Lexicon MC-12 manual Room Modes, Understanding Room Equalization, unless, on a

Version 4 EQ User Guide

Figure 1-5. Tips for arranging your listening room.

Understanding Room Equalization

along its length at wavelengths of 36 ft (31Hz), 18 ft (63Hz), 12 ft (94Hz), and so on. Each dimension of length, width and ceiling

			bad
		position
Corner speaker
unless			designed
			here
specifically
to	be	placed

Open		staircase
can
	resonate

Not
	good		unless
speaker
to		was
	be placedintended
bookshelf			on a

height will resonate independently at its own frequencies.

Figure 1-6. Resonance modes along the length of a room.

Amplitude

ROOM MODES

Room modes are resonances that occur when low frequencies rein- force each other as they reflect back and forth between the hard boundaries of the room. The size of the room determines at which particular frequencies it resonates. Room modes can cause the sub- woofer to sound very loud for one note, and fairly quiet for another. A typical room will exhibit many room modes. For rooms with parallel walls, the significant low-frequency modes can be pre- dicted to occur at any frequency for which an even number of quarter wavelengths will fill the space between two opposite walls. For example, a room that is 18 feet long will exhibit a resonance

The resulting sound in the room is the addition (possibly in a com- plex mathematical way) of all the room's modes. Other factors, such as wall stiffness or the position of furniture in the room, can also affect the modes. At higher frequencies, these effects become less predictable and can change as people move around the room. However, the low-frequency modes are predictably consistent. Any problems produced by the low-frequency modes will always be present, but those problems can be mitigated.

1-5