The AUVA benefit - a natural extension to your loudspeaker

Stack Audio is a British manufacturer of award-winning hi-fi products. We aim to bring music to life by focusing on vibration dissipation and isolation, revealing more detail, texture, and transparency. The AUVA loudspeaker isolators have been conceived to enable your speakers to perform at their best.

Loudspeakers are built around the idea that their drivers (tweeters, woofers, sub woofers) are in place to move air and it is these pressure changes that we “hear”. The placement of the drivers in the cabinet and the cabinet itself are a way of ensuring the drivers are integrating correctly. The designers will have spent months fine tuning the crossover design and transducer placement phasing and tonal balance.

It is also important that the cabinets are stiff and as motionless as possible, so the drivers move air rather than the cabinet. There will be vibrational energy created by the drivers and many speaker designs have bracing and other innovations to help minimise the effects. The AUVAs are an extension of that approach, designed to enhance the purity of the sound reaching your ears.

Coupling and decoupling

Traditionally there are two opposite approaches to supporting loudspeakers in situ – coupling or de-coupling. Coupling typically uses metal spikes or cones that hold the loudspeaker rigidly to ensure there is minimal movement and physically connecting the loudspeaker to the floor. It is a misconception that spikes allow energy to travel only one way because the end of the spike is pointed. In fact, just as vibration travels down the spike into the floor, the spike also transmits any floor vibrations back up into the speaker through the same fine point the vibrations have drained through. De-coupling typically uses a compliant material (elastomer, springs, rubber cones, foam etc) that attempts to isolate the speaker from the listening room floor, absorbing some of the vibration. For speakers to work effectively you need to satisfy two seemingly contradictory aims: hold a loudspeaker perfectly rigidly and absorb vibration.


Particle Impact Dampening 

The AUVAs have been designed to combine the best qualities of both spikes and isolators. Without using soft compliant parts, the AUVAs ensure that the rigidity and precise positioning of the speaker system isn’t compromised. Rather than absorb vibrational energy via lossy compliant materials, AUVAs capture the vibrational energy using particle impact dampening, dissipating it near instantaneously. This process happens in cells inside the AUVA which has a rigid outer shell that still holds the loudspeaker precisely.


To understand the importance of vibrations affecting a hi-fi system, it is necessary to think about what happens to the listening room and the air within it when a speaker is operating. The movement of the speaker drivers creates the sound waves we hear. Pressure deviations from the movement cause particles in the air to vibrate, cascading with each other until the sound wave reaches our ears, which our brains process as music.

Listening to music at its best is an emotional experience, whether live or at home via the hi-fi. In the same way that live music venues pay significant attention to the acoustics in the hall or theatre, setting up your hi-fi listening room is equally important. In the live music venue and at home, managing vibrations (good and bad) is the key to hearing the clarity, timing, and spatial detail in the music.

One of the reasons why isolation is important is that we have loudspeakers creating lots of vibrational energy. By their nature loudspeakers have moving parts generating vibrations problematically across a broad range of frequencies – every forward motion in a speaker cone has an equal and opposite push in the other direction. It is necessary to energise the air in the listening room to hear a realistic and engaging sound. However unwanted movement and vibration feeding into hi-fi equipment is undesirable.

In simple terms it is unwanted energy that creates distortion. It has long been understood that isolation from vibration is important for electronic components to function correctly. This is true for all hi-fi equipment with components and circuitry that are sensitive to microphony, where mechanical vibrations are turned into unwanted electrical signals creating noise. Streamers, DACs and DSP components all have sensitive digital clocks (crystal oscillators) that are critical to their performance. An oscillator works by resonating at a precise frequency so any external vibration can mask this precision and affect the performance of the clock. This is one cause of jitter which can be heard as an edgy or brittle quality to the sound.

Bass radiated through the floor can create resonances that amplify the low frequencies, muddying the bass notes and change the balance of the music. This compounds the bass reinforcement that comes from walls and room corners. Room transmitted vibrations also come back into the loudspeaker itself, causing internal reflections in the speaker cabinet resulting in audible smearing and loss of clarity.

Precise positioning

Loudspeaker positioning is a key part of setting up a hi-fi system. The relationship of the speakers to each other and to your listening position is part of creating a realistic soundstage. If one speaker is closer to you than the other, its soundwaves will reach you before the other speaker and the stereo effect won’t be correct. Even a few millimetres will have an impact, especially for the high frequencies with very short wavelengths. It is the high frequencies that create the stereo image and the perception of a 3-dimensional soundstage in our brains. They are essential to ‘hearing into the music’, conveying the emotion of the original recording and the realism of vocals. Without these being reproduced clearly music becomes background audio wallpaper.

The placement of the drivers in the cabinet and the cabinet itself are a way of ensuring the drivers are integrating correctly. The designers will have spent months fine tuning the crossover design and transducer placement phasing and tonal balance.

Absorbing vibration whilst maintaining rigidity

The problem as we’ve noted is that speakers need to remain rigid to ensure the precise delivery of the musical notes and an accurate and realistic sound stage. Also, if the compliant solutions are not properly designed for the application they can amplify the vibration. Using spikes, cones, or a single solid piece of material such as acrylic will hold a speaker rigid but vibration travels straight through to and from the floor with no effective isolation and back up to the speaker. It remains true that for vibration to be removed you do need movement. So how can you reconcile this conflict of needing movement and rigidity at the same time?

The AUVA loudspeaker isolators aim to combine precise stable speaker placement with effective energy absorption and dissipation, so you don’t sacrifice spatial detail, precision, and nuance from your speakers. They use a carefully modelled and precision-machined solid outer shell to retain structural integrity at the same time transmitting the vibrational energy to particles inside. The particles are excited by the energy and move, colliding with each other and the walls of the cells. It is the movement and the collisions of the particles that convert the vibrational energy into heat in a process known as particle impact dampening.

To visualise the process, imagine a ball dropped onto a hard surface, and one dropped from the same height onto a sandpit. The ball dropped on the hard surface bounces repeatedly only coming to rest when all the kinetic energy has been dissipated. The ball dropped onto the sandpit stays where it impacted, the thousands of grains of sand having dissipated the energy quickly and effectively.

Our patent pending AUVA technology uses multiple finely tuned cells. Various materials including tungsten are used to ensure that the broadband absorption is as linear as possible. Maximising the contact between the AUVA cell walls and the particles ensures a high level of vibration can be dissipated.

Combining rigidity with advanced vibration dissipation results in a more immersive listening experience from your system. Try them for yourself and you be the judge.

Summary of the acoustic benefits of AUVA Loudspeaker Isolators

  • Ensures the rigidity and stability of the loudspeaker position, preventing loss of sound stage detail through multi-axis movements
  • Absorbs speaker cabinet vibrations reducing floor radiations that amplify the bass and feed back to the hi-fi electronics
  • Absorbs room boundary vibrations from reflected soundwaves and prevents them passing back up to the loudspeakers
  • Reduces the vibrations and noise-nuisance in rooms adjacent to the listening room
  • More defined bass, clearer vocals and high notes, and a more distinct sound stage

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