On-axis: ±3.4 dB from 42 Hz to 20 kHz
Average ±30° horiz: ±2.6 dB from 42 Hz to 20 kHz
Average ±15° vert/horiz: ±3.0 dB from 42 Hz to 20 kHz
min. 3.8 ohms/397 Hz/-11°, nominal 6 ohms
Sensitivity (2.83 volts/1 meter, anechoic)
The first chart shows the frequency response of the UF5, the second shows the impedance. For frequency response, three measurements are shown: at 0° on-axis (blue trace); an average of responses at 0°, ±10°, ±20° and ±30° off-axis horizontal (red trace); and an average of responses at 0°, ±15° horizontally and ±15° vertically (green trace). I consider the 0° on-axis and horizontal 0°-30° curves to be the most important. Ideally, the former should be more or less flat, and the latter should look the same but should tilt down slightly as the frequency increases.
The response of the UF5 is quite flat overall. Because of that on-axis dip at 7.5 kHz (which isn't as apparent off-axis), the speaker measures flatter across either of the two measurement windows than it does off-axis. (Without that 7.5-kHz dip, on-axis response would be ±2.3 dB.) That dip is narrow enough, shallow enough and high enough in frequency that I doubt it would bother anyone. The one anomaly I see in the measurement that I expect would reveal itself readily to the ear is that peak centered at 2 kHz, which might make the speaker sound a little brighter but would probably also have the positive effect of enhancing voice intelligibility.
Off-axis response is fantastic, as expected from the concentric midrange/tweeter array. As you move farther off-axis, you get a nice, smooth, consistent treble roll-off with no significant dips in the midrange response, which is exactly the way decades of scientific research tells us a speaker should respond. The grille has a somewhat larger-than-average effect, reducing response by -1 to -2 dB between 2.3 and 6.8 kHz, and also introducing a couple of very narrow (and almost certainly inaudible) dips at 10.3 and 16.3 kHz. So, if the speaker sounds a little bright for your taste, the grille can tame the lower- and mid-treble response subtly but usefully.
The impedance of the UF5 is a little low, dipping below four ohms for a bit, but it can safely be called a six-ohm speaker. Sensitivity is a little on the low side at 83.6 dB (measured at one meter with a 2.83-volt signal, averaged from 300 Hz to 3 kHz), which means the UF5 can hit about 100 dB with about 40 watts. So it'll perform well with pretty much any receiver or halfway-decent amp, although I wouldn't recommend using it with one of those under-$50 Pyle or Lepai amps.
Here's how I did the measurements. I measured frequency responses using an Audiomatica Clio FW 10 audio analyzer with the MIC-01 measurement microphone, and the speaker driven with an Outlaw Model 2200 amplifier. I used quasi-anechoic technique to remove the acoustical effects of surrounding objects. The UF5 was placed atop a 36-inch (90cm) stand. The mic was placed at a distance of two meters at tweeter height, and a pile of denim insulation was placed on the ground between the speaker and the mic to help absorb ground reflections and improve accuracy of the measurement at low frequencies. Bass response was measured by close-miking and summing the responses of the woofers and the ports, and splicing this result to the quasi-anechoic results at 188 Hz. Results were smoothed to 1/12th octave. Measurements were made without the grille except as noted. Post-processing was done using LinearX LMS analyzer software.
As I stated above, the UF5 held up well in direct comparison with my Revel Performa3 F206 speakers, but there were a couple of tunes that showed the benefits of the F206's more costly construction. On "Wives and Lovers" from Frank Sinatra and Count Basie's It Might As Well Be Swing album, I could hear that the Revel's tweeter is better. It sounded smooth, natural, and free of sibilance on Sinatra's vocals; but, when I switched to UF5, I could hear a mild amount of sibilance. I also noted this effect on the Susie Arioli recording and the Thor Blu-ray disc.
Also, the F206s sounded a little more open and spacious, making the UF5 sound a little "boxy" in comparison. Given the UF5's demonstrably excellent dispersion, I think this might have been due to a mild resonance in the UF5's cabinet, which isn't as solid or well-braced as the 3.5-times-as-costly F206.
I noticed that the UF5 has a subtle trace of lower treble emphasis. I would describe the way it sounds as lively, not bright. However, if you're into a more relaxed, mellow sound, the UF5 might have a touch too much top end for you.
Comparison and Competition
There are lots of tower speakers around $1,000 per pair. The UF5 is at the very least competitive with any of the ones I've heard, and it's a better value than most because it's a three-way design and most of its competitors are 2.5-way designs, with a relatively large midrange/woofer driver plus one or two more matching drivers running only in the lower frequencies. While most of the major speaker companies have appealing offerings in this range, their larger midrange/woofer drivers might not allow them to sound as open and enveloping as the UF5's four-inch midrange/one-inch tweeter concentric array will. These speakers include the $449-each PSB Imagine X1T (a 2.5-way with dual 5.25-inch drivers), the $549-each Monitor Audio Bronze 6 (a 2.5-way with triple 6.5-inch drivers) and the $499-each Klipsch RP-260F (a two-way with dual 6.5-inch drivers). I can't say for sure which of these speakers you'd like the most because, of course, there's a certain amount of personal taste involved. I doubt you'd think any of them will sound substantially better than the UF5, though.
Tougher competition might come from the Definitive Technology BP9020, a $649-each, three-way bipolar design with a powered eight-inch woofer and dual passive radiators. I heard the BP9020 at a recent event and was pretty impressed. I doubt it'll match the UF5's sonic purity, but the bipolar design will likely sound even more enveloping, and the powered bass section will almost certainly deliver deeper bass response than the UF5 can muster.
I've heard a huge number of $1,000-per-pair tower speakers. I did my first shootout of them for an industry magazine about 20 years ago...and the UF5 is the best I've heard to date. It's a great value, it's impeccably engineered, and it simply sounds great. Plop a couple down in your living room, hook 'em up to a decent receiver or amp, and you'll experience some of the best sound the audio biz has to offer--at a cost that an average household can easily afford.
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