[Ultralight]

I've noticed that smaller speakers (or is it the smaller drivers?) sound more spacious in my 12x13 feet office.  I do pull speakers at least 3 feet away from the walls. 

Why is that? Is it the smaller body along wound to wrap around backwards for more dispersion?  Is it the smaller drivers that has wider dispersion?  Something else?  Is there no way to get this with larger speakers in a small room?

Thank in advance for any insight.

[richidoo]

I think you're right about dispersion. Controlled dispersion aka even power response is said to be the primary determinant of our perception of SQ. Floyd Toole acoustic and speaker expert has talked and written about this, check youtube.

The illusion of stereo spaciousness in a reflective room comes mostly from first reflections on sidewalls, and some front wall. Maybe the midrange/tweeter reflection spots on the side walls have different reflectivities for the small and large speakers due to different driver heights or speaker position.

Also could be that the small speaker does not excite bass modes as much as a larger speaker would in your small room. Room bass modes can reduce clarity of midrange, and is annoying by itself. But even small speakers with ports get down to 50hz, that's low enough to stir up the mud, so I don't think that's the main problem, but could be contributing.

Small rooms in general tend to have less illusion of space because the reflections come too soon. Hard to avoid that "listening in a room" feeling. My stereo room is the main family room, largest room in the house. I would love to relieve the family burden of the main room of the house filled with hifi equipment, but every other room in the house is too small and doesn't sound as good.

[S Clark]

And small baffles image better than larger ones.  If the instrument placement is to the sides, it can create a more real sense of space outside the speakers. 

[joerest]

Small speakers have less of an impact on the room environment, therefore facilitating less acoustical changes to the room (especially small rooms). For a small room, get used to nearfield listening.


Joe

[Armaegis]

If you're sitting close, the smaller speakers may also be more coherent as the sounds from the separate drivers will have "merged". Larger drivers (and thus larger speakers) need more distance from them before they sound cohesive.

[JLM]

Small room inherently necessitate near-field listening to avoid smearing of direct vs. reflected sound.  Smearing is avoided when the added travel distance of reflections exceed the direct travel path by at least 11 feet or adding highly effective treatments.  You're probably confusing smearing with spaciousness.

Smaller rooms excite fewer room modes that are spaced further apart (as measured by frequency) which end up being more noticeable and with the limited space available be harder to treat.  This affect is based on the room size, not speaker/driver size.  Ideal shapes spread out the frequencies where mode occur more uniformly (not coinciding) so that there is a uniform boost in room reinforcement.

Baffle width simply affects the frequency at which baffle step (transition from full to half space) occurs (and frequency response increases by 3 dB).  Again, this is based on the laws of physics, sound waves are 13,200 (speed of sound in air measured in inches per second) divided by the frequency (cycles per second) long in inches.  Example: a 5 inch half width of front baffle would 'step up' (increase sound pressure levels starting at 260 Hz (13,200/5).  Agree with Armaegis regarding coherency of small speakers, this could explain the better imaging as wide baffle speakers tend to use larger/farther apart mounted drivers.

In order to control dispersion driver sizes must match both crossover frequencies and size of sound waves being created by the individual drivers.  Most speakers don't. 

[planet10]

Smaller rooms excite fewer room modes that are spaced further apart (as measured by frequency)

Smaller rooms don’t have fewer modes they just occur higher in frequency. Because the wavelengths are shorter they are closer together (at least on a linear scale).

dave

[JLM]

Smaller rooms don’t have fewer modes they just occur higher in frequency. Because the wavelengths are shorter they are closer together (at least on a linear scale).

dave

Sorry Dave, but I disagree (it's counter intuitive I know).  Yes they start to occur somewhat higher in frequency simply due to limiting room size (in Ultralight's case 85Hz based on dividing the greatest room dimension of 13ft into the speed of sound of 1100 ft/second).  The other modes will start at 92Hz (based on the stated 12ft dimension) and 138Hz (based on an assumed 8ft ceiling height).  Other modes are in multiples of each of these.  So the beginning modes in this case start at 85, 92, 138, 169, 184, 253, 275, 276, 338, 368, etc. (10 total below 400Hz).

In a larger 12ft x 19ft x 31ft room the modes start at 35, 58, 71, 92, 106, 116, 138, 141, 174, 177, 213, 232, 248, 275, 284, 289, 319, 347, 355, 367, 390, etc. (19 total below 400Hz).  So this larger room has nearly twice the number of modes below 400Hz as the smaller room.  Fewer modes in the smaller room means a more noticeable room affect (unnatural reinforcement of those frequencies, versus a more uniform reinforcement that occurs in the larger room). 

As frequency increases the modes get closer together and the whole mode concept becomes irrelevant. 

[poseidonsvoice]

Copied from a post I did eons ago on the Acoustics circle. I really enjoy this calculator:

Loads of fun, you can actually hear the room modes for your room (as long as your computer speakers can handle it), and also see which sets of modes are causing the most problems in your room

Also included are a 3D view of the modes, Bonello's (room modes per 3rd) and Bolt's area to help in choosing room dimensions.

Give it a try!

http://amroc.andymel.eu

Best,
Anand.