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  • mmensink
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Re: Blind test of live source vs recording/speakers?
Reply #25

Mr. Krueger, let me start by saying thanks for your ABX comparator and I wish your website were still online. I should have saved the audio files on it!

You can still find them on the Wayback machine:

https://archive.org/web/

There were 3 PCABX.COM web sites that were linked together under the covers to take advantage of promotional deals on web sites of a certain size in that day:  www.pcabx.com, www.cdabx.com and www.pcabx-pr.com


Thanks!

Quote
yet I'd still love to make it work. Would you please share your experience and perhaps give some tips?
What kind of music, and is there any sound reinforcement?    ...Obviously, it will be easier to fool the listeners if the "live" sound comes from a PA system.   

It would help to have some distance between the performers and the audience.  I'm not sure how much space you'll have at a hi-fi show unless you have access to a theater.    And to make it "proper", you should be in a theater, or music hall, or whatever is appropriate for the type of music being performed.

And of course,  do your own experiments before going to the trade show.

The plan is to do cello, acoustic guitar and a small percussive set such as bongo's or djembe drums. Besides that we'll do spoken voice and perhaps singing. We'll probably also do some 'effects' with with a tambourine, or keys.

The room in which we'll be doing the test/show is 8.20 x 6.20 meters. Because listeners will be seated over the entire width of the room, we'll use a minimum of panning between speakers. In order to get a credible width in the soundstage, we'll be using a left, center and right setup.

The recordings will be done in an anechoic chamber. The speakers we'll be using are uni-directional (only to the front), but still radiate relatively wide. These speakers have no front-wall reflection but the musicians in the room do. Therefore we'll use a reflector panel behind the musicians while recording in the anechoic chamber. We'll make photo's and a video ;) .

I intend to do part of the demo 'blind', so I'll need an acoustically more or less transparent screen or curtain. Any tips as to what I could use?

Thanks!

Martijn

Re: Blind test of live source vs recording/speakers?
Reply #26

I intend to do part of the demo 'blind', so I'll need an acoustically more or less transparent screen or curtain. Any tips as to what I could use?


There is a standard theatrical tool called a scrim that is used for this purpose. You can control its apparent optical transparency with lighting. If you want people to see the scene behind it, you light the scene brightly. If you want it to disappear, you drop the lighting of the scene, and increase the lighting where the spectators are.

Re: Blind test of live source vs recording/speakers?
Reply #27
Hoi Martijn,

it seems that you have your test ready. The anechoic recording seems the way to go. Please let us know the results.

https://youtu.be/-LfPzgfPXyM

  • ajinfla
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Re: Blind test of live source vs recording/speakers?
Reply #28
The anechoic recording seems the way to go.
Using how many mics, of what types, placed where?
3ch stereo?

None the less, should be interesting, though not sure what it will show  ;)
Loudspeaker manufacturer

Re: Blind test of live source vs recording/speakers?
Reply #29
The anechoic recording seems the way to go.
Using how many mics, of what types, placed where?
3ch stereo?

None the less, should be interesting, though not sure what it will show  ;)

While I don't have anything like an anechoic chamber at my disposal, I've done recordings in quasi-anechoic environments. One such environment involved mattresses wrapped around the recording space (which was small) and one is simply out of doors and a goodly distance from any reflective surfaces.  Soft earth and to a lesser degree foliage are relatively  non-reflective.

BTW AJ if you are interested, I recently posted a comment on what I think may be one of your comments on the AES web site. It is currently in the approval process.

Using measurement mics that were designed to be flat responding in an acoustically environment of "Random Incidence" the resulting recordings tend towards being hot, dry, and bright - similar to very close micing.

Several recordings of natural sounds that were on the old www.pcabx.com web site (still available via the Wayback machine) were made this way.

Attached: one such recording
  • Last Edit: 07 September, 2017, 09:20:02 AM by Arnold B. Krueger

Re: Blind test of live source vs recording/speakers?
Reply #30
Using how many mics, of what types, placed where? 3ch stereo?
It looks like they have put a speaker in the anechoic room as well, which could mean that they recorded the cello live and, with the same recording setup, the reproduced sound from the speaker. I did see a Merging Hapi AD/DA converter for a split second, which probably means that live and reproduced audio should be sample sync. Nice for an ABX.

Re: Blind test of live source vs recording/speakers?
Reply #31
Using how many mics, of what types, placed where? 3ch stereo?
It looks like they have put a speaker in the anechoic room as well, which could mean that they recorded the cello live and, with the same recording setup, the reproduced sound from the speaker. I did see a Merging Hapi AD/DA converter for a split second, which probably means that live and reproduced audio should be sample sync. Nice for an ABX.

So then it would be a mixed live/pre-recorded performance. Now we should be concerned with the provenance of the recorded track.

Re: Blind test of live source vs recording/speakers?
Reply #32
So then it would be a mixed live/pre-recorded performance. Now we should be concerned with the provenance of the recorded track.
We'll have to wait for more info from Martijn, but I expect this is what they did:
1) record a cello (live) in an anechoic room (file A)
2) replace the cello by the speaker and play back file A. Record the speaker's output with the same mic/pre/room as 1. (file B)
3) Make sure file A and B are properly synched and level matched, and perform an ABX test.

