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Need help understanding DIY subwoofer amplifier power requirements.
Hi first of all, I’m a novice on the topic willing to learn. I noticed that for diy subwoofer high-powered amplifiers are used. At high level analysis, My understanding or assumption is, to compensate the DSP applied (ie a -6 db at 90hz with a q of 1) lo flatten the frequency response at 75 db you would need more power to get to the original 81 db.
i.e. originally 81 db required 100w ( i know, very inefficient, its just hypothetically)
75db 100w -> 78db 200w -> 81db 400w
can some one confirm or deny or enlighten me?
thanks all
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This discussion was modified 3 weeks, 4 days ago by
Juan.
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This discussion was modified 3 weeks, 4 days ago by
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3 Replies
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I think you meant 75->78->81. No biggie.
Generally, a 3 dB sound level change, positive or negative, is a factor of 2 X’s the power. So +3 dB is 2 x the reference level, and -3 dB is 1/2 x the reference level.
JL Audio has a good page on it here: https://jlaudio.zendesk.com/hc/en-us/articles/217201737-Doubling-Power-vs-Doubling-Output
jlaudio.zendesk.com
Doubling Power vs. Doubling Output
A common misunderstanding when it comes to audio is that doubling power (watts) will make it sound “twice as loud.” Doubling the power (or cutting it in half) actually provides very subtle changes...
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Thanks for the correction. I overlooked my post.
so in this regard you are confirming my assumption? This would be the reason for high powered amps?
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@Juan The page @TVOR-Ceasar linked is all the answer you will need
tldr
+3db acoustic power is 2x electrical power
+6db acoustic power is 4x electrcial power
+10db acoustic power is 10x electrical powerTo answer the reason why high power amplifiers are used for subwoofers, the lower a frequency the larger the driver needed to reproduce that frequency cleanly at high SPL. Larger drivers have more mass and therefore a higher voltage is required to move the speaker driver to achive a target SPL vs a smaller driver. Higher volatages need higher power rated amplfiers with larger capacitor banks to safely handle the transiet loading of low frequency content. In my pro audio background I often see high frequency compression drivers running around 10-15V under high SPL usage whilst 18″ subs can be hitting 80V on the amplifiers ouput side.
Its not just in the DIY audio side high power amplifiers are used for subwoofers it is simply a forced requirement of their intended use case
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