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SPL technical Question

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Thomas Pennington
05/03/2020 1:50pm

If a speaker has an SPL of 100dB with 1 watt at 1 meter, what would the SPL be with the same speaker at 1/10th of a watt at 1 meter?
More specifically, if amp A has a built in attenuator that reads as down to -35dB reduction on its dial, and amp B has a built in attenuator that reads as reduced watts down to 1/10th of a watt on its dial, which amp will have the most volume reduction at full attenuation if all else is equal, as in the first sentence above?
Thanks.

Narcoleptigon_47048
05/06/2020 3:06am

2x the power = 3dB acoustic power increase. So...do the maths ;-)

Thomas Pennington
05/07/2020 11:08am

Thanks Narco for your comment. To the best of my ability, I come up with -18dB. That being said, I'll re-state my question. All I'm trying to do is buy a new amp that fits my specific needs. I'm an older retired guy. Don't want to drop a large amount of $$$ on the wrong amp. Would very much appreciate any comments that are constructive and helpful.

So here is the question... if amp A has a built in attenuator that reads as down to -35dB reduction on its dial, and amp B has a built in attenuator that reads as reduced watts down to 1/10th of a watt on its dial, which amp will have the most volume reduction at full attenuation if all else is equal?

Thanks all.

Narcoleptigon_47048
05/08/2020 10:23am

Going from say 100W to 10W is 1/10th the power. There's a 3dB acoustic level loss when reducing the power by 1/2. 100/2 = 50/2 = 25/2 = 12.5-2.5 = 10. 3 (x/2) at -3dB each = -9dB. That last 20% power reduction is another -1dB. 1/10th power = -10dB. -10dB is generally considered 1/2 the acoustic level, but some say -6dB is 1/2.