When I decided to install a home theater system, I opted for in-wall and in-ceiling speakers. There are many advantages to using in-wall speakers for a surround sound system, including a clean, nearly invisible aesthetic for both the speakers and the wires and the ability to perfectly place the speakers (with bookshelf or floorstanding models, it can sometimes be hard to place the center, left, and right channels at ear height). You can often paint the grilles to match your walls and ceiling...even cover them with wallpaper (after you perforate the paper, of course). In-walls can also be the safer choice--pets and children (even curious or clumsy adults) can see a floorstanding or bookshelf speaker as a plaything.

The in-wall speaker I chose for my front left, center, and right channels is the Definitive Technology DI 5.5LCR ($449 each), which is part of the company's Disappearing In-Wall Series. The DI 5.5LCR's flangeless grille is magnetic, and its slim profile barely casts a shadow. The micro-perf grilles are paintable. These certainly fall into the nearly invisible category and present a great aesthetic that's sure to please the pickiest of those who firmly believe speakers should be heard and not seen. The supplied cutout template makes it easy to install the speaker between studs either horizontally (for the center channel) or vertically (typical for the left and right channels).

The DI 5.5LCR uses dual 5.25-inch woofers, and Definitive Technology also offers the DI 6.5LCR that uses two 6.5-inch woofers. The tweeters are the same: a one-inch pure aluminum dome. The DI 6.5LCR will not fit between standard studs horizontally (there are ways around this, but it's not easy!), which is why I chose the DI 5.LCRs instead. I found that using the same speakers for all three tasks (L/C/R) makes for a perfect sonic match, although there is no reason you couldn't use the 5.5 for the center channel and 6.5s for the left and right (when oriented vertically, they fit easily between standard wall studs).

The speaker has a three-position environmental EQ switch on the front for tailoring the speaker response to the type of room in which it will be used. If your listening room has reflective properties (hard floors, smooth ceiling and walls, and/or non-cushioned furniture), the sound will be overly bright and unnatural. Engaging the environmental EQ by selecting the "-" setting compensates for overly accentuated treble. If your room has a lot of absorbing surfaces such as drapes, rugs, and thickly upholstered furniture, the speakers may sound dull. Engaging the "+" setting will boost the treble and compensate for this. Leave the switch in the center position in rooms with a balance of reflecting and absorbing surfaces. I chose this setting, as I have plenty of options elsewhere in the signal path to make fine EQ adjustments if needed.

These DI Series in-walls have pivoting tweeters that can be aimed by simply pushing gently near the edge of the tweeter assembly, which allows for approximately 15 degrees of point-source axis adjustment.

So, how do they sound? In a word: terrific. When listening to music (I use my receiver's All Stereo setting), the Definitive Technology speakers are clear and airy. The high frequencies seem to extend and open up effortlessly without ever getting harsh, with plenty of detailed midrange that never gets muddy--thanks, in part, to off-loading the low-frequency chores to a subwoofer (my 14-year-old Miller & Kreisel 12-incher). If you're in the market for a matching in-wall subwoofer, Definitive Technology makes two models: the IW Sub Reference (shown right, $1,299) and the IWSub 10/10. These are passive subs, so Def Tech makes the SubAmp 600 ($699), which would be tabletop- or rack-mounted with your other gear. Either of these fully enclosed subs would be a great way to have your entire speaker system nearly invisible and flush with your walls and ceiling. I only heard these subs once in a showroom, but that was enough to convince me that, if a zero-floor-space footprint is among your design goals, either of these would be a great choice.

