“Let our rigorous testing and reviews be your guidelines to A/V equipment – not marketing slogans”
Facebook Youtube Twitter instagram pinterest

B&W CM8 Floorstanding Loudspeaker Introduction

By

CM8_Gloss-Black.jpgB&W is one of the oldest and most respected speaker companies in the world. They have earned a well-deserved reputation for speakers that sound superb, feature innovative engineering, and utilize the highest quality materials for great cosmetics and fit-‘n-finish.

Designed in the UK and manufactured in China, the CM8 is a compact floorstander in their midrange CM family, just ahead of the 600 series, but beneath the 800 Diamond series. There are CM1 and CM5 bookshelf speakers, two CM Centres (love that British spelling!), two CM subwoofers and a CM9 floorstander above the CM8. At $1099 each, the CM8 certainly can’t be considered inexpensive, but just based on the quality of the materials and workmanship; they appear to more than justify their asking price.

At around 38” tall and only 6.5 “ wide with a very conventional rectangular cabinet shape, these speakers do not attract a lot of visual attention in the room. They’re quite innocuous and I doubt their visual presence would trigger the dreaded WAF to any significant degree.

Design Overview

The B&W CM8s were single boxed in heavy-duty corrugated and had high-quality EPS foam caps holding the speaker at each end of the carton. Chinese packing material is interesting: Regardless of the so-called “burst rating” printed on the corrugated carton or what kind of internal foam packing material they claim it is, in order to get the “good stuff,” a manufacturer has to pay a Chinese vendor top dollar. These cartons were burst rated at 300 lbs. Generally, Chinese cartons rated below 200 lbs. burst are made out of what manufacturers derisively call “cheese paper,” flimsy, lightweight material that seems ready to disintegrate under the slightest stress.

 1a 300 burst test carton.jpg

B&W CM8 Box Burst Rating Marking

Likewise, the internal foam packaging falls into two broad categories: 1) the cheap kind, that breaks into pieces and crumbles into tiny foam sawdust balls that float annoyingly all around the room, rendering impossible any thought of repacking with the foam inserts, and 2) the good foam, which stays together and makes repacking easy and repeatable.

B&W uses very high quality packaging. Having been involved in the design, sourcing and manufacturing of consumer electronics products for decades, I know the cost difference between good and bad materials, and what that says about what a given manufacturer thinks of their products and the image and impression they wish to convey to their customers.

This was a good first step.

The grilles were shipped in their own bag and the speakers themselves have a protective clear plastic shield placed over the baffle board to protect the delicate drivers during shipping and removal from the carton/initial setup. This is incredibly thoughtful and sensible packaging design. I have seen many a tweeter dome ruined by wandering fingers as the speaker was grabbed and carelessly pulled out of its box.

16 protector and bag on spkr.jpg

B&W CM8 Protector & Bag Covering Speaker

The speaker’s base (or “plinth,” as the Brits so amusingly call them) and the carpet spikes/rubber feet for hardwood floors sat in voids in one of the internal foam endcaps. The spikes/feet themselves were in a cardboard/plastic container, much like a small product you’d find at the store. Everything neat, everything nicely situated.

2 accessories in endcap.jpg

B&W CM8 Accessories

The plinth attached easily to the bottom of the speaker with the included machine bolts and hex wrench. Everything lined up correctly, and there was no paint of other obstruction to bind up the threads as the bolts were tightened.

There was another accessory that was unexpected: This was a two-part cylindrical foam “plug” that fit into the rear bass Flowport™. You can effectively transform the CM8 into a sealed system by using the entire plug, or you can remove the center section of the plug and get a quasi-combination of sealed and ported performance. The owner’s manual shows all three response curves: unplugged, partial plug, and fully plugged. More on how these sounded later.

