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by David (Rudy) Trubitt
This article originally appeared in Mix Magazine, © June, 1992
What do you want from a live sound microphone? If you answered good sound and pattern control, durability, low handling noise, a weird, yet cool shape (preferably in black with a green stripe), have I got a mic for you! But seriously folks, AKG released a new line of dynamic mics at January's NAMM show. The Tri-Power series consists of four vocal and three instrument mics designed with the demands of live sound in mind. All mics use neodymium/iron boron (NdFeB) rare-earth magnets for high output, and have black triangulated body shapes, which means they won't roll off the table when you put them down. This unconventional shape also makes the vocal mics a bit more comfortable to hold, and yes, they fit into generic 58-sized mic stand clips.
Let's get specific, starting with the vocal mics. The four models span two capsule designs. The low end of the line includes the D3700 and 3700S (which adds a recessed, but accessible on/off switch). Priced at $189 and $199, these models are designed for a musician on a budget. The D3800 ($279) and D3900 ($319) use the high-end capsule, and the D3900 includes two very recessed micro-switches for low-cut and high-boost contouring (note that prices on some of these models has since been reduced--rudy). All four vocal models have a heavy-duty steel windscreen assembly, which can be easily removed by pressing on it while turning--a child-proof cap, if you will. Once the screen is removed, the two-layer foam windscreen can be plucked out for cleaning. When the cover is removed, the capsule is still protected by a resilient plastic cage, not unlike a roll-cage on a Jeep. A quick twist here frees the capsule. The D3900 and D3800 use a shock-mounted moving magnet system to reduce handling and cable noise. According to AKG, the MMS system floats the transducer's magnet assembly from a suspension tuned to match the mass/suspension compliance of the diaphragm itself. The result is that physical shocks to the microphone body cause the magnet assembly to move the same direction and distance as the diaphragm, effectively canceling the noise. For comparison, I man-handled (person-handled?) the MMS-equipped D3800 and more conventionaly shock-mounted D3700. The difference between the two is immediately obvious. The D3800 is much less susceptible to handling noise, with the greatest attenuation in the low and low-mid region. AKG claims MMS provides a 10 dB improvement over conventional designs, and while I didn't do anything scientific enough to validate that spec., it's a noticable improvement.
The instrument mics also use two different capsule designs. The D3400 ($219) and D3500 ($239) use the same capsule and are identical mics save a very recessed low-cut switch on the D3500. The D3600 ($379), which was unavailable for testing, has an interesting twist. It's a cardioid mic with greatly reduced proximity effect, achieved by using a dual-diaphragm design. The forward element covers frequencies above 500 Hz, while the rear facing element picks up the lows. Both are coupled to a phase-corrected inductive-capacitive crossover network. AKG previsouly used thie technique on thier D200 series.
The instrument mics all include integral stand mounts, which pivot out from the mic's body. This built-in stand adapter has a couple of advantages--these mics are on the chubby side (imagine...a small potato) and won't fit into a standard clip. Also, the pivoting assembly floats in an isolating elastomer cushion, reducing mechanically-induced noise.
I had the opportunity to audition the mics at a gig in San Francisco's Kennel Club, who's house system includes a Soundcraft 200 console, EAW KF-850s and QSC amps. Three guitar-oriented rock bands were on the bill including headliner Sister Double Happiness (who had just won a Bammie award for best club band--see this month's Live Sounds). We used the two high-end vocal mics (D3800 and D3900) and the two single-transducer instrument mics (D3400 and D3500). Two independent engineers were on the show: Sister Double Happiness's Deanne Franklin (also see Mix, March '92) and Chris Kathman who also works regularly at San Francisco's Warfield Theater.
The D3800/3900 have the same broad (about 3 octave) +6 dB peak centered at 5 kHz, according to AKG's published specs. With the D3900's hi-boost switch on, the peak jumps to about +10 dB. Using the hi-boost switch and carving at the 2-3kHz range at the board produced good results. The low-cut switch is down -3dB at around 300 Hz. By 100 Hz, it's down -12 dB. To our ears, this left the mic thin sounding, so we left the low-cut switch flat. All the evening's lead singers sounded good on the D3900--bright and crisp without being harsh or overly sibilant. The 3800 was used for backing vocals, but none of the band's other front-line players did a lot of singing. When they did, it also sounded fine. The pickup pattern of the D3800/3900 is hyper-cardioid. In a word, feedback performance was excellent. Stage level was high, and there were half-a dozen wedges plus side fills but feedback simply wasn't an issue.
