BK Electronics' subwoofers are clever bits of kit, and in a function-leads-form way you could be forgiven for confusing their products with a couple of other brands. A veneered cabinet enclosing some air and made of thick MDF, plus a panel with an amplifier and connections on it, are going to breed this sort of look.

In my opinion, a real indicator of cunning enlightenment - and true of any brand of sub that has this - is the use of both high- and low-level inputs at the same time. It isn't the 'more-is-better, it'll be louder and go to eleven' thing. It is about the Low Frequency Effects, or LFE, channel from your processor.

Missing out on bass

A movie's sound engineer will put bass in there as he sees fit during the mixdown, but if the recordist who made the soundtrack material has created stuff with deep frequencies in but the mixer doesn't suss it, the LFE channel doesn't get the bass and the movie is less exciting as a result.

It has been happening since the days of Lion King. Check out the partridges under the elephant feet in the beginning. They missed them out in the rears! And the elephants' footfalls only boom in the woofer channel sporadically. So, using both inputs is about picking up all the LF information, and creating better bass by sending all that was recorded in that passband to the woofer.

Of course, you do need to have the levels of these two inputs separately controlled, and this means twice as many knobs as normal, which is why it's not often done. So, when you find a sub with this feature, it's almost always a good sign, and means a brand which knows its onions.

The passion of the driver

Another good sign of this BK XLS200MkII is the mad-looking driver. Like the one on the REL, it is hugely heavy-duty and has a big top suspension surround.

The enclosure sits on stubby feet with its driver pointing downwards, and the look is 'woody cube'. Yet despite its small size this box throbs with passion. It drops with a bizarrely deep extension and, despite a small cubic capacity, seems to hold a melody and make some decent dynamics.

Forty minutes into Pirates of the Caribbean: Curse of the Black Pearl, an axe whumps into a table - and this woofer loved it. When the gang head to the isle of Tortuga around the 48-minute mark, there's a massive, bassy swell in the soundtrack. And whaddyaknow?

The XLS200 loved that, too.

We say...

This BK is bogglingly potent for its size and absurdly good value for money. Just think: you could have three or four of these for the cost of the bigger ones in this group...