It is not possible to disable the ABL algorithm, however:
Disabling the ABL will not increase the level of bass (relative to the other frequency bands) in any Beolab loudspeaker.
If you were able to disable the ABL, you would merely get distortion caused by clipping of the signal – either caused by
- excessive excursion of the loudspeaker drivers
- reaching the limits of the amplifiers, or
- reaching the limits of the power supply.
ABL is there to prevent this clipping (and therefore a short time with distortion, followed by destruction of the loudspeaker).
There are some people who confuse ABL with a “loudness” function (which boosts the bass and sometimes treble frequency ranges at lower listening levels) – however, these should not be conflated. Beolab loudspeakers (Beolab 28 excepted) do not have a loudness function, since this would be a feature of the source (e.g. a Beovision television) instead.