INVENTED BY PSI AUDIO · PATENTED INNOVATION
AVAA TECHNOLOGY.
THE ACTIVE WAY
TO CONTROL BASS.
A different approach to bass traps.
Absorb room resonances. Reveal your sound.
We invented AVAA — the Active Velocity Acoustic Absorber. Discover the patented technology behind the AVAA C214, and why active bass absorption changes what is possible in a compact space.
THE ORIGINAL ACTIVE BASS TRAPS. AVAILABLE ONLY FROM PSI AUDIO.
AVAA C214
15–160 Hz · Active bass absorption
01 / BASS DEFINITION
LET NOTES END.
Shorter modal decay helps separate bass notes and reveal transients.
02 / LISTENING CLARITY
HEAR THE DETAIL.
Less lingering bass means less masking, clearer balance and more confident listening decisions.
03 / PRACTICAL FREEDOM
KEEP YOUR SPACE.
Compact, movable absorption. No room calibration and no connection to your audio signal chain.
UNDERSTAND THE PROBLEM
WHAT ARE
ROOM MODES?
Room modes are the natural resonances of an enclosed space. Sound reflects from the walls, floor and ceiling. At frequencies related to the room’s dimensions, these reflections form standing-wave patterns.
The result is a fixed pattern of high and low acoustic pressure. The same bass note may sound excessive near a wall and almost disappear elsewhere. With insufficient absorption, its energy also lingers after the source stops.
This is why moving your head or listening position can change the bass so dramatically — and why an otherwise excellent system can sound boomy, uneven or unclear.
A room mode has two audible effects:
uneven level and lingering energy.
PRESSURE
PRESSURE
PRESSURE
4 m room length ≈ 43 Hz first axial mode
Illustration of a single idealised mode, not a room measurement. At about 20°C: f = 343 / (2 × L). Real rooms contain many overlapping modes.
WHY THE ROOM KEEPS RINGING
Length, width and height each contribute resonances, with further modes involving several dimensions. Absorption adds damping, allowing stored sound energy to dissipate more quickly.
Go deeper: pressure, velocity and wavelength
For an axial mode between rigid parallel boundaries, the separation equals an integer number of half wavelengths. Acoustic pressure is highest at the boundaries, while particle velocity is lowest there. AVAA uses active control to make a high-pressure location absorb energy.
THE AVAA PRINCIPLE
SENSE. CONTROL. ABSORB.
An active bass trap removes acoustic energy from the room. The C214 applies our patented AVAA principle continuously across 15–160 Hz, without being tuned to individual resonant frequencies.
01
SENSE THE PRESSURE
Internal microphones monitor acoustic pressure at the absorber. The system responds to sound already present in the room, regardless of which loudspeakers or other sources produce it.
02
CONTROL THE LOAD
The electronics control the actuators to establish a very low acoustic impedance at the absorber. Impedance describes the relationship between acoustic pressure and particle velocity.
03
ABSORB THE ENERGY
The resulting acoustic load draws in low-frequency energy. Instead of continuing to reflect around the room, part of that energy is absorbed, so resonances decay more quickly.
Like a much larger opening in the wall.
This is a useful acoustic analogy: an opening lets energy escape rather than reflect. AVAA produces an absorbing effect much larger than its own physical surface, without requiring an opening in your room. The equivalent area varies with frequency, position and room conditions.
WORKING ON THE ROOM ITSELF
ABSORPTION.
INDEPENDENT OF
YOUR SIGNAL.
Room EQ adjusts the signal sent to your speakers. It can reduce excitation at certain frequencies, but it does not add acoustic absorption to the room. AVAA acts on the room’s acoustic energy directly.
AVAA is also different from a noise-cancelling system designed to create a quiet point at a listener’s ear. Its local control loop creates an absorbing acoustic boundary. There is no music input and no need to integrate it with your amplifier, DAC or monitoring chain.
YOUR SPEAKERS. YOUR MUSIC.
