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  1. #1

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    Default Drivers frequency response graphs....??

    I have spent the last few days, literally scouring the forum, but can not find any actual "User measured" frequency response graphs, of any of our vintage drivers/

    Has anyone actually measured the drivers, "Free" of the crossover, to get the actual undoctored response and Impedance graphs?

  2. #2

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    I don't believe Polk wants that information out there.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

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    well - anechoic chamber frequency response measurements are kind of useless - one's own in-room response is what will determine what one hears - umm - in one's own room.

    There are all kinds of RTA gizmos out there, at all price points, if one wants measure and/or correct.

    To measure T/S parameters on those ol' drivers; pick up one of these and go crazy...
    http://www.parts-express.com/dayton-...ystem--390-806

    so... in terms of system response, here's what Polk claimed, ca. 1976, for the Monitor Series models 7 and 10 (original, unsuffixed versions). Bear in mind that, AFAIK, there were then - and are now - no legally mandated standards for frequency response, so these are offered strictly as-is from vintage promotional literature. Notice that 'controlled, reverberant environment' qualification - that probably is helping the LF curve considerably.



    polk_brochure_back_pg by mhardy6647, on Flickr

    I doubt that they're anything like that flat in the real world (even with considerable smoothing applied to the data)... but I can tell you that they sound fine indeed and, for their modest price (then and now) they do a remarkably accurate and satisfying reproduction of music.
    all the best,
    mrh

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    Well was wanting this information, as that is typical to do when DIY changing Crossover stuff etc.

    The raw driver response on a baffle, is the starting point to determine how a crossover needs to be optomized to sound best.

    Then the effect of the crossover can be plotted, and any minor changes to improve thing are easy to see.

    I wanted to see the spike in the SL2000 tweeter and its response shape with no crossover
    Last edited by kevintomb; 01-29-2014 at 11:36 AM.

  5. #5

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    Actually AFAIK typically free-space response is what's measured. Baffles, as I am sure you know, introduce all kinds of response artifacts of their own. Take a look at Martin J. King's site some time for more than I'll ever understand on that topic (and more besides): http://www.quarter-wave.com/

    The T/S properties are - arguably - more important than the response in terms of designing crossovers (e.g., a Zobel network to tame inductive reactance). Fs is the important parameter in terms of the XO frequency; and Fs is readily determined from an impedance plot. XO frequency an octave above Fs (e.g., 2 kHz for a driver with Fs = 1 kHz) is a fine rule of thumb.

    At any rate, it's best to measure the actual drivers you want to use (the driver-to-driver variation was, and typically still is, rahter high; the big-bucks loudspeakers typically justify some of their cost by selecting carefully matched drivers). Get a measurement system like the Parts Express and go to town!

    ... and, no matter what, trust your ears vis-a-vis the measurements. If you build it and it sounds like crap, it won't matter if the impedance curve and fequency response are both ruler flat (beyond the impedance peak atr Fs); the system resonance is high Q and well damped, and the waterfall plots are textbook-perfect.

    Just my hardly humble opinions, of course.

    EDIT: For the SL2000 - some white noise (FM radio static) and an RTA with a good calibrated microphone will get you in the ballpark. The cute little Behringer UltraCurve PRO DEQ2496 ought to be able to get you a pretty good estimate. http://www.behringer.com/EN/Products/DEQ2496.aspx

    I've been looking for a good-enough excuse to justify getting one for a long, long time...

    FWIW, I'd say just pitch the SL2000s and get a pair of Peerless KO10DTs from eBAY... but if you're in the mood for a challenge, go for it.
    Last edited by mhardy6647; 01-29-2014 at 12:07 PM.
    all the best,
    mrh

  6. #6

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    Ya the SL2000's are not "bad" per se, but a bit lacking in the really top end, and that nasty spike around 12K.
    I was gonna make a notch filter and reduce the spike down a bit, until I realized I did not know for sure, the actual impedance over the tweeters range, nor the actual spikes width and height for sure.

    I had a response measurement from Stereophile on the RTA 11t (( which is my speaker I had to cannibalize)) from water damage to over half the cabinets while in storage.


    I could just willy nilly experiment I guess

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    I was playing around recently with a pair of Monitor 5 family members with the SL2000 and an EICO ST-70 (pp 7591A integrated amp of nominally 35 wpc) and found some recordings that illustrated its proclivities.
    all the best,
    mrh

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