Jim Smith’s Magic Formula for Speaker Placement

Discussion in 'Audio Hardware' started by LeeS, Nov 13, 2022.

  1. SpeedMorris

    SpeedMorris Forum Resident

    Location:
    Iowa
    As luck would have it, my Diamond 225 tweets are 74" apart, and my ears are 89" away from them. 83.15". Not on purpose. Must indicate golden ears.;)

    It's more like an 85% deal in the next room. Nobody's perfect.
     
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  2. theclipper

    theclipper Forum Resident

    Location:
    Seattle, WA
    I still haven't been able to get the 83% to work with my Spatial Audio Sapphire M3's. He also notes that the minimum listening distance shouldn't really be less than 9 feet in the book. So which one is more important?
     
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  3. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    Then he is essentially saying no nearfield listening. That's just plain wrong.
     
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  4. NoBody99

    NoBody99 Forum Resident

    Location:
    WV
    is the 9' one speaker to ear or speaker plane mid-point straight back?

    If to ear d = 9
    Plane d= 8.2'
    Speaker to speaker d = 7.5'

    If to plane d = 9'
    to ear d = 9.9'
    Speaker to speaker d = 8.2'


    I tried it, slid the couch up
    Speakers 8.2
    To ear ~10'
    0.82

    It did seem more enveloping, less sidewall reflection?
    I increased toe-in a bit.
    Normal I sit ~ 11' or 8.2/12 ~ 0.68
    I'm not sure if I liked it better but will try it some more. It does seem 'cramped'.

    Wife just looked, chuckled, and strolled away.
     
  5. theclipper

    theclipper Forum Resident

    Location:
    Seattle, WA
    I believe he is talking 9' minimum from tweeter to ear.
     
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  6. Tony C.

    Tony C. Forum Resident

    Location:
    Portugal
    That's what I infer, as well, and mine happen to be almost exactly 9'.
     
  7. LeeS

    LeeS Music Fan Thread Starter

    Location:
    Atlanta
    I think Jim Smith in many ways has found a one size fits all…at least in terms of 83% getting it down to a very small area of adjustment.

    It’s really a distillation of thousands of very careful room setups. So we are getting a free ride on Jim’s deep experience in a way.

    Room acoustics are definitely critical but that’s a next step.
     
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  8. NoBody99

    NoBody99 Forum Resident

    Location:
    WV
    But the bullet, rearranged my speakers (and couch) to burn some Turkey calories off. I'm thankful for my brothers daughter having the feast. Rugrats EVERYWHERE! lol

    speakers ~ 7.9' apart
    ear ~ 9.5, ratio = 7.9/9.5 = +/- 0.83

    Focal method
    A = 42 to front wall
    B = 35 to sidewall
    C = 29.5 woofer to floor
    B^2 = A x C = 35^2 = 42 x 29.5
    = 1225 = 1239, very close ~1%

    Vandersteen odd numbers
    L = 378 / 9 = 42, placement 42
    W = 165 / 5 = 33, placement 35

    listened to 1 lp so far. Sounds good. Better? Time will tell.

    It moved me closer to the TV so I looked at recommended distances on online calculators. 65" TV
    4k 4' !
    1080i, 8' (range 4 - 12 depending on source)
    I'm at 11' and it does look better.

    The Ideal Distance for TV Viewing
     
    Last edited: Nov 24, 2022
  9. NoBody99

    NoBody99 Forum Resident

    Location:
    WV
    This has likely been posted. A first reflection point calculator. It can also be used to adjust for example, the 0.83 ratio. You can play with it to see how different layouts move the reflection points around.

    Locating areas of first reflections
     
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  10. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    Good to know first reflections but it's really important to know the radiation patterns of the speaker too.
     
  11. NoBody99

    NoBody99 Forum Resident

    Location:
    WV
    Many variables:
    RT60
    Dispersion
    Room modes
    et al

    All speakers follow the inverse square rule and radiate in a somewhat spherical pattern. But attenuate off axis to varying degrees.

    And the first point doesn't change on that (does it even shift with toe-in?).
    But if the point is 20 deg off axis and one speaker is -15 dB and another is -20 dB, the first will reflect more energy but the point will provide maximum absorption for any speaker. It's fixed by geometry.
     
    Last edited: Nov 25, 2022
  12. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    Attenuation happens widely varying degrees and with substantially different spectral content. An Omnidirectional speaker like an MBL is going to have a radically different reflection pattern than a very narrow dispersion planar speaker. And if we are talking about speakers designed through the HK testing facility we are talking about speakers likely designed to sound their best with the first reflection points untreated but the room diffused. It does matter. This one size fits all approach does not work well for all sizes.

    Room modes are a different issue.

