The shure sm 81s are nice and very flat. I dunno any of the output stats and any of those mics listed, but w a decent preamp like on any basic interface, should have enough power for any of those mics. Is there a particular reason you want omni pickup patterns?

Why are you worrying so much about microphone output (sensitivity)? What type of vocal groups and ensembles are you wanting to record? What pre-amps are you using?

The NT55s come with both cardioid and omni capsules in the box - very handy for swapping between coincident and spaced arrays. You can order omni capsules separately from Rode and fit them to NT5s. However, the NT55 bodies have a useful built-in pad and an HP filter, neither of which the NT5s have.

kmetal is right to mention the Shure SM81s mics to try in this test, but note that in principle they have a fixed cardioid pattern. If you can get hold of the omni capsules for the Shure SM80, I believe these can be fitted to the SM81, although I have never tried this with the SM81s I have.

You are just selecting lateral selections. While all small diaphragm condenser microphones are not the same. They are the same. They're, utilitarian, small diaphragm condenser microphones. And the ones you're looking at? Nothing really to write home about there. For something really special sounding, ya might want to splurge a little bit? How about a Neuman KM 184? They have Omni capsules, which would be the KM 183. I think if ya found a used pair of KM-83/84's, you wouldn't like the noise. Though it never bothered me much. Not when they're plugged into a decent preamp. And no small diaphragm condenser microphone, made today, should be very noisy. Certainly all are quieter than the old venerable Neumann KM 83/84 and the multi-pattern, 86's, that I have. Perfectly wonderful sounding! Noise should not be that big an issue? What are you using?

Unlike the new AKG, 451's, those are a fixed cardioid pattern. They cannot be changed. They're not like the older original 451's, like I have. Those have interchangeable capsules. The newer ones do not.

On vocal ensembles, the hyper cardioid, Beyer M-160's are very very nice sounding. Nice and smooth. No strident, brittle, sound. A reduction in the sibilance. Nice and warm sounding. And along with its M-130, bidirectional ribbon microphone, brethren, they're easy to configure a MS stereo microphone. Which gives you that straight ahead, upfront, middle,solid mono sound and an adjustable stereo width, of your choosing. Hard to beat that combination. You don't need small diaphragm condenser microphones with their wispy crispy sound. I've been hooked on these for over 40 years.

While there are other excellent ribbon microphones out there, some of them are much larger and harder to work with. Such as the old RCA 77 DX's. Heavy suckers! And you don't want to put more than one on any microphone stand. SHURE also has a couple of ribbons but I have issues with those. They feature a different sound on the backside than on the front. And they're not cheap. So if you want a different sound? Why not just buy a different microphone? That made no sense to do. Trying to be all things to everybody. Not.

You might also want to look into the Neumann TLM-107? A new release. Transformer less. Large diaphragm. Multiple patterns. Low noise. High output. Nice. Of course, more money than most of those small diaphragm condenser microphones. But these hold their value. The others don't. They're disposable. And a good bang for the buck nevertheless.

Just a thought?
Mx. Remy Ann David

Thanks for the replies. I'm using an Allen & Heath QU16 digital desk which has decent low noise preamps. Sure not quite Millenia, Hardy etc but still very good. I borrowed a pair of NT5's for a recent classical vocal group and they sounded very good. I worked with two very experienced classical vocal producers on the session and they were both very complimentary about the sound.