Re: [Sursound] Rode Soundfield NT-SF1

[Fons Adriaensen]

On Sat, Apr 14, 2018 at 11:49:07AM +0100, Chris Woolf wrote:

> I'd be very interested to know the argument behind that.
> 
> Although bass response is affected by size in speakers I don't know of any
> reason for that in microphones.

This has little to do with response, and all with directivity.

It's perfectly possible to have a tiny mic with excellent bass
response. But it's quite difficult to maintain directivity
as size goes down. Also self-noise will be worse for small
capsules - they just get less acoustic energy.

If the capsules don't provide directivity, then it has to
be obtained by amplifying the differences between capsule
outputs. The required gain (for first order) is proportional
to the ratio wavelenght / capsule distance, so it will be
higher as frequency and/or mic size go down.
There are practical limits to what can be done this way,
and that more or less imposes a minimum practical size.

Ciao,

-- 
FA


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Re: [Sursound] Rode Soundfield NT-SF1

[Chris Woolf]

I'd be very interested to know the argument behind that.

Although bass response is affected by size in speakers I don't know of 
any reason for that in microphones.


Chris Woolf


On 13/04/2018 18:58, Fernando Lopez-Lezcano wrote:

On 04/13/2018 10:23 AM, Jack Reynolds wrote:

That’s what I thought.
I have also heard that a radius smaller than 15mm or so has 
detrimental effects on the low end


The is probably related to the size of the capsules. As you bring the 
radius down you have to use smaller capsules and the low frequency 
response will suffer (for example, I can see a big difference in low 
end response between microphones I have built using 10mm capsules - 
array radius of 9.2mm - vs. 14mm capsules - array radius 11mm, but 
that is because of the capsules themselves).


-- Fernando

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Re: [Sursound] Rode Soundfield NT-SF1

[Fernando Lopez-Lezcano]

On 04/13/2018 10:23 AM, Jack Reynolds wrote:

That’s what I thought.
I have also heard that a radius smaller than 15mm or so has detrimental effects 
on the low end


The is probably related to the size of the capsules. As you bring the 
radius down you have to use smaller capsules and the low frequency 
response will suffer (for example, I can see a big difference in low end 
response between microphones I have built using 10mm capsules - array 
radius of 9.2mm - vs. 14mm capsules - array radius 11mm, but that is 
because of the capsules themselves).


-- Fernando

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Re: [Sursound] Rode Soundfield NT-SF1

[Jack Reynolds]

That’s what I thought.
I have also heard that a radius smaller than 15mm or so has detrimental effects 
on the low end
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Re: [Sursound] Rode Soundfield NT-SF1

[Fernando Lopez-Lezcano]

On 04/12/2018 03:33 PM, Jack Reynolds wrote:

So is a larger radius A-Format mic not a problem then? I always thought the 
radius dictated the upper frequency limit for spatial aliasing.


The radius defines the frequency at which the array stops behaving like 
a coincident array. Above that frequency filters are normally used to 
try to compensate for that, but they cannot equalize the array equally 
well in all directions. A smaller array will be better in the sense that 
those problems will happen at higher frequencies.


-- Fernando

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Re: [Sursound] Rode Soundfield NT-SF1

[Jack Reynolds]

So is a larger radius A-Format mic not a problem then? I always thought the 
radius dictated the upper frequency limit for spatial aliasing.  
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Re: [Sursound] Rode Soundfield NT-SF1

[Fons Adriaensen]

On Thu, Apr 12, 2018 at 10:12:48AM +0100, Paul Hodges wrote:
> --On 12 April 2018 09:36 +0100 Jack Reynolds
>  wrote:
> 
> > There is an optimum radius of about 15mm, below which the bottom end
> > begins to suffer I'm told. 
> 
> I would guess this is practical rather than theoretical; determined by
> a combination of noise (because of the gain required in the
> differences) and the difficulty of precise calibration at low
> frequencies.

