soundfield mic for stereo application

[Petrus]

New topic, but about SoundField SPS200: How accurately the 4 tracks should be matched in levels as not to create anomalies in the spatial representation? Ideal would be "exactly" of course. I have been using a Maselec preamp with 3 dB steps, and just assumed that a $4000 unit would have all 4 channels pretty well matched. Now I am contemplating getting a Zaxcom Maxx with 4 channel recording option, but it seems that this unit can be calibrated only within 0.5 dB accuracy between channels.

How accurately in levels are the 4 capsules in the SPS200 mic head matched? That might give some idea about the accuracy SoundField thinks is necessary.

[John Willett]

Originally Posted by Petrus

New topic, but about SoundField SPS200: How accurately the 4 tracks should be matched in levels as not to create anomalies in the spatial representation? Ideal would be "exactly" of course. I have been using a Maselec preamp with 3 dB steps, and just assumed that a $4000 unit would have all 4 channels pretty well matched. Now I am contemplating getting a Zaxcom Maxx with 4 channel recording option, but it seems that this unit can be calibrated only within 0.5 dB accuracy between channels.

How accurately in levels are the 4 capsules in the SPS200 mic head matched? That might give some idea about the accuracy SoundField thinks is necessary.

I would send an e-mail to Soundfield and ask them the question direct.

But, I would say, that the Zaxcom is quite a step down from the Nagra VI, AETA 4MinX, Sonosax and Sound Devices units.

Ergonomics and digital implementation on the Zax are great, it just seems to be their analogue technology that lets them down.

[richgilb]

Originally Posted by Petrus

New topic, but about SoundField SPS200: How accurately the 4 tracks should be matched in levels as not to create anomalies in the spatial representation? Ideal would be "exactly" of course. I have been using a Maselec preamp with 3 dB steps, and just assumed that a $4000 unit would have all 4 channels pretty well matched. Now I am contemplating getting a Zaxcom Maxx with 4 channel recording option, but it seems that this unit can be calibrated only within 0.5 dB accuracy between channels.

How accurately in levels are the 4 capsules in the SPS200 mic head matched? That might give some idea about the accuracy SoundField thinks is necessary.

Hi Petrus. They recommend no more than 0.1db tolerance between each channel. I have asked this already. My Focusrite Liquid 4pre does this comfortably. Soundfield have ther own amp called the SMP200, which is not too pricey and you seem to get 15% discount off list quite easily. I am personally looking at Lake People's preamp at the moment, and am in the middle of a discussion with them about this very issue. Soundfield seem to give amps with digital switches a thumbs up but I don't know why, not being an electronics expert. I know they champion the MOTU Traveller for a budget solution, which is digitally controlled.

[leddy]

If you are worried, just could put a test tone on the front end of the audio that you can use to calibrate the channels in post.

[John Willett]

Originally Posted by richgilb

Hi Petrus. They recommend no more than 0.1db tolerance between each channel. I have asked this already. My Focusrite Liquid 4pre does this comfortably. Soundfield have ther own amp called the SMP200, which is not too pricey.

I use the Nagra VI which has well matched amps on a single control that is ideal for the SPS200.

The next firmware update for the Nagra will include A-format / B-format monitoring for the Soundfield mic. It has been Beta tested by a member of this forum (not me) who has given Nagra the , so I expect it next month.

I am pretty sure that the AETA 4MinX also included monitoring for the SPS200 as well.

[richgilb]

Originally Posted by John Willett

I use the Nagra VI which has well matched amps on a single control that is ideal for the SPS200.

The next firmware update for the Nagra will include A-format / B-format monitoring for the Soundfield mic. It has been Beta tested by a member of this forum (not me) who has given Nagra the , so I expect it next month.

I am pretty sure that the AETA 4MinX also included monitoring for the SPS200 as well.

Liquid 4pre also has digital single gain control option for all 4 preamps

[G Gilliam]

Originally Posted by John Willett

I use the Nagra VI which has well matched amps on a single control that is ideal for the SPS200.

