The Advanced Audio CM251 and CM67se are both large diaphragm tube condenser mics. They come with nine polar pattern power supplies, shock mounts, multi-pin XLR cables, foam windscreens, and a nice case to hold each mic system. On the case handle hardware there is a small label letting you know which mic is inside. I immediately thought this was a very nice touch and showed forethought.
If you are not familiar with what Advanced Audio does, their mics are not meant to be exact clones but meant to be influenced by and based on classics models. This approach allows for cost-effective production as well as tweaking the system for modern performance.
For reference, the CM251 is based on the sonics and design of the classic Telefunken ELA M 251 whereas the CM67se is based around the Neumann U 67. These mics command a fairly high price on the vintage market, and are often out of reach to most of us working in the trenches of the audio world.
I was interested in the CM251 partly due to my love for records produced by Mitchell Froom. He has a vintage ELA M 251 that I've listened to on records by Richard Thompson, Los Lobos, Suzanne Vega, and many other others. Advanced Audio's CM251 does not disappoint. It is clear and pleasing, with a never-harsh rise in the top that helps things poke through a mix without sounding strident in any way. The low end is solid, while the mids are slightly subdued.
The CM67se definitely has what one expects from classic Neumann mics. A thick and pleasing low midrange presence that just sounds like a record. Like my Neumann U 87, my Gefell CMV563, and the Neumann U 47 I've had experience with, the tone sounds a little odd in solo but sits in the track beautifully.
I was able to start using the mics in testing situations before having them on client sessions. I had singer/songwriter Sara Quah come to the studio to do some acoustic guitar and vocal experiments. I set both mics in figure-8 and placed them where the guitar null was toward the vocal and vice versa. We recorded the same song with each mic in each position. On guitar the CM251 really emphasized the pick attack and the shimmer of the guitar. While I expected the mic to not suit her voice as Sara often sings in her higher register, I was surprised how much I liked the CM67se. The CM67se was present and pleasing on her voice and brought out some of her chest tone. When I switched the mics and recorded the same song a second time, I was again impressed on how each sounded. The CM67se on guitar (a Gibson J-15) brought more of the woody sound out. The CM251 put a nice brilliance and polish on her voice that was quite different than the CM67.
My next test were drum overheads. I set both mics up as close to each other as possible in addition to bass drum and snare drum mics. I had the Advanced Audio mics' polar pattern set to what I'd call wide cardioid – one click past the standard cardioid marking on the PSU. I played my house Gretsch drum set with Zildjian (mostly vintage) cymbals for this test. I just hit record and played for a while at various tempos, dynamic levels, and styles. This was another example of how different these mics are. The high-end rise of the CM251 did lovely things to cymbal articulation. I can see how a pair would also be lovely. The snare spoke nicely, and the attack of the toms was great. The slightly soft midrange of the mic didn't bring out a lot of the tom's tone, however. I don't think that is an issue if you were using tom mics in a rock, pop, soul, or R&B project. I also assume that higher pitched jazz toms would speak beautifully through the CM251; I just didn't have time to swap drum sets out to see.
The CM67se gave me more of a full picture of the drum set. Cymbals didn't have quite the shimmer of the CM251, but still sounded very pleasing. The snare was present and had a lot of smack. Toms sounded much fuller and present due to the low mid bump in the mic. Again, I believe a pair over a drum set or in a Glyn Johns setup [Tape Op#109] would sound great on a number of projects.
Next up were some client sessions where I tried to utilize both mics whenever possible. I had started a single with Sara Quah called "Make Me Yours." I was adding parts after we'd recorded basics and the first attempt of the lead vocal. I had added a sampled Mellotron and moved on to electric guitar. I was playing an Ibanez Artist through a Vox AC15 and had both mics on the amp's 12-inch speaker, about an inch from the center dust cap and maybe two inches off the grill cloth. Both mics handled pick attack and tonal variations nicely. I was playing in the control room while listening through my studio monitors and was able to adjust my playing to slightly drive the amp on certain sections or back off during the lighter verses. Making adjustments by ear, I found myself using more gain on the CM251 to match the presence of the CM67. The differences in midrange color and presence give the illusion of the CM251 sounding softer when the meters match. I ended up using both mics, hard panned in the final mix.
