Originally Posted by LTD02
i did not have a watt meter when i was a kid. i was taught math. 90db is a good start for AVERAGE SPL. however, onto that one must add allowances for dynamic range, which in well recorded music are 15db. then, if you are using the speakers to play kick drums, bass guitar or other instruments with a 60hz fundamental, then you must allow for another 10-12db for equal loudness curves (aka fletcher munson). on top off all that, one must allow for power compression, which for a REALLY good speaker is going to be another few db as it approaches rated power. then, since you are not typically sitting one meter from your speaker, you must add another 10db to account for distance losses. from this you get to subtract about 4db because you will typically have two speakers pseudo-coupling and you also get to subtract about 9db for boundary additions.
so the math is:
90db [average desired spl at the listening position]
+15db [peak to average]
+10db [equal loudness curves]
+3db [power compression]
+10db[listening at 10ft from speaker, not 3 feet]
-4db [addition from second speaker]
-9db [boundary additions]
115db this is the requirement at the _source_ in order to have undistorted music at 90db @ 60hz at the _listening position_.
most of the speakers in the triad line will fail to meet this objective. this does not make them bad speakers.
Good post. My original comment was a general one, but so is yours in a few instances. You can't add arbitrary elements together and derive a sum. There's no way to determine standard peaks for all music (some have peaks of 6 dB while some may have peaks of 30 dB or more), room reflections will vary at a set listening distance from room to room, power compression may be more or less, etc. You offer excellent elements to be considered, but half of them become estimates in the real world. And before we go further, I am in agreement with you.
The "average" SPL is generally a reference to the average on a frequency response curve; not when playing program material. The level is an average with a steady tone into the speaker. If the speaker is +/-2 dB within a range of 88 dB and 92 dB with one watt input, usually the sensitivity will be stated as 90 dB. I've never used an average dB standard on music, and although it would be interesting to see, I'm more concerned with the speaker handling peaks, which is presumably what you are pointing out with the 115 dB number.
Here is a great link from Crown which illustrates your point well, and it shows how inadequate most speakers are in reproducing high peaks without distress or compression. http://www.crownaudio.com/apps_htm/d...ct-pwr-req.htm
I've posted in other threads that in the majority of systems, peaks are compressed by the amp and the speaker and most listeners don't even realize it unless they've heard a speaker of high sensitivity, high power handling (you usually don't get both) and lots of amplifier power.
I think the key is using the appropriate speaker for the application, and powering it properly. I mentioned in a thread (you'll recall
) that my small-room, two-channel speakers are 86 dB, and I listen around 6' away at moderate levels with a 70 watt amp. I don't throw any Big Loud Music at them, and they work very well, within limitations. They are appropriate for this venue, but inappropriate for theater. My theater uses speakers that will handle double the power, and they're 92 dB with 375 watts per channel being used. I'll probably never listen at 110 dB again, so I'm within the parameters. I used to use a 94.5 dB speaker with a huge amp, and the dynamics were perceptively better at high levels, but they didn't do other things as well as what I'm using now, so these are better for my application.
I would be at a loss to come up with a brand name consumer loudspeaker that can play to high levels without compression. Most of the big names are 86 dB to 90 dB with modest power handling, and almost all would be taxed by having to hit high SPL in any venue. B&W, Paradigm, Ariel, James, Atlantic, Martin Logan, Kef? And at the same price point, JBL?
One of the balancing acts we're faced with in engineering at Triad is maintaining the highest sensitivity we can, and that means designing 4 ohm systems instead of 8 ohm speakers. In testing, a 4 ohm version will usually measure about 2 dB more sensitive than the same design using drivers that are 8 ohms (regardless of theory.) The problem is, although many newer receivers can drive 4 ohms, the manufacturers are specifying a 6 ohm minimum, which is overly conservative. What makes it tougher is, and I can't tell you why, drivers that are 96 dB and higher sensitivity seem to have other annoying sonic attributes, based upon our driver evaluations, unless they're expensive as hell. The Holy Grail would be a 107 dB sensitivity speaker that would handle 500 watt peaks, be fairly compact and affordable, and still sound good at low levels, too.
Thanks for bringing up some important points, one of the most important being distance loss, which is hugely ignored, and made worse by the fact that the higher the frequency, the more the loss over distance.