Car Audio Help (Amp/Subwoofer Setup)

[Afro000Dude]

I was kinda curious as this is a topic I know little about. Can anyone explain to me how to set up, for example, one amp driving two subwoofers? If the subs are 800 watts peak, would a 1600+ watt amp be needed, or would a less powerful one work? And how does "bridiging" two or more amps work? Hmm, I guess this is what happens when I get bored and curious...

 

[Shockwave]

An amp doesnt see speakers. It sees 1 load (The sum of the speakers) on the output section. Thus, you could run 1 sub or 100 subs off of 1 amp. The amp wont know the difference other then what load is presented to the amp.
The total power output by the amp is split between all speakers on the output. Thus, if a 1000 watt amp has 1 speaker, that speaker sees 1000 watts. 2 subs get 500 watts apeice. 3 is 333 watts etc etc. Divide total power by number of speakers for power per speaker. Simple.
Briding amps is NOT recommended unless the amps are strappable from the factory. Bridging two or more simply means combining the total output of multiple amps onto 1 load. Good stuff for high power applications, but again, if the amps arent designed specifically to be strapped (Which some are) then I highly caustion against doing this unless you really know what your doing.
As to your specific application, if the subs are 800 peak watts you dont want 1600 RMS watts, you'll cook the subs. Look for the RMS rating of the subs, or play it safe and get an amp around 800 watts total, which would run 400 to each sub.

This link will give you a good idea how 1 amp output runs multiple subs.

 

[MikeMike]

youve got a long way to go

800 watt peak, is the PEAK amt of power the manuf reccomends. assuming they follow industry standard, that means the sub is RMS @ 400 watts. (shockwave beat me to this point)

you dont bridge 2 or more amps, you bridge 2 channels which normally allows the amp to put more power all into one heap, but makes the amp only able to handle a lesser ohm load. like for instance, if you had a 2 channel amp, that allowed for a 400 watts by 2 @ 2 ohms, if you bridge the channels, you would be able to have a 400 watts x 1 @ 4 ohms. then you have mono block amps, which are stackable with an amp identicle to it, which will act like a bridged amp.

then you have to take into account what types of loads you can get from the subs, how many voice coils they have, and what ohm rating each vc is, if you have a single voice coil @ 4 ohms, you can give a 4 ohm load only. A dual voice coil, with both voice coils being 4 ohms, will allow you to give the amp a 2 ohm load, or an 8 ohm load, by wiring either parrallel, or in a series.

then it just gets more complicated.

MIKE

 

[Afro000Dude]

Yeah I was just about to edit it to 800 peak. I've just never understood how it all works. Thanks for the info.

 

[Beau]

Originally posted by: Shockwave
An amp doesnt see speakers. It sees 1 load (The sum of the speakers) on the output section. Thus, you could run 1 sub or 100 subs off of 1 amp. The amp wont know the difference other then what load is presented to the amp.
The total power output by the amp is split between all speakers on the output. Thus, if a 1000 watt amp has 1 speaker, that speaker sees 1000 watts. 2 subs get 500 watts apeice. 3 is 333 watts etc etc. Divide total power by number of speakers for power per speaker. Simple.

Little more complex than that

You have to figure the impedence of the speakers into the situation. 1600 watts may be for a 4ohm load, it will change inversely proportional with that load. Example:

1600 watts @ 4 ohms = 800 watts @ 8 ohms = 3200 watts @ 2 ohms ( you have to have a 2ohm stable amp to do this)

You can control what your circuit impedence is by the way your wire your speakers. If you wire them in series, your impedence goes up, if you do it in parallel, it goes down. To figure what it is, you take the impedence of the speaker ( usually 4 ohm, unless its a dual voice coil, which can be either 2 or 8), and either times it by the number of speaker you have running in series, or divide it by the number of speakers you have in parallel.

http://editweb.iglou.com/eminence/eminence/pages/support/wiring/wiringfour.htm

 

[MikeMike]

like in my sig, i have 4 single voice coil 12's @ 4 ohms per voice coil.

with this setup i can obtain a load on the amp of, 16 ohms (that will give you no power), or 1 ohm. yes, i could get others, but then each sub would not be gettint the same power.

i have my amp putting out 1100 watts @ 1 ohm. to do this @ 1 ohm the amp must be built for it, otherwise you could damage the amp due to heat.

how much more complicated do you want to get?

MIKE

 

[Shockwave]

Thank you Beau, but I figured we'd get to that part of the lesson after he had a basic understanding of amps. I personally am WELL aware of how to wire amps. I also know what happens when you run to low of impedence to them, or low enough to generate too much power to the sub.
Oh, and to prove you wrong on 1600 @ 4, 3200 @ 2 etc... Regulated power supplies

 

[Beau]

Originally posted by: Shockwave
Thank you Beau, but I figured we'd get to that part of the lesson after he had a basic understanding of amps. I personally am WELL aware of how to wire amps. I also know what happens when you run to low of impedence to them, or low enough to generate too much power to the sub.
Oh, and to prove you wrong on 1600 @ 4, 3200 @ 2 etc... Regulated power supplies

I was being theoretical

(okay... I've been pwned.)

 

[MikeMike]

how about we talk about subwoofer enclosures too.

you have your IB, sealed, ported, bandpass, and nth degree bandpass.

i know IB, sealed, and ported.

IB is easy, infinite baffle, big as you can get it.

sealed, is built to a certain size which is dependant upon the subs vas rating.

ported is built to a certain size, then a port, of x length and of x sq in of port space is built and used to vent the air. to get the length, you must figure out what hz you would like to tune to, around 30 is desireable for daily driver setup. and that will give you your length. the sq in of port space is dependant upon the size of the enclosure.

yes, i can get more indepth but im gettin tired of typing.

and be careful, an amp may advertise its MAX power (you will never get it) like sony, and the other brands normally do at BB, they state their max power, @ 14.2 volts.

MIKE

 

[Shockwave]

Originally posted by: Beau

Originally posted by: Shockwave
Thank you Beau, but I figured we'd get to that part of the lesson after he had a basic understanding of amps. I personally am WELL aware of how to wire amps. I also know what happens when you run to low of impedence to them, or low enough to generate too much power to the sub.
Oh, and to prove you wrong on 1600 @ 4, 3200 @ 2 etc... Regulated power supplies

I was being theoretical

(okay... I've been pwned.)

So, you were theoretically owned then?

(BTW, Thats the dumbest smiley EVAR!)

 

[Beau]

Originally posted by: Shockwave

Originally posted by: Beau

Originally posted by: Shockwave
Thank you Beau, but I figured we'd get to that part of the lesson after he had a basic understanding of amps. I personally am WELL aware of how to wire amps. I also know what happens when you run to low of impedence to them, or low enough to generate too much power to the sub.
Oh, and to prove you wrong on 1600 @ 4, 3200 @ 2 etc... Regulated power supplies

I was being theoretical

(okay... I've been pwned.)

So, you were theoretically owned then?

(BTW, Thats the dumbest smiley EVAR!)

Hypothetically speaking, yes.