Advanced Exakt optimisation

Advanced information on Exakt setup

If the room into which the Exakt loudspeaker system is being installed is rather irregular in shape some further optimisation tricks may be applied.
Konfig provides information which will benefit an experienced installer and allow him to more quickly identify which mode filters will need to be adjusted, and in what way. To make use of this information it is useful to understand the limitations of the Konfig room mode calculation resulting from the assumptions made by the algorithms.
Presented in this section are the fundamental assumptions employed by the room mode optimisation algorithms. Advice for simplifying the dimensions when a room is not rectangular to those accepted by Konfig is given. Also recommendations for when to adjust the room mode filter centre frequency and bandwidth are presented.

Basic assumptions used for calculations of room modes

The optimisation algorithm assumes that the room is of essentially rectangular layout. This is often not the case. For Konfig to provide a meaningful room mode optimisation more complicated room shapes must be simplified to approximate rectangular dimensions. How the room is simplified will dictate the adjustment required to the Konfig optimisation.

The room mode algorithm also makes the assumption that the low frequency absorption (or transmission) of the walls, floor and ceiling are all approximately that of brick or cement block-work. When the room construction differs from this, or the walls contain large windows or multiple doors, some adjustment of the room mode gains will be required.

All reflections at room boundaries are considered to be specular. This implies that the reflective characteristics are ideal and are the same at all frequencies. Most real surfaces do not provide specular reflections, instead the magnitude and phase response of any reflected wave is dependent on the incident angle of the acoustic wave. This has significant implications for any non-axial mode (a mode which operates between more than two parallel surfaces).

Adjustment of room modes in Konfig

When a room mode filter is selected from the drop down list the user is provided with the full specification of the parametric equalising filter applied to optimise for the room mode. Any one of the three parameters (centre frequency, gain and bandwidth) may be adjusted to better optimise for a given room mode. The user is permitted to vary the filter gain by ± 100%, the centre frequency by ± 2 Hz and the bandwidth of the filter by ± 10%.

Additional information provided by Konfig

Konfig provides dimensional information about the room modes. The room mode filter titles shown on the drop down list also include a bracketed set of three characters. This describes the axis of the room along which the standing waves of the room mode occur. Modes active along the length axis of the room are shown as [L--], those active across the width or height are shown as [-W-] and [--H] respectively. The mode descriptor will also inform the installer whether a mode is a simple axial mode (operating along a single room dimension) or if the mode is tangential or oblique (operating between four or six room surfaces).

This is very useful information for the experienced installer.  A length mode will be controlled by the characteristics of the front and rear walls.  Say, for example, the front wall is made of glass; the installer will immediately know that any room mode indicated to operate along the length of the room will need to be adjusted.  If the room has a pitched roof, any height mode will need to be adjusted.

Due to the non-ideal reflective characteristics of real surfaces any non-axial mode is likely to be over-optimised by Konfig. The installer will know that any mode described by more than one letter (e.g. [L-H] or [LW-]) is likely to require adjustment, typically an increase in filter gain (less cut).