[SoundStage!]Fringe with Greg Smith
Back Issue Article
August 1999

ACI B-Flat In-Wall Speakers

Anybody can be forgiven for doing something stupid once. What distinguishes those of us who are really crazy is that we repeat our questionable acts regularly. Back in December, I wrote about my adventures destroying and restoring the walls in the condo I live in. The first half of that project involved running cables all over the living room to add distribution for audio, video, telephones, and computer networking. That was a nightmare involving power tools, heavy sheets of drywall to carry up the stairs, and white dust that hung around for months. After going through all that trouble, you'd have to be nuts to do it again. Which, of course, is exactly what my roommate and I did, only with an additional twist. Since the second half of the project involved wiring the bedrooms and bathrooms, where space is at a bit of a premium, we decided to add in-wall speakers to the mix. While the 11'x13.5' bedrooms could be made into decent listening rooms if that were their sole purpose, needing to house a bed, a desk, and bookshelves prohibits this. Installing the speakers in the walls nicely solves the floor-space issues.

In order to put in-walls in perspective, it's helpful to consider what you pay for when buying a standard floorstanding or bookshelf speaker. The concept I like to use is the bill of materials approach. When you manufacture something, the BOM is a listing of all the materials that make up a package you sell. The first thing most people would list if asked to construct a bill of materials for a set of speakers are the drivers. While those are expensive, it's quite common for the amount of money allocated for the speaker cabinet to dwarf what is spent on the tweeters and woofers, especially when the woodworking labor and other shop resources (e.g., glue or paint setting time/space) is factored in. The bill of materials includes lots of other things too. Don't forget to add in some cash for things like the manual you have to create and have printed. And your estimate will be wildly off if you don't consider packaging and shipping costs. To protect a speaker's expensive finish from a typical delivery by truck, manufacturers have to make some very expensive boxes. Some companies will only ship their speakers by carriers known to be more careful than a typical UPS delivery can manage to keep the speakers from getting damaged. While it sounds like a joke, it's actually true that on some really cheap speakers, like the crappy $20 ones you find at a regular mass-market store, the packing and shipping costs can exceed what the company spends on drivers.

Given the bill-of-materials perspective, where you realize speaker companies spend an enormous amount of their money is on the cabinet and its trimmings, and so you would think that in-wall speakers would get you much better value for your dollar. The enclosure becomes your walls, and all you're really paying for are the drivers, a crossover, some binding posts, and a (usually plastic) shell everything is mounted to. There's no expensive woodwork to get banged up in transit, which drops shipping costs considerably. In-walls should be a bargain compared with their more traditional speaker brethren.

Unfortunately, the market doesn't seem to work that way at the moment. When I went shopping for a set of in-wall speakers to install, I was very disappointed at what I found. The prices didn't seem much cheaper, if at all, than the standalone speakers of similar quality from the same company. The big cost savings I was expecting by not buying a full speaker cabinet just weren't there. I can hypothesize several possible explanations. It could be that the sales volume on the in-walls is so much lower that you're paying a premium because the manufacturing processes aren't as efficient. A cynic might suggest that there's more profit being made here, selling to the lucrative home-theater custom-install markets, than companies can make selling regular speakers. Whatever the reason, I feel that most in-wall speakers are wildly overpriced for what you're buying.

Since I needed 12 speakers to get 4-channel surround in each bedroom and stereo in the two bathrooms, it was looking quite expensive there for a bit. What saved me was looking through the website for Audio Concepts, the maker of the popular Titan subwoofer I reviewed two years ago. ACI sells their B-Flat Wallspeaker for a modest $139/pair. Each B-Flat includes a 1" dome tweeter and a 6.5" polypropylene woofer, not a bad deal for $70 per speaker. The rated bass response is -3dB at 60Hz and sensitivity is claimed to be 89dB/1W/1m, both of which are decent specs for the money. They also are designed to survive high-humidity environments, which means the bathroom installs should last a while. It takes a big leap of faith to order 12 speakers and cut holes in your walls to install them without hearing the speakers beforehand, but I didn't have a whole lot of other options. You can't just hang speaker drivers in free-space and expect to judge their sound quality, because a bare woofer without an enclosure loses most of its deep bass. If you're buying from a custom-installation dealer, they should have some samples of their speakers already mounted in walls for you to hear. That's one service that could well be worth the extra markup that seems to go with buying from the mainstream in-wall speaker market.

