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[Etch-A-Sketch]

Hi, I figured this would be the place for a question like this.  I started looking on AES and did a couple quick searches here and couldn't find anything...

someone asked me about positioning speakers.  I said usually you have them equidistant to you and each other (equilateral triangle) and then also said that the THX standard has them at 30 degrees (instead of 45) off center and each speaker should be the same distance to the listener.

So then this person asked why?... and I said for stereo imaging... but then he asked, well how do you know that 30 degrees and/or 45 degrees is optimal for stereo imaging? why not something else like 60 degrees?  And I said, "well that was what I was taught in college *shrug*"

I explained how as the speakers get further apart you start to lose the center a little bit and panning across the center gets less defined...   so then he asked me if there has ever been scientific testing for this to determine that 45 is truly optimal or if 30 is better for imaging, etc...  I looked and couldn't find anything... Anyone have any information on the subject?  Now I want to know!!!

Fran and others, do you keep any of this in mind when designing rooms and placement for the speakers?

[Die BREMSSPUR]

Howdy,

In a lot of big rooms the soffited mains don't seem to be at a very extreme angle from the pictures.

If you are not installing the speakers in a wall, why would you care what angle they were at?

I would guess that it depends on the room, your speakers, your personal psycho acoustics, preferences and where the lava lamps look best...

I read on this forum about the Adam S-3A's having "hype" and that someone positioned their listening position in front of the converging "sweet spot".

Now I haven't heard any "hype" but I'm an idiot.  I have experimented with pointing the speakers straight rearward and then crisscrossing at an angle behind my noggin.  Right now I have them higher than my head and pointing slightly rearward.

You also have the distance your head is away from them as well as how far they are from the walls, the stands (very fukken important) and the room treatment....

I would tell your friend to forget about any preconceived notion and to experiment because that's why we have studios...

I would also think that the ability to hear things like the room and reverb or tonal characteristics are just as important if not more so than the stereo image.....

Would like to hear your thoughts....

lemme nough

tik

[PookyNMR]

Good question, Derek.

[Ethan Winer]

Derek,

> So then this person asked why? <

So did I. A few months ago I asked exactly the same question in the alt.sci.physics.acoustics newsgroup. Not sure there was much resolution, but below is that exchange.

--Ethan

Quote:

Folks, The standard recommendation for a two-channel listening setup is to create an equilateral triangle between the listener's ears and each speaker. That's always worked fine for me! But someone recently asked me WHY this is the standard setup and I had no answer. Is there a historical reason? Was this determined empirically with listening tests? Is there something obvious I'm missing? Thanks. --Ethan ================================ I just seems natural. There was a center channel in many setups long ago. How its recorded and played back is different from when they first started stereo. Now we have 7.1. I'm waiting for 9.1, with top and bottom, ans 10.1 with vibration. greg ================================ Well I guess its just for simplicity. Keeping the speakers at equal distances from the listener means a  simpler recording and/or play back setup is needed to capture and then reproduce the psychoacoustical trick known as stereo. If you had two sound sources at different distances from the listener (scalene triangle), then there would necessarily need to be delay introduced (either during play back or recording) to produce the desired stereo image. Chris W ================================ Chris, > If you had two sound sources at different distances from the listener < I guess I wasn't clear enough. Of course both speakers must be the same distance from your head. But the "standard" is to have the speakers the same distance from you as between each other. That's what I'm really asking about. Obviously the speakers shouldn't be two feet apart if they're ten feet in front of you. Likewise, ten feet apart is probably too much in a nearfield setup. But why is the "rule" to have all three sides of the triangle the same? --Ethan ================================ I think what your asking is more related to the theory of stereo imaging and how the brain reconstructs spatial information from two (or more) complimentary sound sources. Maybe information on http://www.stereosoundbook.com/ would help here Chris W ================================ Back in my audiophile days I used to experiment a lot with speaker placement.  I found that the distance between the speakers was critically related to their toe-in, and that both had an effect on the imaging ability of the system. I found that there was a compromise between a wide, spacious soundstage and a rock-solid center image. I also found that moving my head a few inches right/left and forward/backwards made a significant difference in the soundtage solidity, and that the lessons learned could be aplied to improving the speaker placement. I ended up trying to make the high-pitched tones from particular instruments line up horizontally with the fundementals from the same intstrument, and found thta this was a good technique for arriving at a compromise. If I got everythng right, the soundstage had significant depth as well as width. The equilateral triangle is just a rough starting point. ================================ I think that is has to do with the angles involved, remember that an equalateral triangle also has equal angles, those being 60 degrees each. Placing the speakers so that the angle formed at the listening point of the triangle is 60 degrees and equidistant to each speaker means that the other two angles will be 60 degrees as well, and this results in an equilateral triangle. This is however, just a rule of thumb, and depending on the type of speakers, the room acoustics, etc, other placements may suit just as well or better. For near-field speakers though, that rule probably works very well in most situations.

