Mark K's Speaker Pages
...when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science...Lord Kelvin
Woofer Test Group 9-Dayton RS180, Seas ER18, Scan Speak Revelator 18W4531G00 and the SB Acoustics SR17NRX35C
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7 inch driver test results
The following drivers were tested.
Dayton RS180 - Used as a reference standard. (Not necessarily because it's the best driver, but it's a solid performer that I've tested many times. It is remeasured here as control/yardstick.
Seas ER18
SB Acoustics SR17NRX35c
Scan Speak Revelator 18W4531g00
First, nearfield FR curves. Note the RS180 is in black. Others per legend.
Nonlinear distortion
The first four graphs below are 5 tone nonlinear distortion spectra. The RS180 is first, as a reference, followed by the SB17, the ER18, and lastly the 18W4531g00.
Note the RS180 and the SB17 have very similar spectra. However both are clearly eclipsed by the ER18 and 18w, which have a distortion spectra that is at least 10dB lower across the board. The 18w measures technically better than the ER18 although the difference is so slight that it is within measurement error. The blunt translation of this is that the ER18 has about the same low end excursion capability of the 18w.
The next series of graphs are 3 tone nonlinear distortion at 150 and 800 Hz. This is all I had planned to do. I added more tests, and you'll see why shortly.
Here, the 18w is the best performer. The RS180 and ER18 are in a second grouping. The SB17 would be here as well, except there is too much nonlinear distortion between 1 and 3 k. Is this audible? It is when I do the tests. It sounds like wind noise from the motor and is clearly distinct being in the range of 8-15th order.
What about 800 Hz?
They all do well, but now the SB17 is the best of breed, besting even the revelator, though the difference is small.
From my initial tests above there is just not quite enough information to decide on a pecking order. I decided to go ahead and retest the RS180, ER18 and SB17 at 80 and 400 Hz. Due to time constraints, I did not test the revelator at those frequencies. You'll just have to decide for yourself if there is enough data to crown the revelator king. We all live in a world full of incomplete information; you just have to decide...
At 80 Hz
At 400 Hz
At 80hz, all do reasonably well, though there is still a little bit of the pesky higher order noise in the SB motor. At 400 hz it's quite severe and audible during the testing.
Conclusion
The RS180 was included as a benchmark comparison. It has solid low end excursion, as evidenced by the 80 hz 3 tone and the 5 tone spectra. It sets the standard for budget audiophile quality, so to speak. (I just wouldn't bother with a cheaper quality driver. Honestly, is it worth working hours on a project with lousy drivers.)
However, the RS180 does not have class leading low end excursion performance. It does have excellent midrange performance and is priced well.
The revelator is the best performer, excepting the lack of data at 80 and 400 h. 'nuff said.
The SB17 could be a worthy performer. Extraordinarily built, on par with the revelator. It is, unfortunately hampered by some chuffing/wind noise coming from within the motor. Now, you might argue that testing in a dipole configuration exaggerates this deficit. Perhaps. Still, there is a better alternative.
Which leads us to the ER18. Wow, when did Seas get their low end together? Back in the old days, my impression of Seas drivers was-extraordinary consistency, excellent midrange and linear performance, but so-so on low end excursion. I guess the Seas engineers must have taken a peek at Zaph and my site, and saw the good low end performance of the Usher, Dayton, and other Asian products, and had some sort of epiphany.
Because, the low end of the Seas ER18 is almost the equal of the revelator. The eye has not seen, nor the ear heard such blasphemy... Overall, the data for the revelator, taken together, suggests that it is an incrementally better performer than the ER18. However, the difference is small, mainly caused by some merely average (good, but average for the good/better drivers) readings for the ER18 in the midrange.
ps. this is not the way I wanted it to turn out. I'm making a two way box and wanted to do something different from Zaph. I really wanted the SB to test better. But, the data is the data. Looks like I'm going to end up with my own Johnny come lately ER18 based two way. Thankfully I won't use the same tweeter. That would be embarrasing...maybe I should just call it the "foxbat" or "foxhound."