KLH Model Six: A Wonderful Vintage Speaker, Especially for Classical Music
Feb 15, 2009 (Updated Mar 3, 2011)
Review by Horswispr
Rated a Very Helpful Review
The KLH Model 6 (sometimes written as Model Six) is among the classic loudspeakers from the 1960s and 1970s. It was the first full-range two-way loudspeaker designed by audio legend Henry Kloss, and it was probably influential in the design of Kloss's even more famous Advent Loudspeaker.
Recommend this product?
The KLH model 6 is a fairly large acoustic suspension loudspeaker, measuring about 23 1/2" tall, 12 3/4" wide, and 11 3/4" deep. KLH 6s weigh more than my beloved Dynaco A-25s, but less than Acoustic Research AR-2axs or Large Advents. I'd guess their weight to be about 32 pounds each. Each cabinet contains a nominal 12" woofer (KLH's literature claims it to be a 12", but I measured it and found the to be a bit larger than the Dynaco A-25's 10" woofer and a bit smaller than the Large Advent's 12" woofer) and what appears to be a medium sized cone tweeter hidden behind a protective screen.
On the back is a three-position tweeter level switch, similar to the one found on the Large Advent Loudspeaker. The speaker wire attachments are high quality thumb screws similar to those found on '60s and '70s Acoustic Research and Advent speakers. The cabinets of KLH 6s are finished in attractive real walnut veneer, and the screens are sometimes a medium brown color and sometimes a light beige (it could be described as "off-white") color. The earliest versions of the KLH 6 had the drivers epoxied directly to the front panels and the screens glued in as well; no access to the drivers. Later models allowed access to the drivers from the front. I believe the KLH 6 was made from 1958 through 1972.
I recently had a chance to listen extensively to a pair of KLH 6s in my home system while refinishing the wood cabinets for a local vintage audiophile. The owner had replaced the capacitors in the crossovers, as well as the speaker wire connector termnals, but otherwise left the speakers intact; the woofers and tweeters were original.
Set-up and aesthetics.
The KLH 6s are easy to set up. Hook up the speaker wires, place them on stands or in a large bookshelf, adjust the tweeter control to your liking, and you're ready to go. The speakers aren't particularly heavy and are easy to move around.
The KLH 6s are very attractive if you like the basic look of KLH, Acoustic Research and Dynaco speakers of the early 1970s era. They are finished in real wood veneer (not the black vinyl cr-p found on many contemporary speakers) and the look is understated and classy. If the grille cloths are torn or just plain tired looking, you can replace them with the cloth of your choice (assuming you have the later ones with removable grilles). If the speakers are worn due to age, they refinish easily. Here's a link to pictures of a decent pair, grilles on and off. These grilles are the lighter beige ones that I actually prefer to the darker medium brown ones.
I used my home stereo for all listening. My gear includes the following: NAD 521BEE CD player, AR ES-1 turntable with Shure M97xE cartridge, conrad-johnson MF-80 power amplifier, modded older Musical Fidelity preamplifier, and an M&K V-2B subwoofer. Comparison speakers include: Cambridge Soundworks Towers, Dynaco A-25s, Acoustic Research AR-2axs, and Large Advents.
To cut to the chase, I really like the sound of the KLH 6s. They err on the side of the smooth and mellow, and they are easy to listen to over long periods of time. And yet, in spite of their mellowness, there is a lot of information there. Imaging in particular is surprisingly good, with the sound spread behind the plane of the speakers and instruments easy to locate. I was also pleasantly surprised by the speakers' "microdynamics": subtle things like the sound of sticks on drum skins or guitar strings struck with different intensities came through well.
But what really won me over was the overall musicality of these speakers. I found myself forgetting about the speakers and listening to the music itself. They were particularly good with classical music, with the smooth sound and good soundstage leading to a convincing presentation.
The bass was good, relatively tight and with some visceral impact, but it was not as tight, nor did it go as deep, as the bass of Large Advents. However, I found the midrange presentation to be smoother than that of Large Advents. Especially with clasical music, it was easier to forget about the speakers and just listen to the music.
On rock and jazz, the presentation of the KLH 6s was a bit on the mellow side, but I still enjoyed it. Drums and cymbals were not as convincing as with my reference Cambridge Soundworks Towers, but they still sounded good. Vocals were presented naturally and without annoying excess sibilance. The visceral impact of kick drums and bass guitar (both electric and stand up) was down a bit relative to Large Advents, but it was still pretty good, proabably a bit better than with Dynaco A-25s, another really nice, mellow sounding speaker.
On solo acoustic guitar, the KLH 6s were very musical, and the space around the guitar was presented surprisingly well, though not as well as with Cambridge Soundworks Towers. The sound of fingers on strings was subdued a bit, but it was there.
On jazz music, the sound of the KLHs was musical and satisfying, but I sometimes wished for more attack from the bass and drums and more energy from the cymbals. In my suburban location, I can only get KDFC, the Bay Area's best jazz station, in mono, and I spent a good deal of time listening to KDFC using a KLH 6 on the left and a Large Advent on the right, as I worked on the other KLH. I had to adjust the balance control on my pre-amplifier to the left a bit, as the KLH 6s are apparently slightly less efficient than the larger Advents, but once I had things dialed in, the sound was fantastic. Both speakers have that Henry Kloss "East Coast" sound, with a slight warmth and mellowness to the presentation, and so there was no sense of a mismatch as I listened. The Advent provided a little extra snap and a little extra bass; the KLH proived that overall sense of smoothness that I find seductive.
If I were building a high quality vintage system, I could easily live with the KLH 6s. Their overall smoothness and musicality won me over, and I found myself smiling a lot as I listened to them, regardless of what kind of music I was listening to.
No, they're not quite as refined as my reference Cambridge Soundworks Towers, but they're pretty darned close when it comes to providing an overall sense of musical satisfaction. Compared to original Large Advents, I find the KLH 6s to be a bit smoother and more musical, though quite similar in overall personality. The Advents have more extension at the frequency extremes, however. Compared to Dynaco A-25s, the KLH 6s are a bit warmer and more relaxed, as well as more dynamic. And compared to Acoustic Research AR-2as, another high quality acoustic suspension speaker from the same era, the KLH 6 sound a bit cleaner to my ears. I also thought the KLH 6s imaged a bit better. Interestingly, the AR-2ax is a three-way speaker, while the KLH 6, Large Advent and Dynaco A-25s are all two-way speakers. I sometimes found myself wondering, while doing these comparisons, if vintage two-ways aren't just a bit cleaner sounding than three-ways, perhaps due to the simplicity of the crossovers.
In a high quality vintage system, you can't go wrong with with a fully restored pair of KLH 6s, Large Advents, AR2axs, or Dynaco A-25s. Each has its own strengths, but all sound surprisingly good. New Large Advents, which came out in the early 1970s (and were voiced slightly differently than the original Large Advents), are also among my favorite speakers of the 1960s and 1970s. For classical music especially, the KLH 6s just might be my favorites.
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