The instrument mics were used on toms and even ride cymbal for the first two acts, who had smaller drum kits. The mic's low end-response peaks at around 200 Hz and is down to -10 dB at 80 Hz. The low-cut switch again seemed to be too drastic. It was left flat on the D3500, and some low-end boost added to both mics at the board. With EQ, these mics sounded very good on toms. Adjectives included punchy, natural, neutral and clear. They also worked fine for ride cymbal bell tones, although I wouldn't expect them to do as well on a thinner cymbal.
The mics worked well enough at the live gig I was curious to see if they'd thrive in a studio environment. So, the next stop was San Francisco's Brillant Studios for a live jazz recording session. The artists were Jim and Morning Nichols, engineered by Devon Rietveld and produced by Allyn Rosenberg. Again the D3400 and D3500 found their way onto the first and second rack toms. These particular drums were pitched higher that the previously tested kit, and the AKGs were also mixed in with a pair of overhead and a second pair of distant room mics. Perhaps for both reasons, the mics needed no additional low-end EQ, although a modest boost at 2.5 and 8 kHz was used. The mics sounded fine, and were used on all the session's basic tracks.
Finally, I tried the D3400 on trumpet, guitar amp and steel string guitar, cueing over Sony V6 'phones. The trumpet a big winner, jumping out nicely with extra punch and sparkle. The guitar amp was also fine, although the difference between the D3400 and an SM57 was not as apparent on this particular amp. The D3400 also sounded good on steel-string acoustic guitar, although the mic's 200 Hz bump tended to over-emphasize the guitar's own resonance in that band (nothing a little EQ couldn't fix). Another solution was to use the D3500 and engage the low-cut switch. With some below-200 Hz boost, I was able to get a nice bright (but not brittle) guitar tone. It might not be the warmest mic for a solo guitar, but it should be excellent for cutting an acoustic above a full band.
Overall the mics performed very well. My only complaint would be the low-cut switch on the vocal mic--it does seem a little drastic. But, that's what I though about the switch on the D3500 until I tried it on guitar. In my opinion, AKG's got a winner. I suspect that the Tri-Power line will eventually become as well-used as the company's other fine instruments.
Deanne Franklin: "On the vocal mic, I didn't use the low-end roll off because it starts too high. I liked the high-boost--it gave a lot of cut and presence, and I could pull out the frequencies that I didn't like. I took out 2.5 kHz in the house and 1.6 kHz, 2 kHz and 2.5 kHz in the monitor mix. It had great vocal presence without feedback. Gary (Sister Double Happiness' singer) said the vocals sounded great--he had a good time. Also, many of the smaller capsule/windscreen mics don't have enough space to keep the capsule from getting saturated with spit. Then, the vocal tone gets worse and worse throughout the night. That didn't happen tonight.
"As far as the drum mics are concerned, we didn't need the switch to roll of any more of the bottom end from those microphones. I had to add a lot more bottom to them, although I didn't mind that--they sounded good. I didn't have to add the high-end that I normally do on these drums. They cut through very nicely--I even rolled out some at 2.5 kHz. I'd like to try those instrument mics on congas--they might sound real good."
Chris Kathman: "I could hear a lot of warmth off the vocal mic that I would not hear off a Shure mic. It had the breathy 100, 200, 300 Hz--and it was stable. The other vocal mics we used were OK, but they didn't make my ears perk up like the lead vocal (D3900) did.
"The drum mics sounded pretty neutral to me--it did not sound that different from the Beta 57. I feel that if I bought a whole set of those mics, I could take them into any situation and make the drums sound like I wanted them too, but without sounding artificial. They were workable, colorless, good mics."
Devon Rietveld: "One of the things we were after with this [studio] date was to get a real live jazz feel. Immediately, these mics worked for me. I found them crisp, punchy, clean and natural. I did add a little top, but the bottom end was fine. Remember that the room we were in supported the bottom-end on the drums, and that we were using them in combination with overheads and room mics."
"I'd say they were more similar to a 421 than a 57. I would definately try them on a heavy guitar amp, like a Marshall that was up really loud, and stick the mic off the amp a few feet. It sounds like they can take a lot of level, so I'd also try putting it right up on the cabinet. I'd probably try them on a lot of things I'd use dynamic microphones on."