Norwegian Bjorn Erik Forberg built an amazing home theater with his own two hands, including the speakers and acoustic treatments.
Many AVS members find great pleasure in designing and building their own home theaters, while others delight in building their own speakers. But Bjorn Erik Forberg (BEF-NO) went a step or two farther in the basement of his home just outside Oslo, Norway, not only building the theater and all the speakers himself, but also the acoustic diffusers.
As a THX Level 2-certified installer, Bjorn Erik had a clear idea of what he wanted in a home theater. "It had to be a room that measured at least 6 x 3.5 meters [roughly 20 x 11.5 feet] with space for six people. Also, it had to be sonically isolated from the rest of the house. Sonic isolation was especially important because I am very fond of loudspeaker systems that produce lots of energy."
When Bjorn Erik and his wife were looking for a house, a good home-theater space was a must. The house they selected had a long, narrow basement, which he divided into two rooms—one would be the theater, and the other would be a workshop for all the building he was about to do.
This long basement would eventually have a wall in the middle, dividing the theater at the far end from the workshop, where all the theater components—framing, walls, risers, speakers, and diffusers—would be built from scratch.
It took Bjorn Erik about six months to develop the plan for the room and about nine months to finalize the speaker design. It took another six months to actually build the room in his spare time—which is quite limited because of his day job as a project manager for Stanley Security.
Bjorn Erik built a room within a room for maximum sound isolation, and the walls are double-layer plasterboard with Green Glue between the layers.
Using a program called AcousticCalculator, Bjorn Erik determined that the most problematic frequencies in terms of reflection from the ceiling extended from about 750 to 3500 Hz, and the areas that would create the most problems were down the middle and near the walls. Using 2x2" lumber cut to different lengths, he built three long diffuser panels for the ceiling.
Back in the workshop, Bjorn Erik constructed his own diffusers from different lengths of 2x2" lumber.
The main speakers are based on a design by Stig Erik Tangen, which Bjorn Erik modified. "The LCRs include three Beyma 15" woofers to reproduce the range of 25-200 Hz, a TAD 12" midrange to cover 175-2000 Hz, and a Beyma horn tweeter that goes from 2200 to 21,000 Hz. All the surround channels are based on the same principle, with a Beyma 15" woofer covering 25-900 Hz and a Beyma horn tweeter from 900 to 21,000 Hz; they have the same sonic signature as the front speakers. I use an active crossover and DSP in a stack of Crown I-Tech amplifiers to power the entire system, which gives the room a very uniform sound with a lot of dynamics and power in every channel."
Bjorn Erik built his speakers based on a design by Stig Erik Tangen.
Crown I-Tech amplifiers provide all power, active crossover, and DSP for all speakers and subwoofers. The electronics are located outside the theater and controlled by IR repeaters.
The subwoofers were designed to blend well with the main speakers, with Beyma 18" drivers that extend from 13 to 120 Hz. "When I was testing the system, they were only level adjustment that was needed. You cannot hear the sound cross between the mains and subs. Also, the subs are used only for the LFE; all the main channels are set for large speakers, which play from 28 to 20,000 Hz."
The sensitivity of the speakers is remarkable—103 dB/W/m for the front LCR, 101 dB for the surrounds, and 100 dB for the subs. "I've measured the main speakers at 134 dB SPL!"
In an intermediate stage of development, Bjorn Erik sits atop the center-channel speaker to give a sense of scale to the whole front-speaker setup.
On the back wall, he wanted to extend the frequency of diffusion down to 200 Hz, so he modified his diffuser design and covered the back wall with panels. After all the treatments were installed on the ceiling and back wall, Bjorn Erik says the sound is very natural and open. The frequency response of the room is flat from 13 to 21,000 Hz, but he adjusted it to add a bit more weight in the LFE "for a greater effect on movies."
The rear wall is covered with diffusers around the back-surround speakers; two DIY 18" subwoofers occupy the lower corners. The diffusers and speakers were subsequently covered with acoustically transparent fabric.
The final front-speaker configuration is mighty impressive, including six 18" subs and three custom-modified LCR speakers.
Bjorn Erik says his biggest challenge was finding a good acoustically transparent projection screen. "I have tried about 10 different screens, and I finally found one that does not destroy the sound and gives a good picture at the same time." He built the frame with a hinge at the top so it can be lifted out of the way to access the speakers behind it.
The final theater sports a 138-inch, 2.35:1, acoustically transparent woven screen from Norwegian company DreamScreen.
The seats are also from DreamScreen.
In this diagram of the final room, the center block is the floor (with three green bands representing the diffusers on the ceiling), and the surrounding blocks are the walls. Imagine that the wall diagrams are hinged at their bottoms, and when you lift them up, they form a 3D model of the room.
Bjorn Erik says his greatest moment was when he first played music in the room—Hitman by David Foster. He also played recordings from young Filipina singer Charice, which "got tears rolling down my cheeks." Of course, movies are also amazing in this stunning room.
By building everything himself, the total cost for the room was no more than $8000, but the gear was another story—Bjorn Erik estimates the total equipment cost was around $140,000. "The VAT [value-added tax] is 25% in Norway, so everything costs more here." But I have no doubt that it is worth every krone.
For much more detail about how Bjorn Erik Forberg's home theater came together, check out the build thread here
If you'd like your home theater considered for Home Theater of the Month, PM me with the details and a link to your build thread if available.
Oppo BDP-95 Blu-ray player
Oppo BDP-103 Blu-ray Player
Sherbourn PT-7030 preamp/processor
Crown I-Tech 4000 (9)
Crown I-Tech 8000 (2)
DreamScreen ultraHD Acoustic V5 (2.35:1, 138", 1.0 gain, acoustically transparent woven)
Front LCR: DIY (based on Tangen AV Design inConcert Miles with 3 Beyma 15P80Nd 15" woofers, TAD midrange, Beyma TPL150H horn-loaded ribbon tweeter)
Side and rear surrounds: DIY (Beyma 15P80Nd 15" woofer, TPL150H ribbon tweeter; 2 side, 2 rear)
Subwoofers: DIY (Beyma 18W1600Nd 18" woofers; 6 in front, 2 in rear)
IR-Link to equipment rack outside the room
DreamScreen Cineseat Promotor (3 front row)
DreamScreen Cineseat Theatre (5 second row)
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