Re: [Sursound] Ambisonic Mic Comparison

[Richard Lee]

There's a number of issues brought up in this thread which Core Sound have 
been aware of for some time and have been attempting to address.  But its 
difficult for a small company to make major changes on the small turnover.

For what its worth, the 'new' PPAc will give around 1dB improvement in 
perceived S/N regardless of your favourite weighting (more if you are not 
using a Metric Halo or similar).  This has been achieved mainly by a bit 
more than 1dB more output. 8>D

The MOTU Traveler has near SOTA noise performance but the design is flawed 
and they often become very noisy over time.  If you have one which has been 
OK for more than 12 mths, you are probably OK

I'm on my 3rd Traveler.  The 2nd one developed the noise almost exactly 12 
mths after I received it.  As the 1st took 3 mths to be 'repaired', those 
of us in Oz are not happy bunnies.  (The Traveler is actually Angelo 
Farina's who kindly lent it to Cooktown Recording and Ambisonic 
Productions.)

Its pretty obvious MOTU don't have in-house design expertise and they deny 
there is a problem.  I've not looked inside a MOTU 4pre ... but so far, 
those we know of haven't developed this problem so it has our cautious 
recommendation.

In terms of noise with TetraMic, I'd expect a 'good' Traveler to be on par 
with Sound Devices and Metric Halo (sadly Mac only) and you would notice 
the noise difference between these and the DR680 which is our 
recommendation for an inexpensive portable device.

My experience is if you are not recording bird song in the Norfolk Broads, 
the noise performance of TetraMic wth the above good preamps is not a 
problem.  There are some excellent recordings on Ambisonia from John 
Leonard & Paul Hodges .. some of which were made in a very quiet studio.

That's not to say we aren't working on even better performance ... 8>D
___

(There are problems with noise on the P48V on early DR680s and Paul Hodges 
has a mod for these on Channels 1-4.  I believe, TASCAM, Europe were 
modifying Mk1 DR680s and the new one has sorted this out.

If you have an old DR680, it is worth doing Paul's mod as it affects some 
mikes, both $$$ & inexpensive.  TetraMic is actually pretty immune to P48V 
noise.)
__

If you have a good A/D without preamps, you can build a 4 channel preamp 
using THAT chips with near SOTA performance.

Bear in mind you need to match THAT 1510s & 1512s for gain.  The internal 
resistors are laser trimmed for CMR but the absolute values differ from 
chip to chip.  Thanks to David Pickett for this tip.

If you prefer to use SSM2019 or TI INA163 chips, use them with the latest 
THAT circuits for more reliable long term performance.  All three are 
capable of excellent performance in the right circuit.

It's the protection scheme that is flawed on the SSM, TI & (very early) 
THAT circuits.  The correct protection is cheapo 1n4004 diodes, preferable 
Glass Passivated 1n4004GP.


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Re: [Sursound] Ambisonic Mic Comparison (& sesquicentennial)

[Michael Dunn]

Ha. I bought the MOTU 2408 many years ago. A versatile box for sure, but 
noticeably bad sound quality. I would never buy anything analog from them again.

 

Funny -- a few years after that purchase, I read a review (in Electronic 
Musician IIRC) of the successor model, and the reviewer barely even mentioned 
the audio performance, sticking mostly to describing all its wonderful patching 
& routing abilities. His audio review consisted of something like: “I recorded 
some synth tracks, and they sounded fine.” Nice.

 

Michael

 

p.s., Canada’s sesquicentennial (150th birthday) is approaching, and I’ve 
written five articles about the Canadian technology scene (& tech history) that 
will appear one-per-day this week. The first is:

 

http://www.edn.com/electronics-blogs/benchtalk/4458540/Happy-150th-Canada--The-Engineers

 

To see the rest as they appear, hang out at:

 

http://www.edn.com/electronics-blogs/4420255/BenchTalk

 

 

There is arguably some surround-sound content in the series ;-)

 

 

 

A Sound on Sound review of the larger box says:

 

"MOTU don't publish any specifications for the 8Pre's analogue 

circuitry, such as frequency response or signal-to-noise ratio. While 

it might be nice to know these things, it could be argued that exact 

figures are almost meaningless to the typical user the 8Pre is aimed 

at. In any case, modern digital electronics design almost always 

ensures that signal-to-noise ratio and bandwidth are no longer the 

key concerns for the performance of an audio interface."

