# Frequency Response??

Discussion in 'Speakers & Subwoofers' started by Jonny*D, May 22, 2005.

1. ### Jonny*D Agent

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Can't someone please explain. What does 70Hz-20kHZ+- 3dB mean

Would 60Hz-20kHZ+- 3dB be better?

2. ### FeisalK Screenwriter

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3dB is significant becasue it is the amount of volume/SPL that is noticeable. so, &plusmn;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

3. ### Dick Boneske Stunt Coordinator

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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.

4. ### Mike^S Stunt Coordinator

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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.

5. ### Wayne A. Pflughaupt Moderator Moderator

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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

6. ### Chris Quinn Screenwriter

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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.

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