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NT-SF1

Postby Dave B » Mon Nov 26, 2018 10:23 am

I read the review of the NT-SF1 yesterday and it intrigues me for a couple of reasons. Obviously, the first thing that strikes you is that you can now have an ambisonic system for the shockingly low price of 1000 pounds. I'm guessing that there are going to be a lot more location recordings done in the next few years, which is great. But, other than a truly excellent 'ambient' mic in decent venues, I'm struggling a bit to see where else this kind of approach would be applicable. Would you really use one as a drum overhead? Is that not overkill?

Or am I missing something about the power/flexibility of the system?

The other thing that struck me was an innocuous comment about needing either digital or stepped gain controls. This seems obvious to maintain the correct phase relationships, but does this not present a problem finding portable recorders? I would have guessed that most of the more affordable ones still use analogue controls or am I out of date again?

I suppose that even if you have to blow a grand on a 4channel portable, the combined price of mic and recorder would still be a fraction of what it would cost even a few years ago...
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Re: NT-SF1

Postby Sam Inglis » Mon Nov 26, 2018 10:56 am

Dave B wrote:But, other than a truly excellent 'ambient' mic in decent venues, I'm struggling a bit to see where else this kind of approach would be applicable. Would you really use one as a drum overhead? Is that not overkill?

There's a tendency to think that just because Soundfield mics can be used to record in surround, that is their only or main function. That's not the case at all really. For me, the beauty of the system is that it gives you an incredibly flexible stereo microphone, and moreover, one in which nearly all the flexibility is available after the fact.

To give you an example -- a couple of years ago I was asked to record a recital by students on a music course. The programme featured about ten different ensembles ranging from a guitar trio to a full wind band, taking in a jazz quartet, chamber orchestra and two choirs along the way, with no sound check and minimal turnaround time between each performance. All I was able to do was run onto the stage as each group was setting up, drag my mic to a position that looked vaguely plausible and hope for the best. But because I was using the Soundfield, I was able to adjust the parameters for each individual performance after the fact so as to make sure the stereo recording angle was always appropriate, there was a good balance of direct to ambient sound, etc. From the same mic I was also able to decode a stereo pair pointing backwards to capture the applause between performances.

There was never any intention to record or mix "in surround" but the sheer flexibility of the system made it possible to get a decent recording where I don't think any conventional stereo pair would have succeeded.

And yes it does make a very good drum overhead! This is another context where I quite often find I want to vary the width of the stereo capture at mixdown. And actually, for the price of the NT-SF1, a pair of many of the classic overhead mics would be out of reach, so it could be considered pretty good value for this job.

Dave B wrote:The other thing that struck me was an innocuous comment about needing either digital or stepped gain controls. This seems obvious to maintain the correct phase relationships, but does this not present a problem finding portable recorders? I would have guessed that most of the more affordable ones still use analogue controls or am I out of date again?

It's not an absolute requirement that you have digital or stepped gain controls, but if not, you would need to go through some sort of calibration procedure to make sure that the gain was set identically across all four channels. Which would be a pain and would prevent you from making gain adjustments during the recording.

That said -- given that the NT-SF1's output is pretty hot, I found that in quite a few cases I could just set the mic preamp's gain at its lowest level. The headroom within the converters and DAW will be much greater than the dynamic range of the recorded signal in most real-world situations, so unless you're working with very quiet sources, you don't really lose anything by recording at a low level and boosting after the fact if necessary.
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Re: NT-SF1

Postby Hugh Robjohns » Mon Nov 26, 2018 11:17 am

Dave B wrote:I read the review of the NT-SF1 yesterday and it intrigues me for a couple of reasons. Obviously, the first thing that strikes you is that you can now have an ambisonic system for the shockingly low price of 1000 pounds.

The Core-Sound TetraMic has cost about this for a while, but uses smaller capsules and so is a tad noisier.

I'm guessing that there are going to be a lot more location recordings done in the next few years, which is great.

The impetus is for mainly from Virtual and Augmented Reality (VR/AR) online videos and games.

I'm struggling a bit to see where else this kind of approach would be applicable. Would you really use one as a drum overhead? Is that not overkill?

Is using an Sm7B overkill when an SM58 sits in the cupboard? ;-)

Yes, it's an expensive mic, but it can do things no other conventional mic (or stereo array) can -- as Sam has already highlighted. That post-production capability to completely manipulate the sound character can be a huge benefit. And yes, I have used my own Soundfield mics as drum overheads and they do sound very good!

