11-Aug-2019, 13:15
@thumb5 ,
I don't think the calculations are based on sine wave inputs. I think they're straight SPL calculations based on the number of watts the amp can deliver and the sensitivity rating of the speaker. The addition for multiple speakers assumes that each speaker is delivering the same SPL, the adjustment for listening distance is based on SPL falloff over distance, and the adjustment for speaker placement is a rough estimate of the support the room gives to a speaker placed in different positions. Ultimately the reliability of the result is going to depend on how the speaker sensitivity is measured, including the relevance of whatever is used for a test signal to situations involving music signals which could be quite different in frequency content, and the accuracy or otherwise of the sensitivity rating and amplifier output specification, both of which can often be wildly optimistic and owe more to marketing considerations than actual measurement. The calculator is simply basing its calculations on the data you enter and the usual GIGO rule (garbage in, garbage out) applies. I can't see anyone coming up with a better approach to the calculation method, anything more reliable is going to require more reliable data for input rather than a different approach to the calculation.
It definitely doesn't take Fletcher-Munson into account and it doesn't have to. What the Fletcher-Munson curves tell us is something about how frequency affects our perception of loudness. In music the level of the sound of different frequencies being played at the same time isn't uniform, the musicians adjust the level from their different instruments/voices to produce the sound balance they want the listener to hear. What the calculator calculates is what the SPL of that recorded sound balance is going to be at the listening position for a speaker of given sensitivity and a specified amplifier output. The relative levels of the different instruments/voices in the music will be preserved provided the speaker has a wide enough frequency response to produce all of the frequencies involved while preserving their relative levels accurately and the amplifier can deliver enough power to allow the speaker to do so.
I think it is quite useful in practice for the purpose for which it is intended. It's not perfect but the problems aren't problems with the calculator, they're problems with the accuracy of the speaker and amplifier specifications that are entered and the fact that music signals can be quite complex and there is no standard test signal that would be equally accurately represent every sort of music signal we send to our speakers. The things that would improve the accuracy of the result have nothing to do with what the calculator is doing and everything to do with the accuracy of the speaker and amplifier data we input.
I don't think the calculations are based on sine wave inputs. I think they're straight SPL calculations based on the number of watts the amp can deliver and the sensitivity rating of the speaker. The addition for multiple speakers assumes that each speaker is delivering the same SPL, the adjustment for listening distance is based on SPL falloff over distance, and the adjustment for speaker placement is a rough estimate of the support the room gives to a speaker placed in different positions. Ultimately the reliability of the result is going to depend on how the speaker sensitivity is measured, including the relevance of whatever is used for a test signal to situations involving music signals which could be quite different in frequency content, and the accuracy or otherwise of the sensitivity rating and amplifier output specification, both of which can often be wildly optimistic and owe more to marketing considerations than actual measurement. The calculator is simply basing its calculations on the data you enter and the usual GIGO rule (garbage in, garbage out) applies. I can't see anyone coming up with a better approach to the calculation method, anything more reliable is going to require more reliable data for input rather than a different approach to the calculation.
It definitely doesn't take Fletcher-Munson into account and it doesn't have to. What the Fletcher-Munson curves tell us is something about how frequency affects our perception of loudness. In music the level of the sound of different frequencies being played at the same time isn't uniform, the musicians adjust the level from their different instruments/voices to produce the sound balance they want the listener to hear. What the calculator calculates is what the SPL of that recorded sound balance is going to be at the listening position for a speaker of given sensitivity and a specified amplifier output. The relative levels of the different instruments/voices in the music will be preserved provided the speaker has a wide enough frequency response to produce all of the frequencies involved while preserving their relative levels accurately and the amplifier can deliver enough power to allow the speaker to do so.
I think it is quite useful in practice for the purpose for which it is intended. It's not perfect but the problems aren't problems with the calculator, they're problems with the accuracy of the speaker and amplifier specifications that are entered and the fact that music signals can be quite complex and there is no standard test signal that would be equally accurately represent every sort of music signal we send to our speakers. The things that would improve the accuracy of the result have nothing to do with what the calculator is doing and everything to do with the accuracy of the speaker and amplifier data we input.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, Keces P8 LPS, Uptone Audio EtherREGEN with optical fibre link to my router, Shunyata Alpha NR and Sigma NR power cables, Shunyata Sigma ethernet cables, Shunyata Alpha V2 speaker cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.
Brisbane, Qld, Australia
