These speaker are based on active filters and separate amplifiers for Bass and ESL and we have tested various variants.

Johns set up

Power amplifiers

Zapsolute is a good old danish DIY amplifier that delivers 100 watt in class A or class AB. It is able to supply the high currents needed for capacitive load. John has build a rather heavy version that delivers 4*100 Watt.

Active cross over filter

An active analog LR4 cross over filter. Different cross over  frequencies have been tested. John has settled on 450 Hz.

Steens set up

Power amplifiers

A Zapsolute 2*100 watt to drive the ESL element and an ICEpower 500A 2*500 watt to drive the bass speaker.

Active cross over filter

I have experimented with miniDSP as active cross over filter (LR4, 350 Hz) and frequency compensation. It is possible to get very fine frequency response as you can see in the Measurements page but miniDSP is not as transparent as I wood like.


We find that the bass is very satisfying after frequency compensation with miniDSP. We also find, that miniDSP is less transparent than an analog active filter.

We also have a number of new ideas that we want to explore so our project will continue during the winther 2015/16. This site will be updated with new findings.


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