The "NB 51" will unfortunately never get close to the performance of "NB10", the "NB10" Bass is rich, sound is better even at very high volume and not consumed as fast.
There still remains the "NB10" as a top favorite of the boombox series, unmatched ...
... However, the "NB51" for this price was very good (price / performance ratio), tone and bass despite all tired enough (all depends on how big the room is, sound distribution)
... Significantly more connectivity options, the "NB10" only possible CD music play as the "NB51" with a USB port (most practical option), additionally an Apple connector provides for iPhones and iPods.
... Good workmanship, how many I can not understand complaints about the processing, usual quality as always.
+++ On the whole, it is worthwhile in any case, I personally did the same a week later a second buy to have with friends while celebrating good music +++