Why your "amazing" vocal mic might not be the right tool for the job.
The hallmark of any great live vocal mic is in it's gain before feedback capability and it's directionality - meaning that it is designed to pick up sound clearly right at the tip of the mic, and reject sound entering from the sides and the rear.
People are crazy about BETA's. And I get it. The Beta series mics do sound amazing. They are crystal clear. And on paper; the supercardiod design should be ideal for the stage. But despite the marketing hype, they have terrible rear and side rejection. So unless you are performing with in-ear monitors in a very tightly controlled low stage volume setting with time for a full sound check and ring-out session hours before the gig, these types of mics are not a good investment for the local gigging musician. In other words; don't use it in the clubs unless you want to bludgeon yourself, and your audience with mind splitting feedback.
The great vocal mix you could have gotten will have to be heavily EQ'ed and pushed down in the mix to avoid feeding back until the result is so muddy, muffled and/or low in presence that your audience can't hear the vocals cut through which for most artists completely defeats the purpose of performing their music live.
Someone in the crowd will inevitably complain about the muddiness of the vocal, or it's low position in the mix, and ask that the vocals be "turned up", and thats when things will start to squeal and hum. Or, as is often the case, you'll have a hard time hearing yourself on stage. So you, or one of your bandmates, will ask for more vocals in the monitors, and you'll once again get feedback.
If the venue has one of these old style analog boards with the requisite 3 knob non-parametric EQ, you're in for a world of hurt. Without full parametric control or graphic EQ it's nearly impossible to tailor a live sound for these mics that retains any clarity and doesn't feedback.
Also because Beta's are supercardiod mics, your monitor wedges work better when they're off to the side a bit. So that the sound coming from the wedges hits the back of the mic at the right angle.
So, what mic should I use?
Well, needs vary on the timbre of the voice in question and your own personal tastes. The response curve on vocal microphones vary quite a lot. [The response curve is the EQ naturally inherent in the mic and how it responds to the varying frequencies of your voice.]
The prices on these mics range from $89- $159.
Sennheiser mics have the richest and most responsive EQ profile in the low to mid range price bracket, very clear like a Beta but with much better rejection.
The SM58 has been the industry standard for decades. and it's rejection is just ok. It's characteristically similar to the Beta 58 just not as sensitive. The advantage to having one you can bring to the gig, is that can be EQed with cheap 3 band EQ's, and you almost can't walk into a venue that doesn't already have them, along with a sound mixer that knows exactly how to EQ them. Many will not know how to get the more exotic mics to have clarity without feedback, which can land you back in feedbackville.
Audix may not have the pedigree or brand name recognition of the other two, but I've been consistently surprised by the quality of Audix mics. Their drum mics are an absolute go-to for me on live drums, and in my experience all the OM series mics and especially the OM5's and 7's are rock solid at killing feedback while retaining presence and clarity. Obviously the higher you go up the scale the better the sound quality.
Where we tend to get lost is when comparing the clarity of these mics side-by-side in a solo environment where there is nothing else going on. When we compare the Audix mics to the Shure and Sennheiser mics, they're a bit less clear, and our instinct is to say, "I don't like it, it's muffled." But that is not how we should grade a live vocal mic. Grade it on how well it rejects feedback while still giving you the necessary frequencies to punch through a loud mix. I've been able to EQ Audix OM2's (the low end of the Audix scale) to sound amazingly clear live without feeding back.
My only complaint with the OM2's and OM3's is the popping P's, but you can fix that with a high pass filter and a gentle notch in the low end. The 5's and up don't have this problem and exhibit the same clarity and presence as the Sennheiser's, but with superior rejection. The down side is; you are gonna spend a little more.
The Sennheiser's are a bit better suited for those playing an instrument and singing primarily because the singers aren't always going to be directly dead-on with the center tip of the mic while singing. And the Sennheisers are a little more forgiving in that regard, while the Audix's have a pretty sharp drop-off as you move off axis.
In conclusion; the more you can do in advance to try and ward off feedback, the better your experiences will be. Don't take my word for it. Do your own research. Try different mics. It may mean buying a bunch of them, trying them and selling the ones you don't like online.
If you insist on bringing your own mic to the gig (and I understand all the reasons - bacteria, smell, not knowing if the person who just used it before you spewed their cold germs all over it, etc.) buy yourself a few mics. Get an SM58 for gigs where the barkeep is the sound girl and other dive bar scenarios. Get an OM5, and an e835 or e945 for high end gigs where the mixer has the ability and knowledge to EQ that mic. Have a Beta for when the conditions are right. The point is; to come prepared, and with options. Your own ears and your audience will thank you.
(I only mention low and mid level mics in this piece, as the high end ones really require you have your own sound engineer to shape the curve, a la Ian Beveridge for Dave Grohl and his Sennheiser MD-431 which is a tonally flat mic with the best rejection I've ever seen, and can be shaped to sound like whatever mic you wish, but your mixer needs to have a parametric EQ and the knowledge and experience to get it shaped just right for your voice. It's also not a great off-axis mic so your singer/singers need to have good mic technique discipline. We use these exclusively in my band now, cuz we play really loud in a small rehearsal space, and we got tired of feedback. As a result we now have confidence that, if we can eliminate it in the garage, we have an excellent shot of having crystal clear vocals without feedback in a club where the PA points away from us, and not toward us.)
Above is a level/rejection test of some of the mics I mentioned (along with some crappy mics I found in a drawer) using an earbud blasting pink noise which is placed dead center at the front of each mic up against the grill and then moved gradually to the sides and then to the rear. The big bump near the middle half of the waveform is from the earbud passing over the windscreen ring and the resulting level return which you'll notice in some cases is equal or slightly less than in front of the ring. The Beta failed epically in that it has way too much gain in the rear of the capsule. The Audix OM5, hands down won the rejection test. Also notice the differences in gain. the SM58 is a very low gain mic, whereas the e835 is a very high gain mic. (From top to bottom we have the Sennheiser e835, Audix OM2, Audix OM5, Shure Beta 58A, Shure SM58, Shure SM57, SHure PG58, and a Carvin M68)
My test is based on Dave Rat's mic eval method - Check out his video where he tests a few of the same mics along with the OM7 and shows you how to evaluate your own mics, here.