KEF Custom Install THX Speaker Review

• Review Summary
• Review Specs

One of the most exciting things about buying a house this past year was the opportunity it presented me for my home theater. After years of having rooms that I had to leave undamaged in rental houses, I could do anything I wanted. One of the first things I did was to decide to go with in-wall speakers to open up more space in the room. Because of my love of their UniQ sound I went with the KEF THX in-wall system and over the past few months it has proven to be fantastic. The KEF system is dynamic and detailed, offering huge performance while becoming almost invisible in the room.

An Invisible System

One of my main goals with my updated home theater was to make as much of the system invisible as possible. By invisible I mean that it is out of the way, with no wires or anything else that I can see, so that I can have as much room as possible for equipment that I am testing. As important as it is to keep my space clean, the gear also had to perform up to the level that I needed for testing other AV components. If the in-wall speakers don’t sound good, I can’t use them to test receivers or turntables with.

Usually if I was considering buying a speaker setup, I would try to review it first so I could make sure it lived up to the standards I wanted. With in-wall speakers this isn’t an option, unless you enjoy installing new drywall after you test a pair out. You can go to dealers to hear, if they have them installed, but there is almost no way to hear them in your room. I’d heard the KEFs at CEDIA before, so I wasn’t blind, but they are similar to my existing R300 bookshelf speakers. Until they showed up at the door, I hadn’t given any of them a full listening session, though.

In the end I decided on a 5.x.4 system with the KEF Ci5160RL-THX Fronts, Ci3160RL-THX Center, and using the Ci200RR-THX for Left and Right surrounds and 4x Atmos/DTS:X height channels. I didn’t go with rears at the start, but left open the option to add them later in the home theater if I felt I needed them. Unfortunately for me, arriving at my house was the beginning of the process.

Reference Design

The KEF system I decided to go with is built to offer the same performance as a conventional speaker system, only without the conventional box. The Ci5160RL-THX fronts each feature a UniQ driver made up of a 6.5” midrange driver with the 1” tweeter in the center. Four 6.5” bass drivers pair with this to offer bass response, even when open backed, close to their R700 tower speaker. At 42 lbs each, without a cabinet, these are beefy speakers with a metal front to keep the drivers rigid when placed in the wall.

The matching Ci3160RL-THX speaker only has two bass drivers instead of four, but otherwise remains almost identical. Since I plan to use it only in a home theater application, I don’t need quite as much bass response in the center channel, but do want the extra bass for when I run the fronts full range for vinyl and other music listening. The UniQ driver here provides ideal integration between the tweeter and midrange for vocals, letting them all originate from a single point. It also offers fantastic horizontal and vertical dispersion, making the sweet spot on the couch for movies wide enough for anyone that is watching.

The Ci200RR-THX UniQ driver pairs a 1.5” tweeter inside an 8” woofer. These are ideal for in-ceiling or surround use, with frequency response that dips down to 33Hz while still maintaining the single point-source design of the UniQ. A set of four arms swing into place and lock the speaker against the wall, making for an easy install with a screwdriver. All these models also feature magnetic grills that you can paint to match the walls, though you’ll want to be careful to use a sprayer to prevent the grill from clogging. I chose to leave them unpainted for now, but might go back and change that later on.

If you’re familiar with the KEF R-Series, the Ci R-Series will look familiar as it is the same technology, adapted for a custom install situation. The main reason I went with the KEF system is still the UniQ driver. By placing the tweeter inside of the midrange driver it unifies the location those sounds come from, hence UniQ. While this might seem like a small thing, after all most speaker designs don’t use it, in practice I found it to be a big difference. There were no small timing differences between sounds from the tweeter and midrange, offering better clarity and detail on everything I listen to. Every seat becomes a better seat, as they’re all the same difference from both drivers while with a conventional speaker those distances can change. After listening to KEF speaker compared to many other speakers for a bookshelf speaker guide at Wirecutter, I was a convert.

A Truly Custom Custom-Install

My theater room is compact at 11’x13’ with 8’ ceilings. One thing you can notice is the exposed beams at the top of the ceiling. These look nice and work great for hiding my projection screen in, but for in-ceiling speakers they present a problem: there is no ceiling! Above the beams is the sub-floor for the master bedroom, so I can’t drill any holes in there. I was going to have to build custom enclosures to hold the Atmos channels in-between the ceiling beams.

