Size matters : all the usual early reflections are retarded, the Schroeder moves, the ETC and RT 60 are expanded, all the distances listener/speaker or speaker/walls get longer, the speakers can be very high, the average listening level can (and has to) be louder, big amps, big speakers...
Is it a different game play ? Maybe, but as it happens that I have a bigger room than these guys, I think that some other aspects are more important for the actual debate, like the symmetry of the reflective surfaces or the rigidity of the boundaries (including the ceiling). A big fish tank is always a fish tank.
I also wonder how they manage the acoustical changes when their room is full of people.
So, Simon, dn't worry, you can have very good or better results in a small room, just the way to get them can be different...hence the plurality of opinions.
Ps : good remark for the speech intelligibility...what I hear daily here is that this is dependent of the nature of the boundaries : softer membrane = better
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or maybe even a bit less, 2-3 ms (Toole)
yes, and these are generally not available in a home listening room without delay lines.
yes that's fine, and you can expect a relatively narrow source width due to lack of reflections from the near side walls. Toole and Geddes diverge here by my reading: Toole says pick up the near side wall reflections for beneficial effects as long as they are not within 2-3 ms, Geddes says you need 10 ms of 'clear space', so avoid the near side walls.
Yes I agree that markus76's graphs are quite informative, and promising for the constant-directivity forward-facing speaker, thanks markus (assuming 60 ms = 0).
I'm talking about stereo cross talk and dipole line arrays as separate entities !
- Elias
Yes.
The interesting part is how these two situations are perceived. They are more similar than different. When I use toe-in the spatial presentation changes considerably. So it's probably not the overall level of single reflections that is important but the specific composition of early reflections.
This is all covered in section 8a of the article I linked (which was linked by someone else earlier in the thread):
"The maximum possible interaural time difference that can occur due to a sound source's move around the head (assuming an average head diameter of ~0.22m and speed of sound = 345m/s) is ~0.65ms or ~0.00065s.
For a sine signal to take advantage of IPD cues without resulting in ambiguity, its period must be at least twice this value (i.e. 2 x 0.00065s = 0.0013s), corresponding to a wavelength of at least twice the head's diameter (i.e. 2 x 0.22m = 0.44m/cycle).
Therefore, the absolute highest frequency for which IPDs provide useful cues is 1/0.0013 = ~770Hz.
For higher frequencies, single-cycle IPDs are not useful cues because they cannot be interpreted reliably, as they depend not only on sound source location on the horizontal & medial planes but also on frequency and, most importantly distance (widely different sound source locations can result in the same IPDs or the same angular location in the localization coordinate system may result in different IPDs)."
So you're right in your thinking, but wrong in your calculation
Exactly.
In a room that size with a bit of judiciously chosen damping / diffusion even stereo can made to be very immersive and convincing with the right speaker separation angle and the right recordings...(recordings with good ambience and locational cues encoded in them, rather than mono sources pan-potted left and right on a mixing desk...)
Although I'm sure Audissey works, the biggest single improvement of that test set-up over a typical home listening situation is probably the size and acoustics of the room, followed by presumably good quality speakers. If you have those, half the battle is won, and I wonder whether such a processing system would really work in any satisfactory way in a small reflective room that doesn't really have anywhere to put all the extra speakers.
Here you go. Floor plan:
An externally hosted image should be here but it was not working when we last tested it.
Nathan, right:
An externally hosted image should be here but it was not working when we last tested it.
By the way, we don't see any front wall reflections because the whole wall is absorptive. There's also a thick rug on the floor.
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Been there, done that
My last listening room but one was 4 metres wide by 8 metres long - not as big as the room discussed but a lot bigger than what I have now, and yes it needed bigger speakers especially for the low end compared to my current room, where I can get away with smaller speakers. (in fact have to, because of the clutter of the room)
But the acoustic performance of the bigger room was far superior. The lowest room mode was 24Hz, compared to 38Hz in this room, so bass response was a lot flatter at the bottom end, I was able to sit 3 metres away from the speakers (and enjoy loud music without that "small room clutter" sound) and yet still be in the middle of the room well away from walls, (whereas here I'm forced to sit right near the back wall) so both speakers and listeners were a lot further from walls, giving much greater reflection delays.
There are some aspects of reproduction that you can't miniaturise beyond a certain point as a room gets smaller, which set limits on the smallest acceptable room. For a floor standing speaker you generally don't want to sit closer than about 3 metres if you want it to integrate well, maybe 2.5 metres at the least, then to get decent stereo imaging and width that sets a minimum satisfactory speaker separation. Once the separation is determined you still need enough room width beyond the separation to keep the early reflections delayed enough.
