The Atlantic Technology AT-1 H-PAS speakers’ overall performance/value quotient is di. cult to overstate. In direct comparison with my everyday small monitors, which cost slightly more, the AT-1 matched their tonal balance, imaging, and transient ease very closely while adding at least an octave of true low bass. I know of nothing anywhere near its price range (or size) that goes as powerfully and honestly low without subwoofer support. The critical listener with a demand for true deep bass but no space or desire for a subwoofer will be challenged to do better.
Frequency response (at 2 meters)
34 Hz to 17 kHz ±2.6 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input)
Bass output (CEA-2010 standard)
Ultra-low bass (20-31.5 Hz): NA
Low bass (40-63 Hz): 103.5 dB
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters)
31.5 Hz at 89 dB SPL
95 dB average SPL from 31.5 to 63 Hz
99 dB maximum SPL at 63 Hz
bandwidth uniformity 94%
I measured the AT-1 standing on the ground, because it will always be used that way. Quasi-anechoic measurements were averaged across a ±30° listening window, with the various curves weighted to take into account the way speakers perform in a typical listening room. The H-PAS seemed to introduce a phase shift that threw off the bass-summing calculations in my LinearX LMS measurement system, so I instead performed a ground-plane bass measurement (with the speaker and microphone on the ground), then spliced this result to the averaged quasi-anechoic response.
The AT-1 exhibits essentially textbook frequency response, with basically flat response on-axis and only a mild treble decrease off-axis, plus slight dips at 1.8 and 3.6 kHz when the mike is moved to 45° off-axis. Cancelation and reinforcement due to floor bounce cause a dip at 440 Hz and a peak at 640 Hz, but they're both mild. The high treble is down quite a bit at 20 kHz, but few people will be able to hear that flaw. The grille has only a slight effect, causing a couple of -2-dB dips and peaks in very narrow bands above 4 kHz. The treble switch boosts the high end (above 2 kHz) by +1 dB or cuts it by -2 dB. The ground-plane measurement showed a -3-dB bass response of 30 Hz.
Impedance of the AT-1 measures almost flat, at 2.7 ohms minimum at 20 kHz and 4 ohms nominal. The impedance phase is also almost flat, with a maximum shift of just -23°. That impedance is a little low, but the speaker's relatively high sensitivity of 89 dB should make it easy for any halfway decent amp to drive.
Because Atlantic Technology claims outstanding bass output for the AT-1 relative to its size, I decided to measure it as if it were a subwoofer. I used the recently developed CEA-2010 standard for the measurements and data presentation, and also included measurements performed using our previous method for the sake of comparison. Although the measurement technique dictated by CEA-2010 is similar to the one we were using before, we've decided to switch in order to conform to an industry-standard method.
Bass-output measurements were a little unusual. Most speakers and subwoofers increase distortion gradually as the frequency gets lower. The AT-1, in contrast, has really good output in the top octave, drops only a little at 31.5 Hz, but has no usable bass response at the next CEA-2010 measurement point of 25 Hz. At this frequency, there was some output at the fundamental tone, but the level of the third distortion harmonic (75 Hz in this case) was too high for me to get a reading. At 20 Hz, it's practically all third harmonic and no fundamental. Thus, by the CEA-2010 standard, output in the ultra-low bass band of 20 to 31.5 Hz was unmeasurable, but output in the low bass band from 40 to 63 Hz was impressive at an average of 103.5 dB. Measured by our old standard, max SPL at 10% THD is 99 dB at 63 Hz, while average SPL is 95 dB and deepest usable bass response is at 31.5 Hz. -Brent Butterworth
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