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Old 10-18-2002, 08:20 PM   #1
AmIGrand
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Basic System Design and Tuning

I've had lots of questions recently about what to get in what order, how to set gains & crossovers etc, and basic troubleshooting. All these things come under the heading of "basic system design, layout, and tuning" in my mind, so here we go. There will inevitably be differences of opinion here. Feel free to bring these up, this is a good place to discuss them - but as always, this is a thread to teach those newer to the 12-volt world some basics, so keep everything factual and calm, please!

An audio system is going to consist of a few necessary parts. A source (CD player, etc), an amplifier (this is anything that sends power to the speakers, whether it be deck power or an outboard amp), signal procesing (pasive or active, explained later) and speakers. The stock system in most cars is a so-so source, with either bad or so-so amplification and signal processing, and speakers ranging from bad to decent. This industry exists for those who like their music enough to invest time and money into improving on this setup, if not outright replacing it! So, begining with what does what and how to get the most out of it -

Source - The deck supplies the signal for the rest of the system. Period. If you like flashy lights and graphics and other stuff, that's your call, but do not sacrifice quality to get these things or the rest of your system will suffer!

Amplifier(s) - Their job is to take a small amount of power and make it more powerful. Again, you can get models that do all kinds of crazy things and look cool, but a basic amp that does it's job is better than one that has flashy L.E.D.'s and plexi for the same money.

Crossover(s) (also called x-overs) - Divide's the audio spectrum to send the right frequencies to the right speakers. Without them, things sound bad real fast, and speakers die horrible deaths.

Speakers - From subs to tweeters, having the correct driver for the correct part of the sound spectrum is essential. There are lots of opinions out there, follow your ears when selecting a speaker, no one can tell you what you like!

Speakers are the single most important part of the equation, they are what you listen to! However - the best speakers in the world sound like crap if they don't have a good signal, in fact, a bad speaker will mask distortion, a good one is true to it's signal - so all the crap will shine through! Because of this, a firm foundation must be planted, and that means clean power. I say that the first step in any system is a decent amp, unless you don't have a CD player. Deck comes first if you need to change the source type or your existing one doesn't work. Assuming that the stock setup has a CD player and the speakers aren't blown, the first step is an amp and a sub.

The reason for this is simple: The stock speakers are OK, they're just playing full range with not enough power. Distortion will kill a speaker before power will every time. When you have a speaker playing full range, the lower frequncies (below about 100 Hz) take about 2/3's of the available power, leaving precious little available for the bulk of the music. In order to play these low frequencies well, a speaker needs a LOT of power and needs to move a LOT of air, which means a LOT of motion. Asking a small speaker to do the job of a big one is going to limit the sound you get, and if pushed, will result in blown speakers. By cutting the low frequncies from the small speakers and dedicating a speaker that is made to handle them to that task, your stock speakers will be loud and clean, and you'll find an octave or two of your music that you didn't know you were missing!

There are two ways to do this in the begining - run the highs off the deck and get an amp for the bass, or get a multi channel amp or seperate amps to power the whole system. It will depend on your budget more than anything else. The cheapest way to do things is to turn the bass down ALL THE WAY DOWN on your deck - this reduces the power consumed and the distortion produced by your poor little speakers - and get an amp to the sub with a bass boost set to about +12 Db to compensae for the reduced signal. Alternatively, you can get an amp with built-in x-overs to cut the bass out of the highs, and leave the tone controls alone. This is better, but more expensive. A third solution is some new decks with HP x-overs for their onboard power, a good in-between if you went with a new deck in the begining, but not for this scenario.

Next on the list will be speakers. Now that we have a good power base and a sub, we want to get speakers that play like we want. Follow your ears. A coaxial speaker has the tweeter mounted in or on the mid. This type of speaker is more efficient, easier to install, and cheaper. A component set (seperates) will have a seperate mid and tweet. This allows for more versatility in speaker placement, and the use of an outboard crossover usually means higher power handling. More work, and more money, but more sound.

