Basic stereo setup, how do you do it, what is important to you?

[DonH50]

Laser rangefinders, or laser pointers? If the former, what make, model, and price range have you found for laser rangers? I did a quick search and found a bunch ranging from ~$20 to several thousand dollars (USD). I would like to have one before I mount some additional ceiling panels, but need to ride the line between quality and affordability... Tnx - Don

 

[RBFC]

As to "anal" setup, carefully considering the placement of speakers, etc.: Let me pose this question:

If Steve's Wilson speaker enclosures had just a "bit" of vibration, if his tape deck had the heads misaligned just a "little", etc. don't you think the results would be less spectacular? The hallmark of a craftsman is to take precision and accuracy a step further than average. I'd say that not all others who enjoy Steve's compliment of equipment achieve the same results in their room due to less attention to detail.

I use a laser pointer, a level, a metal tape measure, and tape placed on the floor to assure the placement of my speakers. I can't tell you how many times I've held one end of the tape measure by my head while my wife or friends held the other end to assure accurate speaker placement. It's like gapping your spark plugs "sorta" near the recommended spec. All that money you spend in quality reproduction equipment can be partially wasted by lackadaisical setup work.

Lee

 

[DonH50]

I'm a design engineer. Anal is a way of life. However, I also have to assess what matters given all the other factors in play. Including moving one's head. As I implied earlier, that does not mean one should not strive for perfection in all the details. However, in your example, vibration in the speakers or a misaligned head would cause a lot more problem than being 1 mm off in placement, IMO. Some of this has to be relative...

 

[garylkoh]

Accuracy is absolutely critical. I use a Bosch DLR165 laser rangefinder - accurate to 1/16th of an inch. It's available from Amazon for between $90 to $180 depending on the stock they have. There is a cheaper version the DLR130 - but I am not sure what the difference is.

You have to get within 1/16" for proper imaging. Here's a fun exercise. Close your eyes, and have someone stand 10ft away from you speak to you. You can point to her (with your eyes closed) with uncanny accuracy. Still have your eyes closed and have her move sideways. See how much of a move she will have to make before you can tell that she has moved.

Lab experiments have shown that the majority of test subjects can tell if the movement is less than 4-inches at 10ft. If the distance between the ears is 6 inches, what is the change of the source distance between the 2 ears if the source moves 4 inches sideways?

 

[Gregadd]

Laser rangefinders, or laser pointers? If the former, what make, model, and price range have you found for laser rangers? I did a quick search and found a bunch ranging from ~$20 to several thousand dollars (USD). I would like to have one before I mount some additional ceiling panels, but need to ride the line between quality and affordability... Tnx - Don

Range finder- long distance for hunters and golfers.
Laser pointer for teachers and business meetings.
Laser measure- for carpenters and such. http://www.stanleytools.com/default...tMax™+Tru-Laser™+Distance+Measurern Can probably double as pointer. This is the one you want. As low as $99.

Because you teach probably tax deductible if used in class.

 

[DonH50]

Thanks for the info, both of you -- I think I'll go identify my birthday present this year! I do (did) not distinguish between range finding and measuring... I thought perhaps Steve et. al. were using a laser pointer for alignment, then measuring with a tape (or whatever), but figured it had to be a laser measuring device of some flavor. I last looked a few years ago and it was around $300 for one I thought was worthwhile, but prices have dropped as they have become more popular.

I have a hunting buddy with a nice range finder (another guy who likes the best of everything); never thought about hunting golfers.

I don't teach much -- just invited lectures at the local college and a conference or two, plus a few trumpet students now and then (none this year as work absolutely killed me last year and through the first part of this year; can't teach and work 60 - 80 hours/week).

Thanks - Don

 

[Gregadd]

never thought about hunting golfers.

Don -according to Tigers' ex wife it's better done with a golf club.

 

[RBFC]

I'm a design engineer. Anal is a way of life. However, I also have to assess what matters given all the other factors in play. Including moving one's head. As I implied earlier, that does not mean one should not strive for perfection in all the details. However, in your example, vibration in the speakers or a misaligned head would cause a lot more problem than being 1 mm off in placement, IMO. Some of this has to be relative...

As I was making a point, I mentioned the above imperfections as a means of illustration only. I did not intend to imply that the relative contributions of each "problem" were equal.

It's refreshing to hear you say that we should strive for perfection. Many of the comments coming from the "engineering" viewpoint seem to have shown an interest in getting things "good enough" so that they are inaudible. The fallacy in that approach is that NONE of the described inaccuracies in audio equipment stand in isolation. A small phase/timing error in the alignment of the drivers in a speaker may be hard or impossible to hear.... couple that with an error in placement that increases timing/delivery errors and smearing, etc. may be the result. Therefore, I'd still submit that we should strive to eliminate as many compounding, confounding factors as possible when setting up a system.