    Depends on the radiation pattern


    But you have to consider spectral content and design goals of the speaker designer or your absorpion runs the risk of becoming a passive equalizer.
     
  13. Tim 2

    Tim 2 MORE MUSIC PLEASE

    Location:
    Alberta Canada
    I've never been a fan of nearfield listening. I suppose if you have a horrible sounding room then the closer to the speakers the better.
     
  14. Tim 2

    Tim 2 MORE MUSIC PLEASE

    Location:
    Alberta Canada
    Yes minimum. I prefer to be about 12' from larger speakers.
     
  15. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    Near field allows you to utilize a smaller room but it doesn’t fix a bad room. Some speakers start to roll off as you get out of the near field. I’m not going to dispute anyone’s preference against near field but technically it works very very well and with many speaker designs gives you the most accurate sound from your speakers.
     
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  16. Tim 2

    Tim 2 MORE MUSIC PLEASE

    Location:
    Alberta Canada
    Agreed, but I find my fairly big ( 177# ) floor standing speakers need room to breathe and blend to get a balanced frequency response. Sitting about 12' away is optimal here.
     
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  17. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    If they are multi-driver speakers they do generally need some distance. Floor standing planars tend to do very well relatively near field as do smaller monitors
     
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  18. NoBody99

    NoBody99 Forum Resident

    Location:
    WV
    You are over thinking this. You can use rules of thumb to get close but you must listen to find what you like best. You can do sweeps, FFT, etc. Far too many variables to model. Not to mention atmospheric conditions, altitude, etc.

    The room geometry and functional use also an important factors. Not everyone can put speakers 1/3 into the room.

    For a standard box speaker you can look at dispersion plots for <10 kHz and +/- 20 deg and you will not see much difference. If you do the designer failed.
    At 10' 20 deg is +/- 7' window.

    I do not plan on using room treatment. If I can move a plush chair into the spot or locate a glass table so the 1st point is under it, not on the surface, that is good enough for me.

    People have different goals, I do not want a studio environment, although some treatments attempt to be aesthetic.
    I opt for 80% with 20% of the effort rather than 90% with 80%.

    Nothing wrong with going the extra mile but not my 'thing'.

    A couple of improvements (?) after the move. Less modes at the LP. A small shift of my table got it out of 'the line of sight', the first point is under the center, it also out some natural absorption at the wall first points.
    I need time to see if it is 'real' or placebo.
     
    Last edited: Nov 25, 2022
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  19. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
     
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  20. Redd House

    Redd House If she dont love me no more I know her sister will

    Location:
    Henderson, NV
    I've got mine at 83% with 7'-10" tweeter to ear and toed in. I'll try 9'-0" tweeter to ear but that's going to spread the speakers pretty close to the Kallax banks on each side of the room.
     
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  21. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas

    I promise you I am not over thinking it at all. The differences are both easily heard and easily measured to correlate to what is heard. These things matter a lot.


    Rules of thumb may or may not get you close. You won't know and trial and error is remarably inefficient. You could be looking for the proverbial Easter Egg in the wrong yard and not know it. You must listen to decide what you like best but you must measure to find your way there. And understand what the measurements are telling you. You can get a full frequency impulse response measurments that will tell you with amazing precision what you are actually hearing. And with that it is much easier to figure out what you like.



    OK which one Failed? Magnepan or MBL? Their dispersion plots are going to be way more different than what you just cited. So which one failed?


    That may be good enough for *you* but it isn't "good" A plush chair is just about the opposite of a well designed and controlled absorptive panel with a known absorption coefficient. It's not going to work well at all unless you get real lucky. It's going to be one of many steps in creating a room that is acting like a random passive equalizer. I'm sorry but that is really a terrible way to deal with room reflections. I wouldn't even say it's better than nothing. Maybe maybe not. That's how uncontrolled that tactic really is.


    Yes, people have different goals. Allthe more reason one sizze fits all solutions don't really fit all

    Whatever "your thing" maybe is your choice. What you personally like is cool. But let's not confuse that with some universal standard. The ideal room is not created by rules of thumb or plush chairs.

    And you really don't need anytime to figure out if changes are real or placebo if you are measuring the room as you go along.
     
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  22. Nascimento Brasil

    Nascimento Brasil Forum Resident

    Location:
    Sao Paulo/Brasil

    Bill, Jim just replied to my email, he will start selling PDF copies of the book, soon it will be available on the site!
     
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  23. Tim 2

    Tim 2 MORE MUSIC PLEASE

    Location:
    Alberta Canada
    Don't most speakers use " multi drivers " ?
     
  24. Bill Hart

    Bill Hart Forum Resident

    Location:
    Austin
    Congrats!
     
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  25. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Las Vegas
    My old ldSound Lab A3s are single driver and are close to 6’6” tall and 3’+ wide. They were great from 6’-7’ away
     

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