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8/1/2000

Producing a slammin' bass track starts with getting a great recording. A well-recorded bass guitar track can grace a mix with warmth and power, but a poorly recorded one can obscure it like a murky cloud. Which microphones are best for recording electric bass? How does mic placement affect the sound? Should you use a DI box? What about compression and EQ?

We'll get to all of that sexy stuff, but first let's address how to set up the instrument itself. Unless your source sounds great to begin with, you'll just be dealing with a "garbage in, garbage out" situation. Put another way, a skillful recording of a lousy instrument is just that.

FIRST BASSBeyond proper tuning and intonation, the three most common problems with electric bass guitars are grounding noises, fret-related artifacts, and poor height adjustment of the pickup.

The time to hunt down the cause of ground-related hum and buzz is not just before you press the Record button. Most DI boxes have a ground-lift switch that may kill the noise, but what if you are not going direct? Fortunately, if the hum goes away whenever the player is touching the strings, there's an easy solution. Attach one end of a piece of wire to the guitar's tailpiece section, at a point where it will be out of the way and won't make any noise as it moves about (for example, wrapped tightly around a string behind the bridge). Stick the other end of the wire into the rear pocket of the player's pants. This usually eliminates the problem.

Fret noise can result when an instrument's string height, or action, is too low. The best solution is to raise the action, but that will adversely affect the intonation, so you'll need to adjust it, too. What can be done if you must record immediately? Borderline fret-noise problems are often avoidable if you simply play with a lighter touch (which is usually a good idea anyway). In my experience, most extraneous bass-track noises are caused by heavy-handed or otherwise poor technique. A moderate and consistent attack yields the most even tone, decreases the amount of corrective compression you'll need, and avoids the insidious clackety- clack of fret slap that plagues many amateur bass tracks. There's simply no way to roll off enough highs to rid a track of these artifacts-that is, not without making the bass sound as if it's being played through a bale of wet cotton. In this case, an ounce of prevention is definitely worth a pound of cure.

Before the session, have the bassist play a chromatic scale from top to bottom and back on each string, with all EQ and tone controls on the instrument and amplifier set flat or bypassed. Do all the notes on a particular string tend to sound either boomy or thin? If so, you may need to adjust the pickup height for a more consistent response across the full range of the instrument. If the notes sound boomy, move the pickup farther away (down) from the strings; if the notes sound thin, move it closer. Failure to nip this problem in the bud will force you into riding the fader on certain notes or applying massive amounts of frequency-conscious or split-band dynamics processing at mixdown. Again, an ounce of prevention...

Now that the instrument is ready to rumble, it's time to set up the amp, microphone, and DI box for recording.

SPLIT PERSONALITYYou probably noticed I mentioned using both an amp and a DI box. If you have enough open tracks to record the miked amp and the DI signal on separate tracks, by all means do so. You'll get two different timbres for the same performance and far greater flexibility in sculpting the final sound at mixdown. The miked amp will have more ambience, and the DI will usually sound clearer and more focused. When you mix, you'll be able to choose which timbre is more appropriate or, more likely, combine the two tracks for a fat hybrid sound (more on this later). In fact, if you're pressed for tracks but have two available mixer channels, you can combine the two signals via the multitrack bus-adjusting each fader to favor one sound over another if desired-and record the summed channels to one track.

No matter how many tracks you decide to use, you'll need to split the signal at the DI box so that one path goes to the mixer and the other goes to your bass amplifier and speaker cabinet (see Fig. 1). For this purpose, most DI boxes feature an unbalanced input and an unbalanced output-typically on 11/44-inch phone jacks-along with a balanced output, usually on an XLR connector. Simply plug the bass guitar into the DI's unbalanced input, connect the unbalanced output to an instrument input on your bass amp, and route a mic cable from the DI's balanced output to a mic input on your mixer. The DI box converts the bass's high-impedance, unbalanced instrument-level signal to a low-impedance, balanced microphone-level signal that gets routed to its balanced output. But before the conversion, the DI splits the signal and sends the unbalanced input signal-unchanged-from its unbalanced output to your amp.

You can choose from a number of DI boxes, ranging from inexpensive solid-state models to pricier tube offerings. The Stewart Audio ADB-1 ($109) and the GRM BPH Missing Link are two cost-effective solid- state workhorses. The BPH box sounds a little brighter and more open, but the ADB-1 nevertheless offers plenty of presence. (Unfortunately, GRM recently closed shop, so the BPH is no longer available; but you might be able to find one secondhand.)

If you can afford them, the Demeter HdI-1 Stereo Tube Direct/Line Driver ($899) and the Ridge Farm Gas Cooker ($1,279) will take your sound to another level. Both are tube DIs that add a warm, lush dimension to bass guitar. I'm slightly partial to the Demeter unit; it offers a bit more presence and definition than the Gas Cooker, which has a softer sound.

AMPED UPBecause loud sources with long wavelengths (in other words, bass frequencies) record best in big rooms, you should put the bass cabinet in the largest room you have-unless you're recording a drum set simultaneously, in which case you should use your second-largest room for the bass. By recording bass and drums in separate rooms, you'll achieve the isolation needed to perform punch-ins on the bass track without having to deal with clunker notes that leak into the drum mics.

If possible, place the bass cabinet in an acoustically dead room. Adding digital reverb to a bass track rarely improves it, so why would you want natural reverb on that track? A dead room gives you a tighter sound. A carpeted space will do in a pinch, but a room that's correctly treated with acoustic foam or fiberglass wall panels will sound much better.

