Headphones & Sound Treatments - 12/11/2018
Another year another annual update. I am happy to say that this update "wraps" up the theater though.
2018 has been a busy year. The two big DIY projects that delayed the completion of the theater were repainting the entire interior of our 4k sqft house, and completely gutting and rebuilding our master shower after a leak in February :eek:
Still. we managed to get a few hundred hours of fun out of the theater and wrap up the loose ends recently.
7 x Headphone Support:
This was a done a little unconventionally, but the end result has been great in my opinion. Basically, I ran a cable from the AVR's 1/4" headphone jack to two Behringer Microamp HA400 4 channel headphone amplifiers in parallel for a total of 8 headphone outputs, each with its own volume control. Originally, I wanted to break out the volume control to each chair, but I shelved those plans for now. I didn't worry about loading the AVR headphone output too heavily as the input impedance for each headphone amp is orders of magnitude higher than a normal set of headphones. Parallel worked nicely and the output of each channel at the amp was nice and clean.
To get the signal from the amps to the chairs, I ordered chassis mount XLR/1/4" combo jacks and I 3D printed some adapters I designed so I could cleanly install them into the bottom of each chair arm's storage area.
My custom electrical spin on this setup was automating the headphone jack activation in the AVR. Normally the headphone jack only activates when a 1/4 jack is physically inserted into the receptacle which has the dual purpose of deactivating the AVR's speaker outputs.
Part 1 of modifying the headphone jack activation = Physically altering the headphone jack PCB inside the AVR by cutting the trace related to the jack switch built into the receptacle that lets the AVR know a 1/4" jack is inserted. After the trace was cut the headphone jack basically acts as if there are headphones plugged in all the time. It's only when the trace is reconnected that it goes back into surround / speaker mode. With this done, I soldered two wires to either side of the cut on the original trace and ran it outside of my AVR to the normally closed contacts of a relay. Doing this made it so the AVR once again defaults to surround / speaker mode, but if I energize the relay externally, the AVR switches to headphone output.
Part 2 of modifying the headphone jack activation = Controlling the Relay. At this point I can leave my headphone jack to headphone amps connection plugged in at all times and remotely switch between headphone output and speaker output by switching the state of the external relay. The next step was how to remote control the relay. My solution was to use an Arduino Uno and a IR diode and code the arduino to power the relay with IR code1 then remove power to the relay with IR code2. There's more to it than that, like what to do if/when the power resets, but that's the gist of it. In the end I created actions for my Harmony 900 that could sequence the arduino through the IR diode which would switch the relay on/off and turn my headphone output on/off.
Sound Treatments:
The last loose end to tie up was my sound treatments. For this I built three 2x2' panels and six 2x4' panels based on 2" Roxul Rockboard 60 and wrapped in fabric I sourced at Walmart. Sounds simple enough, but my other big projects in 2018 + my lack of motivation* to build the panels pushed this project out until just a few days ago. *My motivation also took a hit due to the fact that 90% of my theater's audio output has come through the headphone system (I have young kids and 90% of my theater's use happens past their bedtime) so that kindof zaps the old motivation center knowing that I'm not even using the speaker all that often. Still, we wrapped them up last weekend:
