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Single Mic Technique?

Discussion in 'Live Sound [BG]' started by G Aichele, Feb 5, 2018.


  1. 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.
     
    lowplaces likes this.
  2. Wasnex

    Wasnex

    Dec 25, 2011
    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.
     
    lowplaces and G Aichele like this.
  3. I have only very limited EQ options, and no way to apply an LPF, but I will apply an HPF. And I'll continue experimenting with mic placement in our test recordings before we try this approach (if ever) in a gig. Thanks for the suggestions!
     
  4. saabfender

    saabfender Banned SUSPENDED

    Jan 10, 2018
    Indianapolis
    I’d recommend a compromise to the one-mic technique for bluegrass. Try running a couple end-address condensers (or even SM57s) on a stereo bar in ORTF. That paints a listener-realistic stereo image that will amplify pretty well and record excellently with a minimum amount of mics, player mic technique or sound-man involvement.
     
  5. Wasnex

    Wasnex

    Dec 25, 2011
    I would agree with a near coincident pair if the OP is running stereo mains. ORTF may cause some comb filtering if running mono...XY is a bit more mono compatible. I would not hard pan the mics to full L/R as this is likely to create an unnaturally wide stereo image with a hole in the middle.
     
    Last edited: Feb 10, 2018
    Ulf_Hansson likes this.
  6. Wasnex

    Wasnex

    Dec 25, 2011
    Use whatever tools and techniques you have. Even simple tone controls on a channel strip are useful to some degree. If you are using a small digital mixer, many have extended EQ filters built into the operating system.

    In addition to experimenting with recordings, it would be useful to try the technique out in an acoustic space where you can hook up your mains. I would expect single mic technique to be very challenging in the typical house.
     
  7. Thanks again! My very limited supply of tools includes a small ~analog~ mixer (Yamaha MG06) and a single PA speaker for the mic (the rest of the band). Crown XLS 1000 amp. Strictly mono! I wish we had a better practice space, but it is a house -- although the semi-open floor plan means that the space is not terrifically small. OTOH, if we can pull off playing there without feedback, I'll take that as a good sign. (Next practice is Thursday. With speaker.)
     
  8. I have a small sound company and have also become the defacto sound guy in the bands I play in. I have also tried to limit the amount of sound gear I have haul to a gig. I have had mixed results with condenser mics. The use of a large diaphram mic has been a problem if the band members cannot do the "bluegrass dance" around the single mic. One of the bands (bluegrass) I play in has members who must sit when they play because of physical problems. I have had success using two small diaphram condenser mics with that group. The mics can be set up closer to the players, so two players share a mic. I think the room size has a significant affect on the success of using condenser mics. On a recent job I used a large diaphram mic in a long narrow room. The band was set up along one long wall, making the distance between the band and the audience either quite close to the band if in the middle of the room or quite far away when they were on either end of the room. This arrangement just didn't work. Couldn't get the mic far enough from the band to get good coverage without putting it in the middle of the audience. The next time we play this room we will each have a vocal dynamic mic and plug instruments into the PA.

    Thump on,

    One_Dude
     
    saabfender likes this.
  9. Progress report:

    I did a couple of tests this past week using the mic with the PA speaker attached to that channel and I'm pretty sure that feedback will not be an issue. The mic is set to cardioid and there's an 80 Hz HPF. The three acoustic musicians sit (we're all old; we sit) in a half-circle with the clarinet at 9 o'clock and the guitar and mandolin at 12 and 2 respectively. This does a surprisingly good job of balancing the respective volumes. I listened to them through the speaker and also made several test recordings to confirm the results. So I'm feeling pretty good about this technique and looking forward to gigging (next week) using it.

    FWIW, we play mainly jazz from the 30s and 40s, and rock from the 50s and 60s.
     
    Wasnex likes this.
  10. At our gig last night, the system seemed to work quite well. Medium sized room with approx. 100-150 people in it. No feedback issues, and initial sound tests went well. People danced and seemed to enjoy the music, and no one complained! :)

    We have another gig next week, and I hope we'll have some people there who will give an honest critique of the quality of the sound.
     
    waveman and Wasnex like this.
  11. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    Modern bluegrass approach. 2 large diaphragm condensers. Plus a small diaphragm condenser at waist height on the left hand stand. The mic to the right is the soloist mic. Goes up or down depending on what instrument is soloing and if the soloist is also singing. The Left side stays up for vocal support. Guitarist is the main led singer. The sdc on that stand is mostly there for his dreadnaught.

    Theses guys constantly ‘work’ the mics by moving in or out... side to side. they are amazing.

    Mic’s are ear trumpet LDC’s and Neumann km-105 sdc. Mic on the bass is another Ear Trumpet.

    Pic 1, the right hand LDC is down for the mando.
    Pic 2, it is up for the violin.
    3B1EEACE-10A5-46A7-A15E-887BBFF520B9. 45091CD1-E382-4305-9DA9-8C48856843F9. FA9475E4-116C-4E98-83DE-87B4E26AF4DE. 58D8012F-4669-4637-B975-F2B024A03E1A.
     
    Last edited: Feb 24, 2018
    squarewave likes this.
  12. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    if you do hope the condenser route on stage, you want a mic that has a strong positive side and a strong negative / null on the rear...
     