The other thing that struck me was an innocuous comment about needing either digital or stepped gain controls. This seems obvious to maintain the correct phase relationships, but does this not present a problem finding portable recorders? I would have guessed that most of the more affordable ones still use analogue controls or am I out of date again?

It's a requirement to match gains (rather than phase) from each capsule before the A-B format conversion (which is basically an amplitude matrix), otherwise the virtual polar pattern shapes and angles are all to cock!

But it's less of a problem than it might appear, as many of the latest portable mutli-channel recorders do use digitally-assigned gain controls as the front panel knobs can be allocated to serve as input gain controls or mix faders (or pan controls sometimes, too).

I suppose that even if you have to blow a grand on a 4channel portable, the combined price of mic and recorder would still be a fraction of what it would cost even a few years ago...

Quite so!

My 'vintage' Soundfield SPS422B cost well over £3,000 and my current Soundfield ST450 costs over £5,800... so the Rode NT-SF1 really is a game-changer in bringing all the Soundfield knowledge and experience into a new (more) affordable price point.

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Re: NT-SF1

Postby Mike Stranks » Mon Nov 26, 2018 12:11 pm

Just picking up on Hugh's point on gain controls...

My Zoom F4 has the ability to link the four gain controls in two pairs of two... I use the feature often for stereo pairs. I guess an upgrade (if there isn't one already) to link all four would be fairly simple - and likely given the increased interest in VR now.
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Re: NT-SF1

Postby ef37a » Mon Nov 26, 2018 12:36 pm

Glad this mic came up 'coz I want to ask what I am sure is a stupid question but is just bugging me!

30mV/Pa! Why? I presume Rode could have fixed the sensitivity at any value they liked so is there some deep technical reason why they made it so hot?

The self noise is good but not outstanding so why not a perfectly reasonable (to this old valve jockey) 15mV/Pa and have a 6dB better noise performance? Plus the vast majority of pre amps would not need pads.

Kelvar titfer at the ready. (Oh and mic channel gain setting? Sig genny, DI box and calibrate the buggers!)

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Re: NT-SF1

Postby Dave B » Mon Nov 26, 2018 2:05 pm

Thanks for the replies chaps (and the review in Sam's case) - all good stuff and thought provoking. I guess a number of us will probably splurge on one working on the grounds that it's better to have something like this and not (regularly) use it, than need it and not have it...
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Re: NT-SF1

Postby Wonks » Mon Nov 26, 2018 2:22 pm

As a lot of the planned used will be ambient recordings, with low SPLs at the mic, then I can understand the rather high output levels (but note that it's only a 2mV greater output than a U87 in cardioid mode - and that is generally going to be used a lot closer to a sound source than the Rod - but the U87 does have a pad).

But maybe a pad switch would be a good future addition to make it more versatile.
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Re: NT-SF1

Postby John Willett » Mon Nov 26, 2018 2:58 pm

Dave B wrote:The other thing that struck me was an innocuous comment about needing either digital or stepped gain controls. This seems obvious to maintain the correct phase relationships, but does this not present a problem finding portable recorders? I would have guessed that most of the more affordable ones still use analogue controls or am I out of date again?

The AETA 4MinX has a "soundfield" optioin which gangs all the mic. pre-amps and contrtolls them from a single control. More than £1k, though.

The Røde is about the same as the Soundfield SPS200, by the looks of it, and about 33% cheaper.
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Re: NT-SF1

Postby ef37a » Mon Nov 26, 2018 3:38 pm

Wonks wrote:As a lot of the planned used will be ambient recordings, with low SPLs at the mic, then I can understand the rather high output levels (but note that it's only a 2mV greater output than a U87 in cardioid mode - and that is generally going to be used a lot closer to a sound source than the Rod - but the U87 does have a pad).

But maybe a pad switch would be a good future addition to make it more versatile.

But surely Wonks the mic is going to be used with very good to high end preamps? Even if the output was 5mV/Pa that would be fine and much higher than passive ribbons that are also often used at a distance.

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Re: NT-SF1

Postby Wonks » Mon Nov 26, 2018 3:46 pm

I was think crickets chirping away in the fields etc.

Again, nothing that a 20dB pad on the mic couldn't sort out. Apart from the fact that it doesn't have one.
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Re: NT-SF1

Postby Zukan » Mon Nov 26, 2018 4:10 pm

Great review Sam!

