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Computer Recording: Improving Sound Quality


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#1 OFFLINE   Tekker

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Posted 27 July 2007 - 03:33 AM

This lesson will cover some topics about gear that will help improve the quality of your recordings.

Contents:
The System as a Whole
Microphones
Mixer vs. Mic Preamp
Recording Soundcards
Soundcard/Preamp Combination
Stereo Speakers vs. Studio Monitors
Headphones
Headphones vs. Speakers
Room Acoustics



The System as a Whole

Before getting down to business, it’s important to keep your whole system in mind as you upgrade individual components. The quality will only be as good as the weakest link in the chain. Using a $5,000 guitar on a $15 pocket-sized guitar amp doesn’t make much sense. Likewise is true for recording equipment. Your instruments, room acoustics, microphones, mic preamps, soundcards, effects, monitoring system used for mixing, etc. will ALL play an important role on your final sound. If you upgrade one component and don’t notice much improvement, it could be that the new component isn’t much better than the old one ("more money" doesn't always mean "better"), but it could also be that something else in the system was the weakest link in the chain and is now keeping the full potential of the new component from being heard.


Microphones

Microphones contribute greatly to the quality of your recordings. They can be used for miking acoustic guitars, guitar amps, as well as recording vocals and other acoustic instruments. Using good quality mics on electric guitar and acoustic guitar will usually give much better results than pluggin in direct.

If you are currently using an inexpensive PC mic, then upgrading to a better quality mic (that uses an XLR connector) will significantly improve your sound quality. To use an XLR mic you will need either a mixer or a mic preamp. While you could get cables that would plug an XLR mic into a computer, XLR mics don't tend to work well with standard PC sound cards. Because of the impedance mismatch (low impedance for the XLR mic and high impedance for the sound card) you will get a much lower volume. Preamps, mixers, and computer interfaces with built in mic preamps are covered in more detail in the following sections.

For more a more detailed look at microphones, mic placement, and also some mic recommendations, see the tutorial on microphones HERE.


Mixer vs. Mic Preamp

The output from a microphone is very low and in order for this signal to be processed, it is necessary to use a device called a mic preamp to boost the volume of the mic up to a level that other electronics can use it. These preamps come in a variety of ways, such as in mixers, computer interfaces, and even standalone units.

Mixers are handy as they handle a lot of channels at once, most also have built in EQ and sometimes a variety of other effects. However, cheap mixers (such as Behringer) do not generally give the best sound quality... I have a Behringer mixer that never gets used for recording.

For recording purposes, dedicated mic preamps are a great way to go and there are some very good preamps that won’t break the bank. Even if you don’t use a mic for recording, you can make use of preamps that have 1/4” direct inputs with High-Z (high impedance) settings so you can plug your guitar directly into the preamp and then into your computer without any external processors. This is what I do and then use effects plugins on the dry guitar sound. For more info on this go HERE for a tutorial and demonstration on using VST plugins with your guitar.

Art Tube MP ($40)
Studio Projects VTB-1 ($120)
M-Audio DMP3 ($160) - Dual channel preamp.


Recording Soundcards

Recording soundcards are much preferred over standard PC soundcards as these are not meant for audio recording. They are great for gaming, but when it comes to audio quality even the Sound Blaster Live cards with the 1/4” inputs that “pose” as recording cards won’t hold up to soundcards that are designed for recording (such as M-Audio). Recording soundcards can also come with several inputs to record multiple tracks at the same time. Having multiple inputs is great if you are in a band or have friends that you like to jam with and want to record all at the same time.

M-Audio makes a wide range of soundcards, below are a few examples:

Audiophile 2496 ($100) – 2 inputs and 2 outputs
Delta44 ($150) - 4 inputs and 4 outputs

* NOTE: These audio soundcards do NOT have build in mic preamps. So if you want to be able to record with microphone(s), you will need an additional mic preamp(s) or a mixer to plug the mic into.


Soundcard/Preamp Combination

Another option is to get a soundcard with preamps built in. A good and inexpensive option is the Tascam US1641 ($300). The US1641 provides a total of 14 analog inputs (8 microphone inputs with phantom power and 6 line inputs), 2 monitor outputs, and 4 line outputs. From what I have found I believe you can use all 14 inputs simultaneously.

