When the UPS delivery man came screaming up my driveway recklessly in reverse to deliver the product that I had been assigned to review all I knew about the Emerson Mobile SA-100 was what I'd been able to garner off the Web in the little spare time that I had. Aside from a few details I didn't know much about the product. So I eagerly tore into the package to uncover a pair of 10-inch subwoofers.
The SA-100 has an MSRP of $74.99, which makes it a very reasonably priced subwoofer. Emerson Mobile's representative states the subwoofer works well in small sealed, bandpass, and ported enclosures. Upon inspection of the drivers I found the following: plastic trim ring, large rolled rubber surround, bright blue chrome-plated injection poly cone, 70 oz. magnet assembly, 2-inch voice coil, vented pole piece, bumped back plate, heavy duty binding posts, and a heavy stamped steel basket with an interesting texture coat. The SA-100 has a rated power handling of 350 watts RMS. During my testing I determined that to be a peak power rating, as the subwoofers were driven to the point of audible distortion at or before that point. Power handling before audible distortion is also dependent on the frequency of the source material as well. I found this to be an accurate rating in the upper bass frequencies, but the subwoofer could be driven to audible distortion with less power in the lower audible frequency range.
Now with subwoofers and information in hand I decided it was time to sit down and do some enclosure modeling. I entered the driver parameters into WinISD to begin modeling enclosures. WinISD shows this driver to be optimal in a vented enclosure (ported) or a 6th order bandpass. I wanted to look at it sealed as well, since the manufacturer stated this would yield good response. In the response graph below I modeled the SA-100 in a sealed enclosure of .75 cubic ft. per driver, as well as 1.5 cubic ft. per driver.
I decided to take WinISD at face value and look at a vented enclosure for them. I chose a fairly large vented enclosure of 2.35 cubic ft. per driver tuned to 29 Hz. This makes for a pretty large enclosure for a pair of 10-inch subwoofers. However, those of you who are familiar with vented enclosures know that the more internal volume and vent area you can come up with the more SPL you will attain as a result. The vented enclosure appeared to have a nice smooth frequency response. According to WinISD this large vented enclosure should provide a lot more output then its sealed counterparts between 20 and 50 Hz.
I was concerned about low frequency extension with the sealed enclosures. However, I already had a .75 cubic ft. and a 1.5 cubic ft. per chamber sealed enclosure for a pair of 10-inch subwoofers so I decided to begin there.