Thursday, May 2, 2013

The Audio-Technica High Sensitivity AT 4080 Ribbon Mic



Two Audio-Technica AT4080 in Blumlein
Ribbon microphones have been in service since the 1930s. RCA mics like the 44B and 77DX are now considered vintage. You can spend $1200 to $1500 or more for one. The trick is finding one in good shape because the original ribbons are relatively delicate. Not because of age. That’s just the way they were originally designed. Or, you can try a new Audio-Technica AT 4080 bi-directional (figure of eight), dual ribbon mic that streets for about $999. Seven years in the making, it boasts a 150dB SPL level and the sensitivity of a studio condenser.

Why bother with a ribbon? Well, for one thing, it sounds fundamentally different than dynamic or condenser mics. That’s why recording engineers have continued to use ribbon mics all along. Ribbon mics use a different principle of physics to capture sound than dynamic and condenser mics. Ribbons are rectangular strips of metal, usually aluminum, in a magnetic field. 


Signal flow is a direct result of the induction that occurs as the ribbon moves in the magnetic field. In dynamic and condenser mics, a round diaphragm is used. In dynamic mics, the diaphragm is attached to a coil suspended in a magnetic field. In a condenser mic, the diaphragm is one half of a capacitor. Instead of a magnetic field, the signal is generated by the varying voltage caused the diaphragm moving closer to and further from the other half of the capacitor.

The ribbon element in a ribbon mic has to have unique properties to sound good and be durable. Audio-Technica’s ribbon material is, “pure aluminum from a famous plating company.” That’s all AT would say. The other “magic” in a ribbon is the way in which it is crimped; a process by which the ribbon is shaped and imprinted with a textured pattern, so it holds its shape over time. Audio-Technica has a patent-pending MicroLinear ribbon imprint, which they believe results in a more durable ribbon with better resistance to lateral flexing. The AT 4080 comes with a 5-year warranty on both the mic and the ribbon. Not something you’d want to offer with a vintage mic. Plosive protection, always an issue with ribbons, is achieved with an ultrafine metallic mesh placed over the ribbon so as to be as acoustically invisible as possible.

Early ribbon mics, even the higher sensitivity 77DX, were still relatively low in sensitivity, requiring a lot of preamp gain and accompanying hiss. Audio-Technica solved that problem by using stronger magnets, longer, dual ribbons and a small, low noise amplifier on board the mic. What this works out to, for practical purposes is that the AT4080 is about 20 dB more sensitive than an ElectroVoice RE27 N/D. In fact it’s about 2 dB more sensitive than an AKG C414 B-ULS condenser mic in figure of eight pattern. So forget anything you thought about ribbon mics not having enough sensitivity. The onboard amp uses Phantom Power, so, if you’re old school enough to have learned not to run Phantom Power on ribbon mics, you’ll have to change your ways. 

The Audio Technica AT 4080 has a published frequency response of 20 Hz -18 kHz. Like most ribbon mics, it doesn’t have a presence peak, so it doesn’t sound as bright as a condenser mic. With few exceptions, e.g. the beyerdynamic M500, ribbon mics don’t have a lot going on above 10 kHz. The AT 4080 is down about -3 dB between 5 kHz and 10 kHz, but pops back up to 0 dB by 13 kHz before slowly fading away. The capsule, frequently called “the motor” in a ribbon mic, is well isolated from the body.

IN USE
After recording a voice track, I used a high pass filter at 30 Hz with an 18 dB/oct slope and a parametric EQ set fairly wide at 125 Hz and pulled down 6 dB. With that adjustment, the AT 4080 flattened out nicely. With further EQ adjustment, I was able to make the top end shine some; at least as much as a good dynamic mic. I think that in addition to working well on my baritone narrator voice, the AT 4080 would also smooth out edgy, unpleasant voices. The 150 SPL rating also makes it a good choice for the loudest screaming voices I can imagine.

