8" Woofer test data

The following midranges were tested--

    Seas W21

    Dayton RS250 prototype

    Scan Speak 8555

    HiVi M8a

    HiVi M8n

    Vifa P21

    Silver Flute 8"

The following data are shown

Impedance-standard curves and enlarged views

Nearfield frequency response done at 1"

Nearfield linear burst distortion at 600 Hz, 1kHz, and 1.4kHz.

Nonlinear distortion

    3 tone at 150 and 800 Hz.

    A single 60 Hz tone adjusted so the fundamental spl at 0.25m is 98dB.

    A multitone burst of 20, 28, 44, 64, 92 Hz.  This is a challenging test and the level was set to 92.3dB with a distance of 1 inch so as to not destroy the drivers.

Impedance Data

From 20 Hz to 20kHz

A closer look at the region from 100 Hz to 10 kHz. The colors represent the same drivers as above.

Frequency response

Linear distortion

Nonlinear distortion data

3 tone distortion at 150 Hz and 800 Hz.

First, at 150 Hz.

At 800 Hz

SF8 3 tone data not done. What can I say, I just forgot to hit save...

Now, single 60 Hz HD plots.

Now, the 5 tonebursts.

Comments and Conclusion

Well, this was interesting. There are a couple of different ways of looking at the data. But I look at it this way. The drivers break into three groups. In the top tier the Seas w21, Dayton prototype RS250, and SS8554.  In the second tier, the HiVi M8a, then M8n. The bottom tier contains the Vifa P21 and the Silver Flute 8". 

The overall value award goes to the RS250. It is well built with a cast frame and shielded. Stunningly, it beats the Seas w21 under 100 Hz and really, more or less ties the w21 in the 150 Hz and 800 Hz tests.  While the nonlinear distortion numbers under 100 Hz look similar for the RS250 and the SS8555, there is some rub and buzz present IN THE SCAN about 5 dB before the Dayton. 

If you didn't quite catch that, what I said was, under 100 Hz the Dayton is the best and is capable of about 5 extra dB of headroom. The W21 is as good, or marginally better at 150 and 800 Hz, but can't keep up with the Dayton down low.

Wow.

The achilles heel of the Dayton is poor nonlinear performance above 1k. Really, it would take some work to equalize this much above 1kHz. The W21 does significantly better in terms of linear distortion above 1k though the SS does even better. The Seas is still probably the best in an application that has a sub, i.e. as a low midrange. The SS is a fine performer and probably the easiest to cross. The Dayton, if crossed between 1 and 1.5kHz would be outstanding. (Jon, are you listening? The Dayton is an ideal candidate for a higher order xover...maybe.  4 drivers per side-who needs the TC2+'s?)

Beauty, of course, is in the eyes of the beholder, but the gorgeous driver award goes to the HiVi.  And they do well.  They actually have better numbers below 100 Hz than the W21, but don't do as well at 150 and 800 Hz.  The m8n does a bit worse. The Vifa has respectable nonlinear distortion numbers, but does poorly at linear distortion.  The Silver Flute sort of follows the Vifa with respect to mediocre linear distortion, and has more trouble than the Vifa overall with nonlinear distortion.

Now, these tests are certainly not exhaustive, but I think the essential flavor of the drivers is captured. Try not to make much of small differences. I look at it this way.  A difference of 5 or more dB is probably significant.  Less than 5 dB, probably not. So drivers are either much better, similar, or much worse. Sometimes a signal is audibly worse, but not markedly measurably worse.