PT-3 : Active 3-way Crossover Network

Phase Coherent Outputs, Plug-in Custom -24dB/Oct Crossover Modules, Independent Output Level Adjustments (6dB in 1/2dB Steps)

High-end passive crossovers networks, as refined as they can get, still suffer the same problems all passive filter circuits suffer. This is the just nature of passive design, even the best high-end designers cannot change the laws of physics.

Expensive "designer" components and good circuit design may ease the pain of a passive crossover, making it more listenable, but the problems will still be there, announcing themselve from time to time in the music program.

Problems associated with passive crossovers can include: presenting a difficult load to the amplifier; generating power losses that may require more powerful amplifiers to achieve the desired SPL; poor control over phase shifting; poor control over the crossover frequency; poor channel matching; inconsistency in production units; loss of transparency; degraded damping factor; along with degraded driver control causing distortions and a loss of detail.

There has been much written on the subject, and problems, of passive crossovers and it may suffice just to say that if you could remove them it would not be a bad thing. Some of the best passive crossover designers try hard to keep the component count at a minimum to preserve the sound quality.

Replacing passive crossovers with good active crossovers and bi or tri-amping will improve almost every loudspeaker system. There are exceptions but, very few.

The main advantage of an active crossover is it's ability to very accurately control the output signal level, phase, and quality over the complete frequency range we use in audio reproduction, consistently.

A secondary advantage : Normally during final amplification all frequencies are present in a single summed wave. The high frequency signals tend to clip first while ridding the bass wave, which contains most of the music program energy. This not only sounds bad but can actually damage the tweeters. This problem has traditionally been solved by using a higher power power amplifier with plenty of headroom. Going active more efficiently solves this problem allowing the use of lower power amplifiers which normally sound better and also can cost less.

Good active filters used at line level provide a far superior crossover solution to any passive line level or speaker level filter circuit combination.

Note - Some highly tweaked loudspeaker systems may not benefit from standard active crossovers. These systems may have been voiced to the designers preferences while covering up certain existing fault conditions.

Designers sometimes manipulate passive crossovers into quite complex networks. Compensation circuits, that fix problems, can be added to the actual passive crossover filter circuit. Compensation circuits are not normally duplicated in a standard active crossover.

These complex systems would most likely benefit from a more complex active crossover network but, it would need to be application specific for each loudspeaker model and this type of custom network is not practical to mass produce.

That said... extremely complex loudspeaker systems are quite rare and most of the loudspeaker systems out there today will indeed benefit from going active with standard active crossover networks.

It's easy and nondestructive to try active mode and if there is no noticeable improvement returning to the original passive crossover is equally as easy.

The PT-3 active crossover network uses fourth order (-24 dB Slope) Linkwitz-Riley filters and buffers. This elegant circuit keeps all three outputs (high-pass; band-pass; low-pass) phase coherent (in perfect phase with each other) which greatly enhances the music listening experience.

Standard filter 24dB/Oct L-R crossover points are listed on our “Products” page.

Custom filters (different orders and different types) can be supplied but may require a small PCB fee and a longer lead time. We can make just about any filter type, order, and combination.

PT-3 Features