Earl,
Sorry I didn't catch the scale on your plot you showed. Thought I was looking at 50hz when it was 500. When you say that all 15" speakers have the dip from the surround is that only with an M-roll surround or do you see the same dip with a 1/2 round surround also?
Sorry I didn't catch the scale on your plot you showed. Thought I was looking at 50hz when it was 500. When you say that all 15" speakers have the dip from the surround is that only with an M-roll surround or do you see the same dip with a 1/2 round surround also?
Pano, good that you did this test. I have followed the discussion about the claim that frequencies below 700 Hz are not an important source of localization with a mix of amazement and entertainment. Your test should refute it to the dustbin.
Let's look at the physics of the situation. A 700 Hz tone is just under half a meter long, the distance between a typical set of ears about 22 cm. It is easy to see how a sound source that is even slightly off axis will produce significant phase shifts in the sound entering both ears.
Let's look at the physics of the situation. A 700 Hz tone is just under half a meter long, the distance between a typical set of ears about 22 cm. It is easy to see how a sound source that is even slightly off axis will produce significant phase shifts in the sound entering both ears.
There is also a subtlety to the >700 Hz claim. Does it also mean that reflections from < 700 Hz are not detrimental to localization? Pano wasn't able to localize easily when the two bands were panned to different speakers.
A key aspect of reflections that is often misunderstood: is it correct to assume that a reflection of a 500 Hz wave is heard as 500 Hz? Not likely. Here's a post by speaker dave that speaks about it:
http://www.diyaudio.com/forums/mult...-covers-common-discussions-2.html#post2759273
He says, "We talk about reflections as if they are heard in issolation and have a particular frequency spectrum that is important. The reality is they combine in a particular way with the direct response based on their delay (and perceived based on direction and the ears inherent time windowing). So a flat spectrum reflection will combine with the direct sound for a very comb filtered response. The major deviation is around the first or second comb filter nulls. I have listening simulations and there are always major pitch effect determined by the particular delay. Flat plus flat does not equal flat.
At higher frequencies the comb filtering is dense, within a critical bandwidth, and the reflections add brightness."
Given all these points, how can we disregard reflections of (or directivity for) sounds < 700 Hz?
A key aspect of reflections that is often misunderstood: is it correct to assume that a reflection of a 500 Hz wave is heard as 500 Hz? Not likely. Here's a post by speaker dave that speaks about it:
http://www.diyaudio.com/forums/mult...-covers-common-discussions-2.html#post2759273
He says, "We talk about reflections as if they are heard in issolation and have a particular frequency spectrum that is important. The reality is they combine in a particular way with the direct response based on their delay (and perceived based on direction and the ears inherent time windowing). So a flat spectrum reflection will combine with the direct sound for a very comb filtered response. The major deviation is around the first or second comb filter nulls. I have listening simulations and there are always major pitch effect determined by the particular delay. Flat plus flat does not equal flat.
At higher frequencies the comb filtering is dense, within a critical bandwidth, and the reflections add brightness."
Given all these points, how can we disregard reflections of (or directivity for) sounds < 700 Hz?
Yes, quite right. I hope to do further tests and have some other people double check them. It's easy to make mistakes.
FWIW, we did make some mistakes in the test, E.G, I could not hear the bass moving when panned L-R. We then discovered that it was routed wrong on the console and was not panning at all. No wonder it didn't seem to move. 🙁
I'll repeat the test as time allows and with input from the forum welcome. I'm tempted to try moving the image via delay, as well as via amplitude.
Pano,
I had hoped that you would make your experiment along the claims of David Griesinger. Two examples regarding the 700 Hz "threshold":
Rudolf
I had hoped that you would make your experiment along the claims of David Griesinger. Two examples regarding the 700 Hz "threshold":
Bold highlights are from me to show why noise doesn't cut it as a proof.
Rudolf
Why? In what way? He does not say, as far as I can see, that the sounds have to be vocal for location. Just in the vocal formant range. I don't think many people have trouble locating non-vocal sounds. Do the sounds have to have harmonic coherence? Certainly noise does not.
Anyway, it will be interesting to try it with vocal and other musical sounds. Even with spoken word.
Later in time yes but certainly not lower in level. Do I need to post an ETC? I think I already did that some time ago...
That sub looks from the pictures to have vents - might they have been generating duct noise?
Seriously? I simply look at available data.
Keele's CBT looks very good. It's easy to absorb the side wall reflection if desired. They have high vertical directivity which eliminates the need for ceiling and floor absorption. Overall directivity is very well behaved. Not a "christmas tree" like most constant directivity designs.
Yes, some noise when we really got them going. Turned down a bit no audible noise but plenty of air! Meyer subs are very, very well made. They should be, for the price. Rattling stuff on the warehouse shelves was more of a problem.
They are good speakers. I've not heard the CBT and Gedlee speakers side by side, but I'd put money on the chance that I'd prefer the Abbey in a blind test. You can only tell so much from plots.
I think that once Keele goes with better drivers, the CBT will be a real contender.
According to Griesinger vertical reflections are not an issue. Our hearing ignores them.
Please look at the Griesinger sources that had been linked. All claims of Griesinger apply only to fundamentals with their harmonics. It is the essence of it all. Harmonics would not be harmonics if they were not strictly coherent with their fundamental tone. Noise is almost the complete opposite of this.
Rudolf
That's not the "physics of the situation". Greisinger posts ILD's and ITDs for the head somewhere on his site (no I don't have the link!). These functions get vanishing small below 700 Hz. Nothing at all compared to > 700 Hz. That IS the physics.
Rudolf - do you see the Greisinger papers as significant as I do? You certainly seem to understand them in the exact same way that I do.
Couple the Griesinger papers with the paper that you posted on resolution of amplitude modulations in the ear and one begins to see how potent the Greisinger hypothesis could be. The two papers together present a very convincing picture of some very difficult stuff to understand.
The other hand-waving going on here is not convincing at all. (Pano's results excluded, except that I agree that they need to be done with harmonic tones not noise.)
Do you think that noise is easier to locate? I do find it much easier than pure tone, no doubt. I'll try it with music and speech a report what we find.
If anyone has other types of signals to try, I'm open to them.