Use AVAA with studio monitors, a hi-fi system or a home cinema. It responds continuously to the acoustic field and can act on multiple modes within its operating range.
PART OF A COMPLETE ROOM DESIGN
Keep appropriate speaker and listening-position choices, plus passive treatment for mid- and high-frequency reflections. AVAA focuses on bass resonances; it does not replace every aspect of acoustic treatment or provide sound isolation.
LOOKING FOR PASSIVE BASS TRAPS?
THERE IS ANOTHER
WAY TO TREAT THE LOW END.
If you are comparing corner bass traps, acoustic foam, mineral-wool panels, membrane absorbers or Helmholtz resonators, start with the problem you need to solve: which frequencies ring, for how long, and how much space can you give to treatment?
WHAT PASSIVE BASS TRAPS DO WELL
Porous absorbers dissipate energy through losses in the material. With suitable depth, area and placement, they provide valuable broadband treatment. Resonant passive absorbers use a panel, membrane or cavity to target lower frequencies.
Passive treatment does not need power and can be integrated into the room’s construction. Its performance depends on the complete design: a thin acoustic panel and a large, purpose-built bass trap are very different tools.
WHERE ACTIVE ABSORPTION HELPS
Long wavelengths make deep-bass treatment challenging when space is limited. AVAA C214 provides broadband low-frequency absorption in a slim enclosure, making it a practical alternative to extensive passive bass trapping.
You do not have to choose one approach for every frequency. AVAA can handle low-frequency decay while passive absorbers and other treatments address the rest of the room.
| Consideration | Porous bass traps | Membrane / Helmholtz | AVAA C214 |
|---|---|---|---|
| How it works | Friction and thermal losses in porous material. | A resonant panel or cavity dissipates energy. | Active control creates an absorbing acoustic load. |
| Low-frequency coverage | Depends on depth, material and air gap. Thin panels have limited deep-bass absorption. | Designed around one or more resonances; bandwidth depends on tuning and damping. | Broadband absorption from 15–160 Hz, without tuning individual modes. |
| Space in the room | Deep-bass treatment often requires substantial thickness and surface area. | Depth and surface area depend on the target band and design. | Compact enclosure: 21 cm diameter and 64 cm height. |
| Setup | Choose material, thickness and placement for the room. | Match resonant design and placement to the problem. | Place at a suitable pressure maximum, connect power and switch on. No room calibration. |
| Best role | Broadband treatment, including mid- and high-frequency reflections. | Targeted passive treatment of selected low-frequency problems. | Low-frequency decay control where space for passive bass trapping is limited. |
Comparison of operating principles, not a universal ranking of products. Passive absorber performance varies widely with design and installation.
MEASURABLE ACOUSTIC CHANGE
SEE THE BASS
DECAY FASTER.
In our published example, a 20 m² studio with two large loudspeakers had a pronounced resonance at 32 Hz. Adding two AVAA units reduced its decay time by 300 ms, with improved tonal balance and low-frequency imaging reported for that room.
01 / AVAA OFF
02 / TWO AVAA UNITS ON
Published 20 m² studio example
READ THE TIME AXIS, TOO
A frequency-response curve shows level across frequencies. A waterfall also shows what happens over time. Look for resonant ridges that persist: shortening them is central to what bass absorption achieves.
Historical AVAA technology demonstration. These images are not presented as a new C214 measurement or a C214/C225 comparison. Results depend on the room, unit count, operating level and placement.
SMALL DEVICE. LARGE ACOUSTIC EFFECT.
WHAT DOES
“EQUIVALENT ABSORPTION
AREA” MEAN?
Equivalent absorption area expresses an absorber’s effect as the area of an ideal absorbing surface. It is measured in square metres – not litres, floor space or a guaranteed number of replacement panels.
Our published AVAA illustration shows a frequency-dependent range reaching several square metres. The accompanying technology explanation describes approximately 1–8 m² depending on the conditions. At 5 m², the comparison corresponds to about 25 times the C20 reference surface, or 40 times the C214 reference surface.
