Types of speakers to create nightclub style sound?

As someone who dove into a similar challenge a few years ago, I don't have a complete solution but here are a few considerations I learned along the way:

- Midrange (and separation thereof) is the most overlooked aspect when trying to emulate the 'club sound'. Fairly aggressive separation at the crossover level, coupled with placement of dedicated speakers is key. Funktion 1 does this extremely well, to the point of sounding 'unnatural' or having a 'sound'. (As mentioned in the comments under that RA article shared above)  I personally never understood the application of hi-fi ideals to club setups: Club sound systems are designed to create a very specific experience in a very specific environment. Throw in a few hundred people mingling freely under various states of the mind(:) into the mix, and things like 'accurate reproduction', or 'transparency of sound' become useless consideration. Having experienced Funktion 1 setups in many possible variations from small to ginormous, their magic lies in the fact that you can carry a conversation with another person without shouting and fatigue no matter where you are in the space, while still 'feeling' the music. That's due to that aggressive separation of low / mid / highs. Anything you run through a Funktion 1, well, will sound like Funktion 1. 
As a takeaway, I would go for speakers that imitate that, or at least have a strong, dedicated midrange component in their design. 

- Take into account the music that's designed to play in the club environment. Electronic music that's mixed / mastered for clubs is a complete different beast than anything that would be acceptable as a good source, at least around here :) (Intense bass emphasis, maniacal dynamic compression techniques, and exaggerated transients that are designed to cut through any background noise etc.)

- While it's true the older club setup did make use of them, I would stay away from anything involving tubes especially if Funktion 1 is your reference.  I've been frequenting a few 'hi-fi' clubs that are popping up in and around NYC (mostly trying to imitate the ones in Tokyo), which mostly have systems that are either made up of, or emulate that altec / klipsch / bose setups and I have to say they leave a lot to be desired within your context. A quiet listening session of some delicate ECM record works really well, but the moment you throw in something meant for the *dance* club, and people moving about, those systems start to fall apart, IMO. 

The Bag End suggestion above is an interesting one. I'm not familiar but it does seem like they're going for something similar to your goals. 

Do report back where you end up! This is a very interesting discussion.

I've done 3 night clubs way back when.  In one I did indeed use bag end.  They were some of the better sounding drivers that didn't crap all over themselves when pushed.  In 2 others,  we built the speakers from the place where I worked at the time called SpeakerCraft/Marcof Electronics.  We built a 15 inch 2 way that was quite good.  
In both cases,  I was very conscious of making the dance floor a loud yet tolerable place and keeping it so that you could have a conversation 10 feet off of the floor.  I found to really do this right that the speakers had to be hung.  They needed to be tilted down slightly and they needed their backs away from the area most worried about sound travel.  So if you have a place where guest will congregate most,  you do not want the speakers to be placed where they can fire toward your guest.  Hang them firing toward the floor with the backs to the congregating area. 
I normally used old Sumo Andromeda's back then,  today there are several amps at 150 to 250 watts per channel that would sound better.   Large drivers move air well and are normally higher sensitivity.  I would recommend a high sensitivity speaker if possible.  Our builds were 97 and I recall the Bag End Models that we used at being around 100, Maybe 99.  I hope this helps,  Tim 

I agree with others that horn speakers are often used in the club setting. A friend used multiple Klipsch with subwoofers strategically placed in the club he designed.
Also, EQ is needed since you don’t have much control over the various room surfaces. I include the amount of people in the space as affecting the EQ as well.
This is very different than an audiophile’s dedicated room.

I do live concert production/mixing...have for many years...Consider powered P.A. speakers from Mackie as they’re not expensive and they sound great, and you can run 100 foot balanced lines to ’em. The newer "v3" SRM 350 10" 2 ways are only 23 lbs (neodymium woofer magnets) and 1000 watts (!) with built in signal processing. They're pretty much indestructible...You can buy little rigs for hanging these things. The "v2" version is also light and powerful and less expensive...match them with one of their 18" powered subs and you’ll dance all night at levels that can make your ears ring for months, cause structural damage to your house, and alienate any neighbor within a mile. A little mixer with balanced outs is all you need to drive the things.

I've always been curious about PA sound as it can often provide a very immersive sound, at volume that somehow is not fatiguing. Is this due to frequency balance/sensitivity? I note many PA set ups do not try to reproduce low bass (using a filter of roll off is say 60Hz), I assume there are some frequency bands that are reduced that might otherwise cause harshness at those higher volumes.