Yes, so shouldn't that mean we should be careful about our reference axis?
But what does mean a reference axis for near field holographic measurement ? All axis are measured.
It means that the software is going to choose a given curve among others to display. I'm not sure that this curve is chosen by Amir. He would have to tell the x, y, z coordinates of the tweeter to the software. Is it the case ? If not, the Klippel is probably detecting the axis where the treble response is the strongest.
It is rather a good thing that all speakers are mesured equally. In doubt, we have to read the listening window curve instead of the on-axis curve.
The fact that the speaker was designed to have a best response in a different direction must be taken into account when we interpret the measurements.
I Don't know about the KH-80, but the KH-120 are more sensitive than the 305P to this. We can see below that the in-room curve of the JBL follows closely the anechoic curve, while the one the the Neumann KH-120 is somewhat different.
Both in-room curves were measured a bit above the tweeter's axis. The distance is 2 meters, and the top side of the speaker can just be seen from the listening position.
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Are people OK with the tail of the response being cut off this way? I can shift the directivity plots up so that is not a problem.
I prefer this vertical range.
What do you mean with the tail being cut off ? You mean the left part of the directivity indexes ? Can't we offset them so that they are displayed at a higher position ?
Can't tell if this was a joke, but from everything I've seen online, they are essentially the same barring aesthetic changes, For instance, the mkii appears to hiss as badly as any other iteration...
What about the difference in frequency response ? I thought that only the 305P mkII had the treble boost, and that the original LSR 305 was more neutral.
To illustrate the differences more clearly, here's the KH80's on-axis performance as measured by the Klippel, Neumann, Sound&Recording, and me (quasi anechoically), scaled to match aspet ratio. It kind of concerns me that the Klippel is the biggest outlier in terms of broad FR shape. We know the reference axis was a bit off, but I'd consider these differences of significant amplitude given the precision we're aiming for here.
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Thanks for the comparison.
Neumann's measurement should be discarded, as it is self-referent : the speaker was designed to sound flat according Neumann's measurements, therefore Neumann's curve is obviously flat.
But there is Indeed a difference between near-field direct measurements, as yours, and Klippel's holographic measurement. One explanation, given above, is that holographic measurement gives an accurate result, while direct near-field captation is an approximation. To confirm this, we need to understand the limitations of direct measurement, if they exist.
We might, if we get the chance, compare with other measurement methods. Half space might not settle the argument, as it is a bit inaccurate in this frequency range, where there is a transition between direct radiation and half-space radiation.
Ground plane (microphone against a concrete plane) might be interesting.
True free-field would be ideal, but it requires a lot of Equipment (a crane to lift the speaker far above the ground).
) but when the level gets higher like with top of the line studio monitors and/or your use EQ to correct little imperfections then hearable problems like IMD play a bigger roller than expected.
