PSI AVAA C20 Review

This could be one of the more vague reviews you read.  Not because of a lack of experience with this product but because it makes no sound and the technology is so new.  The best way I feel to give a review of this product is to honestly explain the issues I was experiencing, and how this helped alleviate them.

Room Acoustics

Some time ago, I started looking at ways of fixing acoustic problems in my mix room.  The area I am working in has dimensions of 22’x23’x7.3’.   As any trained acoustician will know, this is not optimal for low-end response.  Every room has its own modes that naturally boost or cut audio as a result of resonating a given wavelength.  The name of the game is to minimize that by having non-parallel surfaces and combining acoustic absorption and diffusion into the design of a room.  After some calculations and an analysis of my room by taking several measurements inside Room EQ Wizard (REW), I found out that my room creates strong axial modes around 70hz-130hz.  This explains to a large extent why I would always have to double-check low end on mixes with other speakers around the house.  Anything from headphones to cheap stereos and to listening in a car, I’ve tried it.  Since all audio playback systems behave differently in a given acoustic environment, the ultimate goal for engineers is to have their mix sound the same across all the different devices people will listen on.

But that requires the absolute best monitoring environment to begin with, meaning: accurate speakers and removing mix room acoustics from influencing your choices.  The only problem is, the lower in frequency you go, the harder it is to tame those acoustics because the physical wavelength is so long.  For example a 60hz sine wave has a length of almost 19ft!  It is beyond the reach of all but the most lavish studios, both physically and financially, to treat this low of frequency.  You would literally have to have acoustic treatment 19ft thick to trap that frequency.

Treatment Methods

So how do I compensate for it?  I treat my room in three ways.  

  • Strategically placed Rockwool panels were installed to treat first reflections and flutter echo.
  • PSI Audio comes to the rescue with a scientific box of magic called the C20 Acoustic Velocity Active Absorber (AVAA).
  •  And lastly, I use a Trinnov ST2 Pro to deal with phase, impulse response, speaker placement, and frequency management in my room.  (I will focus on a review of the Trinnov at a later time)


I got the units on a Saturday (thank you FedEx) and immediately went to work opening them up and implementing them in my studio.  As you can see, the units were double boxed and arrived with in perfect condition.  In my book, careful packaging is a mark of someone who cares about customers. 

Warren Dent over at Zen Pro Audio is so easy to deal with and responds quickly to his emails.  I highly recommend getting your units from him and you won’t be disappointed. In fact, he even sent a great tasting roast of fresh coffee beans with my order.  (Way better than that other company that sends candy)

It’s a TRAP!

I must say that I am not impressed; I am converted. PSI has done their homework with this box.  

I won’t go into too much detail about how it works, but the basic principle behind it is that it keeps the velocity of air around it at a neutral state by measuring and actively absorbing the low end frequencies that build up around the box.  The AVAA is not emitting anything like an opposite sine wave back out into the room to cancel the offending frequencies, but rather absorbing it and creating an anti-wall.  Envision a big hole in your wall that lets low end frequencies escape, and you have a pretty good idea of what this box does.



After lots of positioning, measuring and re-positioning the boxes around my room, I found that right behind my main speakers (and to the center) was the most effective at smoothing out the low end response.  Interestingly enough, it also fixed a drastic phase issue for me at 73hz hertz.  Check out the before and after graphs here.  

Waterfall graphs from REW are below to show the decay of frequencies over time.  These measurements were taken without the use of the Trinnov system that I spoke of earlier.  I will definitely get a review of the Trinnov up for you all and show you the results of that soon.  

I was optimistic that the decay time in my room would have been affected a bit more.  But I realized that for a room my size, I would need at least 3 possibly 4 of these boxes to have a greater impact.  Those of you with smaller, more rectangular rooms would find even a greater benefit than I did with just 2 units.


  • You need to spend time positioning them.  Experiment and figure out where the best place for the units are in your room or you will be disappointed in the results.  
  • Yes, they are expensive.
  • Yes, they do what they claim to.
  • Yes, I would buy more.** 
    • **(a year or two from now when I can get a used one)