Mic a bass amp? The mere thought can cause the brain to lock up due to the heavy conceptual hassle of dragging a bass amp into whatever space you call a studio, putting a mic in front of it, and firing the monster up. After all, isn’t that what direct boxes were invented for? Can’t you just plug into your audio interface and get to bass-ifying with a well-crafted bass-amp model?
Yes, you can. And there’s nothing wrong with that. However, there’s also a bounty of low-end booty to be had by capturing the sound of a bass amp chugging in a room. It’s more trouble, but the process also affords you the chance to discover tones that are unique to your taste, rather than use what someone else modeled and packed into a plug-in. Furthermore, miking a bassist’s rig is the best way to document that player’s live sound. So let’s ban the direct box and plugins, and see what mics can do for your project’s bass sound.
To start, I dragged out an early ’70s Fender Bassman head and matching gigantor cab. Unfortunately, the 30- year-old cab rattled and buzzed like it had a sack of maracas duct taped to it. After removing the 800 screws holding the back on, I tightened up the screws holding the speakers to the baffle, and screwed the back of the cab down so tight it may never be removed. Remember—as when recording a drum kit, you have to listen for any physical anomalies that will compromise your sound and eradicate them. In the case of the bass, this may also mean removing items from the studio that make noise when the amp is raging, setting the cabinet on a foam pad if you hear less-than-wonderful rumbles or buzzes, and so on.
Now, it was time for mic selection and positioning. I went with a Shure SM57 first, and jammed it right up against the speaker—just as if I were miking a guitar amp. The result was a magnificent reproduction of crappy bass tones from every lousy punk band that ever recorded their noise to a cassette 4-track. That’s an attitude, of course, but I wanted a more “produced” punk tone, so I moved the SM57 about ten inches away from the front of the cabinet. The added airspace allowed the bass waveform to breathe a bit, resulting in some chunk with a lot of midrange grit.
At that point, I wanted to achieve more of an old-school thump, so I swapped the 57 for an Electro-Voice RE20 large-diaphragm dynamic. Just switching the mic—and leaving it in the same, ten-inches-from-thespeaker position—immediately delivered a Motown-like wallop with a fat low end and meaty mids. I was able to fatten up the tone even more by patching in a compressor with the Ratio set between 2:1 and 3:1, and the Threshold between –5dB and –10dB. Is this fun, or what?
Emboldened, I sought one of the holy grails of bass sounds—Paul McCartney’s warm, Sgt. Pepper-era punch. I knew from reading about Beatles engineer Geoff Emerick that they used condensers and tube mics back then, so I positioned an Audio-Technica AT4050 condenser set to its cardioid pattern about two feet away from the amp. I dug the added low-end detail the 4050 delivered, but something wasn’t quite right. Remembering (from photos) the open layout of Abbey Road studios, I set the mic to its figure-8 pattern and moved it a couple of feet away from the amp. This captured more room tone and resonance, and after adding some compression (Ratio at 4:1; Threshold at –10dB), the sound definitely evoked some Fab Four vibe.
Swap and Switch
This being a free country and all, why limit yourself to a single mic, mic type, or mic position? I placed a Sennheiser MD421 six inches from the cab, dropped a Royer R-121 ribbon about two feet back, and captured a totally rockin’ bass sound with so much wallop and punch that it almost brought me to my knees. Your monster bass sound may be just a few miking experiments away, so try always anything and everything.