Soundstage Width and Depth

Excellent answer by @millercarbon. dBA? A-weighted measurement?

No not dB-A, DBA: Distributed Bass Array. Multiple subs asymmetrically distributed around the room.

The XLO Test CD has a great imaging test track. Roger Skoff is talking in a bare room. He describes the room, dimensions, microphone placement, and where he is standing. As he talks you can plainly hear exactly what he's talking about. I mean it is like you are the microphones and he is talking at you. He strikes a calves and you hear the reverb. Then he starts walking around the room. Talking the whole time. He walks to your left, he was to your right. He walks behind you! He stands behind you and hits the clavis! If your system is mega this will blow your mind! The room he is in, and the microphone placement, the dimensions are close to the same as me in my room. So its just crazy spooky to hear. 

There's demagnetizing tracks on there too. Some decent level and channel test stuff. And several examples of really good quality recordings, including Michael Ruff Poor Boy in mono. Another good reference disk for setup and tuning for imaging.

of course this thread has devolved into a discussion about DBA, of course it has.

OP:  I find the combination of room treatment and speaker dispersion in the plane of question what affects sound stage.  That is, if you have front and back depth, having good treatment behind the listener and behind the speakers is what helps the most. Want width?  Narrow dispersion or treating walls is what helps. Height? Carpet and ceiling.

There's also a known enhancement if your speakers dip around 2.4 kHz. Wilson used to take advantage (or cheat) of this behavior, though later speakers have forgone this.

In general  you can get a really good idea of how good your system could sound with an ideal room by listening 2' from the speakers. Everything that changes between that and your listening location is due to the room.

Best,

E

@erik_squires  My listening area is my living room and I had to balance aesthetics with functionality when it comes to room treatments. They have been my best investment to date. GIK was great to work with and my sound stage, imaging and tonality were all improved beyond my expectations.

Soundstage width which extends to the outside of the speakers can be encoded on the recording, but it can also be the result of strong early sidewall reflections. The Precedence Effect is not completely effective at suppressing directional cues from significant early lateral reflections, which can tend to pull sound images to the outside of the speaker plane. Toole calls this an "increase in Apparent Source Width (ASW)", and finds that most listeners enjoy it.

But this reflection-induced increase in Apparent Source Width comes at a price, if I understand Geddes correctly, and that price is clarity and/or imaging precision and/or depth of image, assuming the latter is on the recording.

In my opinion image depth and a sense of spaciousness and/or envelopment are all related, in this sense: They are spatial cues which are on the recording itself, rather than being contributed by room reflections (as is the case with increased Apparent Source Width). When the soundstage seems to go significantly deeper than the wall behind the speakers, and/or it seems that you are enveloped in a much larger acoustic space than your room, that is not coming from the acoustic signature of your small playback room.

We can think of the spatial cues which are on the recording as being in competition with the spatial cues generated by the playback room. The ear/brain system will tend to pick whichever cues are the most convincing. Unfortunately the playback room’s "small room signature" has a natural advantage, but with good speaker setup and/or good room treatment it is possible to weaken the playback room’s signature while effectively presenting the venue cues which are on the recording (whether they be real or synthetic).

Briefly, the technique includes minimizing strong, distinct ("specular") early reflections while preserving enough reverberant energy that we have a fair amount of relatively late-onset, spectrally-correct reflections. This is a bit more nuanced than merely hitting a target RT60, as RT60 tells you nothing about what is happening early on, and it is the earliest reflections which most strongly convey the characteristic signature of a small room.

As others have noted, when you are hearing a significantly different spatial presentation from one recording to the next, THAT is very good sign. It means that the recording’s venue cues are dominating over your playback room’s signature.

Duke

Duke,

The source "appearing" outside the speakers is "encoded" in the music with either mixing methods or microphone techniques, but and it is a big but, how that appears on playback is highly dependent on speaker, listening position, microphone or mixing technique and very important the listener themselves. The microphone technique or mixing (playing with timing) can have more impact on perceived playback that anything to do with the venue.


Keep in mind that how this works is not by recreation of a real source outside the speaker as would be the case with a first reflection, but by tricking the brain with a delayed signal from the other speaker hitting the opposite ear to generate timing information that the brain may perceive as equivalent to the timing information of a sound wrapping around the head to determine direction. Not everyone interprets it the same and the effect can be positive or negative and is influenced it appears by individual interpretation of timing and volume cues for direction, not to mention what works for one recording on one system could fall apart completely with a different recording or system. 


For those discussing "height", we have a hard enough time getting height in a real 3d environment. Nothing that comes out of your speakers (in a single plane) is height beyond that your room acoustics may generate and it would bear little reality to the actual recording environment (if it had any height at all in the first place).