high pass crossover - active, passive, simple or complex?

[nick78]

My main speakers are fairly small (MTM's with 5" drivers) yet very revealing, and I assist them with an NHT subtwo active subwoofer. The NHT comes with a sub controller, which sits between the preamp and amp, and acts as a lowpass for the sub and highpass for the mains. it has continuously variable XO points for both the LP and HP.

all the active wizardry and sub-par components in this sub controller aren't doing me any favors in terms of sound quality, and I'd rather not overhaul the entire controller with better components at this time.

So, any suggestions as to my best option for a highpass (only) filter to feed my amplifier with, instead of relying on the sub controller? At the moment I'm thinking that a minimalist approach would be best - a high quality cap and resistor, passive fixed XO just before the amp, but I'm open to suggestions.

[AndrewT]

Hi,
use your sub controls to identify the crossover frequency and slope that you think best suits the combination sub & mains.

Now build a high pass crossover, that mimics the sub processing, to filter the wideband signal to the main speaker amplifiers.

Decisions; for low slopes, single or two pole, you could go either active or passive before the amplifiers. For higher slopes, I believe, your only choice would be active.

If your speakers have a Q that emphasises the upper bass, you can tailor this with a filter Q that is less than 0.7 (Butterworth) built into the filter. If the emphasis is higher up from the crossover point then you would have to add equalisation. Identifying that and correcting it would be a much bigger project.

Tell us the results, particularly if you decide to compare the options.