New Gear Review: AVAA C20 Active Bass Trap by PSI Audio
“AVAA is designed to absorb the standing waves in a room between 15 Hz and 150 Hz.”
Mixing is hard. There, I said it. And there are any number of factors that make it harder.
Every piece of software/hardware you use is altering the signal, and not always in the ways we intend. Even if you have top quality gear, an area that’s too often underserved is acoustics.
Sound always exists within a space. From the Grand Canyon to the smallest closet, there is no separating sound from the listening environment. If your room is coloring the sound, then you’re making critical mix decisions based on skewed information.
This can lead to many frustrating hours back and forth between the studio, the car, and/or any other secondary pair of speakers. In our field, experimenting is what keeps us alive and fresh, but second-guessing is what kills us.
Let’s take a look at a standard room and the problems you may encounter. Imagine your room with just your technical systems inside of it (i.e., your DAW, console, outboard gear, speakers, etc.). Right out of the gate, all of these tools will lie to you, to some extent.
Truthfully though, if you have halfway decent gear, this is the least of your problems. Most issues that arise will be regarding frequency response. The good news is that a lot of that concern can be conquered at no cost by simply referencing and ruthlessly comparing your mixes. Another potential solution is strapping an equalizer across your monitors–a technique used by countless studios over the years.
Once the sound leaves your speakers, it begins to interact with the room, which likely has frequency imbalances of its own. A well-designed room can be an expensive proposition. While it’s a wonderful thing to strive for, it’s not always realistic for most of us on a day-to-day basis.
Acoustic treatment can and should be employed as a first line of defense here. Bass traps, absorption panels, and diffusion can go a long way towards easing the mixing experience. I would even argue that if you have budgeted X amount for your speakers, you may be better off splitting that money equally between speakers and acoustic treatment.
There are numerous companies that make inexpensive prefabricated panels. If you want a specific look, or even a more accurate fix, you can contact an acoustician in your area and have custom panels made and installed.
EQ can be your friend here again, and there are some excellent DSP-based room correction software solutions. These are useful for helping even out the room modes and are relatively affordable. Many such corrections are beneficial, but the frequency domain is honestly only half of the problem.
Time-domain issues occur as the signals start bouncing around the boundaries and surfaces in the room. Software/EQ and referencing won’t help you here as the problem is occurring after those fixes.
The direct signal hitting your ears is being obscured and colored by the reflections that are occurring in the room and arriving later in time. The smearing of these signals can make even basic mix decisions challenging, so it’s acoustic treatment to the rescue again! Those same panels mentioned above, when placed properly, can tame the reflections. This helps clear the space for you to hear into your mix and know what’s going on.
So there you go. Problems solved. You’re welcome. Except for one small detail–most of us work in smaller-to-mid-sized rooms. The frequency-based problems you will run across are generally based on the size of the rooms and the distance between boundaries. Apart from something in the room vibrating sympathetically, these are even mathematically predictable. If your room is X number of feet long, there are specific frequencies that are boosted or attenuated based on that length.
The specific dimension has a relationship with a certain frequency and its harmonics. In a larger room, those problematic areas get lower and lower in the audible range, and at a certain point it’s low enough to no longer be a concern. We benefit in other ways from longer distances between boundaries as well. The farther a sound has to travel before a point of reflection, the more the energy is dissipated and the farther out that reflection gets out in time from the direct sound when it works its way back around to our ears.
In a smaller room, the problems get much worse. Additionally, there are real, practical limits to the amount of acoustic treatment that’s viable in a room. This is true in both the financial and spatial sense. For most of us working in bedrooms, dens, and offices, the amount of acoustic treatment needed to address problems in the very low frequency range would be impossible. Or, at least, miserable to work in.
One can make custom, tuned bass traps which focus on specific areas, but they can be very expensive and might not be effective in a different room. This is a real consideration if you are not in a permanent facility. A huge hole in the wall would solve this problem too, but only in the same way a huge hole in your head would fix a headache. This (finally!) brings us to the focus of this review, the PSI AVAA C20 Active Bass Trap. Spoiler alert: I’m not going back to life without it.
Features
The C20 is a bass trap, but not a passive one like the standard acoustic treatment we’ve been discussing so far. It is also referred to as an Active Velocity Acoustic Absorber. While this is active, and does need power, this is not a DSP-based solution and in no way affects your audio chain.
