Car Audio Faq

[zpeedy mclovin]

well people i really like this forum and i would like to share a small guide that i made with the knowledge that i have if you have some extra stuff let me know to add it since im not the car audio GOD but i still know alil bit

Hi, before reading or taking any info from the write up I made, please include that im not responsible for any troubles or problems/mistakes you make. And if your sharing this info go right ahead and please include or give me props for this write up.

Part 1

What’s a good install????

when u say have a good install means having a good installed system..

and a system it doesn’t mean sub +box + amp

first its the signal(head unit)

enclosure

speaker(s)

the car that is the system in and how the box its made its really important since the sub and box and car will act like a band pass box. and here is what the cabin gains comes in place

amp(having a clean system)

charging system(power) also good ground.

no leaks in the box ( i should have this on enclosure but its mainly a tip).

dampening material.(very important but not needed if you just have a small subwoofer system and stock sound system )

signal+charging+speaker+enclousure+car+amp=system

screwing one of the elements can cause really catastrophic results on you sound.

for example:

if u have air leaks it will sound bad as hell.

if u have bad charging system it will produce a clipped signal from the amp and will never push full power from the amp and probably damage your subs.

if u have a bad or weak signal the amp will never push the power it needs to push and will be weak to clipping

if u make a box that its designed to other car it will generates cancellation causing poor performance and major spl loss..

there’s a million things to check for a good install but experience its the best friend.

Part 2

Tips on building a enclosure.

On building boxes there’s a lot of controversies of tastes on enclosure so it got divided into two categories: spl and sq.

Spl: means that it creates a lot of pressure from the driver making louder sounds. But sometimes it can cause peaks and unbalance of the driver causing the actual reproduction to disappear or change causing distortion.

Sq: means sound quality and it mainly means that the the set up for sq will try to reproduce all the sounds the artist intended to be heard without any distortion added and great frequency extension and a flat response to avoid any peaks.

Box tuning: on ported boxes u always have to using the tuning. The tuning is for tuning on what type of music do you want out of the driver. For spl applications its mainly higher tuning boxes ( 38hz and up) for sq is mainly for lower tuning boxes ( 28-38hz)

If you really want to get the most out of sound u don’t have to go lower than 28hz, going that low its worthless because : most songs don’t go lower than 34hz and in a car 28hz its not used. On home theater is another story since sometimes u need to clearly reproduce a 15hz tone like a step of a dinosaur but in car audio going lower than 28 hz will never help but only hurts the output of the driver.

Tips on spl sub boxes:

Try to use an average of the recommended space obtained by your subwoofer manufactures . or try to use 10-20% less space depending on the cabin application, from there you will have to try to use the most area of port as possible. On spl box tuning its very confusing because the car is the place where the sound takes place, most cars tend to peak at around 50hz, some cars like the crx’s tend to peak up to 60hz, some explorers tend to peak at lower frequencies around 45hz .

Building a enclosure to get optimal results doesn’t happen at the first try. U have to first take a look at the cabin or car that is going to. The cabin or the car is an acoustic chamber than when u place or drop your box there the car and sub will act like a band pass box since there’s already one chamber ( the cabin of your car) and the last chamber will be your box

Tips on Sq boxes:

On sound quality applications your mainly goal is trying to achieve the maximum flat response and without any defects of the original recording or distortion.

On Sq boxes you will have to use around 10- up to 45% more volume or space that your manufacturer recommends. Why??? A bigger box compared to a small box will tend to give you deeper bass or lower frequencies extension, and a bigger box tends to decrease most of the peaks gained in the cabin.

You will have to tune at around 28-35 hz… keep in mind that some subwoofers are made to be more of a spl sub than a sq sub. In that case the optimal tuning is 35hz, going lower will never help the sub since the sub is not capable of handling that low frequencies and even at that low will reproduce unwanted peaks depending on the driver. Going lower than 28-24 hz in car audio like I said before will never help or give any results in fact will decrease your driver output and not helping to get an more frequencies extension..

To create good response and better air flow inside the box try to use aero ports( they add up to 3 dbs when used property when compared o regular ports) try and use the golden ratio. The golden ration is based on the Greek golden rectangle for the perfect rectangle. The golden ration is a lil hard to use on car audio but if used its very helpful and is common used on home theaters.

Part 3

Tips of finding your special subwoofer taste:

Not all the subs are the same if we took out loudness or spl.

Some drivers are different that others. Some driver can reproduce a 16 hz note without any distortion some drivers cant do it.