The other piece I had to arrange was speaker cable. My earlier install, in the living room where the speakers cost several kilobucks, used AudioQuest's excellent Type 4 cable. At $2.50/foot retail, it didn't cost too much for the rear-speaker runs. But in the bedrooms and bathrooms, there was about 400 feet of cable involved. It seemed a bit silly to buy $1000 worth of cable for $834 worth of speakers, so I looked for a less expensive alternative. I'm a big fan of solid-core copper cable without any individual section getting too large, so I limited my search to designs of that type. Unfortunately, most speaker cable aimed at in-wall installation is fat and stranded, both of which are big problems as far as I'm concerned. After looking around for a bit, I ended up back at AudioQuest again. Their Type 2 cable is similar to Type 4 in that it includes two pairs of solid copper wires inside each run. There are two main differences. First, the total conductor area is a bit smaller, equivalent to 17AWG instead of the Type 4's 15AWG. This is not a big deal for this application, where the typical runs are around 25' and the maximum recommended power to the ACI speakers is only 80W. The thinner wire unquestionably made installation a lot easier. The second difference is that the Type 2 is missing the soft filler material that cushions the conductors in the more expensive cable. Because of these differences, for any normal sized run I'd recommend getting the Type 4. But when you need a whole lot of cable and the sound quality doesn't have to be top-notch, the $1.50/foot Type 2 is a good deal. And while the filler makes Type 4 a bit of a potential fire hazard when run in a wall, Type 2's design is CL3 rated, which means you can safely install it in most areas and even hope to pass an inspection afterwards. I read up a bit on UL cable ratings at the excellent Low Voltage Home Pre-Wire Guide, a big collection of resources for the DIY cable installer.

When you're already running wires all over the place in your walls, installing the B-Flats as well is pretty easy. Knock out a hole using the template ACI provides, feed the speaker cable through, and attach it to the (yuck) spring-loaded terminals on the speakers. Fit the speaker in the hole and remove the grille, (I fit dental floss through the holes to yank the grille off) gaining access to a couple of screws. Turn the screws to rotate the "dog-ears" on the back, which hold the speaker in place. Pop the grille back on and you're done.

My bedroom install (as pictured in the opening to this article) has the speakers 7' apart from one another, about 5' above the floor. This puts the tweeter a bit higher than optimal when I'm sitting at my computer typing, but I couldn't mount the speakers any lower because they'd get in the way of the rest of my clutter. There are four speakers in the room, with the idea being that the room is ready for surround with a phantom center. We also ran an extra speaker cable back to the amplifier closet, which can be used to add a real center channel co-located with a video source in the future. Since the bedroom is small enough that the sweet spot is minimal no matter what, I'm not too concerned about getting the extra speaker at the moment.

Before the mess was even cleaned up, I fired up the 1987 version of the Alan Parson Project's Tales of Mystery and Imagination. [Polygram 832 820-2] The opening features Orson Welles speaking a passage written by Poe, and the B-Flats did a passable but hardly spectacular job of portraying a clear center image for that vocal track. The trouble really started when the second track, "The Raven," started with its very deep bass guitar. Each thump of the guitar was accompanies by a significant overhang. Touching the wall beneath the speakers, I could feel the vibration continuing after the note had stopped.

