Review: Marine Speakers
In my career as a reviewer, I've always focused totally on home and portable products, because other speaker categories seemed so different and I figured I couldn't be good at everything. So when Randy Vance, lab director of Boating magazine, e-mailed to ask if I could help him conduct a test of marine speakers, my first response was, "Huh?" I knew such things existed-at least one of my Dad's many boats had an audio system, though we rarely played it for fear we'd scare the speckled trout. But otherwise, I knew nothing about marine audio.
Poking around a couple of websites, I learned that marine speakers are a pretty large category, with some familiar brands and some I'd never heard of. The speakers didn't look all that different from typical in-ceiling speakers, so I figured I could handle the gig. Vance would do the most important part of the testing: actual listening tests on a power boat hauling ass through the Florida coastal waters at 30 mph.
On the boat
I was especially impressed when Vance told me he would build a custom baffle board to mount the speakers on for the test. He placed the test rig in a restored 1978 Glastron GT 150 powerboat (the same kind used in the Bond flick Live and Let Die, but with an updated motor), and set it up with a switcher. Vance switched among the speakers while various drivers of the boat, who couldn't tell which system was playing, judged the sound quality of each one.
The test included four brands: Clarion, Fusion, Jensen, and Sony, each of which submitted a pair of main speakers and a subwoofer.
You can read the full results of Vance's listening tests here.
In the lab
With that done, it was my turn. Vance sent me all of the speakers to conduct the same kinds of lab measurements we do for S&V. For the four pairs of main speakers we tested, I did the same frequency response, sensitivity, and impedance measurements I do for home speakers. For the four subwoofers, I did all of these measurements plus CEA-2010A output measurements.
These were all open-back designs, much like car speakers, so I had to build testing boxes for them. I used 3/4-inch MDF, which is a more rugged, less resonant material than those used in the walls (or bulkheads or whatever they call them) of boats. After browsing some website specs and consulting with a couple of marine speaker manufacturers, I decided to built a 1 cubic foot cabinet for the main speakers, and a 1.5 cubic foot box for the subwoofers. I stuffed the boxes with fiberglass insulation to a density of 1 pound per cubic foot.
Of course, this arrangement only loosely approximates what the speakers will be mounted in on a boat. How much air volume will there be behind the speaker? Who knows? Will the space behind the speakers be sealed or open? Who knows? Will the installer put any kind of absorptive material inside? Who knows? But at least it gave me a reasonable baseline.
Normally at S&V we focus on the average of a speaker's response in a horizontal window of ±30° from the front of the speaker. That's because indoors, so much of the sound you hear is reflecting off the walls, so the off-axis response matters a lot. In this case, though, considering that a typical marine speaker installation doesn't provide much in the way of walls to reflect sound, I focused on the on-axis response.
Check out the accompanying charts for the results. Mostly, the results were similar, although the Sony XSMP1611 main speaker did exhibit much lower treble output than the others. (I even noticed this just from hearing the pseudo-random noise that my Clio FW audio analyzer uses as a test signal.) However, I did notice a couple of trends in the measurements that are worth pointing out.
First, all of the speakers, even the anomalous Sony model, showed a boost around 4 kHz, which I assume is there to help the sound cut through all the motor, water, and wind noise you experience in an open motorboat. This is probably much like the boost around 3 kHz that many headphones have, which is generally thought to produce a psychoacoustically flat tonal balance.
Second, the subwoofers were close enough in design that the acoustical properties of the testing box swamped any differences in the products; that's why they all measured about the same. What really surprised me was that the CEA-2010A response results (measured using my 200-watt Outlaw M2200 amplifier) were also nearly the same. The Clarion CMQ2512W led the pack, but by only a fraction of a decibel, and all were in the same ballpark as a good 10-inch home theater sub. Check it out:
CEA-2010 average bass output results: marine subwoofers
Clarion CMQ2512W: 40-63 Hz, 120.0 dB; 20-31.5 Hz, 103.3 dB
Fusion MS SW10: 40-63 Hz, 118.4 dB; 20-31.5 Hz, 101.5 dB
Jensen MSW10S: 40-63 Hz, 119.6 dB; 20-31.5 Hz, 102.3 dB
Sony XSL100PSM: 40-63 Hz, 119.6 dB; 20-31.5 Hz, 102.4 dB
Unfortunately, I couldn't really listen to these myself and come to any useful conclusions. First, I don't have a boat on which I could actually listen to these in a suitable environment. Second, I lacked the presence of mind at the time to ask Vance to make a recording of boat noise at 30 mph so I could at least simulate a boating environment. Maybe next time....