All your bass belongs to us
When composing, mixing, mastering, or simply listening to music, most of the time is spent in your studio, living room, or a dedicated music room. Unfortunately, many of these spaces suffer from poor acoustics. Finding a room with good symmetry and ideal dimensions, such as those based on the golden ratio, is rare and often a matter of luck.
Most rooms, including typical bedroom studios, share similar dimensions and are susceptible to resonant modes. Particularly below the Schroeder frequency and in the bass range, long wavelengths can distort the sonic image, complicating the mixing and mastering process. This challenge often results in mixes that don’t translate well outside of the studio environment.
Achieving accurate bass reproduction is notoriously difficult and usually requires extensive bass trapping and meticulous speaker placement. However, bass trapping often consumes valuable room space. PSI Audio found out a way to solve these issues in a convenient way. Let’s find out how:
Some History
Some time after the AVAA C20 was launched in 2016, we had the chance to experience its effect at Musikmesse in mid-2018.
After chatting with Roger Roschnik and Fabrice Del-Prete at their booth, we were invited to a hotel room where they had almost the complete product line on demo. This allowed us to listen more critically, even without the AVAAs, than at their booth, which was of course noisy because of the other exhibitors.
We found ourselves in a nice room at the Maritim Hotel, enjoying the luxury of listening to several monitors from the PSI Audio studio line. After Roger introduced us to the AVAA C20, he gave us a longer overview about how the system works, we had the pleasure of listening to some good music on the PSI Audio A17 monitors.
Although it already sounded very good, Fabrice turned on two AVAA C20s without us knowing, and the difference was like night and day. The bass instantly cleared of any long resonant reverb tails or so called ringing. It became really tight and much more balanced. There was no more overhang in the bass for certain notes that matched the room’s resonant frequencies at the listening position.
Trap Time
Fast forward six years, and we connected with PSI Audio to demo their products in our studio for a few weeks. In our studio, we’ve put in significant effort to get the acoustics right and achieve a more even response in terms of frequency and reverb time across the frequency spectrum (RT60). We’ve done this by building our own acoustic panels, installing DIY bass traps filled with Rockwool 221, adding a custom ceiling with Rockwool and slats on top, and using off-the-shelf products from Primacoustic, like their full trap with an integrated membrane.
When visitors come to our studio, some ask why we went to such lengths. As a composer, sound designer, and engineer, doubts often arise during mixing and mastering. A good listening environment that you know well and can trust will help you achieve balanced, great-sounding results more quickly.
In other words, the more you do to get your room sounding right – instead of only investing in great monitors – the more confident you become, and the more the room serves you instead of working against you. “Against you?” Yes, because every room has room modes or standing waves that influence the sound of the monitors. Typically, you address low-end issues with mineral wool, membranes, or Helmholtz resonators. For mids and highs, carpets, curtains, and bookshelves are affordable and effective tools to get reverb times under 250 to 350 ms, as anything above can be problematic. This also helps achieve a more even and balanced sound.
As sound bounces through your room and interacts with the direct signal at the listening position, it can result in larger and louder sound waves or nulls due to relative phases. This varies with frequency and listening position and differs throughout the room. For higher mids and highs, this usually results in slight color changes, as the wavelengths aren’t large and often create a chaotic pattern that isn’t much of an issue and easy to treat.
However, for low-mids and lows, this can be problematic due to larger wavelengths. For example, at our listening position, we have had the typical major nulls between 70 and 100Hz, which is why we created bass traps to mitigate this issue. Typically, addressing low-end issues requires large bass traps, which is exactly what the AVAAs aim to solve without taking up much space. That’s why we decided to give the AVAAs a try.
Choices: C20, or C214?
Since the introduction of the AVAA C20, PSI Audio has released a more compact successor, the C214. While the C20 is targeted at studio professionals, the C214 is aimed more at high-fidelity audio listeners.
Given that our studio is a small attic space, we decided to review the newest addition to the AVAA line. One great feature of the new units is that they come with an app for control and can be boosted for increased efficiency. In our studio, we didn’t feel the need to use this feature, but it was very nice to try out in our living room.
What’s New
So, what’s different and new when you compare the C214 with the C20 in terms of specifications? Well, the AVAA C214:
- Uses digital processing instead of analog, featuring ultra-low latency (less than 0.2 ms) processing via two independent DSPs.
- Is significantly smaller and easier to handle and position in your room.
- Is more effective, with a broader range from 15 Hz to 160 Hz instead of 150 Hz.
- Can be tweaked via an app, providing easy access to the parameters from your listening position.
- Can also be tweaked to change its efficiency at the back of the unit.
- Has an optional mounting bracket available.
- Looks more attractive, in our view.
Setting Up
PSI Audio recommends placing the AVAAs in the front corners when using two units. We tried this first, powered them on and listened to a few good records. The difference was like adding a cherry on top. It felt just right.