One of the reasons manufacturers of standard speakers spend so much time and money-building cabinets for their high-end designs is because it's universally recognized that an inert, solid enclosure improves everything about how a speaker sounds. If you compare something like B&W's Matrix enclosure to the rigidity of a normal home, with drywall and wooden studs every few feet, it's obvious which is going to resonate less when you play music with lots of bass. In days long past, people would build huge subwoofers out of spare rooms, attic spaces, and the like. This type of enclosure, referred to as an infinite baffle because the space is so big, isn't really in fashion anymore for a lot of good reasons. Nowadays, getting a dead-quiet cabinet with lots of internal bracing is essential to reproduce a high-end audio experience. Even though the bass response of the B-Flats is only rated down to 60Hz, that's still plenty of energy to vibrate the wall in time with the music. All that vibration overlays acoustic garbage over the music you're listening to. I shudder to think how awful the in-wall subwoofers I see some companies selling must sound.

Some companies go to considerable lengths to deal with these vibration problems. Phil Clements makes high-end in-wall speakers under the Solus name; they even have ribbon tweeters in them. When I asked him about vibration control, he gave me a long list of mounting options available for those models, and mentioned that he spends a lot of time talking with his dealers to make sure they’re aware of the issues involved. It’s also possible to just throw money at the problem. NEAR builds their approximately $700/pair CAL-8 in-wall speaker with a TeknaSonic vibration absorber mounted on the woofer. I’m tempted to do the same to the B-Flats as a future upgrade. Anyone who is installing in-wall speakers should be paying careful attention to getting a very secure mounting, preferably with some pieces attached to the wood studs instead of just gripping the drywall.

The last two months, the recording I've been listening to most is Subterranea [Giant Electric Pea GEPCD 1021], a concept album from British prog rockers IQ. While the decade isn't quite out yet, I feel safe stating that I think Subterranea will end up being the best progressive rock album released in the '90s. (The two-disc set goes for around $25 from prog import vendors like M&M music.) Unlike the band's earlier work, Subterranea features immaculate production and excellent mastering. During my initial fixation on the music, the two CDs were on nearly continuous repeat playing through the bedroom B-Flats for a couple of weeks. All of the instruments come through very well on the ACI speakers at normal listening levels, but the vocals are on the sibilant, spitty side of things. Tracks like "Failsafe" are recorded just on the border of being harsh, and the B-Flats accentuate that a bit. While not really obtrusive at lower volumes, start cranking things up and the sibilance gets objectionable. How loud is loud here? At my listening position, forming a 7' equilateral triangle with the speakers I have installed, I started to get uncomfortable with the sibilance at peaks of 88dB. A brief look at my Proton D1200 amplifier during this test suggested the speakers were using very little power, a bit more than 2W.

Associated Equipment
  • Rotel RCC-940AX CD changer
  • Rotel RSP-960AX preamp
  • Proton D1200 power amplifier
  • Parasound C/DC-1500 CD changer
  • AMC 3020 integrated amp
  • DH Labs BL-1 interconnects
  • JPS Ultraconductor interconnects
  • AudioQuest Type 4 speaker cable

Since it was unclear to me how much of this was related to the drivers and how much might be a vibration issue, I decided to cut down on the bass some. Audio Concepts sells high-pass filters for $39 that work at line level, inserted between your preamp and power amp. The models I have work at about 85Hz, but ACI also has some at 65Hz. Inserting the filters in my system did two things. First, the overall volume dropped around 1dB. It's not clear what percentage of that is related to the bass being masked and what is a straight loss, but I definitely felt the need to turn the volume up a bit to get an equivalent output even in the midrange with the filters installed. Second, the filters successfully blocked some of the deep bass and, correspondingly, the vibration. The biggest difference is in how the drum snaps sounded. The trailing edge of the drum's sound is much cleaner with the bass filtered out of the in-walls. Unfortunately, the sibilance is still a bit annoying.

