Acoustic Research AR-1 loudspeaker Page 2

A second-order high-pass passive filter at 120Hz separates the woofer from the dual 5.25" midrange units. A fourth-order active low-pass filter, set for 100Hz, is integrated into the woofer amplifier. The midrange units cover the audio spectrum from 100Hz up to 2.5kHz, where they cross over to the tweeter via a second-order high-pass network. Mylar capacitors and low-DC-resistance iron-core and air-core inductors are employed in the crossover.

The new AR-1 features a single pair of multi-way speaker binding posts, instead of the two pairs on the P315HO. Connections can be made with single banana plugs, or the binding-post lugs (said to be hexagonal, but round on the review samples) can be unscrewed to expose side holes for speaker wire. In addition, the new rear service panel contains a detachable AC power cord, a woofer amplifier on/off switch, and a power-indicator LED that glows red in standby mode, and green when a signal is sensed. There is a line-level LFE input jack for the woofer amplifier, and an LFE output jack as well. Finally, there is a small rotary gain control, labeled "30Hz Low Frequency Level Trim," for adjusting the woofer's output for room-placement effects. Unlike the P315HO, the AR-1's gain control no longer affects the critical balance of woofer and midrange outputs. The control's settings now indicate a single reference level for the woofer in normal environments, as well as allowing a ±6dB range of adjustments.

Threaded spikes are provided for leveling the cabinets. To preserve my living-room floor's finished wood, I tested these speakers sans spikes...

Setup
Setup of the new AR-1 proved much less time-consuming than the earlier 315HO version because the woofer-level control no longer affects the midrange response. But position and orientation of the speakers required trial and error. Initially, the AR-1's side-firing woofers were set up facing outward, but this caused a wall cabinet to vibrate during sinewave sweeps.. I reversed the loudspeakers so the woofers faced inward, toward each other. Room rattles stopped, and the overall bass response was smoother.

Next I tried to find the best listening position. I began sitting 16' away from the AR-1s. However, my nearfield listening chair produced far better soundstaging and imaging. Most listening for this review was done from this position, speakers and listening chair describing an equilateral 7' triangle, the speakers 7' from the back wall and 3' from the side walls. The AR-1s were also auditioned in my 15' by 10' study, which is furnished with wall-to-wall carpeting, an area rug, and a couch.

Next, I checked channel assignments and phasing using track 2 on Stereophile's Test CD 3 (STPH006-2). Final adjustments included listening to pink noise and low-frequency signal-generator sweeps, and adjustments of listening-chair position for optimal soundstaging and imaging. Standing up at my nearfield seat position caused mild dulling of the sound when listening to pink noise. This became more prominent nearer to the speaker..

However, with the tweeter 33" above the floor, my low seated position (at which my ears are 37" above the floor) minimized this dispersion anomaly as long as I remained seated. I could hear no changes in the pink-noise pattern—neither subtle dulling nor brightening—by slouching in the seat or by sitting up straight.

The AR-1's powered woofer helped minimize room effects on bass response after I had optimized the speaker's location for best imaging and midrange timbre. Adjusting the new AR-1's bass-level control to maximum made the percussion opening of the Eagles' "Hotel California" (from Hell Freezes Over, Geffen GEFD 24725) sound overblown and muddy. However, the midrange remained unaffected by this control, unlike the P315HO, where vocal chestiness or hollowness was produced in male voices by the extreme settings of the earlier speaker's bass-level control.

The AR-1's high sensitivity allowed my medium-powered solid-state power amplifier, the 100Wpc Mark Levinson No.331, to deliver high SPLs in my large listening room. The AR speakers were so sensitive that I could still hear a signal with the preamplifier volume control cranked all the way down. The Levinson No.331 delivered a strong sense of pace and deep, well-defined bass notes, but the sound seemed hard and more in-your-face on dynamic music. Switching to the more powerful Bryston 7B-ST monoblocks (675W peaks at 8 ohms) significantly widened the soundstage and sweetened the sound. As a result, most of my listening tests were conducted with the Brystons.

Once the loudspeakers were situated, the listening chair adjusted, and the amplifier chosen, I broke-in the speakers by playing my favorite rhythmic selections: David Hudson's Didgeridoo Spirit (Australian aboriginal didgeridoo music, Indigenous Australia IA2003 D), Fleetwood Mac's The Dance (Reprise 46702-2), and David Bowie's "Putting Out Fire," from the Cat People soundtrack (MCA MCAD-1498). This breaking-in proved important, for two sonic glitches that had occurred only when the AR-1's woofer was on gradually disappeared during the first 10 hours of listening.

When driving the AR-1s below 32Hz at high levels, the left loudspeaker made a loud rat-a-tat noise, as if it was bottoming out. The noise heard during continuous sinewave testing was never evident during the listening sessions. The amplifier in the left loudspeaker seemed also to be set at a much higher level than the AR-1 I was using for the right channel. Even so, the left AR-1 had useful output down to 28Hz, while the right AR-1 didn't produce much bass below 32Hz. Both the P315HO and AR-1 versions of the speaker emitted turn-on/off pops and static transient noise when I turned on the external driving amplifier, but the AR-1's noises were much softer. These noises occurred with both the Mark Levinson No.331 and Bryston 7B-ST monoblocks. It was best to turn on the external driving amplifier first, then switch on the AR-1's internal amplifier.

Sound
The AR-1 and P315HO listening sessions produced very similar findings. The AR-1 is voiced a bit brighter than the P315HO, making vocalists more prominent, but there were no other major differences in sonic profile. The AR-1s reached at least 32Hz in my room when swept from 40Hz down to 20Hz with my sinewave generator, compared to the P315HOs' 25Hz extension.

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