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What is 'Imaging'

post #1 of 45
Thread Starter 

We talk about his all the time, this headphone has better imaging than that one, this dac has better imaging than that one. What is it that produces image in audio playback? If you were given the task of remastering and remixing an album and the producer told you, "We had some complaints about the poor imaging of the first release. So we want you to really do everything you can to make this cd image really well." What would you do? Is it transient response, flat FR, low distortion, or do we even know what causes one component to produce a more believable image than another?

post #2 of 45

I think before we discussed imaging, we need to define what imaging is. Is imaging the attempt of recreating a 3D audio image or is it the "headstage" that some has redefined as soundstage. I think it would also be useful for people that are familiar with sound stage to listen to some test CD on soundstage. Once we have experienced a true soundstage, then we can have meaningful discussion on imaging.

post #3 of 45
Quote:
Originally Posted by HPiper View Post
 

Is it transient response, flat FR, low distortion, or do we even know what causes one component to produce a more believable image than another?

 

Flat FR and low distortion contribute but aren't the primary factors in imaging and soundstage (not until playback anyway), since these come from the recording quality. So if some band hired a hack of an engineer or just don't care, no amount of money will get you a system that will correct that.

Also, I second dvw's point that you need to hear these firsthand. Are there any car audio clubs in your area? (They might have a forum) In any case try to get a hold of an EMMA pr IASCA Competition Disc, or any other car audio-specific disc (Focal made one years ago). They test all parameters of an audio system in a car as per competition rules,* including imaging and soundstage. In very simplistic terms, the latter refers more to the space the sound emanates from, while imaging refers to how accurate the placement of each instrument and vocal/s are. In such discs you'll have tracks like a guy discussing both terms while walking around with a mic on a fixed position, which demonstrates how it is done when recording the music.

 

Better if you can hear all this using properly recorded discs in a properly-set up car or home audio system. IMO, some confusion here on Head-Fi probably has a lot more to do with younger people going straight to expensive headphone systems before they even listened to how a proper speaker set-up (car and at home) does it. One of my personal pet peeves is the absolutist application of signal processing as "Garbage In, Garbage Out" where people here would run a cable from an audiophile DAP's (usually more expensive than a proper receiver/processor for a car) line out instead of the right equipment that can deal with the acoustic problems in a car, like unequal pathlength form your ears to each tweeter and midwoofer on either side plus the sub behind, and the soundwaves of each tweeter bouncing off the windshield (and they think both can be absolutely fixed just by EQ and Balance L-R bias). Not to mention the practical ergonomic issues of manipulating a device that is likely sitting on the front seat than on the dash.



*The point ultimately is that natural tonality, imaging and soundstage needs to be replicated in a car; the fun in it is finding ways to get around the limitations of car audio. Classes are divided based on equipment (and other stuff like sound deadening materials) MSRP, and also how much you do to the car. You can't just rip out an entire car interior and install a lounge in there, because by definition, car audio means you can listen to that system while you're stuck in traffic or driving to the event for example. My tweeter pods would cost me points but on daily use they don't get in my way; more angle inwards gets less reflections but the vocals are screwed up when driving, and only center again if I push my head against the headrest while stopped.

700


Edited by ProtegeManiac - 11/23/13 at 8:03am
post #4 of 45
Quote:
Originally Posted by HPiper View Post

We talk about his all the time, this headphone has better imaging than that one, this dac has better imaging than that one. What is it that produces image in audio playback?

I can't think of anything that would affect imaging in regards to headphones. Imaging defines how clear and stable instrument (and voice) placement is in the stereo field. Since headphones provide sound to each ear separately with no leakage or crosstalk between channels, I don't see how that can affect imaging. The same applies to DACs and any other electronic gear. Speakers might seem to have different imaging because their off-axis response varies from one model to another. But if you sit in the center as you should when listening to stereo music, with the speakers toed in to point at you, then speakers shouldn't affect imaging either.

