Tower Speaker Reviews

Bottom Line

Monitor Audio’s Gold GX system is a well-crafted speaker package that’s capable of pinning you to the couch on movies and drenching your ears with detail on music. If there was one shortcoming I unearthed during my time with it, it was that perhaps the GX200 towers are too revealing: Bright recordings could sound a bit in-your-face, though I can’t say I ever really found the presentation fatiguing. Its price is perhaps higher than the average speaker buyer might be willing to pay, but then again, the performance of this Monitor Audio system is anything but average.

Test Bench

Frequency response

• tower 36 Hz to 20 kHz ±2.7 dB
• center 55 Hz to 20 kHz ±2.5 dB
• surround 66 Hz to 20 kHz ±7.4 dB
• subwoofer 29 to 216 Hz ±3 dB

Sensitivity (SPL at 1 meter/1 watt)

• tower 86.7 dB
• center 86.1 dB
• surround 86.9 dB

Impedance (minimum/nominal)

• tower 3.3/6 ohms
• center 3.1/6 ohms
• surround 4.3/8 ohms (monopole), 3.7/7 ohms (dipole)

Bass output, tower (CEA-2010 standard)

• Ultra-low bass (20-31.5 Hz) average: 82.6 dB

20 Hz, NA
25 Hz, 79.5 dB
31.5 Hz, 89.5 dB

• Low bass (40-63 Hz) average: 110.0 dB

40 Hz, 107.2 dB
50 Hz, 111.3 dB
63 Hz, 111.0 dB

Bass output, subwoofer (CEA-2010 standard)

• Ultra-low bass (20-31.5 Hz) average: 103.3 dB

20 Hz, 99.3 dB
25 Hz, 101.7 dB
31.5 Hz, 107.1 dB

• Low bass (40-63 Hz) average: 121.8 dB

40 Hz, 119.9 dB L
50 Hz, 122.0 dB L
63 Hz, 123.1 dB L

Bass limits

• center 86.8 dB at 31.5 Hz
• surround 84.6 dB at 31.5 Hz

Because of the differing configurations of the Monitor Gold speakers, I had to measure each one in a different way. All were measured quasi-anechoically with my Clio FW audio analyzer in MLS mode. I placed the GX200 tower directly atop my measurement turntable and used 2 feet of attic insulation to absorb reflected sound from the ground. I placed the GXC 150 center speaker atop a 2-meter stand and placed the microphone at a distance of 2 meters, enough to incorporate the contributions of all the drivers plus diffraction off the cabinet edges. I attached the GX-FX surround speaker to an ersatz “wall” made from a 2 x 4-foot piece of plywood attached to 2 x 4 studs, with foam on the edges to prevent diffraction, then attached the studs to my measurement turntable. For the tower and center, the curve shown here represents the average of responses at 0°, ±10°, ±20°, and ±30°. I measured the surround speaker in monopole mode using the same averaging scheme, because in this mode it is intended to function much like a bookshelf speaker. However, I measured it in dipole mode using an average of responses at 0°, ±15°, ±30°, ±45°, and ±60°. All results are smoothed to 1/12th octave. All speakers were measured without grilles, then measurements with grilles on were made for comparison.

For the center and surround speakers, the quasi-anechoic frequency response measurements described above were spliced at 220 Hz to close-miked measurements (with the Clio FW in log chirp mode) of the speakers’ woofers. For the tower, I performed a ground plane measurement with the Clio in sine mode to get the total bass output of the two woofers and the port, and spliced this to the quasi-anechoic curve at 250 Hz. The subwoofer’s frequency response measurements were made using close-miking. All results were imported into a LinearX LMS analyzer for post-processing.

Speaker measurements don’t get a whole lot better than these. Let’s start with the GX200 tower, which measures ±2.7 dB throughout its range. Most speakers can’t achieve that even at 0° on-axis; achieving such a flat measurement across a ±30° listening window is outstanding. Off-axis response is nearly perfect, with just a slightly increasing treble roll-off at 60° off-axis. The grille has almost no effect; it merely reduces the response between 9 and 12 kHz by an average of -1.5 dB.

