Studio mains - soundstage depth?

[fineMen]

... eliminates the early reflection off the wall behind the speakers, which is a significant "small room" cue, particularly when it comes to soundstage depth.

Pulling the speakers further away from the front wall pushes that reflection back in time, and ...Absorbtion is imo the last resort because ...

Q: the reflection from the front wall originates at the speaker backwards. Hence the spectral content is with the vast majority of speakers quite limited. Say to frequencies below 200Hz or so. How would that frequency range contribute to a sense of [space | room | soundstage | image | ...]?

Pulling the speakers into the room necessarily would shorten the time the reflections from the backside chime in. How close to that backwall is the sweet stereo chair situated anyway? The timing of backwall reflections is comparable to the timing of frontwall reflections. (No, they are not farther away.) Only that the backwall reflections are full spectrum, full amplitude.

Similar timing with sidewall reflections, but more relevant because of carrying directional cues, because from the sides.

I don't see the benefit of eliminating reflections by flush mounting, if absorption is a not so good thing.

Only because I read it somehere: putting speakers closer to a wall doesn't necessariyl enhance lower bass.

 

[Kvalsvoll]

Yes.

In the playback room there is a "competition" between the venue cues on the recording and the "small room signature" cues of the playback room. Flush mounting eliminates the early reflection off the wall behind the speakers, which is a significant "small room" cue, particularly when it comes to soundstage depth.



Pulling the speakers further away from the front wall pushes that reflection back in time, and the later it arrives the weaker the "small room signature" cues that it conveys. Diffusing that reflection also helps, as does deliberately reflecting it away from the sweet spot. Absorbtion is imo the last resort because it degrades the spectral balance of the reflection field in the room, but often it is still a net improvement. Diffusion arguably also degrades the spectral balance of the reflection field, but only a little bit.

This is how it is.

It is not the reflection from the front wall that creates depth. When speakers are moved away, this reflection is moved in time, and also spectral distribution and level is affected. Then we also realize that the speaker itself should make a difference - and it does; a speaker that does not radiate so much energy backwards into the front wall, can have good depth even when placed close to the wall.

 

[Tangband]

That soundstage depth is an illusion and your perception of it might be enforced by the physical space between speakers and front wall.
Though, there are reflections from the front wall that factor in, but I am not sure if it is crucial for the illusion.

Very true !

 

[Duke]

Q: the reflection from the front wall originates at the speaker backwards. Hence the spectral content is with the vast majority of speakers quite limited. Say to frequencies below 200Hz or so. How would that frequency range contribute to a sense of [space | room | soundstage | image | ...]?

With most speakers there is still enough wrap-around energy above 200 Hz to tell the ear/brain system that there's a wall behind the speakers. My observation has been that soundstage depth for non-flush-mounted conventional speakers is often limited to about twice the distance from the speakers to the wall, unless you "cross the threshold" and the venue cue package on the recording dominates over the "small-room signature" cue package of the playback room. If that happens, the perceived soundstage depth corresponds to the venue cues on the recording, or nearly so. (The ear tends to accept one package of cues or the other as being the most plausible, rather than synthesizing an average of the two, although some averaging may occur.)

Pulling the speakers into the room necessarily would shorten the time the reflections from the backside chime in. How close to that backwall is the sweet stereo chair situated anyway? The timing of backwall reflections is comparable to the timing of frontwall reflections. (No, they are not farther away.) Only that the backwall reflections are full spectrum, full amplitude.

The backwall reflections matter too, and contribute to the "small room signature" of the playback room. Moving the speakers forward (closer to both the listener and the back wall) does not change the arrival time differential between the direct sound and those reflections. If possible I suggest re-directing the first backwall reflections away from the listening area via angled panels.

I don't see the benefit of eliminating reflections by flush mounting, if absorption is a not so good thing.

Since absorption decreases in effectiveness as the wavelengths get longer, absorption tends to alter the spectral balance of the reflections accordingly (uniform broadband absorption being an expensive thing). This has several drawbacks:

1. Reflections can make a significant beneficial contribution to perceived timbre, so as the spectral discrepancy between the first-arrival sound and subsequent reflections is decreased by the absorptive material, timbre is degraded.

2. The ear looks at the spectral content of an incoming sound to judge whether it is a new sound or a reflection (repetition of a recent new sound). Degrading the spectral content of the reflections makes this ear/brain task more difficult, and can result in listening fatigue over time.

3. The in-room reflections are "carriers" of the reverberation tails on the recording, which convey much of the "venue size" cues on the recording. When we reduce the high frequency energy in the reflections we reduce their effectiveness as carriers of these venue size cues. Note that a panel of absorptive material sucks the highs out of every reflection that strikes it, not just the first one. So as the in-room reflections decay over time, their high frequency energy is progressively removed and their spectral balance becomes worse and worse, until eventually the ear can no longer classify them as "signal" and they become "noise".

In my opinion.

 

[fineMen]

In my opinion.

My opinion is based on my experiences, which are only scarse. It's individual.

