• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Microphone configuration and soundstage

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Soundstage has been mentioned in another thread, I thought I would bring the discussion here as the useful information is being lost with unfortunate troll noise.

Soundstage is mostly an artificial construct made up from decisions and techniques used by the recording engineer. I would welcome comment from any studio professionals or experienced individuals out there on this. Even when the techniques are boiled down to their simplest levels, stereo pair mics, their positioning can have a clear effect on the perceived soundstage.

Just for fun I am going to record a speech "walkaround" in a few different environments with different mic configurations so people can hear the differences.

Set up is as follows:-

Rode NT5 cardioid matched pair -
http://www.rode.com/microphones/nt5
http://www.soundonsound.com/sos/aug02/articles/rodent4nt5.asp

Seventh Circle Audio T15 Mic pre-amps - https://seventhcircleaudio.com/products/8

Texas Instruments PCM4222EVM ADC - http://www.ti.com/lit/ug/sbau124/sbau124.pdf

Adobe Audition recording at 24 bit 96kHz

The ADC/mic amp is not exactly pretty, it more evolved with a lot of left over bits from the parts bin rather than being designed, however technically it performs very well.

DSC02343 small.jpg


Wiki on sound localisation - https://en.wikipedia.org/wiki/Sound_localization

There are lots of resources on the net regarding stereo mic positioning and techniques, I randomly picked this one to give an idea of the possibilities.

http://ehomerecordingstudio.com/stereo-microphone-techniques/

Mic configurations are as follows
http://cdn1.rode.com/sb20_quickstart.pdf

1. Stereo spaced pair - Probably should be omnis for this, but I dont have them to hand.
DSC02347small SSP.jpg


2. X-Y
DSC02348 small XY.jpg


3. ORTF
DSC02346small ORTF.jpg


The recordings were made in my theatre / listening room which is well damped with an RT60 of around 0.25 in the midrange. All 3 recordings follow the same procedure, speech from 8 points around the room and a 1-24 count walking in a circle around the mics. This is followed by an extract from a track by Bill Morrissey. I will try and get time to record in a different room (far less absorption) and outside in the garden to see if these spaces affect the perceived soundstage.

I have a definite favourite configuration which I think most represents the spatial sound I hear. It will be interesting to see if others agree.

here are the recordings - dont laugh at my accent, I cant help being born and bred in the UK West Country! :)

http://gofile.me/2vnEF/sSiF1iTeL
 
Last edited:

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,524
Likes
37,057
Look in the reference section for a long paper on the matter if Amir decides to leave it there.

The walk around files should be good. If I can find them, I did this for several Mic set ups a couple years ago. Documenting every 15 degrees for the front 180 degrees. Maybe I did not delete them.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Last edited:

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,524
Likes
37,057
Your last sentence is what this is about I believe John. The reason that is useful is because fidelity is important. That you key on other factors being somewhat dismissive of fidelity is interesting.
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,524
Likes
37,057
You mean this "It really wasn't anything to do with how accurate the recording of the sound stage is to the "actual" soundstage one would hear at the live audio event." I'm not sure what you're saying here?

As far as I'm concerned, you really have no idea of the fidelity of ny aspect of the recording (most modern music is studio manufactured) to the actual event so I wouldn't just pick out soundstage in this regard.

I presume you mean by fidelity the accuracy of the playback to what's on the recording? Where are you getting the notion that I am dismissive of this?

If you did the recording you might know what it really was. Or if you use something like the Op is going to generously provide it might help you align your system so that with the right source material your system has fidelity to the real soundstage some recordings have. Once you are at that point, then even artificial recordings have the most accurate portrayal of the artificial soundstage/soundscape.

A companion thread about psycho-acoustic sound design might be great to go with this one. It is a concept mostly used in movies/surround though it applies to stereo music as well. I am limited on time now or I would start one. Anyone interested might wish to google the topic and read up on it. It is surprising you don't hear more about it from audiophiles.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
I understand that you are just quoting from texts without understanding or purpose.

JK, if you have nothing relevant to add to this thread, can I respectfully ask you to bugger off? You may not think of interest or relevance to you, even though its a clear indication of a lack of understanding if thats the case.

So leave the thread alone for others to constructively take part in.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Yep, meaningless subjective waffle.