The next firmware update for the Nagra will include A-format / B-format monitoring for the Soundfield mic. It has been Beta tested by a member of this forum (not me) who has given Nagra the , so I expect it next month.

I am pretty sure that the AETA 4MinX also included monitoring for the SPS200 as well.

The Sound Devices 744T includes a monitoring mode for the four B-format files you can record from a SoundField controller. B-format monitoring is selected from the headphone output Setup Menu option. When listening to the SoundField microphone, the 744T’s B-format monitor builds a stereo mix using the W, X, and Y signals.

[John Willett]

Originally Posted by G Gilliam

The Sound Devices 744T includes a monitoring mode for the four B-format files you can record from a SoundField controller. B-format monitoring is selected from the headphone output Setup Menu option. When listening to the SoundField microphone, the 744T’s B-format monitor builds a stereo mix using the W, X, and Y signals.

That's good news - but I think the Nagra VI and 4MinX can also convert the A-format signal from the SPS200 which I don't think the 788T can do yet.

[David Spearritt]

Originally Posted by John Willett

That's good news - but I think the Nagra VI and 4MinX can also convert the A-format signal from the SPS200 which I don't think the 788T can do yet.

Correct. The new NVI firmware will accept A or B format as inputs and output three options of MS stereo, ie with a cardioid, supercardioid or fig8 mid. The last one of course equivalent to pure Blumlein. I have tested them all on SPS200 recordings and the mic itself and it is fantastic, especially with those three options.
Finally a recorder where you can monitor soundfield simply and get the mic in the right location without having to cart along a soundfield processor.

[Plush]

Huge UP's to David Spearritt and Nig-Nog for this.

Nagra listens to and then performs for customers.

thankyasomuch!

[Lucas_G]

Hello fellow SPS200 owners,

I have had very little time to investigate further into the SPS200 problems.

I did receive my SPS200 back from Coresound together with the calibration files, but I am still checking things which I want to discuss with Len before giving any final comments on the calibration.

I will also have to ask Pieter at Soundfield as to any progess he has made.

There is just one thing I want to mention here, because it can mean a lot to fellow users:

THE SPS200 INVERTS PHASE

That is important to know...

Normally a mic preserves absolute phase, but this mic does NOT.

Is it important? Some people think that it is of no consequence, and with a sinus wave or a long held tone we will not hear any difference. However, with a sudden sound (for instance from a percussive instrument) it can be detected by our ears as an unnatural thing, as several tests have shown.

Now there are many cd-players, dacs and speakers that do not respect abolute phase, and many listeners do not bother (although they could remedy it by inverting polarity at their speakers).

For one reason it can however be EXTREMELY important to know that your SPS200 inverts phase: if you mix the outcome of your SPS200 with other mics you MUST invert phase in your DAW.

In Reaper this can be easily done by clickling with the right mousebutton on each track of your four raw capsule streams, and selecting ITEM PROPERTIES. There you can select INVERT PHASE. Do this for all four raw tracks.

Of course, it would be also nice to have this option available within Surroundzone, so I will suggest this too.

When I have more news on the calibration within VVMic or on the progress that Soundfield themselves are making, I willl give you an update.

I do have some recording material available, but I want to share it after all questions have been answered.

[John Willett]

Originally Posted by Lucas_G

THE SPS200 INVERTS PHASE

Have you discussed this with Soundfield?

It could be a mis-wired cable?

It is also easily fixed by swapping pins 2 and 3 in the SPS200's XLR connectors - as it has a special cable it's not such a big issue as with other mics.

[Lucas_G]

Originally Posted by John Willett

Have you discussed this with Soundfield?

It could be a mis-wired cable?

It is also easily fixed by swapping pins 2 and 3 in the SPS200's XLR connectors - as it has a special cable it's not such a big issue as with other mics.

Hi John,

I very recently discoverd it. Right after posting it here on the forum, I have also sent an email to Soundfield, so let's wait what they have to say...

I just use their standard cable that comes with the SPS200. Soldering could remedy this, but I think it is a rather cumbersome solution. In that case I would rather have it reversed in the DAW or within the plugin.