Then there are the aesthetic aspects - sofas don't generally get any smaller in small rooms, they just take up more of the room, and in a smaller room side-wall sofas start to seriously intrude in the near line of site path from speaker to listener, causing their own early reflections - generally only on one side of the room, as a small room typically forces one sofa at the back of the room and one on one side, etc ad nauseum.
To get a decent set-up which is not too compromised by the room, and yet doesn't take over the room (still a multi-purpose family/TV room) I think you're looking at a minimum room size of around 6 metres by 4 metres, (19.7 feet by 13.1 feet) and that's only allowing for two floor standing stereo speakers, and not considering surround speakers. My previous listening room was 6m x 4m, and it felt like a "comfortable minimum" size to me.
Yes its possible to make do in a smaller room, especially if you are willing to go with much smaller speakers, but the ultimate result is significantly compromised compared to the larger room, for a myriad of reasons.
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@humdinger
@dbmandrake
Seems there is evidence for a kind of "transitional range".
"Duplex theory" from german Wikipedia
Duplex-Theorie ? Wikipedia
Excerpt:
"Der Bereich zwischen 800 Hz und 1600 Hz – also zwischen den beiden Duplex-Bereichen – liegt genau im Blauertschen Hintenband,
was bei Anheben der Frequenzen nahe um 1 kHz einen diffusen, entfernten und räumlichen Klang ergibt.
(Das Gegenteil von einem „Badewannenfilter“).
In einer Studie konnten Wightman und Kistler 1992 nachweisen, dass die ITD für breitbandigen Schall die lokalisierte Richtung
dominieren, wobei die Dominanz von der unteren Grenzfrequenz des Schalls abhängt. 2002 bestätigten Macpherson und Middlebrooks
die Duplex-Theorie: Sie konnten zeigen, dass die ILD im Gegensatz zu den ITD auf tiefpassgefiltertes Rauschen kaum, jedoch auf
hochpassgefiltertes deutlich dominant wirkten."
And my own rough translation of the excerpt:
"The range between 800Hz and 1600Hz - between the two duplex ranges - is located exactly in the directional 'rear' band
(referring to directional bands according to Blauert), which causes a diffuse, faint, and "spatial" impression if pronounced using
a filter.
In a study Wightman and Kistler 1992 demonstrated, that ITD cues are dominant for localisation of broadband sound,
where degree of dominance is dependent on the lower frequency limit of the sound. In 2002 duplex theory was confirmed by
Macpherson und Middlebrooks: They could show, that ILD has low impact on localisation compared to ITD when using lowpass
filtered noise, but was dominant in highpass filtered noise."
Directional bands according to Blauert:
http://de.wikipedia.org/w/index.php...htungsbänder.svg&filetimestamp=20101030072155
Translation of directions in the diagram:
"vorn" > "front"
"hinten"> "rear"
"oben" > "above"
_________
A "default direction" may be implemenented in the "firmware" like:
"If you don't know where it comes from (take care) , it may come from behind".
Because our eyes are oriented to the front, those individuals having that
implementation of "default direction" could have had better chances to survive
in the evolutionary process.
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The ceiling reflection arrives before the ipsilateral wall reflection ? How is this possible, unless the speakers are a long long way from the side walls ? Also where is the floor reflection ?
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Yes, the path via ceiling is 1,49ms=51cm shorter. The speakers are 1.32m from the side wall. The ceiling is 2.52m. Speaker and ear height is 95cm.
The floor reflection is absorbed by a thick rug.
seems? ...eerrr, isn't such transitional range long established textbook fact?
http://acousticslab.org/psychoacoustics/PMFiles/Module08a.htm#12c
http://acousticslab.org/psychoacoustics/PMFiles/Module08b.htm#12c
what kind of broadband signal? steady (sine waves, noise)? what kind of listening environment (anechoic, reverberant or none ie. headphones)?
I mean was the duplex theory confirmed specifically in case of localisation of multiple virtual sound sources in a small reverberant room?
If not - what is the relevance of this research for our discussion here?
graaf, i was currently not intending to write a doctor's thesis but
just pointing to evidence for the existence of that transitional range,
because that was discussed some posts before ...
The lowpass / highpass filtered sound was noise, at least in the
Macpherson / Middlebrooks study.
I do not know either how that noise was presented (which Envelope ?),
we would have to refer to the paper.
And - yes - we may agree in omitting the word "seems" in my above statement:
"Seems there is evidence for a kind of 'transitional range' ".
__________
I try to keep my wording on the save side you know, because even
duplex therory as such has been disputed by a member committed to
this thread.
