SPL PassEQ

The first generation Passeq was the first passive equaliser to provide three separate frequency ranges for boost and cut. With 12 switchable frequencies per band, i.e. 36 frequencies for the cut and 36 frequencies for the boost, the Passeq was the most powerful passive EQ filter network of all time. The same number of boost and cut frequencies is now also available with the new PASSEQ Mastering Equaliser. However, the selection of frequencies has been changed and the Q factor, or quality factor, has been individually re-tuned for each selectable frequency using an optimised coil, capacitor and resistor combination. Each boost and cut frequency now has an individually optimised Q factor.

The entire passive filter (variable resistor, capacitor and coil) delivers a very nice sound characteristic. In addition to the choice of components, the charging behaviour of the capacitors and the saturation behaviour of the coils play a major role in this. The resulting relative inertia compared to potentially very fast active filters is the reason for a pleasant, musically favourable sound characteristic. We would choose smoothness and transparency as well as strikingly silky highs and pithy basses as a suitable description for our perception.

During fine-tuning, through component selection, in countless listening sessions, the focus was on achieving the most musical sounding curves possible, which need not shy away from comparison with a Pultec EQ from the 1950/60s, for example. But without all the disadvantages of a 60-year-old original, such as the very high noise floor, but above all the very limited frequency selection.

The mid-range bands in particular are now tuned more harmonically for sum processing than on the previous model. The mid range cut band now starts working from 200Hz. We have had new coils specially made for this purpose.

Another highlight of the new PASSEQ is therefore the HF+ band, which has been extended by the frequencies 25kHz and 35kHz and sounds so incredibly good that you won't want to switch it off.

The output level can now be raised or lowered by 10dB using the large rasterised output control in order to address subsequent devices at the perfect working level. This is particularly important for use in mastering.

The gain, Q (HF +) and output parameters of the PASSEQ mastering equaliser can be set in 41 steps using rasterised potentiometers (ALPS RK27 "big blue"). All other parameters are switched via 12-position switches. A perfect recall of all settings is therefore easy to realise thanks to these switches and the detented potentiometers,

As with all new SPL mastering devices, the new PASSEQ also features auto baypass. Each of the two channels can of course be deactivated or activated manually using the large illuminated buttons. However, thanks to the auto bypass, this can also be done automatically in a freely selectable time window.