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TS parameters & Identical drivers in series or parallel? PART 2

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  • TS parameters & Identical drivers in series or parallel? PART 2


    This question has been asked before, but the answer was somewhat vague since they mention that the parameters R(e), L(e), Sd, V(as) and BL will be twice as much and the sensitivity +3db as for a driver when two of them will be connected in series. They also mention that Qes, Qms, and Qts do not change, remaining the same as for a driver.

    To the above, if supposedly they are two different measurements, they only mention that it will be the one of a single driver without establishing which one (??)

    Performing measurements on two woofers of the same model and brand with the Dayton Audio DATS V3 parts-express measuring equipment, the following results are obtained:

    Woofer 1:

    Piston Diameter = 123.2 mm
    f(s)= 37.15 Hz
    R(e)= 3,784 Ohms
    Z(max)= 53.11 Ohms
    Q(ms)= 5,136
    Q(es)= 0.3941
    Q(ts)= 0.366
    V(as)= 19.86 liters (0.7015 cubic feet)
    L(e)= 0.6089 mH
    n(0)= 0.2463 %
    SPL= 86.02 1W/1m
    M(ms)= 18.44 grams
    C(ms)= 0.996 mm/N
    BL= 6.429
    K(r)= 0.02554
    X(r)= 0.5509
    K(i)= 0.006714
    X(i)= 0.7044

    Woofer 2:

    Piston Diameter = 123.2 mm
    f(s)= 35.36 Hz
    R(e)= 3,795 Ohms
    Z(max)= 53.98 Ohms
    Q(ms)= 5.07
    Q(es)= 0.3834
    Q(ts)= 0.3564
    V(as)= 22.25 liters (0.7856 cubic feet)
    L(e)= 0.5943 mH
    n(0)= 0.2446 %
    SPL= 85.98 1W/1m
    M(ms)= 18.17 grams
    C(ms)= 1,115 mm/N
    BL= 6.321
    K(r)= 0.02539
    X(r)= 0.5508
    K(i)= 0.006462
    X(i)= 0.7087

    If I make a measurement of these connected in series, specifying that the equivalent diameter by the sum of the surface of both (119 cm2 X 2) is 174 mm, the following results are obtained:

    Woofers 1 and 2 connected in series and tested with Dayton Audio DATS V3:

    Piston Diameter = 174 mm
    f(s)= 35.56 Hz
    R(e)= 7,654 Ohms
    Z(max)= 105.1 Ohms
    Q(ms)= 4,807
    Q(es)= 0.3776
    Q(ts)= 0.3501
    V(as)= 37.9 liters (1,338 cubic feet)
    L(e)= 1,191 mH
    n(0)= 0.4305 %
    SPL= 88.44 1W/1m
    M(ms)= 41.96 grams
    C(ms)= 0.477 mm/N
    BL= 13.79
    K(r)= 0.053
    X(r)= 0.5467
    K(i)= 0.01338
    X(i)= 0.7049

    According to these results, all the parameters varied. Qes, Qms, Qts and F(s) are all close to the values of a single woofer. R(e) changed approximately twice, the same for Z(max), V(as), L(e), n(0), M(ms), BL, K(r) and K(i) . C(ms) is about halfway through.

    From all this, four questions:

    1. Is it correct to make a measurement of the T/S parameters with speakers connected in series to obtain these and take them as a basis for the calculation of the box as if you were using a single driver as the combination?

    2. Is there any mathematical model to reach a conclusion of the T/S parameters to calculate a box?

    3. Why does the variation of information between the data obtained by Dayton Audio DATS V3 and the original technical specifications of the manufacturer where it is mentioned that the F(s) = 43 Hz?

    4. Regarding item 3, what is the correct data to use for the calculation of a box, Morel Data Sheet, or Dayton Audio DATS V3 results?

    Thank you.

    (Sorry for the "parallel" mistake, I had to re-edit the post, so instead I put "series")

    Translated with (free version)

  • #2
    Something is a little off. The Re and Le should be half, not twice the single driver numbers. Unless you put them in series?


    • afrade
      afrade commented
      Editing a comment
      Sorry, I had to edit the post again. -> Parallels for series.

  • #3
    1) You can or at least use a modeling program that accounts for the use of multiple drivers.
    2) See 1. But basically if x driver needs y volume, then 2x needs 2y
    ​​​​3) A 5hz difference is minimal and will not make an audible difference and hardly a difference in the model.
    4) Use your own measurements. But a trusted manufacturer ie Dayton, Eminence, Morel, SB Acoustics provides data that is accurate enough for a good model.


    • afrade
      afrade commented
      Editing a comment
      The thing here is that all the software I have considers a single model with its unique parameters and it is not able to consider two drivers with different parameters.

    • afrade
      afrade commented
      Editing a comment
      Also, all the software that I know.

    • afrade
      afrade commented
      Editing a comment
      Is there any software that you recomend?

  • #4
    Sorry, I had to edit the post again. -> Parallels for series.


    • #5
      Your own measurements should work, although be sure to break the drivers in for a while first. Although I agree that the manufacturer's data will probably get you 99% there.


      • #6
        Originally posted by isaeagle4031 View Post
        1) You can or at least use a modeling program that accounts for the use of multiple drivers.
        WinISD does, but has no provision for series versus parallel wiring. You can model for one driver or a dozen, the modeled impedance will remain the same with the same Vb per driver.
        if x driver needs y volume, then 2x needs 2y
        +1, so model for one driver and adjust the box size accordingly for two or more. If a pair of drivers going into the same box have specs that aren't very closely matched average them.


        • #7
          At least we avoided the whole "Series connection must ruin everything!" discussion


          • #8
            VituixCAD will do enclosures for multiple drivers in series or parallel, it's free.


            • #9
              YOUR (actual) measurements will be "more correct" than the ave. of a bunch of (unknown when) mfr. runs.
              As Bill says, just average your (slightly different) parms together.
              If you want to build a box using a pair of drivers (and - for whatever reason - your software won't/can't do multiples), just run a model for a single driver (using a port - if that's your goal - of a suitable diameter) then double the box volume, and use 2 identical ports (w/each one) just like the port for a single. (Alternately, you can use a port with the same length, just multiply the dia. by 1.414 - to double it's cross-sectional area.)


              • #10
                Originally posted by afrade View Post
                Sorry, I had to edit the post again. -> Parallels for series.
                When loading the data for the drivers, an average between them can be used. This assumes, of course, that the drivers are identical models and in good repair. Worrying about differences that are small is an exercise in futility. Once in the enclosure, they will behave as if they are a single unit