 

 

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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[David Pickett]

At 21:57 26/06/2017, David Pickett wrote:

This whole business of low noise microphones and preamps is in my 
experience a non-issue in the vast majority of cases.


That said, I was upset to discover that MOTU publish no details on 
their website of the 4Pre that can be construed as truly technical.


A Sound on Sound review of the larger box says:

"MOTU don't publish any specifications for the 8Pre's analogue 
circuitry, such as frequency response or signal-to-noise ratio. While 
it might be nice to know these things, it could be argued that exact 
figures are almost meaningless to the typical user the 8Pre is aimed 
at. In any case, modern digital electronics design almost always 
ensures that signal-to-noise ratio and bandwidth are no longer the 
key concerns for the performance of an audio interface."


...

David 


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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[John Leonard]

http://www.johnleonard.co.uk

I look forward to seeing you enter into the market.

Regards,

John

Please note new email address & direct line phone number
email: j...@johnleonard.uk
phone +44 (0)20 3286 5942


> On 26 Jun 2017, at 20:09, Sampo Syreeni  wrote:
> 
> Granted, that. However, I'd still like to challenge you, as a practitioner, a 
> wee bit. What *are* your needs, really? How do you quantify them, precisely?

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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[David Pickett]

This whole business of low noise microphones and preamps is in my 
experience a non-issue in the vast majority of cases. Very few 
environments are quiet enough to be softer than the noise level of 
most microphones. This is true in most cases of recording nature 
sounds and very few recording studios get down below NC 20.  Concert 
halls are even noisier, and we rarely make recordings in anechoic 
chambers, however isolated they may be.


Sampo is right about the ease with which a high quality mic amp can 
be put together, taking reasonable (and obvious) precaution with 
screening, rf suppression and PSU smoothing. I made a simple 
two-channel amp with two THAT1510 ICs in a small box for use with 
ribbon microphones. It can be powered for hours from two PP3 
batteries, and measures and sounds as well as my much more expensive 
RME UFX amplifiers.


David 


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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[Sampo Syreeni]

On 2017-06-26, John Leonard wrote:

Well, of course, the ULN-8 isn’t just a pre-amp: it happens to have 
eight very nice low-noise high-gain mic pre-amps as part of the 
package, that’s all.


Nowadays even the highest of the highest spheres in operational 
amplifier technology costs something like 40 bucks per stereo pair. So, 
with the minimum of high grade passive components included, and adding a 
competitive markup, plus upholstery, it's unlikely you should have to 
pay much in excess of 150 euros for your mic preamp. At that price 
point, it already ought to look good as well as sounding nice.


What I mean to say here is that far too many people price themselves out 
of the game. Analogue preamp engineering is not exactly the kind of 
rocket surgery which calls for thousands of bucks at a pop. Done right, 
using current top of the line components, it certainly makes its demands 
known to your wallet. But when done right, it won't blow the bank.


Compared to the much more stringent and esoteric demands placed on a 
well-designed spatial pickup feeding your preamp, the latter ought to be 
a mere financial byline.


Empirically, based on my own experiences, the two low-cost 
(sub-$1,000.00) multitrack portable recorders that I tried after 
initially purchasing the Tetramic, were noisy at high gain when 
attempting to record quieter sounds with the Tetramic.


Then, regurgitating Fons's words, something is very wrong there. Using 
current chips and just a hint of age old analog engineering knowhow e.g. 
in how to make up a proper gain structure, you can *easily* get into 
stable 18 bit territory for less than a hundred bucks, per four 
channels. Getting past 20, predictably, start to run into diminishing 
returns, true. But then pretty much nobody both has the mic to exercise 
such extreme sensitivity, *while* at the same time running such a 
forbidding absolute amplitude reference as to not be able to gain ride 
any residual noise below the audibility threshold. Pretty much the only 
folks with such stringent demands come from a film sound background, 
with enough bucks from the get go to render the whole point moot.


