5.1 Mixing on a Budget - EMusician

5.1 Mixing on a Budget

Mixing in surround doesn't mean you have to take out a second mortgage. EM goes shopping at retail electronics stores for affordable consumer receivers and subwoofers that are well suited for surround applications.
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Mixing music in 5.1 surround is exciting, but the price ofequipping your studio for the task might seem prohibitive. If youlimit yourself to professional equipment, things can get expensivequickly. Does that mean that 5.1 surround mixing is the exclusivedomain of the rich and famous, or is there a way to do it on areal-world budget? By adding some consumer gear to your existingproject studio, you can mix 5.1 surround for a lot less than youmight think. (If you aren't up to speed on the basic technology ofsurround sound, see “You're Surrounded” in the October2000 issue; for mixing techniques, see “Mixing in theRound” in the May 2001 issue.)

WIDE RECEIVER

To monitor 5.1-channel surround music in your studio, you needfive full-range speakers and one subwoofer, amplifiers for thespeakers and subwoofer, a volume control with bass management, anda Dolby Digital/DTS decoder so you can check that the finalsurround encoding worked.

Fortunately, a modern home-theater receiver (also called an A/Vreceiver) takes care of those major monitoring requirements (exceptthe speakers and subwoofer) in one fell swoop. All home-theaterreceivers include Dolby Digital or DTS decoders (or both), whichaccept a digital bitstream from a suitably encoded disc in anappropriately equipped DVD player and then convert it to six audiochannels. In the studio, that conversion ability is important onlyfor checking a file that has been encoded; it is not used duringthe mixing process. However, make sure that your receiver has bothdecoding types, just to cover your bases.

More important for mix monitoring, all A/V receivers provideamplification for the five main channels, but few include anamplifier for the subwoofer, which means you'll need a powered sub.Many receivers also include preamp outputs, which let you useexternal amplifiers or powered speakers.

A large knob controls the volume of all six monitor channelssimultaneously, and a bass-management filter directs frequenciesbelow a certain point in the main channels to the subwoofer. Basicreceivers have a fixed bass-management frequency (typically 80 Hz),but more expensive models let you select from a list of cutofffrequencies. To gain access to that and most other parameters, thereceiver must be connected to a video monitor so you can see itsonscreen-display (OSD) user interface.

For project studios, it's important to use a receiver with sixdiscrete analog inputs. Those inputs are intended for the newDVD-Audio and SACD players, which have six analog outputs. In thestudio, however, those inputs are perfectly suited for acceptingthe 6-channel output from the mixer or multitrack mixdown deck formonitoring purposes.

Basic A/V receivers that provide 60W of amplification perchannel can be purchased for less than $300. You can also spend$1,000 to $1,500 — or more — for a high-end receiverwith time-delay correction (which compensates for speakers placedat different distances from the listener), calibration microphones(for automatically adjusting speaker levels), variable frequencybass-management filters, and other bells and whistles. Manycompanies make excellent receivers; check out the offerings fromDenon, Kenwood, Marantz, Pioneer, Sony, Technics, and Yamaha.Fig. 1 illustrates how to integrate a home-theaterreceiver into your surround-mixing system.

If your mixer outputs signals at +4 dBu, you need to know thatconsumer receivers are designed to accept -10 dBV signals at theirinputs. To convert from +4 to -10 levels, you can build a simpleresistive pad (see Fig. 2). If you're not ado-it-yourselfer, you can get a Line-Level Shifter from Ebtech(www.cymation.com) for about$200. That handy device changes the signal levels of eight outputsfrom -10 to +4 and vice versa. It also automatically converts frombalanced to unbalanced (and back again) depending on whether youplug in a TRS- or TS-phone plug.

SPEAK TO ME

I don't like to use consumer speakers for mixing in the studiobecause they tend to color the sound, which can disguise the realmix. I recommend using inexpensive passive studio monitors thatconnect to the speaker outputs of the home-theater receiver. Youprobably already have a pair of nice monitor speakers, so you mightbe tempted to simply add three less-expensive, alternate brand ormodel speakers for the center and surround channels. Don't succumbto that temptation; the best thing to do is match all fivespeakers.

For those on a budget, I recommend something such as the AlesisMonitor One MkII ($299 per pair). If you have a pair of theoriginal Monitor Ones, buy three MkIIs for the front left, center,and right speakers, and move your original Monitor Ones to the leftand right surround positions. Other possible choices for monitorsinclude the Roland RSM-90 ($199 each) and the Tannoy Reveal ($399per pair).

A powered subwoofer is a must, because few, if any, receiversprovide amplification for the low-frequency effects (LFE) channel,and many powered subs are available for a reasonable price (see thesidebar, “Subs for Sale”). Buy a sub with as much poweras you can afford; after all, it has to handle the LFE channel andthe bass frequencies in all five main channels. Go for at least100W, but the more the better.

