I recently purchased a second hand JBL Cinema SB400 Soundbar with wireless sub on eBay. Unfortunately the sub part had taken some damage in transit namely two broken feet, which I managed to repair and a missing control knob on the crossover, which makes it difficult to see what this is set to. 
Regardless of whether I keep it I'll be seeking a partial refund over the cosmetic damage. However, despite all that, I'd like to keep it if possible as the soundbar has a really nice rich warm sound and definitely seems more lively than my Goodmans soundbar, which itself was pretty darn good for the tiny amount it cost.
Anyway, while the soundbar is definitely working (touch wood) I am unable to determine if the sub works. It turns on and seems to be connected to the soundbar (its wireless so no lead) as it enters standby when I put the soundbar to standby and comes on when I turn the soundbar on. However, I just can't detect any clear audio from the sub, it seems like the soundbar is doing everything. I put on an action movie (Jurassic World) which I thought would have had loads of loud bass-heavy areas to work out the sub, yet while there was tonnes of sound, it all seemed to be coming out of the soundbar with none of the deep base from the sub I was expecting.
I have seen a number of suggestions for testing subs online including touching the RCA lead going to the sub or even connecting it to a battery, but as its wireless such methods aren’t going to work. I was thinking of trying to find a dedicated track for testing sub frequencies. I have found the THX test on youtube: https://www.youtube.com/watch?v=PC7WEQsiz08 but I’m not sure if it’s a good idea either as I’ve heard some say that these test tracks can be too severe for some sub woofers and actually damage them? But then how is one supposed to test if it works if you can’t play a test track?
Any advice greatly appreciated.

Regardless of whether I keep it I'll be seeking a partial refund over the cosmetic damage. However, despite all that, I'd like to keep it if possible as the soundbar has a really nice rich warm sound and definitely seems more lively than my Goodmans soundbar, which itself was pretty darn good for the tiny amount it cost.
Anyway, while the soundbar is definitely working (touch wood) I am unable to determine if the sub works. It turns on and seems to be connected to the soundbar (its wireless so no lead) as it enters standby when I put the soundbar to standby and comes on when I turn the soundbar on. However, I just can't detect any clear audio from the sub, it seems like the soundbar is doing everything. I put on an action movie (Jurassic World) which I thought would have had loads of loud bass-heavy areas to work out the sub, yet while there was tonnes of sound, it all seemed to be coming out of the soundbar with none of the deep base from the sub I was expecting.
I have seen a number of suggestions for testing subs online including touching the RCA lead going to the sub or even connecting it to a battery, but as its wireless such methods aren’t going to work. I was thinking of trying to find a dedicated track for testing sub frequencies. I have found the THX test on youtube: https://www.youtube.com/watch?v=PC7WEQsiz08 but I’m not sure if it’s a good idea either as I’ve heard some say that these test tracks can be too severe for some sub woofers and actually damage them? But then how is one supposed to test if it works if you can’t play a test track?
Any advice greatly appreciated.
) you should be OK.