This is the context behind the C214’s “up to 45 times” absorption claim. It is an equivalent-area comparison, not a fixed multiplier at every frequency or in every room.
Original AVAA/C20-era graph retained to explain the principle. It is not a current C214 certification curve; do not use its upper frequency endpoint as the C214 specification.
By lowering impedance locally, AVAA influences the air around the absorber. Our original explanation describes a region extending roughly 1–1.5 m around it. That is a local interaction region, not the size of the room it can treat.
WHERE IT ALL STARTED
THE ORIGINAL AVAA.
TESTED AGAINST PASSIVE ABSORBERS.
This historical test compares decay at a 39 Hz room mode with the AVAA C20, a Helmholtz resonator, a panel absorber, a porous absorber and the empty measurement room. The absorbers were optimally positioned for the published comparison.
A HISTORICAL DEMONSTRATION
The AVAA trace decays substantially faster in this particular test. It illustrates the potential of the original active absorption principle.
It is not a new C214 test, nor a statement that every passive design will produce the same result. The C20 is discontinued; its contribution to the development of AVAA remains essential.
PUT THE TECHNOLOGY TO WORK
FIND THE PRESSURE.
LET AVAA DO THE REST.
Rigid room corners are useful starting points because they often combine pressure maxima for several modes. The best locations depend on your room’s geometry, openings, construction and existing treatment.
- Choose a suitable location. Start near high-pressure areas and follow the product manual’s clearance and placement guidance.
- Connect power and switch on. No measurement microphone or room calibration routine is required.
- Listen, compare and refine. Compare the same passage with AVAA on and off. Measurements can help optimise placement and assess decay.
- Scale to the room. Additional units can increase absorption and give more placement options. Ask your dealer for advice on quantity and sensitivity.
ONE PRINCIPLE. MANY ROOMS.
WHERE CLEARER
BASS MATTERS.
The need is the same: control persistent low-frequency energy so the room interferes less with what you want to hear.
PROFESSIONAL AUDIO
MAKE DECISIONS
WITH CONFIDENCE.
Recording, mixing and mastering studios, home studios, broadcast vehicles and post-production suites. Better-controlled decay can make low-end balance easier to judge and reduce the masking that complicates critical listening.
MUSIC & ENTERTAINMENT
HEAR MORE
OF THE PERFORMANCE.
Hi-fi listening rooms and home cinema. Tighter bass can improve perceived clarity and imaging, making long listening sessions more comfortable. Bars and small venues require model selection appropriate to their sound levels.
SPECIALIST ENVIRONMENTS
ADDRESS
LOW-FREQUENCY RESONANCE.
Machine rooms, boiler rooms and other industrial spaces can also have modal problems. Such applications need an assessment of frequencies, sound levels and environmental suitability before choosing an AVAA solution.
INVENTED HERE. DEVELOPED HERE.
THE ORIGINAL.
STILL ONLY
PSI AUDIO.
We were the first to bring AVAA to the world. We invented and patented this technology, and PSI Audio remains its only manufacturer.
It began with a simple frustration: the same precision monitor could sound very different from one studio to the next. We wanted listeners to hear the loudspeaker’s accuracy without persistent room resonances getting in the way.
What started as a way to demonstrate our own monitors became a technology for studios, music lovers and acoustic professionals.
- 1995
Academic collaboration
The first partnerships with academic researchers lay the groundwork.
- Late 1990s
The listening-room problem
Tests of our studio monitors reveal how strongly rooms can alter the listening result. The idea for AVAA takes shape.
- 2012
Research becomes a project
A three-year development programme begins with two Swiss academic partners.
- 2015
A stable prototype
Electronics and electroacoustic engineering come together in a working, stable AVAA prototype.
- 2016
AVAA C20
The first commercial AVAA brings the original analogue design into studios and listening rooms. This is where the product story begins.
- 2020
The digital development
Work begins on a digital implementation of the AVAA principle.
