Publisher Profile

Bowers & Wilkins CM-7 Floorstanding Speaker Review

By: |


I suspected that the result of the FST mid and the sealed tweeter enclosure would mean a speaker with less sensitivity, but I was not prepared for just how low it would be. The manual pegs the sensitivity of the CM7 at a fairly low 88dB. This is pushing towards the low end of the sensitivity scale, where the scale runs from about 101+ on the top-end and to 80 on the abysmal-end. The Eminent Technology LFT-8B at 83dB takes a lot of juice to sing loudly! At 88dB the CM7 is down lower to the Magnepan 1.6’s at 88dB than many dynamic speakers. Though the variance in numbers seems small, the effect is pronounced; the Von Schweikert VR-4 SR MKII at 92dB, on the other hand, is easy to drive.

Consider this; with each 3dB increase in sensitivity in a speaker, the amplifier needs only half the power to produce a given volume! It also works in reverse, as a 3dB decrease in sensitivity calls for a doubling of power to reach the same volume! Consequently, with inadequate power the CM7’s may not live up to their potential. I can certainly see an audiophile scratching his head in wonderment as he arrives home and hears the B&W’s hooked up to his surround receiver, “Why don’t they sound ‘gripping’ like they did on the big system at the HiFi shop?” Indeed, he has answered his own question when he chose the word “big,” as in big power. I suggest B&W owners with lower-sensitivity speakers investigate their amplification and see if they’re starving their speakers for power. If the sound has not been satisfactory, that may be the primary reason.

When I proposed to Mike that the CM7’s might be low in sensitivity, his response was, “We wouldn’t necessarily consider 88dB particularly low. Like all passive speakers, we are bound by the relationship between box size, efficiency and bandwidth (i.e. bass extension). If we wanted higher efficiency, either the box would have to grow or we’d get less bass. The one advantage in sacrificing efficiency is that, to some extent, you can recover the maximum sound level by making the speaker handle more power.” It is a very good thing, then, that B&W did not lower the sensitivity further, since the speaker is rated at 62 Hz +/- 2dB on the low end.

If your old speakers were higher sensitivity and you move to the B&W’s, you may feel you’re “missing something,” because you have to crank up the volume more. If so, it’s time to investigate a new power source. Once done, these speakers will wake up nicely. I heard this effect precisely transitioning from those sweet little numbers, the Monarchy Audio SM-70 Pro mono blocks, to the twin Pathos Classic One MkII integrateds bridged at 170 wpc (270wpc at 8 ohms!). An individual might think that a smaller floor standing speaker should not need that much power, but if you have a concern beyond HT applications that you desire the best you can get out of them, the CM7’s demand at least 75 Watts of solid power, and ideally 100 Watts or more. You are not likely to get that out of a mass-market HT receiver.


“ … the FST mid is one of the most tonally correct drivers I have heard in a speaker in this price category.”

After laboriously scrutinizing the sensitivity, potential suitors will be happy to know that the FST mid is one of the most tonally correct drivers I have heard in a speaker in this price category. Granting less weight from the smaller cabinet and limited low end, voices were reproduced with uncanny subtlety. Combine this with excellent detail and the CM7 rings true. The speaker is not prodigious in scale, but one gets the distinct sense that the sonic signature could be laid down upon a larger speaker’s voice (in the way that tracks are laid down in recording) and not be in error.


B&W kindly supplied me with a demo disc entitled Bowers & Wilkins with Real World Records. One track in particular I kept playing over and over, “Old Blind Barnabus,” sung by the Blind Boys of Alabama, in reference to the Biblical account of a blind beggar calling out to Jesus to heal him (Technical correction: the name of the beggar was Bartimaeus (see Mark 10:46-52 in the Bible. Barnabas was a fellow missionary with Paul, the Apostle. I do not know if the Blind Boys used artistic license, or simply erred). It was genuinely thrilling to hear these jowel-cheecked baritones and basses singing with abandon. The snap of fingers keeping cadence with the piano and chorus was mesmerizing. The clarity of the voices through the FST was commendable. There was a trim, but not restricted, nature to the FST which inspires confidence that one is hearing a tight presentation.

Boz Scaggs has always been one of my favorite “curiosity” artists. I say curiosity because certain performers have unique voices or playing styles. Boz’s voice is constrained-sounding in such a way that I recall a friend of my mother who had vocal chord surgery. Her voice was affected permanently, and she could only muster a strong whisper in conversation. No matter the intensity of the comment, it came out as a strong whisper. Almost anything she said was interesting because it sounded stressed but soft. I find that I listen to Boz’s voice in the same way, enjoying hearing such a unique sounding set of vocal chords. As he is aging, he’s moving toward ballads rather than pop songs. His collection entitled My Time: A Boz Scaggs Anthology reveals a terrific amount of ennui in his voice as a dejected lover in “Just Go,” and a longing for solitude in “Sierra.” One feels his pain and tiredness intensely – much of this I chalk up to the FST mid, a very clean midrange driver.

