AR-7 and AR-4x

[ninohernes]

What is the difference between these two models besides the crossover point? They both have an 8 inch woofer and a small cone tweeter. Which system is better? The 4x or the 7. I have only listened to the 4x's, I have never heard the 7's before.

[Steve F]

The AR-4x was the successor to the AR-4, AR’s first "small" speaker. The 4x was introduced in the 1966 timeframe. It had an 8" woofer with a treated cloth surround and a 2 1/2" tweeter. The change from the original 4 to the 4x entailed the replacing of the 4’s 3 1/2" tweeter (the same driver used as the midrange in both old and new 2ax's, and used as the tweeter in the original 2x) with the 2 1/2" cone tweeter (the same driver as in the ‘new’ 2x and the 1x.)

In the May 1966 Consumer Reports magazine, the 4x received a spectacular rating, clearly outdistancing all the other speakers tested in a 22-model comparison roundup. "…the best of the lot, the AR-4x, handled these upper ranges as well as any other speaker, no matter how big or expensive, ever put through its paces in our laboratory," they said. And also, "The smoothest response in the test, and one of the smoothest, widest-range loudspeakers ever tested by Consumer Reports."

Julian Hirsch, speaking in Stereo Review said, "This frequency response would be remarkable for any speaker, and in our experience is unique for any speaker in the price class of the AR-4x…We know of no competitively-priced speaker that can compare with it."

High Fidelity magazine said in 1967, "In direct A-B comparison with the costlier AR-2ax, there are moments when the two are indistinguishable."

The 4x was a truly groundbreaking product, delivering first-rate smoothness and musical accuracy in a manageable size at an affordable price.

The 4x’s 8" woofer had a free-air resonance of 30Hz, and it was mounted in an enclosure of .654 cu. ft. volume, resulting in a system resonance of 65Hz. The woofer crossed over to the 2 1/2" tweeter at 1200Hz. The low crossover frequency allowed the 4x to maintain an extremely smooth power response in the midrange, because the tweeter was brought in long before the directional effects of the woofer’s midrange response became objectionable. Some people claim that the low tweeter crossover caused the tweeter to be fragile and prone to blowing, but we never once had a problem in 7 years (1968-1975), playing a wide variety of jazz and classical music at healthy volumes, using a 60 watt RMS/channel Sherwood S-7900A receiver. The 4x ranged in price from $57 ea. unfinished to $63 ea. in oiled walnut veneer.

So AR had set a pretty high standard for compact loudspeakers for both themselves and the rest of the industry. It was going to be difficult to come up with something compellingly new and better at the low end of their product range.

But they did. When the AR-7 was introduced in late 1972/early 1973, AR had correctly seen the need for a high-performance small speaker whose dimensional proportions allowed it to fit easily on shelves (perfect for dorm rooms), be mounted on the wall without awkwardly sticking out too far into the room, or be used in fours for the (thought to be) emerging 4-channel music market. The 7 was one of the best marketing reads ever by AR.

An early AR ad showed four AR-7’s stacked on their backs, with their 4 x 6 1/4" depths being exactly the same height as the 25" tall AR-3a. It was a dramatic presentation of the speaker’s diminutive size, and brought home the size-to-performance story very effectively.

The AR-7 used the new 1 1/4" cone tweeter, introduced in the AR-6 two years previously. The 7’s woofer had a free-air resonance of 25Hz (same as the 6), mounted in an enclosure of .345 cu. ft. for a system resonance of 68Hz (compared to a system resonance for the AR-6 in its larger enclosure of 56Hz). Therefore, as a result of its woofer’s lower resonance, the 7 had very nearly identical bass response to the 4x, in spite of the 7’s cabinet being markedly smaller. Incidentally, a 25Hz free-air resonance for an 8" woofer is almost unheard of today. Most 12" OEM woofers used by the major commercial speaker companies nowadays have a free air resonance of 25-30Hz. I’d hazard the guess that there is currently not a single 8" woofer used in any low-priced speaker from a mainstream manufacturer that has a resonance anywhere near as low as the 7’s. It was really something.

The AR-7’s voicing was also different than the other 1 1/4"-equipped Classic AR speakers, the AR6, AR-8, and AR-4xa. In both listening tests and a review of their measured frequency response curves as published in High Fidelity magazine, the AR-7 can be seen to have 2-3dB greater output in the 6-8kHz range than the others, and this agreeable characteristic imbued the 7 with an extremely alluring sonic signature from an almost impossibly compact package. (Whether the voicing difference was intentional or simply the result of a slightly different interaction, system-wise, between the drivers and the enclosure, is tough to say. However, the result was quite favorable.)

The 7 differed from the 4x in having a two-position tweeter control ("flat" and "norm," a 2dB drop between the two settings) instead of the 4x’s continuously variable tweeter control.

The 7 crossed over at 2000Hz, compared to the 4x’s 1200Hz. Although 1972 was still 3 years before the introduction of ferro-fluid cooling in the voice coil gaps of tweeters, I’m fairly certain that Roy Allison used silicone grease in the voice coil gaps of the 1 1/4" tweeters to aid in heat transfer and increase power handling.

For years, Julian Hirsch had a pair of AR-7’s wall-mounted in his lab. I noticed them every time I was there, but I never mentioned anything about it. Finally the last time I was there, in 1998, I knew he was retiring, so I figured it would be "safe" to ask him about them. He told me, "Well, I put them up when I reviewed them for Stereo Review in 1973, and they were such remarkably good sounding little speakers, I never took them down. I still listen to them from time to time."

The AR-7 was the first AR speaker to be finished in vinyl –not real wood—veneer, a concession to their amazingly low price (when introduced) of $60.00 ea. It was also the first AR speaker to be packed two to a box. (Even the small AR-6 and AR-4x had been packaged individually.)

A direct A-B comparison between the 4x and 7 would show very comparable bass response, but the 7 has a somewhat livelier, more widely dispersed high end. I would judge both of them to be unquestionably the best compact speakers of their day: the 4x in the late 1960’s and the 7 in the early 1970’s.

Steve F.

(I trust that this is a "legit" answer!)

[ninohernes]

Thanks for the explanation. I realy like my 4x's. They are part of a system that is going to college with me, while my "big" system stays at home. I have the AR-4x's and a 50 watt per channel onkyo receiver, which is a great sounding receiver for its price. At home my moitors in my studio are AR-2's being driven by an Adcom GFA-5400 (125 watts per channel). In the living room are my fathers AR-3's being driven also by an Adcom GFA-5400, but at 4 ohms its 200 watts per channel. I am a senior in high school right now, but last summer I had the oppertunity to take some classes at the college that I am going to, Columbia College in Chicago. I am going to major in Audio Arts and Acoustics with a concentration on recording. I had the 4x's in my appartment with the onkyo, and they made excelent "portable" nearfeild monitors for mixing and mastering. I have listened to small monitors that cost thousands, and none of them sound as good as the 4x's. They really kick! My friends can never believe that there is no sub woofer. I always say subs are for sissys! The 4's sound twice thier size. The only thing about the 4's is they are not really sealed. The dust cap is vented and the sides of the magnet are open. My woofers have no tape around them. I really dont care, they sound excelent.

[tysontom]

SteveF's reply on the AR-4x and AR-7 is simply great, and I think it is extremely accurate with just one tiny addendum: the AR-7 was originally offered in a wood finish, but it was not Walnut. It was a Walnut-finish Birch with an oil finish. Later AR-7s were vinyl.

--Tom Tyson