Spl: some specs and information you want to look for spl will be a stiff spider since is what helps the subwoofer move without bottoming out. A flexible surround, a low weight cone to increase efficiency, a big surface area to move some air.

If your going with the big boys you will have to look for higher power handling, great cooling option if you are going into high powered systems and a high power coil and a anodized coil for better thermal management. And finally on a spl sub will always be less xmax compared to a sq sub a high efficiency ration ( or spl typically good efficient subs are up to 90 dbs at 1 watt/meter) and a lil bit high Fs rating above 35hz.

Sq: some specs to help you find out a good sq woofer is mainly a stiff suspension, a low Fs rating, a high xmax ( is the one of the main things u can see a woofer going lower than the other since to make a tone one octave lower than a specified it needs up to 3 times more xmax to reproduce that tone) an oversized back plate so it can allow the woofer more excursion without bottoming out, a extended pole piece to extend the linear magnetic field for the woofer,

Some specs or info can be shared for both applications and are really important like a rigid frame so it can avoid unwanted resonance noise that some cheap frame make, a food Bl rating for good linear and magnetic field.

There’s a t/s parameter that I been inspecting that most of the companies avoid it and is VERY important on getting the right enclosure and is called EBP or efficiency bandwidth product. And is a rating that helps a box builder determine if the driver is suited for ported, sealed or both applications, EBP less than 45 it should be used in sealed and between 45-65 it can be used in flexible applications, over 65 means the sub is mean to be in ported applications.

There is always a way to find out about this.. and me Roberto Rosales A.K.A many names will tell you  ebp can be found like these EBP=Fs/Qes.

Keep in mind that EBP is not 100% accurate but is very helpful that’s why some companies avoid to use this parameter.

Part 4

Building an enclosure and calculating volume:

To begin with if your making your own box first u have to make sure all the walls are properly mounted rigid and invulnerable to flexing when is subject to high pressure. On I suggest using ¾ mdf fiber board or birch and of course internal bracing. The enclosure should be glued together and supported by screws or nails.

Calculating volume: when calculating volume is juzz measuring the dimensions of the box in inches or whatever do you use as your metric system.

Box volume=(height)x(width)x(depth) and then divided by 1728. this will give you the volume of the box in cubic ft.

If two facing sides are uneven length add them together and divide by 2 to take the average.

Subwoofer cross over:

There are two types of crossovers the passive and active. Passives are mainly coils and conductors between the speaker leads between the amp and speaker/ the active crossover is an electronic filter which separates the audio signal to give to different amps. For better performance I use and recommend use a active 80-100hz low pass crossover with 12db/octave and depending on your set up crossed from 60-100 hz.

Part 5

Problems/troubleshooting:

If u or any of your friends are having trouble with your system, like distorted or loss performance or even lost sound after installing your system. You can do these steps I recommend for identifying your problem and even fix it.

If you have any distorted sound or lost or u lose performance or rattling bad form your subs, u first have to check the connections running from your amp to your box and from your box to your sub. Then u will also want to make sure no wires are loose.

If the first step did not solve the problem, check your enclosure for any leaks, crack or broken pieces, any lost of structural damage of the enclosure can cause very dramatic performance lost and distortion.

If still doesn’t work try to check your speakers for any burned leads, or separated components or even unsoldered terminals, u can smell something burning when a sub blows or is acting bad. But hey sometimes when u play your sub too much they will start to heat up and sometimes this is normal but also caused by clipping too.

If none of the steps I told you to do you will want to start looking in other electrical components in the vehicle such as damaged alts, batteries power and ground wire, and any connections, and start by checking first your head unit or other processors u might be using. Some problems can even be cause by a special function of your head unit.

Still doesn’t work??? Try using a dmm and check the ohms of each coil.. and make sure it has good readings then keep checking your electrical stuff and test it one by one. If something wrong u might also want to contact your manufacturer.

Part 6

Size really matter???

Ummm yes but at the same time no, as you know there are people that make a 10 inch sub hit in the mid 150’s in spl competitions. A lot of people say hey a 15 inch have more cone area than a 10. that is a true fact but on cone but you don’t just need cone area. The volume displacement is a better fact than just the cone area too look at. Or a 18 inch pyramid sub will move more air than a 10 inch professional audio woofer??? No right. (unless is the same model )

Anyway a good thing to look at if you want an idea to get loud will be to look at the drive volume displacement. And to get this you simply have to multiply the Sd(effective cone area) x xmax(the linear electrical movement of the driver)= volume displacement(how much air does the sub move.)

