I let luthiers figure out how to get the best sound out of my bass and sound engineers figure out how to reproduce the best sound. Professional studio engineers rarely agree. The ones that I have worked with all agree that the f-hole is one of the worst places to mic and upright bass. Put your ear next to the f-hole and have a friend play a little. Notice that the sound that you are hearing is an undeveloped sound? You hear air movement, uneven frequency response and loud boomy lows, and it doesn’t represent the overall sound of the bass because of the lack of definition. This is not the sound that we want if we want our tone amplified accurately. If the flat frequency graph of the AMT mic holds true, then you are just getting a highly accurate reproduction of this undefined sound. This is equivalent to miking the port hole in you speaker cabinet. If you want to add this boominess to the sound from your pickup, (maybe it’s to make up for the lack of low end from a piezo pickup, in your bass or you just like more boominess than what naturally possible from an upright bass), but it doesn’t make sense to spend $700 on a flat frequency response mic to just to boost boominess, nor are you getting a true tone from your bass.
As a young engineer I kept running into bass players who were obsessed with something they called the “f hole”—so compulsive that at first I was afraid to ask what it was. I was relieved to learn that these were merely the two holes in the front of the bass. They are shaped like a cursive letter “f”. These bassists would insist that the very best sound is obtained by placing a mic right up on one of the f holes, and they usually had a preference for one or the other. I quickly learned that the sound coming out at that point is very dark and mushy, much like the sound of some of those pickups.
Once I was older and more experienced I found the courage and diplomatic skill to distract the bassist just long enough to place a large-diaphragm condenser mic directly in front of and about six inches from the strings, with the capsule halfway between the bridge and the bottom end of the fingerboard.
Move your head close to the bridge and you’ll hear a better sound. This is where a large majority of sound engineers prefer to mic and the consider the the sweet spot. I am not going to take credit for placing a condenser mic in that location as part of the amplification system, since it have been done already by some really great bassists, one of the most popular: Dave Holland. For an example, you can listen to his Extended Play: Live at Birdland CD.
This is not to say that the AMT is not a good quality microphone, but my preference is for the AKG. The newer tailpiece mounted model AMT S25b-tp would allow for miking where I’d like to pull sound from, but that mic is not removable for transport and it is too tightly focused to get a wider area of sound around it.
The AKG is not bass specific, nor does it need to be for where it’s located at. Because it is not instrument specific and AKG has the resources and experience to put together a reliable, durable, good sounding mic at a much lower cost (you’re sharing the R&D cost with tens of thousands of other people instead of a couple hundred).
I prefer BassBalsereit pickup because it picks up sound fairly even across the sound spectrum and can be cranked up with a good amount of feedback resistance. What sets the BassBalsereit apart is that you can turn the pickup and dial in the best and most accurate sound from your bass. It is the best pickup on the market based on my personal experience. The AKG mic does a great job of picking up the rich tone and nuances from that sweet spot on the bass. This all works nicely with the P.A. system and/or an accurate amp such as the Acoustic Image line of amps.