Someone else with super deep knowledge can come in and add on top of my response.
(1) There is a gentle roll off in the high frequencies… somewhere around 19-22khz will be down a touch… like 0.5db to 2db would be reasonable to expect so very subtle
(2) Reduced ringing of the slow filter which can provide a more relaxed sound
(3) Slight aliasing - high frequency noise from the up sampling in DAC will bleed into audio band.
Ok… so this is what I’ve found thus far. I’ve gone back and forth on just two filters and can reproduce the same conclusions.
HYBRID FAST MINIMUM PHASE
I’ve found this filter to be very resolving especially on vocals. Allows any sibilance to be more prominent. However, after about an hour of listening, I start interpreting the filter as harsh/bright sounding, almost grating. Reducing the volume helps but removes the bass of the music I’m listening to
FAST LINEAR
This filters seems to calm the upper end down some, but at the same time feel like i’m losing some of the resolution in the vocals.
Does any of these comments make any sense to anyone out here?
UPDATE… so this is what I’ve found thus far. I’ve gone back and forth on now 3 filters and can reproduce the same conclusions.
HYBRID FAST MINIMUM PHASE
I’ve found this filter to be very resolving especially on vocals. Allows any sibilance to be more prominent. However, after about an hour of listening, I start interpreting the filter as harsh/bright sounding, almost grating. Reducing the volume helps but removes the bass of the music I’m listening to
FAST LINEAR
This filters seems to calm the upper end down some, but at the same time feel like i’m losing some of the resolution in the vocals.
APODIZ FAST
I thought this filter calmed the ‘sizzle’ down from the HYBRID FAST MINIMUM PHASE filter. Seemed to allow the system to be played at moderate and louder volumes eliminating any listener fatique. Thought this is a filter to consider. Had my wife listen to this filter on several recordings, A/B comparing it to the HFMP filter. She felt it made the sound more 2 dimensional, ‘deep’ sounding, un involving.