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ND105-4 fans

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  • DDF
    replied
    Re: ND105-4 fans

    Thanks Chris, good information.

    Leave a comment:


  • raiderone
    replied
    Re: ND105-4 fans

    Thanks for posting your findings.

    By chance did you try the ND105-4 sealed? And if so, how big was the enclosure and what was the f3?

    Leave a comment:


  • Chris Roemer
    started a topic ND105-4 fans

    ND105-4 fans

    About a year ago, when working on my Nano Neos, I ran a pair of these woofers on my WT3, and published the T/S parms that I used to model the cabinets: Qts = 0.48, Vas = 0.13 cf, Fs = 56.

    Initially, in the 2010 catalog, and again in last year's Jan/Feb flyer, PE's (or DA's) original specs were: Qts .55, Vas .16, Fs 77 (oddly enough - that FS was identical to the ND90, hmmm . . . ). At work, we get errors a LOT on electronically generated paperwork. We like to blame it on "cut and paste".

    In last year's Mar/Apr flyer (when I first got excited about this little woofer) the Fs spec had dropped down to 54 Hz. Right now, in PE's "Woofer Selection Guide" the Q, V, F parms are .55, .16, and 54 (ok, 53.8 actually).

    Last month, the new 2011 catalog came out. Guess what? SAME old Fs spec as last year's catalog (77 Hz), AND the Pe spec has also dropped down from the 30 watts it had last year, and still has in the WSG, and in the specs on the Dayton Audio site, to its initial 25 watts. The Jan/Feb flyer has the same (high) Fs, of 77 Hz, and low Pe. Cut-and-paste strikes again.

    Well, I just got eight ND105-4s, and ran them all on my WT3. I tested them before and after break-in. There are SOME parms that not only didn't change with break-in, but were basically identical to those I obtained last year. Re has ALWAYS been 4.0 ohms. The only "spec" I've ever seen is 3.7 ohms. 4 ohms is really more of a 6 ohm "nominal" impedance driver's Re, than a 4 ohm driver's Re (which is usually a lot closer to 3 ohms), but it helps keep the system's imdedance hgh enough to not cause an 8 ohm amp any sweat. The Le spec has always been 0.78 mH, and I've always gotten 0.79, perty darn close. Also, I've always gotten an SPL of 84dB/w/m out of my WT3, which is also what WinISD comes up with, maybe a dB higher than the official spec.

    This year, I had a good sized sample, with 8 drivers. Last year's sample was only 2 units. First I'll show you how they measured, then tell you my thoughts.

    Data string will be: parm - lowest (of this year's 8), average, highest, "/", then (out of only 2 units last year) the lower, then higher.

    Qes - .50 .53 .55 / .49 .54
    Qms- 6.7 7.0 7.5 / 6.8 7.5
    Qts - .46 .49 .52 / .46 .51
    Fs --- 61 63 65 / / 54 62
    Vas - .12 .12 .12 / .12 .16

    Well, all the Q values are fairly close to what I got on my small sample from last year. Out of my two 2010 samples, one Fs was right in the range that I got this year, but LAST year, the other unit was unusually close to the lowest published spec. I've never seen an Fs as high as the (current) 77 Hz spec. I ran the Vas using added mass, and used 35 cents (g), 7 nickels. Oddly enough, out of 10 drivers, 9 had a Vas of 0.12cf, but ONE last year was 0.16, which is actually the spec you see published. The ND105-EIGHT is actually published as 0.13 cf.

    So, I've changed my T/S modeling specs, but just by a tad, except for Fs, which had to be raised.

    Qes = 0.523, Qms = 7.1, Qts = 0.487, Vas = 0.12 cf, Fs = 62.

    I'm keeping my Nano Neos box design the same. Either 0.30, or 0.28 cf (where all panels can be cut from one 24" x 48" sheet). I stressed an 8" long x 1.5" dia. vent before, but given the rise in Fs by 6 Hz, 7" won't be bad at all. Even with the Fs change, the modeled F3 only rises by a few Hz.

    As far as parameters changing with break-in, Qms dropped almost 10% from an ave of 7.6 to 7.1, and Qes and Qts (which is highly dependent on Qes) both dropped just over 5%, from .56 to .53, and from .52 to .49. Fs also dropped from 67 Hz down to 63.

    Chris
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