphs stating "MONITOR SECTIONS: THE MISSING LINK." A high resolution monitor controller can be a powerful tool to hear the distinctions necessary when listening to compression.

Q) Do you have any suggestion for getting a more transparent sound? -Quincy

Separations can add a significant amount of transparency. Besides that, good electronics and clean mics help for sure. I'm also a fan of high end power cords that clean up the AC lines - this translates to better top end and tighter bottom. Clean mixing helps too - don't have bad caps in the console, some transformers can add too much coloration, etc. Don't bounce too many tracks digitally unless you really need the processing power - there can be some dullness and lack of zip that occurs from track bouncing.

Keep lots of headroom - don't press everything to the top. Don't have your recording room be too dead - some diffusion and live surfaces are good. Higher quality reverbs add a great deal of transparency that the cheap ones just can't match.

Sometimes cutting with eq at 400Hz 500Hz 600Hz or 700Hz (anywhere in between) can help give a more pure sound. If stuff is a little boxy or cloudy a peak eq (dip in this case) cutting with a moderate Q can help.

The arrangement of the instruments can help - be sure stuff isn't crowding out other sounds, be sure parts are played tightly, and pan things so they don't overlap too much. If your sound seems good in the studio and fluffy in the car, your monitors could be too bright or you could be adding too much from 32Hz and down in the bass or kic.

When you solo stuff, it should sound almost too clear to be correct, but when it's all blended it, then it should sound correct. Avoid using the same frequencies on too much stuff. Spread the timbre out evenly, keep the bass clean and even, watch for ground loops or hum in your system. Keep testing out different ideas - we all discover much that way!

Q)  I have a set of Mackie monitors and I have an Beringer equalizer to real time [analyze] the room to check for hot spots. Is that ok or should I learn the monitors natural curve and room issues?  Is it good to compare CD’s and listen in the car and other play back units and make the adjustments by memory?

I'd leave out the Behringer and get to training your ears to detect a range of sounds - and then understand how that range translates to the commercial playback world.  If you can't get the distinctions you want, alter the speaker placement and the room conditions to meet the preferences of your ears.  What that means is play 20 different CDs.  Pick up some of the ones I listen to and check for the characteristics I talk about on that page.  You should hear 20 different sounding CDs and you should be able to pick out what you like and what you don't like. 

For instance, I bought the Eric Clapton CD "Back Home" and I like the clarity and the mix, but the sub-bottom end is TOO much, and it's too slamming loud.  Disappointing because he doesn't need it to be hot to sell records.  I love the Toad the Wet Sprocket "Coil" even though the mixing is a bit compressed - all the music is clear and warm.  You should put up your reference CDs, and if you keep hearing the same "tone" that you don't like, then modify the speaker and room so you find a situation where you like the differences and characteristics.  Listen in several consumer places and take note of what you hear that you like.  What's obvious, what's subtle. 

The closer the speakers are to the wall, the more the bottom end changes.  The farther back you sit from the speakers, the more the tone changes.  The farther apart the speakers are, the more the tone changes.  See how it sounds when you sit or stand at the very back wall. 

Use really really good cables because that will change the tone of the top end a lot.  Be sure your CD playback system is excellent - a bad CD player with so-so converters won't give you the truth.  Sorry to spend more money, but if you are referencing to pro music, you have to hear it as good as you can possibly afford.  Again, the cables make a huge difference.  I use several kinds of Audioquest and Mapleshade products.  You may think Mapleshade's "Tweaks and Wires" are funky looking but they know their stuff.

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Brazil's BR6
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Marc Seal
Marc Seal
Gregorian Chillout
Gregorian Chillout
Eden
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Everette Harp
Cutting a Hot CD

Mastering Procedures

How to prepare for mastering

Creative changes

Even More Secrets of Mixing

Even more about studio monitors

Separations

How to create Separations

Illustrated History of Separations

Great reference CD's

Getting a bigger sound recording

Eq Settings that make a mix come alive!

How much compression?

Should I have the pressing plant make the glass master at 1X?

Stereo widening techniques

Differernt opinions in the studio

Backup your masters!

How to Align a 2-Track Analog Machine

Career Consultation

Created in 1998 • Modified 07/12/03
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