I have my M&K sub starting at their upper range at 120 Hz, and the DI 5.5LCRs starting at their lower range at 100 Hz. Just right for my ears. With movies, TV shows, and video games, dialogue from the DI 5.5LCR was perfectly intelligible, while the highly localized left and right information comes seamlessly from a very nicely framed soundfield. I use a set of DAS Factor 5s for my left and right surround speakers because I already owned them, and they work quite well. Had I not already owned those, I would have selected the Definitive Technology DI 5.5BPS ($449 each), a bipolar surround speaker that provides extremely wide dispersion. I've heard these, and they are terrific. The pivoting pure aluminum tweeters and axially aligned design allow for greater placement freedom whether using them as side or rear surrounds or both. This is where Def Tech gets its Balanced Dual Surround System moniker from, as these speakers employ dual 5.25-inch woofers along with dual tweeters (the same one-inch pure aluminum tweeters found in all the Def Tech in-wall and in-ceiling speakers in this review).

Did I mention I have a Dolby Atmos setup with an Onkyo TX-NR636 receiver? For my height channels, I'm using another Definitive Technology in-wall: the DI 6.5R (shown right, $279 each), which is a direct-radiating, two-way speaker with--you guessed it--a 6.5-inch woofer and one-inch tweeter. Not only do the speakers seamlessly deliver the height information for Dolby Atmos, but they sound full and detailed in All Channel Stereo when I play music through the system.

High Points
• The DI 5.5LCR is nearly invisible. For the slightly higher cost of installation, you get a clean look with no visible wires and nothing to have knocked over.
• These in-wall speakers deliver great sound.
• The speaker is a great value, since the speaker manufacturer does not have to provide an exotic wood or high-gloss finish.

Low Points
• Installation often requires cutting through walls and snaking wires through studs, which can be costly.
• These in-wall and in-ceiling speakers are not enclosed, so sound may leak into adjacent rooms.
• In-wall subwoofers, even the fully enclosed subs from Definitive Technology, struggle a bit to provide chair-shaking, chest-thumping LFE compared with freestanding subs.

Comparison & Competition
The list of possible competitors to the DI 5.5LCR is long. One good option that comes to mind is Noble Fidelity's L-85 Mk II ($895/pair), which is suitable for use as both an in-wall and in-ceiling speaker for the L/C/R and height applications. Using one model for all chores could be seen as a negative--you know the saying, "jack of all trades, master of none." However, Noble Fidelity has engineered a system that handles the differences between dialogue and effects extremely well. The design adopts the same nearly invisible goal as Definitive Technology's DI Series, and it includes micro-perf beveled magnetic grilles in both round and rectangular shapes to suit in-wall or in-ceiling mounting. They are pretty slick.

If you fear that sound will leak into an adjacent room from standard in-wall or in-ceiling speakers, you'll want to consider a fully enclosed option. Enter Sonance, whose solutions all have integrated enclosures. This not only keeps the sound projecting in the intended direction, but it allow Sonance to tune the speakers more precisely. That adds another level the price, however. More drivers, more tweaking potential and more, well, everything. These speakers start at $1,250 each, and I recommend you listen and decide if the price matches your wants and needs. Are they better? Yeah, but how much better is something you need to decide for yourself. If isolation is a requirement, I wouldn't hesitate to go with these speakers.

Conclusion
If you're building an home theater system from scratch (even in an existing, older room) and a nearly invisible, zero-floor-space design is your goal--but you don't want to sacrifice sound quality and aural impact--I highly recommend the DI Series from Definitive Technology. The speakers' build quality and attention to detail (both visually and sonically) are excellent. We are talking about way more than bang for the buck here, although the value is extremely high. Using all the Definitive Technology speakers I discussed here, along with the IW Reference subs and the SubAmp 600, a full-tilt bozo 9.2.2 Dolby Atmos disappearing in-wall and in-ceiling speaker system would cost a total of $7,556. Add a good Dolby Atmos-enabled receiver, and you're rockin' a system that would have cost significantly more money just 18 months ago! Cue up Donald Fagen's "Tomorrow's Girls" or pop in Mad Max: Fury Road on Ultra HD Blu-ray with its Dolby Atmos soundtrack, and prepare to be wowed. I was!

Additional Resources
• Check out our In-wall and On-wall Speakers category page to read similar reviews.
• Definitive Technology Debuts BP9000 Bipolar Speaker Line at HomeTheaterReview.com.