Well, Pieter Stenekes from Sonoris is turning out to be one of my favorite audio dsp coders as he has been consistently turning out fantastic stuff - and he really comes close to the Algorithmix stuff at less than a tenth of their price with his latest plugin.
Here's the info from Sonoris:
The Sonoris Linear Phase Equalizer (SLPQ) is a parametric linear phase equalizer in the SAWStudio native format. The plugin features 7 bands, including lowpass, highpass, peaking and shelving filters.
The linear phase algorithm of the SLPQ is based on a technique called “backward-forward filtering”, until now only implemented in some expensive high end equalizers. The main advantage of this technique is that IIR filters can be used instead of FIR filters, the latter is commonly found in linear phase implementations. IIR filters are known for their more analog kind of filtering and are also more efficient than FIR filters. The filters used in the SLPQ are actually the same as in the Sonoris Equalizer and has also correct gain up to Nyquist.
Until recently, this type of processing was not possible in real-time, because it needs a fast CPU. It also introduces an unavoidable latency, but the plugin automatically compensates for this. In the options menu you can choose out of 4 quality settings, from low to extreme. This way you can fine-tune the CPU load. When necessary, set the buffersize in SAWStudio a bit higher to avoid clicks.
The plugin has a large graphical display that shows exactly what you get. The Sonoris Linear Phase Equalizer has a HQ switch that enables an upsampling mode. In this mode, the SLPQ has an even more accurate response, especially at the higher frequencies.
Features