I determined by ABXing that for me it is imposible to recognize a song lowpassed at 18000Hz (even though I can hear a sweep up to ~19500Hz), So I was thinking about using 18KHz as the lowpass filter when encoding my APEs to MP3s for my portable.

But I'm unsure if it was safe to change the lowpass filter in the alt-presets since many are told to leave the presets without any command line modifications.

I'm using Lame 3.90.2.

PS. I lowpassed the wavs using CEP2 @ 32bit, and dithered the results using a triangular 0.54-bit dither. then used WinAbx to compare ( Are there any errors in this approach for determinig my lowpass cut-off )



Sorry for my English.

By changing the lowpass with APS yes, you will get reduced quality. At least that's what i got when i tried it with some songs. It's probably always best to leave the alt presets as they are, so they'll work best.
(don't be sorry about your english, it didn't offend me that much .. {edit: -I- like your sig })

Well, I guess I'll leave then alone. A lowpass at 18KHz is doesn't represent a 'great' bit-rate reduction anyway.

Thanks for you answer.

Have you tried APE -Y? IIRC, APS -Y applies a lowpass at 16 kHz most of the time, only encoding higher frequencies if there's much energy. For some types of music it decreases bitrate noticably. The -Y switch is considered to be safe for APS, but I'm not sure about API. Maybe someone else can tell?