 4 two-part foam plug.jpg

B&W CM8 Foam Port Plugs

The CM8 might be compact at 38” tall x 6.5” wide, but it’s very heavy for its size and conveys a very solid impression to the user. There are two sets of binding posts—just below the dimpled port, as part of a common plastic assembly— connected by a brass strap. The ends of the posts have the required plastic plugs (a CE requirement), but these can be pried out if you want to use banana plugs instead of bare wire to connect the speaker wire to the posts. The posts themselves have a nice-sized hole to accept bare wire and that’s how I connected them with 14-ga wire. Nice, easy, and secure. I did not use the bi-amp feature, but it’s nice to know the option exists.

 5 close-up holes in posts.jpg

B&W CM8 Binding Posts

The cabinet itself was made of high-quality 7/8” MDF. (Again, not all Chinese MDF is created equal—there is “good,” solid Chinese MDF and there is flaky, cheap Chinese MDF. This was the “good” kind.) The driver areas on the baffle were routed out, so those sections are thinner than the rest of the cabinet walls, unfortunately. However, as can be seen in the photos, the inside of the cabinet has extensive windowpane bracing, which contributes to the cabinet’s overall solidity. The FST™ midrange driver is in its own isolated chamber within the cabinet. The cabinet is also stuffed pretty densely with a fiberglass-ish material throughout, no doubt with the intent of reducing internal cabinet resonances and standing waves to a minimum. One gets the overall impression that this is a very inert cabinet that does not negatively intrude on the speaker’s sound.

6 windowpane bracing.jpg       7 cab bracing and stuffing.jpg

B&W CM8 Internal Views of Cabinet Bracing & Stuffing

This is a very attractive speaker with the grilles off. The silver “aluminum” rings around the woofer and the “aluminum” faceplate on the tweeter are actually just a thin (perhaps 2 mm thick) brushed aluminum flashing, adhered to a molded plastic substrate. This is pretty common practice among speaker manufacturers, as it gives them the opportunity to present nice-looking drivers that appear to have very expensive aluminum frames or faceplates, while keeping costs dramatically lower.

 8 MR trim ring.jpg

B&W CM8 Driver MR Trim Ring

In B&W’s case, however, these are, in fact, aluminum-frame woofer and midrange drivers. Once the trim rings are removed, you can see the raw drivers themselves: they have heavy cast aluminum frames, far stronger and less prone to ringing than cheaper stamped-steel frames.

 9 FST sideview.jpg

B&W CM8 Midrange Driver

The woofers have vented voice coils, and measure 29 mm across, or 1 1/8”. This is a beefy voice coil for a small 5” woofer. A slightly larger voice coil like this will exert more control over the woofer’s cone for lower distortion and will handle a good deal more power than a conventional 1” coil, which is 27% smaller than a 1 1/8” coil. Nice design.

Also clearly visible is the unexpectedly large magnet structure, which no doubt contributes to a respectable overall system sensitivity of 88 dB.

 10 CM8 wfr, vented VC, magnet.jpg

B&W CM8 Bass Driver (notice the vents on the voice coil)

One small nit to pick with B&W, however (and to be fair, they are certainly not alone in this): There is a sticker on the back of each woofer magnet that clearly says “8Ω.” Since the two woofers are driven in parallel, that means the woofer section is 4Ω. The midrange and tweeter also carry “4Ω” markings on the back. This is obviously, intentionally, a 4Ω system, in spite of the factory’s specs saying “8Ω.” Many other speaker companies stretch the truth about their impedances also, because most less-expensive receivers can’t handle speaker impedances below 8Ω, and to publicize a low system impedance (4Ω) is to limit the speaker’s acceptability in the customer’s mind. One would logically think that a speaker of the CM8’s quality will be teamed up with amplification that can handle an under-8Ω load, but B&W is certainly not alone in bending the ratings rules here.