On the sq hand. Going bigger is a good thing since increasing the surface are allow the woofer to really hit deeper or get a lil lower but it has disadvantages like response. A 10 inch is always faster and have better response than a 18 inch with same motor. Sometimes that fast response have a good sound not muddy but punchy that some people like to hear that’s why is always better to have a combination, and the ideal woofer size is 12-15 inches.

In my opinion try to use a woofer between 12-15 inches of diameter if you cant use this large try getting a nice 10 inch sub. If you have a real big car like an SUV you will have to get bigger sub a 15 is a good choice or a 18 inch. If you have a really small car like a mini cooper a 10 inch or a 12 will be plenty.

Part 7

Is the rms the main or best thing on the woofer???

If you really want to get loud and want to find a easy to get loud sub read my chapter 3 on tips of finding a spl sub.

Anyway a lot of people says rms is the king of specs and is the true thing to check if the system is loud. rms is like the horsepower in car audio, but just having the horsepower you know how fast a car is??? No right??? That’s why rms is not the main fact to see if a woofer gets really loud. For example you have a 1000 hp engine. The engine goes to the tranny and then to the differential and at the wheels it probably lost about 200 horses. Take those horses and put it in a SUV check how fast the SUV is and take the engine out and put it in a small car, then you will see that in the car the engine is faster. In car audio that’s the same. Like look at the motor of the sub is like an engine, if you put a stiffer cone and good stiff suspension it will be louder than a heavy cone with rough suspension. That’s why as I stated in chapter 3 there you will find how to get a nice suspension with a great motor.

Never in your life use max wattage…. Max wattage is only something they refer as power handling in a woofer or amp for a short burp( maybe 1 second 2 second max or even less making it worthless in car audio but is still being used)

On car audio there’s always cheaters. Sometimes good cheaters and sometimes bad cheaters. Like take for instance the wattage rating. Some companies overate their product to improve their sales, for example you see a lot of companies saying they have the best subwoofer, and is in fact a lie. They say 1000 watts (but they don’t tell you that’s max) sub in bold letters making it the main thing about the woofer and max or rms is not a big thing of seeing a sub can do, sometimes overrated products add things or cheat on their products to boost their sales like they have a 600 rms sub and they say hey lets add another 200 watts and what thing they are adding to the woofer is distortion. In amps they add more watts like they have a 1300 amps they are “why not make it into a 1500 watts without doing nothing??” this is what a overrated companies is. And u can see this by buying cheap equipment (sometimes there are cheap products that are also underrated instead of overrated). Some companies underrate their stuff to make them perform better and to avoid a lot of problems. Some companies just add free watts to have their name known.. and is a good thing but they put the free watts on the price. So don’t say hey my 1300 watts amp is really pushing 1500 watts just like your 1500 watts amp and you don’t clearly see that both amps cost the same or maybe your 1200 watts amp is more expensive than the 1500 watts your friend have.

Part 8

Clipping

Clipping is mainly our worst enemy in car audio, clipping is what mainly causes speaker and amp failure and bad performance, clipping is an unwanted thing, the cause of clipping is mainly poorly charging system, since you need power to make power, so if your are getting power and turn into a bigger power is not possible, sometimes some amps are invulnerable to clipping, and if you have a 80 amps current flow they take the 80 amps and produce it into what is equivalent to 80 amps of power without any stress, is mainly because they have a regulated power supply. Some amps without this feature take the 80 amps of current flow and try to make a bigger output power and they fail by sending dc current to the driver making it perform bad and even kill it.

You just cannot detect clipping by just the ear, sometimes clipping is unhearable and you cannot detect it by ear, sometimes you think your system is clipping but is not, the only thing to see if your system is clipping is having an oscilloscope a clamp meter and perform various task to find out if your system is really clipping. Most people mistake clipping with a spl sub that their nature is to get loud and not sound good at all.

Clipping is also and mainly caused by higher gain setting on your amp, so try to set your gains with a voltmeter, there are some websites with calculators to help you out. A bass boost can increase clipping, when you use the full 16 db that the amp give you and that’s bad, if your are using bass boost is a good thing to use but never try to go more than 6/10 of bass boost if you are not competing.

Some times instead of you having clipping u might have a really high t.h.d ratin( or total harmonic distortion)

Part 9

What to look for an amp.

For an amp try to look for good capacitance banks, and double sided boards beefy power supplies and good mosfets that can really handle their power ratings. And try to get a regulated power supply if you don’t have the charging.

