What makes good imaging?

[lowpolyjoe]

I'm referring to the ability of a set of stereo speakers to convince you that the different sources that comprise the audio stream are arranged precisely on a sound stage - not just blaring out of one speaker or the other.

When I got into home audio (mostly home theater) I never felt like I had such a great sound stage without a center channel. But when adding a center channel, it was always under the TV and voices of characters on screen always seemed somewhat 'beneath' where they should be. When I built my Finalists and ditched the center channel, I was very pleasantly surprised. The image is pretty stable, even in poor seating locations (ie. far over to one side). With the tweeters at ear-height, things sound like they should and I'm very happy


My question about imaging has 2 motivating factors.

Firstly, I'm nearly done with my first ever design effort for a small bookshelf MTM. I have not done enough listening yet to determine how they image, but if they suck, I'm curious if there is anything I can do to improve them. I'm thinking perhaps phase issues between drivers are my biggest issue when reviewing my modeling data at this point.

Second, there have been a couple of car audio threads recently that got me wondering if I should try to replace the rather dreadful setup in my car. I was heavily into car audio a long time ago. I never had good imaging in my car. Honestly, a lot of people who 'supposedly' had good imaging setups, I never found very convincing either. But I'll admit I never sat in a serious SQ show car. At the time (~15-20 years ago) I recall people moving away from door speakers and making fiberglass kickpod setups and aiming the drivers at the opposing seat. My understanding was that this

1) comes closer to equalizing the distance from each channel to your ears
2) puts you 'on axis' for the far source and 'off axis' for the near source to help balance relative SPL (at least at higher frequencies)

I don't think I ever heard one of these setup so I don't know if it works, but those principles seem reasonable to me. I don't expect i'll build pods. I have woofers in the lower door panels and tweeters in the doors near the side view mirrors (Subaru WRX). If I approach this setup with measurement equipment and PCD, is it reasonable to expect accurate imaging out of a configuration like this if I use quality components and produce a good crossover?

Thanks a lot.

[Navy Guy]

Re: What makes good imaging?

In regards to the car audio kick panels, it also puts the woofer and tweeter closer together so you don't suffer so much comb filtering or off-axis nulls around the crossover point.

[jsr]

Re: What makes good imaging?

I've personally found phase alignment to be an important (most important?) factor for precise imaging. I've built some speakers (not my designs) where phase alignment between drivers was not optimal and imaging was average (average being typical of what I'd hear on many commercial speakers). I modified the XOs on one to improve alignment and imaging improved. With that said, this design has received tons of praise from the community, so precise imaging may not be all that important to many. I try to get as good phase alignment as possible across as wide a band as possible without sacrificing frequency response in personal designs, but that's because I'm anal on some performance characteristics.

Regarding car audio, I've never been in a setup with the same level of imaging as a well done home setup either. In car audio, the environment plays a much larger (dominant?) role. The quality of sound is much less on axis first arrival sound and more power response with all reflections, in and out of phase, combined. With door panel mounted drivers, I don't think you will get beyond reasonable imaging (which if that's what you're shooting for will be fine). People use kicks to make the on axis response a larger factor. Without properly aiming the drivers, there's a ceiling in performance in car audio that's well below what's possible.
As for the crossover, keep in mind car audio crossovers are not time aligned. That's left to the active electronics, be it your HU or amp or sound processor. Car audio crossovers are nothing but straight filters. Better ones contour the response and help squash breakups, but still just used as filters without much thought into time alignment because the mfrs don't know where you'll place the drivers. Even for you, if you designed them to be time aligned in your setup, that limits the usefulness if you move it to another car. For car audio, use of active processing is a better option and you can get very good performing active equipment for mobile audio at much lower cost than home equivalents.

[Sydney]

Re: What makes good imaging?

... I never had good imaging in my car. Honestly, a lot of people who 'supposedly' had good imaging setups, I never found very convincing either. ...

Me neither ( FWIW )

[Architect7]

Re: What makes good imaging?

Remove first reflections as much as possible. Use angled surface mounts to mount your tweeters instead of flush mounts.

Time alignment works wonders. I have my tweeters in surface pods on my A-pillars and mids lower in my doors. After taking measurements from drivers to my ears and punching the numbers into my Eclipse HU, the image is front and center on top of my dash/mid windshield. I was planning to go 3-way to get my image up higher but right now I don't really have a need to.

[Paul Carmody]

Re: What makes good imaging?

If I told you, I'd have to kill you.

[jon96789]

Re: What makes good imaging?

I cannot tell you what makes for a realistic soundstage and imaging, but I can tell you I have only heard it twice in my past forty years in hi-fi.

Once with a pair of Magnepan MGII planar speakers driven by a Sony STR-7800SD receiver, Sony PS-X7 turntable and a Shure V15-Iv cartridge in 1974. When I listened to Kenny Rankin, the symphony was in the background, the sax solo was a bit in front of the orchestra and vocals were up front and center. I could pinpoint the position of each audible sound in depth and lateral locations.

The second time was with a pair of KEF 104.2 speakers driven by SEP tube amp and a Marantz CD player in the '80s.

I have tried in vain to replicate the imaging to no avail. All I can say is that once you obtain a realistic soundstage, it is mesmerizing.