So what does affect imaging? Untamed reflections in the listening room! As you move your head slightly, the timing of the reflections from the left and right sides keeps changing, and that disrupts the stability of what you hear. More here:

Early Reflections

--Ethan
post #5 of 45
Language is so imprecise.... Ethan, what about "soundstaging"? Correct me if I'm wrong but headphones supposedly do better at this because they make use of the whole ear, not the ear canal, for generating the sonic input, and that is somehow more natural, or uses things about the ear that are lost if it's just a direct canal injection.....? Or is that voodo? And/or, can IEMs "correct" for this in their design?

Soundstage to me has always had primarily to do with the nature of the recording, is the mic placement simple enough in the recording, can the reverb tails be heard, but also on the transducer side, do do the drivers ring in response to fast transients, and does that muddy subsequent input to them, etc.

....?



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post #6 of 45

but a part of what your brain does is to automatically account for head turning - you really expect the sound reaching your ears to change when you move

 

so we get the infamous "straight line between you ears" "imaging" of headphones which is totally unnatural, the excessively florid discussion of various headphone's relative sound stage, imaging properties are exaggerations of just small tweaks to that unnatural line between the ears placement

 

the vast majority of commercial music is mastered to be listened to through real speakers, out there in fixed locations a distance from you in a room, still lots in just stereo

 

and with close micing, many studio productions with performers in different room/booths, not even performing at the same time - the "sound stage" of many commercial productions is "painted on" electronically by the mastering/mixing engineer by turning knobs, sliders, mousing settings in DAW


Edited by jcx - 11/23/13 at 1:57pm
post #7 of 45
True, I understand all that, and have heard a few binaural experiments over the years, which have proven interesting but not mind-blowing. As a fan of baroque/classical/romantic/modern music among other things, I do like a simply recorded performance in a live environment, not over-miked. But I certainly play around myself with artificial tracking and reverb, etc. so I understand how all that works, and actually design for headphones myself when working, not looking to achieve realism.

But I think beyond the spatial disconnect, one's ears hear sound reflected around the head, off the shoulders, within the environment..... none of that can be replicated with headphones or IEMs.

I just wonder what the differences are, really, in the ways you have to design the transducers in each technology to sound "good," given the limitation that they're aiming at an average response with recordings designed for an entirely different reproduction environment. In other words, is there any sound science specific to IEMs and specific to headphones around artificial simulation of what we loosely attempt to describe as imaging or soundstage or air or whatever. Or is that not even a subject.


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post #8 of 45

audio processing for "spatial sound" in headphone listening subject is called Virtualization

 

crossfeed with filtered, delayed signals from the other stereo channel is a start to try get back some of the features of having your head between your ears in a real sound field, can be done with analog circuits or as a digital sw plugin to your digital source

 

crossfeed circuitry used to be more promenently featured in headphone amps here a few years back

 

plugins for popular PC media players exist, and there's DolbyHeadphone

 

RockBox even includes crossfeed in their DAP sw

 

 

 

probably the best comercial system today is the Smyth Realizer DSP with head angle tracking http://www.smyth-research.com/technology.html

post #9 of 45
Cool stuff, thanks for the info.

That Smyth Realizer looks like interesting work; I hope the technology becomes mass-market some day.



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post #10 of 45
Quote:
Originally Posted by Copperears View Post

Ethan, what about "soundstaging"?

That's the same thing as imaging.
Quote:
Correct me if I'm wrong but headphones supposedly do better at this because they make use of the whole ear, not the ear canal

Headphones have perfect imaging simply because they avoid room reflections. Again, it's the reflections that destroy imaging.

--Ethan
post #11 of 45
So, no difference on that between headphones and IEMs?
post #12 of 45
Quote:
Originally Posted by EthanWiner View Post

Headphones have perfect imaging simply because they avoid room reflections. Again, it's the reflections that destroy imaging.

