Jim Smith’s Magic Formula for Speaker Placement

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

  1. Nascimento Brasil

    Nascimento Brasil Forum Resident

    Location:
    Sao Paulo/Brasil
    I don't know where you got the idea that I came here on business or that I'm looking to save on shipping! I just think it's smarter to download it and store it on an ipad! The world has to move forward, no more cutting down trees!
     
    timind likes this.
  2. Bill Hart

    Bill Hart Forum Resident

    Location:
    Austin
    Ah. Well, I didn't know if you came here on business, it was really a question. I take your point about paper. I read most stuff on Kindle because the print is too small for me to read on most trade paperbacks. If a book is "special" I will buy the hardback, but gone are the days when we accumulated bags and bags of books to try to donate to the local library (they rarely wanted them).
     
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  3. Nascimento Brasil

    Nascimento Brasil Forum Resident

    Location:
    Sao Paulo/Brasil
    Today, the only thing I'm interested in accumulating, is friends and LPs!
     
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  4. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    but how do you position the chair first?
    The speakers are not yet positioned and they need to be positioned before you measure / evaluate the bass response.
     
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  5. My calculations stated and quoted that 80/98 (82%) sounds really good, however I've noticed that when I lean forward as little as 2 inches, it sounds even better. So 80/(98-2) or 80/96 which is 83%.

    Next step will be to move the couch ahead 2 inches.
     
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  6. Mike-48

    Mike-48 A shadow of my former self

    Location:
    Portland, Oregon
    Slightly OT -- Where did the oft-repeated recommendation come from to sit on an equilateral triangle with the speakers (Y = X)?
    I have set up systems through the years and always preferred the sound further back. I thought it was my particular situationd or ears, as one keeps hearing, use an equilateral triangle. Where did that ever come from? Is there any data behind it? Anyone know?
     
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  7. ayrehead

    ayrehead Forum Resident

    Location:
    Mid South
    :shake:
     
  8. Paul Saldana

    Paul Saldana jazz vinyl addict

    Location:
    SE USA (TN-GA-FL)
    I own four subs, my main system has two of those.
     
    bever70 likes this.
  9. Rick58

    Rick58 Forum Resident

    Location:
    Eagle, ID, USA
    I don't know but think it's just "a good starting point" ... I usually use Cardas's method then tweak from there.

    Actually his nearfield setup IS an equilateral triangle ... Room Setup: Near Field
     
  10. macster

    macster Forum Resident

    Location:
    San Diego, Ca. USA
    Leave me alone, I'm trying.

    :cry:

    M~
     
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  11. Doctor Fine

    Doctor Fine "So Hip It Would Blister Your Brain"


    It goes back to the very beginning of stereo and yes I was THERE when it happened in the 50s. It was posted on the back of early stereo record albums. 90-degree placement for two channel was pretty well accepted as a "pro" distance. Seriously, it is a common starting point and has been forever since my days reading Layfayette and Allied Radio catalogs. Hey Crutchfield recommends it so you can't go wrong with Crutchfield, can you?

    No mention is made of the type of room that needs 90 degrees because it is a compromise number. In a truly large, long room you would probably like to take advantage of sitting a bit farther back to hear a farfield presentation. So I totally "get" Jim's 83 number because he works in truly large rooms, But in a small room or on a desktop you probably want to sit closer and the image widens out to 90 or wider to be able to pick out details in the mix like you are sitting in the front row hearing individual instruments.
     
    progrocker likes this.
  12. Mike-48

    Mike-48 A shadow of my former self

    Location:
    Portland, Oregon
    There are no 90-degree angles in an equilateral triangle. I'm missing something! Did you mean 60 degrees?
     
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  13. LeeS

    LeeS Music Fan Thread Starter

    Location:
    Atlanta
    You use an RTA measuring device to position the chair for bass.
     
  14. LeeS

    LeeS Music Fan Thread Starter

    Location:
    Atlanta
    Once you get the chair in what Jim calls the “anchor point” then you can find the zone of neutrality (the right distance from the wall) for the speakers. You can adjust the distance between the speakers to get to the 83% rule (or 82-84 depending on room)
     
    DangerousKitchen likes this.
  15. Doctor Fine

    Doctor Fine "So Hip It Would Blister Your Brain"


    sorry. was not using my brain when I opened my mouth---ha!
     
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  16. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Antarctica
    You can't fix standing waves in a room with speaker/listener placement
     
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  17. bever70

    bever70 Let No-one Live Rent Free in Your Head!

