Putting the Science Back into Loudspeakers

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#462
ScottG said:
On other topics I remember (particularly the "stereolith" thread which I liked very much), but stereo bass as well in either config. mentioned?

If so, cool! 🙂 (..and yes, then I did miss it. 😱 )
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Oh your emphasis was on stereo - no I didn't do "near field stereo bass". I just tested near field mono bass. That alone would be an interesting topic for further investigations. Probably nothing this thread is about 🙂
 
#463
markus76 said:
Oh your emphasis was on stereo - no I didn't do "near field stereo bass". I just tested near field mono bass. That alone would be an interesting topic for further investigations. Probably nothing this thread is about 🙂
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..yes, mono near-field I remember (..dipole I believe).

Mono bass near-field (behind the head) is something I've advocated as an alternative to Earl's distributed bass method (..largely because it's cheaper and requires less floor space). Not the same of course, particularly in that it's only good for the single listener, but when equalized it can sound as good (or even better) in that it often provides a more tactile sensation. I've done this in multiple "enclosure" formats, my favorite wasn't dipole - but rather a long folded transmission line with a low fs driver. (..dipole would be optimal for apartment living though.)
 
#464
markus76 said:
I don't know any "system that preserves low freq ITD cues" within acoustically small rooms. I believe "better" in this case is flat mono bass and spatial cues from higher frequencies.
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Griesinger states that monophonic bass without any ITD undulation results inside the head locatedness in a small room.

I have confirmed this in my room with monophonic bass with monopole speakers and, indeed, the bass is inside your head ! This is not good, not good at all.

- Elias
 
#467
speaker dave said:
with legato strings you may never hear the hall contribution at all.

I'm not the first person to comment on this as it has been well observed before.

David S
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Yes true. The hall sound is perceived during short pauses in music.

Constant steady state sinusoidal tone does not produce hall sound.

The perception goes in foreground and background streams, and reverberation is one of them.
 
#470
Kindhornman said:
Elias,

So do all concert halls sound the same then until there is a break in the music. or is that a very blanket statement that is not really true?
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Can I have a third choice?

With a truly steady state signal (say long term pink noise) the only thing the hall can contribute is strength or strength vs. frequency. RT, EDT, early/late ratios, IACC and other standard measures are all about how sound builds up and the decays between our two ears.

As I stated several times, yes, you would probably figure out you were in a warehouse, even with slowly varying music. Still, it is considerably less obvious with slow music than with dynamic music or, especially, voice.

David S
 
#471
I was reading that with amusement because I did a gig about a week ago in a big, reverberant shed. 100'x100', concrete walls and floor, steel ceiling. Speakers in the center. Wow, it was live!

At one point I was playing a 1000 Hz tone. I stopped it. The sound did not stop! Then about 3 seconds later it died. Wild. You could punch the mute button on the console and nothing would happen for a few seconds - a strange feeling. We were all laughing and taking turns doing it.

Despite that, it was obvious that it was a large, diffuse sound-field, not a small room at all. I'm not sure where the clues lay, but it was obvious. Identifying it as a warehouse blindfolded might have been tough, however.
 
#472
Elias said:
Griesinger states that monophonic bass without any ITD undulation results inside the head locatedness in a small room.

I have confirmed this in my room with monophonic bass with monopole speakers and, indeed, the bass is inside your head ! This is not good, not good at all.

- Elias
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I don't get in-head localization nor have I heard such reports from others using multisub configurations.

How did your test look like?
 
#474
I did not really notice in-head localization with the near field subs yesterday. I was playing lots of Massive Attack with meaty bass lines - the bass moved to the localization cues from the front. I must admit though, that I've never heard a room with high quality bass at high SPL, so I don't have that reference.

For my apartment dwelling, nearfield bass is a good compromise. It is hard to get to realistic SPL without being a nuisance, otherwise, and realistic SPL is important for the illusion as a whole. It passed the fiancee test. I showed her how we can turn it up in a 'bass cocoon' but have the bass disappear when you get up. We had a nice post work debrief with our favourite songs

Note that you have to be careful that there isn't any mechanical vibration giving away sub location at higher Hz.

This might not be appropriate for the thread, but an interesting device to try would be a pipe with mid bass drivers on both ends operating up to ~1000 Hz, behind the head. This could be responsible for bass and ITD, with HF HRTF content coming from front on. The result would be a combination of ambio and Watson. Perhaps such a setup has been suggested already.

markus76 said:
I don't get in-head localization nor have I heard such reports from others using multisub configurations.

How did your test look like?
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#475
markus76 said:
All current papers and solutions about low frequency optimization in acoustically small rooms use multiple subs driven by a summed signal.
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That's certainly true and I believe a multiple sub system is a big improvement over a single sub system.

