Standing waves & system dynamics …

Standing waves …

Standing waves, room modes or room resonances – what ever you want to call them, cause utter devastation to our otherwise beautifully reproduced music.

The awful fact is, that as soon as you make a room a “room” :  Thats with walls, ceiling and floor boundaries, it (the room) naturally following the laws of physics has inherent resonant frequencies, based on it’s shape and size.
At these frequencies, sound waves are “bounced” between the relatively solid physical boundaries of the room.  They continue to bounce back and forth for quite an alarming measure of time, before the various losses involved “spend” all the energy and they finally die away.

Musically …

In musical listening terms, these frequencies could easily remain audible for two or three seconds. All the other frequencies in the room and the music, are likely to die away in less than half a second.
It shouldn’t be difficult to imagine that a guitar note, dying away in less than half a second, followed by a bass guitar note taking two seconds to decay is:
(A) Not going to sound right, or “it’s best”
(B) Not representing the music “as the artist intended”

Graph …

This graph shows the effect on bass drum beats, and importantly the reduction in Dynamic range.
The blue traces represent the room resonances, decaying over, in musical terms, a very long time.  So much so, that the room resonance effect from the first bass drum beat is still audible at the second bass drum beat.
As recorded, the “gap” between the bass drum beats should be “silent”.  With room resonance in control, the gap is anything but silent: in fact full of a slowly decaying version of the previous beat.

Bass drum dynamics graph.jpg
The reduction in dynamic range, or “loudest bit” to “quietest bit” is reduced by up to 20dB.
The subjective effects on the lister are:
(1) Lack of “punch” and “weight” particularly in bass rich percussive events
(2) Lack of musical involvement
(3) Lack of performance emotionality

In short, to maximise listening pleasure, musical involvement & emotionality, and to do justice to audio equipment at any technical level – you need a ….

“tight, firm bottom” !

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