I gave a hint on a recording, that delivers not only one space, but a few spaces simultaneously packed into each other. If such is possible, even with my quite humble set-up, where's the problem? Maybe that those spaces mentioned are acceptedly artificial for one, and second really support the artistical message, hence are relevant. There are other audio drama, using similar tricks, if Zappa comes too explicit for some.

And of course I answered the Q given myself by quick 'n easy experimentation. With the andecdotal result: bandlimited to 250Hz second order Q=0,5 (aka LR) the remaining sound of my stereo isn't "roomy". Room ... whatever You name it needs seemingly at least some mids to materialize. According to this, I tend to believe that the first reflections from behind the listener may be a bit more relevant than what comes back from the wall the speakers stand at. Reasoning given above.

When it comes to a problem statement regarding relevant time-ing of reflections, I'm not sure if the math was adequately expoited yet.

 

[Duke]

With the andecdotal result: bandlimited to 250Hz second order Q=0,5 (aka LR) the remaining sound of my stereo isn't "roomy". Room ... whatever You name it needs seemingly at least some mids to materialize...

In another thread apparently you described your system in more detail:

Practically I've got speakers with a directivity index of about 6(dB) @ 300Hz gradually narrowing down to about 9(dB) @ 10khz. These are toed-in by 45°. Due to the actual radiation pattern this alters the effective directivity index to, say 5 and 7 respectively. A DML with 'chaotic' phase rendition but very wide dispersion is added behind the baseline of the former two. Since the DML is a dipole, it was possible to minimize the output towards the listener. It was integrated by feeding it with a summed left+right signal, crossed over @ 1kHz with a quite shallow 6dB/oct. The level (measured in the reverberation filed), referred to the mains (both) was not critical at all. The difference between -10dB up to 0dB was gradual, not game changing. Don't say this is the holy grail, but it catches my interest still. Visitors like it, and my cat too.

So if I understand correctly, you have narrow-pattern main speakers toed-in by 45 degrees, and then behind your main speakers is a single dipole speaker facing the side walls (nulls towards the sweet spot and towards the "front" wall), which receives a summed (L+R) signal. Is this correct?

If so, your observation that the sound of your stereo isn't "roomy" makes sense to me. Imo your configuration is doing at least two things which tip the spatial perception away from the "small room signature" of the playback room and towards the "venue signature" on the recording:

1. The earliest reflections are the one which most strongly convey "small room signature", and your narrow-pattern main speaker with 45 degrees of toe-in minimize the amount of energy in the early reflections. Aiming the null of your supplemental dipole speaker towards the listening area prevents it from adding significantly to the early reflections.

2. The later reflections do not strongly convey small-room signature, but they do act as the carriers for the venue cues on the recording, in particular the reverberation tails. Because of the relatively late-arriving contribution of your dipole speaker, you end up with MORE beneficial, late-onset, spectrally-correct reflection energy than would normally be the case. This has the net result of strengthening the presentation of the venue cues on the recording.

So imo your configuration results in relatively weak "small room signature" cues from your playback room, combined with relatively strong "recording venue signature" cues, which makes it more likely that the latter will dominate the listener's perception. My guess is that the soundstage you hear varies a lot from one recording to the next, being dominated by the recording rather than by the playback room.

And there is one other thing your configuration probably does well: The contribution of your dipole speaker probably corrects the spectral balance of the reflection field, so that it more closely resembles the spectral balance of the direct sound. This would show up as improved timbre and reduced listening fatigue.

In my opinion.

 

[fineMen]

So if I understand correctly, ...

You do perfectly. I'm pretty much delighted that the set-up as such could be understood from my description. I then thought, that the additional sound from the dipole would rather subsummize under 'early reflections', though.

Why we not come together easily might originate in different expectations. I mean, the soundstage-ing in general doesn't support the stream of (musical) ideas too much. Times that uber-focus on imaging (pun intended) distracts from the art. I don't see a point in discussing this back and forth with so little validated info at hand. Not to forget the vast number of different methods to render stereo, beginning with the original recording (mikes, speparated booths, ... ), panning, mixing, DSP and lots more.

By the way, my room is by European standards not too small with 5 / 8+4 / 6 meters w / d / h.

In a way smaller venue I once used on-wall speakers with great success. If my recollection doesn't trick me, the gain in "I'm there" categories was to a bigger part due to having a more pronounced midrange. The otherwise deeply colored reflections from that wall (behind the speakers) didn't stain the overall soundfield. Leightweight, crunchy, accentuated I would say but not exactly lean. On the other hand, Harman suggests that tilt, so soffit mounted speakers the like might need special attention with the equalization.

 

[puppet]

I believe that the flush mounted loudspeakers use the close wall proximity like a mirror reflection. You get the sense of depth through that mirrored image. This is like the corner mounted line array. Close enough to the corner will produce faux sources. Like a woofer placed close to the floor.

 

[Putter]

As an indication of how much the room affects soundstage depth, when I listen to speakers on the pool deck which is essentially outdoors I get all the depth one could ask for.