--Ethan

 

One caveat though - left can't hear right and vice versa without something like Crossfeed. On some headphones the soundstage is like someone poking a trident at you - far L, C, and far R are too far forward, but everything between L-C and C-R sounds a bit too far behind. I've come across a guy who described that (from my SR225) as "more 3D" than the speakers he's tried, but when you consider how the drum rolls have some hits that seem farther out than the others, it's obvious that the recording was more flat (from front to back) with which the speakers were accurate, then the headphone was just problematic.

 

Still, that part about not dealing with room reflections is what's great about them. The only room large enough for speakers in my house has a the ceeling slanted on one side, which is best used behind the speakers, but still leaves me with the left side of the room which is concrete (the outer wall) and the left side of the room with a wooden wall (separating it from second floor the hallway). Everything on the left side is too loud and too forward - I've tried a bunch of acoustic panels on that side but no dice.I didn't want to do major renovations because on sunny days I'd open the window on that side and read in that room. Well, now the headphone system sits below that window. My amp has Crossfeed but on my headphones (and the relatively smaller soundstage on the amp's DAC) I don't really need it. Despite theoretically problematic headphone L-R issue, on some headphones it's a lot less of a problem vs how a room can screw up any speaker in it.


Edited by ProtegeManiac - 11/25/13 at 7:10pm
post #13 of 45
Thread Starter 

That pretty much sums up why I usually listen to headphones, I don't have a room that will do justice to my speaker system. I saw some JBL powered monitors the other day that said they were engineered for near-field imaging and frequency response. I assume that means you are supposed to listen to them from a pretty close distance and therefore room acoustics won't affect them as much as other speakers. If that is true, that may be a partial solution. Sort of a hybrid between headphones and speakers.

post #14 of 45
Quote:
Originally Posted by HPiper View Post
 

That pretty much sums up why I usually listen to headphones, I don't have a room that will do justice to my speaker system. I saw some JBL powered monitors the other day that said they were engineered for near-field imaging and frequency response. I assume that means you are supposed to listen to them from a pretty close distance and therefore room acoustics won't affect them as much as other speakers. If that is true, that may be a partial solution. Sort of a hybrid between headphones and speakers.

 

I had a pair of Swan D1080 MkII 08s myself at my workstation, which saved me a lot of earritation from wearing a headphone or IEM all day when I had to. Imaging was great for the price (plus you get an amp with it for $150, perfect if your headphone amp or DAC has a preamp or bypass output), tone was a bit warm but I suppose it would have been fatiguing otherwise at just 18in away from my head.

 

Unfortunately, with the possibility of doing my PhD elsewhere, I decided to start selling off some stuff I can't take with me rather than have them stocked up. Even my car's gonna go with its entire audio system - I'll definitely miss that huge amp, but it's about time I got into Class D's anyway.

post #15 of 45
Quote:
Originally Posted by HPiper View Post

That pretty much sums up why I usually listen to headphones, I don't have a room that will do justice to my speaker system. I saw some JBL powered monitors the other day that said they were engineered for near-field imaging and frequency response. I assume that means you are supposed to listen to them from a pretty close distance and therefore room acoustics won't affect them as much as other speakers. If that is true, that may be a partial solution. Sort of a hybrid between headphones and speakers.


I've pretty much given up on speakers and room acoustics, as it's an expensive, messy, ultimately uncontrollable listening environment.

There is so much NOISE these days, be it sirens in the distance, dogs barking next door, airplanes overhead, traffic and horns nearby, HVAC systems turning on and off, inside or out, washing machines, dishwashers, electrical hum, people talking, computer hard drives whirring, children shouting, neighbors arguing, pets scratching their behinds, rain, wind, etc. etc. that I'd just as soon eliminate all that with a good pair of IEMs and at quieter moments, headphones, and be entirely with what I'm listening to in my nearly silent sound cocoon.

And that's at home. smily_headphones1.gif

So one can go on forever about speaker refinements, near-field, etc. and I simply won't care.
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