So now we have a clean power base, and good speakers, with some bass. For many, this is enough! But now we can start into the details. Personaly, I consider a new deck to be a detail, except as outlined above. By getting the new deck, we send cleaner power to the amp, so we get cleaner sound out of the amp. Beyond that, it's a matter of getting the features we want for more enjoyment of the system - a seperate volume control for the woofer, MP3 playback, a multi-disc changer, and those funky graphics that every manufacturer but Eclipse seems to thing are so darn special.

Now we have a complete system, EQ's and stuff can be added as we delve deeper. Right now, all this stuff needs to get set up correctly.

This is a basic overview of who what when where and why. How is discussed in some of my other stickies on impedance, voltage, and box design, as well as others still to come. We will assume here that you have the right wires, the right box, and the correct impedance speakers and subs for your system, and get into getting it all tuned correctly.

Active crossovers. Most amps have these built in, so do some decks. I do not usually recomend using deck x-overs, they aren't all that accurate. But they're beter than nothing. Try not to stack them unless you really know what you're doing - if both deck and amp have built in x-overs, use the one with the better range of adjustment, not both. On the amp, there are three types, switched, selectable, and adjustable/variable. Switched will be ON/off at a set frequency. Not the best, we may want another frequency - but better than nothing. Selectable will be a switch with several set frequency options, this is better. Adjustable or variable will have a continuously adjustable range with which to set the frequency, usually 50 to 500 or so. This is pretty simple - you want the frequency to match the size speakers you have. Smaller speakers need to be crossed higher (less bass) larger ones can be lower (stronger midbass). Subs are all about the same - contrary to popular belief, big woofers don't NEED to be crossed lower. Crossover slopes and subsonic filters will be attacked later, in a more in-depth thread. Small speakers (3.5 to 5.25 inches or so) should be HP in the 100 to 150 range, higher with more power. Medium speakers (6 and 6.5's, 5x7, 6x8, 6x9, etc) will be in the 80 o 120 range. Subs usualy work best LP between 70 and 100. Play with it once your gains are set to get what you're after.

Amplifier gains. These are RARELY set correctly, even by pro's. In a perfect world, they would not be necessary! All decks would have a standard preamp signal voltage, and amps would be set accordingly at the factory. Such is not the case, however. Gain is not there to make things louder. Gain is there to match the amps input section with the sources output voltage. Some decks have vary low preamp voltage, .5 to 1.2 volts or so. Some have very high output voltage, 4, 5, 8 - even 16 volts in some cases. The gain control on the amp will have a given range, usually .5 to 5 volts nowadays. You set the gain on the amp as close as possible to the max output on the deck, plus a little - the deck seldom puts out maximum preamp voltage, and some CD's are recorded louder than others. The easiest way to do this is by ear, believe it or not. Put on some very powerfull, full-range music. Heavy modern rock bands and loud classical music are best, rap and techno have very little signal across the full range, and don't get a lot of output. If you can get your hands on a test CD with an all-bits-high pink noise signal, great! Turn the gain ALL THE WAY DOWN, and the deck volume ALL THE WAY UP, in that order. Begin turning up the gain SLOWLY, until you begin to hear distortion, and stop. Done! Hopefully, this is louder than you will listen to your music 90% of the time. If not, DO NOT INCREASE THE GAIN! You need more power - get a bigger amp!

We now have a clean little system, that has some bass, plays loud & clean, and doesn't run the risk of blowing up any time soon. Unfortunately, this means you are now addicted, and will be expanding the system in the near future.

I hope this gives people new to the stereo world an idea of where to start, and how to avoid blowing up the stuff they start with. There is a lot more to cover here, and it will be covered. I hope we get a lot of discussion going on this one, as it will enhance the effectiveness of this thread - so please comment and question away!
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Old 11-14-2002, 12:53 PM   #2
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Hey bro I have a couple questions for ya. I'll be tuning my new system soon once I finish building my trunk and glassing, and I had some questions about gain. I've tuned a one amplifier system before, but for my new one I decided to do the following setup...