CALIBRATION ON THE CHEAP

Once you have the receiver and speakers set up, it's time tocalibrate the system. You can get a nice real-time analyzer (RTA)for $1,000 to $2,000, which makes calibration a piece of cake. Butthat's a lot of money when you can do the same basic job with a $50Radio Shack sound-pressure level (SPL) meter, which thousands ofrecording studios worldwide have embraced as the cheap alternativeto a high-priced RTA.

Adjust the output level of each speaker while playing pink noisethrough it. Nearly all modern A/V receivers include a built-inpink-noise generator for setting the speaker levels properly. Whenthat function is engaged, the pink noise automatically cycles fromone speaker to the next at a predetermined rate, which means youmay have to let it go around the room several times before you getthe levels right.

Prior to beginning calibration, make sure that the correctamplifier channels are hooked up to the appropriate speakers.There's no better way to ruin the sound of your mix than byaccidentally swapping the surround and front speakers, but I'veseen it happen time and time again. So make sure everything'sconnected with the correct polarity from the receiver to thespeakers.

Start calibrating by placing your SPL meter at the centerposition where your ears would normally be, pointing it directly atthe speaker that is playing the pink noise (only one speaker at atime should be making noise). Modern receivers include parametersthat let you adjust the level of each speaker in their OSDcontrols. If you're using five matched speakers equally spacedaround the mixing position, the gain settings for the left, right,center, left surround, and right surround should all be the same,but the bottom line is that the SPL meter should read the samelevel from all five speakers (use C weighting). For movie sound,the generally accepted level is 85 dB SPL with the receiver'smaster volume set to 0 dB, but that's not critical for music.

Subs for Sale

Manufacturer and Model List Price

Definitive Technology PF15TL $699 Hsu Research VTF-2 $499 Polk PSW350 $420 PSB Alpha SubSonic 1 $439 Signet SP100 II $600 Snell QBx $700 Tannoy PS110B $499

The LFE level from the subwoofer needs to be 10 dB higher thanthe main speakers, but only within the two octaves it covers. Whenproperly calibrated with an RTA, the LFE level will read 10 dBhigher than the main speakers. However, a simple SPL meter averagesthe energy in those two octaves over the entire audible frequencyrange, which makes the LFE appear to be only 4 dB hotter whenproperly calibrated; set the receiver's LFE gain control so thatthe SPL meter reads 4 dB higher than the main speakers.

Once your receiver and monitors are properly calibrated, verifythat your mixing console is connected properly and calibrated.Start by injecting pink noise from a signal generator, test CD, orthe console's built-in generator into a single channel strip. Patchthe strip to all six surround output buses equally. (I typicallyset the console to individual-send mode rather than using thejoystick or pan/fader steering). Then set each channel send tounity gain. The surround bus output faders should also be set tounity gain.

Next, go back to the input strip and set the trim so that theoutput level is -20 dB on the console's meters. That is called -20decibels full scale (dBFS). Finally, make sure that the mixdowndeck is also showing -20 dBFS on all six tracks; if not, trim theconsole's ADAT or TDIF outputs or the tape deck's input levels.(The LFE channel only gets an extra 10 dB of gain in the finalmonitoring part of the sound chain, not the recording path.)

SMALL EQUALS BIG SOUND

Modern A/V receivers include a parameter that lets you specifyyour main speakers' size — small or large. That settingdetermines whether the receiver's bass-management function isengaged. If you specify large speakers, the bass frequencies willbe routed directly to the speakers without passing them to thesubwoofer. But if you specify small speakers (even if your speakersare physically large), the bass below 80 Hz will be pulled from themain channels and redirected to the subwoofer, which is exactlywhat you want (unless you're using big speakers that reproduce downto 20 Hz at full level).

You want to enable bass management so that any bass problems canbe heard and corrected. In a 5.1 surround — music mix, youdon't need to put audio in the LFE channel. Any bass in the mainchannels will be routed to the subwoofer during playback anyway andat the proper levels. I've done music mixes with nothing in the LFEchannel that have tremendous bass during playback. Nevertheless,what you put in the LFE channel is your business as long as youcalibrate it properly in your studio.

Surround mixing needn't cost you an arm and a leg. With aconsumer A/V receiver, five inexpensive monitors, a poweredsubwoofer, and a Radio Shack SPL meter, you can turn your stereostudio into a surround room for much less than the big shotstypically spend. All that's left to add is your creative genius,and you're on your way toward the future of recorded music.

Mike Sokol is a human being, with 2.0 ears, learning how tomix in a 5.1 environment. For some reason, no one takes seriouslyhis suggestion of using gene therapy to add 3.1 more ears tosurround-mixing engineers.