I am gonna guess around 5-6db boost in bass so definitely not neutral bass. It has a fun amount but not M-100 levels either. The sub bass is good but rolls off on them and don't have the industrial strength the WS99 has. So not really for bass fans..But it is their mids that shine like crazy. The sweet smooth forward mids on them are the main attraction.. They are also on ears and need the WS55 pads which ends up being more money but is well worth it.
I don't find the WS99 recessed in any part of the sound. It is not as forward in the mids like the ES700 but I wouldn't say they are neutral in the mids either..These have absolutely no part of a U or V shape sound. On bass light tracks you can tell the mids are a solid notch forward.