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Discussion in 'Amps and Cabs [BG]' started by bizzaro, Jun 22, 2001.
100 db?? Is this a good spec for a speaker.
100 db is fine.
Mine are 96 db.
120 db is perfection, in theory.
It's all about the tone.
What does it mean?? What kind of a measurment is it and how do you compare speaker to speaker db to db?
It's a measure of efficiency: the higher the number, the more acoustic output. To compare the numbers between different speakers, you have to be sure they're all referenced to the same standard, otherwise comparisons are impossible. The most common standard I've seen is XXX dB for 1 W at 1 m. Some people use 2.83 volts instead of 1 W, but I understand this is only valid for 8 ohm cabs because at 4 ohms 2.83 V = 2 W, not 1 W.
My own bias is that it's easily possible to get way too hung up in worrying about efficiency numbers. Everything else being equal, it's great to have more efficiency, but on the other hand, what good is a very efficient speaker if it sounds bad? All you get then is a loud bad sound. IMO tone comes first, and efficiency comes after that. Ideally, you want both, but if you can only have one, go for tone. The reasoning is, if you have an inefficient but good-sounding speaker, you might be able to get the volume you want by obtaining more amp power; but if you have an efficient but bad-sounding speaker, you very likely won't be able to make it sound good no matter what you do.
In most cases it is a measurement of the amount of sound a speaker puts out measured 1 meter away from the speaker with 1 Watt going into the speaker. This is measured with a Sound Pressure Level meter. You can buy one at Radio Shack if you want.
from my handbook-
80 dB is "loud", like normal street noise, electric shaver, alarm clock...
90 dB is "very loud", like noisy factory, truck without muffler.
100dB is like lawn mower, car horn at 5 meters, wood saw
130dB, threshold of pain
140dB, jet engine, artillery fire.
I heard somewhere that 150 dB is capable of stopping the human heart. Is this true?
Yep. 150 dB will kill you. It's an increase of 20 dB over the pain barrier. A rise of 20 dB means 100 times the amplifier power, and sounds 4 times as loud. We're talking about 100,000 watt here (or to that extend)
By the way, Donne Demarest, perfection would be 112.1 dB, not 120 dB. 1 watt of electrical power converted to sound with 100% efficiency results in 112.1 dB.
Remind me to come back here and straighten out some of this stuff when I'm not so tired.
A loud bar venue runs between 100 and 106 dB(A) at the audience distance from the band. I take a dB meter with me on every gig.
A bass cabinet rated at 100 dB that generates 106 db at 8 meters with a 250 watt amp will be generating 124 dB on stage. Time for earplugs.
I looked up the numbers, and you are correct.
Dyslexia struck again.
I'm back. Efficiency and sensitivity are *not* the same thing. If they were, then the latter would not be required nomenclature. The difference has a lot to do with the directivity of the cabinet. In an extreme case - a horn emitting very high frequencies - you can have extremely high sensitivity, but the overall efficiency could be poor because all the power is beamed to a confined area.
See my March 3 post on this topic at http://www.talkbass.com/forum/showthread.php?postid=129510&highlight=Speaker+Efficiency#post129510.
The determination of loudness vs. distance also depends on directivity and the shape of the wavefront. A spherical wavefront's attenuation with distance differs from cylindrical, which differs from planar, etc. This means that one simple function cannot apply to all acoustic settings.
- Mike (the acoustics nerd)