The C20 is designed to focus on low-end issues and deals with problematic modes between 15 Hz and 150 Hz. Above these frequencies, passive solutions work well and are recommended. This device also does not employ active noise-cancelling technology similar to many headphones, which analyze incoming audio, and create a polarity inverted copy of it. The C20 does not make sounds, it absorbs them.
The C20 is small and unobtrusive, especially as it is designed to go in the bottom corner of your room with the flat side panels against the wall. It’s important to ensure that airflow is unobstructed, but you can try other corners in the room if one or more are not a good fit. It’s about 17″ wide and 20″ tall, about the size of a small PA speaker, or a larger near-field monitor.
There are only two controls: a power switch and a rotary control for adjusting sensitivity. There are no panels or menus to scroll through. A green LED on the front indicates power and will flash red if the limiter is engaged. This means it has reached maximum effectiveness and will go no further. If the LED turns continuously red, you are in danger of overheating and must clear out some space for proper ventilation.
In Use
I currently work out of an apartment in Brooklyn, NY. My room has a solid system with great converters and speakers, as well as acoustic treatment (prefabricated panels at the main reflection points above, behind, and to the sides of me as well as 8′ of bass traps in each front corner). I also employ Sonarworks. The combination of good gear, well-placed acoustic treatments, and room correction software has turned an ugly Bed-Stuy box into a very usable space.
[EDIT: I have moved to an apartment in California. The new place is smaller and has more modal issues and the C20 has done even more to help here!]
The C20 could not be easier to set up. Place it in the corner, plug it in, turn it on, and you should be good to go. It is important to note this device is designed for a room of at least 10 square meters (approximately 107 square feet), has acoustic treatment for the mid and upper frequency range, and is not too reverberant.
If reverberation is an issue in your room, you can dial back the sensitivity knob from its default “CAL” position. If you happen to run into stability or positioning issues, the user guide offers a few tips that should solve most problems.
I powered up the device using a longer power strip, so that I could turn the unit on and off from the mix position to A/B with and without it, and pulled up my favorite bass-forward playlist. Immediately, I was struck by a clarity and definition in the low end that was not there before. Any hazy or muddy low end notes are now clear as day. Separation between kick bass was almost laughably easy to identify and dial in. Notes that went up and down the bass scale were solid and well-defined.
The difference to my image was a huge improvement. I invited over an engineer friend whom I trust, and set him up in the mix position to A/B as well. I left for two minutes and came back to the proclamation of “I’m buying this!”.
My mixing time has sped up quite a bit as I am getting a much better picture of what is going on, and I can make fast, confident decisions. Time-domain issues can be problematic as well since some notes will ring on longer, or shorter than their actual length. Understanding how long a bass or kick note lasts makes a solid, punchy low-end so much easier to achieve.
To Be Critical
The C20 is not right for every situation though. I also brought it to a studio with a well-designed control room, and let another trusted colleague try it out in his place. I thought it cleared up the low end.
However, he is so used to the space and knows exactly how to get what he wants quickly and easily. Changing the response of the room for him wasn’t worth it.
If you are in a very small or reverberant room, the effectiveness of the unit can diminish. If you’re in a very large room, you may need more than one. Additionally, the C20 is expensive. The list price is $2,795, which represents a significant investment, on top of a pile of other significant investments needed before this one can even be considered.
Summing it Up
All things considered, I found the PSI AVAA C20 to be a resounding success, and I’m buying this one. I tried this device in three different control rooms at different listening levels.
Overall, I ran into zero problems with it. I never ran into the limiter, or had stability issues even when turned up, but I tend to listen at relatively conservative SPL levels. To me, the difference was greatest in my apartment, the room I’m most familiar with.
I mentioned a hole in the wall earlier for good reason. When discussing acoustic absorption, the measurement unit is a Sabin. 1 Sabin is equal to a 1 square foot hole in a wall. The C20 takes up a little over 2 square feet but absorbs the same as a hole in the wall that’s 43 square feet!
I don’t know how long I’ll be in this place, nor how long I will be in the next (or even the one after that)! The C20 is small and portable, easy to set up, and generally works in any room. Other treatments that would be as effective at low frequencies would either be very large and difficult to transport, or custom designed for this room’s problematic areas and wouldn’t translate to a new space.
If your room is treated and you have decent monitors, but still feel like the low-end could be tighter with clearer definition, you should definitely give the PSI AVAA C20 a try.
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