Like some other bass players, I'm also the sound guy for our band. The others help out, but perhaps since they're all acoustic musicians (clarinet, mandolin, guitar/singer -- no drums) they have less interest in the electronic stuff, and since I already have some idea of things like impedance and gain vs. volume, it fell to me. Which is OK, but live mixing has always been a burden I could do without.
So lately I've been thinking about the "single mic technique." One large-diaphragm condenser mic used by everyone (but me). Still popular among bluegrass and folk groups, and small ensembles, but once (before stereo, before music became largely electronic) it was not usual for many types of music.
I've been experimenting recently with recordings of our practices using such a mic (AT2050), and I really like the results. I send out the recordings to the band, and this forces everyone to listen to each other (both during practice and again with the recording) and share together in mixing as they play. I'd still have to do some mixing during a performance, since the bass signal will go to a bass speaker and the mic signal will go to a PA speaker, but that's still much less work for me than the one close mic/performer custom. And less gear for us all to hump! Most of the venues where we perform are fairly small and quiet (no bars or loud celebrations, and rarely outdoors). The acoustics are not always good and there is rarely a stage, but our 2 speakers are generally more than enough.
I suppose most of you don't play in bands like mine, but perhaps some of you do. In either case, I'm thinking of using this technique for our next few gigs, and I'd appreciate your thoughts about such a technique, pro or con.
I haven't done a 1 mic technique, but I have a lot of experience with area mic'ing large ensembles for sound reinforcement. IMHO close mic'ing is best for higher volume and feedback resistance, but area mic'ing tends to sound more natural.
Using 1 mic should work fine as long as you don't expect or need much volume. You need to work out the height of the mic necessary to balance the vocals and instruments and you need to work out the distances that each player should be from the mic for solo vs ensemble work. Clarinet is way louder than mandolin or guitar and will likely need to be further from the mic to maintain balance. You need to figure out the optics and acoustics so everyone, including the clarinet, looks like they are part of the ensemble and can step up to solo.
Another thing to be mindful of is speaker placement in relation to the mic. Ideally you want the sound from the speakers and sound from the instruments to reach the audience simultaneously. If the two sound sources do not arrive simultaneously they will cancel instead of summing. This will reduce apparent volume, degrade sound quality, and destroy the illusion of an acoustic ensemble. To work out the distance, measure from audience to the speakers and then place the mic so it is the same distance from the audience as the speakers. Basically the prime listening location should be equidistant to each speaker and the mic.
The ideal spread between the speakers is a compromise. Wider will typically reduce the tendency for feedback, but too wide will destroy the image of an acoustic ensemble because people will hear only the sound source they are closest too.
Consider applying a low pass filter LPF and high pass filter HPF to the mic. The filters will help increase clarity and reduce feedback so you can increase volume a bit. The low E string on the guitar is around 82hz. Start with the HPF around 80hz and increase the frequency until it starts thinning the sound. Thinning the sound a little is desirable, so listen to the entire ensemble and make a judgment on what sounds best. Ultimately you will probably end up with HPF between 150 and 250 hz depending upon if you singers are male or female. If you have the ability to low pass, start with the LPF around 15Khz. Reduce the LPF until you notice the sound dulling a bit and then raise the frequency just a touch.
If you have graphic or parametric EQ, you may also benefit from ringing the system out. This is done at your risk, so a word of caution when ringing the system. You want to avoid prolonged or loud feedback as you can quickly damage speakers and ears. Others should be asked to leave the room and you should wear hearing protection. Keep one hand on your master volume and increase gain on the equalizer band slowly. When you hear feedback starting, reduce gain as quickly as you can.
If you have a 31 band graphic, 1) turn the system up till it is on the verge of feeding back. Try to remember the most prominent feedback tones. 2) Reduce the gain so the system is stable. 3) Slowly raise two adjacent sliders on the graphic EQ at a time and return them to 0db. 4) Note which bands are most prone to feedback, and dial them back. Often the same frequency will feedback between three adjacent bands. When possible only cut the one band that is closest to the feedback frequency. When you only need to cut one band you can cut deeper; -12db is usually fine. If you have to cut two or more adjacent band, often it is better to not cut as deep so consider -3 to -9db, depending upon how many adjacent bands must be cut. Let your ears be your guide and don't be afraid to cut two adjacent bands 12db if it sounds better.
If you have a parametric EQ, complete step 1) and 2) in the preceding paragraph. 3) Set the Q or bandwidth of one filter to medium. 4). Boost the band about 3 db and slowly sweep across the frequency spectrum, noting which frequencies feedback. 5) Go back to the worst frequencies. 6) Increase the gain slowly till the feedback begins to develop. 7) Simultaneously narrow the bandwidth to its narrowest setting and adjust the frequency until you find the exact frequency of the feedback. 7) Dip the band at the feedback frequency and slightly increase the bandwidth. You don't want to leave the filter at its narrowest setting because the exact feedback frequency will change throughout the night. You typically reach the point of diminishing returns after you eliminate the 4 or 5 frequencies that are most feedback prone. If you get a bunch of adjacent frequencies feeding back, broaden the bandwidth of the filter and use less of a cut.
After you finish ringing the system, slowly increase your master volume to see where your new feedback limits are. Dial the master volume back at least 6-10 db if you can, so that you have a bit of feedback resistant headroom. If you can't get sufficient volume with 6-10db of feedback resistant headroom, use close mic'ing technique as required.
