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I figured i may as well write a better explanation of the whole stereo building thing, for anyone who ever wants to search on the BB for it.
maybe i should post this in the general section? oh well, anyways...
The first step to a stereo system is finding an amplifier that is "matched" to your speakers. Or finding speakers that are matched for your amplifier, depending on which one you own first! :) Honestly, almost everything in car audio is in the same range, around 50watts max, however, there are exceptions when you get into higher end equipment. Home audio is usually more diverse, and the ohms are usually higher as well... the concept is the same though...
"Matching it" means that the rated power output of the amp is at least equal to or GREATER than the rated power REQUIREMENTS of the speakers. You can overpower most quality speakers by 25% or even up to 50% if they are well designed... and not damage them over the long term. Under-powering a speaker will damage it MUCH sooner than overpowering it will. This is because there isn't enough electric-magnetic force on the speaker coil to keep it centered in the magnet as the cone moves... which will pop the speaker coil out of the magnet... blowing the speaker. If you feed the speaker enough power, no matter how loud you crank them, the electromagnetic force should keep the cone where it should be, centered in the magnet as the cone moves.
However, speakers that are more powerful in terms of sheer wattage ratings aren't always louder though! speakers have something called the "sensitivity rating". This rating is in dB, or decibels, and it shows how the speaker will REACT to the wattage power you are sending it. A speaker with a sensitivity of 110dB will be MUCH more efficient with the power you send it, and louder, than a speaker with a sensitivity of 90dB. Something to keep in mind when shopping, so check and compare the sensitivity ratings of your speakers! Although, most consumer speakers are within the 90-100 range, which is fine, but the higher the better, and you get what you pay for...
So, back to amplifiers. if your amp says 3000 watts on it, like the one on the left in the picture in my post above this one... it's rated for 3000 watts PEAK output.
Manufacturers like to usually list the highest output an amplifier can ever do, for the sheer sensationalist effects of having the highest number possible on the rating.
This high number is usually the amplifiers PEAK output, and the amp rarely reaches it under normal circumstances.
My amp for example, is rated at 3000 watts, but only at ONE OHM. this means that whatever speakers it is connected to, their ohm load, sometimes referred to as IMPEDANCE, has to be one ohm as well in order for the amp to output it's full power. I'll get to ohms in just one second...
so the real ratings of my amp are
3000 watts at 1 ohm
2400 watts at 2 ohms
1200 watts at 4 ohms
Ah, the plot thickens! The amp isn't really putting out 3000 watts all the time, so, dont jump the gun and buy a 3000 watt speaker, unless it's ONE OHM! Which is rare...btw...
To further thicken the plot, these ratings are the PEAK power output ratings of the intended ohm-load situations.
Meaning that, even at 4 ohms, the amplifier STILL isn't putting out 1200 watts all the time!
Amps have peak power output ratings, and CONTINUOUS power output ratings, or "R.M.S." ratings.
The R.M.S. is the consistent wattage power the amplifier will be putting out, and THIS number is the one you need to match with your speakers. The same actually can be said of speakers too. They give the PEAK power rating, and the RMS power rating. You want to paya small bit of attention to the peaks, in order to keep them in the same ballpark, HOWEVER YOU WANT TO MATCH THE RMS POWER RATINGS AS BEST YOU CAN!!!
RMS stands for something of course, but what it stands for escapes me. as i recall it was a very complicated abbreviation for a *VERY* complicated mathematical equation on how to calculate the continuous power output in watts, and all we need to know is RMS stands for continuous! :)
In fact, my amp didn't even suggest what the RMS power was, but i know it's less than 1200... SHEESH...
so we went from 3000 to under 1200 in a short ammount of research. Sounds like a scam right? That's just the industry trying to sell you something...
Quick sidenote, this amp CAN put out 3000watts rms... and it was under $400. So, why didn't everyone buy one? There is yet ANOTHER rating to consider when shopping. And that is the THD rating, which is in PERCENTAGE.
THD stands for TOTAL HARMONIC DISTORTION, which is the level that the internal electronics of the amplifier will distort the audio signal passing through it. You want this number to be AS LOW AS POSSIBLE!!!