I found that this was not the case with the ULN-8 and also with the 
Sound Devices 788T. We shall see how the SD Mix-Pre 6 behaves when it 
eventually reaches these shores.


To reiterate, if you can hear any difference between such already rather 
high end devices, somebody, somewhere royally fucked up. Even if my 
understanding of analogue engineering is rather limited, still, given 
the almost unreal performance of today's opamps as a building block, 
even I am fully confident I could design a minimalistic, well-performing 
mic preamp from scratch.


As always, other people may have different experiences, but their 
needs may not be the same as mine.


Granted, that. However, I'd still like to challenge you, as a 
practitioner, a wee bit. What *are* your needs, really? How do you 
quantify them, precisely?


I mean, once we know what you and the other practitioners are *really* 
after, I'd contend that even a half-baked theoretician such as myself 
could readily give rise to some rather magical sounding things. The kind 
of bang for buck which is entirely two or three decades beyond what an 
audiophile purveyor would have you believe is possible.

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[John Leonard]

Well, of course, the ULN-8 isn’t just a pre-amp: it happens to have eight very 
nice low-noise high-gain mic pre-amps  as part of the package, that’s all. 
Also, rather obviously, I didn’t buy the Tetramic and then the ULN-8. The ULN-8 
has been at the centre of my studio set-up for many years and has proved to be 
well worth the money.

Empirically, based on my own experiences, the two low-cost (sub-$1,000.00) 
multitrack portable recorders that I tried after initially purchasing the 
Tetramic, were noisy at high gain when attempting to record quieter sounds with 
the Tetramic. I found that this was not the case with the ULN-8 and also with 
the Sound Devices 788T. We shall see how the SD Mix-Pre 6 behaves when it 
eventually reaches these shores.

As always, other people may have different experiences, but their needs may not 
be the same as mine.

Regards,

John


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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[Augustine Leudar]

I use Zoom H2 and H2N and Motu interfaces (ultralite and 24 ao with
ada8200) the pres are fine - the line/mic in on a zoom h2n ,a little
minijack input,  are quite noisy however - so I usually prefer to use the
onboard mics than an external with this device.

On 26 June 2017 at 15:10, David Pickett <d...@fugato.com> wrote:

> At 14:44 26/06/2017, Steven Boardman wrote:
>
> >I use the Motu 4pre (with a tablet for on the fly decodes), with a
> >Zoom F8 in the field. I also have a RME Fireface in the studio.
> >None have problems with the noise floor being louder than that of the mic.
> >The noise of the Tetramic is only a problem when the subject is quiet
> >or far away. So for most musical applications it’s great. If you are
> >trying to capture wildlife at a distance then there are better options…
>
> Quite so. As I read the article, I didnt have the impression that the
> sources used were all that challenging in terms of loudness. The noise and
> sensitivity spec on the Tetramic is quite satisfactory:
>
> "... Self noise: 19 dBA per capsule. Self noise can decrease or increase
> depending on selected decode
>
> "Maximum SPL per capsule: 135 dB Sensitivity per capsule: 7.0 mV/Pa
> nominal (-43 dB ref: 1V/Pa) ..."
>
> I cannot find comparably detailed specifications for the MOTU 4Pre, but
> the sensitivity demands above are not extreme.
>
> At 14:17 26/06/2017, Sampo Syreeni wrote:
>
> It's been something like a decade since I looked into something like
>> Cirrus Logic or Analog Devices A/D silicon. Then a perfectly good four
>> channel, 16-18 bit equivalent chip cost somewhere in the vicinity of $35. A
>> reference PCB layout for it came free as well. Thus, the idea that you'd
>> now have to expend anything beyond some 100€'s in hardware in order to get
>> a fully functional, top of the line preamp for your top of the line
>> ambisonic mic, seems pretty much preposterous.
>>
>
> Indeed so.  I cant quote prices for the A/D stage, but the one-off price
> of a THAT1512 analog input amplifier costs only EUR 6.82 at Mouser.com, and
> requires only a few additional components.
>
> David
>
>
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-- 
Augustine Leudar
Artistic Director Magik Door LTD
Company Number : NI635217
Registered 63 Ballycoan rd,
Belfast BT88LL
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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[David Pickett]