File B will contain twice the effect of the room (probably negligible in this case) and mic/pre/ADC, plus once the speaker's noise+distortion.

  • ajinfla
  • [*][*][*][*][*]
Re: Blind test of live source vs recording/speakers?
Reply #33
In order to get a credible width in the soundstage, we'll be using a left, center and right setup.

Matrixed or discrete?

Nice speakers Btw
Loudspeaker manufacturer

  • ajinfla
  • [*][*][*][*][*]
Re: Blind test of live source vs recording/speakers?
Reply #34
Using how many mics, of what types, placed where? 3ch stereo?
It looks like they have put a speaker in the anechoic room as well, which could mean that they recorded the cello live and, with the same recording setup, the reproduced sound from the speaker. I did see a Merging Hapi AD/DA converter for a split second, which probably means that live and reproduced audio should be sample sync. Nice for an ABX.
Yes, I watched video after work, it does appear they may have done so.
I am curious about the 3ch format. For PSR, thats a good start. But the mics and arrangement being used to capture the soundfield....
Loudspeaker manufacturer

  • ajinfla
  • [*][*][*][*][*]
Re: Blind test of live source vs recording/speakers?
Reply #35
I recently posted a comment on what I think may be one of your comments on the AES web site.
I haven't posted in a while. What paper?
Loudspeaker manufacturer

  • jlohl
  • [*][*]
Re: Blind test of live source vs recording/speakers?
Reply #36
So then it would be a mixed live/pre-recorded performance. Now we should be concerned with the provenance of the recorded track.
We'll have to wait for more info from Martijn, but I expect this is what they did:
1) record a cello (live) in an anechoic room (file A)
2) replace the cello by the speaker and play back file A. Record the speaker's output with the same mic/pre/room as 1. (file B)
3) Make sure file A and B are properly synched and level matched, and perform an ABX test.

File B will contain twice the effect of the room (probably negligible in this case) and mic/pre/ADC, plus once the speaker's noise+distortion.
Why not just measure anechoic impulse response of the loudspeaker so you can convolute it with any recording (anechoic or not) and compare original vs convoluted (check sync and level as usual) ?
  • Last Edit: 08 September, 2017, 11:03:31 AM by jlohl

Re: Blind test of live source vs recording/speakers?
Reply #37
I recently posted a comment on what I think may be one of your comments on the AES web site.
I haven't posted in a while. What paper?

The hd meta study.

Not approved yet.

  • mmensink
  • [*]
Re: Blind test of live source vs recording/speakers?
Reply #38

I intend to do part of the demo 'blind', so I'll need an acoustically more or less transparent screen or curtain. Any tips as to what I could use?


There is a standard theatrical tool called a scrim that is used for this purpose. You can control its apparent optical transparency with lighting. If you want people to see the scene behind it, you light the scene brightly. If you want it to disappear, you drop the lighting of the scene, and increase the lighting where the spectators are.


Thanks Arnold! I should have checked in sooner. I've been trying to find the right material and couldn't really find anything. This seems to be perfect!

Hoi Martijn,

it seems that you have your test ready. The anechoic recording seems the way to go. Please let us know the results.

https://youtu.be/-LfPzgfPXyM

Hi Kees,

Thanks for sharing the video. Will you come and join us for the demo? It is at the XFI Premium hifi show: http://x-fi-audioshow.nl

So then it would be a mixed live/pre-recorded performance. Now we should be concerned with the provenance of the recorded track.
We'll have to wait for more info from Martijn, but I expect this is what they did:
1) record a cello (live) in an anechoic room (file A)
2) replace the cello by the speaker and play back file A. Record the speaker's output with the same mic/pre/room as 1. (file B)
3) Make sure file A and B are properly synched and level matched, and perform an ABX test.

File B will contain twice the effect of the room (probably negligible in this case) and mic/pre/ADC, plus once the speaker's noise+distortion.

Hm... that's actually a great idea! Unfortunately we didn't do that, though. The 8c's were brought to the anechoic chamber for monitoring purposes only. We did a recording of a cello, spoken word an snaredrum. The plan is to compare those recordings one-on-one with the live sound. Exciting!

Using how many mics, of what types, placed where? 3ch stereo?
It looks like they have put a speaker in the anechoic room as well, which could mean that they recorded the cello live and, with the same recording setup, the reproduced sound from the speaker. I did see a Merging Hapi AD/DA converter for a split second, which probably means that live and reproduced audio should be sample sync. Nice for an ABX.
Yes, I watched video after work, it does appear they may have done so.
I am curious about the 3ch format. For PSR, thats a good start. But the mics and arrangement being used to capture the soundfield....


The recordings were done with two microphones. However, we'll mostly work with mono from a single speaker. The playback system will be LCR.

From what I've heard so far, voice and snare drum are very live like. The cello sounds impressive, but it's immediately clear that it's not live. I think the problem is the complex radiation pattern of the cello. Therefore you can't capture the true character of the instrument with a single mic. Play that imperfect recording back over accurate speakers with constant directivity, and it's just not the same thing. We'll be using the recording anyway and it's up to us to try and explain the above to the listeners.

I think it will be a fun demo!