[Etch-A-Sketch]

Die BREMSSPUR wrote on Wed, 06 December 2006 03:42

If you are not installing the speakers in a wall, why would you care what angle they were at?

Well, regardless of sofit mounting or stand mounting, the distance between the speakers in relation to the distance from you will effect your stereo imaging.  so will reflections around the room and such that you have also mentioned...

Also, by angles I am not refering to the direction the speakers are pointing.  Sorry about the confusion on that... I'm talking about the geometry of where the speakers are placed in relation to the listener and the distance from center.  This is not regarding whether the speakers are pointing straight at the far wall, or spun inward a little bit to aim directly at the listener.

For example... draw an imaginary line from your listening position straight ahead.  Then draw a line from your listening position to your left speaker.  Now using the center line as 0 degrees, with a compass what is the angle of the line going to the left speaker?  do the same for the right speaker.

[Etch-A-Sketch]

Etch-A-Sketch wrote on Tue, 05 December 2006 13:37

Hi, I figured this would be the place for a question like this.  I started looking on AES and did a couple quick searches here and couldn't find anything... someone asked me about positioning speakers.  I said usually you have them equidistant to you and each other (equilateral triangle) and then also said that the THX standard has them at 30 degrees (instead of 45) off center and each speaker should be the same distance to the listener. So then this person asked why?... and I said for stereo imaging... but then he asked, well how do you know that 30 degrees and/or 45 degrees is optimal for stereo imaging? why not something else like 60 degrees?  And I said, "well that was what I was taught in college *shrug*" I explained how as the speakers get further apart you start to lose the center a little bit and panning across the center gets less defined...   so then he asked me if there has ever been scientific testing for this to determine that 45 is truly optimal or if 30 is better for imaging, etc...  I looked and couldn't find anything... Anyone have any information on the subject?  Now I want to know!!! Fran and others, do you keep any of this in mind when designing rooms and placement for the speakers?

I also realize I made a mistake in my geometry...Doah!!!  30 degrees off center is the equilateral triangle... 45 degrees off center will yield a greater distance between the speakers than the speakers are to you (which I have seen in quite a few studios).  

Sorry 'bout that.

[Etch-A-Sketch]

Thanks Ethan!  I'll look into getting a copy of "the Stereo Soundbook".  It sounds very interesting.

[franman]

I'll chime in on this one>>>.

Look, we use equalateral triangle as a "Golden Rule" of sorts.. In other words, all of our designs start with what equalateral triangle (or 5.1 setup in a circle with ITTU speaker angle placements which include 30/0/30 for L/C/R) speaker layout.

Why?? Because that's what puts us on axis with a speaker that we assume we like, and that sounds most accurate on axis. It also is one of the precepts that the center "phantom image" in stereo reproduction is based upon.. If the triangle gets too wide than you feel as if you are in a hole in the middle of the image, and panning is exagerated.. If the triangle is too narrow, than you will exagerate all of your panning in an effort to setup a wide enough stereo field.

