Frequency Response
I test the speakers on-axis, and off-axis 30 degrees with the tweeter to the side and on top. This gives a good approximation of the how well the speakers can be expected to work within the huge range of mounting positions that they will be used in. If you can make them work well in all of these tests, you should be able to do the same in your car.
Graph 3 shows the separate on-axis response for the woofer and tweeter overlaid on a single graph without a crossover. The tweeter is a bit more efficient and has a reasonably smooth response out to 20kHz. The woofer however has a pretty choppy response with two 5dB peaks at 4kHz and 6.5kHz. My guess is that these are artifacts of the very stiff cone and dust cap. I will also hazard a guess that they will not be controlled easily by the crossover, but may disappear off-axis.
Graph 4 shows the on-axis response of the woofer and tweeter with a crossover. The highest peak on the woofer has been controlled but at the expense of an increase in the peak at 4kHz. It's also interesting to note that the tweeter's response extends well into the range that the woofer is playing. This is never a good idea and will cause substantial response errors.
Graph 5 shows the on-axis response with the tweeter at 0 and 180 phase. The 0 phase response is the better of the two because it is using the overlapping range for the tweeter to cancel some of the peakiness on the woofer. Neither of these responses is great though.
Graph 6 shows the 30-degree-off-axis response with the tweeter mounted above the woofer. This response is certainly better and my guess is that the engineers optimized the system response off-axis.
Graph 7 shows the off-axis response with the tweeter mounted to the side of the woofer. This now shows the dip at crossover point and some other pretty major response errors.
Graph 8 shows the tweeter's response using the attenuation switch. Because the testing is not done in an anechoic chamber, the results are shown above 200Hz, which is the range of true accuracy. To see the frequencies below this, I use a technique called near-field testing that gives accurate response from 10Hz to about 400Hz. Graph 9 shows the near-field response of the woofer and the very typical low Q shape. It is interesting to note that even though the Fs of the speaker is quite low, the low Q means that the response is actually down 6dB at Fs.
Graph 3 | 
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Graph 5 |
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Graph 9 | 
Graph 10 | |
I tested distortion (Graph 10) at 50 watts to see if the coil offset would show up and in fact it does. The distortion is climbing from about 400Hz and down. This means that without an active crossover and subwoofer, the midbass is going to have pretty high distortion. My guess is kick drums and the upper region of bass guitar will suffer.
So how does the Zapco
system stack up?
I can't say that I am impressed with the CK-16.2. It is not as flexible as many of the other component systems I have tested and the performance is really only average. In fact, it is surpassed by some coaxials I have tested. As I said above, we are just beginning to reevaluate our ideas about performance. Distortion may not sound too bad, and in the perfect mounting combination the Zapco system may sound great. Eric, did you hear what I tested?
Subjective
Installation
The Zapco CK-16.2 is retail for $1,159 for the complete set. When they arrived, I started to wonder if Zapco sold them by the pound! For being in such a small box, these things were heavy. I opened the box to find that Zapco had done a very nice job on the build quality on all of the components. The woofer has a cast frame and a lot of magnet. The tweeter housings are from machined aluminum billet and have a thread body to mount them. The tweeters do not have any kind of angle or surface mounting, but John Borges at Zapco told me they are looking into making these available. Even the crossover is mounted to a heavy-duty aluminum plate. The fit and finish is top notch and befitting the price point, but the owner's manual is pretty thin and needs improvement. Again, a talk with Borges reveals they are already working on the completed manual, which should be available by the time you read this.
The one real problem we had with installation had to do with the woofer. Zapco packs the CK-16.2is with a plastic ring. This ring is made to fit around the front of the woofer so that your mount screws do not get into the rubber surround when you tighten them during installation. Unfortunately, this information was not spelled out in the owner's manual (Borges tells me that all new units now have this info in their manuals) and could have led to a disaster if a less experienced installer were doing the job.
Listening
My appreciation for the Zapcos increased more and more as I listened to them. They excelled at all of the music I threw at them. On Diana Krall's Love Scenes album, I really enjoyed their image stability, height, focus and size. I liked the fact that the speakeris location disappeared within the image and sound staging.
Vocal and instrument detail was exceptional. The slight vocal overload in the recording at 0:18 seconds was clearly audible. String noises from the upright bass were good. Although the deep body tones were a bit rolled off in level, they were still impressive for a 6 1/2" woofer. Interestingly, the electric guitar and piano sounded a touch dull on their overtones. This surprised me because the vocals were so good and natural sounding.
On Lenny Kravitz's "Believe in Me," the Zapcos did a great job on the opening percussion and drums. The high hats and kick drum in the first four bars shimmered and kicked. I emphasize that the male vocals were really, really good. As a matter of fact, the overall musical balance on the Zapcos was great. Even at high volume levels the Zapcos did not overload or stress out the listener as the song built intensity and thickness. They stayed clean and smooth. The highs had good shimmer and extension, and the acoustic guitar was nicely rounded and had full body acoustics.
To test for a sense of space and how the Zapcos handle acoustic instruments, I listened to Telarc's 20-bit recording of Schubert's Symphony No. 9 "The Great." The opening French horns sounded nice, very realistic and with an excellent sense of ambience. The cello plucks and note shifts were good, but a subwoofer would have filled this out and given a more complete representation.
The full string section was expansive and true sounding. The oboe was a touch subdued, but still with the reediness you want to hear from an oboe. The Zapcos were able to maintain the sense of space and ambience, even during the big crescendos. The brass section did not get harsh or overly brassy. The timpani drums were thin on body, but still had that nice "kettley" soundothese speakers are very impressive.
OK, from Bach to blast! Yeah, I know that last track was by Schubert, but who's keeping track of the old dead composers anyway? I dropped in Usher's Confessions album and listened to the "Intro" track and "Yeah!" On "Intro" the acoustic guitar was just beautiful. The shakers had good detail and the backing vocals had depth. Usheris vocals were just a touch nasally, but you could hear his breathing. The overall clarity was excellent. The bass line as pretty darn solid, but it was missing the fundamental note.
On "Yeah!" the Zapcos were a little bright, but nothing that would turn me away. Adding a subwoofer should be the perfect cure for this too. The Zapcos' 6 1/2" woofer gave a mighty effort to reproduce this driving bass line and it did one of the better jobs of all of the speakers I have tested for CA&E.
Conclusion
I was a little skeptical of these speakers when I heard that they were a first effort from an amplifier company. Even the fact that they were from Zapco did not assuage my doubt. But after listening to them and living with them, I am a believer. These are one of the best component systems I have listened to; I would put them within the top five. What is interesting is that they are the least expensive of my top five, too. While $1,159 is a lot of money (and Zapco is working to improve the owneris manual and the other things I whined about earlier), I have to say the Zapco CK-16.2's may just be a deal at this price. You need to go and listen to them. Take your favorite CDs and goo.. right now. Go....