You will also want to look for low THD ratings. THD is total harmonic distortion and is mainly a spec that can tell you how the amp will alter the original recording reproduction by adding distortion.

Look higher power rating if your having this amp for subwoofers and can be stable at you desire impedance load.

NEVER get an amp because of their Max(or dynamic power) rating, is the manufacturer only give the Max rating. Try using the root mean square spec to get the rms..

When they only give you max, try to multiply it by .707 which is the root mean square.

Lets say you have an amp that the max rating is 1000 watts max, and you want to find the rms. Well take the 1000 x 0.707 = 707watts rms this is a basic formula on hwo to get a basic idea of the rms output of your amp.

A good thing for an amp is a good clean thermal friendly heat sink, a fan is always a plus, heavy gauge wire connections a strapping capabilities is also helpful.

Part 8

Is Fs the main parameter that can tell me how low my sub will go??

Ummm no really, Fs is just the frequency of resonance for a driver in FREE air( in other words the frequency that it vibrates the most). Not in a car, not in a box, in FREE air, or like the sub out of the box outside of the car.

When you put the woofer in a box, the Fs can dramatically change or stay the same(since Is not in free air no more ), sometimes will be a slightly change sometime will never happen, put the box with the driver in the car and will change again, so don’t just go for a lower Fs or try to look at my chapter 3 where I explain on how to find a Sq sub.

Sometimes if a woofer is not designed well if you play a tone that is lower than the Fs the woofer will act like it was not a box at all, some woofer will only do this on the frequency of the Fs.

Some spl sub have really high Fs since forr main spl competition they use 40hz+ tones and they use woofers with Fs in that range so they can vibrate the most at those frequencies.

Part 9

Is the bigger the magnet the better???

Another big NO. magnet is not a big factor of how a sub can play. There are some magnets that are up to 75% smaller than rationally magnets and offer up to 3 times more magnetic strength. ( some of them are not used in commercially available products since they are known that are bad for us)

There’s the neodymium magnet, and is a magnet that is upto45% smaller and offer up to 2.5 times the magnetic strength, but using the same size of this kind of magnet as with a rationally magnet size will make the woofer motor. To really have high motor strength that instead of increasing the sound it will decrease, go out of control, have a lot of problems etc…

If your in the market of a woofer and want a neo magnet theres bunch of companies selling products with this kind of magnet but just have in mind that if u use this magnet be careful this magnets are so strong that sometimes overpowering them they tend to cause really high tempetures causing the woofer motor to go bad, and if u overpower them you can also damage the speaker since the extra power will make the motor bottom out and maybe blow the speaker. This kind of magnets causes a lot of troubles in speakers that’s why not all companies use them and are really hard to work with.

Part 10

Front or back stage or both???

From my technical view you will have to try to focus on the front stage, since it will be the main space where you will be spending time hearing the sound.

Always try to get a good components in the front, if you can you can install another set on components in the front on kick panels to get better imaging, and worry a bout rear stage later.

So no back stage??? If you are in a budget try to focus on the front stage and worry about back stage like I said before. But really try to get the back stage done, since you will feel an empty spot in your sound, a rear stage can really improve the sound on your music, making it sound FULL and RICH. And 1 speaker alone will not produce all the full sound not even 2 or 4 on components ( 2 mids and 2 tweeters) but 2 pairs or back and front stage will always sound much better .

Part 11

Amp or no amp for front and back stage or aftermarket speakers.

If you are upgrading to aftermarket speakers and amp is a MUST,

A single head unit will never provide the power for the aftermarket speakers, it will never send proper electrical power to them, and will cause really high distortion and clipping. Most of the aftermarket speakers are meant to be used with at least 40 watts rms for each speaker and the head unit will simply provide that kind of power and without that you will be sending weak signal damaging your speakers. And the only thing the head unit will provide is high amount of THD or high distortion..

With a amp to power your aftermarket speakers yoru system will have the ability to recreate a better imaginary stage, and a good set up will easily make the stage to seem close to the actual height ,width ,and depth of the actual performance stage the audio was recorded to. And your speaker will really make the music as if you had the artist playing in front of you.

And have in mind that almost ALL aftermarket speaker were designed to use with aftermarket amps.

Part 12

How do I set my cross overs.

Is really simple. Lets start with the small door speakers. First you will have to see your speakers frequency response.

Frequency response is mainly a reproduction of the audio signal, that shows the average reproduction range of the speaker or the range of the output the speaker can produce and is mainly stated like 40-20,000hz where 40 hz it’s the lowest the speaker can reproduce without causing distortion, and is the same with the 20,000.

