What a great weekend it was at the Marriott Hotel in Melbourne. Those who went along were treated to an impressive range of top shelf audio gear.  SoundAcoustics treated a room in conjunction with Equinox Audio, builders of superb Australian made speakers. Listening to these speakers was an absolute treat. I treated the room with a combination of the new Red series Viola panels (see below) and the HA600/75 hybrid panels, mounted on 1800 x 600mm MDF panels (3 mm). In one corner I had 4 x BT600/150 bass traps and another 4 BT600/150 at the first reflection points, functioning more as broadband panels.

For a smallish 4 x 5m space, the room sounded remarkably flat, and changing the seating position forward and back revealed very little change in low frequencies. Like ourselves, Equinox speakers are proudly Australian developed and manufactured, so it was a pleasure to create an environment to allow these speakers to really shine.

The Australian Audio & AV Show is on from 21 – 23 Oct 2011
Location: Marriott Hotel Melbourne, Cnr Exhibition & Lonsdale St, Melbourne, Victoria 3000

More information:

In October we there will be a unique opportunity to see SoundAcoustics panels in action in a fully treated room at the THE AUSTRALIAN AUDIO & AV SHOW Melbourne Marriott Hotel,
Friday 21st to Sunday 23rd October 2011. The installation will be in conjuction with some superb high end components from Equinox Audio. You will be able to hear (and enjoy!) the hand crafted Equinox speakers in an acoustically  treated environment. On display will be the BT120/80 bass traps,  HA600/75 hybrid panel and the SA600/75 acoustic panel (as well as a surprise new release!). At the THE AUSTRALIAN AUDIO & AV SHOW the exhibitors will be in moderate sized individual rooms, so will present similar acoustic challenges to the problems one might find at home, particularly in regards to low frequencies.

Most commonly, neighbours are annoyed by low frequencies from an audio system or a band rehearsing. Low frequencies essentially travel through any coupled structure, that is, through walls.  The low frequencies don’t need to be very loud to be annoying, and they can penetrate throughout the structure of neighbouring houses. The best way to stop low frequencies from escaping is to build a ‘decoupled structure’ within an existing room which is well constructed and sealed. The inner room can be an insulated stud wall structure sitting on rubber blocks, ideally on a concrete slab.

Unfortunately there is no standard for measuring corner bass traps, unlike flat wall mounted acoustic panels, which we have assessed at the RMIT acoustic laboratory in Melbourne.  So the most practical way of determining bass trap performance is by in-situ testing and measuring reverberation times at various frequencies. A bass trap can be tested as a flat panel in a reverberation chamber down to 100hz, the limitation of accurate measurement. A flat section of 180mm thick 32 Kgm/3 acoustic foam (thickness of BT120/80) absorbs at around 90% at 100 Hz. So at least we know we are off to a good start with the design of a trap, with guaranteed absorption at 100Hz.
When placed across a corner, with a large airgap behind, efficiency is greatly increased. Also, the width of the panel across the corner will increase the efficiency of the panel (the BT120/80 bass trap is 800mm wide) So what we need to assess with in-situ testing is how far below 100hz the bass trap continues to absorb.
For example an empty room, say 5 x 4 metres, will measure a reverberation time of around 1500 – 2000ms at the 64 Hz band.
The placement of 8 BT120/80 (2 in each corner) will reduce the reverberation time to around 500 – 700ms at the 64Hz band, which is significant in terms of improved low frequency definition. It is also useful looking at the effect  bass trap installation has on the frequency response of a room, in particular looking at peaks and nulls due to room modes.
There are many variables which effect the performance of bass traps, and whether they achieve the desired result, such as the size and dimensions of the room, the seating position, construction materials, audio system configuration, floor coverings, and adjoining spaces, just to name a few.

The first question you need to ask yourself before installing any type of acoustic treatment is: What am I trying to achieve? Generally speaking, there are two broad categories of acoustic treatment. The first is reducing the volume of harsh reflections and reverberation which are annoying to the ear in a wide range of situations. For example, harsh reverberation caused by cymbals, snare drums, guitars in a rehearsal room, or in a restaurant, the clatter of cutlery and chatter (due to hard floors and walls). The second category is the specific application of acoustic treatment, in order to create a more accurate listening environment, such as a recording studio, home theatre or audiophile room.

