Active Crossover

This started off as a 2-way crossover and was later updated as a 2.5-way with a mono sub-woofer channel. It's served me very well over the years!

 In its present incarnation it has 4th-order Linkwitz-Riley filters based around high quality op-amps. It also features a 7 stage delay network that can be connected to either the high or low pass filter sections to correct for differences in the acoustic centres of high & low frequency drivers.

Currently it's resting while I design a new speaker system with a DSP based speaker management system. But I expect it to rise again after another update to add an extra low-pass section to make a 3.5-way or maybe a 4-way system.

Parametric Equaliser

Back in the day, EQ's were parametric if they weren't graphic. The limitations of graphic equalisers meant that a parametric EQ was the thing to build. But the complexity involved in building an analogue version is quite daunting- if only to drill the holes & put all the required markings onto the front panel!

Each channel is fully independent each with 4 filter sections, 3 true parametric and a shelving high-pass filter with adjustable frequency. The parametric sections are switchable between two frequency ranges for extra flexibility. A gain make-up control allows the overall perceived SPL to be matched to the non-EQ level. The filters are bi-quad op-amp based filters using high quality op-amps. Each section and the complete EQ cab be bypassed as neeeded.

The analogue parametric filter still sounds very good but has been replaced by digital versions. They offer better sound quality than active analogue EQ's and are much easier to use. The only analogue EQ's that are still competitive in sound quality are the passive cut-only filters such as those made by White Instruments. But these are only fixed frequency filters with limited flexibility and and very limited ability to provide correction for acoustic problems.

Currently the ol' EQ is sleeping peacefully having been replaced by a digital speaker management system.