Room Acoustics Treatments

Standard Volcano (2 parts) 102 cm (40") (h) x 38 cm (15") diameter

Additional centre module 42.5 cm (16.7") x 38 cm (15") diameter

The Volcano is the latest in the family of variable resonators developed and manufactured exclusively by Acustica Applicata. It is the new entry level model in the family that includes the Polifemo and Phemo. It is designed to improve the sound of any audio system, in any room.

It is not just an ordinary corrective tool, it is has been developed for those audiophiles who seek an improved sound that is more refined, more elegant and that recreates the “live” event. Improvements to the sound stage, the finer details, the nuances created by the musician, the texture and timbre of instruments and their sound.

In any listening room there are two, or more, loudspeakers that produce a sound pressure into a space surrounded by walls. Only part of the sound produced by the loudspeakers arrives at the listener’s ears directly. A large proportion of the sound arrives at the listener after having bounced off the walls at various reflection points. These reflected sounds are arriving later than the direct sound, and at variable amounts of delay. These reflected sounds also have to pass through the area occupied by the loudspeakers. This all creates distortions and a confused sound picture.

To illustrate this point in a very simplified manner, imagine a 3-dimensional room as a 2-dimensional surface, rather like a rectangular swimming pool. Then imagine two identical spheres dropped down simultaneously into the pool, away from the sides, at points where you would position of a pair of loudspeakers in a listening room. The two spheres entering the water cause circular waves that move outwards. These waves spread, with a certain frequency, enlarging themselves towards the closest swimming pool walls, and from the point of impact new waves emanate in the opposite direction. These new waves in the opposite direction will either reinforce or cancel the first waves coming from where the spheres entered the water.

The spheres generate waves in a circular fashion and some of these propagate themselves towards the inner area of the pool, and around the halfway point will “crash” into each other. In this particular position, the waves will interact with each other and very rapidly change so they are no longer like their original form. They will be warped and distorted by all the collisions between them, and from those waves coming back from the walls. They will then travel all over the swimming pool until they gradually disappear.

Music is obviously much more complex than the simple, single wave. The example illustrated above is of a single, low frequency wave, but the low frequencies generated by an audio system are at many different frequencies, and much more complex and more intricate than a 2-dimensional simple oscillatory motion.

Playing music in a room generates many different frequencies simultaneously. Additionally, stereophonic sound will be more like two spheres dropped that are not the same size, or the same weight, hence generating waves of different energies and difference frequencies. This whole phenomenon increases in complexity hugely once you consider a 3-dimensional room with a whole bunch of waves colliding in space and creating room distortions.

In a listening room there 3 to 5 positions where these distortions become extremely significant: Two are along are at the lateral walls closest to the sides of the speakers.

Two are at the wall behind the speakers, again closest to the speakers.

The most important position is between the speakers in the middle of the sound stage. This area has the most turbulence where waves are colliding with themselves, they increase their energy or, more crucially, can cancel their energy.

So treating this area with a suitable acoustic device, designed for this purpose, results in a major improvement in sound quality. The 3-dimensional stage increases significantly, the illusion of hearing into a much bigger space of the recorded venue. Transparency and clarity are noticeably better; a more correct tonal balance ensues with more impact and depth of the lower frequencies. Instruments and voices become more detailed and it is possible to perceive a person standing there, not just a voice. But above all is an outstanding increase in dynamics.

Acustica Applicata have researched extensively this area of room acoustics phenomena and developed variable resonators such as the Polifemo. Now a new variable resonator has been born, which is easier to use and produce a more balanced and more in-phase sound. The VOLCANO was designed for exactly this position, in the centre of the sound stage, and it always results in an improved and more natural sound quality. The sound is much more like the concert hall experience.

The standard VOLCANO is 105 cm (41”) tall with a diameter of 38 cm (15”). The body is made from pure transparent Plexiglas with ends made from MDF uniquely shaped to a specific design. The base has a port of 10.5 cm (4.1”) diameter into which is a cylinder made from a flexible acrylic which can be easily moved up and down to tune the resonant frequency to be addressed. The height of this cylinder within the Volcano tunes it to obtain the best depth and speed of the low frequencies within the room.

By playing a track with good low frequency content for a couple of minutes or so, and moving the cylinder up and down, it is easy to hear the sonic differences. A few changes of height with the same track will determine the best tuning for the bass frequencies, in the position being tested, for the listening room and the audio system being used. There is a scale on the cylinder that allows the listener to raise and lower it with accuracy during the listening tests.

This adjustment to tune low frequencies takes its inspiration from a device used by lute builders in the early 900s: its name was Tornavoz and was used to increase the sonorous projection of sound and the low frequencies of the instrument.

In the middle of the VOLCANO is a membrane stretched within a wooden frame which can be orientated from vertical to a horizontal position by an external knob. The membrane is made of a special acoustic material. By angling this membrane it is possible to adjust the high frequencies: the vertical position give more texture and sweetness to the high frequencies, whilst the horizontal position gives more body to the mid frequencies. In most applications, somewhere between the two is tuned to taste.

The top of the Volcano is specially shaped so that the internal and external curves are different. The underside of the top is a shallow curve of very specific shape. This curved shape and diameter of the crater is of fundamental importance and essential to the performance of the Volcano. There is a fixed hole in the centre which is also shaped with calculated curves and diameters and works in conjunction with the shallow “crater” of the top. These parameters have been extensively studied by Acustica Applicata, going through several prototypes and hundreds of hours of listening and measurement tests. This top part, shaped like a crater with a hole in it, is the inspiration for the name.

The Standard VOLCANO is in two parts and simply links together by placing the top section onto the wooden flange of the bottom section. These parts are not glued as it just sits into a machined groove within the wooden flange. This also allows for ease of cleaning the internal parts, and for adjustment of the tuning cylinder in the base. (In practice, it is also possible to adjust this tuning port from the outside from underneath the base).

The standard VOLCANO is effective from 35 Hz and upwards. By adding an additional extension Plexiglas module, the lower frequencies treated is starts from 25 Hz and upwards. The overall height of the Volcano is then increased by 42.5 cm (16.7”) to 144.5 cm (57”). This can extend the use of the taller Volcano to corner positions in very large rooms or attic spaces with angled ceilings or that are mansard shaped.

The VOLCANO is delivered in one carton, the same size as a DAAD No. 4. The two sections are separately packed inside. It takes no time at all to unwrap these sections and place the lower part in the position to be treated, usually between the loudspeakers. Then place the upper section into the groove in the appropriate wooden flange at the top of the lower section. No fixing or gluing is required.