For the first category, any acoustic material that absorbs high frequencies is suitable. This can be standard acoustic panels*, carpet, drapes, or soft furnishings. Roughly speaking, all these materials will absorb 500hz and higher, reducing harsh higher frequency reflections. To put this into perspective, middle C on the piano is 261 Hz.
Acoustic treatment for the second category requires are different approach. To create an accurate listening environment, the acoustic treatment needs to be effective over a wide frequency range. This requires bass trapping for low frequencies (usually mounted in corners) and broadband acoustic panels (best at first reflection points). Most importantly, if you are on a budget, start with bass trapping first. Low frequency reverberation interferes with your ability to accurately assess the volume of low frequencies when mixing and listening to music. The most common symptom of an unbalanced room, in a recording studio, is a mix which translates poorly to other playback systems.
In an audiophile room or home theatre, it is low frequencies that ‘jump out’ or conversely, disappear.

*Most acoustic panels on the market (such as our own AT600/40) are only ‘mid/high’ frequency absorbing panels. For example, eggshell foam or similar. The ability of acoustic foam to absorb lower frequencies is directly related to thickness. For example, the SA600-75 (75mm thick) broadband panel absorbs affectively down to 200Hz, where as the AT600-40 (40mm thick) absorbs down to 400hz. Which is virtually an octave difference.

Acoustic foam panels can be coloured or “flock coated” which is a soft fibre type finish similar to suede or velvet.
The panels are coated in a thin layer of adhesive, statically charged and placed in a chamber where the flock is attracted to the foam. Coating has no adverse effect on acoustic performance. The standard colour of polyurethane acoustic foam is charcoal grey, so the underlying colour of the foam can show through with light colours. Bold colours such burgundy give a very classy and robust finish that is easy to clean with a damp cloth. Acoustic panels are coated to order, so there is a turnaround time of typically two to three weeks. The cost of coating acoustic foam panels is between $15 and $30 per panel, depending on size.
Acoustic foam panels can become a design feature with a bit of creativity. In a home theatre or home studio, the most first application of panels should be at the first reflection points, which are the side walls near the speakers, and also on the rear wall. By placing a mirror on the wall at the panel position, you should be able to see the speakers (from the listening position). Panels can be placed on angle, or spaced apart up to fifteen centimetres.
The flat FP600-60 acoustic panel can look very simple and stylish just using two contrasting colours.

I get lots of questions about vocal booths, and the solutions are either expensive or a lot of work. If you need a quick and dirty vocal booth, this BT270-600 pressure zone trap configuration works great. The staple gun channels are what makes this possible.

Most home or project studios are located in smallish rectangular rooms, creating a real challenge in creating a relatively accurate listening space. Parallel walls reinforce and nullify harmonic frequencies, creating peaks and dips in the frequency response, particularly between 50 and 250Hz. A common mistake is the overuse of thin acoustic panels (50mm and less), which provide virtually no absorption of frequencies below 200Hz. This is not a balanced acoustic treatment, and makes recording and mixing music a nightmare.
Every small room requires bass trapping, but how much? There are many different bass traps on the market, the most common being semi rigid fibreglass traps, membrane traps and acoustic foam traps. Which is best? In reality, all well designed traps are effective. The real question is, how much trapping do you need?
Much of my work is acoustically measuring recording and listening rooms. Many of these rooms already have well regarded (and expensive) bass trapping in place, but still exhibit a very lumpy frequency response.
The problem is, there simply isn’t enough bass trapping in place to overcome the acoustic characteristics of the room. It’s often a matter of experimenting with as much bass trapping as practical and measuring the impact it has. In some cases, it’s just not possible to get a room within plus or minus 15 db, due to the dimensions and construction of the room.
A good place for bass trapping in small rooms is the ceiling. The RAM400-1000 traps are ideal for this application, as they can be easily installed with a staple gun.
The reality with bass trapping is that it’s often a case of experimentation, and small rooms generally require a substantial amount of trapping.