PSI Audio AVAA C20 electronic bass trap Associated Equipment

Sidebar 2: Associated Equipment

Digital Sources: DAC: 8-channel Cranesong Avocet monitor controller for 5.1-channel surround plus stereo bass.
Power Amplifiers: Lipinski Sound Mono Block L-301V.
Loudspeakers: Revel Ultima Gem2.
Subwoofers: JL Audio Fathom f112 (stereo pair), each powered by dedicated 20 amp line, permitting 1500Wpc bass peaks with no power sag.
Cables: Interconnect (analog): Mogami low-capacitance OFC (balanced AES/EBU). loudspeaker: Mogami eight-conductor OFC, doubled 14 AWG, equivalent to 8 gauge.
Accessories: Surge-X series protectors with Surge-X RFI/EMI filters. RealTraps MondoTraps, Sonex One acoustic panels, AudioVero Acourate & AcourateConvolver software, Room EQ Wizard analysis software, dedicated 230V/100 amp power service, central-point grounding, 115V/20 amp hospital-grade isolated ground outlets.
Listening Room: 18'–20' 7" (5.5–6.3m) L by 14' (4.3m) W by 12' (3.6m) H in front, rising to 23' (7m) in rear. Volume: 4536ft3 (128m3).—Bob Katz

PSI Audio
US distributor/dealer
ZenPro Audio, LLC
119 Towhee Circle, Orangeburg, SC 29118
(803) 937-6012

dalethorn's picture

That's an epic review. A lot of audiophiles who don't record or mix will want to try this, but I think they're going to need help. And I wonder what that help would cost. Great music tips too BTW.

Axiom05's picture

Interesting write-up on an interesting product. Please note that my following comments are based on my personal experience with bass traps and not from any professional or expert knowledge. Based on your frequency plots, one might conclude that, while audible, the effects from spending $6000 on active traps is quite minor and a poor value. As you have shown for both the active and passive bass traps, their effect in the frequency domain can seem insignificant (on the order of 1 - 2 dB or less). My experience with passive traps has been similar: I have not seen huge improvements in the frequency response (some frequencies get better and some get worse). However, I have found the true value of traps to be how they effect the time domain response. For me, reducing the "ringing" of the bass notes provides a significant improvement in the sound quality. Our ears seem to be less forgiving of time domain issues than of peaks in the frequency response. In other words, a peak in the bass region is more tolerable if the note isn't accompanied by a long reverberation time. It would have been interesting to see before and after waterfall plots of the product under review, particularly how effective they are at 29Hz. This is one of the potential strong points of this type of product as passive traps will have little effect at these lowest frequencies. However, it does seem apparent that any practical improvements using active traps will require more than one unit. Ouch!

Tim Link's picture

I too found this article interesting, especially the frequency response curves with and without the traps. We make and sell passive bass traps, and we get before and after measurements from our customers whenever we can. We too have found that often significant sonic improvements from the traps looks like very little change when looking at frequency response. To get a better idea of what's going on, we use a recording called MATT - Musical Articulation Test Tones. This will clearly show the difference when played in a room and recorded at the listening position. We run the recording through an analyzer that shows how fast the room is tracking the volume level at different frequencies.
What's also nice is that you can just listen to it and hear where the room is slurring the bass dynamics. This gives you a clear idea of whether or not the room could benefit from more bass damping.

drblank's picture

I don't know why he's comparing against the Mondo Traps. Those aren't that great of a product if you are trying to go after low frequencies under 100hz.

I also don't think that using subs is going to give the best attack and decay rates. I've talked to someone that has actually tested a variety of subs placed around the room at different heights and the attack and decay rates aren't as good as the products they compared them against. They compared them against diaphragmatic absorption cabinets. There are much better absorption products on the market other than the Real Traps or active subs for low frequency absorption.

I would be looking at companies that make Diaphramatic absorption products. They can be designed to really be effective towards the low frequencies under 100hz, but you need something that will effectively go down to the 30 to 50hz range as that's typically where you find most problems. Think in terms of the fundamental frequency of bass notes. A Piano, for example, goes down to about 27.5hz for the lowest note on a typical 88 note grand piano. The bottom two octaves on a piano are 110hz and below. The Mondo traps is just cheap building insulation wrapped in fabric, put in a metal frame and either hung or positioned around the room. They aren't low frequency absorption products. For that, you'll need diaphragmatic, membrane or Helmholtz resonators. Diaphragmatic being the most effective if designed properly.

Kal Rubinson's picture

Since the link for the BagEnd trap is dead, here's a link to my Stereophile review.