wanted enclosure design for 8" maganavox 8rw

[stevodude]

Been trying to find info on plans for a pawo zhorn 8" all morning, and for the life of me I can't.

Seems most of the zhorns are designed around the fe127 or that sized driver.

I have 2 magnavox 8rw's, and a couple of different tweeters to try, and heard that the 8rw's work best in a zhorn side vent arangement.

Anyone have any idea of where I can get a plan?...

or can I just throw these drivers in a Half Chang?

Cheers, stevo.

[stevodude]

Ok, maybe I didn't supply enough information?...

If I run through some tests to get some more driver specs manually? Taken from http://www.radiolocman.com/shem/shem....html?di=18868

Can I do this to get an close enough approximation of fs, Vas and Qt?


* Using either an 8 ohm precision resistor (or accurately measuring the resistance of the "calibration" resistor), turn your generator/AC voltmeter into an impedometer by driving the calibrated resistor from the generator through the 1 kOhm resistor, and adjust the output of the generator until you get a convenient voltage across the resistor. For example, if the calibration resistor is 8 ohms, you might adjust the output so that you measure 8 mV across it. Basically you make the current 1 mA so that on the mV scale on your voltmeter the reading is effectively both mV and Ohms. Your setup will look like this:

                        o---- 1kOhm -----+<-------+
                        |                |        |
                      Sine gen.       8 ohms   AC voltmeter
                        |                |        |
                        o----------------+<-------+

This circuit is called an impedometer, where the voltage across the load is proportional to the impedance of the load. The 1 kohm resistor turns the oscillator into a pretty good approximation of constant-current source.
* Measure the DC resistance of the driver to test. This gives you Re. [Let's say it's 6.5 ohms]
* Replace the calibration resistor with the driver to test. Do not change the voltage from the generator!
* Adjust the frequency in the region of the specified resonance until the voltage across the driver is at a MAXIMUM. Record the frequency. This is Fs, the resonant frequency [let's say it's 32 Hz]. Also, measure the voltage across the driver. This is defined by Re+Res. [let's say voltage is 42 mV which means Re+Res is 42 ohms]. (using an oscilloscope set for phase measurement, Fs will also be where the phase is 0).
* Calculate the ratio between the DC resistance (Re) and the maximum impedance (Re+Res), call it Rc. [In this case, it will be 42/6.5 or 6.46]
* Find the two frequencies on either side of the resonant frequency f1 and f2 where the impedance is Re * sqrt(Rc) [in this example, that impedance will be 6.5 * sqrt(6.46) = 16.5 ohms, and let's say that occurs at f1 = 22.6 Hz and f2 = 45.3 Hz].
* Calculate Qms as:

                           Fs sqrt(Rc)
                     Qms = -----------
                             f2 - f1
                  [in the example, it will be:
                           32 sqrt(6.46)      32 * 2.54      81.3
                     Qms = -------------  =  -----------  =  ----  =  3.58
                            45.3 - 22.6          22.7        22.7
    * Calculate Qes as:
                             Qms
                     Qes = --------
                           (Rc - 1)
                  [in this example, it will be:
                             3.58         3.58
                     Qes = ---------  =  ------  =  0.66
                           6.46 - 1       5.46           
    * Calculate Qts as:
                           Qes * Qms
                     Qts = ---------
                           Qes + Qms
                  [here, it would be:
                           0.66 * 3.58      2.36
                     Qts = -----------  =  ------  =  0.56
                           0.66 + 3.58      4.24

So, you have derived Fs, Res, Qms, Qes, Qts for the driver.

* Repeat the measurements in a sealed, leak-free, unlined test box, and determine the equivalent values of Fc, Qmc, Qec, and Qtc (use a box whose volume, Vb, is close to the expected Vas for maximum accuracy). [In our example, Vb = 20L, Fc = 80 Hz, Qec = 0.95]
* calculate Vas as follows:

                                Fc Qec
                    Vas = Vb [ -------- - 1 ]
                                Fs Qes
                  [In our example:
                                80 * 0.95                76
                    Vas = 20 [ ----------- - 1 ] = 20 [ ---- - 1 ] = 20 * 2.62 = 52L
                                32 * 0.66                21
                   Our Vas is 52 liters].

You now have Fs, Re, Qms, Qes, Qts and Vas.