- 2023
AVAA C214
The AVAA C214 introduces digital control in a compact cylindrical format.
- Today
The invention continues
The AVAA C214 is our compact reference for studios and hi-fi. The AVAA C225 extends the family to high-SPL applications. AVAA C20 production has ended.
EXPERIENCE THE INVENTION TODAY
AVAA C214.
THE TECHNOLOGY,
IN YOUR ROOM.
Compact active bass absorption.
For the studio. For the music room.
A digital implementation of our patented AVAA principle, with a slim aluminium enclosure, black or white finishes and optional mounting feet. The app lets you control individual units or groups and adjust sensitivity.
For high-SPL home cinema and other demanding sound-level applications, explore the AVAA C225, operating from 12–130 Hz. Compare the current AVAA models ↗
GO A LITTLE DEEPER
BASS TRAPS.
ROOM MODES.
YOUR QUESTIONS.
What is AVAA technology?
AVAA stands for Active Velocity Acoustic Absorber. Invented and patented by PSI Audio, it uses microphones, actuators and an active control system to absorb low-frequency sound energy in the room. PSI Audio is the original developer and the only manufacturer of AVAA technology.
What are room modes?
Room modes are resonances associated with the dimensions and boundaries of an enclosed space. At a modal frequency, bass can be strong in one part of the room and weak in another. When poorly damped, that resonance also takes longer to decay, making bass notes overlap.
Can an active bass trap replace passive bass traps?
An AVAA can be an alternative to substantial passive treatment for low-frequency resonances within its operating range. The C214 covers 15–160 Hz. Keep suitable passive treatment for mid- and high-frequency reflections; the best combination depends on the room and its existing treatment.
What is the difference between AVAA and acoustic foam?
Acoustic foam is a porous absorber. Its low-frequency performance depends on thickness, material properties and placement, and thin foam mainly treats higher frequencies. AVAA actively absorbs bass energy in its specified range without needing a large depth of porous material.
Is AVAA a Helmholtz resonator or a membrane bass trap?
No. Helmholtz and membrane absorbers are passive resonant systems whose performance depends on their tuning and damping. AVAA uses active control to absorb across a frequency band, without requiring the user to tune it to individual room modes.
Does AVAA use phase cancellation or room EQ?
AVAA is an acoustic absorber, not a speaker equaliser or a listening-position noise-cancelling system. Its internal control loop changes the acoustic conditions at the absorber. It requires no connection to the music signal and works independently of your speakers and electronics.
Does AVAA C214 need calibration, an app or a measurement microphone?
No room calibration is required. Position the unit in a suitable high-pressure location and switch it on. The app provides optional control and sensitivity adjustment. Acoustic measurements are useful for checking placement and the result, but are not needed to calibrate the absorber.
Where should I place an AVAA, and how many do I need?
Start with suitable high-pressure locations, often rigid corners. Follow the manual’s placement and sensitivity guidance. The number of units depends on the room, listening level and desired improvement. One unit can act on multiple modes within its operating range; it is not one absorber per mode.
Will AVAA improve bass throughout the room?
Absorbing modal energy can improve decay beyond a single listening position. The result will still vary with frequency and position: AVAA does not guarantee an identical or perfectly flat response at every seat. Assess several positions when planning a studio or home cinema.
Does AVAA soundproof a room?
No. Bass trapping controls sound inside a room. Sound isolation between rooms is a different task that depends on the building’s construction and transmission paths. AVAA is not a substitute for a soundproofing design.
Is AVAA C20 still available?
Production of the AVAA C20 has ended. It was the first commercial AVAA and remains an important part of the technology’s history. Explore the C214 for current compact active bass absorption, or visit the Downloads page for legacy documentation.
PATENTED AVAA TECHNOLOGY · PSI AUDIO
LESS ROOM
IN THE WAY.
Hear what active bass absorption can bring to your system.
Explore further: Room modes explained · Manuals & technical documents · AVAA C20 legacy information