  13. tshapiro

    tshapiro Gold Supporting Member Supporting Member

    Aug 25, 2015
    Jax Florida
    Not so much a micing solution, but from a process standpoint, I make it everyone’s responsibility to plug themselves into the mixing board. I mix from there. I do this so I don’t have the total burden of setup. While others may not understand sound systems and mixing they can certainly setup their own mic and plug it into the board. It’s a protocol I’ve had in all the different bands I’ve played in for many years and it works great. I also have them pack and bring everything related to them: their mic, cords, stands, etc. This works particularly good for singers who don’t like to lift a finger :)
     
    G Aichele and JRA like this.
  14. JRA

    JRA my words = opinion Supporting Member

    G Aichele : great idea all the way around --- and i'm glad it's working for you! :thumbsup:
     
  15. We tried the technique at a second gig last night. Again there were no feedback issues, but we did have a bit of a problem getting the clarinet into the mix. She's placed the furthest from the mic because the instrument is so much louder than the others, but if she turned to face the audience (90 degrees away from the front of the mic) her sound nearly disappeared. This was "solved" at the time by having her turn to face the mic, but I'm not sure that's a totally adequate solution for future live performances.
     
  16. I did sound this summer at an outdoor concert for a 5 piece folk type bluegrass band. They insisted on the bass going direct and all other guitars, banjo, voices and fiddle go through one very hot ribbon mike. They would then step in and out as their parts needed.

    It was a nightmare. They had a feedback unit and all I could do was try to feather one volume fader and the bass. The audience was not amused, and I got a lot of looks but hey, I have two fades.
     
  17. Wasnex

    Wasnex

    Dec 25, 2011
    You did mention that you had the clarinet positioned at 9 o'clock. This is significantly off axis for a cardioid mic. If you have the clarinet move back and to the center it should pop up in the mix nicely. Might seem counter intuitive because the distance is greater, but being more in the primary pickup pattern of the mic will offset this. Old positions 9,12,2. I am assuming the mic is pointed at the guitarist. Perhaps 9:30,12,2 would work better, or 10,12,2.

    You could also aim the mic slightly toward the clarinet and have the guitar and mandolin shift (audience) left accordingly. Perhaps 9,11:30,1:30 would work better. Mic is still aimed at the guitarist. Also assuming the single speaker is audience right for max feedback rejection.

    Use whichever solution provides the best audio visual compromise. I wouldn't worry if the clarinet is not facing straight off stage. Facing in the general direction of the audience should be fine.

    Each gig will likely be a bit different. Do a sound check and put down a few pieces of tape to mark everyone's position if needed.

    You could always consider using more mics. Placement and aiming for isolation is key to avoiding comb filtering with your mono signal. I suggest you Google "microphone 3 to 1 rule"
     
  18. I do know about the 3 to 1 rule and am seriously considering using more mics, but that puts the mixing burden more on me. Nevertheless, so far everyone in the band has been very cooperative with my experiment. Thanks especially to Wasnex for the post above re band member placement. I read somewhere that 90 degrees off-axis with a cardioid effectively doubles the distance from the mic, but there's so much info on the WWW about mic placement and it's not always consistent!

    BTW, a big problem with the clock metaphor is that it implies that the mic is equidistant from the performers. But if I "squeeze the clock" and move the mic closer to guitarist (but keep still same distance and relative direction to the others), what does that do? That's kind of where I am right now, playing with that.
     
  19. Wasnex

    Wasnex

    Dec 25, 2011
    If the mic is aimed at and moved closer to the guitarist, the guitarist will become louder in the mic. As the other instruments move out of the mics primary pickup pattern, but remain equidistant from it, they will become softer and their sound will typically darken. The the spec sheet for the mic you listed doesn't display a detailed multi-frequency polar plot. Typically the pickup pattern is narrower for high frequencies. This is part of the reason I think having the clarinet and mandolin slightly off axis is desirable. The clarinet in particular can be very abrasive sounding in a mic. It should be noted that not all mics sound good off axis.

    Something to keep in mind is what happens when you get the mic really close to the source. At some distance with most cardioid mics, the bass response will begin to increase. This is proximity effect. The other point to keep in mind is the way sound emanates from an instrument. The clarinet will radiate sound from the mouth piece, keys, and bell. The balance of the sound will shift along the length of the instrument as different notes are played. If you get too close, the 3 to 1 rule implies you will hear primarily the part of the instrument that is closest to the mic rather than a full balance sound of the entire instrument. This is also true of guitar and mandolin. The sound hole, neck, and different places of the body produce different sounds. If the guitar is too dark, aim the mic at a part of the instrument that produces a brighter sound.


    It sounds like you understand the necessary principles and just need to experiment some more. Keep in mind the 3 to 1 rule is an oversimplification. The key point is if you have two sound sources producing the same SPL in two mics you will get phasing unless both sound sources are equidistant from each mic. Obviously this is impractical. The phasing can be addressed with aiming and distance. The idea is for each mic to only pickup it's intended source and to significantly reject all others.

    As an experiment, hold the mic in your hand and listen with headphones. Hum, speak, or sing as you move the mic around changing distance and how it is aimed at your mouth. Note the difference between speaking straight into the mic, and speaking into the mic at 90 degrees and 180 degrees of axis. Hold the mic next to your chest aimed up at the bottom of you mouth and notice how the sound changes as you move the mic up towards your mouth. Hold the mic at arms length and notice how the sound changes as you move the mic to your mouth and to your chest. This experiment should give you a more intuitive understanding of how to vary mic placement for the desired results.
     
    Last edited: Mar 5, 2018
    G Aichele likes this.
  20. Another gig coming up (Friday) and I'm not sure whether to put the clarinet on a separate mic (dynamic, cardioid) or not. Main reasons against: more to setup/takedown, and mainly more mixing for me! Main reasons for: better control over her volume and "place in the mix." Plus it make things a bit less congested around the other mic.

    I welcome your opinions.
     

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