While this may seem overkill if all you only want to record yourself, it is actually a very good deal as the preamps are included. If you wanted to use 2 mics at once with one of the other M-Audio cards, you’ll have spend at least $80 (for the Art preamps) just to get two mic preamps, plus the price of whichever card you get. So you’ll end up spending around a couple hundred anyways for only 2 channels. So getting 14 inputs for $300 is an unreal deal! :)



Stereo Speakers vs. Studio Monitors

One of the biggest improvement to my studio has been upgrading my old stereo speakers that I used for years to real studio monitors.

For mixing you want to try to get speakers that are as flat as possible in order to hear what your mix really sounds like. Mixing on flat speakers will allow your mixes to translate to other speakers better.

In general stereo speakers are designed to make stuff sound good by boosting certain frequency ranges. While this may be a good thing while listening to music as it is perceived to sound better, for mixing this is a bad thing because you are basing your mixing decisions on something that is not in your recording but in your speakers. This will cause you to overcompensate for your speakers’ sound in your mix. The result is what you mix may sound great on your speakers, but will not translate to other speakers very well.

Generally studio monitors are the better choice for mixing as they are flatter. Of course these are just simple generalizations as not all studio monitors are flat and not all stereo speakers are hyped. Some audiophile stereo speakers can beat out some of the best studio monitors, so it all depends on the particular brand and model of speaker.

I highly recommend the Yorkville YSM-1p ($450). I did a LOT of research before getting these and on every forum I looked at these were considered to be the best in their price range.

B&W have incredible reviews (even by professional mixing and mastering engineers on some of the recording forums I frequent). They have quite a range of products that range from affordable to very expensive. These are audiophile stereo speakers and from what I have heard form very credible sources these are some of the best speakers you can get for mixing as well.

In reality, there is no such thing as a “perfectly flat" speaker... It just doesn’t happen. ;) So another important point is to get used to your speakers. Listen to as much music on them as you can and compare your mixes to professional mixes. Also listen to your mixes on as many other stereo systems as you can (in your home stereo, friend’s stereo, your car, your computer speakers, headphones, etc.) to get an idea of how your monitors translate to other systems.


Headphones

There are a lot of headphones in the same price range, so it’s hard to find a “best for the price” comparison. However, I think it would be hard to go wrong with any of the major companies like Beyerdynamic, Senheiser, AKG, Sony, etc.

Some things to consider when choosing headphones:
- Durability and build quality.

- Light weight and comfortable to wear.

- Not ear fatiguing. This is especially important for headphones since they blast sound directly into your ears. Harsh sounding headphones can wear your ears out rather quickly.

- Open/closed: Open headphones are not insulated, so sound can easily leave (and enter) the earpieces. If you are recording using microphones the sound from the headphones can leak out and get picked up by the microphone. For tracking purposes, it is best to use closed headphones that are insulted so that the mic only picks up what you are recording. However, during the mixing process, open headphones generally are the best. Sound does not resonant within the earpiece because it is not confined within the earpiece, so the sound quality is (in general) better for open headphones... This of course depends on the overall quality of the headphones, but all else being equal go for open headphones for mixing and closed headphones for tracking.

If one pair of headphones has to serve both tracking and mixing purposes, then get closed headphones instead of open headphones. The best use of headphones during mixing is for checking your mixes (NOT actually mixing - as will be explained below), therefore it is better to not compromise headphone isolation during recording because you don’t want the sound from your headphones being recorded again by the mic. Closed headphones are also good if you mix in a noisy environment (due to kids, loud neighbors, etc ;)). If you don’t record using mics and you have a quiet place to mix in, then isolation doesn’t matter and open headphones will probably be your best option.


Headphones vs. Speakers

Headphones are big in the home recording world and for good reason. They are relatively inexpensive (especially when compared to speakers/amps) and allow you to mix without disturbing family members. However, unless need to meet certain noise requirements, it is better to mix with speakers over headphones. Headphones are very good at covering up mistakes in your mixes and even headphones labeled as “mixing headphones" will have more problems than using speakers.

