The Advantages of Floor Coupled Up-Firing Speakers

There is also a time factor involved. The longer the signal is on the better you can resolve its location. A short LF wavelet would not be localizable in any environment.

In a room I'd think it to be the other way around: the low-passed speech fragments Markus posted probably change in frequency too quickly as to not fully activate room-modes. On steady sine-waves I can't hear the direction up to a couple hundred hertz.
 
What would constitute a "wavelet"? Less than a full cycle at that frequency?
Would that difficulty also apply to wavelets of a higher frequency?

It would take several cycles of the sound for the ear to resolve anything from it. The ear does not have a sampling system and it can't react instantaneously, so the signal has to be somewhat stationary for several cycles to be resolved in the brain. For a 100 Hz this would be about 50 ms. - well into the reverb tail of any small room.
 
It would take several cycles of the sound for the ear to resolve anything from it. The ear does not have a sampling system and it can't react instantaneously, so the signal has to be somewhat stationary for several cycles to be resolved in the brain. For a 100 Hz this would be about 50 ms. - well into the reverb tail of any small room.

Please excuse my ignorance on the subject, but does this mean that less than about 5 periods of a 100 hz tone would not be heard at all?
 
Please excuse my ignorance on the subject, but does this mean that less than about 5 periods of a 100 hz tone would not be heard at all?

Your ability to detect its pitch, or its direction would be seriously degraded. You would "sense" something, but you could not really tell what frequency it was. Hence, in a small room the sound field has reached steady state well before this happens, which is the reason that I state that the sound field in a small room at LFs is basically a steady state situation and as such the EQ should be done on the steady state signals. To be valid this requires spatial and frequency averaging. This is quite different than the situation above say 500 Hz where we can resolve pitch and direction of even the direct signal well before there are any reflections - unless those reflections are coming very soon. If they do arrive very soon after the direct sound then the ear will use them in its analysis.
 
Let me start by stating that I haven't really investigated the theory of the matter of localization of low-frequency sound-sources. Two of my observations however contradict with what you are saying (EDIT: not necessarily in the above post).

With a sine-wave it is impossible for me to hear the direction from which it originates up to a couple of hundred hertz. This is in line with what you are saying. But how do you explain that hearing direction on those low-passed speech samples Markus posted is so easy?

You say we mainly hear direction on the basis of level differences and differences in time of arrival at both ears, and that these differences are too small to be able to hear direction of low frequencies. This seems intuitively right to me. Yet I can easily hear direction of low frequency sine-waves outside, without early reflections except from the floor. How is this possible?
 
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Let me start by stating that I haven't really investigated the theory of the matter of localization of low-frequency sound-sources. Two of my observations however contradict with what you are saying (EDIT: not necessarily in the above post).

With a sine-wave it is impossible for me to hear the direction from which it originates up to a couple of hundred hertz. This is in line with what you are saying. But how do you explain that hearing direction on those low-passed speech samples Markus posted is so easy?

You say we mainly hear direction on the basis of level differences and differences in time of arrival at both ears, and that these differences are too small to be able to hear direction of low frequencies. This seems intuitively right to me. Yet I can easily hear direction of low frequency sine-waves outside, without early reflections except from the floor. How is this possible?

I have not listened to Markus demos so I can't comment. I suspecxt that there is some significant information well above 100 Hz.

Theoretically you should not be able to localize 50 Hz out of doors. I can't explain your results execpt to say that any nonlinearity will defeat the test because you can easily localize on the harmonics.

I usually do not worry about distortion from a sub for several reasons, but the harmonics CAN make the sub localizable and that is a problem.
 
Please excuse my ignorance on the subject, but does this mean that less than about 5 periods of a 100 hz tone would not be heard at all?


Hello,

5 periods of a a 100Hz pure tone (sine) will possess a complex spectrum (a lot of components with f < 100Hz and also some over 100Hz). It will most surely not sound as a pure tone...

Give a look to the spectrum of a pulse made of 5 periods of 100Hz sine in the attached file. (the 5 periods are preceded and follown by 10seconds of silence.)

Best regards from Paris, France

Jean-Michel Le Cléac'h, France
 

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Hello,

5 periods of a a 100Hz pure tone (sine) will possess a complex spectrum (a lot of components with f < 100Hz and also some over 100Hz). It will most surely not sound as a pure tone...

Give a look to the spectrum of a pulse made of 5 periods of 100Hz sine in the attached file. (the 5 periods are preceded and follown by 10seconds of silence.)

Best regards from Paris, France

Jean-Michel Le Cléac'h, France

Jean-Michel

No one would do it that way!! And in all my discussions I said a "wavelet" meaning a slow rise and fall of the wave. This would have a very narrow range of frequencies centered on 100 Hz. But of course you knew that, which makes me wonder why you made such a comment.:confused:
 
I thought of the possibility of harmonics causing the ability to localize the source, but with a stimulus of 100 hz that would have to mean quite an amount of higher order harmonics. Not impossible, but unlikely IMHO.

