Imaging and Staging problems in the Prius? (stereo issues)

I've yet to see any threads in here on the subject so I thought I would bring it up in case some of the more high-end stereo orient people could benefit from the info.

I recently installed a set of Diamond Audio D9 7" component speakers and I ended up having to mount the rather large tweeters in the small "dash window" area. This puts them a bit forward of the stock tweeter locations but at almost the exact same height.

The Problem: I cannot get anything even close to a center image with this speaker configuration. A large part of high-end car stereo is the "imaging and staging" effect you get with certain speaker placement and processor configurations. IE. The vocal portions of music sound like they are coming from the center of your windshield and just a bit forward. You are essentially trying to recreate a true sound stage with vocals in the center and other instruments on either the far left/right and some behind. For some this may sound od but when it is done correctly it can truely make listening to your music in the car almost magical. lol In my situation the sound quality is spectacular but the vocalist sounds like it is coming from my A-pillar.

Some high-end processors can allow specific manipulations of speaker phase, equalizer adjustments, and even time alignment to try and get a proper soundstage set up in your car. There are also tricks that can help those without processors or EQ's to come close to the same results. I'm going to post 1 such procedure as it really helped me drastically change the sound in my system and it could help any of you even if you are just running deck power.


The Solution:

• Set up your speakers and equipment correctly in the first place with a mind for staging and tonal quality (just putting them in the stock locations doesn't always work the best for sound quality).
• Perform the procedures listed below or something close to them in an attempt to correct for poor speaker placement or phase issues.
• Purchase a processor capable of allowing the adjustments needed to recreate the sound stage. This is generally considered the last resort method but a great many people do it.

After prerforming a modified version of the procedure listed below I was able to get a center image but not quite as solid as I would like as a small amount of vocals still seem to come from the left A-pillar even though the main image is in the center just above my MFD. I will not post the procedure I performed (adjusting individual tweer levels, midrange phase swap, balance control etc.) because it is confusing and it is unlikely most of you would have a configuration close to mine AND the fact I will have to chnage it once I get a processor so I'll keep things basic for now. I will admit to having used the Balance adjustment 1-2 clicks (out of 15) to the right. If anyone has better information I'm all ears as this is a mixture of old school tweeking and new information I didn't know about. So without further bs here is the procedure. If it helps you attain a better center image I'd love to hear about your results. If you already have a processor that allows for individual adjustment of Left and Right channels then life will be easy for you after you go through this procedure.

Quoted from Diymobileaudio.com and Elitecaraudio.com. Those guys are full of great info.

Originally Posted by Cmusic from ECA
There are several different methods used to tune eqs. This is the one I use. An RTA is not needed if the steps are done correctly. This method uses crossovers and gain settings as the most important factor in tuning. I think the eq should be last in line when tuning. Remember after each step to write down your settings. If the sound gets worse, then you can go back to the previous step’s settings and start over.


1. Set all bands flat, as well as the head unit bass and treble.

2. Turn off the subs. Using music with a good bass line, run the highpass crossover up and down until the midbasses can play as low as possible without any distortion or excessive door panel vibrations.

3. Unhook the mids and tweeters, allowing only the midbasses to play. Listen to mono pink noise or a well-recorded song with a centered vocalist. Test CDs such as the IASCA test CD or Autosound 2000 Test CD 102 or 103 will work great. Listen to where the centered sounds are coming from. Then reverse the polarity of one midbass (Reverse the speaker wires coming from the passive crossover and going to the speaker, just flip the positive and negative wires. I usually flip the driver’s side speaker.) and re-listen to the test CD. If the sounds are more centered then keep it as is. If the centered sounds are more diffuse and un-locatable, then flip the polarity back to where it was originally.

4. Then unhook the midbasses and play the mids only and follow the same polarity and listening tests as before. Mark your best settings.

5. Do the same procedure for the tweeters.

6. When you have tested for the proper polarity from all three ranges of speakers, hook all of them back up with respect to each set of speaker’s best polarity. You can have any combination of polarity, such as all the midbass and tweeters straight and one midrange reversed.

7. Now you should have the correct “acoustic†polarity set within each set of speakers. Next is to set the acoustic polarity between the sets of speakers.

8. Listen to some very familiar music with a good range of sounds. Then flip both midbass’ polarity and listen again. Before you only flipped one midbass, now you are doing both at the same time. For example if the left midbass was reversed and the right was not before, now the left will be not reversed and the right will be. Listen to the music again. If the midbass is more powerful and full then leave the wiring as is. If the midbass sounds weaker and wrong then restore the wiring as before.

9. Perform the same listening tests while flipping the mids and tweeters, and use the wiring configuration that sounds the best.

10. If you have went though all these steps adjusting the polarity of the speakers then the system should sound really good without any eq adjustments. You might want to play with the gain adjustments on the crossover and/or amp to better blend all the speakers together.

