So... since they quote the same maximum peak SPL, what can I conclude from that?
That below a certain price
point, it's Whose
Line Is It Anyway -- everything's made up and the points don't matter.
Since you're linking to powered speakers, let's look at the QSC K-series, one of my favorite powered
speaker lines on the market. Notice that they put the same 1000W
amplifier in each and every
speaker, even the sub. This is for economies of scale in manufacturing more than anything else. They can market their 8" cabinet as a 1000W
speaker, but that's more of a
reflection of the
amplifier than it is the
driver element. As stated before, even on
passive speakers the wattage ratings are misleading because they don't take into account efficiency, but active speakers really make wattages completely meaningless.
In contrast, depending on how you choose to look at it,
here's a 700W speaker that puts out 145dB.
So what, pray tell, does a better
speaker get you?
A larger
driver element with extended low-end response and better
pattern control. It also gets you a couple extra dB of
headroom, which most people will never notice with a
meter. What they will notice with their ear is that with a smaller
speaker, they cannot "feel" the sound like they would instinctively expect to and may perceive that as a quieter
speaker, which then they drive into
clipping and
distortion trying to feel the low-end that that size of
speaker cannot possibly produce.
When I recommend the K-series to someone, I usually go for the K10 or K12, not because of SPL, but because of
pattern control. The K8 is better for a small, crowded room where the speakers are immediately in front of a crowd and taking advantage of the 105° conical
pattern. Any larger rooms benefit more from a K12 because it keeps the sound on the audience and off of the walls and ceiling.
Shifting gears a little
bit, let's talk about SPL over a distance.
An ideal
line source attenuates at -3dB per doubling of distance from the
speaker. If you are 60' away and hearing 100dB, then in an ideal laboratory environment, the speakers within an
array couple together to produce a wavefront that at 120' would be apprx 97dB. At 240', 94dB.
An ideal
point source attenuates at -6dB per doubling of distance. That means at 120', you would hear 94dB. At 240', 88dB.
Traffic is a good example of a line source. The reason highways are particularly obnoxious to residents nearby is because once you get enough cars on the
road, the nature of the noise source behaves more like a
line source and the noise carries farther. Not because it's all that much louder, but because the noise from each of the vehicles is coupling together as they scurry down the roadway. So at midnight or noon, traffic behaves more like a
point source and attenuates to a much quieter
level to the neighborhoods next to the highway. At rush hour though, it acts like a
line source and in an ideal environment attenuates apprx half as much as at lunchtime. The noise carries
much farther and is much more of a nuisance.
What does this all mean?
SPL matters in larger environments much more than in smaller. The
intensity of the noise source will vary significantly near the
speaker, no matter what. In a small room, a difference of 3-6dB is generally insignificant, though it will be audible. However, as the noise propagates away from the
speaker, that 3-6dB can have consequences for a larger group of people. If we have a
point source and take the chunk of space between 60' and 120' and say it has mean SPL of 85dB, that's quite a
bit of audience space that falls into a 6dB window, between 82-88dB. You may be incinerating the people sitting directly in front of the
speaker, but at this 60-120' distance, you have what would be considered an acceptable amount of drop-off between the first row and the back.
On the other
hand, if we stick that 6dB window at 85dB between 10' and 20' away from the
speaker, well now it doesn't really matter what you do. Unless you're holding your performance in a shoe box, someone in the front row is either getting incinerated or someone in the back can't hear. This is because if we have 88dB at 10' with a
point source, we have 82dB at 20', and 76dB at 40'. If the first row is at 10' and the last row is at 40', it will be perceived as literally half as loud in the back row as in the first row. (Human perception is 10dB = twice as loud)
Put all of this together, and if you're buying a
system for a rock and
roll show in a stadium, you want a
line array so your sound makes it across the field, and the farther you get away from your
stage, that extra 3 or 6dB between one
speaker model and another begins to really,
really matter because at a distance it affects a much greater footprint of the field and of the bleachers.
This is the long way of saying that for a smaller environment, there any number of factors that take precedence over pure loudness.
Distortion,
pattern control,
headroom before
clipping, low-end response and whether you can feel the <80Hz content, how the
speaker is aimed within the room, how much distance is between the
speaker and the first row, how distance is between the first row and the last row, if the
system is tuned and delayed properly or used with out-of-the-box settings, how good the
speaker sounds in a
blind demo compared to the runner up, and of course -- the quality of the signal chain and the microphones. A $1,000,000 PA still sounds like a bad car stereo if you put $35 generic
headset mic's in front of it or if the faders on your
mixer are all dusty and crackle whenever you move them.
Okay, not quite, but the without knowing how a given published specification has been arrived at, there is a semi-deliberate obfuscation of physics.
