SO ... HOW do we measure soundstage???

[Duke]

In my view that is mostly wishful thinking.

It is accomplished routinely in studio control rooms, by managing the in-room reflection arrival times.

A concert hall has reverberation time around 2000ms. A listening room <500ms.
What later reflections should be "conveying"?

Assuming the reverberation of the concert hall is on the recording, then that reverberation is IN the in-room reflections. To put it another way, the in-room reflections function as "carriers" for the reverberation tails on the recording, assuming they retain enough overtone structure for the ear/brain system to correctly identify them as hall reverberation.

And how do you get later reflections without earlier ones?

Good question!

One way to do it is with room geometry. Studio control rooms often avoid early reflections at the mix position by having the first reflection paths for the main monitors miss the mix position. Often the side walls are angled such that the first lateral reflections pass behind the mix position. (Normally it's not possible to do this with the wall behind the mix position, so path length distance is used to push the arrival of those particular first reflections back in time.)

In a home audio setting one can use directional loudspeakers and toe them in far enough to avoid having significant ipsilateral first reflections, such that the first significant horizontal-plane reflections are the contralateral ones, which arrive after a considerably longer path-length-induced time delay.

Imo absorbing the first sidewall reflections is problematic, as that energy is no longer available to arrive as later reflections. In a home audio setting I prefer to minimize the first sidewall reflections via sufficiently narrow radiation patterns and aggressive toe-in. If that's not feasible, ime diffusion of the first sidewall reflections is generally preferable to absorption.

 

[Suono]

first reflections
early to control, absorb, spread

 

[slaweks]

It is accomplished routinely in studio control rooms, by managing the in-room reflection arrival times.



Assuming the reverberation of the concert hall is on the recording, then that reverberation is IN the in-room reflections. To put it another way, the in-room reflections function as "carriers" for the reverberation tails on the recording, assuming they retain enough overtone structure for the ear/brain system to correctly identify them as hall reverberation.



Good question!

One way to do it is with room geometry. Studio control rooms often avoid early reflections at the mix position by having the first reflection paths for the main monitors miss the mix position. Often the side walls are angled such that the first lateral reflections pass behind the mix position. (Normally it's not possible to do this with the wall behind the mix position, so path length distance is used to push the arrival of that first reflection back in time.)

In a home audio setting one can use directional loudspeakers and toe them in far enough to avoid having significant ipsilateral first reflections, such that the first significant horizontal-plane reflections are the contralateral ones, which arrive after a considerably longer path-length-induced time delay.

Imo absorbing the first sidewall reflections is problematic, as that energy is no longer available to arrive as later reflections. In a home audio setting I prefer to minimize the first sidewall reflections via sufficiently narrow radiation patterns and aggressive toe-in. If that's not feasible, ime diffusion of the first sidewall reflections is generally preferable to absorption.

"the in-room reflections function as "carriers" for the reverberation tails on the recording" .
They do need to be, the late reverberation is in the signal, it does not need to be extended by the room reverberations.

 

[Suono]

useful or good reflections to listen to ambience

 

[Justdafactsmaam]

The reflections of our room, appropriately controlled and treated, allow us to reproduce the environment where the recording was made.

No it doesn’t. Your room and a concert hall are not interchangeable

 

[Duke]

"the in-room reflections function as "carriers" for the reverberation tails on the recording" .
They do need to be, the late reverberation is in the signal, it does not need to be extended by the room reverberations.

The idea is not for the playback room's decay time to add to the reverberation decay times on the recording, and most playback rooms are far too small to do this to any significant degree anyway.

The ideas is for the playback room's reflections to deliver the reverberation on the recording from many different directions, which is highly desirable. Arguably the worst direction for reflections to arrive from is the exact same direction as the direct sound.

 

[Suono]

then try listening in free field or anechoic and see if you can hear the event environment

 

[Justdafactsmaam]

In the playback room there is, in effect, a competition between two "packages" of venue cues: The venue cues on the recording, and the "small room signature" cues of the playback room. The ear/brain system tends to accept the most plausible package of cues rather than combining and conflating two conflicting packages of cues. The desired outcome is for the venue package of cues on the recording to be perceptually dominant.

The playback room's signature is most effectively conveyed by the early reflections, while the venue cues on the recording (in particular the reverberation tails) are most effectively conveyed by the late reflections, assuming they are spectrally correct, or nearly so.

By managing the in-room reflections to minimize the early ones, while preserving the spectral balance of the later ones, it is possible for the recording venue's package of cues (whether they be real or engineered or both) to become perceptually dominant. This is sometimes referred to as a "you are there" presentation.

If you minimize the early reflections of a listening room there are no later reflections to “balance” whatever that is supposed to mean or how it’s supposed to be done.

But yes, if you minimize the listening room reflections you have done part of the job of allowing the spatial cues on the recording to be heard and to work in conveying the recording space.

 

[Suono]

If you minimize the early reflections of a listening room there are no later reflections to “balance” whatever that is supposed to mean or how it’s supposed to be done.

 

[Justdafactsmaam]

then try listening in free field or anechoic and see if you can hear the event environment

My room has an RT 60 bellow 100 milliseconds from about 125 hz on up. In conjunction with the BACCH SP I get an astonishing recreation of the concert hall acoustic space with many classical recordings.

Something that no conventional stereo in even a modestly reverberant room could begin to do.

 

[Justdafactsmaam]

Your image fails to represent the attenuation when you minimize early reflections.

Why don’t we look at something real like a waterfall plot?

 

[Thomas_A]

My room has an RT 60 bellow 100 milliseconds from about 125 hz on up. In conjunction with the BACCH SP I get an astonishing recreation of the concert hall acoustic space with many classical recordings.

