Thanks Cooldude

I can't mess around with the cabling going to my Pentas, but this evening I dragged the Cona down from upstairs and plugged it into the speaker 2 outlets on my BM 8000. Because of this, i could switch the Cona in and out at will by using the speaker 2 switch. Results were good - I tried a variety of types of music: indie/rock/rap/electronica and I was really happy with the extra bass sound the Cona gave. It definitely improved the listening experience for most types of music, but I have to admit that it did take a little getting used to. 

I think if we move to the place with the double-height living space then I'll use the Cona. The extra bass will easily be swallowed up by the space, and it can always be switched in and out when required should anyone complain about the noise!

I fully agree, Alex, 2 subs would sound better and make a better balance with the pentas. 

Smart thinking

Not only will it match the Pentas better, but IMO stereo subwoofers are naturally better than mono subwoofers. While many claim sub-frequencies are impossible or difficult to locate (ie, you can't hear where they're coming from), I don't agree. It's highly reliant on room acoustics but for example in my bedroom I can very clearly hear where subwoofers are placed whether the crossover point is 40 Hz or 140 Hz or anywhere in-between.

Not only is the locatability an issue for me, but the imaging plays a role from my experience. Having subwoofers running in stereo (not just both subwoofers on each side playing the same thing, but a separate channel of audio for each sub) seems to make things sound less condensed and generally make the bass sound 'bigger' without it getting boomy/over the top.

I hear what you're saying, and two Conas would certainly look good.

How would this work in practice though? The Cona has a double voice coil that sums both left and right channel inputs, so how would I get a stereo bass effect for left + right channels? Would I just hook up the left channel to the left Cona, and the right channel to the right Cona? I'm not sure that you've considered the equipment I'm working with here!

I think you would need to bridge the output  - take the left hand channel from BM8000 socket 2 and feed to one Cona input on both left and right channels.  Undertake a similar operation for the other Cona - feeding right to both right and left....

Whilst I accept everyone hears things differently - why would B&O make a single subwoofer  (BL2 & Cona) if they could have persuaded people to buy 2? 

Brian 

You can buy two, there's nothing stopping you. For a lot of people though, one is enough.

RE connecting, I would effectively bi-wire the subwoofer and run both the connections into the Beomaster 8000 outputs, and wire both outs into the Pentas.