A few years back I put together some random notes I had kept on how to set up a stereo system and I posted on the Tacoma World forum I used to frequent. (Note: if I plagiarize without credit due, please forgive, it's been a while). Some ideas may be wrong headed, some may be my personal opinion, but I offer them for anyone trying to get really good sound but not knowing how to proceed (without throwing excessive amounts of money at it). I apologize for the length - and multiple posts (wouldn't all fit in one) - and do welcome updates, critiques, etc.
********* Begin Lee's treatise on stereo originally on Tacoma World *******************
One of my kids asked me about how I went about setting up a car stereo system. So, I pulled together some notes I've written to myself over the years (gathered from many sources that I failed to track and therefore sadly cannot credit - hope I am forgiven) - trying to describe in one place a "basics" course on how to accomplish audio tuning in the mobile environment.
Based on how big this document turned out to be, I may not be offering all that much of an easy solution to TW, but I'm posting in the hopes it helps one or two people anyway.
Disclaimer: I honestly have doubts about my skills to do this, especially given the knowledge I see from several of the members. I'm not a musician, I'm not an acoustic engineer, I'm not a sound professional, but I am an enthusiastic listener. I've learned some things in the 42 years since I installed a system in my 1st car, and I've been forced to discard things I "learned" that turned out not to be true – and who knows how many falsehoods I'm still harboring. I also lack experience in the Tacoma - what works, what doesn't in terms of specifics. Finally, I'm not even a particularly good writer - so please critique & comment.
I hope to cover the steps below in this thread. How each step is accomplished is somewhat gear dependent, and I'll do my best, but see the disclaimer paragraph above.
0. Preface
1. Eliminate system noise
2. Check speaker polarity/phase
3. Start with a clean signal
4. Setting Gains/smoothing frequency response
5. Equalization
0. Preface
As in any good project, a baseline/starting point has to be established, so:
a) There is no substitute for attendance at live concerts, preferably by a great musical ensemble in a great environment (what I mean here is NOT along the lines of attending the early Beatles concerts held in baseball stadiums). As trite as this might sound, you need to know what music is supposed to sound like. You are best served by hearing music in an un-amplified environment. That way you learn what an instrument should sound like, not what a sound engineer thought should come out of a loudspeaker.
b) You should find a well recorded CD from an artist of your choice and listen to it. This should not be done on the OEM stereo, nor with some MP3 rip-off. It should have decent dynamic range (not overly compressed) and preferably contain a wide variety of instruments in type and frequency range (including male & female vocals). Play it on a high-end home audio system. If you can't afford that (I can't), then get the best set of headphones you can lay your hands on. Listen to the system with the all the bells & whistles set for "flat" output. Listen over and over until you know the recording by heart - this will allow you to recognize "faults" in the system you will be installing/tweaking.
c) Now that you know what a system should sound like, use your budget wisely and from a total system perspective to acquire what you think sounds good - after all it's your money. I tend to spend my $$ roughly in thirds (headunit, speakers, amplifiers), but YMMV.
Finally, I sincerely hope this doesn't come across as pretentious on my part - I hope other knowledgeable forum members would be kind enough to jump in advance this discussion.
1. Eliminate System Noise
The goal here is to eliminate 100% of the noise - basically something that can’t be done - but it's a goal, so we do our best (and hope for the best). What is noise? In a vehicle audio system, there are many potential noise sources, I’ll try to explain a few (source noise, thermal noise, induced noise and ground loops) and concentrate on those that respond to treatment.
Source noise. Source noise comes from the source (duh!), and the only treatment is to use a different source. Source noise includes things like a weak FM signal (listen to another station), bit jitter in the production run of a CD (buy a different CD), etc. A real-world example would be the CD of David Crosby’s " If I Could Only Remember My Name". The original master tape (and vinyl record) contained a fair amount of hiss. When the recording was moved to CD, a decision was made to not attempt removal of the hiss. The only treatment is to use a different source but none is available so this noise we must live with to listen to this music.
