I live in a semi-detached house and, like with a flat, you expect to hear a certain amount of noise at times. Generally my current neighbours a pretty reasonable most of the time so we tend to get on fine.
The neighbour prior to them though (that house is rented) was a complete nutjob about noise ... after trying various things and being blamed for making too much noise again and again (including when the source of the noise was another neighbour mowing their lawn) I eventually did a test and asked her if there was to much noise "now" ... she said there was ... I then pointed out that the power was turned off at my fuse box and nothing was on in the house.
I would expect to hear a certain level of bass leakage and that would be fine as long as it was at a reasonable time (from what the OP has posted it seems to be) and not intrusively loud (again from what the OP says ...). Trouble is once things around noise become sensitive then relations can go downhill quickly.