newb amp question

[hmchaos]

i have two 8in subs that i was thinking about putting somewhere in my new 93 sedan. my only problem now is how much power i need to push them. ive heard mixed thoughts.
is a 2 channel or d class better?
do i need more power than the subs can handle(maybe like 50-100w more)?
all im really sure about car audio is that you go by the rms? right?

heres the sub specs:
1300W Peak Power Handling (Total) / 650W Peak Power Handling (Each)
650W RMS Power Handling (Total) / 325W RMS Power Handling (Each)
2” Parabolic RFL Voice Coil
60 oz. Magnet
4 Ohm Impedance

[sonikaccord]

I'm guessing 650w is as a pair. You should get a monoblock, class d is more efficient but not necessarily a requirement. All a monoblock is another name for a one channel amp. More power is always good, but 100w extra won't make too much of difference if you got a 700w amp. I'm again making the assumption that each sub is 4 Ohms. You should look for an amp that puts out it's most rms watts at 2 Ohms. (2 subs wired in parallel equals half the ohms) I'm being very simplistic cause I don't want to confuse you. It's alot to take in sometimes

[jewelproject]

8inch? thats a little small for my taste(thats what she said). i would go with a nice mono amp. then go crazy and turn your rear deck speakers into mounts for your 8's. relocate your rear speakers into your doors!!!! but its your car do what you want with it. if your not sure what you want. find a friend who has a decent amp and hook it up to your subs.

[hmchaos]

to sonik- yes its 650/pair. im trying my best to soak it in... and i appreciate your info.

to jewel- yeah, two 8's...(now that i wear big boy pants and im all growed up , im not big on hearing loss, parts rattling off my car or having a sound system thats worth more than the car itself)... i just wanted to have a nice sound. also, i was planning on doing the rear deck when i get home (get to leave bahrain on 1Sep! score!). i just didnt know if i had the room or not. have you seen it done? great ideas!

[Hopeless]

8inch? thats a little small for my taste(thats what she said). i would go with a nice mono amp. then go crazy and turn your rear deck speakers into mounts for your 8's. relocate your rear speakers into your doors!!!! but its your car do what you want with it. if your not sure what you want. find a friend who has a decent amp and hook it up to your subs.

hehehehehe, 8's can still pack a punch. buddy with 2 DD1508s running on an Alpine PDX 1.1000 that i have in my closet now was pushing 142dB+

sonik's info is on point, i generally like class D monoblocks over all

[hmchaos]

hehehehehe, 8's can still pack a punch. buddy with 2 DD1508s running on an Alpine PDX 1.1000 that i have in my closet now was pushing 142dB+

sonik's info is on point, i generally like class D monoblocks over all

its science, the surface area is larger. it's be like having a 16in sub. props to my homie, Bill Nye the Science Guy

[hmchaos]

for the power, is 1000W RMS x 1 @ 4 Ohms/2000W x 1 @ 2 Ohms too much? if set up properly, will the amp run more efficiently? how do you know what too much power is?

[Hopeless]

for the power, is 1000W RMS x 1 @ 4 Ohms/2000W x 1 @ 2 Ohms too much? if set up properly, will the amp run more efficiently? how do you know what too much power is?

if you set way low you may be ok. but thats overpowering the subs by quite a bit there.

[sonikaccord]

Yes the amp will just cruise along. You have to listen for stress and abnormal noises and see if the voice coil is heating from the speakers. I wouldn't recommend doing it if you don't know what to listen for though.

Power handling is really just a 'suggestion' to the amount of power you should run to a driver especially subs.

[hmchaos]

thanks again, i dont wanna have to worry about it so ill find something a little lower.

[jewelproject]

hehehehehe, 8's can still pack a punch. buddy with 2 DD1508s running on an Alpine PDX 1.1000 that i have in my closet now was pushing 142dB+

sonik's info is on point, i generally like class D monoblocks over all

i dont doubt 8's punch. but they dont slap! dont get me wrong i've seen 3 jl 8w2( i believe they were) get higher db scores than two 15 solo's.

[WilliamW]

its science, the surface area is larger. it's be like having a 16in sub. props to my homie, Bill Nye the Science Guy

No, it's a little less than 1 twelve inch subwoofer. Here is the science.

PI*R^2

That's what you need. The "Diameter" of the 8 inch subwoofer is 8 inches. The "radius," which is R, is 4. So if you take 4 and multiply it by 4 (which will give you 16) and then multiply it by 3.14 you will get 50.24. Take this number and double it since hmchaos will be running 2 of these 8 inch subwoofers and the total surface area is 100.48 square inches.

The quick and dirty for 1 12" subwofer is this. 6*6*3.14. 113.04 Square inches. So 2 8" subwoofers would sound very VERY similar to a single twelve and they can really thump. A 16 inch sub has an area of 200 square inches. (that's a lot of sub)

But that's only the surface area of it. You could get 2 8" subs that hit harder, but it has a lot of other factors that come into play.


Staying on topic, hmchaos there are lots of amplifiers that can do what you need. The biggest things to pay attention to is the ohm load on the amp itself. When you double the resistance, the power will half. When you half the resistance, the power will double.

With your subwoofers you can run the speakers in 3 different ways.
Way #1: You can run them separately in which you will need a stereo amplifier stable at 4ohms per channel that gives you the power per channel you need.

Way #2: Monoblock / Class D: If you run the subwoofers in parallel, the resistance will drop to half. So your 4ohm subwoofers will show a 2 ohm load on the amp. If that amp makes 1000 watts @ 1 ohm, then you will have 500 watts to use.

Way #3: Monoblock / Class D: If you run the subwoofers in series you will double the resistance and you will get 8 ohms showing at the amp. This isn't recommended because if you had that same 1000 watt amplifier @ 1ohm and ran a 8ohm load you would get 1000 watts halved three times. 500, 250, 125. You would only get 125 watts.

Hopefully I haven't confused too many people.

[sonikaccord]

To add to will's n00b raping post, and part 2 of my original post:

every doubling of power is only a 3 dB gain. Where 3 dB's is a noticeable change in volume level. It also works the other way if you half the power. Sometimes extracting the most power out of your setup isn't necessarily worth the hassle especially with subs.

10dB's is doubling of volume, but also 10 times the power. That's why for daily setups imo 1000W per sub is the max I would care about about running. More power above that leads to electrical upgrades and extra money.

With that being said, 750w amps at 2 ohms are pretty common and inexpensive and would fit your setup like a glove.

[hmchaos]

wow. thanks william and sonik for breaking it down "barney style." i actually understood it.