The GXC 150 center speaker’s response is even flatter, at ±2.5 dB. It has surprisingly deep response at low signal levels, although it can’t match the GX200’s deep bass output. As usual with a woofer-tweeter-woofer center speakers, you get big dips in response of -20 to -25 dB at angles of 20° or more off-axis (caused by interference effects between the two woofers), but the frequencies of the dips change at different angles in a way that averages out to an extremely flat response across the listening window. Again, the effect of the grille is negligible: -1.3 dB at 10.7 kHz, and a boost averaging 1.5 dB between 12.7 and 18.7 kHz.

The GX-FX surround has very flat and smooth response, much like that of the GX200. That big dip you see in the response, centered at 380 Hz, is a cancellation effect caused by mounting the GX-FX on a wall. Without that dip, the response in monopole mode would be ±2.8 dB. Response in dipolar mode is ±8.1 dB, and is noteworthy for stronger-than-average treble response for a dipolar speaker. The grilles cause fairly random and mild (max ±2.2 dB) response anomalies above 2.5 kHz.

Impedance of the tower runs below 5 ohms between 90 Hz and 1.2 kHz, and hits a low of 2.5 ohms at 130 Hz with a phase angle of -21°, so you’ll want to use this speaker with an amp with strong rated output at 4 ohms. The center speaker presents an easier load, running above 6 ohms for most of the audio range with a minimum of 3.5 ohms/-11° phase at 170 Hz. Impedance of the surround in monopole mode bottoms out at 4.3 ohms at 217 Hz with a -1° phase angle. In dipolar mode, the minimum impedance is 3.7 ohms at 450 Hz with a +12° phase angle. No matter what mode you’re in, the surround isn’t tough to drive.

Sensitivity (average of quasi-anechoic measurement from 300 Hz to 10 kHz at 1 meter at 0° with a 2.83 volts RMS signal) is about average for all models: 86.7 dB for the tower, 86.1 dB for the center, and 86.9 dB for the surround (in monopole mode).

The subwoofer’s frequency response in its factory reset condition from its LFE input spans 29 Hz to 216 Hz with the EQ bypassed. EQ1 cuts the output by max -6.2 dB in a band centered at 50 Hz, but the band is so broad, stretching from 25 to 150 Hz, that the effect of this setting will be mainly to lower the sub’s overall output. EQ2 is the same as the EQ off setting except that the deep bass rolls off more; it’s down -13.3 dB at 20 Hz compared with the EQ off setting. EQ3 kicks up the response between about 50 and 140 Hz by a max of +3 dB, and rolls off the deep bass response -10.4 dB at 20 Hz compared with the EQ off setting. Setting the low-pass filter (i.e., crossover) to 80 Hz produced a -25 dB/octave roll-off.

CEA-2010 output measurements for the tower speaker and subwoofer were taken at 2 meters then scaled up +6 dB per CEA-2010 requirements; an L appears next to those measurements in which maximum output was dictated by the subwoofer’s internal limiter. At press time, the CEA had instituted changes to the CEA-2010 standard but had not published them; however, they did tell me that the new standard requires averaging in pascals rather than in dB, so that’s the procedure I followed here.

I measured the output of the GX200 tower using my Krell S-300i integrated amplifier to power the speaker. Low bass (40-63 Hz) performance is good for a slim tower, comparable to that of conventional 8-inch subwoofers. There’s not much output in the ultra-low bass (20-31.5 Hz) band, though. (I wasn’t able to get a measurement at 20 Hz, so to perform the ultra-low bass average I used the 25 Hz measurement and subtracted -18 dB, per CEA-2010 procedure.) Averaged using pascals (the new method) and dB (the old method), the results are: low bass 110.0 dB/109.8 dB, ultra-low bass 82.6 dB/76.8 dB.

The GXW-15 subwoofer’s output (measured at factory reset with EQ off) is extraordinary in the low bass (40-63 Hz) octave, roughly equaling that of the much larger Hsu Research VTF-15H I keep around as a reference. However, it can’t muster as much ultra-low bass (20-31.5 Hz) output as many larger 15-inch models can. While there’s a decent amount of energy down low, this is more what I call a “punch sub,” seemingly designed to deliver maximum impact rather than the deepest possible response. Averaged using pascals/dB, the results are: low bass 121.8 dB/121.6 dB, ultra-low bass 103.3 dB/102.7 dB. — Test Bench by Brent Butterworth