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Dats V3 measurement question.

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  • fpitas
    commented on 's reply
    I like the Variac idea. I wonder if a lamp dimmer would work, too. If it does, it's a bit cheaper. The harmonics from the chopping will sound terrible, but oh well ;)

  • JRT
    commented on 's reply
    A suitable variac can work well in exercising woofers free-air at 60_Hz with widely adjustable voltage. The advantage is in the quick and easy setup. ...after making a reusable cable assy.

  • billfitzmaurice
    replied
    I hang mine from a rafter in my shop with a piece of wire or twine. Free-air means just that. If you place it close to boundaries they'll show up as bumps on the impedance trace. I break in woofers before measuring them, and if they've been sitting for a while I 'wake them up' with a minute of pink noise, otherwise the suspension will be stiff and that will affect the result.

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  • DeZZar
    replied
    Originally posted by Grtpumpkin View Post
    I refoamed a pair of old boston accoustic A60's series 1 woofers with rotted surrounds and I performed a before and after free air sweep. I got significantly different numbers of the before and after of the refoamed surrounds..
    Well of course - the rotten surrounds really aren't exactly giving you a set of baseline measurements to compare with.

    Realistically you will probably never get the exact same specs - so its just about modelling the new measurements in the enclosure and checking how it performs. Chances are your re-foamed originals are going to work closer to the original performance than some random replica.

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  • Grtpumpkin
    commented on 's reply
    I can't imagine the driver jumping. The sweep tone is not very loud. At least it wasn't on my 8-inch driver. But then again, I'm brand new to all this.

  • Chris Roemer
    replied
    Yeah, I'll put 2 books down and set the backplate (magnet) vent over the gap between them, so as not to block the vent. OR, pull a kitchen table apart like 1", and straddle the gap w/the magnet.
    Also, on a light motor w/a strong magnet, you might have to hold down-pressure on the frame. If the driver "jumps" when you test it, it'll throw the results off. (Ideally, you'd orient the driver horiz. instead of face up, but then it's hard to lay nickels on it (for Vas) - which are EXACTly 5.0 grams each.

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  • Grtpumpkin
    replied
    Actually, I was asking out of curiosity as I vaguely remember reading somewhere about propping the driver up a certain distance from a horizontal surface. Something about reflections off the surface if it was too close.
    I refoamed a pair of old boston accoustic A60's series 1 woofers with rotted surrounds and I performed a before and after free air sweep. I got significantly different numbers of the before and after of the refoamed surrounds. I was interested in purchasing some one off specially designed woofers off e bay from midwest speakers that they had made specifically for the series 1 A60's. Those specs are different also. I can't find any T/s specs for the original A60 drivers. These were my very first attempt at refoaming speakers and I do question my results as I did not do the prettiest of a job. Although the speakers still sound pretty good.

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  • DeZZar
    replied
    I just have mine propped up a little on the magnet (not blocking any vents) on the desk.

    if you're asking because this is the first time you are measuring drivers and you are seeing different specs....this is normal....and drivers will require a break in period before they start measuring closer to manufacturer specs.

    https://techtalk.parts-express.com/f...uring-break-in

    Leave a comment:


  • Grtpumpkin
    started a topic Dats V3 measurement question.

    Dats V3 measurement question.

    New to measuring drivers.
    When measuring a woofer for free air parameters, what is the best position for the driver? Sitting on a flat surface on the magnet facing up? Raised up off the surface such as magnet sitting on a drinking glass? Suspended in air hanging from a wire with driver in horizontal position? Does temperature and humidity have a large effect on readings? What is the most accurate way to measure?

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