I know it's not recommended, I just tried following setting:

-V 5 --vbr-new --athaa-sensitivity 1 -b 128

and compared it to

-V 5 --vbr-new --athaa-sensitivity 1

both files had almost the same file size and the bitrate was always almost the same (sometimes there were differences at around 1-2 kbps).

Is that a conclusion that -b 128 affect a lower quality? Watching the Encspot graph, I noticed that more 128 kbits were used, but less high bitrates.

All you are doing by adding "-b 128" is changing the minimum allowed bitrate from 32kbps to 128kbps - it shouldn't degrade quality in anyway, just means the bitrate should not drop below 128kbps - even when only very low bitrates of e.g. 32kbps would normally be required.

For -V 0, -V 1 and -V 2 "-b 128" is default. Manually enabling it is not really necessary - the default VBR options are pretty good!!

EDIT: However, I am not an expert - have little techincal knowledge of the LAME VBR modes.

Adding a "-bxxx" bitrate constrain to VBR encodes has no direct influence on the quality. It only affects what frames are allowed to be used and how many bits are available at maximum. This switch is useful if you have a buggy hardware player with restricted bitrates.

IIRC that was true until LAME 3.96.1. Now it goes down to 32kbps too

Nope, that's right. Lame 3.97 using -V 2 till -V 0 without --vbr-new means that 3.97 uses --vbr-old by default, so the minimum bitrate is 128 there. adding --vbr-new there's no more low bit limitation.

You're right! I didn't knew it because I only use vbr-new now. But I hope nobody is encoding with vbr-old these days

IIRC, Lame 3.97 (at least at) -V2 old method uses 32 as minimum bitrate using the exe, while 80 using the dll, as confirmed by EncSpot.

BTW, I still encode using the old vbr method. Sorry to burst your bubble HeXeR.

Audiograbber, too? Now you're burstin' my bubble.

Yup, and another thing, I also still use the FhG ACM @ 128kbps from WMP 11. Life is sweet! 16khz ain't gonna burst my bubble, though!

EDIT: And you're still on the Audiograbber forums too, odius_m. Now you're burstin' my bubble!