At 14:44 26/06/2017, Steven Boardman wrote:

>I use the Motu 4pre (with a tablet for on the fly decodes), with a
>Zoom F8 in the field. I also have a RME Fireface in the studio.
>None have problems with the noise floor being louder than that of the mic.
>The noise of the Tetramic is only a problem when the subject is quiet
>or far away. So for most musical applications it’s great. If you are
>trying to capture wildlife at a distance then there are better options…

Quite so. As I read the article, I didnt have the 
impression that the sources used were all that 
challenging in terms of loudness. The noise and 
sensitivity spec on the Tetramic is quite satisfactory:


"... Self noise: 19 dBA per capsule. Self noise 
can decrease or increase depending on selected decode


"Maximum SPL per capsule: 135 dB Sensitivity per 
capsule: 7.0 mV/Pa nominal (-43 dB ref: 1V/Pa) ..."


I cannot find comparably detailed specifications 
for the MOTU 4Pre, but the sensitivity demands above are not extreme.


At 14:17 26/06/2017, Sampo Syreeni wrote:

It's been something like a decade since I looked 
into something like Cirrus Logic or Analog 
Devices A/D silicon. Then a perfectly good four 
channel, 16-18 bit equivalent chip cost 
somewhere in the vicinity of $35. A reference 
PCB layout for it came free as well. Thus, the 
idea that you'd now have to expend anything 
beyond some 100€'s in hardware in order to get a 
fully functional, top of the line preamp for 
your top of the line ambisonic mic, seems pretty much preposterous.


Indeed so.  I cant quote prices for the A/D 
stage, but the one-off price of a THAT1512 analog 
input amplifier costs only EUR 6.82 at 
Mouser.com, and requires only a few additional components.


David

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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[Steven Boardman]

> On 26 Jun 2017, at 12:26, David Pickett <d...@fugato.com> wrote:
> 
> There is something not quite right here.  It seems quite crazy to have to 
> spend over USD 3000 for a preamp/AD convertor to use with a microphone 
> (Tetramic) which is designed to sell for USD 1300 (i.e. much cheaper than the 
> Soundfield).  But I am not convinced that such an expensive preamp is 
> required.  The Tetramic website says: "We've found that a few commercial mic 
> pre/ADCs will do the job. They are the 
> <http://www.motu.com/products/motuaudio/traveler-mk3/ 
> <http://www.motu.com/products/motuaudio/traveler-mk3/>>MOTU Traveler, 
> <http://www.motu.com/products/motuaudio/4pre 
> <http://www.motu.com/products/motuaudio/4pre>>MOTU 4Pre, Metric Halo's 
> <http://www.mhsecure.com/v5mm/ULN-8.html 
> <http://www.mhsecure.com/v5mm/ULN-8.html>>ULN-8, Prism Sound's 
> <http://www.prismsound.com/music_recording/products_subs/orpheus/orpheus_home.php
>  
> <http://www.prismsound.com/music_recording/products_subs/orpheus/orpheus_home.php>>Orpheus,
>  Apogee's <http://www.apogeedigital.com/products/quartet 
> <http://www.apogeedigital.com/products/quartet>>Quartet and 
> <http://www.rme-audio.de/en_products_fireface_ufx.php 
> <http://www.rme-audio.de/en_products_fireface_ufx.php>>RME Fireface UFX."
> 
> I am not a MOTU user, but at USD 449, the MOTU 4Pre presumably has a quite 
> adequate noise specification, or the highly competent Tetramic engineers 
> would not have mentioned it in the same sentence as the more expensive 
> options.
> 
> David

