speaker to big?

Panu21,

You should definitely work on acoustic treatments (broadband traps) for the bass and consider a Parc or Room EQ Wizard. Boomy room modes can really clutter up detail in the bass. A small monitor might indeed be better provided it is a sealed box and rolls off around 60 Hz...in some cases "less is more" as your ears can figure out the reduced bass frequencies from the higher harmonics anyway...whereas bass boom can disguise or hide detail.

In a room that size, you can get away with -3dB at 40Hz pretty easily - especially with some furniture and doorways in the room. There are many floorstanding options with this level of bass output. Your room is close to mine (14x13) and my speakers are 38Hz at -3dB but I have some bass traps in the corners and speaker placement was fairly critical. So anything with a little less bass than that should be fine for your situation.

Most monitors won't have this kind of extension so if you can live with less bass, then they are a fine alternative. I personally feel that solid bass extension is required for high fidelity, but to each his own.

Arthur

I had a pair of Gallo Ref 3.1's in my room, which is similar in size to yours. I could not get rid of boomy bass caused by standing waves. I sold them and bought a pair of Harbeth Compact 7ES-3's. These speakers integrate into my small room much easier than the Gallo's. YMMV...

Two considerations:

Large speakers are usually designed that way to accommodate larger woofers. This may overdrive a smaller room. Also, remember that nearly all speaker cabinets vibrate to some degree, thus they add to the soundfield. The larger the cabinet, the more potential for this.

Second, larger speakers may have drivers spaced further apart and require a more distant listening position to allow them to integrate. Also, in producing more bass, they may need placement further away from the front and side walls, thus requiring a larger room.

It depends on how much importance you place on the presence of deep bass info vs the insertion of an add-on parametric equalizer.

Personally, I would opt for a 'fuller' range floorstanding speaker and lopping the tops off low frequency nodes caused by room dimensions (or necessary set up compromises) than relying on minimizing room problems with small speakers or room treatments for a couple of reasons.
1) Some of the room/bass problems can be well above 60hz, well within the effective response of many 'monitors' and can really muddy up bass response.
2) It is very difficult to treat a room to eliminate or minimize deep bass problems related to room size. Resist buying into all of the hype hear about band aid products. DO some research into acoustics for your self.

FWIW even if you can't set up the speakers that you decide to buy for your room, try to find some of similar size and frequency response and listen for yourself to see if they create any problems (for you, not just in theory).

FWIW.