However, I think Elias wanted to argue that your basic assumption, that we only hear the steady-state response at low frequencies, is wrong. I believe Blauert's "Spatial Hearing" should be of interest here. However, if I remember correctly, Toole states that below about 80 Hz there is no audible difference (in terms of locatedness) between mono and stereo bass.

(Please correct me if I'm wrong)
 
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#476
a_tewinkel said:
That's certainly true and I believe a multiple sub system is a big improvement over a single sub system.

However, I think Elias wanted to argue that your basic assumption, that we only hear the steady-state response at low frequencies, is wrong. I believe Blauert's "Spatial Hearing" should be of interest here.

(Please correct me if I'm wrong)
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There seem to be three factors involved.

First, in the presence of modal effects found in acoustically small rooms, is it even possible to deliver appropriate spatial cues? Due to modes the level can drastically vary between left and right ear. This is further complicated by how the two sources of a stereo sub setup couple to the modal field. Such conditions make it nearly impossible to deliver spatial cues to the listening position.

Secondly, not everybody agrees that stereo bass even exists. From Toole "Sound reproduction":
Stereo Bass: Little Ado about Even Less
With apologies to William Shakespeare, this issue relates to the fact that for
all the systems described above [i.e. multiple sub configurations] to function fully, the bass must be monophonic
below the subwoofer crossover frequency. Most of the bass in common
program material is highly correlated or monophonic to begin with, and bassmanagement
systems are commonplace, but some have argued that it is
necessary to preserve at least two-channel playback down to some very low
frequency. It is alleged that this is necessary to deliver certain aspects of
spatial effect.
Experimental evidence thus far has not been encouraging to supporters of
this notion (Welti, 2004, and references therein). Audible differences appear to
be near or below the threshold of detection, even when experienced listeners are
exposed to isolated low-frequency sounds. The author has participated in a few
comparisons, carefully set up and supervised by proponents of stereo bass, but
each time the result has been inconclusive. With music and fi lm sound tracks,
differences in “spaciousness” were in the small to nonexistent category, but differences
in “bass” were sometimes obvious, as the interaction of the two woofers
and the room modes changed as they moved in and out of phase. These were
simple frequency-response matters that are rarely compensated for in such
evaluations. Even with contrived stereo signals, spatial differences were diffi cult
to tie down. This is not a mass-market concern. In fact, some of the discussion
revolved around the idea that one may need to undergo some training to hear
the effects.
Another recent investigation concludes that the audible effects benefi ting
from channel separation relate to frequencies above about 80 Hz (Martens et
al., 2004). In their conclusion, the authors identify a “cutoff-frequency boundary
between 50 Hz and 63 Hz,” these being the center frequencies of the octave
bands of noise used as signals. However, when the upper-frequency limits of the
bands are taken into account, the numbers change to about 71 Hz and 89 Hz,
the average of which is 80 Hz. This means, in essence, that it is a “stereo upperbass”
issue, and the surround channels (which typically operate down to 80 Hz)
are already “stereo” and placed at the sides for maximum benefi t. Enough
said."
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Thirdly, stereo bass in (music) recordings is the exception and not the norm. So, why go to great lengths and find a solution to a problem that doesn't even exist?
 
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#477
markus76 said:
First, in the presence of modal effects found in acoustically small rooms, is it even possible to deliver appropriate spatial cues? Due to modes the level can drastically vary between left and right ear. This is further complicated by how the two sources of a stereo sub setup couple to the modal field. Such conditions make it nearly impossible to deliver spatial cues to the listening position.
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Perhaps subs close to the listening position could do the trick, or perhaps a multiple sub system in which subs could act as either the source or as a cancellation device to minimize modes. But I agree that it is a very difficult problem.

markus76 said:
Secondly, not everybody agrees that stereo bass even exists. From Toole "Sound reproduction":

[...]
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Indeed (that's the quote from Toole I was referring to). Perhaps the frequency to which "stereo bass" can be heard varies considerably between subjects.

Thirdly, stereo bass in (music) recordings is the exception and not the norm. So, why go to great lengths and find a solution to a problem that doesn't even exist?
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Good point. For me, with all factors considered, a multiple sub system is the best compromise.
 
#478
a_tewinkel said:
Perhaps subs close to the listening position could do the trick,
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It probably could in a one seat solution. But, would that remove the in-head localization Elias had? By the way, we still don't know what his test looked like.

a_tewinkel said:
or perhaps a multiple sub system in which subs could act as the source or as a cancellation device to minimize modes. But I agree that it is a very difficult problem.
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It looks like a physically unsolvable problem in acoustically small rooms.

a_tewinkel said:
Indeed (that's the quote from Toole I was referring to). Perhaps the frequency to which "stereo bass" can be heard varies considerably between subjects.
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Perhaps. We don't know. The only person in these threads that constantly reports different perceptions than the norm is Elias. He can localize tweeters and gets in-head localization with a monopole subwoofer.
 
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