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B. Midrange and Woofer/Mid-Bass: Now mute all but the midrange. These are easier
because phase is more obvious at lower frequencies and because you can use more volume.
The procedure is the same but now you should use the male vocal. Listen for the vocal
location. It should be at a specific location near the center of the window. Change the
phase of the right speaker a few times and listen to the difference. Use the combination
that puts the vocal in a specific central location. Then you can mute all but the Mid-Bass
and do the same as for the midrange. Note: Another easily heard sign of phase in mids
and woofers is bass. When 2 speakers are out of phase there will be less bass. More bass
in-phase/less bass out-of-phase, listen for this in addition to the localization.
C. Subwoofers: Woofers are the easiest. Play something with bass. The male vocal should
work fine. If you are using multiple woofers they must be in phase or your bass will go
away. When you change the phase of the right woofer it will be extremely obvious which
polarity is correct. Note: Now you have phased each pair of speakers. Hopefully all are still
0, but if not it's OK, but from now on they can only be changed by the pair. Never change
only one driver out of a pair. It's best to make a chart of speaker phases so you have it for
reference later.
Phasing the System: Setting the front stage
D. Tweeters to Mids: Now we start phasing the driver pairs to get a proper front stage.
Again, from here on we change only by the pair. Mute all except the tweeter and midrange
channels and listen to a musical track. The main vocal should be centered and the sound
stage should be spread across the window about 1/2 ~ 2/3 the way up. Listen for this.
Now change the phase of both midranges and see where the sound stage is. If the
tweeters and mids are out of phase, the stage will be lost (usually it will drop toward the
floor). Do this a few times (always changing only the mids) and see which position puts
the sound stage higher up where it should be, right across the window. You will leave
these this way now and bring in the Mid-Bass.
E. Woofers/Mid-Bass: Un-mute the mid-bass and see where the sound stage goes. If it
pulls down to toward floor, then reverse the phase of the mid-bass drivers. Try both ways
a few times to see which gives the correct sound stage.
F. Subwoofers: Subs can be difficult, but not because of bass. You have already phased
the woofers. There will be bass! The issue will be the transition from bass to mid-bass. Play
a cut with good mid-bass (kick drums are excellent). Look for sharp solid mid-bass. Change
the phase of the subs a couple of time and listen. A bad transition will leave mid-bass soft
and weak. Also listen for location. you want the bass to be in the sound stage... not in the
trunk. If your woofers are in a portable enclosure you may even want to move the box
location to see what that does. The key is finding that combination that gives clean solid
mid-bass that seems to come from the front of the car.
Now you have set the R-to-L phase of each pair of speakers and you have blended each
pair into the system in the correct phase for the best sound stage.
SAVE: At this point you completed the system setup and will want to Save to File then
Write to Device to save the work. Write to 2 memory positions so you have one to work
on and one as reference.
Manual Tuning
At this point you have effectively set up your entire system. Each channel has the correct
input, each speaker has been identified as to function, the crossovers have been set for
each speaker, the delays are set for the proper sound stage and you have assured that all
speakers are operating in the same polarity acoustically. Now it is time for the most difficult
and most subjective part. Tuning the system to have the correct sound in the car. Since
every car is different from every other car, the tuning must be done specifically for your
individual car and your specific equipment. A car is a poor listening environment because
so many factors in the car change the sound as it moves through the car interior. Windows,
upholstery, even the very shape of the car all affect the sound waves and you need to
tune the system to compensate for those affects.
The goal is to get the sound the artist intended, even though you are sitting in your seat
in the car, and not at a concert. To do the tuning you will need a 1/3 Octave RTA (Real Time
Analyzer) and a source of “pink noise”. Pink noise is sound that has equal signal levels at all
octaves. It is a standard of reference that, in conjunction with an RTA can show you what
your car is doing to the frequency response. Then you can compensate with the equalizer.
Also handy is a 31 column sheet to chart the response before equalization.