2 Kicker Comp 15" (250rms)
2 Rockford 250a2 Amplifiers (250rms x 1 @ mono)
Pioneer DEH-P9200H Deck (4V preamp outputs)

I'm going to obviously bridge each amplifier onto one subwoofer. Now when I tune this sucker, It's going to be rather difficult to get the gain on both amps exactly the same. Secondly, since I'm bridging into mono, do i need both RCAs plugged into both amps? Or will it only actually take the left channel's signal, meaning I could put the left channel RCA plug into the left channel of the first amp, and the right channel RCA plug into the left channel of the second amplifier, rather than splitting my RCA preamp and cutting the voltage inhalf. Any suggestions to make this easier on me? Thanks a lot my man.

Also, as far as capacitors go, I know they're a bandaide, and I'm going to have to see how much my lights dim before I make a decision. In your opinion though, how much can our alternators handle wattage wise (peak and RMS) before needing a new alternator? Also would the system just hurt it a little so a 1 farad capacitor might be a good option? My system is going to be pulling about 700 watts RMS and 1100 peak when it's all said an done.
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Old 11-14-2002, 11:36 PM   #3
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Wattage ratings on amplifiers will have nothing to do with your alternator, 'cuz every brand rates their amps different;y. You go by the current draw, which is indicated by the fuse. The 250a2 has a 25 amp fuse if I remember correctly, so 50 amps for both. If you have another amp running the highs, the 3 amps will dim the lights noticably at high volumes. With just the two, you should be OK with a cap, without it the lights will dim, but not badly. It also depends on what else is running - if you have the headlights, wipers, and heater going, it'll dim the lights more than if it's just your DRL's and nothing else. Anyway - you should be OK without the cap, and fine with it.

As for the gains - You really ought to get one amp to run both subs unless you have an oscilliscope to match the amps precisely. If you must use 2 amps, and you don't have an O-scope....

Punch amps bridge from the left channel, so that's OK with the RCA's the way you said. Just make sure the switch on the amp is set appropriately. The optimum solution IMHO would be to get a line booster like the Phoenix Gold Bass Cube (I love that thing) or the AudioControl Overdrive. That way you can leave the gains basicly all the way down, and just cram a ton of input voltage into the amp. Other wise, tune one amp and one woofer with just the left RCA in it until it's correct with the gains, and set the other amp to the same level.

Either way, make sure the box is seperate chambers - you do NOT want to try and tune a system with multiple amps driving speakers in a common chamber, trust me. Been there, spent hours doing that. Not fun.
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Old 01-03-2003, 10:06 PM   #4
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Re: Basic System Design and Tuning

Quote:
Originally posted by AmIGrand
Small speakers (3.5 to 5.25 inches or so) should be HP in the 100 to 150 range, higher with more power. Medium speakers (6 and 6.5's, 5x7, 6x8, 6x9, etc) will be in the 80 o 120 range. Subs usualy work best LP between 70 and 100.
Okay, i'm tryin to get this...so since i have 5.25 in the front, i should set my crossover at about 100, 6x9 at about 80, and a sub at 80? It's a high pass for the 5.25 and 6x9, but a low pass for the sub, right? I have it set right now with a low pass for the sub, and just the bass down on head unit with a bass boost for the sub.
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Old 01-03-2003, 10:22 PM   #5
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You'll wanna play with it a bit to get it right on, but that's a good start!
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Old 07-04-2003, 04:59 PM   #6
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AmIGrand, you said:
"By cutting the low frequncies from the small speakers and dedicating a speaker that is made to handle them to that task, your stock speakers will be loud and clean, and you'll find an octave or two of your music that you didn't know you were missing! "


this means that with a 2-channel amp and a pair of subwoofers, will do the job?

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Old 07-04-2003, 05:33 PM   #7
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yeah, what you'll do is set a bit of a bass boost on your amp for the subs, and at the head unit, you can turn the bass down so that bass will be cut from all your speakers, but since u ran a bass boost on your subs, it'll make up for the loss. So, you'll have your subs running how they should and your stock speakers running only the higher notes they're designed to play.
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Old 07-05-2003, 09:37 AM   #8
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Bingo!

