A Beginner's Guide to Building a Budget 5.1 Editing Suite
COW Library : Art of the Edit : Jonathan Bird : A Beginner's Guide to Building a Budget 5.1 Editing Suite
For years, I have produced an underwater science/adventure series that airs on public television called Jonathan Bird's Blue World. We produce it in HD and deliver it with a stereo (2 track) mix. For international release, we deliver it with an "M&E" (Music and Effects) mix in addition to the stereo English mix, so it can be adapted to foreign languages. Because our program is 75% underwater, a great deal of the soundtrack is foley.
I really enjoy sound editing and mixing, so we don't farm this part of the production out. We do it ourselves because it's fun, creative – and cheaper!
While I consider myself a pretty good "audio guy" I have never done a mix in 5.1. In fact, our little production studio didn't even own the gear to do a 5.1 mix until recently.
We're currently working on a 6K film for release in the fulldome theater market about underwater astronaut training called Space School. These theaters all have large 5.1 systems and a 5.1 soundtrack is required for this market. I figured, how hard could it be to do the 5.1 mix ourselves? We decided to build a 5.1 monitoring system around our edit bay and start mixing in 5.1.
It's not that tricky, to be honest, but there are a few things we learned (the hard way) along the way. I thought I might share a few experiences to (hopefully) make someone else's life easier.
4K/5.1 editing system at Jonathan Bird Productions. HP Z820 Workstation running Premiere CC. HP Dreamcolor monitor, 50" Samsung 4K playback monitor. 5.1 system driven through Soundblaster Z card to Yamaha surround receiver. Speakers are Fluance.
When you start thinking about putting together a 5.1 suite, you probably think first about speakers. In an ideal world, a 5.1 suite has 5 identical speakers and a big subwoofer. The speaker levels are calibrated so they all produce the same sound pressure level given the same input. So my first thought was to buy 5 of the same powered monitor, like the KRK ROKIT 6, or something similar.
However, the next thing to consider is: how do you turn the volume up and down on all 5 speakers while keeping them calibrated to each other? You can use the computer's volume controls, but that's pretty clunky. Furthermore, all 5 speakers will need two cables: the signal and the power. Turning the system on involves going to each individual speaker and flipping the power button – which is conveniently located on the back of most powered monitors. And, of course, powered monitors are not cheap.
So I started thinking about using a 5.1 receiver (as one would use on a home theater set up) to run the speakers. It has a convenient power button for the whole system and a nice volume knob – even a remote – for pretty short money – a 5.1 speaker system can be had at all price ranges from about $200 and up.
The only drawback to buying a complete 5.1 speaker set is the fact that all the speakers are not usually the same. These systems for home use are typically based around a larger pair of front speakers, a smaller, horizontally-designed center channel speaker and a pair of even smaller "bookshelf" speakers for the rear. In the end, this is the way I went for my studio even though it's not ideal. The reasons were mostly based on space, finances, and how I would mount the rear speakers to the wall.
CONNECTING TO THE COMPUTER
I (mistakenly) assumed that the best way to get audio from the computer sound card to the receiver would be to use the fiber optic S/PDIF input that all surround receivers have. This, I reasoned, would run the audio from the computer sound card to the receiver in one easy cable. Wrong.
Sound cards these days are so good, that virtually any card has 5.1 capability, particularly the Sound Blaster and similarly-featured cards. I bought a Sound Blaster Z card on newegg.com for under $100. One of the reasons I liked this card was the fiber-optic output, thinking I could use it to connect to the receiver.
The sound card output using (3) 1/8 inch stereo (analog) jacks.
But when I got the speakers set up, the receiver wired, and the card installed, I found that no matter what I did, the 5.1 signal ended up as plain stereo at the receiver. Turns out that the fiber protocol can handle 2 channels of PCM audio or a 5.1 multiplexed/compressed signal (such as the Dolby Digital bitstream put out by a DVD or Blu-ray). So if I played a DVD movie in the computer, the 5.1 worked through the sound card via fiber. But a computer/sound card cannot create a compliant 5.1 bitstream in real time that a receiver can decode – which is why the sound card settings always reverted to stereo when I selected the digital output on the sound card.
Realizing my mistake, I now had a small problem. I had to use the 6 analog outputs (consisting of 3 stereo 1/8" jacks on most sound cards) to get 5.1 to the receiver. However virtually no home theater receivers these days have analog 5.1 inputs anymore! They have optical and HDMI inputs for 5.1 audio, and analog inputs only for stereo sources like a CD player. So much for that brand new Sony surround receiver I just bought!
Back about ten years ago, when 5.1 in the home was still rather high-end, almost all the receivers had analog 5.1 inputs. So I went to my home theater system in the living room and pulled out my old Yahama 5.1 receiver from 2001. Aha! Analog inputs! So my home theater got an upgrade to a nice new Sony surround sound receiver and my old Yamaha saved the day in the studio. These days, for someone looking to do this without an old receiver lying around, eBay is the best option. For $50, you too can have an analog 5.1 amp!
I ordered three 1/8" stereo to RCA plug Y cables of appropriate length to connect the three output jacks of the sound card to the 6 RCA inputs of the receiver. Then I set the sound card preferences for analog output of 5.1, and I actually had sound in all the speakers!
On the back of the Yamaha surround receiver, 6 analog inputs from sound card using 1/8 inch stereo to RCA "Y" cables.
Within Premiere, after setting the sound settings and creating a 5.1 sequence, I was able to verify that I could pan the sound around the 5.1 space. This was a major achievement after all the hassle and wasted time with the optical output.
