I recently bought 3 10" db104 from frys..each are 4 ohms...with 270rms...if i was to wire them into a parallel circuit i would create 1.333 ohm......so if i was to get a monoblock 1 ohm stable amp..how many watts should i get the amp in?...


how do you determine what kind of amp you should get anyway..(wattage in relation to how u wire them)...just other questions i have been wondering about....

 

An 800 watt amp should pick them up good.

 

Well, when they are in parallel, each woofer will present its full load across the amp output, so you just need to add each woofer's rated wattages, in this case 3 x 270 = 810W RMS. This is what you should match to, so rgarjr is right. The amp is usually matched to the total RMS power.
When they are all in series, the output voltage is divided up among the woofers, so output volume is lower at a given volume (voltage) setting. You compensate for this by turning the volume up higher. When you do this, you will crank it up until the perceived loudness is about the same as it would have been for the parallel case. So guess how much power you need? SURPRISE! 810W.
Having said that, there are pros and cons to series vs. parallel. In series, you could run out of available voltage when trying to crank up to achieve loudness - you can hit the battery supply rail and you're done, that's all you get. The other biggest con with series is that the woofers will have more of an effect on one another, especially if they are not perfectly matched.
In your case, for (3) 4 ohms in parallel, the 1.3 ohm equivalent is a nominal value. The actual instantaneous impedance will vary dynamically with the music. So better get an honest amp, one that will handle the high current requirements of the low impedance. Don't forget that your electrical system also has to provide the current to the amp, and driving 1 ohm could overstress your car's electrical system if you aren't careful. I'd definitely put in at least a 1 Farad cap, right near your amp, for the added current demand.

 

Thks for the feed back..i mite need some help later on regarding adjusting the amp...wait so if the subs are in a series circuit..it still needs a 810 watt amp...?...how will the power be distributed....say i buy a 1200 rms mono amp....is there anyway i can "turn it down" to compensate for the 810 rms it requires?...sry i just started gettin into audio for my car...

 

Power will be distributed roughly equally among the 3 woofers if all 3 are in series.
You can get a 1200W amp, you just have to be careful with 2 things: 1) you'll have to turn the gain down, 2) you may have an even greater drain on your car's electrical system.

 

Bigger amps require more power, so unless you are planning on getting a high current alternator and an optima yellow top, I would stay within that range.

 

so..... either way in series or parallel...i will need atleast a 810 watt amp to drive them...?

....may need some help later on on tuning the amp guys..thks

thks for all the feedback guys .!