The stock systems in most GA's have more potential than one might think once you relieve the poor stock speakers of the unecessary stress. Adding an amp and sub will bring it to life!
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Old 09-19-2003, 07:03 PM   #9
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I would like to make a note on how to set up two amps for the same output. All you need is a multimeter and a little time. Just put your meter on AC and put the ends on the amp output of the amp while its hooked to the speaker. Now just play a sine wave and measure each amp and turn the gains untill the output is the same. Thats the easy way to do it anyway. You can also see what your amp is acually putting out by squaring the AC and dividing it by the ohm load. Peace, Lee
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Old 09-20-2003, 10:28 AM   #10
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Good info! Thanx for the input!
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Old 12-09-2003, 08:13 AM   #11
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tweeter

anyone know what size the tweeter on the doors of a 99+ GT coupe is, I was thinking about replacing them.
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Old 12-10-2003, 08:08 PM   #12
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It's a 1/2 inch piece, but a careful hand with a dremel and a good eye for install could put any shallow mount piece in there, up to about 1".
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Old 12-10-2003, 08:30 PM   #13
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You may have covered it already and I may have missed it, or maybe you intend to cover this. I find alot of systems out there way outta balance! Remember to balance your amps. This will give you the best control thru you H/D..
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Old 10-03-2005, 09:45 PM   #14
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hey all...i am new at this and i jsut installed a urban 700 watt 2 channel amp and two audiobuhn subs rated at 300 watts..... i didn't want to tare out the radio to see if the stock radio had rca hook ups.. so i bought something that i jsut plug in my speaker wires in to and i get rca's for my amp..... well... i got it all hooked up and it seems to only work half the time... like if i have it on so the amp puts out bass only... you hear it for a while then it goes away like the amps shuts down but if the amp is on full meaning it is puting out highs and lows it work fine.. beside i have blowed the sub....what would cause that.. wehat it be the thing that bring the stock speaker wires to rca or the amp???? and does the stock head unit have rca outputs?
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Old 10-05-2005, 04:07 PM   #15
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Quote:
Originally Posted by devil_bowler
hey all...i am new at this and i jsut installed a urban 700 watt 2 channel amp and two audiobuhn subs rated at 300 watts..... i didn't want to tare out the radio to see if the stock radio had rca hook ups.. so i bought something that i jsut plug in my speaker wires in to and i get rca's for my amp..... well... i got it all hooked up and it seems to only work half the time... like if i have it on so the amp puts out bass only... you hear it for a while then it goes away like the amps shuts down but if the amp is on full meaning it is puting out highs and lows it work fine.. beside i have blowed the sub....what would cause that.. wehat it be the thing that bring the stock speaker wires to rca or the amp???? and does the stock head unit have rca outputs?

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Old 10-09-2005, 02:50 PM   #16
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ok so i lost devil bolwer about half way through but i do have a similar question. I'm also clueless as to most of the stuff but i have help from people who arent. My main concern is where are the rca jacks are. I took out the head unit and was rather disappointed. I am absoultely stupid when it comes to the audio stuff but if someone could tell me where the rca jacks are, that would help a great deal
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Old 11-02-2005, 03:21 PM   #17
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There are none on stock systems. They build as cheaply as possible, and are not worried about expandability.
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Old 07-19-2007, 08:03 PM   #18
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I was about to post up an amp gain tutorial, but it looks like you've got it covered quite nicely.

I'd like to add a great site I found for test tones, which IMO work way better than trying to use music to set the gains.

http://www.realmofexcursion.com/downloads.htm

It's real easy to detect clipping with a test tone. 1khz usually works well for your regular speakers. For subs you'll need to use something low, but if you can use something sorta high (200hz with LPF off) it'll be easier to hear when it starts clipping.

Also, playing a full-on test tone can damage your speakers (and your hearing). Temporarily wiring your speakers in series off of one amp channel while setting gains is a good idea. This will theoretically cut the power going to your speakers by 75% and you won't have to worry about blowing them up.
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