Have you ever had the experience of a great sounding rehearsal at home only to be faced with a completely different outcome at the gig? This is a scenario that leaves many musicians scratching their head, trying to figure out why their tone is so different in a new environment. It all comes down to room acoustics and the reflective qualities of a room.
In a simple sense, every room we perform in possesses a certain frequency response. This response, variable to our position inside the room, causes boosts and cuts at different frequencies. This issue can be controlled to a large degree with acoustic treatment, and sound enthusiasts usually undertake this task in professional recording environments. In your local pub, however, there is likely to be little to no consideration of room acoustics.
We are all familiar with acoustic problems, and we have all experienced them to some degree even if we are consciously unaware of this fact. An interesting test, and one that I always like to use, is to try and talk over the PA system. If another person can audibly hear what you’re saying then the sound engineer is likely to be doing a good job in controlling room acoustics.
There are 3 types of acoustic issues that we can experience:
1. Standing waves
This is a phenomenon that happens when sound is reflected off a fixed boundary (such as a wall) and then interferes with itself. In other words, the sound waves are being superimposed causing their energies to be either added together or canceled out.
2. Low frequency build-up
This is a common issue in many venues. Low frequencies are generally ‘felt’ rather than ‘heard’. Have you been inside a loud club and felt the ground shake beneath you as if there was an earthquake? Low frequencies can become cluttered and muddy which mask other frequencies in the mix.
3. Flutter echoes
This is a series of rapidly repeated reflections that are caused by sound waves bouncing around between various parallel reflective surfaces. The best way to describe this is the “boing” sound which is similar in characteristics to a squash ball.
In the average room, we are faced with a multitude of parallel surfaces which make up the acoustic properties of the room. Another threat would be right-angled surfaces present between wall-to-wall intersections. These reflect sound back in the same direction it’s sent from causing prominent frequencies to build up.
By understanding this logic, we have 2 general options to combat bad acoustics when deciding where to position our amplifier.
1. Avoid parallel surfaces between walls
2. Avoid sharp corners.
Unfortunately, these aren’t great solutions, especially in small venues and if we are taking the aesthetic of our performance into account. We will address some better ways to correct bad acoustics.
Acoustic treatment provides compensation for uneven frequency responses within a room. An example of an acoustically treated venue that everyone has visited is the local movie theatre. Generally, professional theatres and performance venues that are suitable for bands will be acoustically treated.
Although acoustic treatment may guarantee us great sound quality, it’s not a requirement for a great sounding room. The proof of this would be in the recording techniques employed in the 70’s, and the lyrics from “Smoke on the Water” offer some great insight:
“We ended up at the Grand Hotel
It was empty cold and bare
But with the Rolling truck Stones thing just outside
Making our music there
With a few red lights and a few old beds
We made a place to sweat”
The sound of a room is not as important as its “feel.” Consider that many great recordings from the 70’s were not recorded in professionally treated rooms. In fact, they were recorded in basements, homes, manors and other peculiar locations. These tactics are not limited to older recordings. Dave Grohl recently recorded an album in his garage and Blink 182’s self-titled album was recorded at home.
Because the acoustics can differ so vastly from room to room, as musicians we are really faced with a new challenge in each venue that we play. What we should aim to do is embrace room acoustics musically by taking the room into consideration when playing our instrument. For example, depending on how “live” a particular room is, we will need to adjust our playing volume and intensity accordingly.
Repairing Bad Acoustics
A bad sounding room can be a performer’s worst nightmare. Particularly, as guitar players, we may enjoy performing at high volumes which may not work in certain venues. Thankfully, we are not stuck with bad acoustics, and there are a few things we can do in order to combat them.
1. Cardioid Microphones
This is an obvious solution that most venue owners already use. A cardioid microphone only picks up sound directly in front of it, diminishing the sound of the room but not eliminating it completely. The most popular choice for guitar cabinets is the Shure SM57. Of course, these microphones have other benefits too, such as eradicating feedback and not picking up unnecessary stage noise. You should also consider pointing the back of the microphone towards what you don’t want to hear.
2. Cabinet Simulation
It’s possible to use a high-quality passive DI box to send a direct signal from your guitar amplifier to the PA system. The device connects between the speaker output and speaker of your amplifier, eliminating the need for a microphone. This is a great tactic for live performances as you are still able to use your amplifier for stage monitoring. A popular option for guitar amplifiers is the Palmer PDI09, which is able to simulate an authentic speaker tone.
This is the most powerful tool we have at our disposal for repairing bad room acoustics. This shouldn’t be confused with an EQ effects pedal used with a guitar amplifier. This would be pre-EQ, but what we’re looking for is post-EQ. This is equalization applied on the mixing console to the master mix.
The issue is that many musicians lack technical knowledge in order to perform this task on their own. This is why professional bands are likely to employ at least 2 sound engineers in order to ensure a comfortable performance.
Luckily, acoustic issues can be resolved by the simple use of a parametric EQ.
Boost frequencies to locate problematic areas;
This is usually performed with a narrow bandwidth (or ‘Q’);
Cut problematic frequencies by reducing their volume.
The general rule of thumb here is that we should aim to “cut” frequencies and not “boost” any. Most rooms have acoustic issues in the 30 – 50hz range, creating unnecessary bass build-up and boominess. Generally, this is the first area we should explore for corrective purposes.
About the Author
Dean Hailstone has 20+ years playing experience and has performed in countless live and studio sessions. You can read more of his posts dedicated to the gigging guitarist on his blog found at PlayGuitarLive.com.