11. Now onto the eq! The first eq step is to adjust the tonality. While listening to familiar music, adjust each individual band up and down slowly. When the music sounds better then move to the next band. Adjust the left and right bands equally. (We’ll get to the separate left and right adjustments soon.) It really does not matter if the bands are boosted or cut, just that it makes the sound better. Not every band needs to be adjusted. In fact if you did steps 1 thru 10 correctly you should not have to adjust over half the bands. Having a 1/3 octave eq does not mean you have to adjust every band. It means you have the ability to adjust each band if needed. Watch out for big jumps from band to band, like one band set to +4 and the next band set to –6.

12. Continue through all the bands, take a break, and do the same procedure over again. But this time the adjustments will be smaller as you get the tonality dialed in. This step might take several days, weeks, or longer.

13. In tuning you will find some eq bands will raise, lower, move the sound closer, or farther away if adjusted in certain manners. For example, lowering 5 KHz will generally move the soundstage farther away and raising 2 KHz will make the soundstage rise. Each vehicle and system will have different settings that will be the best. The best way to achieve awesome sound is to constantly adjust.

14. When you are satisfied with the tonality of the system, it is time to start adjusting the left and right channels separately. These adjustments should not affect the tonality, but improve on the imaging and soundstaging. Using the Autosound 2000 Test CD 102 or 103 “My Disk†listen to the individual frequency pink noise tracks. (Test CD103 has the tracks arranged in an easier configuration.) Each frequency band should sound like it is coming from the center of the soundstage. If one band is off to one side, then use each band’s left and right eq controls as a balance control. This is very similar to the head unit’s balance control, only now you are balancing each frequency band by itself. For example if 200 Hz seems to be shifted to the left of center, lower the left 200 Hz band and raise the right 200 Hz band one dB at a time until the band is centered. If a frequency is shifted to the right, lower the band’s right channel and raise the left channel in small amounts.

15. When you have when through all the bands take a break. Then later go back through each band one by one and make any further needed adjustments until all the frequencies are lined up in the center of the soundstage.

 

LMAO! In actuality some CDs I would seriously assume this to be the case. Most popular music is record rather terribly so proper staging or imaging is hard to come by.

 

I'm not sure if I am following you Tom.

If you mean correct polarity as in all the positive and negative wires are hooked up to the corresponding positive and negative terminals then yes, that was done correctly the first time. One way to check the polarity of larger speakers is to take a small 12v battery and connect it to the speaker leads in small "taps" and watch which way the speaker cone moves. If it moves out with the positive wire on the positive terminal and negative to negative then your polarity is correct. If it moves in when power is applied then the polarity is backwards. The problem is that does not always sound good or give the correct phasing of the speakers for this particular application. The car is an interesting environment for audio reporduction because of it's shape, materials, and alignment issues.

So my system was hooked up "correctly" but didn't sound right with respects to imaging, tonal quality was excellent though. By reversing the positive and negative wires on one of my midranges (left) the center image shifted way over to the middle. I later reversed the other midrange (right) and put the first midrange (left) back to normal polarity just to ensure I was not losing tonal quality or midbass.

This is why many people have stereo systems that sound marginal or not nearly good as they could. Much of the work the guys on Elitecaraudio.com do does not seem intuitive unless you are schooled in audio repoduction and theory. I'm not so I just read what they do and try it for myself.

 

Thanks. That helps describe why absolute phase can be different for each speaker yet still produce a focused image and maintain overal tone quality and midbass performance (in the right combination)yes?

 

Agreed. I believe this is why the guys on that forum always state that your gains and crossover points are the most critical and first priority (excluding install). Then comes phasing, then comes EQ and/or time alignment adjusments.

My amplifier has a 4th order Butterworth filter (I'm pretty sure it's a 4th order) with adjustments from 50hz to 5kHz. My crossover networks (part of the component set) allow for a 180deg phase swap, bi-amplification, and a +2,+0,-2,-4 tweeter lvl adjustments. These are essentially the only tools I have to work with.

From further reading on Elitecaraudio.com I find that adjusting left and right channel frequencies independently one can shift the center image as well. This is one of the reasons I am thinking about purchasing an equalizer like the Audio Control DQS.

 

I thought about it and it would have been my first choice of adjustments but they are fixed in those pods and cannot be moved. The only other option is to try shaving down the pod and having it re-covered but I'm not favorably inclined to that idea since my buddy spent so much time working on them. My center image is pretty good right now but needs a lil more tuning. I think the EQ can fix it. Thankfully I can try it before I buy it.

This is exactly the find of dialog I was hoping for so that others can see how much equipment choice and installation can affect sound quality. There is so much more to it than simply buying a set of speakers and slapping them in the door. Thank you guys for the helpful advice so far.

 

I only mean to resurrect this old thread so that I can add that using the time alignment feature on my headunit was the easiest way to achieve a decent center image.