Hi David,

I use the Motu 4pre (with a tablet for on the fly decodes), with a Zoom F8 in 
the field. I also have a RME Fireface in the studio. 
None have problems with the noise floor being louder than that of the mic.
The noise of the Tetramic is only a problem when the subject is quiet or far 
away. So for most musical applications it’s great. If you are trying to capture 
wildlife at a distance then there are better options…

Best

Steve
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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[Sampo Syreeni]

On 2017-06-26, David Pickett wrote:

I am not a MOTU user, but at USD 449, the MOTU 4Pre presumably has a 
quite adequate noise specification, or the highly competent Tetramic 
engineers would not have mentioned it in the same sentence as the more 
expensive options.


Furthermore, on the digital side of things, we can buy somethhing 
equivalent to yesterday's supercomputer for nickel and dime (cf. 
Raspberry PI and its ilk). It doesn't seem quite right that we couldn't 
engineer high quality analogue preamp circuitry towards a similarly low 
price point, especially since the advances in digital circuitry are 
synergistic with analogue designs.


It's been something like a decade since I looked into something like 
Cirrus Logic or Analog Devices A/D silicon. Then a perfectly good four 
channel, 16-18 bit equivalent chip cost somewhere in the vicinity of 
$35. A reference PCB layout for it came free as well. Thus, the idea 
that you'd now have to expend anything beyond some 100€'s in hardware in 
order to get a fully functional, top of the line preamp for your top of 
the line ambisonic mic, seems pretty much preposterous.

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[David Pickett]

At 10:48 26/06/2017, Enda Bates wrote:

>In our test, the mic preamps were quite modest (the MOTU 8m) although
>still fairly representative of the types of mic pres often used with
>these types of mics, hence the issue. So, as John also mentioned, when
>using the TetraMic with modest mic pres (such as a Motu, or a Zoom
>portable recorder), noise can be more of an issue with this mic
>compared to some others, but using better mic pres (such as the Metric
>Halo) much less so. To me this is something important to be aware of.

There is something not quite right here.  It seems quite crazy to 
have to spend over USD 3000 for a preamp/AD convertor to use with a 
microphone (Tetramic) which is designed to sell for USD 1300 (i.e. 
much cheaper than the Soundfield).  But I am not convinced that such 
an expensive preamp is required.  The Tetramic website says: "We've 
found that a few commercial mic pre/ADCs will do the job. They are 
the MOTU 
Traveler, MOTU 4Pre, 
Metric Halo's ULN-8, Prism 
Sound's 
Orpheus, 
Apogee's Quartet and 
RME Fireface UFX."


I am not a MOTU user, but at USD 449, the MOTU 4Pre presumably has a 
quite adequate noise specification, or the highly competent Tetramic 
engineers would not have mentioned it in the same sentence as the 
more expensive options.


David


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[Sursound] Re. Re: Re Re: Ambisonic Mic Comparison

[Enda Bates]

Hi Sampo,
   well the objective directional analysis we're discussing here was not of 
course, but yeah all of the listening tests on audio quality were naturally 
double blind.

In terms of the TetraMic, our experience was that in general the output from 
this mic was a much lower level signal, compared to say the Ambeo. So, my 
original point was not really that the Tetra is noiser, just that it requires 
more input gain compared to some other mics, which places more demands on 
whatever mic preamps are being used. And yes, I'm just referring to program 
level overall noise.

In our test, the mic preamps were quite modest (the MOTU 8m) although still 
fairly representative of the types of mic pres often used with these types of 
mics, hence the issue. So, as John also mentioned, when using the TetraMic with 
modest mic pres (such as a Motu, or a Zoom portable recorder), noise can be 
more of an issue with this mic compared to some others, but using better mic 
pres (such as the Metric Halo) much less so. To me this is something important 
to be aware of.

Steven, although it arrived too late to include in our tests, to my ears, the 
new Ambeo plugin greatly improves the high frequency response, so I'd 
definitely recommend trying it out.

Thanks for the offer Gerard, I'll let you know if we do ever plan on doing more 
tests like this.
enda

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