Crutchfield saws in half an Elac speaker.

Discussion in 'Speakers' started by jazzmans, Feb 10, 2018.

  1. smoke-libr8r

    smoke-libr8r Active Member

    Messages:
    111
    Pete: Do you think that the purpose of the insulation material in the front reflex chamber is to help mitigate the chuffing from the inner ports? The frequency content seems about right.

    I wonder if anyone could have done a design like that in the days before CAD?

    If you are going to test a new blade, you'll want to do a better job avoiding the magnets than the Crutchfield guy. ;) When he first started cutting there were a lot of sparks.
     
    alteclipsch likes this.

     

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  2. alteclipsch

    alteclipsch Super Member

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    1,559
    That was the first thing I noticed!
     
  3. Retrovert

    Retrovert AK Subscriber Subscriber

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    Location:
    New York City, NY
    Of course it could be designed before CAD!!! (shakes head in disbelief at the notions of the kids these days, and how they think the entire design world started circa 1990, springing from Zeus's head fully formed, and before that we all lived in caves and hadn't yet discovered fire, let alone electricity, until, as documented in Kubrick's "2001", we danced around with animal femurs in our hands because monoliths educated us.)

    No CAD magicks are required! Computers make things faster and easier, but a whole world of engineering existed before widespread adoption of CAD. Jordan's paper on the ARU was published in 1956! Neville Thiele (to cite another of the most famous researchers) was publishing papers on filter design in the 1950s and on the design of vented loudspeakers in 1961! Jordan, Hartley, and a host of others were publishing in the 1950s as well! No CAD then! It was either hand-cranked calculators or slide rules.

    This was soooooo long ago that cars were land yachts with tail fins! TAIL FINS, I say, TAIL FINS. If one wanted car audio it was a portable 45 in mono on an AM radio using a vibrator to form high voltage. You have no idea of the horror.

    Port calculations may be performed with a hand calculator. Even pencil and paper. Understanding the math is the issue, not performing the calculations. See:

    From those references it is calculations like:
    Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)
    Sd = pi*(Dia/100)^2/4
    Vd = Sd*Xmax/1000
    Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5

    Engineers designed speakers with non-CAD programs (written in Fortran, PL/1, Basic, assembly language, etc), hand calculators (programmable HP-41 calculators), even sliderules.

    I had electrical engineering software running on my HP-41 circa 1980. Performed, among other calculations, filter design. Butterworth, Bessel, and others. (Somewhere I still have that calculator. It cost me two weeks pay!) We also used filter software on an Apple ][. Not CAD, by any means, just a faster way to do calculations than a non-programmable hand calculator.

    One could design a double-tubed bass-reflex speaker with a passive radiator using a pencil and empty spaces on the newspaper racing sheets. Sheet of MDF, circular saw, circle-cutter router jig, drivers, glue and clamps, capacitors and inductors for a crossover, badda bing, badda bam, badda boom. Speaker.

    Next step, discover fire and electricity, move out of the cave, put some clothes on, invent bureaucracy, internal combustion, and double lattes to drink during rush-hour traffic while listening to traffic reports on AM. Plus social-media forums to ensure nobody ever gets any work, particularly speaker designs, completed.
     
    SuperLead100 and maxhifi like this.

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