Later that week, keyboardist Mike Gardner came in to add Hammond organ to the track. I thought I'd have some fun and set the mics up as a mid/side pair on the Leslie speaker. The mid (cardioid) was the CM67se and the side (figure-8) was the CM251. This combination and sound was nothing short of glorious, even as Mike just played chords while I set levels and listened. The sheer meatiness of the CM67se alone would be perfect in many situations recording the Hammond and Leslie combination. The CM251 as a side mic added beautiful width and sparkle. On the mix, I rode the side mic channels to spread and narrow the sound to great effect. I don't believe I touched the EQ.
Later, when Sara and I decided we didn't have the lead vocal we wanted for the song, I thought I might get a more interesting take by having her play acoustic guitar while singing the lead. Referencing the test recordings mentioned above, I decided to use the CM67se on guitar and the CM251 on vocal with both mics in the figure-8 position. Both sounds worked well with the production, and the deep nulls of the figure-8 pattern left me enough room for mix placement. I was able to compress and ride the vocal and use effects without messing with the present guitar sound.
I had an interesting session for a local composer, Chad Tallon, who'd done a modern version of The Jungle Book for an amusement park in Thailand. He needed the lead character's songs done before he went to Chicago to record the rest of the cast. His student, 15-year old Adrian Mendez, was singing the part. She has a very modern pop/Broadway type voice. I had both Advanced Audio mics set up in the booth to audition. It was pretty clear that the CM67se was not the mic for her voice, but the CM251 was perfect. The high-end rise and quick articulation of the edge terminated CK12 capsule reacted exactly as you would want to hear for her style of singing.
I continued this setup of both mics in the vocal booth on several projects. With Chinese rapper (rapping mostly in Mandarin Chinese) Ricardo, I liked the chunkier tone of the CM67se and used the CM251 for adlibs. Upon sending him the mix he asked to hear the other mic on the lead. He preferred the CM251. I believe it has to do with how the hard consonants of the language sounded on each of the mics that brought him to that decision. I used both mics, panned hard and effected for the chorus vocal.
On a session where two different singers (Jeff Walker and Aaron Hinkle) sang the same song, there was a clear case of one mic sounding great and the other sounding totally wrong, and when the singers switched, so did the mic. The singer with a nasal upper midrange buildup sounded great on the CM251 and not so great on the CM67se while the other singer, with more of a classic rock high tenor sound, was perfect with the CM67se but harsh and piercing on the CM251. On a different session a female singer (Stevi Z) sounded wonderful through each of these mics and would have been ridiculously happy with either. She liked the CM67se because of the way it complemented the lower register of her voice. For background vocals on that same song (sung by Sara Quah) I used the CM67se on the low parts and the CM251 on the high harmonies.
Cutting percussion for the above Stevi Z song, "Best Friends Don't Drink Alone," I set up both mics in omni in the live room. I was also playing the parts, so I just tracked each instrument: an egg shaker, a caxixi, and a tambourine to two tracks each. For the mix, the egg shaker and caxixi (a Brazilian basket shaker with a hard leather bottom) both sounded better with the CM251, but the tambourine was perfect with the CM67se.
I really like both of these microphones and am sad that I need to pack them up and send them back to Canada. I do feel like I should point out a couple of minor negatives. The included shock mounts, though quite sturdy, have the tightening screws in awkward spots and are a bit of a hassle to adjust. New shock mounts from Advanced Audio will include a wing-nut screw, which should address some of the problem. I had to re-glue the felt on one of mounts, but they do hold the mics quite securely and I didn't have a single issue with mechanical noise. The mic bodies are heavy and robust, and I would like to see that carried through to the power supplies – there is a bit of flex in the XLR panel which makes latching the cable a bit of a fight, but newer units will include an updated 7-pin connector for better fitting. These are minor issues that are being addressed in future production runs, so they shouldn't dissuade anyone from using these fantastic sounding microphones.