Rules: Yep, the mans right... there are now rules in Rock N Roll.. so, experiment at will and find what works for you... but I'm telling you that ALL of our in-wall monitor system are based on equalateral triangles that focus somewhere between 12" and 24" behind the armrest of the console.. why? because at around 12" of "overshoot" your ears are just about in the direct path of the speakers.. further back, widens the sweetspot (for larger triangles 9-11 feet) without putting you in the hole I described above. This is all based on our experience doing this several hundred times in good rooms, bad rooms and everything in between!! I will tell you in no uncertain terms that the SINGLE BIGGEST THING YOU CAN DO TO TUNE YOUR SYSTEM, is experiment with speaker placement:
1. Start with positioning the pair for "optimal" bass response (that's a big statement right?).. what sounds best and/or measures best for YOU..
2. tweek speaker toe-in angle and fine position adjustments to tighten up the stereo image.. when your mono is rock solid and the speakers "dissappear" and your sound stage opens up, that's when you've got it right! we're talking critical listening hear guys..
3. finalize toe in to control HF response to taste.. totally on axis should give the most and flattest HF response, all other variables being equal..

Yes, I'm ignoring the room for this discusssion because as I've said, this is what we do in room after, room, after room and it works.... at least for Lars and I...

fm

[Barry Hufker]

I'm no expert, but it seems to me that if you sent pink noise through both left and right, you could spread the speakers until there is a 3,4.5,6 dB drop in the center (between the speakers).  Then that ought to be a smooth transition between the left and right.  Why 3, 4.5 and 6?  Because if a combination of both channels results in + 6dB-spl, then dropping 6 dB ought to reduce that build up in the center image.  But it could be that a drop of 3 or 4.5 dB might sound better.

Am I wrong??

Barry

[Yannick Willox]

It gets more complicated when using panning versus classical stereo pickups. Eg. Blumlein sounds better when replayed on a 90deg spaced system, than on a 60deg system.

That is a pity, since most "audiophiles" are actually listening to narrower setups than the 60deg standard.
My speaker setup is around 52 degrees. Why ? I prefer the flatter roomresponse and better imaging above the "correctnes" of the 60degrees.

For most sources, 60 degrees actually sounds like the maximum to me. Also, do not forget some speakers have a on-axis HF boost to compensate for the narrower dispersion at those frequencies. It's better not to point those directly at the hotspot.

[jetbase]

franman wrote on Sat, 09 December 2006 15:25

1. Start with positioning the pair for "optimal" bass response (that's a big statement right?).. what sounds best and/or measures best for YOU..

Is this what Room Optimizer helps with? Does anybody provide a service where you can give them your parameters & they provide you with speaker positions (as a starting point, obviously)?

[Barry Hufker]

Take a look here:

http://www.rpginc.com/products/roomoptimizer/index.htm

Barry

[Yannick Willox]

I used this to optimise my speaker positioning:
http://www.cara.de/ENU/index.php?load=cara-raumakustik-simul ation.html

[franman]

Cara and Room Optimizer can both provide good, valid starting points. I have actually had amazing experiences with rectangular rooms and Room Optimizer's ability to nail the LF response in the room very closely. (Of course not roomw we designed, as these ALL have nice flat LF respones - LOL)... Cara is a very strong program, but our biggest gripe is that it doesn't allow you to "add" trapping into your designs. The wall is the wall, and you can give it a Coefficent of Absorption, but sometimes, a wall is not a wall (like when you have 3ft of porous absorption in front of your multiple layer drywall partition).. anyway, both great programs and useful by professional and room "users" alike..

[Yannick Willox]

In Cara you can make custom materials and then stick a object or surface to a wall that will have the specs of your basstraps.

Likewise you can have windows in a wall, which Cara treats as some sort of panel absorber.