Acoustic Research AR-90 vs. KEF 107-1

[Dan Mui]

It is time for me to write a comparison between my AR-90s, BA-T1030s and recently acquired vintage KEF 107-1s. I previously wrote about my AR-90 vs. BA-T1030 in this forum back in late 2020.

 

I got my KEF 107-1s in excellent condition approximately three months ago from a seller who no longer uses them. My seller got them for free from the original owner, who is an internationally renowned individual. The seller sold them to me at well below market value.  Since they are not the kind that you bi-amp, they were new likely built circa 1986 to 1988. The KEFs do not have the KEF Kube.

 

I disassembled the speakers and refitted the 4-10” woofers with new surrounds. I touched up the already beautiful solid (does not look like veneer to me) rosewood cabinets. The crossovers are in like-new condition without any signs of leakage.  All the components, including nuts and screws, are top-drawer stuff.  Fit and finish of the speakers are the best that I have ever worked with. It took me nearly two weekends (25 hours) to finish.   

 

About a month ago, I inspected the mid- and high-range crossovers of the AR-90’s carefully.  They were in great shape physically and I found no leakage. I then listened to the high- and upper mid-range of the AR-90 carefully with respect to the Optimus Linaeum tweeters on top of the AR-90. Other than a bit less sensitive than the added-on tweeters, they sound alike.    

 

Sound

I have listened to the KEF 107-1 and the AR-90 (mostly) in the last three months using the same Sony S-Master Pro Class-D STR-DA7100es receivers and Denon DVD-2900s.  The Sony Class-D has no distortion or noise to speak of. Far quieter than any tube or Class A/B amplifiers that I had. The Sony is very natural, yet analytical. The sound of BA T-1030 went to another room which displaced the AR Holographic Imaging M6.  I sold the AR M6 to a friend, who is very happy with them. I compensated for the lack of the Kube by increasing the bass & treble (a bit too recessed) by 3dB on the Sony.  The 3dB boosts are sufficient without making the music sound over boosted. The bass boost is somewhat more noticeable. I keep Linaeum tweeters sitting on top of (AR-90) or behind (KEF) each pair of speakers.  The Linaeum and the KEF are nearly identical in sound and volume (matching sensitivity). Less so for the AR-90 as it is less sensitive than the KEF (87 vs. 90dB).  Here are my observations.

 

1.     KEF 107-1s have more holographic and out-of-the-box sound, depth, better (maybe even more precise) imaging and very musical and sound very natural.  The small heads on top of the band-pass bass cabinets eliminate the issue with sound reflection from the surrounding sides of the cabinets.  The AR-90s use acoustic blankets but are not as effective with respect to the heads of KEFs. The KEF sound is noticeably darker (but not greatly) than the AR-90 even with the boost in the treble. In a quick comparison, one might even think the AR-90 sounds more entertaining and has more flares. However, longer listening session will point otherwise. Both speakers are very musical, and I guess (to say) that AR might voice the AR-90 to satisfy a wider spectrum of audience (East plus a bit of West coast sound). To my ears, the KEF is another level above the AR-90 in terms of musicality, soundstage, imagining & naturalness.  Both female and male voices are a bit more realistic from the KEF. The KEF bass is top quality, solid but musical without feeling like listening to a quality boombox in a house or car.  There is hardly any pressure from the bass even at much higher volumes. The bass, mid-range & treble are so well integrated that there is more unity than the AR-90. This might have to do with the all drivers are in the box of the AR-90s. 

2.    The BA T-1030 speakers’ sound in-between the AR-90 & KEF 107-1. They are closer to the KEF 107-1s sound-wise than the AR-90s. However, they still sound more so within the box, less holographic and a bit more brittle/less sweet than the KEFs. Simply put, the KEF uses high quality drivers and parts. Their crossovers were well-designed, which contribute to the quality of the imaging. I briefly heard a pair of an earlier Harbeth Monitor 40 from the BA-T1030 seller several years ago. I thought the BA-T1030 sounded better, but now I realize that the BA T-1030 may be just more entertaining but not necessarily better or correct.

 

However, I love all three pairs.

[AR surround]

I agree with your comparison.  I had an opportunity to audition a KEF 105 vs the AR9.   The KEF 105 was very precise, etc etc.  I found that I liked the way it handled classical music more so than the AR9.   The moveable heads really had that 'cool' factor and accommodated  optimization for the sweet spot.  However, when switching to rock / popular music I preferred the AR9.

I do not care that the AR spec calls for placing the AR9 against the back wall, etc.   Mine sound much better and more 'holographic' and with more depth when pulled out into the room and toed in towards the main listening position.

 

[Dan Mui]

The unity of KEF sound is likely that the bass output is from the front top slot of the cabinet.  I think it is only exclusive to Model 107, not other KEF models with the band-pass design in that era (late 80s/early 90s).