11-Aug-2019, 14:27
@Confused,
Take a look at Stereophile's speaker test reports, especially the impedance and phase plots at low frequencies. There's huge variations there from speaker to speaker and that affects the load the speaker places on the amp with some speakers being easy to drive, others hard to drive. There's going to be variations in power draw from speaker to speaker and there's no way any calculator can take that into account unless you can enter that kind of data into the calculator also. I don't know of any calculator that lets you do that.
Then there's the room response. We both know that lots of speakers, including the Harbeths, roll off at lower frequencies. Room response is even more uneven at low frequencies than speaker response and we've got no idea what the room response was like. I was once told by a dealer that his best showroom started rolling off at 100 Hz because of openings to other areas. I was once in a showroom where I could not hear a prominent bass line from a speaker at the listening position the dealer had set up but that bass line became very audible and in balance with the rest of the music if I stood up and took one or two steps forward so we're talking about what was probably a measurable SPL difference in the room of 30 dB or possibly more in a space of less than 3 feet. Where was the mic placed for the video? Was it in a null position for the bass or in a pressure zone for the bass notes? If it was in a null, was the volume level set for a balanced sound somewhere around where the mic was in which case the amp would have to have been delivering a lot more power in order to deliver the level heard at the mic position but the level of the voices of people near the mic wouldn't have to have been anywhere near the output from the speakers at the speaker location because most of that output of the speaker would have been disappearing at the mic position because of the null. Add to those issues a pile of people in the room with their clothes adding to the absorption of the room furnishings/carpet/curtains etc and whatever acoustic treatments are present and the absorption they provide.
As I said in my response to @thumb5 above, the problem isn't with the calculator, it's with the data we enter and the data we've got for entry is very limited. I have no idea what the acoustics of the room were like but I do know from experience that you can pour huge amounts of power into trying to get decent listening levels in one position in a room and much less power into getting similar results in another position. The calculator makes limited provision for speaker placement but that's a rough estimate which won't be accurate for every room, and no provision apart from for listening distance for room effects at the listening position. Most of us, probably nearly all of us, don't have that sort of data for our rooms and I hate to think what the calculator would look like if it allowed us to enter that sort of information.
I think the calculator is quite accurate for the sort of input data it uses but I can also envisage situations in which the 40 watts you calculated for a 95 dB level at a given distance could easily end up actually being an order of magnitude higher depending on whether or not the listening position was in a null for the bass frequencies and the listener was adjusting the volume level to compensate for the null, especially with a speaker that was difficult to drive.
It would be great if someone came up with a calculator that took more things into account. Then we'd find people complaining that the calculator was useless because they couldn't provide all of the data it asked for. There's no perfect solution here, and there's no way of avoiding the sort of difference in result shown by your video example and the situation in my room with the sort of calculator that we can find online. If we want anything more than that, then we're probably going to have to look for something that starts out with a professional level room analysis tool, speaker measurement tool, and a amplifier measurement tool which measures amplifier performance to a greater degree than even the Stereophile test reports do and they're more detailed than any other reports I've seen that are generally available. If we had that then we'd see a pile of complaints that the damn thing was too complex for anyone to use.
We've got what we've got, it's better than nothing, and it works better in some situations than it does in others. In the end, if you can't get the levels you want in your room with an amp of a certain size then you need a bigger amp or more sensitive speakers. The only simple and reliable test available for any one of us is to grab an amp and speaker combination, stick them in our room, and see whether we're happy with the result. The best the calculators we've got can do is give us an idea of what a starting point for amplifier power and speaker sensitivity should be. Sometimes, probably a lot of the time, that starting point will work but sometimes it won't.
Take a look at Stereophile's speaker test reports, especially the impedance and phase plots at low frequencies. There's huge variations there from speaker to speaker and that affects the load the speaker places on the amp with some speakers being easy to drive, others hard to drive. There's going to be variations in power draw from speaker to speaker and there's no way any calculator can take that into account unless you can enter that kind of data into the calculator also. I don't know of any calculator that lets you do that.
Then there's the room response. We both know that lots of speakers, including the Harbeths, roll off at lower frequencies. Room response is even more uneven at low frequencies than speaker response and we've got no idea what the room response was like. I was once told by a dealer that his best showroom started rolling off at 100 Hz because of openings to other areas. I was once in a showroom where I could not hear a prominent bass line from a speaker at the listening position the dealer had set up but that bass line became very audible and in balance with the rest of the music if I stood up and took one or two steps forward so we're talking about what was probably a measurable SPL difference in the room of 30 dB or possibly more in a space of less than 3 feet. Where was the mic placed for the video? Was it in a null position for the bass or in a pressure zone for the bass notes? If it was in a null, was the volume level set for a balanced sound somewhere around where the mic was in which case the amp would have to have been delivering a lot more power in order to deliver the level heard at the mic position but the level of the voices of people near the mic wouldn't have to have been anywhere near the output from the speakers at the speaker location because most of that output of the speaker would have been disappearing at the mic position because of the null. Add to those issues a pile of people in the room with their clothes adding to the absorption of the room furnishings/carpet/curtains etc and whatever acoustic treatments are present and the absorption they provide.
As I said in my response to @thumb5 above, the problem isn't with the calculator, it's with the data we enter and the data we've got for entry is very limited. I have no idea what the acoustics of the room were like but I do know from experience that you can pour huge amounts of power into trying to get decent listening levels in one position in a room and much less power into getting similar results in another position. The calculator makes limited provision for speaker placement but that's a rough estimate which won't be accurate for every room, and no provision apart from for listening distance for room effects at the listening position. Most of us, probably nearly all of us, don't have that sort of data for our rooms and I hate to think what the calculator would look like if it allowed us to enter that sort of information.
I think the calculator is quite accurate for the sort of input data it uses but I can also envisage situations in which the 40 watts you calculated for a 95 dB level at a given distance could easily end up actually being an order of magnitude higher depending on whether or not the listening position was in a null for the bass frequencies and the listener was adjusting the volume level to compensate for the null, especially with a speaker that was difficult to drive.
It would be great if someone came up with a calculator that took more things into account. Then we'd find people complaining that the calculator was useless because they couldn't provide all of the data it asked for. There's no perfect solution here, and there's no way of avoiding the sort of difference in result shown by your video example and the situation in my room with the sort of calculator that we can find online. If we want anything more than that, then we're probably going to have to look for something that starts out with a professional level room analysis tool, speaker measurement tool, and a amplifier measurement tool which measures amplifier performance to a greater degree than even the Stereophile test reports do and they're more detailed than any other reports I've seen that are generally available. If we had that then we'd see a pile of complaints that the damn thing was too complex for anyone to use.
We've got what we've got, it's better than nothing, and it works better in some situations than it does in others. In the end, if you can't get the levels you want in your room with an amp of a certain size then you need a bigger amp or more sensitive speakers. The only simple and reliable test available for any one of us is to grab an amp and speaker combination, stick them in our room, and see whether we're happy with the result. The best the calculators we've got can do is give us an idea of what a starting point for amplifier power and speaker sensitivity should be. Sometimes, probably a lot of the time, that starting point will work but sometimes it won't.
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
