Dr. Floyd E. Toole has published a number of articles and AES papers related to this subject.
Among which:
"Subjective measurements of loudspeakers: A comparison of stereo and mono listening"
Among which:
"Subjective measurements of loudspeakers: A comparison of stereo and mono listening"
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Solo
performances. This is why a center channel is used in some systems. Also for uniform pans across a wide stage. WHG
performances. This is why a center channel is used in some systems. Also for uniform pans across a wide stage. WHG
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Some are suggesting that power response can be measured in room including reflections, at only the listening position. One example purpose is for comparing crossovers in the low kHz region.
May I have your opinion on the limits of the validity of this?
May I have your opinion on the limits of the validity of this?
If I measure the response at every point in a room then I have an exact calculation of the power response. If I measure this at a single point then there is an expected error of +6 dB to -11 dB. That is hardly good enough to rely on as a measure of the power response. As I add N more uncorrelated points to the average the error will go down as 1/N (linearly.) At some point I will get an answer that is "good enough." We found years ago that it took about 18 points to get a 1 dB error. Six gets you about 3 dB.
Earl, may I get your interpretation please. Floyd Toole said the following in 2019
Some are interpreting this to mean that diffraction is not important. How would you respond to that assertion?
How to Choose a Loudspeaker -- What the Science Shows | Page 90 | AVS ForumFloyd Toole said:
Some are interpreting this to mean that diffraction is not important. How would you respond to that assertion?
Diffraction is important, but when you look at the levels in comparison with other data, they will seem smaller.
I'm interested in seeing Earl's take, but I disagree with comments that it's not important (I don't visit that site, so haven't read them). To me it depends on two things, the first arrival impact and the power (room) response. If the on-axis is designed to be flat on-axis, the off-axis response may be problematic. The contribution to the off-axis responses will show up in the power response. My take on his comments is that they are with regard to room reflections. Those average out, but are best avoided, as he says. I don't interpret his comments to mean that it's not important.
Dave
Toole said "... in practice they often are not consequential audible problems."
That means only that it's possible that they're not be important.
This is a bit like saying: If the system is ****** enough, you're not going the hear the extra ******ness.
The audible distortion is basically covered with more distortion.
IMO, we have to move away from comments like this if we have high-fidelity and perfection in mind and not simply listening to music causally in the background somewhere random in the room.
Floyd's first sentence is certainly true, as is the second, but the second clearly refers to measurements not perception as the first one does. Hence this is not a claim of diffraction perception only that it is difficult to measure as the third sentence also implies. Although I am not 100% sure that everything will average out, none-the-less just because something is difficult to measure does not mean that it is inaudible. Anyone reading this who's take-away is that diffraction is not audible has clearly not read it carefully. Floyd is always careful about what he says that's one of the things I admire most about him. I wish that I were more careful sometimes.
I don't understand the question "measure at every point in a room" does not equate to "Mic axis angle random to speaker axis?"
Yes, and as Omholt say's what is an audible problem depends on what other problems exist and what one is looking for.
For example we know that wide directivity enhances spaciousness and will also tend to "cover up" early diffraction effects. But these two things also degrade imaging. So if the choice is audible diffraction or enhanced spaciousness but a degraded image then many will likely prefer the wide directivity and thus diffraction is not an issue anymore.
But if one wants to improve imaging by limiting the VER, then diffraction is likely going to be an issue in this case.
Think of diffraction as Very Very Early reflections. micro-seconds of delay, not milli-seconds as reflections are. This will mess up the brains ability to sort out image as these diffractions get fused into the direct sound - unlike room reflections which usually arrive late enough in time to be considered as distinct sound arrivals.
Thanks for your input, it is appreciated.
IMHO if some claim a preference for spaciousness without first having this experience, it may not be clear what this represents. Just one possibility, maybe early reflections can make a not so good speaker or implementation just a little more tolerable to listen to?
I am one that does not (a clean image is what I had always been looking for). In order to realise this it was necessary to take the advice here, and then to pursue designs where low diffraction and early room interaction was a primary goal. Then to use this knowledge to refine the design, integrate with the room and voice the speaker. I have confidence in this process as those that have also done it will know.
IMHO if some claim a preference for spaciousness without first having this experience, it may not be clear what this represents. Just one possibility, maybe early reflections can make a not so good speaker or implementation just a little more tolerable to listen to?
I share that opinion. Spaciousness, without first having achieved precise imaging, is a formula for pleasant mediocracy, ime/imo.
Comes from time blurring i think, ....and can come in several ways, which are all time related.
I think that, at least, the three of us agree.
And I agree that if someone has not experienced great imaging, which is very hard to do, then they don't really understand the attraction.
And I agree that if someone has not experienced great imaging, which is very hard to do, then they don't really understand the attraction.
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