The speakers in a 5.1 mixing environment should all be the same distance from the editing position so that the arrival time and phase of sounds is the same for all channels. In a typical editing suite, the tendency is to put the front speakers right on each side of the computer desk and the rear speakers on the wall behind, much too far away. So if your front speakers are against a wall and can't be put further from the editing seat, the rear speakers should be close behind on stands, not ten feet away on the wall.
Mounting of rear channel speakers on the studio wall.
Once you have placed your speakers correctly, next you need to calibrate the speakers. Most surround receivers essentially treat the front pair of speakers as "reference" and then you have fine-tuning adjustments +/- 10dB or so on the center channel and rear speakers within a menu in the receiver. The sound card control panel also usually will have adjustments for level on each channel if your receiver doesn't.
The newer receivers have an auto-calibrate, where you just put a microphone in the middle of the room, hit calibrate, and the receiver plays tones and adjusts itself. Unfortunately, these newer receivers don't seem to have analog inputs! So for me, the calibration would be manual.
Essentially, you want to play pink noise alternating back and forth from one of the front channel speakers to the center channel speaker. You can build a simple edit in Premiere (or your editing software of choice) to do this. Then while it's playing, adjust the level of the center channel in the receiver's menu to match as closely as possible to the level of the front speaker.
The best way to do it accurately is a Sound Pressure Level meter. Don't roll your eyes...you can get one online for under $50. But if you are cheap, you can do it by ear and get it close. Then do the same thing for the rears, matching their output as best you can to the level of the fronts. Of course, if all your speakers are the same, there should be no adjustment to be done. But if like me, you do not have the same speakers in all 5 spots, you will need to calibrate. If you don't calibrate, your mix might sound completely wrong on other playback systems.
Calibrating the subwoofer is a little harder. It must be done with a Sound Pressure Level meter. It should produce the same SPL as any other speaker in the system when provided with pink noise at the same level. But you can't do it by ear because the frequencies are so vastly different. You really need that SPL meter.
Some NLEs do not allow sending audio only to the LFE (subwoofer channel) without also sending it to one of the other channels. Therefore, to calibrate the subwoofer (for example in Premiere) you want to send audio to the center channel, with the subwoofer send on that track set to 100%. Then simply unplug the RCA jack on the amp that feeds the center channel. Now the center channel is quiet and only the sub is producing pink noise. Now alternate that with one of the front channel speakers to set the level of the sub using your SPL meter.
Digital Instruments SL-814 Digital Sound level meter used at seating position to calibrate all 6 channels.
Most subs are powered. The signal will go from the computer to the receiver, then back out of the receiver as a low level signal on a RCA cable to the sub. The amp is in the sub, so you will set the gain of the amp at the sub, not in a menu in the receiver.
Why have it go through the receiver at all? Because the receiver adjusts the volume of the sub along with the volume of the rest of the speakers as you turn the volume knob.
Depending on how you are monitoring your video, you may find that the audio and video are out of sync when you set up a system that sends video through a different path than audio.
Most modern HD and 4K monitors have a delay in processing the picture for display. This can range from 50-200 milliseconds. Of course, the television manufacturers know all about this, so they delay the audio that comes in with the picture (on the HDMI cable, for example) by the same amount, to keep them in sync.
But when you send 5.1 audio to a surround receiver in analog, it doesn't get any delay. So the audio comes out of the speakers 50-200 msec earlier than the picture appears on the monitor, and the result is some pretty serious lip sync issues, which drives most editors crazy and make accurate sound effects work impossible.
Unfortunately, as of this writing, Premiere doesn't have a function to delay the audio, and neither does the software for most sound cards I have seen. (Ironically Premiere does have the ability to delay the picture, but not the sound).
In this case, the most logical solution, believe it or not, is three stereo delay units in between the computer and the amplifier, giving you six channels of delay.
My gadget of choice for this is a compact delay unit designed just for this purpose called AV Toolbox AP-411 Lip Sync Corrector. It is adjustable in 50 mSec intervals with a tiny knob, so it's easy to dial 3 units to the same delay time (which is important to maintain synch from front to back).
They are installed into the back of our rack with some velcro because they are so small they won't stay put otherwise. Note that each of these little delays has a "wall wart" power supply and no power switch. So if you don't want them just running all the time, you can either manually plug and unplug them to turn them on and off, or you can connect them to a switched power source like a power strip.
However, most surround receivers have at least one "switched" AC outlet on the back, which goes on and off with the power switch/remote control. If you use a lightweight extension cord with three plugs on the end and wire all three power supplies (they consume very little power) to the switched outlet, your digital delays turn on and off with the surround receiver, so they don't have to be manually turned on and off each time the system is used.
Now that you have a functioning, calibrated 5.1 monitoring solution, it's time to start editing. Don't even get me started on the quirkiness of almost every single NLE when it comes to mixing in 5.1. Most 5.1 mixing in the pro world is done in ProTools. If you want to do it in Premiere...well, that's another article!
Jonathan at the editing suite. Nothing beats editing in 4K with surround!
All images © 2014 Jonathan Bird.
And for more from Jonathan's editing suite and underwater photography...
Jonathan Bird's Blue World
Jonathan Bird's Blue World is an underwater adventure series co-produced by the titular Emmy Award-winning cinematographer and naturalist, and the Oceanic Research Group. The 30-minute episodes cover a variety of subjects in and around the water, including marine research and underwater exploration. Needless to say, it also features stunning underwater imagery.
This truly epic conversation with Jonathan covered his trajectory across over 20 years in the industry, through NLEs (from Avid, Media 100, FCP, and now Premiere), camera formats (Hi-8 to 4K), computing platforms (adding HP workstations to his previously all-Mac shop), and business models – starting with creating the TV show he'd always wanted to work on.