7 inch driver test results

The following drivers were tested.

Dayton RS180

Seas W18

Seas CA18

Scan Speak 8535

Scan Speak 8543

Scan Speak 8545

Scan Speak 8546

Vifa M18

Vifa PL18

Adire extremis-note the extremis was tested considerably after the others and the graphs are presented separately, mainly for my convenience.

And also note-for both the M18 and PL18, only limited data are available.

First, impedance curves and 1" nearfield FR curves. Note the RS180 is in black. Others per legend. Extremis impedance not shown/done.

Now, zoomed in between 100 Hz and 10kHz.

1" nearfield frequency response

Extremis 1" nearfield frequency response

Linear distortion

Extremis vs RS180 at 400 hz

Extremis vs RS180 at 800 hz

Extremis vs RS180 at 1200 hz

Extremis vs RS180 at 1600 hz

Extremis vs RS180 at 2000 hz

Nonlinear distortion

There are many graphs to look at here. First, there is a series of graphs using a single tone stimulus. The level was slowly increased until a target third order distortion product was achieved. At 30 Hz this was -20dB, at 50 Hz this was -30dB, and at 80 Hz this was -40dB. This is arbitrary and driver that had a significantly lower or higher absolute spl are difficult to compare. The graph is set to the level of the Dayton in all three series.

This data is a bit difficult to interpret. So much for this way of doing it. The RS180, W18, and CA18 have roughly similar outputs, and so they are directly comparable. The entire Scan series was able to put out ~3-5dB more output before the 3rd order HD product reached -20dB. Although the RS graph at first look is better than the Scans, 3-5dB is not an insignificant amount at 30 Hz. So, the Scans are capable of producing a notable amount of additional spl, although the RS is very clean. Consider the following graph below

Here's what we are looking at. The original RS180 curve is in black. The level of the fundamental is 78dB. The original SS8545 is in light blue. At first blush, the RS beats the SS. But not really. The SS8545 is putting out a fundamental level of 82dB. When you increase the drive level of the RS to 82dB for the fundamental, the red curve results. Clearly, the SS8545 beats the RS180 in absolute spl output at 30dB. Note that, below this level, the RS is a very clean driver, maybe better than the SS.

The adire is capable of at least 3dB more output over the scan. The spectrum is a bit noiser than the Scan's, but would improve if I reduced the extremis drive level to match the output of the Scan.

Let's look at the 50 Hz data with the third order product at 30dB down.

Again, the spl problem occurs at 50 Hz. The Scans have variably more output. So, let's increase the drive level again on the RS180 to 88dB and compare this to the above graphs. In this case, the outcome is not quite as clear. Consider the following graph.

The graph is done a bit differently here. The RS180 curve in black is shown already with the level increased to match the SS8545 and SS8543. While the RS180 has a bit more 3rd order products, it's cleaner than the SS8545 higher up. I threw the SS8543 in here because, well, it's a surprisingly good driver as well.

The Adire driver has a fundamental level of 88dB here at 50hz. Still in the best group with the scans, but its lead over the scan has evaporated.

So lets look at 80 hz. Let's just look at everything adjusted to a fundamental of 98dB.

Note all sorts of bad things are happening to the W18 in the above graph. I couldn't get to 98dB. I know the lower order distortion products don't look all that bad, but the higher order products are very audible. Since the ear is less sensitive at low frequencies, you end up hearing a lot of rub and buzz on a signal such as this.

Good performances by the CA18, RS180 and SS8535. A bit of higher order distortion starting to creep in for the 8545 and 8546's. We'll see more of this at 150 hz from the SS. Disappointingly, I didn't do this for the extremis. Perhaps JonMarsh will when he gets praxis...

Nonlinear distortion continued. Page 3. SL style 3 tone tests.

We'll start at 80 hz.

So, they all do well here and are very closely grouped, except for the Vifa M18, which lags behind.

Let's look at 150 Hz.

Also, similar performances, though surprisingly, the SS8545, 8546, and extremis suffer from more than expected higher order distortion. It is audible. The W18, although one of the best at 150 Hz, does not clearly distinguish itself from the other leaders. It's not clear to me there is any clear difference between the RS180, W18, 8543, and maybe the 8535 and CA18.

Let's look at 400 Hz.

Wow, where did the SS8543 come from. Clearly the best in the group. The SS8535 is right behind it. The RS180 and W18 are next, though I would give the edge in this case to the RS because the number of distortion products overall is a bit lower. The SS8545 probably can be said to fall in this group, edging out the SS8546 which seems to have more distortion products overall, though the levels are good. No mistaking the superiority of the 8543 in this particular test though.

Lastly, let's look at 850 hz.

Conclusion

All the drivers tested are good. I would have liked to have a bit more data for the extremis and M18. However, a couple of conclusions can be made. First, there is no clear dominant winner.

 The extremis clearly has the brute force excursion that is claimed for it. But its midrange/3 tone distortion tests are in the middle of the pack. Its linear distortion is reasonable if used below 2k.

The Scans are a bit of a heterogeneous group, with suprisingly good brute force excursion, second only to the extremis, and remarkable midrange distortion for the 8543 and 8535. The 8545 and 8546 have overall good performance, marred slightly by the appearance of higher order distortion products at a couple frequencies. The 8535 is a suprise, with very good linear distortion and very good midrange distortion. The low end is probably very good-but I'd have to redo the nonlinear tests with the level adjusted. (On one of the graphs, the spl of the 8535 is 10dB greater than some of the other drivers-so comparisons the way I did the testing is difficult.). This would be a good choice in a sealed box/2nd order acoustic slopes. I'm definitely keeping my pair.

The w18 has the best linear distortion numbers, below 2k anyway. And in the group with the best midrange distortion numbers. Unfortunately, disappointing brute force excursion, even beat out by the CA18, which is a pretty good drivers all around, though it doesn't standout in any category. The w18 is best used as a lower midrange. In the 150-1500 hz range, it is the clear winner.

The RS180 is without a doubt the best value. It does not have any significant defects, except its FR curve gets funky above 1200 hz (or, it's linear distortion rises notably at 1600 and 2000). It can't quite match the smoothness of the FR curve of the W18, but has overall better distortion numbers when considering performance below 100 hz. In a two way, I would go so far as to say that the RS180 is better than the W18.

Depending on which factors you consider important and how you weigh them, any of these drivers could be the "right one." For example, if you want a woofer for sealed box use, crossed with second order acoustic at 2k, the SS8535, might be the best. If you want absolute maximum low end spl, the extremis is the king. As a low midrange crossed at 150hz/1.5k, the W18 might be the perfect choice. If you're on a budget, or, if you're willing to sacrifice a small amount of bass for improved midrange performance, and can cross low, the RS180 is the right choice.