Axiom Home Page Forums General Discussion Advice from Axiom Owners Room Size versus Listening Distance

In several posts recently, would-be Axiom buyers have asked the age-old question... "Which speakers do I need for my room size?"

Responses always correlate big rooms with the need for big tower speakers. However, less often, we ask users how far away they sit from their speakers. I can understand why room size is a driving factor for the size and number of subwoofers needed (to move all of the air in a big room), but for main speakers, isn't listening distance more important than room size?

Example: I have a 8000 cubic foot room (hypothetical) but that room is made up of a living room, dining room, kitchen, and open balcony to the second floor (i.e. really high ceilings). Despite how huge this room is, only a small portion of the room is dedicated to my listening area (one couch 6' away from a medium-sized TV). Given the room arrangement, we have only one listening position from which we listen to music or watch movies.

In this scenario, does the rule that "bigger room requires M60s or M80s" apply? (I realize if money is no object we'd all want 80s, but I'm wondering if the decision on speaker size for the mains is actually driven by room size or listening position)

Again, on the subs, clearly here you'd still benefit from more bigger subbage to pressurize the room and move air around, but does the same hold true for the mains? If so, why?

Thanks,

Jason

I suspect you have a good point, Jason, but as I'm running M80s in a 19x20 room, 8 feet away from them, I don't really know the answer.

M80's in a 2150 cf room here (it is pretty open to a kitchen about half that size though.)

I think my speakers sound GREAT in my relatively small room. I probably could have got by with less, but why settle for anything but the best?

I'm a big believer that listening distance matters most for everything but the sub. It gets tricky to discuss though, since in a smaller room there is a credible view that at a relatively short distance the accumulated reflections become the dominant factor and that distance becomes irrelevant.

The point is, I think, that in a large room at short distances the reflections are not as big a factor (since the walls are simply further away) so that the straight-line distance to the speaker is the primary determinant of how much energy the speaker needs to kick out to give you the desired SPL. The key issue is how much air the speaker can move, I think, more than the actual size of the speakers -- for example the M40s in my living room (4200 ft3, opening into another ~8000 ft3) sound wonderful but I wouldn't want to try and "rock the house" with them since they only have a single small woofer and tweeter.

All I can add is that in Mojo's 4000cf room, my M22s always sound thin, in my 2500cf room they sound very nice and full. I know room treatments and even just the furniture can add to or reduce the sound, but I still think the room size does have an affect on the sound from small speakers, as they still have to move air to give them nice bass.

Yeah, I don't know what the exact effect is -- it may be as simple as smaller speakers only being able to play cleanly at lower volumes where the ear tends to roll off the perceived bass and treble (the old Fletcher-Munson loudness compensation curves). The M40s seem to be able to play loud enough to sound full (and they kick out a surprising amount of deep bass) but I don't think they have a lot of headroom to spare.

Interesting. I don't tend to sit in one place to listen to music. The M3 with sub would probably have filled my 1800cf room nicely, but then I wouldn't be able to rock to SRV while cooking.

I guess I assume that people do other things while they listen to music the way I do. The M80 does just fine when your listening from 6' away. The M22 would strain when you are 15' away in your 8000cf room.

Exactly. If you are in the kitchen and your speakers are in another room then you have a large listening area

Click. Click click click click. 3000cf. Hey, I'm a perfect candidate for the M80! Its funny that I never considered this when I bought the M80s.

I suppose there are advantages to buying a smaller speaker if you want to localize the sound a little.

Jason, the question of how loudly a speaker has to play in a certain situation(and the related question of how much power is needed at the time)depends on both room size and reverberation time and listener distance. A key concept in this is the "critical distance" of the room, which is the distance at which the sound level reaching the listener directly is equal to the sound level reaching him from room reflections, i.e., with both equal, the total sound is 3dB higher for the listener. A simplified discussion of this is found here , with the formula for calculating the critical distance(in meters)with a certain room volume and reverberation time(typically about .5 second at mid frequencies for home listening rooms). Linkwitz has a more complex discussion here in sections C3 and C5 to similar effect. The net result of this is that in typical home listening rooms the critical distance isn't far from the standard 1 meter distance for speaker sensitivity ratings, resulting in an "in room" number about 3dB higher.

Beyond the critical distance the contribution from the room reflections remains relatively constant at home distances and the overall sound level falls much less than the 6dB per doubling of distance that the direct sound theoretically falls. This is the reason that some of the power calculators available online are quite inaccurate, since they use the 6dB loss figure. Dr. Toole makes a similar point in his new book which was the subject of a thread here a couple months ago and which I'm reading now. At pp. 44-48, he discusses with illustrations the fact that sound level drops much less with distance in listening rooms when the room gain is taken into account.

So, the bottom line is that the calculations can get quite complex when all the factors are entered, but the requirement for speaker loudness level(and required input power)is less affected by both listener distance and room size than is sometimes imagined.