The damping factor is determined by the quotient of the speaker impedance and the output impedance of the amplifier. To state the damping factor figure of an amplifier is meaningless, as the speaker impedances varies with the frequency and the various types and brands of loudspeakers existing. The figures of the true damping factor are only valid for a specific amplifier/ loudspeaker combination. This fact gives one of the reasons why Lab.gruppen don’t publishes the damping factor figures.

The only figures that are relevant for amplifiers are the output Impedance figures. Most amplifiers on the market only show low output impedance (or high damping factor) at low frequencies and high(er)at high frequencies. This is due to the improper design of the output network and/or frequency dependent feedback. Lab.gruppen design has the feature to have nearly constant impedance over the audio frequency band with a value of 0.05 to 0.07 ohms (50-70 mohms). This causes less coloration. Another feature of the power supply in the fP 2200 - fP 6400 (thanks to the stabilised power supply), is that the output impedance doesn't rise during clip situations. In most conventional amplifiers the impedance rises 10 or l00 times during clip. That causes uncontrolled movements of the speaker-cone. The conclusion must be that the Lab.gruppen switch mode power supplies sound better or have better definition, especially in the bass region, compared to conventional designs.

Damping factor influences on active and passive frequency divided loudspeakers

Another reason we do not publish the damping factor is that it’s not relevant to the audio quality of the power amplifier. For example; a professional loudspeaker driver has a DC-resistance between 2 and 5ohms, which is connected in series with the driver in the equivalent circuit diagram of the driver. In this case, the damping factor has more to do with the speaker itself than the amplifier, as the speaker driver is connected directly to the power amplifier just as in an actively divided system (see example below). In a passively divided speaker system the filter network circuit are placed between the power amplifier and the speaker driver. In this case, however, the filter impedance determines the damping factor of the speaker driver. The output impedance of the power amplifier can influence the characteristics of the filter response, but it’s not sure that a lower impedance (higher damping factor of the power amplifier) will give a better response. A classic example is the tube amplifier, which has relatively high output impedance and which gives a very good sonic result in most cases.