    Location:
    Belgium
    We get that! BUT you need your speakers to play anything BEFORE you can measure, don't you? So, where do you put your speakers FIRST before deciding on the seat position (by measuring)?
     
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  18. bever70

    bever70 Let No-one Live Rent Free in Your Head!

    Location:
    Belgium
    Good for you, I only have one but I do get the wraparound bubble effect sitting further away (83%) and don't need to sit closer for that. Positioning the speakers further apart (equidistant triangle) thins the sound out which I don't like.
     
  19. Doctor Fine

    Doctor Fine "So Hip It Would Blister Your Brain"

    Correct. Don't try to fix them because you cannot do that---try to avoid them by learning where they pile up!
     
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  20. Doctor Fine

    Doctor Fine "So Hip It Would Blister Your Brain"

    By using the Sumiko method of placing them in the "power spot" that is where you want them to sit. You have to find that spot by using tests tones and recordings by ear. It will "light up" properly. Then you can get busy with "tuning" once you are "in the zone."

    Once I personally get in the zone with a speaker I find an 1/8 of an inch will drastically change where the vocals pop out. That is proof you are in the "power zone."

    The "Power spot" will still be evident as you move you chair around the
    room you will have tons of choices where to put the chair. Once the room is properly pressurized by the power spot the whole place is the "sweet spot."
    Then you look for chair locations that are the sweetest ones to choose from.

    I have all my chairs (all 4) in the living room sitting in the sweet spot. You get perfect separation over in the corner, at the back wall or standing up in the kitchen and looking back into the room. The image holds up no matter where you sit or stand it is in 3D.
     
    Last edited: Nov 17, 2022
    bever70 likes this.
  21. bever70

    bever70 Let No-one Live Rent Free in Your Head!

    Location:
    Belgium
    I know,but that would be after you have decided on the best seating position, right? So how do you decide on the (best measuring) seating position? If you put your speakers first (using sumiko method), then you are more or less stuck with a seating position...
    This is like the chicken-egg riddle...which comes first :D?!
     
    timind likes this.
  22. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    Agree, it is a function of room geometry.
    You can located the chair to avoid them.
    Sometimes using them when locating a sub can ameliorate a problem.

    The Cardis method in my room
    14 W x 32 L
    Speaker d between 7', to wall 3.5'
    From front wall 20' !
    Not going to fly :)
     
  23. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    I'm using 3 methods when I rearrange.

    Vandersteen (and others), odd numbers
    Front wall 390"/13 = 30
    Side wall 165"/5 = 33

    Focal
    A x C = B^2
    A > B > C
    3 dimensions
    Floor to woofer, 29 in my case, C
    Speaker face to front wall, 30", B
    Speaker to wall, 33", A
    any dimension can be any variable as long as A > B > C
    33 x 29 = 957 = 30^2 = 900

    I'll split the difference
    To side wall 32 from 33
    To rear 30.5 from 30
    32 x 29 = 928 = 30.5^2 = 930
    :)

    speaker d = 165 - (2 x 32) = 101" = 8.4'
    Seat ~ 11
    8.4/11 ~ 0.76
    If I scoot up 1' ~ 8.4/10 = 0.84

    I never claimed to be normal, my wife can confirm

    :biglaugh:
     
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  24. Doctor Fine

    Doctor Fine "So Hip It Would Blister Your Brain"

    Sumiko basically sorts the entire room. You take a stab at a sensible visual layout and then place the speakers and the chair at the same time. If you get it to work with audio but the location sucks visually---nothing is stopping you from trying out some other locations. The idea is that Sumiko will fix just about any location you can dream up. Just pick the best one available to you in that room. Some locations definitely ARE better than others. It takes work eliminating all the second-best ideas. But it is pretty simple work. Just time consuming.

    For example in my main room I first set it for "the chair" in the center. Then after living with this and noticing the sound sucked over at the sofa on the long wall I slightly retuned Sumiko to give clarity to THAT location and made sure I hadn't ruined "the chair." Sumiko will work at multiple chairs if you have the time to tune your room for friends to sit and listen with you. No need to keep it all to yourself.
     
    bever70 likes this.
  25. Nothinbuttrouble

    Nothinbuttrouble Well-Known Member

    Location:
    Antarctica
    You can play some dodgeball with the peaks and nulls but the overhang hangover from the standing waves doesn’t go away. The entire room will be pressurized. I’m also a bit skeptical of a single formula being universally applicable to a wide array of speaker designs with radiation patterns that vary so widely.
     

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