What strobes to light a large dance floor?

Is this a reception dance floor at a wedding? As opposed to a recital of a dance studio...

If so, you don't need very powerful lights, particularly if you are going to use 4 of them. Most DSLRs these days are capable of perfectly nice higher ISO images, meaning shoemounts will work just fine, in most cases. Monolights--maybe if you are going to bounce only and maintain a low/medium ISO or smaller apertures. 30x30 is what I'd consider medium sized. I'd probably be using 2 off camera lights.

Yes, this is for a wedding. Nadine, what brand are you using? I don't want to go too high with ISO, with my 5DMKII I try and stay at 1600 or less.

I shoot most dim/evening receptions at ISO 1250, using 2, sometimes 3, off camera flashes. I have 2 Sunpak 120Js, but I don't always use both. Sometimes I use a shoemount--I have various ones. Presently, one of them is a Vivitar 285 because it has a metal foot and takes a beating. I have two other Metz shoemounts that I can use, as well as another Vivitar 283.

I also have a Norman 200B and a Dynalite UNI400, which I've used when I knew I'd be bouncing flash all night long in medium to large spaces. I also have a Dynalite corded system, but I hardly use that for wedding receptions.

I use two or three Nikon Speedlights mounted on clamps or with velcro straps up high and out of the way. I own several studio strobes, but would never ever use them during a reception; you're asking for a lawsuit when someone trips over a cord, or a broken strobe when a stand gets knocked over. That can be an expensive lesson to learn. Besides, you generally don't want the entire floor lit, you do want to open up the background a bit, but you don't want a nighttime reception to look like daylight (plus too many big strobes going off is annoying to guests). Addditionally, keeping the rest of the room a stop or two darker will help to isolate your subjects, and maintain the mood.

Look for something better when it comes to strobes. Around 500-600 true Ws, recycle time around 1 second at full power and the ability to set the flash power down to 1/16 power or less. If you can change the power remotely that might be useful as well.

Speedlights are a useful tool but strobes are superior when it comes to flash power and recycle time. Easier with strobes if you are two shooters firing the same strobes. I would prefer to use strobes all the time but they take longer to set up since they need ac power so many times it's easier to use a couple of speedlights.

I think two strobes are a good starting point. I would take a look at the Einstein strobes or the Elinchrom bxri. Remember that you can use your strobes for other purposes as well.

Thanks for all your responses. I've shot weddings with other photographers and they were using elinchrom and Whitelightning from Paul Buff. Elinchrom units are so expensive I don't think I can justify the price.

Alex one of the photographers I've worked with, has been setting up lights for the past 30 years and has never had a problem with people tripping over them. They are usually setup in a corner or right by the DJ.

Sometimes aiming strobes at the dance floor with a second, third,or fourth strobe will cause havoc with all sorts of issues, such as shadows, over exposing, underexposing, temperature changes, and whatever you can think of that can go wrong.

You surely can bounce strobes placed in the back and light up the tables, with people of course standing around.

Sometimes I will backlight the B&G during their first dance, That can be a fun shot lighting up her veil. As always, when doing something new, cover yourself by shooting the normal shot you've always done.

If you have a meter and your camera is pretty much set at f-11 the background strobes would be cool if you set them up around F8 to 8.5. If your camera is set at 5.6 I think the extra strobes would look great at F4. So a 1/2 to 1 stop lower is a good start.

Lukasz, the bxri is Elinchrom mid level monolights (RX is their high end). They are $585 each so more expensive than the ones you looked at but not as expensive as their RX models or other high end models like the $1200 Profoto D1 500Ws air.
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Lukasz, for the reception dancefloor with my 5dmkii I usually have the 580 exii on camera in ettl and a 430 in manual at 1/4 power synced with pocketwizards. I then drag the shutter to usually around 1/40th and shoot fairly wide open and then bring my iso up so that the background is underexposed by about a stop. Usually I don't have to take the iso above 800 for this. Depending on the venue I have the 430 bouncing straight up off the ceiling or have it aimed right at the dance floor. This has resulted in well exposed dance floor shots for me in even dimly lit reception halls. Having the 580 on camera with its autofocus assist beam is clutch too.

I have contemplated getting an elinchrome so that I can do some cool work a la Zach and Jody gray outside to get some great dramatic skies, but for receptions the speedlites have been plenty powerful for me.

At 1/4 power the refresh time is pretty speedy too on the 430 exii.