How much harmonic content is required? The third harmonic at 300 Hz could be quite detectable (as far as localization is concerned) at even very low % THD.
 
Okay, so the source-direction of a pure 300 hz tone should be audible. This is a much lower frequency than the approximately 1000 hz you usually mention. Do you believe a frequency in the whereabouts of 300 hz to be the lower frequency limit for hearing direction in the free-field and 1000 hz to be an approximate lower frequency limit for hearing source-direction in a small room?
 
Heavens no! Where did you ever get the idea that I thought that? We do have decent directional sense at 300 Hz particularly with no reflections. In a small room the directionality will be compromised when reflections are present. But the key point here is that our sense of directionality at 300 Hz is not on par with what it is at 1 kHz and above. No one is arguing that there is some directionality at 300 Hz, only that it is so much stronger at 1 kHz and above that if there are signals above 1 kHz they will dominate the locational sense of the signal.
 
Okay, then at least that is out of the way. I mistakingly thought you were of the opinion that directivity was not important below approx. 1 khz because there was no directionality below that frequency.

It is nevertheless interesting to think about why sine-waves up to a couple of hundred hertz have less directionality than Marcus' LR4 low-passed speech material. Would you give it a listen? I'd like to hear your view on it.
 
Hello,

Since this thread is about a combined system with a loudspeaker and a room, one must not forget the speaker! And in particular the temporal effects of the combined system, and the most important reason for temporal fidelity - directivity. It's well known that a monopole gives a poor rendering of the low freq information inside a small room whereas the performance of a directional source is much more better.

http://www.diyaudio.com/forums/multi-way/145876-measured-monopole-dipole-room-responses.html

- Elias
 
(and common) to hook all your sources like cable/satellite/internet receiver, disc player, game console, etc. to an AVR and TV."

well, literally none of my audiophile and music lovers colleagues have it

but yes, I am aware that we are in minority from mass-market consumer point of view
as a matter of fact we are freaks, to watch movies we go to a cinema, we don't have iPods and don't use computers for audio purposes, we are even interested in music not only like some! ;)

however I wasn't aware that for some users the diyaudio.com is a mass-market-consumer-crap-oriented forum

My experience is different. All omni directional concepts I have heard did create the very same aural space for each and every recording. Single sounds were always oversized and localization was ambiguous.

yes, Your experience is obviously different from mine, Moulton's, Hegeman's, Carlsson's, Salvatore's to name a few and of many, many (yes, many!) people who praise imaging and soundstaging of MBL 101 or Beolab 5 to name just two
 
Okay, then at least that is out of the way. I mistakingly thought you were of the opinion that directivity was not important below approx. 1 khz because there was no directionality below that frequency.

It is nevertheless interesting to think about why sine-waves up to a couple of hundred hertz have less directionality than Marcus' LR4 low-passed speech material. Would you give it a listen? I'd like to hear your view on it.

The point is that below about 500 Hz our hearing is loosing its directional resolution to the point where, in a small room, it is virtually gone at about 100 Hz. This certainly de-emphasizes the importance of directivity at these frequencies even if it does not make it altogether irrelavent. The critical thing is that above about 1 kHz we must have constant and controlled directivity and below 500 Hz it is of dubious value.
 
yes, Your experience is obviously different from mine, Moulton's, Hegeman's, Carlsson's, Salvatore's to name a few and of many, many (yes, many!) people who praise imaging and soundstaging of MBL 101 or Beolab 5 to name just two

My impression is that virtually no one in professional content creation uses these kind of speakers.

I once heard the Beolab 5 - honestly, that was one of the worst loudspeakers I've ever listened to.
 
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Like Keyser I have a had time localizing sine waves. For me, at most any frequency. :(

So I thought I'd try this test.
  1. The filtered Voice. No problem telling where it came from. In fact I had to turn off the right channel to even hear the left.
  2. White noise low passed at 300Hz. Also very easy. No mistake.
  3. 300Hz sine wave. It came out of the wrong channel! Until I realized that it was actually coming from where I put it. But because I happened to be looking at the silent speaker, it "stuck" there. Had to move around some to unstick it. But, sitting between the speakers it seemed to come mostly from the center.

All the tests were done with only the woofers on, no mid or tweeter. Woofer low passed at 450Hz, 3rd order.

The voice file does contain info above 300Hz, see my FFT graphs below. However the 300Hz white noise does not contain much, I used a steep filter.

For me, the trouble comes with pure sine waves. I'll try to test where white noise has to be low passed for me not to be able to locate it on my system.

Interesting stuff!
 

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