Sound Performance Lab 2595 manual Advantages of Passive Filtering, Filter Types, Single Core Coils

Introduction

Advantages of Passive Filtering

•Typically coil inductance in virtually all active filters is achieved through simulation. True passive coil filters, on the contrary, can only deliver the genuine, characteristic sound asso- ciated with inductive components.

•Inherent distortion elements of active filters are ruled out by passive filter design.

•For any number of reasons stemming from design and component advantages over active filters, passive filters achieve a very natural aural quality and through their harmonic treat- ment (THD, distortion, phase response, etc.), offering at the very least, a clear sonic alter- native, which our ears often perceive as an extremely attractive one.

•All passive filter components (variable resistor, capacitor and coil) work in concert to produce this beautiful sonic result. An important part of this process is played by coil and condenser loading and saturation characteristics. The resulting difference in latency from characteristically extremely fast reaction of active filters provides for more pleasant, musical sonic qualities. We tend to perceive these attributes in terms of an increased suppleness and transparency, with perceptibly improved, silky highs and robust basses.

72 passive Filters with 120 Volt Makeup Amplifiers

With 72 passive filters (36 x boost, 36 x cut per channel), the Passeq surpasses all previous designs of this type by a wide margin. Each channel is divided into three cut and three boost bands, each offering 12 switchable frequency ranges. The cut and boost ranges are not iden- tical; crossovers are designed to work with like a precise mechanic cogwheel so as to allow the engineer access to the largest possible number of optimal, wide-band S-curves with variable slopes. A further noteworthy Passeq feature is its individual sonic adaptation of each induc- tive filter through separate coil/condenser/resistor combinations: In stark contrast to earlier filter design and construction, each Passeq filter is optimized for the frequency assigned. To insure the best possible signal warmth, richness and musicality in processing, coils for critical voice frequencies are custom-made for the Passeq. This achieves the widest possible range and tonally appealing sound color palette from any passive EQ.

Filter Types

The Passeq employs two distinct filter types: One of these functions much like traditional shelving filters, while the other, as a peak filter, and together, they provide the combined char- acteristics of wide-band control in low and high ranges with more specific frequency range control in mids. This selection minimizes mutual influences between low, mid and high bands while providing a more selective control in the mids is often useful.

Single Core Coils

Until now design approaches have involved individually wound coils, but multiple coils have nonetheless been placed on a single core. The Passeq design places each coil on separate cores. This eliminates any possible unwanted mutual influence transmitted through common- core windings and thus, among other improvements, results in better THD values.

Peak and Shelving Filters

Mid boost and cut, as well as HF boost filers have been set up in a peak (bell) configuration, while the hi cut, low cut and low boost filters function in a shelving configuration. The HF boost band offers variable values from Q=1 to 0.1.

Passeq 7