Polk 7Bs: Excellent Large Bookshelf Speakers from the Late 1970s
Nov 15, 2012 (Updated Jan 17, 2013)
a Very Helpful Review
by the Epinions community
Polk 7Bs were one of several versions of the famous Polk 7, a high quality loudspeaker that was introduced by Polk Audio in the late 1970s and continued in production at least into the mid-1980s. The 7Bs are two-way loudspeakers featuring a 6 ½” bass/midrange driver, a small dome tweeter, and a 10” passive radiator. I believe that the tweeter for the Polk 7B may have been made by Peerless, an excellent driver manufacturer. The bass/midrange driver is the same one used in many Polk speakers of the time, including the 10B.
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The Polk 7B is a fairly large bookshelf style speaker, measuring 24” x 14” x 9 1/8” deep. Recessed into the back are banana plug connectors, similar to those used on Dynaco A-25s. They twist in and out, so you can choose to use banana plugs or standard speaker wire to hook up your speakers. A nice touch with the 7Bs is that there is a fuse to protect the drivers, and that fuse is mounted outside the speakers, in the recessed back area next to the terminals. This means that you can easily replace the fuse should a power surge or teenager do something undesirable. Your drivers will still be intact once the fuse is replaced.
Aesthetics and Actual Use.
The most obvious negative about these speakers is that they are finished in faux-walnut vinyl, not real wood veneer. But the vinyl isn’t too fake looking (it’s quite dark) and will suffice if it hasn’t been damaged (you can’t really “refinish” faux-walnut like you can real wood). The grill cloths are black fabric.
Someone recently brought a pair of Polk 7Bs to me for some corner restoration work, and of course I had to give them a listen. The Polk 7Bs are slightly more sensitive/efficient than my vintage reference Dynaco A-25s loudspeakers. I believe both are rated at 89db/1 watt/1 meter, but the Polks sounded subjectively louder than the Dynacos when I switched them in. I’d guesstimate them to be about 1 to 1.5 db more sensitive. The sound of the Polk 7s was smooth and well-balanced from the start, and I continued to enjoy listening to them over time. They were not fatiguing, nor did I notice any bothersome colorations.
The overall tonal balance was fairly similar to that of the Dynaco A-25s; these are definitely “East Coast” (slightly mellow-balanced) speakers. But there were differences as well. The Polk 7Bs sound like they had a bit more treble extension than the Dynacos, and (surprisingly, given the size of their front baffle) I also thought they threw a better defined soundstage. The Dynacos sounded a bit more mellow, and also placed instruments a bit further back in the soundstage. On classical piano (KDFC), I did notice an occasional high note “thrust forward” a bit with the Polk 7Bs, but this was very rare. Overall they did a great job with classical piano and accompanying orchestra.
On jazz music (Keith Jarrett Trio), the Polk 7B sounded neutral, with the piano a bit further forward in the soundstage than with the Dynacos. Cymbals were airy and relaxed. A quick switch to the Dynacos confirmed that their tonal balance is similar overall. The Dynacos actually presented the “growl” of Gary Peacock’s bass with a bit more authority, while the Polks made the cymbals in Jack DeJohnette’s drum kit sound just a touch more natural. The Polks threw a slightly larger soundstage and were slightly "crisper" and “cleaner” sounding.
On folkie Greg Brown’s Covenant CD, just a touch of the heft of Greg Brown’s voice was lost with the Polks, relative to the Dynacos, but the sound was still good overall. Accompanying acoustic guitar sounded similar to the Dynacos, with perhaps a tough more air, while electric guitar had a bit more “edge” to it with the Polks. Voice clarity was really good with the Polks.
One unusual area where the Polk 7Bs were among the best speakers I’ve auditioned here: male radio announcers’ voices. Large Advents and Acoustic Research AR-3as make male radio announcers sound a bit too chesty. Dynaco A-25s make them sound a bit warm, though less chesty than the Advents and ARs. Through the Polk 7Bs, they just sounded like real people talking in a fairly large acoustic space.
A couple of times I was listening and writing, I was marveling at how dynamic these speakers are, or how natural the cymbals are on the Keith Jarrett CD, only to realize that I’d switched to the Dynacos and was listening to them at the time. The point is one that audiophiles sometimes write about: you quickly adjust to the tonal balance of any good loudspeaker, and subtle differences sometimes don’t make that much difference in overall listening pleasure. As I was half way through writing the previous sentence, I switched back from the Dynacos to the Polks, and yep, everything I wrote above is true (cymbals a bit more airy; a little upper bass growl lost; soundstage a bit more forward, etc.), but I’m already adjusting to the Polks’ presentation of the music.
The Polk 7B is yet another excellent loudspeaker from the 1970s. As I think about the many really good vintage speakers I’ve reviewed, I find myself wondering what the Polk 7Bs would sound like in an A-B comparison with the recently reviewed A/D/S L-730s (which have since gone back to their owner). Both had unusually clean trebles, and yet neither sounded particularly bright.
Compared to my reference Dynaco A-25s, the Polk 7Bs were a tad cleaner, a tad less full in the upper bass, and a bit more forward in their presentation. If I had to split hairs, I’d say the Dynacos were a bit less fatiguing over hours of listening, while the Polks were a tad more exciting to listen to.
I do wish that Polk Audio had made some of their speakers with real wood veneer. It adds just a touch of class to the speakers (and makes things more fun for me, as I can refinish the things to near mint). But the faux-veneer of the Polks is dark and unobtrusive, and the front grilles are also attractive and understated.
One more positive that I haven't mentioned: Like Dynaco A-25s, the Polk 7Bs have rubber woofer surrounds, rather than the foam of Advents and several other '70s manufacturers (including Acoustic Research on some of their models). Rubber surrounds last for generations, meaning that you should naver have to "refoam" a pair of Polk 7Bs.
Put these on your short list if you’re looking for some vintage “East Coast” speakers with a high degree of clarity and just a touch more “excitement” than provided by Dynaco A-25s, AR-2axs or Large Advents.
Thanks to wsmunch for getting Polk 7Bs listed on the Epinions website!
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