Thermal Noise. Thermal noise wouldn’t be a problem if we were willing to live at absolute zero (last time I checked that was -459 degrees Fahrenheit so I think even my Canadian friends - that visit Florida in the winter - would think it too cold). Thermal noise sounds like the hiss that you hear between stations on FM radio and in simple terms exists due to the random movement of electrons caused by heat. Since many of us seem to prefer existence somewhat near +70 degrees F, all we can do is hope the manufacturer of our equipment exercised careful design, then we can apply a little attention to detail in hopes of minimizing this type of noise. That detail would include ensuring adequate heat ventilation of the headunit, amplifier, etc. As a side benefit, the equipment should have a longer life with proper ventilation. Remember, the goal is minimize, it can’t be eliminated.
Induced noise. Induced noise has numerous causes, many of them somewhat insidious. Sometimes it sneaks into your system through the power wiring, or it might sneak in via wires placed too closely together. Hey, it can even get in through the air, but the biggest problem occurs due to power wiring and signal cables.
We all know our trucks are battery powered and a battery is a pure DC source right? Wrong (at least in our case). Although the point can be argued (a little), our trucks are alternator powered, and the electrical system is a nasty environment for electronic equipment. The alternator outputs high-current pulsating DC into the battery, which then shows up everywhere else in the electrical system. When it becomes induced noise it sounds like a whine whose pitch is proportional to engine speed. Courtesy of Mr. Michael Faraday, we know that if you put two wires in close proximity to each other, and one of them is carrying an electric current, you generate electricity in the other by a) moving one of the wires relative to the other, or varying the electric field. Since the alternator (notice the name) puts out alternating current, we have a case of varying electric field inducing noise current in nearby wires. Imagine the “receiving” wire as the RCA cable from the head unit to the power amplifier. Describing how to diagnose this problem would be long and involves things like muting plugs (a follow-on post?). This problem usually exhibits itself as a one over R squared phenomenon (doubling distance results in 4-fold noise reduction, so rerouting the cables away from other wires is the traditional method of attack). I found this out the hard way on a 2002 MR2 Spyder when I initially ran RCA cables under the sill panel at the driver’s side (left) door and found bad, bad alternator whine. I fixed it by running them down the passenger side door (note: I retained the run of power, ground, and remote turn-on wires down the driver’s side). As an aside, I use a set of StreetWires RCA cables that have little directional arrows printed down the length of them. I know of no scientific reason why the electrons would like to go one way versus another down the wire, but I sleep a lot better knowing I ran them with the arrows pointing from the headunit to the amplifier. YMMV, feel free to be a rebel.
EMI. The other (major) source of induced noise is electromagnetic interference (EMI). In this case, the EMI functions as the transmitting station, the sound system’s wiring becomes an antenna, and the amplifiers within the system become the receiver(s). To each their own, but that station doesn’t play my kind of music. Some examples of EMI are ignition noise (like using solid core ignition wires vice suppression core), or even a loud buzz that you might hear if you drive near a television transmitter, electrical power station, under powerful fluorescent light systems, etc. The solution here is to encase the system in a Faraday cage or otherwise use technology smartly in an attempt to minimize this. That’s why the HU is in a metal case, signal cables are shielded, professionals use balanced line systems, etc.
Ground Loops
Ground loops are nasty things. I used to work in a lab that had about 50 rods driven deeply into the ground over about an acre outside that hooked up to the electrical power system and we still had ground loop problems inside with some sensitive lab equipment. They are caused by the non-zero resistance of the wire/vehicle structure used in interconnecting the equipment. Typically, ground loops are created by a system (like a headunit and amplifier) having multiple connections into the grounding system. In vehicles this problem is made worse by assuming that all points in the metal frame make for a good ground. They do work as an effective ground for things like cigarette lighters and tail lights, but not so good for audio. The alternator in the battery charging system makes things worse because the frequency of its AC output (that’s why it’s called an alternator, not a generator) is within the audible range. The low impedance involved (high available current means low impedance) make filtering out alternator noise even more difficult. So, these voltage drops occurring between the various grounds in the body usually have alternator noise riding on them, which gets into an audio system via a ground loop. Fortunately, the solution is easily described and not too hard to implement. Find a place on the body (preferably near the amplifier since it has the most electrons scurrying about) and bring the grounds of all the electronic devices (except the speakers) to that spot. Secure the collective ground(s) to the body & voila problem fixed. And by secure them to the body I don’t mean through layers of paint or other insulator. If you can’t find a place for good clean metal to metal body connection you may have to sand down to bare metal, drill and fit a bolt/nut- with washers on both sides, attaching the ground through the use of wiring lug.
