Sound Stage - Image Question

[Brad225]

We have all heard it. Your listening to a piece of music and an instrument or vocal moves well outside where your speaker is positioned. It is obvious how you can have imaging directly in front of and any where in between the speakers but how does it move outside of them.

I know that an out of phase connection on speakers will cause the sound to be very strong to the right side and left side of the speakers with no center image.

Is the material that appears to the left and right of the speakers with proper connections nothing more than parts of the music that the mixing engineer chosen to reverse the phase of in order to gain that effect?

If not, how can music come from outside of the speaker?

 

[amey01]

It's called psychoacoustics - the little cues and whatnot. I'm sure others here will be able to elaborate, but firstly understand that the ear is only two channels, yet we can position a sound anywhere in a room - above us, below us, left, right, behind, etc. Stereo operates on two channels exactly the same as the ear and the little cues and delays that enable you to determine where a real sound is coming from enable you to determine from where a stereo-reproduced sound is coming.

 

[roberto]

It's called psychoacoustics - the little cues and whatnot. I'm sure others here will be able to elaborate, but firstly understand that the ear is only two channels, yet we can position a sound anywhere in a room - above us, below us, left, right, behind, etc. Stereo operates on two channels exactly the same as the ear and the little cues and delays that enable you to determine where a real sound is coming from enable you to determine from where a stereo-reproduced sound is coming.

Very true, and also just to add a little, one ear has a time delay of 3 miliseconds from the other. This allow us to triangle from frecuencies above 100Hz from where the sound is pruduced. Low frecuency below 80Hz we can not tell from where it is. Even the trained ears have a hard time with low frecuency. Absolute phase we can tell. You can do this very easy with ML. Postive transients and negative transients are very easy to tell. Also when you have a recording where you can not get the right stage size or the right size of the instruments and vocals. Then you change the speakers polarity (both reversed) and then you might get the right sense of stage...happy listening,
Roberto.

 

[Beakman]

A lot of this has to do with the rear reflection and how that surface(s) handle reflecting different frequencies. Play a recording featuring a single or solo instument (a xylophone is a perfect subject) scored through a wide range of octaves and you should see the soundstage expand and contract.

 

[amey01]

A lot of this has to do with the rear reflection and how that surface(s) handle reflecting different frequencies. Play a recording featuring a single or solo instument (a xylophone is a perfect subject) scored through a wide range of octaves and you should see the soundstage expand and contract.

Very true also. That was my greatest bugbear with my old room. The soundstage would move and jump around depending on frequency. A centred female vocalist was also a good subject - she'd move from left to right depending on frequency of note. YUCK!

 

[User211]

Low frecuency below 80Hz we can not tell from where it is. Even the trained ears have a hard time with low frecuency.

Conventional wisdom may say this, but I guarantee you I can always hear where my Descent is, given a track with a good amount of bass. Why is this??? I can even move it just a few inches and I know a change has taken place.

Surely conventional wisdom isn't wrong?

 

[sleepysurf]

I think room acoustics/reflections are 95% responsible for these effects, for better or worse. That's why investing time/$$ in various acoustic treatments, along with speaker positioning, is so critical.

In fact, I just discovered yet another acoustic "variable" this week. I have a 55" Sony HDTV on a cantilever wall mount. Following standard recommendations, I kept the TV as flush with the wall as possible, and pulled my Summits out as far as possible, to minimize "bad" reflections. On Wed, I pulled the TV out farther from the wall to better watch the Rays beat the Red Sox :rocker:, and forgot to push it back in. This morning, I cranked up my music, and was surprised to find the soundstage was more forward and much crisper sounding! That goes against all the usual teachings, but proves how important reflections are. I threw an acoustic blanket over the TV, and also compared with it back flush against the wall, but found I actually prefer the crisper presentation with the TV closer to the speakers! (My Summits are still > 2' in front of the plane of the TV).

 

[roberto]

Conventional wisdom may say this, but I guarantee you I can always hear where my Descent is, given a track with a good amount of bass. Why is this??? I can even move it just a few inches and I know a change has taken place.

Surely conventional wisdom isn't wrong?

Hola...that could be because you might have frecuencies above 80Hz. Remember that the cut at 60Hz does not means that you don't have any signal at an octave above (120Hz). You might have it -6dBs or -12dBs depending of the circuit cut and the crossover built in your sub, and the selected frecuency cut at the sub. Also in every room you have standing waves...and usually belongs between 30Hz to 60Hz...typical...of course when you have plenty bass energy, you could located it...but when you have a noise, like your fridge motor (compressor), or a big truck motor outside in your street, you start to walk around the room, guessing from where could be this noise, until you find it. But if the frecuency is above 100Hz, you do know right away from where it is coming from. This is my experience, and if you can do better, I really envy you (the good envy of course, LOL)...happy listening,
Roberto.

 

[Duane Rogers]

Brad 225 I've got a Carver C-1 Sonic Hologram Generator from the 80's that gives the effect you're refering to on most recordings. I couldn't find the manual but I believe it works on some method of phase inversion. Depends if you like the effect or not but I still use it,I am willing to sacrifice a little pinpoint imaging for the super wide soundstage. D.R.

 

[psychoacoustic]

yes... psychoacoustics. Very well explained above.

Sound and timing cues created within the recording mix as intentional or as a result of the reflections in the room.

I.e A soundfield of mix-down or room mix-up


Carver Sonic hologram...? I remember those days. DBX Soundfield 1's, Polk SRS's, all had an interesting approach. If I remember correctly, the DBX soundfield was oval shaped, from left/right of the speaker and intentionally prominent to the central overlap of the complimenting L/R speaker fields

* IMHO, there was a time when less channels on the mixing board was more of a benefit then a 10 feet of mix controls all fighting over the same stereo/timing cue. {wishful days when drums were real and a synthesizer = a mini-Moog}

Respect.....

 

[Brad225]

Thanks for the responses.

I moved some of my acoustical panels around to try to eliminate reflections from the mix.

In the picture there is a 5' panel to the left of the speaker covering the side of WAF TV/equipment cabinet. Directly behind the CLS is a 6' panel. To the right along the wall are 2 6' panels and in the corner is an 8' tall bass trap. The panels are all 2" 24" wide thick Owens 705 full range absorbing material. The 8' tall bass trap is triangular shape frame 26" across the face fitted into the corner filled with stacked pieces of acoustical cotton. There is also another 6' full range panel at first reflection point not in the picture.

Both sides of the room have the same treatment.

The only panels I have added is the second outside panel along the wall making the coverage 48" wide.

I tried turning the 2'x6' panels 90 degrees to the side walls in front and behind the front plane of the speakers. I placed them to the side of the CLS's as though they were attached to the wooden frame filling the space to the side wall so there could be no rear reflections.

With all of these placements of the panels there was still sounds coming from outside the speakers. Not quite as much but still 80% of what it had been. My interpretation is that I have probably eliminated the reflection issue from the equation and it's the psycho-acoustic-timing cues-phase that is creating what I am hearing.

I can understand that your 2 ears can determine where a sound is coming around you but I'm still puzzled about the ability of the speakers to create a sound real or not outside of the left and right plane of the panel.

I think it is time to type a few words into Google and find out more about how psycho-acoustics work.