I'd be interested to see if that can be used to capture spaces...mmmm. Certainly would make for some creative and esoteric textures...
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Re: NT-SF1

Postby ef37a » Mon Nov 26, 2018 4:43 pm

"I was think crickets chirping away in the fields etc. "

Well for a long time dynamics were all you could use on wildlife* and most of those are 6dB down on even 5mV!

*I have a pair of pretty rubbish Mapiln (Oh! HOW I miss 'em!) £20 dynamics in my garden being amped up by a Xnx 802 (which has never been off this 4 years!) and it is only really in the dead of night/early morning when there is no wind that the pre amps show up.

I am waiting on a review of one of those SE spook powered amps before I flash my eighty quid!

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Re: NT-SF1

Postby Hugh Robjohns » Mon Nov 26, 2018 4:51 pm

ef37a wrote:30mV/Pa! Why? I presume Rode could have fixed the sensitivity at any value they liked so is there some deep technical reason why they made it so hot?

30mV/Pa is a little higher than the average capacitor mic, but not by a mad amount. There is at least one studio vocal mic that pushes out more than 50mV and that is bonkers!

I think given the intended application -- ambient soundscapes for VR/AR -- and working with modest location recorders, it's a reasonable compromise that will minimise the electronic preamp noise and produce healthy signal levels.

But I agree a pad switch for use on loud sources would have been a wise addition. With a 30mV/Pa sensitivity, a loud source producing 126dB SPL will try and make the mic generate line level (+4dBu)!

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Re: NT-SF1

Postby ConcertinaChap » Mon Nov 26, 2018 6:47 pm

Why do you chaps keep doing this to me! I thought I was very happy with my mic collection. Now suddenly there's a new one to lust after, and worst of all it's not so expensive I could just ignore it, just so expensive I'd really notice the money go.

:(

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Re: NT-SF1

Postby blinddrew » Mon Nov 26, 2018 9:24 pm

Yeah, but think about it CC, when would it be useful for you to be able to capture the complete atmosphere of a live performance in a natural and ambient way with just a single, relatively discreet, microphone?
I mean, it's, it's, it's, kind of exactly what you do really isn't it?
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Re: NT-SF1

Postby Bob Bickerton » Mon Nov 26, 2018 10:50 pm

blinddrew wrote:Yeah, but think about it CC, when would it be useful for you to be able to capture the complete atmosphere of a live performance in a natural and ambient way with just a single, relatively discreet, microphone?
I mean, it's, it's, it's, kind of exactly what you do really isn't it?

Maybe it could be inserted inside his concertina?

Probably shouldn't say this, but I once removed the bellow pins and inserted a jar of peanut butter and a packet of (savoury) biscuits inside a friend's melodeon, before replacing the bellow pins and taking off. I came back some minutes later to find him playing the melodeon but complaining he thought some of the reeds were sticking. Our mirth alerted him to the fact that something more was amiss. Fortunately the burst packet of biscuits didn't seem to do much damage to a melodeon that was well past its use by date, may have even improved things............

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Re: NT-SF1

Postby Wonks » Mon Nov 26, 2018 11:06 pm

blinddrew wrote:Yeah, but think about it CC, when would it be useful for you to be able to capture the complete atmosphere of a live performance in a natural and ambient way with just a single, relatively discreet, microphone?

Well, a discrete collection of four microphones.

But you've still got placement issues for instrument balance. And if the group form a circle around the mic, how do you then create a workable stereo image for normal use (rather than a surround sound one)? You'd have to go mono.
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Re: NT-SF1

Postby ConcertinaChap » Mon Nov 26, 2018 11:30 pm

blinddrew wrote:Yeah, but think about it CC, when would it be useful for you to be able to capture the complete atmosphere of a live performance in a natural and ambient way with just a single, relatively discreet, microphone?
I mean, it's, it's, it's, kind of exactly what you do really isn't it?

Hammer, let me introduce you to nail.

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Re: NT-SF1

Postby Sam Spoons » Tue Nov 27, 2018 12:11 am

Life's tough CC, but, ask yourself this, how good would it be for live miking a concertina?
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Re: NT-SF1

Postby Sam Inglis » Tue Nov 27, 2018 10:02 am

Wonks wrote: if the group form a circle around the mic, how do you then create a workable stereo image for normal use (rather than a surround sound one)? You'd have to go mono.

Not at all! You can decode an Ambisonic mic to a stereo array that has a 360-degree acceptance angle (back to back cardioids). Or you can decode it to multiple spot mics pointing at the individual musicians, and pan those as you like.
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