********* Begin Lee's treatise on stereo originally on Tacoma World *******************
One of my kids asked me about how I went about setting up a car stereo system. So, I pulled together some notes I've written to myself over the years (gathered from many sources that I failed to track and therefore sadly cannot credit - hope I am forgiven) - trying to describe in one place a "basics" course on how to accomplish audio tuning in the mobile environment.
Based on how big this document turned out to be, I may not be offering all that much of an easy solution to TW, but I'm posting in the hopes it helps one or two people anyway.
Disclaimer: I honestly have doubts about my skills to do this, especially given the knowledge I see from several of the members. I'm not a musician, I'm not an acoustic engineer, I'm not a sound professional, but I am an enthusiastic listener. I've learned some things in the 42 years since I installed a system in my 1st car, and I've been forced to discard things I "learned" that turned out not to be true – and who knows how many falsehoods I'm still harboring. I also lack experience in the Tacoma - what works, what doesn't in terms of specifics. Finally, I'm not even a particularly good writer - so please critique & comment.
I hope to cover the steps below in this thread. How each step is accomplished is somewhat gear dependent, and I'll do my best, but see the disclaimer paragraph above.
0. Preface
1. Eliminate system noise
2. Check speaker polarity/phase
3. Start with a clean signal
4. Setting Gains/smoothing frequency response
5. Equalization
0. Preface
As in any good project, a baseline/starting point has to be established, so:
a) There is no substitute for attendance at live concerts, preferably by a great musical ensemble in a great environment (what I mean here is NOT along the lines of attending the early Beatles concerts held in baseball stadiums). As trite as this might sound, you need to know what music is supposed to sound like. You are best served by hearing music in an un-amplified environment. That way you learn what an instrument should sound like, not what a sound engineer thought should come out of a loudspeaker.
b) You should find a well recorded CD from an artist of your choice and listen to it. This should not be done on the OEM stereo, nor with some MP3 rip-off. It should have decent dynamic range (not overly compressed) and preferably contain a wide variety of instruments in type and frequency range (including male & female vocals). Play it on a high-end home audio system. If you can't afford that (I can't), then get the best set of headphones you can lay your hands on. Listen to the system with the all the bells & whistles set for "flat" output. Listen over and over until you know the recording by heart - this will allow you to recognize "faults" in the system you will be installing/tweaking.
c) Now that you know what a system should sound like, use your budget wisely and from a total system perspective to acquire what you think sounds good - after all it's your money. I tend to spend my $$ roughly in thirds (headunit, speakers, amplifiers), but YMMV.
Finally, I sincerely hope this doesn't come across as pretentious on my part - I hope other knowledgeable forum members would be kind enough to jump in advance this discussion.
1. Eliminate System Noise
The goal here is to eliminate 100% of the noise - basically something that can’t be done - but it's a goal, so we do our best (and hope for the best). What is noise? In a vehicle audio system, there are many potential noise sources, I’ll try to explain a few (source noise, thermal noise, induced noise and ground loops) and concentrate on those that respond to treatment.
Source noise. Source noise comes from the source (duh!), and the only treatment is to use a different source. Source noise includes things like a weak FM signal (listen to another station), bit jitter in the production run of a CD (buy a different CD), etc. A real-world example would be the CD of David Crosby’s " If I Could Only Remember My Name". The original master tape (and vinyl record) contained a fair amount of hiss. When the recording was moved to CD, a decision was made to not attempt removal of the hiss. The only treatment is to use a different source but none is available so this noise we must live with to listen to this music.
Thermal Noise. Thermal noise wouldn’t be a problem if we were willing to live at absolute zero (last time I checked that was -459 degrees Fahrenheit so I think even my Canadian friends - that visit Florida in the winter - would think it too cold). Thermal noise sounds like the hiss that you hear between stations on FM radio and in simple terms exists due to the random movement of electrons caused by heat. Since many of us seem to prefer existence somewhat near +70 degrees F, all we can do is hope the manufacturer of our equipment exercised careful design, then we can apply a little attention to detail in hopes of minimizing this type of noise. That detail would include ensuring adequate heat ventilation of the headunit, amplifier, etc. As a side benefit, the equipment should have a longer life with proper ventilation. Remember, the goal is minimize, it can’t be eliminated.
