2 subwoofers better than one ?

If this is mostly to be used for AV, I would spend double the money on a single better sub (unless the room is a very awkward shape). A 12" sub should be fine for a room that size.

I would definitely spend more on one better quality sub...For music or AV. Assuming your main speakers go down below 100 Hz, the sub is non-directional anyway. 

In my experience it often does rely on the acoustics of your room and how/where you place the subwoofer(. I will say this though: its easily get an 'even' bass reproduction using two instead of one, so that is what I would suggest. But still, try not to skimp on the subwoofer quality if you want two of them.

Start with one quality 12" Sub, position is correctly and see what you think.  Just be sure to try different locations like the corners first and then try moving slow out of them.

One good sub should be plenty in your room. Normally two subs are used in far bigger cinema rooms.  But it may interest you to know that I had a demo of some M&K speakers (£900 each) with the 12" M&K sub in a room similar to your dimensions, believe me you did not need another one of those monsters!

Hope that helps and let us know how you get one

You say that but in the Paradigm demo at the Bristol show last year they had two of their multi-thousand pound subs at the front and still had a smaller model at the back for "fill-in" purposes. That wasn't a massive room, however there were no solid walls for reinforcement, which may have been relevant.

can anyone at what hifi shed some light on this please

I dont know if the team can shed any light, every room is unique and without testing its impossible to tell. For instance are your walls solid? As you heard above there was a demo with two subs.  Do you have carpet or are your floors wooden?  Is your room shaped like a box room or do you have a protuding chimney in the middle?  Have you ever tried to demo a 12" in your house and have you found the sweet spot for that 12" sub before you even contemplate the second?

You see, 2 subs can work well in the right room and right conditions but so can one. It all depends on your listening needs. But as I said above get one 12" (a good one) Ask your retailer if you can do a home demo and should you find that you need more bass after throughly experimenting then ask to borrow and test a second.  Test them out and see whether you need it in your room or not.  But for a room that size my initial feeling is that one good quality 12" will do the job.  

Take my room for example, its slightly smaller than yours 14x12 and I have one PV1 sub that is plenty.  Two of them would cause an earthquake!  But of course that is my room.

If the single sub has EQ built in, integration is made all the easier.

Increasing the number of subs in a room will almost always improve the in room response and help tame the standing waves, four subs is the ideal. Irrespective of the quality of the sub, the standing waves are determined by the room and will always be the same.

In a room of your size (which is an alomst identical size to mine), you will almost certainly have standing wave issues. Play a bass heavy track and walk slowly (i.e. shuffle) around your room, you will notice spots where very little bass can be heard, and others where bass is very heavy. Even on our two seater sofa there is a wide difference is bass between the two seats.

That said, buying a better sub will (should) produce 'better' bass; i.e. tighter, more defined and controlled, but that better sub will still be subject to the same standing waves and suffer the same sound pressure variances aroundthe room. These can only be addressed by using multiple subs, or better still bass trapping room acoustic treatments.

Using an off-board EQ device link an Antimode or Beringer can improve the performance of your sub no end. I get a huge improvement in bass definition and control, and a reduction in the extremes of the standing wave effects, from using my Antimode.

My advice would be, if you are completely flexible on sub-woofer positioning within the room, go for the better sub (especially as MK subs are excellent! Biased I know!), if you are limited on positioning, you need to see what the bass level is like at your listening position, and if it is quite lacking, two subs may prove to be the ideal solution.

Unless you're REL, who recommend one sub for every speaker, attached via high-level input!

But then, you'd kind of expect them to recommend that though really... 

Couldn't have put it better myself! Spot on!

Wow!  I bet they can't wait for the new 22.2 surround sound format coming out of Japan then!!

Agreed with Gdavies on pretty much every point. While not always practical, two subs are nearly always better than one for those reasons of room modes/flat spots etc.

Yes, but in your opinion, are you better with 2 cheap subs or spending double on a more expensive one?

Well it would depend on the room to an extent - if it's a smallish room, say 12ft x 10ft or less, then a good quality single smaller sub (Rel Quake type) should be fine, two subs or a larger single sub may well be overkill. If you're talking a larger room, say 16ft x 12ft then one large sub or two smaller ones will be about on a par as long as there's no particular room mode issues. For larger rooms than that I'd always recommend two subs of "ok" quality over one larger or higher quality unit.

One big sub may reach very low but that doesn't help if you have flat spots around the listening area (and the middle of the room is normally a problem area in that regard) or if you sit along a wall that accentuates bass, requiring you to turn it down and sacrifice impact.

Two subs, preferably in opposite corners in an ideal world will most likely offer the most uniform room coverage (unless you're going massively multi-sub) and also not have to be driven as hard as single unit - something that can draw attention to it ruining the surround affect.