wharfedale Super 3 P1P2J1J2

These four Super 3 units are all original with exception of the annuli. There are two more original Super 3's currently in use.

The P1 and P2 have 14500 lines . The J1 and J2 field strengths are unknown but they check out for sensitivity the same as the P pair.

If my calcs are correct, 14500 lines here will equate to about 11,382 gauss (1.14 teslas) and 13,000 lines will equate to about 10,205 gauss (1.02 teslas)

Exotic rare earth metal magnets such as CoSm(cobalt/Samarium) and Neodymium(NdFeB) yield higher strengths for smaller magnet sizes. They also improve efficiency (sensitivity) as well as transient response which is very likely the reason why some folks don't like neodymium woofers. The bass is very tight and gives the illusion of a lack of bass. This is due to the speaker's ability to better follow the electrical signal (highly damped) and prevent the cone from over shooting the signal and sort of running away with itself.

FIGURE 1

Z VIO=J1; GREY=J2; BLK=K; RED=P1; GRN=P2

Referencing above 1khz, the upper two traces are those of the P1 and P2. They measure 15W at 4khz. The J1 and J2 measure 9W and the K unit measures 11W at 4khz. these impedances are used to calculate the power transfer which was measured at 1/4w 1/2m, which is the same as 1w1m. The erratic traces below 1khz are most likely due to the foam centering disc inside the voice coil, attached to the top of the pole piece. These were cut by hand and are not perfectly circular. While it doesn't look nice, it doesn't matter; the tweeter is second order high pass filtered at 4khz

The transfer function for power transfer is P=E²/Zcosq where q is the phase shift but we can ignore that as it is usually small. Transposing, we get E=SQRT(PZ), where SQRT is square root. It can be seen then that for 1 watt, the voltage that need be applied is the SQRT of Z at the desired frequency. For 1/4w, the voltage applied is the SQRT of Z/4. Thus, for J1, J2, we get 1.53v; for K, we get 1.66v and for P1, P2 we get 1.94v, resp. and all at 4khz.

FIGURE 2

1w1m VIO=J1; GREY=J2; BLK=K; RED=P1; GRN=P2click for image larger piccy

As can be seen here, using the voltages as described in fig.1, all 4 yield much the same output.

These response curves may not be linear but keep in mind that these tweeters are over 60 years old and are paper cone tweeters. Also, they tend to roll-off after about 15khz but despite all that, many still like their sound.

So many are influenced by the shape of a response curve and end up tweaking the system to get to where they like it; the resultant response curve is usually anything but flat. Keep in mind that the microphone used to measure this stuff doesn't have ears.

It seems that these folks spend too much time listening to their speakers that they miss the music.

The end result is that the differences in "lines" on the label has little effect on sensitivity and any electrical difference may have been compensated by the longer voice coil. In a stereo recording, the varying voltage levels between the two channels are different with respect to each other, thus masking any subtle difference in sensitivity. Now, if the system were switched to mono, then both channels get the same signal strengths and a good set of ears can easily detect a subtle difference between the channels.

The K tweeter came from my left channel corner Wharfies. Luck was with me as this fella has 13000 lines. The right channel tweeter has no label.