Starting from scratch in a large room

36" shelf is a good height for horizontal speakers, beams drivers close to seated ear level. (42-48 for me, I’m tall, depends on chair height). Typically tweeters toward the center, keeping their narrow distribution more toward the center.

you can add something below as needed

btw, toe in. you can keep them ’straight’ for casual listening, toe-in some for 1 centered listener, toe them in more for two listeners, back to straight for wife factor if an issue. consider an appropriate amount of material that permits movement yet allows them to ’feel’ heavy on the shelf which hopefully is solid.

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’extra power’.

Usually I recommend efficient speakers, horn type the most efficient, (high 90’s, some over 100 db/1w/1m).

specifically to minimize the amount of power needed, especially if tube amp(s) might be desired now or in the future.

efficient speakers keep cost/size/heat down and increase placement options, consider remote beam and visible line of sight.

horn speakers enclosures, especially unvented ones are large, cubic feet determines amount of bass. (your location precludes rear/side/bottom ports, perhaps front port).

smaller, un-ported, usually efficiency drops, and often impedance drops, i.e. 6 ohms nominal, even 4 ohms nominal. there are some great sounding in-efficent/low ohm speakers, soooo to keep your options open for a large space such as yours, I will relate a recent experience:

friend, large space: 29 feet wide, 45 ft long, high ceilings.

JSE Infinite Slope Model II’s, sensitivity 91 I think, fairly easy load.

McIntosh AMP, MA2270, 270 wpc, BIG Meters.

Playing decently loud: typical 2.7 watts used; frequent 27 watts drawn; occasional 200 wpc; and infrequently but repeatedly the Power Guard came on, indicating the amp was preventing clipping exceeding rated 270 wpc.

Of course you can drive any 91 sensitivity with an 80 wpc amp, however, dynamics in content will need more instantaneous power. Size of space, desired volume, music dynamics are all involved.

So ’extra’? More power is not linear. IF I recall correctly: For each +3db in loudness (a perceivable difference) DOUBLE the power is needed. So a 150 wpc seems like a lot more than 80wpc, and yet ....

Restricting yourself to efficient speakers is wise, they get bigger, especially not ported, what is the wife factor for big speakers horizontal on a shelf?

Consider limiting yourself to a stereo amp that can be used MONO, so you could always buy a second one in the future.

I wonder if a surround system might work such as Definitive Technologies.  Wall mounted with hidden wires.  Looks like you are more interested in creating a mood rather than trying to truly image sound.  

@deertrail7, what are the horizontal and vertical dimensions of your 24" deep shelf?

The reason I ask is, in that size room adequate SPL capability and low-end air-moving capability are going to be an issue, and both of those tie back in to loudspeaker size.  So if shelf-mounting is your only realistic option for aesthetic concerns, the size of that shelf space becomes a factor.

Note that high-end recording studios sometimes flush-mount speakers in walls, so your situation may not be all that bad, assuming that a true flush-mount installation is feasible.

Duke

dealer/manufacturer

I think we're past the best advice offered up by @russ69, and @ghdprentice.

You may be happy with what you get, but it seems to be an inefficient use of spending money as pointed out. You may well enjoy the results going the other, suggested, direction.

Good luck, regardless; these are always fun projects.

@audiokinesis,

This post may read a bit differently from some of the above thread.  If your wooden countertop is situated along the 18 ft. wall, then your situation may not be nearly so dire.

If you can get say, 8-12 ft. of centered speaker separation and move your 13 ft listening position a bit closer, you may be okay.

Speaker selection and positioning will be key.   Speaker plane should be positioned at or slightly beyond the edge of the cabinet.  Flexibility for at least some tow-in will help.

Importantly, you should avoid using any open port rear-firing speakers.  Unfortunately, this may rule out your otherwise excellent choice of the KEF R3. However, a baffled rear port will allow close-wall placement.

I can speak to you with some confidence because my room is very similar, and over the course of time I’ve tried most permutations.  With some effort, You can set up a very effective near- and mid- field listening experience.  Try to think of your room as  say, 18 x 20, just without a back wall.  Listening in the back section may not be highly resolved stereo, but you can still rock out to good hifi sounds.

As for components, in lieu of my first wish to suggest Ayre Acoustics EX-8 2.0, ($8000) I think I instead have another strong recommendation for you to consider: 

Buchardt Audio S400 Mark II speakers ($2100), (amazing speakers, good for near wall) and 

Buchardt Audio I150 all-in-one integrated amplifier ($2000) minus $500 if bought with the speakers.  Check out the specifications and great reviews.

Buchardt will ship you the components to try out for 4 weeks.  100 bucks no hassle return. Then, for around $5k, some cables and possibly a sub or two, you might just be well on your way.  Good Luck!