(The above is to be understood as purely and sincerely constructive.)
But my goal was just finding evidence for the transition range.
As is see things "duplex theory" is nowadays more a superordinate (and fairly old)
concept which leaves space for refinement in which cues are relevant especially
above the transition range. That is IMO a developmental pattern often seen in
the history of science: A former theory is refined, but stays valid as a kind
of superordinate concept. Not all theories in science have the same degree
of abstraction.
But even that may be disputable ...
just pointing to evidence for the existence of that transitional range,
because that was discussed some posts before ...
The lowpass / highpass filtered sound was noise, at least in the
Macpherson / Middlebrooks study.
I do not know either how that noise was presented (which Envelope ?),
we would have to refer to the paper.
And - yes - we may agree in omitting the word "seems" in my above statement:
"Seems there is evidence for a kind of 'transitional range' ".
__________
I try to keep my wording on the save side you know, because even
duplex therory as such has been disputed by a member committed to
this thread.
(The above is to be understood as purely and sincerely constructive.)
But my goal was just finding evidence for the transition range.
As is see things "duplex theory" is nowadays more a superordinate (and fairly old)
concept which leaves space for refinement in which cues are relevant especially
above the transition range. That is IMO a developmental pattern often seen in
the history of science: A former theory is refined, but stays valid as a kind
of superordinate concept. Not all theories in science have the same degree
of abstraction.
But even that may be disputable ...
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Thanks Oliver, these few words :
The range between 800Hz and 1600Hz - between the two duplex ranges - is located exactly in the directional 'rear' band
are very relevant for me, I was not aware of a transitional zone, and haven't seen the relationship with the rear band, while using these curves (inverted) for my rear speakers.
The range between 800Hz and 1600Hz - between the two duplex ranges - is located exactly in the directional 'rear' band
are very relevant for me, I was not aware of a transitional zone, and haven't seen the relationship with the rear band, while using these curves (inverted) for my rear speakers.
Interesting point, also mentioned in that introduction to psychoacoustics link.
Related to this, I was recently (before reading that article) playing around with equalizing the surround dip in my speakers (a 1/4th octave few dB dip at 1Khz) which I've never bothered to do anything about before, and with the response flattened in this region image localization doesn't seem as good to me.
With the dip left uncorrected forward image localization is strong and so is the phantom channel. With the dip removed the front/rear location of the image does indeed seem to be a bit more indeterminate, and not as strongly "forwards" as before.
It seems that a small dip in the middle of this band may help (artificially) strengthen the impression that the sound source is ahead of you. On the other hand the sound quality and tonal balance seems better with the response flattened in this region, particularly on speech.
Interesting because many drivers put a dip in the response somewhere between 800-1200 Hz, and those that do might be perceived to image better, even if it's actually due to an error in the frequency response.
I'm unsure what to make of this from a practical perspective - it may be that there are other complementary errors in the frequency response that need correcting that may be playing against the error at 1Khz, so I have more investigation to do...on the one hand I want them as accurate as possible, but on the other hand I do like strong imaging, and I don't want to have to choose between the two.
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Even many conventional cone + dome 2-ways have a dip in power response in that transitional range.
In my own free interpretation this may enforce a "front oriented" impression, but also hamper
"spacious" impression. Due to beaming of the 2-way's woofer, you would have to introduce an
on axis hump in this range to provide flat power response ...
That hump caused by directional radiation from the front may also contradict the
"default spectral interpretation" (which is "rear") of pronounced intensity in that range.
Severe coloration (subjectively) would be the price for flattening the power response
of such a 2-way. So one is better off introducing a dip in the power response.
"Flatness on axis" can't be the only issue involed, because you could compensate for beaming of
the woofer by more/less/no toeing in as well. But that doesn't work as well due to my own experience,
the comon 2-way (2 ... 2,5 Khz crossover) will usually have (need) that dip in power response.
In my own free interpretation this may enforce a "front oriented" impression, but also hamper
"spacious" impression. Due to beaming of the 2-way's woofer, you would have to introduce an
on axis hump in this range to provide flat power response ...
That hump caused by directional radiation from the front may also contradict the
"default spectral interpretation" (which is "rear") of pronounced intensity in that range.
Severe coloration (subjectively) would be the price for flattening the power response
of such a 2-way. So one is better off introducing a dip in the power response.
"Flatness on axis" can't be the only issue involed, because you could compensate for beaming of
the woofer by more/less/no toeing in as well. But that doesn't work as well due to my own experience,
the comon 2-way (2 ... 2,5 Khz crossover) will usually have (need) that dip in power response.
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