Now that I'd taken some of the bass out anyway, it seemed a good time to drag the ACI Titan subwoofer into things. Tuning it to match the 85Hz roll-off, there was a big difference in how the subwoofer integrated when I flipped the 180-degree phase-shift switch. Having the sub out of phase worked a lot better in my room. Removing the filters and matching against the in-walls running full-range, I found about 65Hz and no phase shift worked well, which tracks well with ACI's claims for lower frequency response from the B-Flats.

Using the Titan was certainly as effective as extending the speakers to full range, either with or without the high-pass filters. One oddity of human hearing is that when the bass response of a system is full and deep, the treble sounds less pronounced. As a result, the B-Flats sounded smoother and more pleasant when the subwoofer was added, especially when in conjunction with the high-pass filter. If you want full-range sound, or you like volumes over 85dB, filtering the bass out of the B-Flats and using a separate subwoofer is definitely a path to explore. But I hesitate to talk too much about my results, because the constraints on where I could put the subwoofer meant I never got the kind of unobtrusive crossover I've normally achieved with the Titan. There weren't any useful spots I could find where I lost the ability to localize the subwoofer output. Note that this is a common problem when using crossover frequencies in the 80Hz range, which is why I usually prefer something below 50Hz instead.

Moving around the room, it's obvious that the B-Flats aren't engineered like most home speakers. The off-axis sound has considerably more energy than you normally find, which is good for filling up a room. The flip side is that when you're not aligned right, the sound gets even more ragged. When I'm listening at 45 or 60 degrees off-axis, the sibilance isn't quite as bad. But when I'm sitting at my computer, some measurements and a touch of trig tell me I'm 75 degrees away, and the treble output is ragged there. Normally speakers have their high-frequency content so reduced when you're that far from center they sound too laid-back. That is certainly not the case with the B-Flats.

How do the B-Flats compare with a high-quality regular speaker? I keep enjoying the $320/pair Clements 106di speakers I looked at back in June, and they have a similar driver complement to the ACI speakers. But the differences in sound between the two are quite obvious. The 106di’s tonal signature remains remarkably well balanced, even at volume levels exceeding 90dB, while the B-Flats suffer from dynamic compression, vibration-related bass bloat, and the sibilance I mentioned above as higher output levels. The quiet cabinet of the Clements speaker is simply a better environment for housing a woofer than my walls will ever be. Also, the 106di in my room reaches about 15Hz deeper in the bass, which makes it a lot more satisfying to listen to. If you want the best possible sound for your money, even at the $170 price of the B-Flats, I think the choice is obvious: buy a great regular speaker, not an in-wall. I’d certainly prefer something like Paradigm’s Atom ($180/pair) to the B-Flats, everything else being equal. But as I don’t have room for four Atoms in my room, that’s a moot point -- the B-Flats work here where regular speakers wouldn’t.

ACI’s B-Flat can be a satisfying musical source as long as you understand its limitations. When the volume here stays under 80dB, I rarely have a complaint about how the speakers sound. Running full-range, the speaker's bass is satisfying and the sibilance-inducing treble peak isn’t particularly fatiguing. But as the SPL creeps toward 85dB and above, I find the output somewhat too harsh for my tastes, and the vibration induced in the wall gets loud and distracting. While the first issue could be solved by using a speaker with more expensive drivers, the way the drywall shakes is going to be a limiting factor no matter how much I might spend on the speaker. If you’re shopping for in-wall speakers, make sure your installation is done with an eye toward reducing wall-borne vibration as much as possible, and avoid units that go deep into the bass. The inexpensive B-Flat works well for me, but there are definitely some trade-offs to consider carefully before you decide an in-wall speaker is what you want to commit to.

...Greg Smith

Audio Concepts, Inc. B-Flat Wallspeaker
Price: $139 USD per pair.
Warranty: Five years, replacement of defective parts.

901 S. 4th Street
La Crosse, WI 54601
Phone: (608) 784-4570
Fax: (608) 784-6367

E-mail: sales@audioc.com
Website: www.audioc.com

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