 11 CM8 wfr with 8 ohm label.jpg

B&W CM8 Woofer Magnet

The distinctive yellow-woven B&W Kevlar 5” midrange driver features B&W’s proprietary FST™ design, which stands for Fixed Surround Transducer. According to the manufacturer, the FST design reduces the non-linearity in the driver’s travel by eliminating the overly soft and floppy conventional surround, thus keeping the driver’s motion more purely pistonic within its operational passband, for greater accuracy and lower distortion. The FST design is used in B&W’s speakers right up through their Diamond Series, which top out at over $20,000/pair!

The tweeter is an interesting driver. It utilizes a scaled-down version of B&W’s Nautilus tweeter rear enclosure, where the rear radiation of the tweeter is disseminated in a tapered chamber of non-parallel walls, thereby eliminating the possibility of the high frequencies being re-reflected through the dome and interfering with the tweeter’s direct radiation. As can be seen in the accompanying photo, the clear plastic tapered chamber is filled with damping material. There is no reason not to treat the high-frequency enclosure and radiator as an interdependent system, the same way the woofer and main enclosure are treated. Kudos to B&W for doing so.

12 tw Nautilus chamber.jpg 

B&W CM8 Tweeter

They could have done it even better in my opinion, however. Atlantic Technology in their $2500/pr AT-1 uses a 1 1/8” silk dome that is loaded into a bullet-shaped rear chamber. (See picture.) Since their enclosure also tapers into a non-perpendicular rear wall, there are no internal reflections that can come back up through the enclosure. However, the AT tweeter chamber is made out of drawn aluminum and functions as a very effective heatsink, since it physically contacts the tweeter’s back plate, forming a continuous thermal path with a massive surface area to pull heat out of the tweeter’s voice coil and magnet area. There is no reason that B&W couldn’t have done the same. As a matter of fact, there is no extra heatsinking on their tweeter at all and the rear chamber actually blocks some of the free air flow to the back of the small ceramic magnet and backplate, which is the part of the tweeter assembly that radiates the heat away from the driver. I’ll take on faith that B&W performed all the requisite power handling and life tests during development and that their tweeter is not prone to premature thermal failure. And in all fairness, the tweeter crossover is 4000 Hz, more than high enough to ensure that the tweeter doesn’t see any truly arduous current drive levels. Still at this price level, that rear chamber should have been aluminum, not clear plastic.

 13 Rear of AT-1 tweeter.jpg

Atlantic Technology AT-1 tweeter

The crossover is a pretty conventional design, using standard parts. It is mounted on the inside of the bi-amp terminal assembly, which is part of the terminal cup/Flowport™ plastic molding. Two massive chokes are used and mounted at 90º to each other, to cancel out any magnetic interaction between the two. That’s smart design. They are also both strapped and hot glued down to the PCB, for a good mechanical connection and vibration prevention. The caps and resistors are regular-grade components, not audiophile-fringe grade. The Flowport has B&W’s trademark dimpling on the surface of the port tube, said to reduce port “chuffing.” The inside end of the port tube is also flared to reduce wind noise, which is where many manufacturers cut corners since it’s not visible from the outside of the cabinet. Again, this shows the careful attention to detail one expects in a premium-level product.

 14 coils 90 degrees.jpg

B&W CM8 Crossover

The grilles continued the theme of clever, thoughtful design. Imbedded into the grille’s frame were several small neodymium magnets. Just under the surface of the speaker’s front baffle—but not visible to the user—were either metal discs or corresponding neo magnets. When the grille was brought near the baffle, the neos “grabbed onto” their magnetic partners under the baffle’s surface, and the grille neatly and precisely snugged into place on its own. A firm but gentle tug was all that was required to remove the grille, and there was never any danger of the grille coming off on its own. No alignment by the user was necessary; once the magnets “grabbed,” the grille positioned itself exactly where it was supposed to, every time. Very, very nicely done, and the front baffle of the speaker was totally free of any visual obstructions like grille tree receptacles or grommets, etc.

