radiogram Posted November 12, 2010 Share Posted November 12, 2010 After getting the WT3 tester under Windows XP (it does not work under W7), I measured the impedence and T/S parameters of Crites CS1526C Woofer mounted in a Cornscala Bass Cabinet. My Cornscala Bass bin has almost same volume of Cornwall but with different shape. It is rectangular the first 9 inches of depth and then tapers like a trapezoid towards the rear. The port shelf is same dimension and postion as of cornwall. First I will post the impedence I measured earlier with my crude simple method using a known series resistor ans measuring voltage. Here it is. Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 Here is the measurement of CS1526C (mounted in cabinet) by WT3. I did more than 10 runs at different times and the results were quite consistent without much variation. Re is right on (my Fluke Meter measures 3.8). The WT3 impedence curve pretty much matches with my crude method above with a few minor exceptions at a few frequencies. Also, the min impedence between the double peaks is at 40Hz suggesting tuning to 40Hz. Interesting things are as follows: 1. Le is reported as 1.7mH (do not know at which frequency) 2. Qts, Qes and Qms are substanially different from free air specs (cabinet loading cause??) which are Qts = 0.2, Qes = 0.27, Qms = 9.93. Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 Bob: Have you done Le measurements on the CS1526 at various frequencies with something like a B&K precision meter? Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 12, 2010 Share Posted November 12, 2010 The plot seems to look like 6 Ohms at about +36 degrees polar Zo at 400 Hz. That is 4.85 +j3.5 Ohms rectangular. It is 4.85 Ohms in series with 1.39 mHy. Is that typical for a K53 driver? Is that waht it's supposed to be? Al K. Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 Al: The plot I have posted so far are for BEC's CS1526 Woofers (in my Cornscala cabinet) which are as per Bob close to specs as early K33's. I will be posting the K53 measurement next. Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 Here is what WT3 says about K53/K701 combo. The impedence peaks in the midrange ain't so pretty! Also interesting is Le is repordted as 2.2mH higher than a Woofer??? Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 This is K77F as measured by WT3. I am wondering what effect there maybe from what I see around 3.5KHz. Quote Link to comment Share on other sites More sharing options...
radiogram Posted November 12, 2010 Author Share Posted November 12, 2010 It is also interesting that the K77F is labelled as a 8 Ohm nominal Imp tweeter. From the plot the average Imp is only around 6 Ohms. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 12, 2010 Share Posted November 12, 2010 I think all the measurements should confirm what I always say: Ignore the published impedance data. It's BULL $HIT! They are just nominal numbers that generalize what "category" they roughly fall into. 8 Ohms, 16 Ohms, 4 Ohms.. Yeah RIGHT! I just got a pair of B&C DCX50 2-inch coaxial drivers. Their impedance is "called" 8 Ohms. The tweeter section is more like 6 Ohms and the squawker section is roughly 12 Ohms. I'm developing a Linkwitz-Riley crossover at 9 KHz for it. The design will be at 6 Ohms with a transformer to attenuate the two by 10 dB and swampers will put everything back to a real resistive 8 Ohms. The midrange Zo plot is below. Al K. Quote Link to comment Share on other sites More sharing options...
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