Best wishes,

Lucas

[LenMinNJ]

Originally Posted by richgilb

Liquid 4pre also has digital single gain control option for all 4 preamps

And so does the very capable and low cost Tascam DR-680 recorder. Channel gains can be ganged in user-defined ways.

We hear good things too about the MOTU 4Pre.

[Lucas_G]

Originally Posted by LenMinNJ

And so does the very capable and low cost Tascam DR-680 recorder. Channel gains can be ganged in user-defined ways.

We hear good things too about the MOTU 4Pre.

Yes, I have two Tascam DR-680 recorders and they perform well. They also work fine in cascade mode giving one 12 or 14 channels.

However, it is good to check the inputlevels with a cabletester that can output a testtone on mic-level. In one Tascam for instance there was nearly 2 dB difference among channels, and that is a bit too much for an ambisonic recording. You can easily correct this in you DAW, but first you will have to know how much one should correct for each channel. Those cabletesters are relatively cheap, and they also come in handy for.... cabletesting!

[ricardo_lee]

Originally Posted by Lucas_G

THE SPS200 INVERTS PHASE

Lucas pointed me to this thread.

I'm afraid I'm the guilty party as I did the Mk3b & Mk4 Soundfields for Calrec. These invert phase and this has been carried through the Mk5 and also ST250 & SP422. Dunno about ST350 & 450.

My excuse was trying not to pass the signal through yet another evil OPA.

Mea culpa, mea culpa, mea maxima culpa!

But hello to Daniel & Prof Farina. I endorse everything Angelo says except, like Guru Fons, I think all FIRs evil while Angelo thinks all IIRs evil

I've been designing IIRs & FIRs nearly as long as Fons though I hesitate to place myself on the same sentence.

On a more serious note, one reason why SurroundZone may not sound as good as other plugins is their use of evil FIRs

[Lucas_G]

Hi Ricardo,

Thanks for your honest reply. (Soundfield still keeps quiet...).

I can see your thought on avoiding yet another opamp stage.

It would however have been better to mention this in the manual, because I think noone would ever expect it to happen. And it is absolutely vital information when you mix the Soundfield with other setups (I will always mix the Soundfield with a non coincident setup like an AB or ORTF...).

In fact I only discovered it when I did my usual test of clapping my hands after the recording was done, in order to be able to timealign later the various mics within the DAW. I saw a reversed impulse....

What do you think of Jonh's suggestion to exchange pins at the soundfield cable?

Best wishes,

Lucas

P.S. would love to hear more from you regarding the Coresound measurements...

[Lucas_G]

Originally Posted by ricardo_lee

On a more serious note, one reason why SurroundZone may not sound as good as other plugins is their use of evil FIRs

Ricardo, on a real serious note, the reason why Surroundzone sounds so bad is the resulting frequency response when used with the SPS200. There is a 10 dB boost at 7 kHz and a much too thin lower mid region. Whether FIR or IRR, this will always sound like %@#$#

[John Willett]

Originally Posted by Lucas_G

Hi Ricardo,

Thanks for your honest reply. (Soundfield still keeps quiet...).

Probably because Ken Giles sold Soundfield to TSL in September and the factory is in the middle of being moved down south to Marlow in Buckinghamshire.

[David Spearritt]

Excuse me for being thick but what have op amps and iir or fir filters got to do with raw a format capsule outputs into a plugin reversing the phase?

[Lucas_G]

Originally Posted by John Willett

Probably because Ken Giles sold Soundfield to TSL in September and the factory is in the middle of being moved down south to Marlow in Buckinghamshire.

Should we worry then....

[Lucas_G]

Originally Posted by David Spearritt

Excuse me for being thick but what have op amps and iir or fir filters got to do with raw a format capsule outputs into a plugin reversing the phase?

Hi David,

None of the plugins reverses phase (but in this case it should! ).

The reverse is happening in the electronics built in the shaft of the mic.

It could have been corrected by adding again another opamp stage at the output of the electronics of the mic, but Ricardo choose not to do so...