The sounds from the headphones go straight into your ears and don’t combine with each other before reaching your ears. This is very important when dealing with stereo instruments and effects (like reverb), because each speaker will be playing something that is slightly (or very) different than the other. This creates phase differences (for a basic explanation of phase see HERE). When the two signals are not identical in both speakers (mono) the signals from the two speakers will interact with each other and different frequencies will either add together or subtract from each other (depending on if they are in phase or out of phase) and thus change the overall sound that reaches your ears. This is NOT the case with headphones. The signals from the two ear pieces never interact and therefore they don’t add or subtract from each other, so you could have big phase problems in your mix and never know it until you listen on speakers.

To hear this first hand, here is a very simple test you can try:

Insert a song into your recording program (a single stereo file, not a multi-track project). Invert the polarity on only ONE channel - either the left or the right, but not both.
NOTE: If your recording program does not have this option, then let me know and I’ll try to dig up a VST plugin that will do this.

Now play this track on your headphones. You should notice how the sound seems to originate from inside your head instead of from the speakers. This is a very strange effect but try to ignore this for now and pay particular attention to how the bass sounds. Does it sound like it has weakened or does it sound about the same? While the origination may have moved to inside your head it should sound essentially the same and shouldn’t have lost any of its tone or fullness.

Now play this same track on your speakers. Notice any difference in the bass? If you answered yes, then you are correct. The bass should now sound much weaker and thinner. All of the thump and fullness of the bass is gone and all that is left is weak and wimpy. This is due to the speakers being 180 degrees out of phase (like the second diagram in the link on phase above) and the result waves created by the speakers combine together before reaching your ears and the bass is drastically decreased in the mix. In headphones however, you do not hear this effect at all because the waves never interfere with each other, they get pumped directly into your ears. While this may be ok for casual music listening, it's bad in mixing because you want to be able to accurately hear what's "wrong" with your mix so you can fix or at least try to minimize the problems.


Another reason for using speakers is the placement of the speakers. For studio monitors, home theater systems, etc. the ideal angle for your speakers is 60 degrees. You and your two monitors should form a 60 degree equilateral triangle. The angle of headphones however is 180 degrees which is far from ideal, so your head and the two speakers form a straight line. With headphones, you don’t have as much of a feeling of depth as you do with speakers. In other words, instruments/vocals that sound far away (pushed back into the speakers) or close and up front (popping out of the speakers). This is because there is nothing in front of you as both speakers are on the side of your head, so you can’t judge distance in front of you. Effects like reverb and delay are used to create this sense of depth and a lot of it is lost or at the very least sounds very different with headphones.

Having said this, headphones definitely have their place in the mixing process. They are great for panning instruments because you can essentially blow up your stereo field to 180 degrees and put each instrument exactly where you want them. This is analogous to Photoshop in that you can zoom in on an image for editing details that may be harder to see when zoomed out. But like the Photoshop analogy, looking at a zoomed in picture doesn’t look very realistic. Likewise headphones don’t create a realistic soundstage (I’ve never heard any live bands whose sound originates from within my head... aside from my own air guitar solos but that’s another story :smilinguitar:). Once you have the instruments panned the way you want them, go back to the speakers to make sure it still sounds the way you want it.

Headphones are also very useful for checking your mixes on as well. Most of your listeners will probably listen to your mixes on headphones at some point, so it is essential to make sure it sounds good on them. Chances are though if the mix sounds good on speakers it will also sound good on headphones as well. However, the reverse is not always true, a mix that sounds good in headphones can sound terrible on speakers. So in general mixes translate much better from speakers to headphones than from headphones to speakers.


Room Acoustics:

Room acoustics is far to often overlooked. Typically lots of money is thrown at "stuff" such as mics, preamps, interfaces, effects and not a dime spent on what is quite possibly THE weakest link in the chain... the room treatment. Your room plays a very big part in your sound so it is important not to neglect this area of your studio. This goes for the mixing environments as well as the recording environment because if the room is distorting what you hear, then the decisions you make during mixing are also going to be distorted from trying to overcompensate for the room.

I'm not going to do a formal lesson on this as these websites provide FAR more information and details on this topic than I ever could:

Beginner friendly and contains lots of real-world practical applications:
Eathan Winer - Acoustics Articles

Much more advanced and technical, contains lots of specs and numbers:
John Sayers - The Recording Manual


'Cause I don't wanna read the book, I'll watch the movie.

Tekker's Lessons on GfB&B: Music Theory, Recording, and General Guitar





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