Pros: smooth sound; good bass for small speakers; small and attractive
Cons: problems with tweeter controls and woofer surrounds; rolled off at frequency extremes
The Acoustic Research AR-4x loudspeaker has been around since probably the mid-1960s. There were several different versions of the AR-4 over the years, and I think the AR-4x was among the earlier versions. In any case, it's a small two-way loudspeaker with an 8" woofer and small cone tweeter. It's slightly smaller than the famous Dynaco A-25, maybe 19" tall, 10 1/2" wide and 9 1/2" deep.
A couple of months ago, I was able to come up with a pair in good working condition (I cosmetically restored the pair and sold it to a nice fella on the East Coast) and spent several weeks listening and evaluating.
The AR-4x is an attractive little loudspeaker in a typical late '60s early '70s way. It has very nice real walnut veneer, and the light, high quality screens make for a classy look. The AR badges that screw in to the screen frames add to the overall appearance.
(Note: As of early March, 2009, Epinions has moved this review into the wrong category. If you want to see a picture of the AR-4x, go to Google Images and enter Acoustic Research AR-4x.)
The speaker wire connectors on the back are good quality thumb screws. Attaching speaker wire is fairly easy. The thumb screws do not accept banana plugs, like the connectors of Dynaco A-25s do, but they're not as frustrating as the tiny screws of Dynaco A-10s.
The tweeter level of AR-4xs is controlled by a single continuous knob on the back of each speaker. This is an Achilles' Heel of AR-4xs: the potentiometers (affectionately known as "pots") tend to corrode over time, eventually silencing the tweeters, although the tweeters are actually in working order. In some cases, there are "sweet spots" on the pots, allowing the tweeters to function, but often one or both tweeters will be completely silent.
If you can find a fully functioning pair, the sound is quite nice. I would describe it as "dark" compared to Dynaco A-25s or Small or Large Advents, but it is still satisfying.
On classical music, the sound of the AR-4xs was particularly good. The rolled off high end, coupled with decent bass extension and nice micro-dynamics, yielded a smooth and satisfying sound. Strings were NOT steely, as they were with the KLH Model Seventeen. I could listen for long periods of time without fatigue. Interestingly, though, FM radio announcers DID sound a bit "chesty" as they had in my system with the original Large Advents. This suggests a "hump" in the upper bass/lower midrange.
On Keith Jarrett's Standards, Volume 1, the sound was mellow and pleasing. The leading edge of piano transients was muted somewhat, relative to more "high definition" speakers, and cymbals didn't have as much shimmer as they do in real life, but the overall presentation was enjoyable to listen to. Keith Jarrett's moaning (he moans along as he plays) was separated from the piano, bass and drums nicely. And the bass had good "throng" to it. The speakers did not sound wimpy, in spite of their small size.
On Govi's Seventh Heaven, a recording of "new age" guitar music with a Latin flavor, the AR-4xs sounded a bit TOO mellow. The sound of fingers on strings was lost, and there was a lack of air around the guitar. But the bass was at times actually a bit punchier than it had been on my Dynaco A-25s, though I doubt it extends as deep (smaller woofer and cabinet).
On Gordon Lightfoot's Summer Side of Life, Lightfoot's voice sounded good, full and manly, and the guitars sounded realistic. However, the sense of air around the guitars was again lacking somewhat. Still, I didn't find myself wanting to switch to speakers with higher resolution. I just enjoyed the music.
Imaging was pretty good with the AR-4xs. Because of the mellow balance, the instruments were presented behind the plane of the speakers, and they were located fairly well in space. But I have to admit that after awhile, I noticed the AR-4xs sounding a bit "closed in," relative to the other speakers I'd been listening to (Cambridge Soundworks Towers; Dynaco A-25s; New Large Advents). When I switched back to Dynaco A-25s, my "retro references," the soundstage became bigger and there was more air around individual instruments.
Still, my overall impression of the AR-4x was quite positive. I enjoyed the good micro-dynamics and laid back and warm presentation. The speakers played MUSIC and didn't call attention to themselves.
I should mention that AR-4xs came with two different versions of their 8" woofers.
The more dependable version has treated cloth surrounds, like many KLH speakers. These apparently don't deteriorate over time. But some AR-4xs have foam surrounds, like Advent (and some AR) speakers. These will require refoaming every 15 years or so. Cost of a refoam is from $50 to $100 per pair.
If you find a pair of AR-4xs and are considering buying them, try to get the screens off so you can check the woofers. Unfortunately, this isn't always an easy proposition, as AR used a very strong glue to attach the screen frames to the front baffles of the speakers. If the woofer surrounds are nice and soft, you probably don't need a woofer refoam. If they're hard, or break apart when you touch them, pass that pair on to a devoted hobbyist.
The tweeter control problems also deserve further mention. Rotate the tweeter level knobs on the back with your ear right next to the tweeter. Does the tweeter cut in and out? This is typical of AR-4xs in working condition. You can choose to live with it, finding the sweet spots where the tweeter works. Or you have have a hobbyist fix or by-pass the tweeter controls. If the tweeter is SILENT, rotate the knob back and forth several times. Sometimes you will be able to establish a connection. Often you will not. I am not an expert at fixing struggling AR tweeter potentiometers, but they CAN be fixed or replaced.
AR-4xs can often be found on Craigslist for under $100. But because of the problems described above, one can NOT count on such a pair to be functioning 100%. I think the incredible popularity of Dynaco A-25s comes from the fact that they are extremely dependable and don't suffer from woofer surround or tweeter pot problems. AR-4xs are fussier.
In terms of sound, I'd say the Dynaco A-25s are a bit more accurate than AR-4xs, but a fully functioning pair of AR-4xs is just as satisfying to listen to.
Dynaco A-25s in poor cosmetic condition but perfect working condition might cost you $90/pair on Craigslist or Ebay. A pair in perfect cosmetic AND working condition can cost up to $450 on Ebay (though $250 is a more reasonable price for a nice pair of A-25s). In contrast, I've seen AR-4xs go for as little as $50/pair, and rarely more than $200/pair. A pair of AR-4xs in perfect cosmetic and working condition is a real find and a good bargain.
To conclude, AR-4xs are attractive and good sounding vintage speakers, but their fussy nature means they may be best suited for the hobbyist who is ready and willing to deal with possible woofer surround and tweeter pot issues.
Still, if you find a pair in good cosmetic and working condition, snap 'em up. Listening to AR-4xs is like sipping a good cup of hot chocolate on a cold day!