It cant be realistic, you dont know what the original was like and its a fabrication in any case.

Now please leave the thread.
 

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
Soundstage has been mentioned in another thread, I thought I would bring the discussion here as the useful information is being lost with unfortunate troll noise.

Soundstage is mostly an artificial construct made up from decisions and techniques used by the recording engineer. I would welcome comment from any studio professionals or experienced individuals out there on this. Even when the techniques are boiled down to their simplest levels, stereo pair mics, their positioning can have a clear effect on the perceived soundstage.

Just for fun I am going to record a speech "walkaround" in a few different environments with different mic configurations so people can hear the differences.

Set up is as follows:-

Rode NT5 cardioid matched pair -
http://www.rode.com/microphones/nt5
http://www.soundonsound.com/sos/aug02/articles/rodent4nt5.asp

Seventh Circle Audio T15 Mic pre-amps - https://seventhcircleaudio.com/products/8

Texas Instruments PCM4222EVM ADC - http://www.ti.com/lit/ug/sbau124/sbau124.pdf

Adobe Audition recording at 24 bit 96kHz

The ADC/mic amp is not exactly pretty, it more evolved with a lot of left over bits from the parts bin rather than being designed, however technically it performs very well.

View attachment 833

Wiki on sound localisation - https://en.wikipedia.org/wiki/Sound_localization

There are lots of resources on the net regarding stereo mic positioning and techniques, I randomly picked this one to give an idea of the possibilities.

http://ehomerecordingstudio.com/stereo-microphone-techniques/

Mic configurations are as follows
http://cdn1.rode.com/sb20_quickstart.pdf

1. Stereo spaced pair - Probably should be omnis for this, but I dont have them to hand.
View attachment 837

2. X-Y
View attachment 838

3. ORTF
View attachment 836

The recordings were made in my theatre / listening room which is well damped with an RT60 of around 0.25 in the midrange. All 3 recordings follow the same procedure, speech from 8 points around the room and a 1-24 count walking in a circle around the mics. This is followed by an extract from a track by Bill Morrissey. I will try and get time to record in a different room (far less absorption) and outside in the garden to see if these spaces affect the perceived soundstage.

I have a definite favourite configuration which I think most represents the spatial sound I hear. It will be interesting to see if others agree.

here are the recordings - dont laugh at my accent, I cant help being born and bred in the UK West Country! :)

http://gofile.me/2vnEF/sSiF1iTeL


Cool are those the new supplies from DIYINHK? Did you order up the multichannel USB interface with inputs as well?
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Cool are those the new supplies from DIYINHK? Did you order up the multichannel USB interface with inputs as well?

No, I built this some months back and havent ordered the USB interface yet, you can see Im still using the minidsp one.

The supplies are
http://www.diyinhk.com/shop/audio-k...-dac-power-supply-regulator-91215v-15ax2.html

The interesting this is when i initially got the TI board I jury rigged some very basic +-15 and 5Volt supplies with simple 7805,15 and 7915s. Cant get any more basic than that. The noise levels and audio quality were excellent from the ADC and up to manufacturers spec. I fitted the DIYINHK supplies and they didnt actually make a jot of difference to measured or subjective results :)!

The other home brew boards in there are supplies for the Mic preamps - a regulated 48volt for the phantom mic supply and unregulated +-24volt for the amp circuit (regulation to +-18 volts on board).
 
Last edited:

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
No, I built this some months back and havent ordered the USB interface yet, you can see Im still using the minidsp one.

The supplies are
http://www.diyinhk.com/shop/audio-k...-dac-power-supply-regulator-91215v-15ax2.html

The interesting this is when i initially got the TI board I jury rigged some very basic +-15 and 5Volt supplies with simple 7805,15 and 7915s. Cant get any more basic than that. The noise levels and audio quality were excellent from the ADC and up to manufacturers spec. I fitted the DIYINHK supplies and they didnt actually make a jot of difference to measured or subjective results :)!

The other boards in there are supplies for the Mic preamps - a regulated 48volt for the phantom supply and unregulated +-24volt for the amp circuit (regulation to +-18 volts on board).