 15 neo mags in grille frame.jpg

B&W CM8 Grille Cover with Neo Magnets

My CM8 samples had what B&W called their Satin White finish. From the name “Satin White,” I was expecting a nice silvery-white finish, with a somewhat 3D depth and luster to it, similar to what premium automobile manufacturers use. Cadillac and Audi, in particular, offer a very beautiful white paint and I was looking forward to what B&W’s interpretation of this finish would be. Alas, I was a bit disappointed. The finish was a flat, plasticy white, akin to a white Formica countertop. While it wasn’t offensive per se, this was certainly the one area that my CM8’s came up short.

Set-Up

I set up and listened to the CM8’s in a 2-channel music system. The room was a small-to-medium sized 17 x 14 x 8 ft. These are very good sounding dimensions, since the length (17) is a prime number, and the height (8 ft) is not a whole number multiple of either the L or W. Therefore, these dimensions do not lend themselves to troublesome, additive bass/room resonances. The room has six 2 x 3 ft acoustic wall treatments staggered around the four walls (one centered on the front wall, two each at different heights on the side walls, and once centered on the rear wall between the two windows). There is a large sectional for seating and the floor is carpeted. Overall, the room is just slightly on the dead side of neutral, and it sounds excellent: solid, uniform bass, good imaging and detail, very little “ringing,” but live enough to let the speakers blossom out and fill the space with organic sound. Excellent recordings—especially of small-scale ensembles like jazz trio or solo piano—can sound almost live in this room. I have tremendous confidence that this room allows equipment to sound as good—or bad—as it can.

Associated Equipment

The rest of the system is simple but straightforward, and very high quality. The pre-amplifier/power amp combo was Parasound’s New Classic 2100 pre-amp and 2250 power amp, rated at 385 WPC 20-20k, into the 4Ω CM8’s. The CD player was the NAD 545 with Burr-Brown DACs. Considering the modest size of the listening room, this is more than enough clean, distortion-free power to ensure that the electronics never intruded upon the listening sessions in a negative way. Speaker wire was simple 14 ga. twisted-end, inserted into the holes in the binding posts. Basic Monster interconnects between the pre/power and the CD/pre. Nothing lunatic-fringe about the connectors and speaker wire, and more importantly, nothing that could even remotely be considered a defining or distracting influence on the sound.

The CM8s were set up according to B&W’s recommendations, about 2 feet from the wall behind them and about 2 ½-3 feet from the sidewalls. I experimented with placement by moving them closer to the wall behind them, but found that the balance got a little ‘tubby’ when the speakers were within about a foot of the wall. The speakers have very good horizontal dispersion and toe-in was minimal—perhaps 5-10º or so. Set up this way, the speakers threw a very solid, well-defined image with a good phantom center and relative immunity from stand-up/sit-down pickiness.

 

Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!

Recent Forum Posts:

ratso posts on August 04, 2012 08:48
nice review, and yes it is nice to see some of the bigger names being reviewed here. but… i hate to say this, because it could open a big nasty can of worms. but the next time can we omit the word “chinese” being used in a derogatory way here? you could have just told us “there is good mdf and bad mdf”, etc.
AcuDefTechGuy posts on August 03, 2012 10:44
Just more info:

CM8
Cartons = $54 each speaker
FST midrange = $123 each driver
Tweeter = $147 each driver
Woofers = $ 71 each driver
Plinth (body) = $117 each speaker
Crossovers = $163 each speaker
Grilles = $100 each speaker

And yes, very nice to see more reviews of the big brands.
Nuance AH posts on August 03, 2012 08:54
No measurements?
templemaners posts on August 02, 2012 14:30
I tried 2 different browsers and 2 different computers, but didn't see the jump to bar on the Intro page, but it showed up on the listening and conclusion pages Matt put up.

Thanks for the links.

Side note on the actual speakers - the press photos make them look a lot wider than 6.5".
gene posts on August 02, 2012 14:26
templemaners, post: 898390
I don't see anything of the review past the introduction page.

anytime we change the publish date and post, it takes an hour or so for the page to cache out and show the other pages. It should appear, soon.
Post Reply