Speaker sensitivity?

gshisme

I have read that for every 3 dB difference in speaker sensitivity the required power to drive the speakers either halves or doubles. Is that to say to power a LSi9 which has a rating of 88 sensitivity would require 100 watts to equal the sound level of a CSi40 which has a rating of 91 at 50 watts. I think I am confusing myself because this just doesn't sound right. I realize there is an impedance difference between these two speakers. Does that factor in. I used these two speakers just for comparison purposes.

Greg

rs159

If you have a good amp, then halving the ohms should roughly double your power. If you don't have a good amp then it will probably get really hot and go up in smoke. You're right about the dBs, e.g. 60dB + 60dB = 63dB, not 120dB.

TonyPTX

Originally posted by gshisme
Is that to say to power a LSi9 which has a rating of 88 sensitivity would require 100 watts to equal the sound level of a CSi40 which has a rating of 91 at 50 watts.

Yes, this is a correct statement. For every 3dB in volume gain, the power needs to be doubled which is why it's important to get a speaker with decent efficiency.

gshisme

OK so why the difference in sensitivity between speakers. There seems to be no correlation between low/high sensitivity and good/bad speakers.

edit

RuSsMaN

Since when does the Csi40 hit 91db at FIFTY watts? Do you mean 1 watt (in the chamber)?

Cheers,
Rooster

gshisme

RuSsMaN,

I'll put it another way:

If I listen to the CSi40 at a volume setting of say -25 with a 50watt per amp, would I need a 100watt per amp to drive the LSi9 at the same listening level of -25?

rs159

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TonyPTX

Originally posted by gshisme
OK so why the difference in sensitivity between speakers. There seems to be no correlation between low/high sensitivity and good/bad speakers.

Why does my truck only get 18 MPG as opposed to some other car who may get 25 MPG? They both run on gasoline and have internal combustion engines right?

Seriously though, all things considered (number of windings on a voice coil, cone material, tweeter material, cone displacement, housing tolerances, x-over efficiency), it's just the small differences in a speaker that make some more efficient than others. You also have to realize that you're talking about SOUND level which is on a LOG scale as opposed to power which is just a squared function. Sometimes things just don't seem right but they are.

As for the correlation between good and bad speakers, anything at or around 89 dB/1 W/1 meter is acceptable. Cheap speakers don't come close to this and those that do sound horrible due to corner cutting from the above mentioned considered options that help prevent distortion and extra noise from being introduced into the reproduction of a sound.

gidrah

Yes! You are correct. I also think there would be additional math in your example, in that the LSi are 4ohm and the CSi are 8ohm. Now the 2X wattage is roughly X2 again.

Mismatching amps can be a very good thing!

burdette

Originally posted by TonyPTX


Why does my truck only get 18 MPG as opposed to some other car who may get 25 MPG? They both run on gasoline and have internal combustion engines right?

As for the correlation between good and bad speakers, anything at or around 89 dB/1 W/1 meter is acceptable. Cheap speakers don't come close to this and those that do sound horrible due to corner cutting from the above mentioned considered options that help prevent distortion and extra noise from being introduced into the reproduction of a sound.

I don't agree with that summary at all. I don't think you can tell *anything* about a speaker - good or bad - from the sensitivity value. You can buy very expensive speakers that have sensitivities in the low/mid 80s.. and you can buy great speakers that are well into the 90s... and you can buy **** just about anywhere in there, as well.

I thought of the same example you used.. miles per gallon.. but the second part of your comment is like saying all cars that get high mileage are better at cornering than cars with low MPG.