To identify pressure zones (the areas where you hear the bass the most), we performed a room sweep with a sine wave at about 85-90 dB between 20 and 300 Hz and also playing pink noise and measured it using and walking around in our studio with an SPL meter. Since our room is not a typical shoebox shape, this resulted in one pressure zone at the back in the middle and one up front at ¼ of the room’s width. However, positioning the C214s at the front left and right corners created the most coherent sound at the listening position. Most of the resonant ringing at around 27, 40, 60, 80 and 138 Hz almost disappeared, making the room sound larger and calmer than it actually is.
Another approach is to calculate the room modes by hand and then measure where the biggest issues are by playing test tones at several of those calculated frequencies. Then, place the AVAAs where the highest pressure is measured.
The lowest frequency axial room mode is caused by the longest room dimension and can be easily calculated. Divide the speed of sound (343 m/s) by twice the length (L) in meters. To find the next two lowest modes, use the same formula with the width and then the height of the room. You can add the corresponding frequencies as multiples (overtones) to identify other problem areas.
As mentioned before, our room isn’t a typical shoebox, so we did a lot of measuring and applied common sense after reading extensively on the subject. Also, as mentioned in the manual, in small rooms the placement isn’t really that strict. That’s something we encountered as well. That makes us wonder how these AVAAs work.
How does it work?
AVAA stands for Active Velocity Acoustic Absorber. According to PSI Audio, it’s simply a matter of placing it in areas where there is significant pressure, powering it on, and forgetting about it. We believe they’re absolutely right.
Effectively, it acts like a hole in the wall or a large passive bass trap. Simply put, this means that signals between 15 and 160 Hz enter but aren’t reflected back out. It achieves this by measuring the pressure of incoming signals and working like a sort of inverted subwoofer.
From the manual:
“The graph hereunder shows the typical equivalent absorption area of an active AVAA over the frequency bandwidth it is designed to absorb. Note that an AVAA C214 is approximately 0.13 m2 so an equivalent sound absorbing area of 4 m2 is 30 times the surface of the AVAA.”
Results
When mixing and playing music, our sound system, consisting of KSD A200mk2, was already quite neutral. However, activating the C214s resulted in an even calmer and tighter bass and lower mids, exactly what we were looking for. By listening to some tracks of Aphex Twin (…I Care Because You Do – 1995), Boards of Canada (Geogaddi – 2002), Deadmau5 (Polar Soundtrack – 2019), Justin Bieber (Purpose – 2015), two albums of Stewart Walker (Ivory Tower Broadcast (2014) and Flatwound Modal (2018)), Tinashe (BB/ANG3L 2023) and to Vincent de Moor (Orion City on CD/YouTube) we got the impression that for all these albums the bass got more tight, the music resonated more with us if that makes sense. We can imagine that adding another one or even another set would further improve the sound. It’s as if a veil has been lifted from both the speakers and the room itself, resulting in better and more precise bass, and a more coherent overall soundstage and image. Let’s have a look at some measurements.
Measuring
The following measurements with 1/12th octave smoothing are with the AVAAs turned off in purple, on at the pressure places we’ve found by walking around in the studio in orange and at the two front corners in red:
And here are the waterfalls of the same measurements:
As you can see, the frequency spectrum improves by approximately 2.5 to 3 dB between 70 and 100 Hz when using the AVAAs at the corners in front. The reverb time gets even better when using the two AVAAs at different pressure zones. Three or four units would likely be ideal.
Conclusion
So is the AVAA C214 the ultimate and compact bass trap? Well the AVAA C214 is a digital bass trap – or pressure based absorber according to PSI Audio – that is truly worth considering if you are serious about your audio system. It is not cheap, but on the other hand, if you ever move, you can simply take the AVAAs with you, plug them into a wall outlet, and power them on, instead of needing to create loads of – probably custom – big bass traps again.
Whether you are an audio professional or an audiophile, we highly recommend it.
Thanks to Fabrice from PSI Audio and Ulmt from Helios Pro Audio Solutions Netherlands for lending us a set of C214s.
Pros and Cons
and you’re good to go!
Pros
- Highly effective solution
- Compact solution
- Convenient and easy setup
- Remote control via app
- Easy to move when relocating
Cons
- Significant price increase since the introduction of C20
- App functionality is limited to WiFi 2.4GHz; Bluetooth is not supported.
After a chat with PSI Audio they told us that a complete new app with added Bluetooth support is on its way.
More Information
For more information about the AVAA C214, please visit the product page on the PSI Audio website: https://www.psiaudio.swiss/avaa-c214-active-bass-trap/
In the Benelux, the PSI Audio C214 AVAA is distributed by Helios Pro Audio Solutions and their subsequent dealers. Are you residing outside the Benelux, please have a look here: Where to buy – PSI Audio