I'm surprised those supplies didn't help. They look like very nice unit's. They use the lowest noise LDO's available. I have the previous generation ones. Maybe would be more noticeable in a DAC application.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
I'm surprised those supplies didn't help. They look like very nice unit's. They use the lowest noise LDO's available. I have the previous generation ones. Maybe would be more noticeable in a DAC application.

Well I thought it might make a difference to the analogue input section - this is fed direct from the external supply (has bypass on board). However the ADC chip analogue section has another 4volt regulator on the board and so does the digital section (3.3v). It seems that there is adequate PSRR.
 
Last edited:

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
Well I thought it might make a different to the analogue input section - this is fed direct from the external supply (has bypass on board). However the ADC chip analogue section has another 4volt regulator on the board and so does the digital section (3.3v). It seems that there is adequate PSRR.

The cheap regulator probably puts more noise into the system than it was fed and evens things out :) Either that or other stuff in the system has a higher noise floor anyways which drowns out the benefit of the cleaner power to the ADC board.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
The cheap regulator probably puts more noise into the system than it was fed and evens things out :) Either that or other stuff in the system has a higher noise floor anyways which drowns out the benefit of the cleaner power to the ADC board.

I think TI have done a good job with the evaluation board to get the best out of the adc chip. After all they are using it as a vehicle to demonstrate and sell the chip. :)

I achieve the spec typical rating dr of 123dB(A) and sounds very good.
 

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
I think TI have done a good job with the evaluation board to get the best out of the adc chip. After all they are using it as a vehicle to demonstrate and sell the chip. :)

I achieve the spec typical rating dr of 123dB(A) and sounds very good.

Yes but they are built to a price point to provide basic evaluation purposes for manufacturers to develop products with it. ESS has evaluation boards for the Sabre chips as well. But they don't preform as well as the top DAC's out there that use the chip. The noise I was referring to was noise from the mic pre boards anyways. Your system is only as good as the weakest link.

However I'm waiting for the new ESS 9038 pro chip because Dustin from ESS told me it sounds better than even the $5000 Mirus DAC when powered by a cheap SMPS! It should be popping up here any day:

http://www.shawelectronics.com/dac-evaluation-boards.html
 
Last edited:

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
Downloaded but my system is out of commission right now. Will have to listen later.
 

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia

Yep I hear you, the point is you have multiple levels of regulation plus the chips also have their own PSR. There comes a point where there is no benefit and I think that is the case here.

BTW you can bypass these regulators and input your own supplies, which of course I tried and used another DIYINHK board, guess what, the noise floor increased! :) crazy, not what you would expect.

Here is the noise floor of the board plus an overlay of my MDAC at 1kHz -60dB. I will try and get a few grabs of the mic pre amps also. Also a recording of a track being played back from the mdac plus the original for comparison.

http://gofile.me/2vnEF/dIIsnDSxO

ADC
mdac nF overlay.png


Mic pre amp Noise floor (lowest gain)

mic pre min gain.png
 
Last edited:

Mivera

Major Contributor
Joined
Mar 4, 2016
Messages
2,322
Likes
97
Location
West Kelowna
Yep I hear you, the point is you have multiple levels of regulation plus the chips also have their own PSR. There comes a point where there is no benefit and I think that is the case here.

BTW you can bypass these regulators and input your own supplies, which of course I tried and used another DIYINHK board, guess what, the noise floor increased! :) crazy, not what you would expect.

Here is the noise floor of the board plus an overlay of my MDAC at 1kHz -60dB. I will try and get a few grabs of the mic pre amps also. Also a recording of a track being played back from the mdac plus the original for comparison.

http://gofile.me/2vnEF/dIIsnDSxO


View attachment 851

If you read the datasheet of the LT3042 it says the more you run in parallel, the lower the noise is. Also helps to distribute dissipated heat. I suppose you also benefit even if the other regulators aren't of the same quality. I was always told that the best regulator should be the one closest to whatever is using the power. And it should be located very close. Within 1 cm if possible, and use high quality bypass caps to reduce noise/increase PSSR. This was likely why the noise increased. The noise was picked up in the long distance between the supply and the ADC chip/analog stage opamp. So I suppose in order to get the very best out of it, you would have to swap the regulators out on the TI board with the LT3042's. But they don't come in the same package. Not sure if there's an adapter or not available.
 
Last edited:
Top Bottom