Something that no conventional stereo in even a modestly reverberant room could begin to do.

Do you believe that this is a true recreation of the event (i.e. equal to the signal generated at your eardrum, as if your where there, and which seating?) or just a recreation of the recording? Why not use true binaural recordings from best seating position?

 

[olieb]

Arguably the worst direction for reflections to arrive from is the exact same direction as the direct sound.

Why exactly is that? This is where the reflections in the concert hall come from mainly, at least during the first 100ms.
And in a typical listening room (with unidirectional speakers) there is a very pronounced lack of frontal (earlier) reflections, everything is coming from back (and sides).

 

[goat76]

Do you believe that this is a true recreation of the event (i.e. equal to the signal generated at your eardrum, as if your where there, and which seating?) or just a recreation of the recording? Why not use true binaural recordings from best seating position?

For binaural recordings to work with loudspeakers, a crosstalk cancelation program like BACCH is needed for such a recording to be properly reproduced. But for normal 2-channel recordings, the BACCH filter will just act as a sound effect, a sound effect that can either cater to someone's subjective liking or completely ruin the mix depending on how the mix is made.

 

[Duke]

[In reply to Duke's statement that "arguably the worst direction for reflections to arrive from is the exact same direction as the direct sound."] Why exactly is that?

I read it in Floyd Toole's book. He described a study, presumably in an anechoic chamber, wherein a single reflection was simulated by a delayed signal sent to a second loudspeaker placed at different angles to one side. They included the case of the reflection being generated by the first loudspeaker (no second loudspeaker), such that the reflection arrived from the exact same angle as the direct sound, and this was judged to be the worst from the standpoint of perceived coloration.

This [from the front] is where the reflections in the concert hall come from mainly, at least during the first 100ms.

Is your point that the reflections from the front of the concert hall are sufficient to convey the perceptions of spaciousness and envelopment? If so, why do multichannel recordings rely on side and rear channels to convey spaciousness and envelopment? My point being, the delivery of hall reverberation energy from many directions is desirable. And the in-room reflections can do this if they are spectrally correct and do not arrive too early.

 

[goat76]

"the in-room reflections function as "carriers" for the reverberation tails on the recording" .
They do need to be, the late reverberation is in the signal, it does not need to be extended by the room reverberations.

The reflections that occur in the listening environment can't distinguish between the recorded direct sounds and the recorded reverberation tails, it "makes a soup" of everything and treats it all as one single continuously changing sound, but as long as the early reflections are kept under control, the diffuse field of sound the late reflections adds to the equation can add a sensation of envelopment (even if this soup of diffused sound contains a mess of every single sound in the recording, no matter if it happens to be recorded direct sounds or recorded reverberation tails).

 

[Justdafactsmaam]

Do you believe that this is a true recreation of the event (i.e. equal to the signal generated at your eardrum, as if your where there, and which seating?) or just a recreation of the recording? Why not use true binaural recordings from best seating position?

Of course it isn’t a true “recreation” of an event. That is literally impossible. We are limited to the spatial cues encoded on any given recording. None of which will give us a “true” recreation of that sound field.

It’s also not what I said. I called it astonishing. And I called it that because that was exactly my reaction the first time I heard it.

With that said a custom binaural recording made with in ear microphones of the listener will give you 100% accurate spatial recreation in playback.

 

[Blumlein 88]

Do you mean that Polk had three-channel or just crosstalk cancellation? Have been talking with the constructor of Bremen speakers and system, it is a bit secret but based on a center speaker and speakers placed on the sidewalls. I would guess these replace the L/R primary wall reflections and makes the side walls "invisible". But perhaps also act L/R speakers to widen the front scene with the center to create phantoms between L-C and C-R (i.e. three-channel). Those who have heard it says it is really very close to a real event, and you could even walk around in front of the system and get the same impression. I would really want to hear that system some time.

Any of the Polk SDA speakers. I think it was Stereo Dimensional Array. They still do it and have in one form or another since the 1980's.

Stereo, Supersized: Inside Polk SDA Technology | Polklore

Try this little experiment: Close our eyes and listen to the sounds around you. Notice how you can easily tell where sounds are coming from, even when you can’t see them?

www.polkaudio.com

 

[Justdafactsmaam]

For binaural recordings to work with loudspeakers, a crosstalk cancelation program like BACCH is needed for such a recording to be properly reproduced. But for normal 2-channel recordings, the BACCH filter will just act as a sound effect, a sound effect that can either cater to someone's subjective liking or completely ruin the mix depending on how the mix is made.

Nonsense. It’s not a sound effect. It removes a sound effect. The effect of speaker cross talk. Something that is not on the recording.

 

[olieb]

Is your point that the reflections from the front of the concert hall are sufficient to convey the perceptions of spaciousness and envelopment?

My point is that in the concert the bigger part of reflections comes from the front, so it seems to be quite a natural thing.
In the listening room the early reflections are mainly not from front (unless with bidirectional speakers). So this is different, maybe not very natural/balanced, I don't know.
The envelopment in the concert will in any case not translate easily to the listening room, as everything there will emanate from the two frontal (unidirectional) speakers.

He described a study, presumably in an anechoic chamber, wherein a single reflection was simulated by a delayed signal sent to a second loudspeaker placed at different angles to one side. They included the case of the reflection being generated by the first loudspeaker (no second loudspeaker), such that the reflection arrived from the exact same angle as the direct sound, and this was judged to be the worst from the standpoint of perceived coloration.

Well this is certainly interesting, but "anechoic" and delayed from (the same) speaker might be rather different than a room reflection and of course one would have to know what kind of delay we are talking about.
This experiment on the other side hand looks as if one was checking on the effect of crosstalk though.