CDT 07 - Lightest driver out of the three. Cast frame has a cheap, plasticky feel to it. Pole vent in the rear, no venting under the spider. Claims to have a copper faraday ring atop the pole piece. Straight profile fiberglass cone, with a soft, dome shaped poly dustcap. This driver has very noticeably the least amount of physical excursion, but is a good ~3mm shorter than the Seas G18RNX/P. (Driver provided courtesy of Ken)
RE XXX - Heavy driver. Cast frame feels like a heavy aluminum cooking pot. Huge tapered chrome top plate. Ventilation under the spider. Rear pole vent. A good amount of physical excursion, but surprisingly seems a tad bit under the Seas G18. Soft poly cone with inverted poly dustcap, feels like tupperware. Would be nice to see more than 4 mounting holes for such a heavy driver. Depth is a good 10mm+ or more than both the other drivers. Don't drop this one on your foot.
Seas G18RNX/P - Very solid, heavy open cast basket with wide open ventilation under the spider and rear pole vent with bumped backplate. Without bump on the backplate this would be the shortest depth driver. Physical excursion is the best of the three. Straight profile fiberglass cone with hard plastic phaseplug. Would be nice to see copper, but only on the Excel I guess
8 mounting holes on the frame, vs. 6 for the CDT and 4 for the RE.
How do they sound? I'm still listening.... I will say this though. My first impression is that NONE of them can touch the Seas W18 Excel
The CDT and the Seas G18RNX sound identical to me. Which is to say pretty good. Not the absolute best midrange like what you'd expect from a stiff cone driver with a top notch motor, but definitely at the top of the class with respect to conventional overhung drivers. Sound was lively, fairly open, smooth, and without hint of cone breakup or coloration. And btw, the Seas just killed the CDT's in mid/bass. Although they were fairly punchy, they began to show definite signs of strain well before the Seas. Also, with about half the power available the 8ohm Seas driver was roughly about the same loudness and headroom as the CDT.
The XXX was the worst performer of the bunch. Good bass, just perhaps a bit less than the Seas. Tonally very good in that respect, as least for IB door applications. Midrange sounded much like a Hi-Vi poly cone I tested earlier this year... which is to say not that great. Details were very "mushy" and confused sounding, and overall "congested".
Here are the frequency response plots. Keep in mind that the nearfield response is only good up to 500hz, and the farfield plots are good only down to 500hz. The idea behind this is to measure the driver very close to the cone, where the driver's own response won't be affected by the room or baffle. However, it's only useful up until a certain frequency (4311hz / driver diameter in inches per D'appolito). The farfield response is taken at 1m away and gated... that is information recorded beyond a set amount of time is disregarded... that keeps room reflections from interfering with your measurements. Merging both the nearfield and farfield plots therefore gives you a reasonably accurate overall frequency response measurement.
Note - 1/3rd octave smoothing applied
Measurements include spreading loss (drop in response below 1khz, due to mounting on a small baffle)
Comparison of relative efficiency:
I'd say they're more or less the same, with perhaps the CDT being slightly more efficient.
Waterfall plot:
Distortion:
Scale is 10db per line. I don't know the drive voltage or actual dbspl. Taken at 1m, decently loud. (Save the pics and zoom in to distinguish better)
At 80hz the XXX leads, followed closely by the Seas G18, and lastly the CDT07 which has a significant amount of higher order products.
At 200hz, the Seas G18 has significantly higher 2nd order distortion, but otherwise very low on higher order distortion. XXX has lower 2nd order, but more serious higher order distortion. CDT07 just performed terribly with significant 3rd, 4th, and 5th order distortion. I'd have to rank from best to worst Seas, XXX, and CDT.
800hz is really a tie. XXX has higher 2nd order distortion, but lower 3rd. Seas G18 has pretty decent results all around. Cdt did OK as well. No real winner here.
Listening with just pure sine waves, I prefer XXX < 1khz, Seas above 1khz, and CDT not at all. CDT showed the most obvious coloration with test tones. XXX above 1khz began to sound "shrill" and raspy, otherwise good performance.
I also did a high power sine sweep from 20hz to 80hz. Significant rubb and buzz with the XXX. Driver was nowhere near xmax at ~60hz, and the thing was buzzing like an angry bee's nest. CDT was bad too, but not nearly as bad as the XXX. Seas showed poor performance, but was the quietest of the 3 by a noticeable amount.