[John Willett]

Originally Posted by Lucas_G

Hi David,

None of the plugins reverses phase (but in this case it should! ).

The reverse is happening in the electronics built in the shaft of the mic.

It could have been corrected by adding again another opamp stage at the output of the electronics of the mic, but Ricardo choose not to do so...

But couldn't it all have easily been sorted by the wiring of the output XLRs?

[David Spearritt]

Originally Posted by John Willett

But couldn't it all have easily been sorted by the wiring of the output XLRs?

My point exactly. We are talking raw A-Format mic signals coming out of this thing. All other mic manufs seem to manage to get the phase correct coming out of their mic bodies.

[Lucas_G]

Originally Posted by David Spearritt

My point exactly. We are talking raw A-Format mic signals coming out of this thing. All other mic manufs seem to manage to get the phase correct coming out of their mic bodies.

Yes, that would have been a valid option, of course.

Apparently noone was aware of it (except Ricardo).

What strikes me is that in the world of ENG all these things seem to be irrelevant, and Soundfield has been looking almost exclusively at that sector, it appears.

People like Tony Faulkner and other sound engineers therefore don't like to work with Soundfield mics. I just hope we can change this. If Soundfield could get themselves devoted to soundquality (vital in that world), I am sure they would in the end be able to get a foothold in the world of acoustical recordings like classical and jazz.

What they need, it seems to me, is people from that world that can test their equipment from a to z in the real practice of music recording, so that their products will live up to the expectations there. Or am I wrong? What do fellow GS members think on this subject?

Personally I begin to like the SPS200, now that I find remedies for the flaws. As an addition to other setups it really gives you a lot to adjust in the aftermath of the recording. It can function as a kind of saveguard... I do not regret that I bought it, and that I put a lot of effort in it.

[boojum]

Originally Posted by Lucas_G

Personally I begin to like the SPS200, now that I find remedies for the flaws. As an addition to other setups it really gives you a lot to adjust in the aftermath of the recording. It can function as a kind of saveguard... I do not regret that I bought it, and that I put a lot of effort in it.

I understand completely how you feel but the end-user should not be depended upon to trouble-shoot and fix failures in concept and manufacture which are kept secret. What planet are these guys on?

[ricardo_lee]

Originally Posted by Lucas_G

.. plugins reverses phase (but in this case it should! ). ... It could have been corrected by adding again another opamp stage at the output of the electronics of the mic, but Ricardo choose not to do so...

The reasons for this are long, involved and mainly historical going back to the first prototypes. I had a chance to bite the bullet and correct things with the Mk4 but didn't.

You'll find the stereo outputs are in proper phase but not the B-format on the Mk4. Having said that, SPS200 is A-format out and should be in correct phase. ie each output should be like a normal mike.

And there's no excuse for not correcting it in Surround Zone as it costs nothing in $$ or sound quality.

I should also add there are some famous name Germans with similar historical discrepancies but I think, this millenium, they all follow AES/ITU

[David Spearritt]

Originally Posted by ricardo_lee

Having said that, SPS200 is A-format out and should be in correct phase. ie each output should be like a normal mike.

So let me get this straight. Can we please restrict the discussion to the SPS200 for the moment. Is the phase of the raw mic signals out the end of the SPS200 correct in absolute phase?

And there's no excuse for not correcting it in Surround Zone as it costs nothing in $$ or sound quality.

And you are saying the SurroundZone plugin reverses the phase????

[ricardo_lee]

Originally Posted by David Spearritt

So let me get this straight. Can we please restrict the discussion to the SPS200 for the moment. Is the phase of the raw mic signals out the end of the SPS200 correct in absolute phase?

And you are saying the SurroundZone plugin reverses the phase????

.. over to Lukas and those who have actual grubby hands on da beast..

[JEGG]

Originally Posted by Lucas_G

People like Tony Faulkner and other sound engineers therefore don't like to work with Soundfield mics.

I can't at all speak for Tony, but I'm not sure he's a fan of coincident mic'ing in general.