Do you want one in your TV studio? That depends on what you want to record or broadcast and the acoustics of your space. Like most ribbon mics, the AT4080 is a bi-directional figure of eight. It picks up sound from the front and back (0 and 180 degrees), but very little at 90 degrees off axis. If you have two people in the same room and need to mic them both, theoretically, you could put them on the front and back sides of this mic and record both voices with one mic. They would have to have equally loud voices and be the same distance from the mic and close enough so as not to hear much of the room itself. If the two people had unequally loud voices, you could position the quieter voice closer, but now were entering that area of recording where things get iffy. If one voice required EQ and the other one didn’t, you’re stuck.

If you have a small booth with a large plate glass window behind the mic, although the nulls of the sides of the figure of eight are quite deep and effective, the backside of the figure of eight will pickup the bounce from the window, or any hard, reflective surface. If you turn the mic 90 degrees so that one of the nulls is aimed at the reflective surface, you’ll reduce the “roominess”, assuming that the back is not aimed at another hard surface.

If your facility uses a lot of compression and limiting to increase relative loudness, you may be aware that dynamics processors generate gritty distortion artifacts, especially when using relatively brighter condenser microphones with more aggressive presence peaks. The harder you hit the processing, the nastier it sounds. The Audio-Technica AT4080 should keep the sound from getting edgy as quickly.

If you record or broadcast music, a ribbon mic comes in very handy. It’s directionality is a very useful tool on a music sound stage; almost like a free isolation booth. With a little practice, you can capture one instrument nicely and position the mic to put another instrument in one of the mic’s two nulls to avoid picking up that instrument. Ribbon mics are frequent choices for horns, strings, banjos, accordions and edgy electric guitar amps because their softer high frequency response takes the edge off of those instruments. They can also do well as drum overheads if the space has been designed properly.

With two AT4080 ribbon mics, you can experiment with Blumlein Recording. Noted electronics engineer Alan Blumlein applied for a UK patent in 1931, describing the use of two figure of eight mics positioned coincidentally on the vertical axis (one directly over the other) and with each mic’s lobes positioned in the nulls of the other mic. So, as viewed from above, instead of a mono figure of eight, you get a stereo clover. Sound sources are usually placed at or in between the front lobes. Experimentation with four or more sources in a circle that surround the Blumlein Pair, in a proper acoustical environment, have yielded some exceptional recordings, some that yield a sort of  surround sound.

JOSHING WITH JOSH

Shown here are Josh Polak on mandola, Rabbi Shuviel Ma'aravi on guitar, Esther Polak on woodwind and Mike Abramov on hand drums. Shuviel's guitar and Mike's drums were holding down the center of the stereo spectrum with Josh's mandola and Esther's woodwind to the left and right, respectively. I started by positioning Shuviel and Mike at 0 and 180 and got the volume balance by having them move toward or away from the mics. I had to move Josh and Esther around a bit to  balance the loudness of their instruments and get them to the right places on the stereo spectrum, but playing in a circle allows for optimum musician eye contact which normally translates into better performances. To hear a short section of what we recorded, follow this link to my SoundCloud account.

MIKE, DAVE AND VAN
Next in were Mike White, Dave Mattheiss and Van Ertel with a Mike White original. To get the mix right using only the two AT4080 mics, I had to position everyone exactly where I wanted them for level and pan. I'm a one room operation, so I need accurate headphones. My choice are the Audio Technica ATH-M50.  

I started by putting Mike, who was singing and playing, between the front lobes of the two mics, at Zero Degrees. Van's pedal steel amp speaker is on the Black & Decker WorkMate centered between the back lobes at 180 degrees. Dave Mattheiss, with the white hat, we moved around until we got his guitar in the right spot. Because Mike's guitar body is slightly right of center, I put Dave to the left so his guitar would be on the other side of the stereo spectrum. We "mixed" levels by moving toward or away from the mics. We did a Mike White original tune called "Living Will." Here's a link to it. To get a better look, click on the pictures. 

