Measuring Imaging?

[BeeKay]

Obviously, we measure the individual channel (source, amplifier, loudspeaker) very well. The methods are very well scientifically substantiated and this enables us to achieve comparability and a reliable evaluation system between different devices.

So in the mono range, it's all sunshine and roses.

How do we measure and compare spatial imaging performance? Of course, the listening room is highly individual. But we have the same problem with the single channel.

Will these journeys ever continue so successfully with two (or more) channels?

 

[DVDdoug]

How do we measure

You don't . With normal stereo, the sound obviously really comes from a pair of speakers (or headphones). Everything in-between, including the phantom center is an illusion. It's mostly up to the mixing engineer to create the illusion. Then of course, the speakers & room acoustics play a role, as well as your brain (and possibly your imagination).

I suppose you could set-up an experiment with a panel of listeners, with a particular recording in a particular room and maybe get some kind of consensus. But, I don't see much value in that.

With headphones, the most common perception is that the sound is coming from inside the listener's head. Very few people get a realistic soundstage illusion. Headphone Soundstage Survey

 

[BeeKay]

Thanks!
I was looking mostly for a standardised approach to compare the imaging capabilities of different speakers. Some method to ideally overcome pure subjective reports on which speaker with how much toe-in would excel at the job and which less so.

Not much hope though …

 

[Speedskater]

I think that the Siegfried Linkwitz (RIP) site may have some papers on the subject.

Linkwitz Lab - Loudspeaker Design

Design and consultation in electro-acoustics. Fundamental concepts of sound reproduction in rooms. Detailed design information for DIY construction of a subwoofer and an open-baffle speaker with exceptional fidelity. Dipole loudspeaker design for true to the original sound reproduction with...

www.linkwitzlab.com

 

[ppataki]

I was under the impression that the wider the 'dispersion' (horizontal directivity) is, the wider the image will be

But please correct me if I am wrong

EDIT: or probably it is better to say that the soundstage will sound bigger

 

[youngho]

How do we measure and compare spatial imaging performance? Of course, the listening room is highly individual. But we have the same problem with the single channel.

It sounds like you're asking how to measure and compare subjective experiences, like "how can we measure and compare how painful different sorts of trauma like stab wounds or blunt force impacts are?" You can create numerical rating scales, but I don't think that there is really any objective, quantifiable way to measure and compare individuals' perception in a realistic way (fMRI?). When it comes to spatial perception, ITU-R BS.2399-0 (https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BS.2399-2017-PDF-E.pdf) does give some specific categories and terms to consider. Probably you're referring specifically to localizability.

In any case, you may enjoy reading this thread if you haven't seen it already: https://www.audiosciencereview.com/...creates-a-large-and-precise-soundstage.48542/

 

[kemmler3D]

Thanks!
I was looking mostly for a standardised approach to compare the imaging capabilities of different speakers. Some method to ideally overcome pure subjective reports on which speaker with how much toe-in would excel at the job and which less so.

Not much hope though …

You would have to do it with a panel of listeners, because imaging ultimately happens in the brain. It's trivial to make an audio sample where tones should appear to be coming from specific angles when the speakers are in a specific position relative to the listener. Or even make real musical recordings where the position of the musicians is precisely noted.

But someone then has to sit down and compare the intended angles with the apparent ones coming out of the speaker.

However, if you could establish a strong correlation between subjective results and measured ones, using a torso simulator with mics, (the proper name for that escapes me) you could then use the mics to measure imaging. This would be something like preference score.

I think It would probably only take $10m or so to fund this study from scratch. But, I have to imagine a lot of the research already exists but isn't public or hasn't been applied to speakers in this way. Otherwise how are these companies putting out convincing virtual surround products?

 

[Mort]

I was under the impression that the wider the 'dispersion' (horizontal directivity) is, the wider the image will be

View attachment 455959

But please correct me if I am wrong

EDIT: or probably it is better to say that the soundstage will sound bigger

The right Directivity measurements will tell us something about the imaging, I agree.

 

[Keith_W]

Unfortunately the jury is out on this one. As @DVDdoug says, imaging is an illusion. But what are the objective measurements that create this illusion? Nobody knows. Everybody agrees that it has something to do the direction, timing, and loudness of the reflections, but nobody agrees on how much. Everybody agrees that the directivity of the speakers is important, but nobody agrees on whether narrow or wide or even omni is the best. The studies have not been done, there is no evidence, so nobody can tell you for certain. And that is the sad state of affairs.

 

[Mort]

We can identify bad imaging on polar plots, right? The directivity index isn't meaningless.

 

[kemmler3D]

We can identify bad imaging on polar plots, right? The directivity index isn't meaningless.

Yes, but I think from that we can only really say "imaging should be OK" or "imaging is probably wrecked". As @Keith_W says, we don't have the data to say exactly what perceptions of imaging are likely to happen based on speaker measurements.

You can find a lot of people who will offer strong opinions about this, but I'm not aware of actual science that would give us a rubric to predict imaging more specifically, based on a spinorama or any other measurement. I'm not saying no such research exists, but I don't know about it.

 

[MatrixS2000]

Obviously, we measure the individual channel (source, amplifier, loudspeaker) very well. The methods are very well scientifically substantiated and this enables us to achieve comparability and a reliable evaluation system between different devices.

So in the mono range, it's all sunshine and roses.

How do we measure and compare spatial imaging performance? Of course, the listening room is highly individual. But we have the same problem with the single channel.

Will these journeys ever continue so successfully with two (or more) channels?

Use this sound file and the screen capture below. It represents what the intended image placement should be:

The file has 7 drum beats each imaged slightly differently as per the above illustration.

 

[thewas]

See also this and the threads linked in it:

Can you measure imaging and soundstage?

Like the title says, can you quantify or measure imaging and soundstage? I have had many different speakers, some large and some small, sometimes the large speakers have smaller soundstage than a bookshelf.. sometimes much less expensive speakers image much better than a more expensive or better...

www.audiosciencereview.com

 

[RickS]

See also this and the threads linked in it:

Can you measure imaging and soundstage?

Like the title says, can you quantify or measure imaging and soundstage? I have had many different speakers, some large and some small, sometimes the large speakers have smaller soundstage than a bookshelf.. sometimes much less expensive speakers image much better than a more expensive or better...

www.audiosciencereview.com

Agree, the topic has gained some traction recently, but we have too many comparable threads. This one may have a very short lifespan.