[lowpolyjoe]

Re: What makes good imaging?

In regards to the car audio kick panels, it also puts the woofer and tweeter closer together so you don't suffer so much comb filtering or off-axis nulls around the crossover point.

That's a good point I hadn't thought about. I really don't want to make pods - but it does seem there are some good arguments for them.

As for the crossover, keep in mind car audio crossovers are not time aligned. That's left to the active electronics, be it your HU or amp or sound processor. Car audio crossovers are nothing but straight filters.

Thanks for all the info. I do recall a lot of serious car builds using a lot of active stuff. I'm trying to avoid running any extra electronics. I don't even have an amp or sub at the moment and i would like to keep it that way. I guess whichever way i go, having a DATS and Omnimic should help me out

I have my tweeters in surface pods on my A-pillars and mids lower in my doors. <snip> and punching the numbers into my Eclipse HU

Hmmm... i would kind of like a stock look. But maybe i could look into a new HU that has some better DSP functionality. I'm running an ancient double-din Pioneer at the moment. Ugliest thing I've ever seen but it does the job. This raises another question I've been pondering - are there any HUs out that mirror iPhone/iPod GUI directly (including both display and touch input)? I heard this sort of functionality (CarPlay?) is coming soon to several car manufacturers so i was wondering if it's available on the aftermarket side yet.

Me neither ( FWIW )

My cynicism outweighs my susceptibility to peer pressure when everyone else says "sounds great" ;)

If I told you, I'd have to kill you.

Could be worth it :p

[Navy Guy]

Re: What makes good imaging?

One thing that I have thought about doing if I ever tried to do another car audio setup in the future would be to use a stout 2-3" driver that can play down to around 300-400 hz with a small tweeter like the Vifa OT19 and mount both of those in the A-piller. That way the woofers in the door are only doing the low end heavy lifting and most of your freq content that is going to be really directional is in the same area.

[lowpolyjoe]

Re: What makes good imaging?

One thing that I have thought about doing if I ever tried to do another car audio setup in the future would be to use a stout 2-3" driver that can play down to around 300-400 hz with a small tweeter like the Vifa OT19 and mount both of those in the A-piller. That way the woofers in the door are only doing the low end heavy lifting and most of your freq content that is going to be really directional is in the same area.

Did somebody say "peerless 2" buyouts"? lol :p

I fluctuate back and forth on what i want to do with my car. Half the time i think i should just sell it and get something more suitable to my age and driving habits (ie. do little or no work on the car or audio setup). Other half of the time i want to go all out and build a quality sound system and get a turbo back exhaust with a pro tune. <sigh> .... don't know what to do.



jon96789 - I definitely agree that finding good imaging is like a needle in a haystack proposition in my experience. Having good depth to the stage is some next level stuff.

[Face]

Re: What makes good imaging?

I've only heard one car audio setup that had both imaging and a soundstage. He had tweeter and mid pods on top of the dash by the A pillar and the right amount of delay. Too bad these kind of setups are far and few between. And of course the crossover between the two components(mid/tweeter) is very important as well. I would try for smooth, flat or an angled downward phase response(non wrapping) between the two drivers.

[craigk]

Re: What makes good imaging?

Paul I hope you do not kill me, if you do have fun with the drivers. :D symmetry. matching all components as closely as possible is a start in the right direction. drivers, caps, coils, every thing. no flames on this one, just my opinion. I also think that a cab where you "do not" offset the tweeters is the way to go. I know sometimes there are benefits to this, but looking back, speakers that are aligned on the center line of the cab image and have a more stable sound stage usually, and yes I have heard exceptions. I will now go into the witness protection program.

[Architect7]

Re: What makes good imaging?

Hmmm... i would kind of like a stock look. But maybe i could look into a new HU that has some better DSP functionality. I'm running an ancient double-din Pioneer at the moment. Ugliest thing I've ever seen but it does the job. This raises another question I've been pondering - are there any HUs out that mirror iPhone/iPod GUI directly (including both display and touch input)? I heard this sort of functionality (CarPlay?) is coming soon to several car manufacturers so i was wondering if it's available on the aftermarket side yet.

Here is what mine look like:



I recommend the Pioneer DEH-80PRS. Best deck on the market right now under $1k, many of the features of its big brother, the P99RS. Time alignment, active 3-way crossover, 16 band EQ and a great auto eq/ta program as well. Plus it acts as a DAC for iPods and USB thumb drives for even better sound quality.

[kanemack]

Re: What makes good imaging?

I have heard a few cars that pulled off imaging really well. The main problem was that they were tow in show only cars, meaning they were useless as cars. There was a system way back when from Rockford Fosgate called Symmetry which consisted of a rack where you would add amps and various DSP units. Did a great job from everything from 1/3 octave eqs to time delay stuff. I did manage to talk one person into buying it, as most didn't like the $10k base price. Now that side of the industry is gone. My friend's car audio store now specializes in anti DUI blowy things.


I even found a picture of one:



Looks pretty high tech even now. In a car you need a lot of "high tech" to get good imaging.

[kanemack]

Re: What makes good imaging?

Oh and I forgot, look into dipole designs for home use... they do a lot better jobs with imaging and soundstage.