Lee

 

[DonH50]

Lab experiments have shown that the majority of test subjects can tell if the movement is less than 4-inches at 10ft. If the distance between the ears is 6 inches, what is the change of the source distance between the 2 ears if the source moves 4 inches sideways?

A challenge! I’ll play…

I’ll work in inches, so 10 feet is 120”. Starting with the person directly in front, the distance to each ear is 120.037494” assuming ears 6” apart. At 1127 fps, TOA is 8.87588688 ms to each ear.

Now move her over 4” to the left, still 120” away. Distance to the left ear is 120.004167”, with TOA 8.87342255 ms. It’s now 120.203993” to the right ear, or 8.88819826 ms, a difference of 0.0147757 ms (about 14.78 us).

I am impressed! Assuming I did the math right (I did not double-check it), that implies we can resolve a time delay of under 15 us, much less than I would have guessed, and the difference in distance to our ears in the latter case is only 0.200”, or 1/5”. Not quite 1/16”, but very small relative to everything else. I still wonder how much that matters in the real world with music, room interaction, and listener movement, but something to think about. Music has much higher-frequency signals than average speech, making time differences (and thus positioning) more critical, one would think.

A range finder it is for me this year… - Don

 

[DonH50]

never thought about hunting golfers.

don -acoording to tigers' ex wife its better done with a golf club.:d

lol!

 

[DonH50]

Lee,

Yes we agree. That bit about "given all other factors" is important, and your point about operating in isolation makes my comment explicit. Nothing works alone! A circuit with a thousand transistors (small potatoes today, but I am an analog designer so not atypical for me) will probably work OK if one is off by 1%. Shift them all 1% and there's trouble. Design is an exercise in optimization of all variables for the best performance under all conditions, and that indeed requires each device, cell, block, etc. to be as close to perfect as possible. I can cite numerous examples of bad things happening when one little detail is overlooked. In my stereo, the image suffers a bit; in my job, a $1M mask set may be trashed, or the shuttle may fall out of the sky because the Ku-band radar (which I worked on) misplaces a bit of debris in orbit.

Which serves as a reminder that, even though the consequences of misaligned speakers are much less dire, that does not mean I should neglect it, nor belittle those who are "anal" about it. To paraphrase, the real question may be -- why am I not?

Point made, Lee et. al., thanks. - Don

 

[Gregadd]

Don I used a mono source and measured to the front of the head and got a difference .067 inches with three significant digits. I guess I have to stay after class. I think Ethan posted a graph on this subject.

 

[DonH50]

I did say I did not check my numbers... Let's see:

1. Reference, subject (source) centered 120" away, 3" to the side of each ear means distance of sqrt(120^2 + 3^2) = 120.0375"

2. Keeping 120" perpendicular in front but moving over 4" puts the source 1" to the left of the left ear: sqrt(120^2 + 1^2) = 120.004" to the left ear.

3. The right ear is now 7" over from the source so I get sqrt(120^2 + 7^2) = 120.204" from source to right ear.

4. The difference in distance to each ear is (120.204 - 120.004) = 0.200" with the source moved over 4". That changes the time delay (time of arrrival, TOA) from source to ear, and allows us to perceive relative position. Zero difference in distance means zero difference in time, and the source is dead in front of us. Move it a bit, and our ears catch the time delay and our brain tells us which way the source moved.

I think.

Hopefully somebody can jump in and tell me what I did wrong... - Don

 

[Gregadd]

Ok I see. I measrured from the front of the head. Should have gone on to EE school.

 

[DonH50]

Nah, just have to 'member that HS geometry class for this one. If it needed more than right triangles, though, I'd have to grab a book to look up the triangle relationships! - Don

 

[garylkoh]

4. The difference in distance to each ear is (120.204 - 120.004) = 0.200" with the source moved over 4".

Don is correct - 1/5". The majority of subjects can detect that difference. Some subjects can detect a change as small as 1" side to side.

Now, move one of your speakers forward by 1/5" - and find that the center image has moved by much more than 4" if you are sitting in the near field.

Next exercise - if the wave length of middle C is about 4ft, what phase error between the two speakers would result in a diffused image and soundstage?

Given that capacitors used in crossover networks are +/-20%, how close do each component in the crossover have to be matched, and how close do drivers have to be matched?

Since most manufacturers do not match to such tolerances, it can be easily shown that getting the measurements absolutely correct would still not give you the perfect image. You have to shift the speakers around, and that's assuming that the recording you use has an absolutely centered center image.

