Acoustic foam made room harsher!
I had a client who installed a moderate acoustic treatment (8 x SA600-75, 4 x BT600-150) in a home theatre to improve his listening experience. The results were not what I expected. Normally the results are “improved imaging and clarity” or “tighter bottom end”. The client reported back that the system became very harsh in the 2-3 Khz range. I suggested a few changes to the layout but to no avail. I then suggested loading the room up with as much absorptive material as possible – pillows, doonas, blankets, old clothes, towels and spread them everywhere. The room became very dead, and the system remained harsh. More absorption certainly wasn’t going to improve the situation. What is going on here? This is the weird world of psychoacoustics. The panels can’t possibly be increasing the high frequency reverberation times, but they are changing the balance of the room by reducing low frequency reverberation times (generally still longer than mid-high frequencies). This can make mids and highs sound sound more present (and harsh in some cases). A great experiment is to place your speakers in an open outdoor area. This is like placing them in an anechoic chamber. They will generally sound lacking in low frequency warmth, compared to the indoor experience. And sometimes harsh. This is why we have a money back guarantee on our products, no questions asked. They don’t always sound better to the listener.
Jan 02, 2010
Just wanted to chime in to say what an excellent and candid blog post. Really appreciate you posting a scenario where the treatment did not improve things. While this scenario might be unusual, your post reminds us that when we’re dealing with “the weird world of psychoacoustics” things aren’t always as predictable as the room mode calculator suggests.
It also shows that you’re willing to balance your information rather than just state amazing case-scenrios of miraculous acoustic improvement when using your products. Well done & thankyou.
Jan 04, 2010
Thanks Craig for the comment. As you say, there are far more aspects to acoustics than a room mode calculator. For many people, a bit of a lumpy bottom end and a woolly cushion of low frequencies is not just acceptable, it’s their preferred listening experience. Not everyone is after clinical accuracy. Psycho acoustics is an interesting area. For example, it’s amazing how quickly the brain adjusts when you flick in the loudness on a system. After a short while the accentuated low frequencies become normal. Defeat the loudness, and what was previously a balanced sound has become thin and lacking in bottom end.
Many mastering engineers continually cross reference to maintain their “psychoacoustic calibration”