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 Forum index » How-tos » Ambiophonic Sound Reproduction
Hi Ho Ambio!
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Winstontaneous



Joined: Oct 31, 2008
Posts: 39
Location: Berkeley, CA

PostPosted: Tue Aug 09, 2011 3:38 pm    Post subject: Hi Ho Ambio!
Subject description: Using Ambio for Installation in less-than-ideal Listening Environment?
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I've been on electro-music for a while but never had really noticed the Ambiophonics forum.

I'm working on a multisensory installation (sound, sight, scent) for the 2011 SoundWalk festival. I'm looking for a way to have an immersive sound experience that is distinctly different up close vs. far away.

The challenge is I'm not sure of the space I will be installing in; it's likely to be outside. Preferably it will be low-powered so I can run it on a battery + inverter. Regardless, it will be surrounded by many other noises over which I have no control, and I want to use this to my advantage...I want people to have just a vague sense of what's going on at a distance; the physical location of the visual and scent elements will put their heads (literally) in a place where the audio magic can take place.

The sound part itself consists of a VAZ Modular synth patch with 4 voice samples and 4 sine tones processed through 2 filters. Pitch, filter cutoff, and panning are controlled by slow random LFOs and a bit of automation. The vast majority of sound info is in the midrange.

At first I thought of doing some sort of surround setup with complex panning and phase shifting taking place between the speakers. This has many technical challenges. I really want my setup to be as simple as possible, playing pre-recorded files from my Zoom H4N or at most a 5.1 DVD, not a computer. My DVD player only puts out digital 5.1 while my receiver only has 6 analog inputs. I don't own 5.1 speakers and I don't have the right mixing setup. So this was more of a pipe dream that would be expensive and fraught with technical complications.

Remembering this forum, I downloaded Weldroid's ambio.one and loaded it up in REAPER. My speakers are some itty-bitty Harman Kardon desktops, and a 2.1 Tascam setup with flat-panel NXT drivers + sub. I busted out my protractor...it took me about an hour to dial in ambio.one on some of my tracks, but suddenly I was hearing sounds coming from 2-3 feet beyond, plus above and below the speakers! My initial impression was, "Wow, this is how I meant this to sound when I recorded it."

For reference the ambio.one settings that work best for my stuff are:
Low @ 230, High @ 10760, Delay @ 34, Atten @ 1, and Master @ 0.

The results are definitely more mixed on music recorded by other people. In particular there seems to be a weird phasiness in the midrange that can be shifted by sweeping Delay and increasing Atten, but it never really goes away. Am I doing something wrong, or is this just revealing anomalies of the stereo process or the auditory system?

This applies more to busy pop production; Electric Light Orchestra in particular sounds horrible and congested no matter what the settings. OTOH, anything by Brian Eno (solo, or with U2 or Talking Heads) sounds great, but somehow I'm not surprised!

I think I'll buy the Ambiophonic DSP VST to see how that behaves...curious how it differs from ambio.one.

One thing I must say is I'm very glad that the developer(s) of ambio processing chose to keep it free + open rather than going the patent/copyright/trademark route. Very cool!

Anyway, longwinded post, sorry! Next step will be to render my track at a variety of Ambio settings and run an extension cord into the backyard to see how it holds up outside. Again, I'm looking for interesting effects rather than a textbook "perfect" ambio implementation. I imagine if I use ambio in the final piece that I will automate & render different settings so the experience changes over time.

I've done a fair amount of looking through the forum and Glasgal and Miller's sites.
All the info I've found appears to be about "ideal" conditions.
Curious if others are taking ambio outside the listening room.
Thanks!
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DW



Joined: Jul 23, 2011
Posts: 12
Location: Wales

PostPosted: Sun Nov 13, 2011 1:43 pm    Post subject: Re: Hi Ho Ambio!
Subject description: Using Ambio for Installation in less-than-ideal Listening Environment?
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Winstontaneous wrote:
I've been on electro-music for a while but never had really noticed the Ambiophonics forum.

Snipped.

Remembering this forum, I downloaded Weldroid's ambio.one and loaded it up in REAPER. My speakers are some itty-bitty Harman Kardon desktops, and a 2.1 Tascam setup with flat-panel NXT drivers + sub. I busted out my protractor...it took me about an hour to dial in ambio.one on some of my tracks, but suddenly I was hearing sounds coming from 2-3 feet beyond, plus above and below the speakers! My initial impression was, "Wow, this is how I meant this to sound when I recorded it."

For reference the ambio.one settings that work best for my stuff are:
Low @ 230, High @ 10760, Delay @ 34, Atten @ 1, and Master @ 0.

