When I want to use a (very) steep highpass filter around 25 Hz to remove subsonic noise, should I use a Linear phase EQ or would that introduce side-effects?  I read some things about pre-echo's but I am not yet familiar with that phenomenon.  Would another type of EQ be more suitable?  If so, which plugin?  I need VERY steep settings.  Until now I have used a Waves plugin (twice to get the result I needed).
I am asking because relatively short IRs inherently are different sources to process than longer music clips.  And they actually contain digital IR filters themselves (each peak/echo is also a filter), so I am a bit worried that using the wrong type of EQ could affect other aspects of the IRs than only the low frequencies.

Thanks for any early reflections ;)

Peter Emanuel Roos
www.PeterRoos.com / www.Samplicity.com (IR libs)

Using linear-phase EQ with very low cut-off frequencies (like below 40 Hz) for impulse responses is not the best thing because this will introduce a lot of latency - if you cut it, impulse's sound will be damaged.  Minimum-phase is the best option.  For example, Voxengo Elephant's DC filters can be a good choice (they are -36 dB/oct high-pass filters).  I do not suggest you to use steeper min-phase filters than that, because that may introduce a very high overshoot, and a very unfortunate (towards impulse's "pristinesness") group delay.

Thanks Aleksey!

My intended use for this EQ is during the production phase (not in a runtime mixer setup), does your latency remark also apply here?  In the sense that delays are introduced into the original Wave form?
I use Sony SoundForge for editing and mastering stereo files.  I have a pile of Wave plugins and a smaller number of Voxengo plugins (Elephant, GlissEQ and PS of course! :) :) :)

Peter Emanuel Roos
www.PeterRoos.com / www.Samplicity.com (IR libs)

Sure, by latency I meant an increasing wavefront that is added by linear-phase filters before the actual impulse start.