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| By: P0werLifter on Sat, 4 Oct 04:14:11 -0500
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To start off, Id like to go ahead and cover the basics of the electricals needed to run a stereo system, whether it be a SPL, or SQL based system. Every automobile charging system has an alternator, and a battery with Power and Ground leads. The average automobile has around a 100amp Alternator with a battery. It takes around 50-60amps to run your stock electricals. So with a stock 100amp alternator that leaves you with 40-50amps to play with without having to upgrade you electricals.
When figuring out how much power is going to be needed to run a given stereo system, add up the total wattage of your system multiply that by the efficiency factor,divided by your charging systems voltage (13 volts is a good average number to use). As you will notice, different classes of amplifiers have different efficiency ratings.
Well go ahead and say you have purchased a 1000watt amplifier. Class D/T amps run about about ~90% efficient, so figure about 1111/13=85.5A
Now as far as Class A/B and HC amps, the efficiency is much lower, around 55-60%To get 1000watts RMS out of an A/B amplifier, it will take around ~1800 watts of input to produce 1000 watts of output (factoring the efficiency). 1850/13= 140amp draw. Notice the current draw is much higher in the A/B and HC classes from factoring in the efficiency. Class D/T amplifiers are recommended if your powering subwoofers.
If you are only over your alternators charging capacity within about 10-20amps...you might get by with just buying a High Cold Cranking Amp ( 850CCA or higher ) like a Optima Yellow, Red, or Blue Top and maybe a 1 or 2 Farad Capacitor. This may..or may not help. But would be a good start without having to fork out the money to upgrade the whole charging system.
***Remember in order to even consider running a very large wattage system, upgrading your charging system is a must. There are no other effective substitutes. For High SPL applications, that require TONS of amperage, many competitors run multiple alternators, and a bank of batteries to support the power requirements. In order to run multiple alternators you need to make sure that your alternator brackets and the actual alternator itself is perfectly aligned with the belts to make sure you don't shred your belt and leave you stuck somewhere. Also if your going to run multiple batteries, you need to run these in parallel to still net 12Volts for your system to run on. In addition many people run dual alternators, 1 for your stock electricals, then another with the batteries to run your system, Tv Screens etc.
If your love your system Low , and Loud enough to where your eyes shake, and your body tingles, then this is the area for you. SPL (sound pressure level) is basically how loud you can get in dB's at in a certain frequency range.
There are many different types of subwoofers, some for Sound Quality, some for SPL, and some that are a mix (SQL). For the remainder of this article I will only be focusing on SPL woofers, amperage, and box building techniques.
When looking for an SPL subwoofer, look for high XmaX (high one way excursion ---How far the subwoofer and move in and out) and high power handling Capability ( not the MAX handling..look at the RMS value for the subwoofer). A subwoofer with high power capability, and high XmaX will net good SPL results when combined with a proper box design, matched to the subwoofers used. By far the greatest factor in SPL is your enclosure. This is where it alot of experimentation comes into play as far as Port Area, Size of the enclosure, Positioning of the subwoofers, etc.
As a general rule the larger box and port area the better. Its going to take some experimentation but build an enclosure, put in a bass CD and do a couple low frequency sweeps to figure out what frequency puts out the highest SPL output in your vehicle. then tune your next enclosure to that frequency.
Remember, Port area and tuning are KEY to SPL output. As far as subwoofer placement, usually you get better SPL results from either pointing the subwoofers up, or towards the back to avoid noise cancelation (again this is going to take some experimentation). As far as wattage goes, competitors push their subwoofers to the max and sometimes above it to produce maximum excursion ability to produce larger numbers.
For example, say you have a subwoofer thats rated at 1800RMS. If you run it at 900rms you canstill reach the XmaX of a given subwoofer, but if you double the power up the the orginigal 1800watts, you will gain +3dBs...(even though this is not audible to the ear above ~120dB of SPL), every dB counts in competition. Also sound deadening you vehicle well net about a 3dB gain.
Remember, Enclosure size, design, Tuning, and Port area are KEY to SPL output, there is no set rule that is appropriate for every automobile so its going to take experimentation to get everything perfect. HAVE FUN and I hope this guide has helped you,
If you have any suggestions, Comments, Questions, Feel free to get a hold of me.
P0werLifter
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