While running cables for the room, I measured the walls where the surround speakers are going to go. The wall are your standard 2×4 stud construction, which means they have around 3.75” of depth inside of them. The KEF Ci200RR-THX is a beefy 8” driver with a powerful magnet assembly, and it needs almost 5” of depth. Now the surrounds are going to need their own custom enclosures as well.

The center channel is designed to go across studs if you can notch them, but for me that meant notching an outdoor wall. This was something I did not want to do, and so I decided to build an on-wall box for the center channel as well. The left and right speakers looked to be able to fit into the stud bays fine on the front walls, so they would not need to have any custom boxes built for them.

I’m also very thankful that my father-in-law enjoys building things, as he already owned all the power tools I needed. KEF provides minimum and recommended volume sizes for cabinets if you decide to build them for their custom install speakers, so I used those as my template for size. I decided to not skimp on the cabinet construction and went with plans that people would use for building a subwoofer cabinet. If it can hold a 12” bass driver without much vibration, it can hold these. I sat down and designed cabinets for each speaker that could be made from a single 2’x4’ sheet of 3/4” thick MDF. Since I’m not a woodworker, I tried to make the cabinets as simple as possible, with the fewest cuts, so it would be easier to get right. You can see the plans that I used for these below.

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Once cut, all the cabinets with assembled with Gorilla Wood Glue and Spax MDF screws. I can’t say enough good things about the Spax MDF screws. With the Torx head and the tip design, you can drive these in without needing to pre-drill at all. They go in fast, they hold tight, and they led to assembling cabinets that were rock solid. To be 100% sure that these cabinets were sealed, we left off the front panel until the glue had dried. Then I added some smaller 1×2” pieces of wood to the walls to pull them even tighter and caulked all the seams inside. After this was finished then I put the front panels on and glued them tight.

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After another day of letting the glue dry, I was ready to drill out the holes for the speakers. KEF provides a template for installing the speakers on the walls, which of course works for doing it this way as well. With a jigsaw and going slow and steady, doing this was not hard at all. Once finished I took the MDF out, vacuumed out the dust from inside the cabinets, and was ready to paint. Since I had my home theater room painted when I moved into the house, all in a neutral gray for video reasons, I had leftover paint to use here. I only bothered painting the sides that would be exposed to the room, no need to deal with painting what only the walls will see.

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Finally we were ready to finish up the final bits of the speaker cabinets. I drilled a pair of holes in each and installed some binding posts from Parts Express on each. Some polyfill was installed into each cabinet making to improve bass response as well. Installing these cabinets into the ceiling was actually pretty easy, aside from the weight. Each speaker box is close to 35 lbs from the MDF alone, making them a bit hard to hold up and drill at once. Again here I used screws from Spax to attach them to the ceiling beams and they worked perfectly. The boxes fit right between the beams and with six screws each, they aren’t going anywhere. Surrounds were anchored into a horizontal stud on each side by screwing inside of the cabinet, and the center channel was mounted below the TV to studs. I then ran 12 gauge wire from the closet to each box and was ready to install the drivers.

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Finally it was time to install the front left and right speakers, which are much easier. They have a brace that is designed to slip around the drywall and then it is tightened around it. This sandwich then keeps the speaker in place and uses the wall cavity as a speaker box . For most installs this is pretty easy to do, aside from the little bit of stress from making a gigantic 4’ tall hole in your drywall. Once the hole for the right speaker was cut, I then found a problem: the studs were too close together.

Yes, when I measured the studs I was sure I had enough room, but I managed to measure the outside edges of them, and now I had a problem. They were an inch too close, so I couldn’t slide the speaker in around the drywall since the studs got in the way. The hole was in theory large enough, but I was stuck about how to get it in there. After trying to figure this out on my own for a few hours, I called KEF and gave them the situation. We thought about it for a while, and I kept thinking of solutions. Maybe I could build a small box outside the wall that it rests on? Could I file away at the drywall on top of the studs enough to slip it in?

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An hour later, KEF called back with a solution, and an ingenious one. We would get a 1”x3” strip, cut it down, and attach it inside the wall, connected to the studs. Then I would remove the back half of the brace, which usually allows the speaker to compress against the drywall. By attaching those strips inside the wall, I could use the 10 screw holes usually used to connect the back brace to instead screw the speaker to those strips. Now the speaker would be connected to the studs, making it rigid, and able to fit into the hole I’d already cut. Amazingly, this worked. The speaker fit right into the wall, it attached to the trim strips, and it compressed against the drywall. The problem had been fixed with some creative thinking.

