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Installation Question

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=25805
Printed Date: May 17, 2024 at 5:43 AM


Topic: Installation Question

Posted By: Julian59
Subject: Installation Question
Date Posted: February 03, 2004 at 9:34 PM

Here's a Installation Question,  This happen to us way back. We installed a massive system, over 4000 watts (cost over 12,000) it just didn't sound right.  Nevermind what kind of speakers or amps. The problem was a Phase Lag   How do you do to fix this.

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Be Smart Never Assume
Improvise Adapt and Over Come
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Installer/Technician 20 years



Replies:

Posted By: forbidden
Date Posted: February 03, 2004 at 9:41 PM
Describe the problem a little better, I have not heard the term used before.

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Top Secret, I can tell you but then my wife will kill me.




Posted By: maddhatTer123
Date Posted: February 04, 2004 at 1:23 AM
are you using multiple 2 or 4chl amps, are the rca's different brands, lengths?, what head unit, same brand equipment.

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THE INSTALLER HAS SPOKEN




Posted By: staudio
Date Posted: February 04, 2004 at 5:16 AM
Phase lag.... wow thats when sound is reaching the listener at a different time. Solving a problem like that in a system as big as your describing could be difficult. I've never delt with a problem like this before but my assumption (yes I may be making an ass of me and you) is that you must set all of the divers an equal, or close to equal, distance from the area of indended listening. Anyway having had no experience with this, this is all the information I can provide, hopfully an older pro knows something more of this problem. Good luck

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Posted By: DYohn
Date Posted: February 04, 2004 at 11:07 AM

Correcting phaseing problems inside a car is very difficult.  You have to add DSP time-domain alignment circuits (time delays) to adjust the relative timing between the various drivers.  This is very time consuming and requires significant electrical engineering ability to design yourself.  You are in Bob Carver's field of psycoacoustics now.  An even bigger problem in a system like you describe will be phase problems cause by reflections and cabin gain, rather than those caused by the actual timing from one driver to another.  As wattage increases, the acoustic cancellations from reflections inside a small enclosed space become a bigger and bigger problem, especially if you are using long-throw drivers.  Near-field monitor designs have fewer such problems, but then you wouldn't push those with 4K watts, nor would you use them in a car... 

The best thing you could probably do is install some good quality DSP processors with either Dolby AC-3 or THX parameter compliant capability (like those with a Motorola DSP-560001 chip) and use them to digitally adjust your time alignments, rather than try to design and build something yourself.  I could suggest some equipment for home or theatre audio, but I'm not familiar with available car audio equivalents.  Look for DSP gadgets!





Posted By: bberman1
Date Posted: February 04, 2004 at 11:23 AM
You may want to look into the new Audiocontrol DQX https://www.audiocontrol.com/MobileAudio/Products/Digital/DQX.html 




Posted By: Julian59
Date Posted: February 04, 2004 at 12:03 PM

PHASE LAG

   Phase Lag is a term first expained by a Tech that worked for Rockford Fosgate in the mid 80s.

On speaker systems where the woofer and midrange speakers are separated by more than a couple of feet, the travel time of sound through air can produce what is called a PHASE LAG  leading to cancellation .  For the reason On any installation (even with other than 12 db crossovers) try reversing both woofer phases. In almost all cases bass will be mush tighter with woofer reversed.

When a high and low-pass pair of 12 db/octave filters are used, Cancellation  can be avoided by one simple step:

Reverse the woofer phase by reversing the wiring to the + and - terminals. Reversing the woofers has the effect of putting the woofer and midrange back in phase at the crossover frequency, to compaensate for the crossover's phase reversal. Some high end Amplifiers use this feature a 12 db/octave active crossovers, and are wired to use this reversal technique.

These considerations also apply to midrange-to-tweeter crossovers, although usually the problems introduced are less audible. The cure is the same, but applied to the tweeter. Reverse the tweeter phase by reversing the + and - terminale

In General , the acoustics of Auto and the variations of speaker placement can produse a variety of unexpected cancellations. Where possible, experiment with speaker phasing by comparing the sound of the system with in-phase and reversed woofers and /or tweeters to find the smoothest sounding connections.

Avoid Cancellation

Thank You

Julian59



-------------
Be Smart Never Assume
Improvise Adapt and Over Come
=============================
Installer/Technician 20 years




Posted By: forbidden
Date Posted: February 04, 2004 at 1:16 PM
I second bberman, a delay circuit (I think someone mentioned DSP) should do the trick for you, I also would recommend the new Audio Control processor. I can't remember if the old Rockford symmetry piece addressed this or not.

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Top Secret, I can tell you but then my wife will kill me.




Posted By: Teamrf
Date Posted: February 04, 2004 at 6:22 PM
I like Rockford Fosgate...Lol didn't mean to get off topic...just wanted to comment on RF.

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~The Rookie~
Rookie of the year that is...
Don't let the smoke out of your equiptment..it doesn't go back in.




Posted By: Alpine Guy
Date Posted: February 04, 2004 at 9:53 PM
By an alpine deck with time corection posted_image lol




Posted By: ccroadshop99031
Date Posted: February 10, 2004 at 10:23 PM
have to love the alpine cda9813 with time correction





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