Re: [Sursound] RIR measuring, how to capture a higher order Ambisonic room responce?

[Fernando Lopez-Lezcano]

On 05/08/2018 01:11 PM, Fons Adriaensen wrote:

On Mon, May 07, 2018 at 07:05:37PM -0700, Fernando Lopez-Lezcano wrote:


So I bought a robotic arm. Len (from Core Sound) asked off-list about it, so
I'm including some information here. I got the WidowXL from Trossen
Robotics. Anything better (as far as I could find, not an expert!) would
have driven the price up exponentially - this one is not cheap anyway. I
just spent two full days assembling it (lots of pieces, lots of screws).
Beware, ask before you buy as to delivery times - mine was delayed several
times and they were not very upfront about it (or just did not know).


One problem you may observe with robotic arms is vibration.


Yes, I did observe that "feature" :-)


It depends
on if the robot has mechanical brakes, or is using the actuator servos
to maintain a static position.


No brakes, just servos (it is a relatively "low cost" arm[*], or an 
expensive "toy", depending on how you look at it).



In the latter case there may be some
vibration due to marginally stable control loops. This is usually very
low level but a microphone will be all too happy to pick it up.

I wonder how the WidowXL performs regarding this.


Yes, it does make, sometimes, a tiny quite low level buzzing sound (no 
other way to describe it). I would like to imagine that it would not 
affect too much the recording of long sine sweeps at relatively high SPL 
levels... plus the mic mount attaches with a bit of padding. We'll see 
(hear?). See picture of one of my old prototypes taped to the grip (to 
test that the arm could actually handle the weight, had the needed 
torque, and could contort as needed :-) Not much testing done, just 
first impressions.


(busy designing and 3d printing the custom grips and mounts I need for 
the mics...)

-- Fernando

[*] at least for what I found online the next step up was about > $5-6k, 
for a good one but not industrial you could expect to pay >$20k , and 
for the real (industrial) thing maybe about the same but then you have 
to spend  in the environment in which you can run it safely... There 
were actually quite a few open source 3d printed arms but I could not 
find out that was convincing and already available.

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Re: [Sursound] RIR measuring, how to capture a higher order Ambisonic room responce?

[Fons Adriaensen]

On Mon, May 07, 2018 at 07:05:37PM -0700, Fernando Lopez-Lezcano wrote:

> So I bought a robotic arm. Len (from Core Sound) asked off-list about it, so
> I'm including some information here. I got the WidowXL from Trossen
> Robotics. Anything better (as far as I could find, not an expert!) would
> have driven the price up exponentially - this one is not cheap anyway. I
> just spent two full days assembling it (lots of pieces, lots of screws).
> Beware, ask before you buy as to delivery times - mine was delayed several
> times and they were not very upfront about it (or just did not know).

One problem you may observe with robotic arms is vibration. It depends
on if the robot has mechanical brakes, or is using the actuator servos
to maintain a static position. In the latter case there may be some
vibration due to marginally stable control loops. This is usually very
low level but a microphone will be all too happy to pick it up.

I wonder how the WidowXL performs regarding this. 

Ciao,

-- 
FA



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[Sursound] Job: R Engineer in Audio Compression at Qualcomm San Diego

[Nils Peters]

Dear all,

we have a new job opening in our 3D Audio team for an expert in audio 
coding.
Details and the application process can be found here: 
https://jobs.qualcomm.com/public/jobDetails.xhtml?requisitionId=1964127


Feel free to contact me off-list if you have questions.

Nils
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Re: [Sursound] RIR measuring, how to capture a higher order Ambisonic room responce?

[Eric Benjamin]

t look to be a robust measurement method. ..
> >
> > We always talk about the 1st reflections, in this case. Not reverb,
> > which is kind of statistical.
> >
> > Of course you can try, but how much precision is really needed? (Should
> > be clarified before...)
>
> I would have to go to my data to get some numbers... I definitely can
> see effects at high frequencies when the data capture is not precise
> (I'm in the process of trying to build a better measuring rig).
>
> -- Fernando
>
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Re: [Sursound] Strange 'buzz' in Ambisonic recording

[David Pickett]

>> On 7 May 2018, at 17:30, Gerard Lardner  wrote:

>> I recorded a concert on Saturday (John Rutter's /Gloria /and Karl
>Jenkins' /The Peacemakers/) using an Ambisonic mic and some others.
>I'm encoding the A-format to B-format using VVEncode in Reaper, and
>panning in the extra mics using Wigware Ambipan. The result is then
>decoded to surround sound or to stereo using VVDecode; all in the same
>Reaper set-up. I've used this approach before, usually successfully.
>>
>> I find that, when the organ and brass are playing at full volume (I
>mean in the orchestra, not just in playback), there is a 'buzzing'
>sound in the playback. It sounds harsh, pitched at about 50 Hz.

Some more information would be useful.

-- Which ambisonic mic were you using?

-- Does the buzz really only appear when the organ and brass are playing?

-- Is the buzz heard both in loud AND soft passages?

David

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Re: [Sursound] Strange 'buzz' in Ambisonic recording

[Jon Honeyball]

Spectral analysis would be a good clue here — sounds like clipping of LF to me

jon

> On 7 May 2018, at 17:30, Gerard Lardner  wrote:
> 
> I'm very much an amateur here, so please forgive what might be a stupid 
> question!
> 
> I recorded a concert on Saturday (John Rutter's /Gloria /and Karl Jenkins' 
> /The Peacemakers/) using an Ambisonic mic and some others. I'm encoding the 
> A-format to B-format using VVEncode in Reaper, and panning in the extra mics 
> using Wigware Ambipan. The result is then decoded to surround sound or to 
> stereo using VVDecode; all in the same Reaper set-up. I've used this approach 
> before, usually successfully.
> 
> I find that, when the organ and brass are playing at full volume (I mean in 
> the orchestra, not just in playback), there is a 'buzzing' sound in the 
> playback. It sounds harsh, pitched at about 50 Hz. But if I listen to the 
> A-format files alone in Reaper or in VLC Media Player, there is no buzz. 
> Similarly, there is no buzz if I encode the A-format using the stand-alone 
> version of VVMic. The buzz is present both in the B-format from the Ambisonic 
> mic and, less strongly, in the panned B-format from the soloists mic. It 
> appears to be an artefact of my editing configuration; but it didn't happen 
> in a recording I made, using the same configuration, last month. The only 
> difference since then has been that my old hard disc, which had developed 
> some faults, was cloned onto a new SSD.
> 
> Does this description suggest a specific problem/remedy to anyone? I know I 
> can produce a decent CD using the stand-alone VVMic route and panning in the 
> soloists into the stereo mix; but I'd like to get to the bottom of why my 
> Ambisonic configuration is doing this now.
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