The radius would matter if omni capsules are used. In that case
the practical lower limit if you want the 1st order response to
go down to the 20-50 Hz range is around the size of the Eigenmic,
somwat more than 15 mm radius. And even then that requires very
careful calibration and stability.

Tetrahedral mics use near cardioid capsules, and extracting the
first order AMB components doesn't require a minimum distance
between them.

Ciao,

-- 
FA

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Re: [Sursound] Rode Soundfield NT-SF1

[Chris Woolf]

On 11/04/2018 18:40, Paul Hodges wrote:

...
I wonder how the capsules will compare with those on the SPS-200, given
that the projected cost is a mere fraction of that (if the price quoted
in the video is in Australian dollars, then it's only a quarter of the
price of the SPS-200!).


While I have been sceptical in the past about Rode products I have to 
admit that many of their more recent ones have been remarkably good for 
the price. The company's willingness to commit to a lot of capital 
expenditure in automating manufacture, on the presumption of being able 
to sell high volumes, has made low cost manufacture possible. They seem 
able to compete with Far East pricing, yet maintain Western engineering 
values - a scary feat.


They've also bought Peter Schillebeeckx with the Soundfield remnants, so 
they do have some proper expertise too.


Only time will tell if the product really works, but it can't be 
dismissed out of hand now.


Chris Woolf


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Re: [Sursound] Rode Soundfield NT-SF1

[Paul Hodges]

--On 12 April 2018 09:36 +0100 Jack Reynolds
 wrote:

> There is an optimum radius of about 15mm, below which the bottom end
> begins to suffer I'm told. 

I would guess this is practical rather than theoretical; determined by
a combination of noise (because of the gain required in the
differences) and the difficulty of precise calibration at low
frequencies.

Paul

-- 
Paul Hodges

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Re: [Sursound] Rode Soundfield NT-SF1

[Jack Reynolds]

There is an optimum radius of about 15mm, below which the bottom end begins to 
suffer I’m told. 
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Re: [Sursound] Rode Soundfield NT-SF1

[Paul Hodges]

--On 11 April 2018 10:26 + "Courville, Daniel"
 wrote:

> http://www.rode.com/nt-sf1

Given the amount of space they've left behind the capsules, it seems a
shame they didn't take the opportunity to mount them closer.  Perhaps
the space is crucial to the performance of the capsules.

I wonder how the capsules will compare with those on the SPS-200, given
that the projected cost is a mere fraction of that (if the price quoted
in the video is in Australian dollars, then it's only a quarter of the
price of the SPS-200!).

Paul

-- 
Paul Hodges

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Re: [Sursound] Rode Soundfield NT-SF1

[Dave Hunt]

Hi,

Also this, a sound field microphone to mount on top of a camera:

http://www.rode.com/blog/all/videomic-soundfield-abdi

Seems like a short while ago that it was on their website looking more like a 
forthcoming product. 

https://www.gear4music.com/PA-DJ-and-Lighting/Rode-VideoMic-SoundField/1U73

Described as "Coming Soon". I did see a video, but it seems to have disappeared.

It looks like they may have dropped this concept for the time being. Presumably 
they had problems with the housing being near the capsules and quite large. As 
shown, it would have the body of the mic in the down position, so perhaps not 
too much of a problem.


It looked like an extension of 

http://www.rode.com/microphones/stereovideomicx

with similar mounting, controls, and windshields, and (as I remember) sensible 
headphone monitoring.

I have one of these, and have been impressed.

An unusual looking microphone, but quality and very practical. 

Then, there's this

http://www.rode.com/news/new-rode-i16-offers-360-surround-recording-for-ios-devices

Ciao,

Dave Hunt


On 11 Apr 2018, at 17:00, sursound-requ...@music.vt.edu wrote:

> From: "Courville, Daniel" 
> Subject: [Sursound] Rode Soundfield NT-SF1
> Date: 11 April 2018 11:26:00 BST
> To: Sursound 
> 
> 
> This should be interesting...
> 
> http://www.rode.com/nt-sf1
> 
> https://vimeo.com/264158943
> 
> 

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