Updated: Sep 10, 2020
Room acoustics is a tiring and tedious affair, especially if you are already settled into a nice cozy environment and dread the word renovation.
Spend a small fortune or mortgage your kids - either way, there's no ceiling on how much you can splurge on the components that make up a home studio or a home theater. And it’s just the beginning, since the single, most important, factor in bringing out the best in your sound system is the room they play in!
By The Hashtag Studio.
The truth is, room acoustics need not be a year-long project where the better part of your savings are invested and exhausted.
“ Arming yourself with a little research and some intuitive thinking can generate ideas that work as well, if not better than professional acoustic treatment.”
To Begin With
Ensure sufficient ventilation for yourself and your equipment. Split Air Conditioners works fine these days and even micro fans like the ones used inside a PC can be mounted behind the amplifier to provide the necessary cooling.
Minimize the use of glass in your room since windows and large glass artifacts can cause unwanted reflections.
Use drapes to cover large windows, The fabric used to make drapes should be twice the size of the glass area that is to be covered.
Don't go bare, even if you dare, Bare looks good in brochures, but in real world conditions, a bare room will sound only as good as a tin can.
Experiment with positions when it comes to putting your speakers but when it comes to your sofa, stick to the basics and make sure it sits in the middle of the front two speakers and directly in front of your screen.
The first step on your road to home theater nirvana should be chalking out the dimensions of your "new" room. It would be impossible to predict the nature of acoustics for a room before actually constructing it, but following some basic principles will ensure that you start out on the right foot.
Room dimensions are a make or break situation. No matter what the treatment, if your room's inherent dimensions defy the laws of physics and psychoacoustics, there isn't much you're going to get by spending lakhs on interior design. Every room generates standing waves' which interact with the way low-frequencies (bass) are reproduced. In simple language, if your room is shaped wrong, you won't feel the explosions on your home theater system just like in the multiplex. So what do you do? Since we're talking about creating rooms from scratch, this bit is easy. Just avoid constructing rooms which have equal dimensions or dimensions in multiples of each other. For eg, a 10 ft height x 20 ft length x 20 ft width would spell disaster in terms of getting the right bass from your sub woofer. A room where all three dimensions (HxWxD) are non-divisible by each other is theoretically a better room to place your speakers. This theory can best be described with an analogy of a bouncing ball in a square box and a triangular box. Think of the ball as the sound wave and the box as your room. The ball will take longer to come to a halt in a square box than in a triangular box. For practical purposes, living in a triangular room would be slightly claustrophobic, so the next best thing would be to have irregular room dimensions and make the best of what you have.
“In the world of acoustics, No. 1 is usually not the best.”
First order reflections, for instance are reflections caused by sound hitting a side wall before reaching the listener, arriving at a slight delay compared to sound directly from the speaker. This causes your brain to miss out on micro details and it starts applying its own error-correction mechanism. In the meantime the music you are listening loses the warmth and the spatial information that makes music interesting when you're sitting in the sweet spot (main listening position). What you get instead is a harsh bright sound that doesn't sound pleasant for too long and you're forced to lower the volume due to ear fatigue.
HIGHS AND LOWS
High ceilings are better than low slung false ceilings and even better if they are sloped. Parallel surfaces cause sound to ricochet between walls, adding unwanted reflections that are delayed (in comparison to the direct sound from the speakers) and distort the phase information in your music. Eliminating parallel walls may be almost impossible but experimenting with your ceiling isn't.
Breaking up a flat surface with irregular columns and troughs is a good idea in any home-theater setting. Materials that absorb, diffuse and reflect sound in the right dosage can bring out the potential hidden in walls and ceilings. Damping material like rock wool or acoustic foam is a good idea, if applied with care. Too much of it can suck the life out of your music, and too little will set off a series of echoes that can make any Record sound like it was recorded in a church! Simple, everyday objects like books, rugs, curtains and coffee tables can be placed wisely to create a pleasant effect.
Acoustic treatment of bare walls during construction can be quite a handful. At this stage, you will have to scout the market for the required materials (see Surface Treatment). You will also need to work closely with your architect or contractor during the application of the selected material to your walls. Although there are many materials available, the most practical and efficient nowadays is rock wool that is available in sheets. The chosen material will have to be held in place by a thin plywood sheet, which needs to be perforated so that the absorptive material behind it can work its magic. The number of perforations in the ply will determine the absorption coefficient. As a thumb rule, 25 per cent of the entire treated surface must be perforated. Ideally, this should be done with randomly placed circular holes of varying diameter.
“Remember, symmetry is bad when it comes to acoustics. Side walls, rear walls and walls facing the speakers are the most critical areas when it comes to acoustic treatment.”
Even with rock wool, more is not necessarily better. Layers of varying thickness will best absorb different frequencies. To have any effect on frequencies lower than 100 Hz (bass), you will need a rock wool layer at least 4 inches thick upto a height of about 3 ft from the floor. The rest of the wall can be coated with rock wool of decreasing thickness all the way to the ceiling. If this is too much to handle, treat specific points like the first order reflection points (see Reflections) which are easy to detect. After placing your speakers in their final location, ask a friend to hold a mirror on the side wall and sit in the main listening position (sweet spot). Ask your friend to move the mirror along the wall at the same height as the tweeter (loudspeaker that produces high frequencies) of your speaker. The point on the wall where you can see the reflection of the tweeter is the first reflection point.
The wall behind the speaker is also a major source of detrimental reflections. Hang a few paintings or even soft toys just to absorb some of the stray, backward energy. For most people, the TV screen is placed at this location, so a simple but elegant rug draped over the screen when not in use should do the trick. Sound waves move around the room in a trajectory similar to a light source, but since it's invisible, we use tricks like mirrors and in some cases, laser inferometry to "see" these reflections.
At this first reflection point, you can either absorb or diffuse the sound depending on the loudspeakers in use and their sonic signature. Speakers of the direct/reflecting variety or "omnipolar", which radiate sound in more directions than just forward, need absorption on the side and rear walls to keep the sound from bouncing around the room until it dies. Brands like Bose, Adam Audio and Genelec make speakers that adhere to this design philosophy. The phenomenon where reflected sound reaches the ear slightly later than direct sound is called delay. By controlling the delay in your room, you can define how "dead" or "live" your room is. Usually, a middle path is best for everyday listening.
SOUND PROOFING VS ACOUSTIC TREATMENT
Remember, sound proofing and acoustic treatment are two entirely different things. Acoustic treatment might not cut down on the sound escaping your room but it will decrease the amount of external noise entering your room, thereby increasing the dynamic range of your system. Having higher ambient noise entering your listening room will make you increase the volume of your system, causing sound distortion and stressing your hearing. On the other hand, if you control the ambient noise entering your room, you can listen to your system at a much lower level, preserving the nuances and also extending your listening session because your ears won't get fatigued as quickly.
In the end, making a dedicated home-studio or a home theater is an enlightening experience that shouldn't be looked upon as daunting. If you stick to the yardsticks and get your homework done, it can bear the rewarding results for you.
Wall: Rock wool, dampening fabrics, foam and in some cases even acoustic wallpaper can be used as a retrofit treatment.
Glass: Heavy drapes for acoustic reasons and a blackout drape if you're using a projector is a must.
Floor: A minimum of 1/2 inch carpeting in front of the loudspeakers helps immensely in cutting down floor reflection that can otherwise cause the sound to get bright and edgy.
Ceiling: Specific points on the ceiling can be treated with diffusors that can be made out of foam or fiberglass sheet or even gypsum board can be used.
By The Hashtag Studio.