You do not want the amp to add ANY noise to the audio signal as it passes through its' circuitry. You want it to be as clean as possible, and this is the THD rating. A THD rating between 0.01% and 0.05% are some of the best ratings you can achieve... those are the actual numbers to look for, HUNDREDTHS of a perent.
My amp? well, they didn't even LIST the THD, however i heard it was 5%!!!
This means, that the sound is VERY harsh, and distorted, all the time, well, compared to an amp with a THD that is lower. again, you get what you pay for...
OH Well, Back to ohms.
So. my amp is a MONO-subwoofer amp. It's only meant to power subwoofers, like that 18" woofer you see in that picture in the above post. It only has one MONO channel, because a stereo subwoofer is pointless, due to the characteristics of bass frequencies. BASS frequencies are almost impossible for the human ear to locate where they are coming from, so panning them left or right wouldn't effect how they sound to us. Almost ALL bass recording you hear are panned, or split, evenly between the left and right tracks of your music cd's or mp3's. Ever wonder why the 5.1, and 7.1 systems only have one subwoofer? they only NEED one! the .1 stands for ONE SUB! And all the bass in 5.1 recordings is sent to that sub. Your ear couples it with the sound from the other 5 speakers, and in your mind the image is put together. pretty interesting stuff...
Gods honest truth, the subwoofer i had was 1600 watt RMS at 4 ohms, and my amplifier wasn't technically powerful enough to drive it efficiently.
I didn't have the money to spend on an amp at the time to run it at over 1600watts at 4 ohms... it's difficult to find one...
What I should have done, obviously, Is dropped the ohm rating to 2 ohms somehow to get more power out of my amplifier...
however, this is only done by adding more speakers to the setup.
there are two ways to add a speaker to an amplifier, and adjust the ohm rating that the amplifier "sees".
One is to daisy chain the speakers together. Positive terminal to positive terminal, and negative terminal to negative terminal...
just like car batteries when you are jumping a car. (i know you're supposed to ground to chassis, but for sake of argument)
so, you come out of the amp and into the first speaker, then out of that speaker to the next speaker. Really simple.
Adding speakers in this manner is called running them in PARALLEL, and running them this way effectively HALVES the ohm rating the amp sees, assuming you used two of the same EXACT speaker, which is a must!
So, you ran two 4 ohm speakers in parallel, and you get a 2 ohm load.
However, you add the speakers wattage together! So, in my case, assuming i could even fit another 18 in my trunk, you'd have 3200 watts at 2 ohms. Well, this is STILL incorrect for my amplifier! Back the thr drawing board...
The other way to wire speakers together, although less common, is series wiring.
You run the positive out from the amp, into a speakers positive, however, you run out of that speakers NEGATIVE terminal, and into the next speakers POSITIVE terminal, then out of that speakers negative, and back to the negative of the amp. You make a big LOOP of a single strand of wire between all the speakers.
Series wiring DOUBLES the ohm rating the amp sees, because now the power has to flow through all the resistance of the speakers voice coils. By the way, if one of these speakers voice coils should fail, then BOTH of the speakers will stop making sound. This is a disadvantage of series wiring.
There is a combination of series and parallel wiring to achieve different ohm ratings, and to prevent loss of sound in the event a driver should fail, but those are much more complicated to setup, and generally aren't used in everyday situations.
So...
Summing up so far
Match Wattages in RMS between amps and speakers
Match OHM ratings between amps and speakers, depending on what the AMP needs!
Wire speakers in single, parallel, or series to achieve the desired OHM rating for the amp.
Buy speakers with the HIGHEST sensitivity you can afford.
Buy amplifiers with the LOWEST THD you can afford.
And, i think that's it.
If anyone ever has any questions, feel free to write me... i can't type any more today! ;)
-gavin
posted by 74.70.10...
, Mon, 5 Feb 2007 09:31:37, Mon, 5 Feb 2007 14:58:04
, Mon, 5 Feb 2007 21:39:44, Tue, 6 Feb 2007 10:57:22
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