Using a mono recording will work only if the room is sonically perfectly symmetrical - I say sonically because a lot of rooms I've been to that look symmetrical are not sonically symmetrical because of air conditioning ducts, wall material, and what is behind the wall.

 

[DonH50]

Thanks Gary, at least something went right today!

Now, for the life of me I can't see how a slight displacement would do more than shift the image slightly to one side or the other in the absence of other artifacts (e.g. room reflections, etc.) I can align everything, apply a mono source, and I should get a perfectly centered tone (or source, whatever). If I move a speaker back and forth, I can shift the image's perceived location, presumably due to a combination of time and amplitude change caused by moving the speaker. Is the goal then to correctly place the image with respect to the recording, or is something else going on as well?

Note: This is a difficult test to perform in a room due to all the reflections and such. Moving the speaker may change the sound field via various interference effects. Also, one could argue that volume must be matched after moving them, but to me that's part of the error if you move a speaker so I include that in the image displacement effect. My room is pretty well damped so I think it provides a reasonable test case. Besides, it's my room, where I care most about the sound!

One other question: my AVR (Pioneer SC-27) includes group delay compensation (over frequency, per speaker), and I assume Audyssey and other similar systems do as well. I did not check (nor am I sure it is stated) what resolution of control is provided, but generally speaking do these schemes provide sufficient range and resolution to compensate for typical speaker displacement?

I am pretty sure most people do not position their speakers so accurately, and I wonder what they (and I) am missing. This has me interested enough to play around with my speakers a bit and take a few more measurements to see what happens. I admit I did not expect such small numbers in time and space...

Curious,
Don

p.s. I was typing as you were so some of this you have addressed... Tnx - Don

p.p.s. If a mono recording won't do it, and perfect positioning by measuring won't because of component tolerances, how do we determine when the speakers are perfectly positioned? What do we listen to and/or measure?

p.p.s. I could stick my hand up to answer your other questions, but time to give somebody else a chance...

 

[garylkoh]

The jury is still out as to how our brains localize sound. All scientists know is that they now know that there is much more that they don't know.
http://www.aip.org/pt/nov99/locsound.html

One example is that the auditory nerve disappears into six areas of our brain - and the processing is so complex that hair cells in the ear cannot be replaced because it would take the brain years to figure out how to process the input from new hair cells.

My speaker set-up process is a lot of iteration between measuring, listening, measuring and listening - to a fixed set of music that I have used over and over again consistently for years. If you're interested, here's a link to my procedure (including the music).
http://www.genesisloudspeakers.com/whitepaper/Genesis_Loudspeaker_Setup_Procedure.pdf

I've done this as a training session for the Pacific Northwest Audio Society exco members - and it works.

 

[terryj]

Next exercise - if the wave length of middle C is about 4ft, what phase error between the two speakers would result in a diffused image and soundstage?

.

hi gary, have not bothered to work it out but off the top of me 'ead I'd say about 0.7 degree haha.

Thanks for the link, it is saying a LOT about the things I was going to mention. They were very surprising to me, so much so I wanted to share with this thread. It is good to see my thoughts being set down far more rigorously in your paper.

I need to run a few measurements tonight, so will try and illustrate with pics soon.

My only 'concern' with using tracks and saying 'this is what should happen' is that (not you, but I'd love your reaction to this) *we* get used to 'our sound'. And, being arrogant bunch that we are, what we hear is, naturally, correct. Hence, if another systems does it differently the danger is that it (when it might be right) can be labelled wrong, because it is not how ours does it.

I don't have a way out of this problem, hope others can steer me correctly!

 

[DonH50]

Hmmm...

Middle C = 261.63 Hz so at 1127 fps the wavelength is 4.3076’ = 51.69”
Assuming we resolve to 0.200”, then 180 deg x 0.2" / 51.69" = 0.696 deg

Pretty impressive! See, others can do math, too!

Gary, thanks for the links, I will download them post-haste. Thinking a long way back, in the 80's there was a lot of research and I think time of arrival and amplitude were the main factors? Not completely sure... I do know binaural was coming into vogue (again) and so a lot of research into how we "place" objects was being done. The one thing I recall clearly is that the earliest sound determines location and later (reflected waves) tend to be ignored (suppressed, whatever); equal arrival and equal loudness "confuses" us but is the thing that makes stereo work (that's what provides a "phantom" stable center image from two speakers off to the left and the right). There's a name for it but I can't recall... "prescience" isn't it, but something like that. Senility!

I'll also download your setup procedure and give it a go; nice to have one from an expert! This has got me excited about trying something old made new again. - Don