If your speakers says that they are 40-20,000hz you will have to cross your system at around 60hz, try using around 10-20 more hz to cross your speakers. And you will have to do these with all the speakers you have or you wanted to be crossed. Keep in mind that a single speaker will never reproduce all the frequencies. That’s why we need different speaker to do different jobs like mids tweets and subs.

If you want to cross your subwoofers, first you have to take a look at how you crossed your door speakers first, a subwoofer can reproduce sometimes sound up to 150hz easily they can get up to more but will be sometimes inaudible or unnoticeable, ok now if lets say your crossed your door speakers at 60 hz you will have cross your sub at that frequency to pass the frequency response from the speakers to the subs. For example the door speakers will handle the 20,000-60hz and on 60 hz will be crossed, then the woofer is crossed at 60hz it will start from there and handle the lower frequencies.

Subsonic filter what???

Subsonic filter is mainly a filter or kind of like a crossover to filter out really low frequencies that can really damage your speakers specially if you are using a ported box. If you have a subsonic filter with a dialer try to set it 5 hz lower than you tuning on your ported box, or if you don’t know the tuning of your box or have a sealed box try to set it at 25hz since most speaker will reproduce a 20hz tone,

Part 13

Ground???

Ground is mainly a point that has zero voltage.

The single and most important factor to avoid high resistance or better flow of electricity and avoid unwanted noise is finding a good ground

A bad ground can cause clipping, or severely damage your amp and cause to shorten its life.

On head unit the regular ground from the wiring harness is not always enough try to find a better ground so you will never have problems like blown output channels clipped signal etc…

Getting a good ground means that you have to use the shortest cable as possible from the ground point to the electrical thing that is being grounded. Having a longer connection will cause or increase high resistance making it not to transfer the electricity good causing problems with your equipment.

Always try to find the best ground as you can and use the bigger and shortest( in length) connections you can.

Part 14

Car charging. Whats first???

First is to calculate your total power that yoru sound system will draw from your car charging system. If your alternator is big enough you might go away with it. But sometimes people use tons of power and the stock alt just cant keep up with the demand.

Like I said try to get a good alternator that have good output at idle and that is able to give the power you need..

Big 3 whats that???

Is a method to improve or upgrade the car charging wiring system for better current flow…

It consist of adding 4-0 gauge wire from your alternator to your battery +.

Then adding 4-0 gauge fron battery negative to chassis.

The next thing to add 4-0 gauge wire from engine block to chassis or battery negative ( for me is best to use the alternator casing as ground to negative battery )

Make sure you disconnect your battery and protect all your electrical before doing this work. Also when connecting to chassis make sure you scrape any metal and find a good spot for grounding.

Part 15

Is a capacitor needed??

Mainly yes, a capacitor is needed in car audio and even if you don’t have a high powered car audio system is needed. They are used to power the 15kw Rockford fosgate amp 

Why???

Because the capacitor will work as a buffer and a filter for your charging system AND because of the alternator makes AC current then transfers it to DC current and when the car is demanding lots of power making the alt work really hard sometimes the alt will miss tiny AC-DC conversion. The capacitor will somewhat help to filter out unwanted AC that was not converted into dc current and somewhat improving your voltage and your amperage and the quality of your electrical system.

But no the capacitor will suck power from your charging system in a car audio and make in it worst??

The answer will be yes BUT no. the capacitor is a fast charge/discharge device. Which when is charged and your amp produce the up to 5 second boom sound the amp will try to get all the power it needs and the stock charging cant provide all that power the cap will try to help it out alil by sending all its power but when the boom is stopped as fast as a 1 second when the amp is not asking for power the capacitor will charge in that 1-5 second time. So clearly is not sucking power IS helping the charging system. However the capacitor is kind of like useless if your over exceeding what your charging system can provide. If your charging system is set up to your electrical equipment a capacitor is a MUST and a PLUS, like I said the cap will filter unwanted AC current and will help to avoid sending that small AC current to your amp or your equipment and somewhat shorten its life and will provide a richer and cleaner electrical signal.

So if I get the cap is the rule of thump okay??

Umm not really. Some people say .5 farads for every 500 watts or 1 farad for every 1000 watts.. and from the results we gotten. You have at least double the quantity for your electrical since not only your amp will use it. Try at least 2 farads for every 1000 watts of power.

And finally make SURE you don’t exceed 20 inches of wire when your wiring it to your amp. Make sure is close AS possible to the device you want it. And not to exceed 20 inches

Roberto Rosales

let me know if it indeed help alil