The results are definitely more mixed on music recorded by other people. In particular there seems to be a weird phasiness in the midrange that can be shifted by sweeping Delay and increasing Atten, but it never really goes away. Am I doing something wrong, or is this just revealing anomalies of the stereo process or the auditory system?



Snipped.

It is a potential problem whenever two similar magnitude signals arrive at one ear with a delay between them. When the delay is a multiple (1, 2, 3 etc.), of the period at a particular frequency, you get a peak in the frequency response, and (0.5, 1.5, 2.5 etc.) you get a dip.

For a fully crosstalk cancelled situation, the delay is defined by the speaker and head geometry, and so is the attenuation by the 'average' head for the far ear relative to the near. For these three fixed conditions, this defines the relationship between the frequency response at the ear relative to that at the speaker. In this situation one can choose to apply an equalization to the phase/frequency response to get a flat response at the ear. The downside of this is that the speaker drive is no longer flat, so the sound that bounces off the walls is coloured. Listening near-field helps there.

You can compromise on the crosstalk cancelling where there are peaks, which I think is what prof. Choueiri does.

Dips in the frequency response are generally less audible than sharp peaks, so full equalization for the direct sound is not always the best choice.

Stereo, of course has a flat speaker feed, but peaks and dips in the 'phantom' centre, and little crosstalk attenuation.

RACE (in most or all present implementations) assumes a constant head attenuation with frequency, which is not actually the case, but eases the colouration and other problems.

Ambio.one and other RACE applications have the benefit of adjustable controls, but the range of these controls can be so high that most combinations are not really suitable.

Ambio.one IMO does not display the correct values for what I would define as attenuation and delay. so you cannot easily find the best settings, or directly compare with Steve Hotto's versions with the same settings.

Another problem with the applications I have tried/measured is that the filters, if used, distort the delay some distance from the crossover point.

I prefer low values of delay, and small speaker angles. This leaves only one peak in the audible range. For Ambio.one my preferred settings are against the low stop for both delay and attenuation, with the filters off.

I have not tried AmbiophonicDSP VST pluginAmbiophonicDSP VST plugin, so I don't know what applies to that.

flat-panel NXT are good for surounds, but not the Stereo-dipole as they jumble the phase.
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rmiller



Joined: Feb 03, 2003
Posts: 40
Location: Bethlehem PA 18018 USA

PostPosted: Tue Dec 20, 2011 1:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Winstontaneous wrote...

Quote:
I think I'll buy the Ambiophonic DSP VST to see how that behaves...curious how it differs from ambio.one


How'd your comparison test go? Ideally you found that Ambiophonic DSP plugin's controls compensate for the issues in posts above. For example: "Recursion" for individual head attenuation, "Delay" for the relationship between speaker angle and your head width, and "Zentrum" for the hollowness of critical center images that varies by the method used in each recording.

For those new to Ambiophonic reproduction of stereo recordings, think of conventional stereo, with speakers angled ideally 60 degrees (an equilateral triangle with the listener) as comparable to taking a color photograph but viewing it in black & white - it's not wrong if an abstract rendering is desired. But unless the colors are viewed that were also captured, it won't appear natural - an inaccurate, incomplete reproduction. Ambiophonics unmasks details in the recording that conventional speaker positioning obfuscates due to crosstalk. That's why I and others use crosstalk cancelling for monitoring accuracy in making mixing decisions. Take a few minutes to try the pre-processed demos at www.filmaker.com/products.htm (using your closely-spaced PC/laptop speakers to approximate the ideal 16 degree speaker angle for Ambiophonics), then decide whether the AmbioDSP plug-in is for you ( http://electro-music.com/catalog/product_info.php/products_id/114 ).

_________________
Robin Miller

Last edited by rmiller on Thu Dec 22, 2011 9:41 am; edited 3 times in total
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DW



Joined: Jul 23, 2011
Posts: 12
Location: Wales

PostPosted: Tue Dec 20, 2011 2:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Robin,
I hope I have caught you while you are still here, and sorry for butting in..

I have recently made an Ambisonic to Pan-Ambiophonic-thingy decoder. I hope you can try this Pre-processed files as you are probably one of few people set up to do so.
Stereo-dipole - front channel 1.2 , rear channel.5,6, Channel 3.4 empty.
Source file from here:
http://soundofspace.com/ambisonic_files/58
My dual Ambiophonic file here:
http://www.megaupload.com/?d=7MX2W3FR
AmbiFusion-DW-jhroy_hot-air-balloons.aac
You should hear 3D ie. including height.

Regards,
David.
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