How do you chose speakers based on room size?

Duke ;

Like the others ...your explanation has cleared up a lot of things that I have noticed along the way ! Thank you .

What I was trying to get at concerning the 'guidelines' were things to look for that were specific to the size of room that the speakers are to be used in , not an all in one approach .
What design characteristics would be favorable for speakers in a small room that would not be favorable for speakers that were to be used in a large room and visa/versa ?

Thank you .

"What design characteristics would be favorable for speakers in a small room that would not be favorable for speakers that were to be used in a large room and visa/versa?"

Well this depends somewhat on where the speakers are located within the room but in my opinion in a small room you generally want the bass rolloff to start fairly high but it can be gentle. This should synergize better with the anticipated boundary reinforcement than a speaker that is "flat" down to a fairly low frequency. Conversely, in a big room you need speakers with more bass output, relatively speaking, because the room isn't going to help you out as much.

In any size room I like fairly uniform radiation patterns in the midrange and treble region. In a small room I like a fairly narrow pattern that can be aimed to minimize early sidewall reflections, but there are people who like omnis in small rooms (the reflections from an omni are likely to be spectrally correct, which is desirable). I like to have at least a 7 millisecond delay before the onset of reflections other than the floor or ceiling bounce, and that corresponds to a path length difference of about 7 feet. So something like baby Maggies located 3.5 feet in front of the wall would probably be feasible (I'd prefer 5 feet out, but we're talking about the minimums here).

In a medium or large room where we'll have a good 10 milliseconds or more before the onset of reflections from nearby walls, we can freely use speakers that have a wider pattern (dipoles, bipoles and omnis conceptually fit into this category if they can be placed far enough out into the room)). Such speakers give a greater relative level of reverberant energy in the room and in my opinon more closely approximates the sort of soundfield we experience at a live performance. Now there are competing schools of thought that object to "adding" reverberant energy via wide-pattern speakers, but that's another topic for another day.

So to recap, you usually need a lot of bass output in a big room but not nearly as much in a small room, and (in Duke's opinion anyway) wide-pattern speakers are better suited for medium or large rooms than for small rooms.

"Duke, That explains alot and makes a good case for a midrange driver that covers as much frequency range as possible. "

Consistent also with my positive experience using OHM Walsh and Triangle 2-way monitor speakers in my small room, both of which cover a wide range through a single driver I believe. Similar expererience using my 2-way Dynaudio Contour line monitors as well.

Ideally, for coherent imaging and sound, you do not want different mid and high frequency ranges to be coming from different locations. Wide range drivers and drivers located closer together physically is what is needed to a greater extent to produce this ideal geometry when listening more nearfield in a smaller room, where the ears are capable of triangulating better on the exact source of sound.

From farther away in a large room, it is less of an issue.

Basically, in smaller rooms, the best things also happen to come quite often in smaller packages.

"In a small room I like a fairly narrow pattern that can be aimed to minimize early sidewall reflections"

Duke , is this why some speakers have the driver recessed from the front face of the speaker box and others put some type of built up ring around the driver if it is mounted on the face ? Or a narrow dispersion horn usage rather than a wide dispersion horn ? Would these perhaps be design features to look for if considering a small room speaker ?

And finally , what is your take on back loaded horns as suggested by J Bailey ? And speakers like the Altec 15 and 19 , used in small rooms in the Orient , where they are slammed up against the wall behind them but also used successfully away from the back wall in a larger room such as member 'T bone' does ?

Thank you .

""In a small room I like a fairly narrow pattern that can be aimed to minimize early sidewall reflections""

For me there are two viable approaches to fitting speakers into a particular room, large or small:

1) Do everything you can to isolate the speakers from room acoustics in order to hear just the recording and not the room

2) accept the room as your particular concert venue and utilize it

In the first case, more directional speakers or external tweaks that accomplish the same thing (see the isolated location of my Triangle monitors in my second system listing) are the solution, particularly in tight or limited quarters.

In the second case, omnis or other wide dispersion designs are the ticket.

Each sounds inherently different but both are viable approaches depending on the listener's goals.

I like and utilize both approaches in different rooms in my house, but, push come to shove, I tend to prefer the wide-dispersion approach.