Loudspeakers and amplifiers add merit to a home theatre, but installers tend to underestimate the importance of acoustic treatments.

Anthony Grimani has spent a lifetime studying and testing the perfect audio layout of a home theatre, and as president of two US-based companies – Performance Media Industries and Media Specialty Resources – he knows a thing or two about achieving the perfect sound in a room.

According to Anthony, acoustic treatments play a fundamental role in the business model of the AV industry and should become part of the client’s overall budget, rather than the installer’s last-minute ‘band aid’ solution.

“The final link between the speakers and the listeners is the air in the room. And the purpose of acoustic treatments is to tune the room so that the air can enhance the sound as opposed to disturbing it,” he says.

“This doesn’t take away from the fact that the room also needs to have a nice design, so when the user walks in they feel like they have been transported into this beautiful space. It’s a challenge to find a way to make that design integrate acoustically and optically into the needs of a home cinema.”

Aside from leaving treatments until the last minute, Anthony says there are five fundamental errors installers make when trying to achieve perfect sound in a room.

“The most common mistake is doing nothing, which is being guilty by omission. That’s not a mistake of acoustics, it’s just failing to realise how great an effect it has.

“The practice of using acoustic treatments in a room is out there, but it’s still a relatively new field. However, there is an increased sensitivity to the fact that this matters.”

In his opinion, the biggest problem is simply the fact that many people haven’t experienced the difference that acoustic treatments can offer to a room.

“It’s hard to describe, but once you sit there and hear it for yourself, everything falls into place,” Anthony says.

“At the CEDIA US Expo that took place in Denver three years ago, we were given the opportunity to build two home cinemas side by side. One was equipped with very good equipment but no acoustic treatments; the other had the same equipment laid out the same way but the room was treated. You could walk from one room to the other and it was stunning to hear the difference.”

The second most common mistake is a trend that Anthony describes as “the solution of ease”, which basically involves too much absorption at the wrong frequency.

“We’re seeing a fair amount of this in the US, which is the act of covering the whole room with 2cm to 3cm of ‘fuzz’ – this is either foam or thin fibreglass that covers the walls, but it may actually be worse than sonically reflected walls. The reason for this is that material on the walls will absorb the high frequencies, but none of the mids and lows.

“That means you have no room for reflections at high frequency, but you have plenty of it at 500Hz in the mid-range, where most instruments are. So what happens is that room still echoes, but it’s lost all of its life because the high frequencies are sapped out.”

The third point that Anthony refers to on the list is the simple habit of mistaking acoustic treatments for something other than its intended purpose.

“It’s what I loosely call, ‘sound isolation’ or ‘sound proofing’. People may think that putting panels up on the wall will reduce the amount of noise that is going to the bedroom next door, or the kids’ room upstairs, but it doesn’t one bit.

“Adding sound isolation to a room is a completely different process. It’s an entirely different science that is handled during the initial design and construction phase – you can’t get there just by putting panels up on the wall.”

Coming in at number four on the list is the habit of creating uneven amounts of absorption, diffusion and bass trap in the room, which ultimately throws off the balance of the audio overall.

“When people add in acoustic treatments they may decide to install absorber panels that suck out sound reflections, which is a first step. But for a good quality home cinema you also want to have some scattering of the sound in the room. The purpose of scattering devices is for the sound that hits them to get scattered evenly in the room. And the idea of those panels is to make the room feel bigger than it really is,” he says.

“A well-treated room needs to have absorbers that are relatively thick, about 100mm is ideal, covering only about 20% of the surfaces. Scattering devices, also known as diffusers, can then cover another 20% of the surface and bass traps that usually absorb the bass at the corner of the room can also cover about 20% of the corner surface.

“If you follow that simple recipe, you’re going to end up with a room that works well. Once a dealer experiences the benefits of diffusion, they won’t go back.”

His final point on the list of ‘what not to do’ refers to taking shortcuts and substituting acoustic treatments for a single product, such as an amplifier.

“I hear all the time that if you use a sound system, like an amplifier, that has an equalisation system built in, you don’t need acoustics control anymore. To be honest, that comes from a lapse in the communication from manufacturers who say that this is going to compensate for the sound of the room,” he says.

“What it does is compensate for the low-frequency effects of the acoustics of the room only. The fact that a room echoes cannot be corrected by a device that changes the frequency balance of the sound. So a common mistake involves people thinking they can skip acoustic treatments because there is an amplifier that’s going to take care of it.”

On the other hand, Anthony does admit that people tend to believe that a room with acoustic treatment surpasses the need to tune the selection of loudspeakers to the room.

“That’s not true either. A good home cinema – at any level – is a combination of a well-treated room with that rule of 20% absorption, 20% diffusion and 20% bass trap, coupled together with a sound system that can equalise for the room. If you can achieve both things, the results are glorious.”