Home theater

Three years ago I built some speakers to be put next to our then-new 32" TV. The resulting speakers were dubbed Baritones, them being bar shaped and all. The idea was to have an inconspicuous mini home theater system. The speakers were meant to be as small as possible, but I was suckered into building great sounding speakers, and as a result they were not as small as I initially thought they would be.

Later on, more and more audio/video equipment entered the house, and the dresser under the TV started to fill up. So this is the train of though that hit me:

  • Why not put a shelf above the TV to put most of that stuff?
  • Nah, a simple shelf doesn't fit with the rest of the furniture. Our furniture is made with thick oak beams. So why not put the equipment on an oak beam?
  • Nah, solid oak is too expensive. I'd have to make it hollow to keep cost down.
  • So if it's going to be hollow, why not open up the top side, so the equipment can sit inside it and I'll just make a window for the remote control signals?
  • So if it's going to be hollow, why not put the speakers in there as well?

And here you have it: a huge bar with an open top side and windows on the front, and the speakers are simply part of the bar!

Click thumbnails to zoom in. Click again to zoom out, or use cursor keys to walk through all images.

Home theater setupI got an oak panel measuring 2 m by 60 cm and 18 mm thick. The TV dresser is 1.70 m wide, so the bar is 1.70 m as well. At 10 cm high there's enough room for most equipment, and more importantly the Monacor SPH-30X/8 speakers, and a depth of 40 cm gives me plenty of space for cables and power supplies etc. The top edges are also going to be 10 cm wide, so there's room for some decorative stuff or a light or something. Next to the speakers I routed two openings and fitted acrylic windows in them.

I thought of taking pictures of the whole building process, but didn't. I did a lot of routing and sanding, and if there's anything damaging to photographic equipment, it's dust. So I'd have to wait for the dust to settle down every time I wanted to take some photos. I could also have taken the bar to my studio every time, but seeing as it weighs in at about 25 kg and it's 1.70 m long, that wouldn't have been a solution either. The workshop is in the attic, the studio a floor down.

So here are some pictures of how it looks, finished:

  

The right side. There's a red backlit USB LCD (from Lcdmodkit) behind the window, connected to the HTPC. Norwegian trolls stand guard. The speakers will eventually be covered up with speaker cloth.

  

Right side zoomed out. Here you can see the Zotac ZBOX AD10 plus employed as a HTPC and server.

  

The left side has the TV receiver behind the window and of course the left speaker. Here, the Norse god Njord protects us from harm.

  

The connection to the left speaker. The speaker port also ends in this cavity.

  

The cable hole. It's covered by the mid section's beam. Getting cables through is a pain, but nothing will even stick out.



Are you wondering why I used cable ducts and didn't route the cables through the wall? Well, the outer walls and floors in our house are made of the hardest, coarsest concrete I've ever laid eyes on. Just drilling small holes in it takes a professional rotary hammer; I use a Hilti TE22. The Hilti is a tad too heavy for small drill bits, so for every 10-20 holes I drill into it, a drill bit snaps off. Imagine what it would take to route a slot in such a wall. There's your answer.

Under-the-stairs subwoofer

When I was done with the bar, I sat down to listen to the integrated speakers, and while they sound exceptionally clear, and provide quite a bit of bass response for their tiny size, real depth was simply lacking. Our living room had been lacking low bass ever since I decided to remove the Scala transmission lines. I can't remember why actually, probably because one of them was damaged.

Allow me to reminisce once again. Originally I set out to build a 2.1 system with a pair of Monacor SPH-135KEP speakers converted to coaxials dubbed Yellow eyes. While that project is still under construction, I couldn't wait to start on the planned subwoofer. The sub will simply be part of both speaker setups: the home theater bar and the Yelloweyes.

When I was renovating the rotating staircase in our living room, I closed up the steps and built a closet underneith, but I left the bottom step open. The original plan was to build a cat's nest under the stairs. They could get there by crawling under the bottom step and then eat their kibbles in peace.

Gathering dust on the shelf are my two trustworthy Monacor SPH-300KE kevlar woofers. I bought them for a high end bass guitar backline (the Yellowstones, back in 1999) and while they had trouble keeping up sound pressure wise, they provided me with breathtaking deep bass. Since they have reasonably high efficiency (slightly over 90 dB, 1W, 1m) I figured one would suffice for normal listening levels in a living room.

I have grown fond of closed box subs. I've had one in three different cars over the last decade and I really like the direct, punchy bass it produces. Ported cabinets may sound deeper, but somehow, somewhere they always sounds sluggish. As if the sound comes after the fact. The slight loss of low end from a closed box can be brought back with a shelf filter or equalizer if need be. Letting WinISD calculate a closed box for this driver with a Q of .71 was easy and the outcome was a cabinet volume of 70 liters. Since the sub is going to be under the stairs, it doesn't need finishing; heck it doesn't even have to look good. First I just made a rectangular box out of old clothes cabinet panels, mounted the speaker and gave it a go in my studio. There, it sounded sensational, and with my studio monitors playing full range, the sub could easily carry it way down to the deep end, without breaking a sweat. At a few Watts, it filled the room with deep bass.

Then I put it under the stairs, but even with a much higher input level, there was hardly anything the sub added to the room. I stuck my head under the stairs, and yup, there it was: the closet was bass lovers' heaven. But I didn't want bass in the closet, of course, I wanted it in the room. Duh. So I added a front section to the cabinet that tunnels the sound into a port just above the floor, and right to the edge of the bottom step. The closet was now much more quiet and the bass was thrown into the room.

  

This is the visible part of the sub. A rectangular port under the bottom step of a staircase.

  

Looking into the port there's an unobstructed view to the 12" kevlar SPH-300KE driver.

  

With the scoop-like port attachment, the cabinet grew quite big and unsightly, so it's only for the better it's hidden in a closet.


I ran the tests with the PA amplifier that's normally in my bass guitar rack case. As a more permanent solution I modified my old monoblock amp to fit this application. I heavily modified the preamp so it now only gives low frequency output. I used a programmable signal processor to determine the best crossover frequency and decided on 85 Hz. The speakers in the bar are starting to drop off there; it seemed the most logical to let the sub take over there. I'm not sure yet whether I'm gonna put a highpass on the bar speakers. I'd have to modify the amplifier that drives them.

UPDATE (January, 2013): well, that's unfortunate. Because the bar is firmly mounted to the wall, the sound travels right through it and keeps the neighbours kids awake late at night. Yes, it sounds incredible that two tiny 3" speakers are capable of setting an oak beam and a concrete wall into motion, but they do. I figured it was nearly impossible to mount the 25 kg bar on a damper of some sort, so I decided to disconnect the speakers for the time being, and set up the new Yelloweyes, which turned out quite nicely, I might add.

UPDATE (May, 2015): After finishing my 2015 car stereo project, and not using the second SPH-300KE woofer, I decided to convert the sub-under-the stairs to an isobaric ported cabinet. The sub will reach almost an entire octave lower this way. It will sound a bit slower, though, because of the higher group delay compared to the original closed cabinet design.

Comments

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