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Discussion in 'Speakers & Subwoofers' started by Jonny*D, May 22, 2005.
Can't someone please explain. What does 70Hz-20kHZ+- 3dB mean Would 60Hz-20kHZ+- 3dB be better?
3dB is significant becasue it is the amount of volume/SPL that is noticeable. so, ±3dB at 70Hz means the bass starts noticeably getting softer at 70Hz. If you are not using a subwoofer 60Hz is better, in fact floorstanders go all the way down to 40Hz or lower before rolling off. If you have a sub, a higher rolloff might mean that it is easier to integrate the sub and mains. YMMV of course
I believe the decibel scale was developed by Alexander Graham Bell. He picked 1 db as the minimum change in sound level that a human could detect. A +3 db change represents double the sound level. To illustrate this, if a sound is produced by a device at some level, and you add an identical sound source, the level change is 3 db. If you had four of these devices, the output would be 6 db louder. So, when a component is measured to be -3 db at some frequency, it is producing a change in sound level half of what it would be at 0 db. Humans can hear 20-20,000 Hz, so the closer to + and - 0 db a component is, the better.
I think when you add another source with the same volume and location, the overall spl increases by 6dB. Increasing the volume of a single source by 3dB requires double the power.
Jonny, Theoretically perfect response would be a flat line; for the sake of this situation let’s give the flat line a 0 dB reference. In the example you’ve given, it means response dips no more than 3 dB below the flat line, and rises no more than 3 dB above it, between 70 Hz-20 kHz. Make sense? Regards, Wayne A. Pflughaupt
A 3dB increase does not double the loudness. It take doubling the power to achieve a 3dB increase in volume. Here is a link to a sound ramp that decrease at 6dB per tone and then at 3dB per tone.