All rooms, even those that have been professionally treated, have at least a couple of lingering bass room modes, or narrow notches, in the low-frequency response that will sound either boomy or weak. These problems will be evident only in certain parts of the room. In fact, moving the bass cabinet just 6 to 12 inches can make a profound difference in the sound. Before you set up the mic, move the bass cab around while playing a scalar motif to find the spot with the most even frequency response. Bear in mind that moving the cabinet closer to a wall (or especially into a corner) will boost the overall bass response. But again, some individual notes may sound weak if your placement results in room-mode interference.

Many bassists make the big mistake of going for a cabinet position that gives the biggest bottom end. They also often boost the bottom frequencies on the amp's onboard equalizer to excess. But what works in a live situation doesn't always work in the studio. The sound you produce should be reasonably balanced across the bass and middle frequencies-one that you can later tweak to complement the mix without applying tons of corrective EQ.

PUT THIS THEREI generally use cardioid microphones when recording bass; placed on-axis (pointed straight at the source), they give a hint of room tone but focus mostly on the direct sound emanating from the cabinet. My hands- down favorite mic for recording electric bass is the Lawson L47MP ($1,995), a reasonably priced tube condenser that provides a fat, luxuriant sound. My favorite dynamic mic for bass recording is the AKG D112 ($338). An admittedly pricey alternative, the Neumann U 87 condenser mic ($2,825) has also given me great results.

I like to place the mic 1 to 2 feet away from the cabinet. If you're miking a cab with multiple drivers, stick your head near each speaker in turn and listen. (If the amp is too loud for comfort, just note from the control room how the mic sounds on each speaker.) Because every speaker has a slightly different personality, put the mic opposite the one that offers the closest sound to what you're going for.

To get the brightest sound, place the mic directly in front of the bass cabinet and point it straight at the center of the speaker cone; for a softer sound, put it about 45 degrees off to either side of the cabinet (but again pointed at the speaker cone). If you're getting a lot of fret slap, buzz, or other extraneous sounds, pointing a directional mic slightly away from the cone will roll off the extreme highs and reduce the noise somewhat. Just make sure the mic isn't pointing at another sound source when you position it, or you may get unwanted bleed.

MORE THAN THE SUMEven once you're getting a great sound from both the mic and the DI, there's still room for improvement. You can combine the two tracks for a fatter sound than either delivers on its own, but merely summing the tracks together tends to yield less-than-spectacular results because the two signals are typically out of phase with each other.

What causes this? By the time the signal from the bass cab reaches the mic, its waveform has progressed partially through its cycle, whereas the DI'd signal is captured almost instantaneously. The two signals are in different phases of their cycle, so they will probably interfere with each other destructively upon reaching the mixing console (see Fig. 2). One likely result is a reduction in the amplitude of the combined signal. For reasons too complex to discuss here, the resultant weakening of the sound usually affects the bass frequencies-exactly the band we wish to reinforce!

The solution? Delay the DI signal by the same amount as the miked signal so that both are in perfect phase alignment. A good rule of thumb is to delay the DI signal by 1 ms for each foot that the mic is placed away from the cabinet. This is easily done; most digital mixers allow you to delay individual channels in 1 ms increments. If you're mixing on an analog board, you can patch in a digital delay on the DI signal's channel insert. Listen to the combined mic and DI sounds while fine-tuning the DI signal's delay time in 1 ms increments.

You'll know when it's right, because the sound will be huge. In fact, this procedure may give you too much bass. Trust your ears, and tweak the delay time until it sounds right to you. (If you don't have a digital delay available, try reversing the channel's polarity to improve the sound.)

TIGHT SQUEEZEI always use compression when recording electric bass on full-production numbers. Because the human ear is not very sensitive to bass frequencies, any significant level fluctuations tend to result in weak notes. I've yet to meet a bass player who can deliver the perfect attack envelope and sustain on every note, so for a consistently full sound throughout a mix, compression is a must.

I generally prefer soft-knee compression on electric bass, with ratios ranging from 2:1 to 4:1. However, on slap bass I sometimes go with a hard-knee setting for tighter control of peaks. To get a really even sound that doesn't jump out, I'll set the compressor's attack time somewhere between 1 and 10 ms; for a punchier sound that emphasizes the attack of each note, I'll try lengthening it to 20 ms or so.

A release time of around 500 ms is good for adding sustain to a part with long, sparse notes. When notes are coming fast and furious, though, I'll use a relatively short release time; this lets the compressor recover from attenuating a loud note in time to avoid squashing the attack of a quieter note that follows. But use caution when setting the compressor's release time: too fast a setting can result in very audible distortion. The reason for this is complex, but suffice it to say that bass wavelengths are so long that a quick change in their level (per short release time) can transform them into something approaching a square wave. A release setting of 100 ms or longer is usually safe.

SHAPE SHIFTINGI never record electric bass with EQ. Instead, I prefer to massage the sound through mic placement. Your sound will be better preserved if you EQ only once-and because you'll probably end up tweaking the EQ at mixdown, why risk making wrong decisions early on? Therefore, the following comments refer to equalization at mixdown.

When the bass sounds too thumpy-that is, when each note sounds as if a large object is being dropped- use a highpass filter or shelving EQ to roll off frequencies below about 50 Hz. For a bigger bottom without increased rumble, try boosting at around 80 Hz. If the bass is too boomy, try cutting in the neighborhood of 125 to 160 Hz. A cloudy or muddy bass is often improved by cutting around 200 Hz; this is usually preferable to boosting the mids, which can cause a harsh or "wooden" sound. As with all matters pertaining to sound, your ears are your best guide to using EQ effectively.

TROPHY FISHInstrument setup, room acoustics, cabinet position, microphone choice and placement, phase relationships of combined DI and mic signals, compression, EQ-all of these details are important. Pay careful attention to every facet of the recording process, and you'll be on the fast track to landing the Big Bass!

Michael Cooper is the owner of Michael Cooper Recording, located outside the small resort town of Sisters at the base of the Oregon Cascades.

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