Controlling Standing Waves In The Small Home Studio

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Controlling Standing Waves In The Small Home Studio      

Tim Smith                   

Our article today deals with what engineers call standing waves in the home studio.

Standing Waves

Probably one of the single largest hurdles to home studio recordist is getting  good monitoring in their spaces. Much time, effort and science goes into designing an ideal acoustic situation in a professional studio.

The main culprit is  standing waves. A simplistic explanation is that they are sound waves which instead of being absorbed by their surroundings,tend to bounce around in the space. Worse yet,some of these waves can be accentuated while other sound waves are attenuated. This all results in a mix that is off balance. You won’t hear a true mix in this situation and your mixes will suffer as a result.

Think for a minute of a sound wave like the waves that come from throwing a rock into a pond. Sound causes an invisible wave in the airspace in much the same way.Now imagine that you and a bunch of friends start to throw numerous rocks into the pond. The results are waves which intersect one another, just as the speakers in your studio are making different sounds and the sounds also intersect. As long as these waves are in harmony with one another all is well,but all to often this is not the case and some of these waves might be cancelling one another out or exaggerating certain waves over others. In a worst case scenario the sound will be very muddy and unclear in the bass ranges and possibly have other issues with the higher frequencies all depending on your space.

 

Tuning Your Room

Not all rooms are built to the same dimensions and so not all rooms will have the same monitoring characteristics.In order to be accurate, sound must be dealt with in both the time and frequency domain.The frequency of the sound determines the characteristics it will have in the room as well as the time it takes to travel. Sound waves have frequency overtones and undertones or harmonics of the fundamental frequency. These harmonics can make life miserable for the home recordist.

There are several ways to deal with this problem, the most common being to tune the room with sound absorption material and equalization.All sound waves have energy that must be trapped in order to  avoid  nasty harmonics and to keep the waves from bouncing off of your walls. Covering your entire wall with sound absorption might make it too dead a space to listen in though.

One way to tune a recording space is to use a source of accurate sound transmitted from the monitors and then monitored by a microphone located in the listener position in the studio. The idea is to adjust an accurate EQ until the result is  flat. Then what you hear in that room is considered to be uncolored and a fair representation of the mix you hear.Sometimes pink noise is used which is a composite of many frequencies or it can be done with one frequency at a time.There are also numerous proprietary systems you can buy which will do a fairly good job of tuning your room for accurate sound mixing.

I use a system made by IK Multimedia called ARC2. While not always a magic bullet, it more often than not will align a room to a much better listening situation. Using both time and frequency calculations ,it can rid a studio of many common acoustic problems. See the picture here of my ARC graph both before correction and after:

ARC2

 

The orange line represents my before curve and the white line represents after the correction. The main consideration when using ARC is that it be set up correctly following all instructions which can be slightly tedious as you need to position a mic in multiple locations and take sound measurements with the software.It’s well worth the effort though,and  has helped me in my mix decisions. As you can see ARC has pretty much balanced my room.

What’s going on with my bass?

More often than not many of the more serious problems in small recording studios concern the bass of the mix. The reason for this is because the dimensions in many rooms are very similar in stick constructed homes within the last 50 years. Rooms that are 12×12,15×15 or similar combinations are very prevalent . Box and rectangle shaped rooms are common in those sizes and it’s these dimensions that closely align with the wave length of bass frequencies which, if you could see a bass sound wave it would be close to the length of your walls from floor to ceiling and even from side to side depending on the wave and the room size specifically. It’s  safe to say that most rooms like this will exhibit muddy sound in the bass ranges. The most common symptom of this is that the bass you will hear in an untreated room will seem to be louder than it actually is because of standing waves.Not only that ,but the bass will be undefined. The very first thing you will notice after treating your room will be less bass and that’s because there really is less bass.

But what about my mid and high frequencies?

These frequencies are certainly problematic at times as well,especially if there are no sound absorbers placed at either side and at the back of your monitors. Any frequency has the potential to become skewed after entering your room environment. Since bass has more energy and a longer wave length than mid and high frequencies it tends to be more difficult to manage,especially at higher db levels. Yet the stereo image can be skewed by wandering waves in the higher frequencies. Wandering waves also cause phase cancellations which essentially cause you not to hear certain frequencies and make bad mix decisions.

Here is a chart indicating the length of sound waves at certain frequencies:

Wavelength01

Make educated guesses on selecting sound treatments

Not all sound treatment is created equal. The panels sold by many manufacturers that are usually 2×2 square and fairly thin. The type that you hang or glue to your wall. These are only good for the higher frequencies. They won’t help at all for bass control. The smaller panels are good for mounting on a wall next to your monitors so they manage the sound coming from your studio monitors.The 2×4 panels are also used in this way and on the ceiling above the monitoring area, usually hung on wires  6 to 12 inches down. These minimize waves that might be hitting the ceiling. Carpeted floor helps in this regard as well. And remember, not all foam is the same.  For this kind of a job you need dense foam made specifically for acoustics.

Bass on the other hand tends to concentrate in corners, so a good installation would involve dedicated bass absorbers floor to ceiling in the corners. These are also usually made of a dense foam material. There is plenty of info for the do- it- your- selfer out there for the adventurous and handy.You can make your own sound absorption.

I am moving soon, I rent, my space is dual purpose. I can’t install sound absorbers. Are there any other options?

I saved the best for last. In many cases you can still manage to get a decent mix if you do a few things properly without spending a fortune on sound absorbers and seriously modifying a room. It ‘s  a short cut though and short cuts are usually not the best option but it may be your only option at this point.

Here are a few tips that will greatly help you to get better mixes right now:

Mix mostly at lower volume levels. This will keep the standing waves to a minimum.

Mix with your monitors at close range. Mixing close will give you mostly uncolored sound as it isn’t going as far before it reaches your ears.

Learn your monitors. If you know , for instance , that your monitors are hyped at 200hz , then mix accordingly. Make adjustments for your speakers if necessary.

Learn your room. If you know that bass is a problem in your mixing room, then you would want to mix more bass than you think you really hear because your room is hyping the bass. Also consider mixing the highs and mids first and then adding bass drum and bass guitar. That way you can get a more accurate view of those ranges without the bass clouding your judgement.

Use a good pair of mixing headphones. Using headphones along with open studio monitoring can give you a better picture of what the mix really sounds like.

Listen on multiple systems. Listening on multiple systems will allow you to hear your mix across different types of systems.

All of these tips involve a little more work than simply getting your room tuned as close as you can. Like I mentioned earlier ARC is a really great way to solve many of these problems without putting up even one piece of foam. I highly recommend acoustic treatment and ARC if at all possible.

 

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