Subwoofer Reviews

Extended Test Bench

Frequency response

• SM65: 43 Hz to 20 kHz ±3.5 dB
• SM45: 46 Hz to 20 kHz ±4.7 dB
• SuperCube 8000: 32 to 116 Hz ±3 dB

Sensitivity (SPL at 1 meter/1 watt)

• SM65 85.3 dB
• SM45 82.8 dB

Impedance (minimum/nominal)

• SM65 3.1/7 ohms
• SM45 3.3/7 ohms

Bass output, subwoofer (CEA-2010 standard)

Bass output, SM65 (CEA-2010 standard)

Bass limits

• SM45:                                                    95.4 dB at 40 Hz

The frequency response curves shown above represent the average of quasi-anechoic measurements taken at 0°, ±10°, ±20°, and ±30°, all performed with a Clio FW audio analyzer. The microphone was placed on-axis with the tweeter (the position where I got the flattest response) at a distance of 1 meter, with the speakers on top of a 2-meter-high stand. The measurements were taken using quasi-anechoic technique (with Clio in MLS mode and 1/12th octave smoothing) above 250 Hz and ground plane (with Clio in log chirp mode and 1/3rd octave smoothing) below 250 Hz. For the subwoofer, I performed a ground plane measurement to get the total bass output of the active woofer and the two passive radiators. All results were imported into a LinearX LMS analyzer for post-processing. The SM65 and SM45 measurements were normalized to 0 dB at 1 kHz, and the SC8000 subwoofer normalized for peak output at +3 dB.

The SM65 measures pretty well, with a fairly flat frequency response across the ±30° listening window. There’s a bit of a peak around 14.5 kHz, but that shouldn’t be audible to most listeners. There’s also a rise around 2 kHz, which may be why I thought the sound was a bit bright. Off-axis response is very good; at ±45° and ±60°, there’s the expected treble rolloff at frequencies above about 2 kHz, and a peak of about 4 dB appears between 4 and 7 kHz. The grille reduces treble output by 1 to 3.5 dB above 2.5 kHz, which is a slightly bigger treble reduction than we usually see with most grilles.

Pretty much the same for the SM45: Its response is actually flatter up to about 3 kHz, but that makes the tweeter’s treble peak at 14.5 kHz appear more prominent — at least to the measurement microphone. Its small off-axis anomalies are similar to those measured in the SM65, as are the effects of its grille.

Impedance of the SM65 drops to a low of 3.1 ohms at 200 Hz, but the phase angle at that frequency is just -0.1° and the impedance averages about 7 ohms. For the SM45, it’s 3.3 ohms/-33° phase angle at 125 Hz. Sensitivity (average of quasi-anechoic measurement from 300 Hz to 10 kHz at 1 meter at 0° with a 2.83-volt RMS signal) of these speakers is rather low, though: 85.3 dB for the SM65, 82.8 dB for the SM45. So while the impedance won’t be tough for a cheap receiver to handle, the power demands indicate you’ll get the best results with a receiver or amp rated at least 80 watts or so per channel.

I included a frequency response chart showing the SuperCube 8000’s various EQ modes. EQ off (orange trace) measures pretty close to flat. All of the EQ modes boost overall output. EQ1 (blue trace) delivers a huge, 11-dB boost at 40 Hz. EQ2 (red trace) boosts about 5 dB at 48 Hz and rolls off the deep bass below about 35 Hz. EQ3 (green trace) boosts 10 dB at 50 Hz. EQ4 (purple trace) boosts about 9 dB at 70 Hz and also rolls off deep bass below about 50 Hz. The sub’s internal low-pass filter delivered a combined rolloff of about -20 dB/octave.

CEA-2010 output measurements for the subwoofer were taken at 2 meters and then scaled up 6 dB per CEA-2010 requirements so that they are equivalent to 1-meter results. An “L” appears next to those measurements in which maximum output was dictated by the amplifier’s internal limiter. Averages are done in pascals as per the revised (but as of press time, still unpublished) CEA-2010 standards. Just for kicks, I also ran CEA-2010 on the SM65, driving it with a Krell S-300i integrated amp.

Results for the SuperCube 8000 were a little unusual. The output of most large subs at the 40-, 50-, and 63-Hz measurement points is usually dictated by the internal limiter, but with the SC8000, I bumped against the limiter only at 50 Hz. At 63 Hz, what sounded like a mechanical buzz (the driver hitting the grille fabric, maybe?) limited the max usable output. Also, at 25 Hz I encountered a weird noise that sounded somewhat like the speaker driver bottoming out, although it could have been a noise from one of the passive radiators, too. Seems to me the limiter should clamp down on the amp before the drivers are stressed to this point. Anyway, the SC8000 averaged 117.6 dB in the low bass (40-63 Hz) and 106.4 dB in the ultra-low bass (20-31.5 Hz). Those are respectable numbers — especially the ultra-low bass number, which is just 11.2 dB below the low bass number.

The SM65 put on a good show, too, delivering an average of 108.1 dB in the low bass octave. That’s comparable to a typical 8-inch subwoofer. But that’s just for one SM65; figure on roughly an extra 6 dB for a pair. You won’t get much output below that, though — I got measurable results at 31.5 Hz but nothing much but distortion at 25 Hz. — B.B.