Induced noise. Induced noise has numerous causes, many of them somewhat insidious. Sometimes it sneaks into your system through the power wiring, or it might sneak in via wires placed too closely together. Hey, it can even get in through the air, but the biggest problem occurs due to power wiring and signal cables.
We all know our trucks are battery powered and a battery is a pure DC source right? Wrong (at least in our case). Although the point can be argued (a little), our trucks are alternator powered, and the electrical system is a nasty environment for electronic equipment. The alternator outputs high-current pulsating DC into the battery, which then shows up everywhere else in the electrical system. When it becomes induced noise it sounds like a whine whose pitch is proportional to engine speed. Courtesy of Mr. Michael Faraday, we know that if you put two wires in close proximity to each other, and one of them is carrying an electric current, you generate electricity in the other by a) moving one of the wires relative to the other, or varying the electric field. Since the alternator (notice the name) puts out alternating current, we have a case of varying electric field inducing noise current in nearby wires. Imagine the “receiving” wire as the RCA cable from the head unit to the power amplifier. Describing how to diagnose this problem would be long and involves things like muting plugs (a follow-on post?). This problem usually exhibits itself as a one over R squared phenomenon (doubling distance results in 4-fold noise reduction, so rerouting the cables away from other wires is the traditional method of attack). I found this out the hard way on a 2002 MR2 Spyder when I initially ran RCA cables under the sill panel at the driver’s side (left) door and found bad, bad alternator whine. I fixed it by running them down the passenger side door (note: I retained the run of power, ground, and remote turn-on wires down the driver’s side). As an aside, I use a set of StreetWires RCA cables that have little directional arrows printed down the length of them. I know of no scientific reason why the electrons would like to go one way versus another down the wire, but I sleep a lot better knowing I ran them with the arrows pointing from the headunit to the amplifier. YMMV, feel free to be a rebel.
EMI. The other (major) source of induced noise is electromagnetic interference (EMI). In this case, the EMI functions as the transmitting station, the sound system’s wiring becomes an antenna, and the amplifiers within the system become the receiver(s). To each their own, but that station doesn’t play my kind of music. Some examples of EMI are ignition noise (like using solid core ignition wires vice suppression core), or even a loud buzz that you might hear if you drive near a television transmitter, electrical power station, under powerful fluorescent light systems, etc. The solution here is to encase the system in a Faraday cage or otherwise use technology smartly in an attempt to minimize this. That’s why the HU is in a metal case, signal cables are shielded, professionals use balanced line systems, etc.
Ground Loops
Ground loops are nasty things. I used to work in a lab that had about 50 rods driven deeply into the ground over about an acre outside that hooked up to the electrical power system and we still had ground loop problems inside with some sensitive lab equipment. They are caused by the non-zero resistance of the wire/vehicle structure used in interconnecting the equipment. Typically, ground loops are created by a system (like a headunit and amplifier) having multiple connections into the grounding system. In vehicles this problem is made worse by assuming that all points in the metal frame make for a good ground. They do work as an effective ground for things like cigarette lighters and tail lights, but not so good for audio. The alternator in the battery charging system makes things worse because the frequency of its AC output (that’s why it’s called an alternator, not a generator) is within the audible range. The low impedance involved (high available current means low impedance) make filtering out alternator noise even more difficult. So, these voltage drops occurring between the various grounds in the body usually have alternator noise riding on them, which gets into an audio system via a ground loop. Fortunately, the solution is easily described and not too hard to implement. Find a place on the body (preferably near the amplifier since it has the most electrons scurrying about) and bring the grounds of all the electronic devices (except the speakers) to that spot. Secure the collective ground(s) to the body & voila problem fixed. And by secure them to the body I don’t mean through layers of paint or other insulator. If you can’t find a place for good clean metal to metal body connection you may have to sand down to bare metal, drill and fit a bolt/nut- with washers on both sides, attaching the ground through the use of wiring lug.