Nondirectional & Inaudible Bass: What Frequencies?


Hello. A few quick technical questions: I am curious as to what frequency bass goes "nondirectional." I saw a reference in print to it being around 100-125Hz, but that doesn't seem right to me. Does the room have an effect or is it purely psychoacoustic?

Also, wondering at what frequency bass becomes inaudible. Thanks much!
socrates

Showing 1 response by sdcampbell

Well, there are two perspectives on the issue of "directionality" with bass frequencies. Some folks will say that bass frequencies become essentially non-directional below about 40 Hz, while others will argue that we are much aware of low-frequency directionality than we realize.

I was of the school that thought bass was non-directional in the bottom octave (20-40 Hz), until I bought a really good subwoofer (a Vandersteen 2Wq). I had the sub in one corner of my listening room, and when I played recordings of pipe organ music, I sure could tell where the lowest frequency notes were coming from. This led me to buy a second 2Wq sub, and it made a vast difference in the quality of bass in my room.

Based on this experience, I now advise people who want good bass reproduction for MUSIC to buy a stereo pair of subwoofers. I believe strongly that a pair of subs is necessary to achieve realistic musical presentation.

Reproducing low-frequency effects (LFE) for home theater is a somewhat different matter. Low frequenices on DVD are usually sound effects such as explosions, deep rumbles, etc., and they are normally of short duration. The short duration of the sound gives us less time to become aware of directionality, unlike music where the low tones may be sustained for 5-10 seconds or more.

As for the audibility level of low frequencies, that will depend on:
1. your listening room;
2. the roll-off curve of your speakers and subwoofer(s);
3. the amount of amplifier power available for your speakers;
4. the nature of the recording (there is very little audio signal below 25 Hz in home theater).

Most home listening environments, if they have not been acoustically treated, show pronounced roll-off below 30 Hz, and "bad rooms" may even cut off the bass frequencies around 35 Hz.