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Exakt filters will have different versions, highlighting any changes. These are primarily the major changes below, coupled with minor improvements.
These versions are different between Exakt loudspeaker modules/Exaktbox version etc, so will vary between speakers and products.
Note: In Konfig there is only a limited selection of filters for newer products. More filters are available in Manage Systems.

Exakt filters are the profiles used in the Exakt Engine:

Original Design release

In the original release of Exakt the drive unit models were rather inflexible. The roll-on and roll-off of each drive unit were modelled separately but could only be deployed to correct for both the magnitude and phase of the natural response, or do nothing. At the lowest frequencies there was very little we could do due to the massive processing requirements, so for most speakers we left the natural roll-on alone. Furthermore, we didn't have a viable model for the roll-on of ported systems or the capability to correct for any fixed internal electronic filtering.

It should be noted that the original release for many supported speakers is not available as a selection using the current version of Konfig. The file format is very different to what is used today and is not readily supported by the Exakt compiler.

Independent drive unit modelling

The first and most sizable change to the Exakt filters happened in October 2015 when we introduced Independent drive unit modelling, often described as 'fourth order filters'. This change introduced the current file format used for all Exakt designs and allowed a huge increase in the processing flexibility of the Exakt engine. Each drive unit could now be modelled with a greater flexibility. Improvements included; ported system models (fourth order), support for fixed electronic filters (e.g. subwoofers), independent modelling of magnitude and phase or phase only for low frequencies, better processing by application of new windowing techniques (allowing extension of linear phase to the lowest frequencies).

Independent highest frequency modelling

For many speakers, there is also this version of filter, which is not available for selection in Konfig. This was essentially the same as the independent highest frequency modelling filter. Changes were made to all design files to ensure they fell in line with the generic measurements stored in the cloud for the drive units employed by the filter. This was put in place to guard against cloud drop out. It shouldn't ever cause a problem, so this version filter can be considered as a 'belt and braces' replica of the 'independent highest frequency modelling version .

Extended drive unit modelling

Linn has invested significant effort in improving our acoustic measurement capabilities (bought a very posh laser measurement system, built an anechoic chamber, written a new measurement suite) which gives us a much clearer picture of what the loudspeaker is doing. With Katalyst in the speaker, we decided it was time to re-examine the 350. The results of this work are described as Extended drive unit modelling. Previously, we treated each unit in general terms, correcting for the roll-on and roll-off behaviour using a model-based approach. The extended models treat any consistently measurable acoustic aberrations in the pass band of each drive unit, while also adding more precision to the fit of the general models. The result is a response from the speaker which runs more closely to linear phase than before. Previous filters resulted in a phase response to within +/- 15 degrees of linear over the full range of the speaker. The extended models get closer still to a truly linear phase response.

Gain Adjustment

This is a more complete model of the servo bass system was derived and implemented, providing improvement for both systems and accounting for the extra filtering from the input board of the 350P to the external Exakt system. The ‘Balanced emphasis’ filters have been developed and deployed for each drive unit to improve the dispersion characteristics of the speaker, resulting in better imaging. The extra filtering deployed in the ‘Extended drive unit modelling’ filter release was revisited and improved, yielding a more precise linear phase response.

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