For the left front speaker, well, the wall cavity has plenty of space. It took 10 minutes to cut the hole, fish up the speaker wire, and use the bracket to sandwich the drywall. I became very envious of those people who have large enough walls that all their speakers installed this easy. It would have saved me 10+ hours of work and a lot of money in construction costs. But two weeks and a lot of construction work later, all the speakers were in place. Finally it was time to put on some music and movies and listen.

A Slow Build

For my home theater, I’m using the Anthem MRX 1120 receiver, which has power for 11 channels without an external amplifier. The five main channels use class AB amplifiers while the rears (not used here) and height channels use Class D amps. I made sure to talk to both Anthem and KEF before the project and both said the pairing would work well, especially in a room my size.

Upon firing them up, the front speakers impressed me with their bass but also didn’t leave me with an impression beyond “That sounds good”. This sounds a bit strange, as you’d want something to leave you with an impression, especially after spending money and hours of time getting it setup. As I realized over the next few weeks, this is actually the exact impression I should want the speakers to leave on me.

One problem with reviewing speakers is that your brain adapts to the sound of them over time. When people often write about a speaker breaking in over time, or coming to life, more likely that is their brain learning to listen to the flaws and adapting to them. When I turned on the KEF in-walls and didn’t have a huge reaction to it, that is because my brain didn’t hear those flaws and issues and then have to adapt to them over time. I didn’t hear peaked treble or an absence of midrange, and I heard a soundstage that is wide and detailed.

The more I listened to music, the more impressed I became with the KEFs. Since the home theater doubles as my home office, I spent 5-6 hours a day listening to the KEFs with a wide variety of music. My worries about a soundstage not being wide or lacking the precision of my prior bookshelf speakers were allayed as locating instruments in the mix was easier than before. In dedicated two channel music, bass response is better than expected for an in-wall speaker, and better than my R300 bookshelves are.

Listening to Johnny Cash’s cover of “Hurt” his voice is anchored in the center of the room. As the chorus starts and the music builds around him, the KEFs don’t slouch as they are pushed. The sounds of the piano and guitar are easy to distinguish, but the vocals never take a back seat to them or are hidden away. Going back to one of my all time favorite albums, Belle & Sebastian’s The Boy with the Arab Strap, all the small details show up. From the opening notes bouncing back and forth during “Sleep the Clock Around” to the drums that are tight and controlled, I find myself listening to the music for fun instead of focusing on it for a review.

With movies, the KEF system has never disappointed. If you’ve only used Atmos with the ceiling firing modules, as I had at home, you don’t know what you are missing. Soundtracks that take full advantage of Atmos, like Sausage Party and Deepwater Horizon, are spectacular. The KEF system places objects all around me in the room and pans are seamless between the speakers. I cannot hear the transitions from one speaker to another, instead it moves as if there are speaker everywhere in the room.

Vocals from the KEF center channel are crystal clear. I designed the enclosure for it to have a small tilt, so it is below the TV but angles up towards ear height. The front three channels also hide behind my 92” Stewart Studiotek Snomatte 100 screen. It is acoustically transparent and drops down in front of them and my TV. This setup was not possible before with speakers that aren’t in-wall my space.

I also wasn’t sure about the ability of the Anthem receiver to drive the KEFs to the levels I would like. I’ve never felt the need to push the Anthem above a level of -10dB, and even at that level it is louder than the room needs. Would they benefit from an external amplifier? Possibly, but you don’t need one to be able to use them. In addition to the Anthem a powerful receiver like the Denon X6300H or Arcam AVR 850 should do fine.

KEF THX In-Wall System Conclusions

At the outset of this, I said my most important goal was that the KEF THX system provides reference quality audio for reviews. Being invisible was the secondary option to that. Compared to the R300 system that it replaced, the KEF system offers better bass response in the front channels. The vocals and midrange, with the UniQ driver, keep the same wonderful sound I bought the R300’s for. While an R900 might offer better bass response, there is no way I can put those in my room.

That is where the KEF system has undeniably succeeded. It has given me a reference class system in a small room, and it takes up no space while doing so. No stands or towers that occupy a few square feet. No cables to trip on that are in the way. No worries that my kids are going to knock them over if they’re in the room. Instead, I have a room that looks clean with a TV on the wall, and a system that is invisible.

Going with an in-wall system is not something everyone can do, but for those that can it is possible to do a system that is hidden but doesn’t sacrifice quality. I know that the KEF system is going to deliver the performance I need when watching movies or music to test gear, and it does so without taking up any space. I hope if you make the jump that you’ll have walls and ceilings that are easier to install the speakers into than mine were.