The KLH Model Seven's sealed enclosure makes them easy to place, even in acoustically challenging rooms.
The Willing Suspension of Bass
"One of the delightful things about the sealed-box, acoustic-suspension, single-degree-of-freedom speaker is that it's a quite simple system, with an attendant lack of eccentricity."
So wrote KLH founder Henry Kloss in a 1971 article for Audio. In it, he cited Hofmann's Iron Law, which says that speaker designers get to pick just two of these three key parameters:
- Small enclosure volume
- Deep bass extension
- High efficiency
In other words, if you want a smaller enclosure with deep bass, you'll end up with very low efficiency. In the early 1950s, amplifier power was a precious commodity, so loudspeaker designers did not want to give up on dB per watt, but certainly wanted to offer lower bass. So they effectively increased enclosure volume with ports, allowing for more bass and loudness at a given power, but with, as Kloss put it, an "attendant eccentricity."
Kloss' big realization at the time was that amplifier power will get cheaper and more abundant, so he chose lower efficiency sealed designs, reasoning that it's better to spend on amplifier wattage than live with the compromises of ported cabinets. (Either that, or following Hofmann's law, create massive loudspeakers.)
Acoustic suspension, as sealed designs are known, doesn't offer as much low end as a similarly sized ported speaker, but does offer extremely high-quality bass. Thanks to computer design and modeling, today's ported designs are drastically less compromised, but even so, you'll immediately understand what Henry Kloss was after when you hear the coherence and agility of the bass notes of KLH's sealed designs.
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This is the KLH Model Three, but you can see the same high-quality wood-grain finish and fabric grille.
Listening to the Model Seven
When a new product is released, we can't wait to rip the demo unit out of the box and get it going. It was no different with the Model Seven: just minutes after arrival, it was hooked up and being broken in.
Joel Bennett, Upscale Audio sales associate, said they reminded him of the old Boston Acoustics A150 he bought for his father. "They have the same New England School of Audio Design sound. The mids and the highs are smooth and lively, and 'squeaky clean' without any hardness or glare."
Ken Davis, our sales manager, had a very similar reaction. "They are large speakers that throw an even larger soundstage. Mids are smooth and rich. The highs have a faint hint of sparkle that is polite and not biting."
Ken noted that the mid and tweeter placement is asymmetrical which gives you an extra in-room adjustment: In most cases, place the drivers to the outside for the widest soundstage, but in narrow rooms or with a lot of side reflections, it can help to swap left and right speakers, thereby putting the drivers on the inside.
No speaker is without a downside and Joel found the Model Seven didn't acoustically disappear as completely as narrower speakers in the same price range. But to make up, he says, "The bass is stunning and seems much lower in extension than the specs would indicate."
Ken observed that the Model Seven is not overly detailed, but like many products that lose fine detail to ease and musicality, "you don't feel like stuff is missing."
Audition the KLH Model Seven if you're looking for a larger speaker from a manufacturer that is doing retro right. KLH holds onto no-nonsense classic good looks, and an acoustic design that relies on being direct and simple. You won't get as much bass extension as you would from a ported design, but you'll immediately understand that bass is always better and more realistic when it's tight and fast. Also, the slow roll-off of a sealed design means it integrates smoothly with subwoofers, letting you circumvent Hofmann's Iron Law by getting the speed of sealed box bass with the efficiency and extension of ported bass.