It seems, however, that the CM7 was bred to rock, and this it does quite well. I was messing with the Tannoy Glenair’s (in for review), seeing what they did with older bands like Boston (Horrors! Such a fine high efficiency speaker as a Tannoy and such crass music as Boston? Oh, yeah!) when I was struck by the urge to compare the sound with the CM7. One can hardly get two more distinct speakers than these, the one having a concentric 15” paper woofer with horn tweeter, the other the tight, 3-way Kevlar-wielding CM7! It is not proper to simply compare the two speakers in a win/lose fashion as they are separated by more than $8k retail. What I was looking for was how vibrant the CM7 was with the rock music.

“There have been larger floor standers where I have had to limit levels so that they would not assault the ear, but not these.”

The CM7’s like to party, eschewing the polite, refined nature of the Glenair. They bit into the meat of the music and punched their way through the bass line. I wondered if I would be able to tolerate the guitars at high levels on tracks like “Foreplay/Long Time”, and pleasantly I was able to. There have been larger floor standers where I have had to limit levels so that they would not assault the ear, but not these. Even though the bass driver was pushed beyond comfortable level to begin a “pumm, pumm” rhythm, and the synth was a tad stressed, they never broke my self-imposed “noise” barrier – the point at which the music sounds like noise rather than music. This is high praise for a smaller floor stander!

Music through the CM7’s seemed contextualized properly. I had just picked up Seal’s Live in Paris DVD, and put it on the Oppo 970HD going through the Pathos amps. It was perfectly grand, the 7’s in a darkened room at full stride presenting themselves as though they could be much larger. The vibrancy matched the intensity of the on-screen performance. I never gave a thought to the fact that my subwoofers had been silenced.


The Story Of The Foam Plugs

In the tradition of the TV shopping channel QVC, “BUT WAIT! THERE’S MORE!” (Queue image of CM7’s in background with set of foam plugs foreground…), for an unlimited time, when you purchase a pair of CM7’s, we’ll include free this set of audiophile quality foam bass port bungs! Made especially for B&W, they are guaranteed to combat bass bloat!” If I were selling CM7’s in a store, I would play up these least expensive, most easily ignored elements of the speaker – the very low-tech foam port plugs! I have to laugh at the technical term employed – “bung.” I guess the word plug is not accurate and cylinder is not fancy enough.

I do not speak in jest about the efficacy and necessity of these little foam wonders. I found that the bung was quite useful to integrate the speaker’s presentation. It took a bit of looking in the manual, but I did find the reference under the heading “Fine Tuning”:

“If you want to reduce the volume of the bass without moving the speakers further from the wall, fit the foam plugs in the port tubes as illustrated in figure 3.”

That was it; what it should have said was, “The foam plugs supplied are the means to obtaining superior performance from your speaker.” I don’t expect B&W to admit it, but the foam bungs were as critical as any other aspect of this speaker’s performance!

Granted, foam bungs are not the kind of things I typically get excited about, but what was exciting to me was the impact these silly foam pieces had on the speakers! Sometimes audio is an experiment in centimeters, either in placement of speakers or a sound panel, etc. My logic was that a foam plug would effectively attenuate the bass as it was inserted in varying depths into the port. It worked marvelously well! I felt the speaker was bass emphasized without the plug. I experimented with two primary options: 1. No Plug, resulting in an earnest bass with unacceptable distortion at higher levels, or 2. Plug inserted fully, resulting in a more subdued bass, but with more emphasis on the treble making it a tad too stiff.

“The happy news is that the CM7, to a degree, can be tuned to taste.”

The solution was to pull the foam insert out approximately two thirds. Ahhhh! The integration of drivers was complete! (Sounds like a mad scientist, “We have achieved the integration of the drivers! It Lives! It LIVES!”) The bass was meaty but not meandering and the treble was complimentary to it. Now I could bob my head and relax as I increased listening levels. While this may seem absurd to some readers, such precise positioning of the plug had important consequences in my room. The happy news is that the CM7, to a degree, can be tuned to taste. It took some fiddling with the plug to get there, but once the Goldilocks setting was reached, the sound was just right!

When I mention such a seemingly unintuitive tweak, it is only because it made a significant contribution to the overall sound. If the foam bung didn’t make that much difference, I would have conceded that one had to live with a bass or treble emphasis in the CM7’s. No, the plug position did not make the speaker suddenly take on different tonality or make it jump into a higher echelon of speakers, but it did make it perform much more like a well balanced speaker.

That is also the conclusion I reached regarding the CM7 – that it is a vivid sounding, yet well balanced speaker. It’s notoriously difficult to make a small floor stander with satisfying bass, and it’s not an easy thing to make a monitor with an appealing upper-end. B&W has done well on this account as they have made the CM7 a superb-sounding Compact Monitor for use as mains, especially so in a HT oriented system.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Popups Powered By :