BANG A GONG
Then, Yoga Master Joe Roberson came in with his amazing gongs. Gongs can be very challenging to record without distortion. The sound field generated by a gong is very complex and can easily modulate the diaphragm or ribbon element of a mic, causing unpleasant distortion, even though the record level is well below zero. 

At a foot away, even at low playing volumes, I was getting breakup. I reset and backed off to about 18 inches to 2 feet. Because these AT4080 ribbons are as sensitive as a studio condenser mic, I only needed to use 35 dB of gain from my GML preamps to get a good level into Pro Tools.

Here's a track we recorded. As you listen to the piece Joe performed for me, note the dynamic range; how quiet the space is and how little circuit noise and hiss you hear from the mics at low level and how that sound builds as Joe wakes up one of his gongs. That's a measure of the low self noise of the AT4080. As I mentioned earlier, Audio Technica's effort to increase ribbon length, increase magnet flux and add a small Phantom Powered amp chip to each mic really make a difference. Audio Technica also figured out how to capture more high frequencies with their ribbon.

JAN SEIDEN - FLUTE
It occurred to me that if the gong can be fragile and overpowering, the flute, with its seemingly simple sound is actually rather complex. Internationally known flautist Jan Seiden lives nearby (Baltimore is a very cool town). I asked what she could bring to the AT4080 party and she arrives will all flags flying.

After listening to three of her dozen flutes, I chose a double chamber, double octave, E minor, native american style flute made by Dana Ross at Falcon Flutes. Jan played "Highland Heather" one of her original pieces which you may have heard on her Memory Of Time CD.

As you can see from the picture, this is no ordinary flute. As you will hear by clicking on this link on my SoundCloud site, it can produce multiple tones simultaneously.

Jan stood at the zero degree point, between the two front lobes of the AT4080 mics. After setting a level based on the volume of her playing I hit RECORD and we were done in one take. I did use a bit of EQ and several stereo reverbs for this 24-bit, 44.1 kHz recording, but no limiting or compression.

MADRIGALS
I've worked with madrigal singers Larksong for over 15 years. We have recorded at least three CDs and usually go to St. John's Episcopal Church on the west side of Baltimore where one of the member attends church. Getting six, and now seven singers around these mics while they weave their lines for this sort of recording created some challenges. We had to play around a lot with placement, who stood where, to get them all on the proper place on the stereo spectrum because with Blumlein, there is no postproduction/mixing panning of individual sounds. Attention to the relative volume of each performer is also extremely necessary. If you're too loud, you have to remember to sing softer or step back some.

After a few numbers, it became clear to me that I needed to put the baritone and bass voices at zero and 180 degrees. I also put the only alto there. Then I flanked them with the tenors and finally put the sopranos on the outside edges.

This picture shows the six person arrangement with alto, Martha, to the right at zero degrees and Dave, bass baritone to the left at 180 degrees. Sopranos Andrea and Janet flank Martha and are facing the front lobes of each microphone. Tenors Drew and Jim are facing the rear lobes of each microphone. When I added Kevin, I had him behind Martha at zero degrees.

On this piece, "April Is In My Mistress' Face", you can hear the blending and weaving as each vocal part comes and goes. I've added a little reverb and some minor gain reduction.

Come back again as I add recordings of other instruments to this blog post. Contact me about them at tyford@tyford.com.

SUMMARY

When a company like Audio-Technica spends seven years developing a mic to get it right, you can expect good performance for your investment. While you can use the AT 4080 for VO work after some EQ and in a properly designed booth, it can also be used for a variety of other applications as described above. It’s a worthy addition to your mic locker because it’s sturdier, more sensitive and has more high frequency response than vintage ribbon mics. 

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Fast Facts

Application: Studio recording
Key Features: Sturdy, high sensitivity figure of eight ribbon mic
Price: $1245 with suspension mount.

Contact:
Audio-Technica U.S., Inc. 
1221 Commerce Drive 
Stow, Ohio 44224 
Tel: 330-686-2600