Hello cheeg,
I’m just going to complete my last post as I previously stated:
Lastly, I wanted to provide you with some easily verifiable facts that should allow you to more easily recognize the bad information you’ve been given already on this thread as well as any that may be given to you in the future. But I have a meeting I need to attend right now, so I’ll give this info to you later on another post as soon as I can. Continuing:
1. Humans cannot localize sounds (determine exactly where they are originating from) with frequencies below about 80 Hz, which includes all the audible deep bass tones down to the audible limit of 20 Hz. We are increasingly adept at localizing sounds as their frequencies increase from above about 80 Hz to the generally accepted audible upper limit of high pitched sounds of 20,000 Hz.
2. Recording engineers, of course, have known about this fact since at least about 1950 and is the main reason they’ve been summing all bass tones, with frequencies at or below about 100 Hz, to mono ever since.
Some individuals will inevitably deny this is true. I usually just ask them to name a single commercially available recording that contains stereo bass below 100 Hz.. I’ve never been able to name a single example and neither has anyone else.
3. It follows logically from the above 2 facts that the reproduction of true stereo deep bass on a home audio system is not possible, as long as commercially available LPs and CDs are the source material played. Therefore, it makes little sense to position a left and right sub near each of your left and right main speakers. It’s best just to operate all subs in mono and position them where the bass sounds the best using the crawl method.
4. Bass sound waves behave very differently in a given room than midrange and treble sound waves behave. This is mainly due to the facts that bass sound waves are omnidirectional and very long while midrange and treble sound waves are highly directional and much shorter. The length of a frsound sound wave is directly and inversely related to its frequency. The lower the frequency, the longer the corresponding sound wave and the higher the frequency, the shorter the corresponding sound wave. It’s a continuum with the lowest audible frequency of 20 Hz having a sound wave length of about 56 feet and the highest audible frequency of 20,000 Hz having a sound wave length of a fraction of an inch.
So, the long omnidirectional bass sound waves are launched into the room from the sub in many directions and, if the frequency is deep and long enough, each sound wave could exceed any single dimension of the room. Each of these bass sound waves will continue to move out into the room until it meets a room boundary (floor, ceiling or wall), reflect or bounce of this surface and continue moving in the reflected direction until it meets another room boundary and is reflected once again. This process continues until the sound wave either collides with another reflected sound wave (causing a standing wave) or it runs out of energy.
5. Each time any of these moving and reflecting bass sound waves collide with another sound wave, what’s called as bass standing wave results at the specific room location the collision occurs and we perceive the bass at these exact spots as a bass peak, dip or null.
If a 4-sub DBA system is utilized, our brains sum and average the bass by frequency and no bass peaks, dips or nulls are perceived in the room. If only a single sub or pair of subs are utilized, the crawl method can be utilized to ensure the designated listening seat is not located near a bass standing wave.
6. Interestingly, it’s been proven that a complete,full cycle and full length bass sound wave must exist and be detected by our ears prior to our brains can process it and create the perception of a bass sound at the appropriate depth of pitch in the room
If the bass is deep enough that the sound wave exceeds any of the room’s dimensions, this means the sound wave must reflect off at least one room boundary before we perceive a bass sound or tone at all.
7. Our ears and brains are much less sensitive to the arrival time of bass frequency sound waves than midrange and treble frequency sound waves. I believe heaudio123 correctly mentioned this earlier on a post. I’m not absolutely certain, but I believe as long as bas sound waves reach our ears within about one fifth of a second of each other, our brains process these sound waves as related and parts of a single sound or tone. This means the sound waves from all 4 subs in a swarm definitely do not need to arrive at one’s ears at the same time. There’s no strict timing requirements or resultant “smearing” involved with multi-sub bass reproduction.
8. Of course, the much shorter and highly directional midrange and treble sound waves also reflect or bounce off room boundaries (floor,ceiling, walls) until they collide with one another or run out of energy, just as bass sound waves do. It’s much more important that the main speakers are precisely positioned in the room, and in relation to one’s ears at the designated listening seat, so that the direct midrange and treble sound waves from the speakers arrive at the listener’s ears first, before any reflected sound waves do to ensure optimum performance, imaging and quality. However, it’s much easier to useroom treatments to absorb or diffuse first reflection points of midrange and treble sound than it is to do the same on first reflection points of bass sound waves. There’s also no performance, imaging or quality concerns dependent on the direct bass sound waves from any specific, or combination of subs, arriving at the listener’ ears first. Any midrange and treble sound wave collisions resulting in midrange and treble peaks, dips and nulls at specific locations in the room, are typically not a big issue since we tend to perceive these as an ‘airy’ quality to the overall sound in the room.
Hope these facts helped your understanding,
Tim
