Odd impedance?
|
Bronze Member Username: Sevin7Post Number: 87 Registered: Apr-05 | if you wire 3 dual 4ohm subs you get a 2.67ohm load: http://www.crutchfieldadvisor.com/learningcenter/car/subwoofers_wiring.html?subs =3&impedance=DVC4x2 I dont have 3 or want 3, but im curious, how can you tell how much power your subs are getting? No amp tells you how much it puts out @ 2.67ohms, do you just estimate between the 2 ohm and 4 ohm rating? |
|
Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1121 Registered: Sep-04 | If you have a regulated power supply and are running the amp within its limits then power should double every time you halve the load. Its a little more complicated when you have a crazy impedance like 2.67 ohms. An amplifier simply provides a specific maximum voltage at its highest output and you can use this formula to figure out how that relates to the load your driving: P = V^2/R V^2 is a constant if the amplifier is running within its design parameters so once you figure out what V^2 is you can just plug any resistance into that formula to figure out how much power your amp "should" be developing. Example: Your amplifier provides 200 watts into a 4 ohm load. 1) figure out V^2 V^2 = P*R = 200*4 = 800 2) plug in a resistance into the first formula to find the aproximate maximum power output. P = V^2/R Power at 2 ohms = P(2) = 800/2 = 400 watts makes sense right? Power at 1 ohm = P(1) = 800/1 = 800 watts again it makes sense and is easy to figure out w/o the formula. Power a 2.67 ohms = P(2.67) = 800/2.67 = 299 ~ 300 watts Bingo! You can use this for any load. Say you had 3 4 ohm drivers You can use RF's site or another formula to figure out the equivalent resistance. Series is easy. You just add em up. For parallel drivers its: Req = 1/(1/R1 + 1/R2 + 1/R3.... + 1/Rn) = 1/(1/4 + 1/4 + 1/4) = 1/(3/4) = 4/3 or 1.34 ohms just like it says on RF's site. If you have the same amp then P(1.34) = 800/1.34 = 597 ~ 600 watts If you use 4/3 instead of the 1.34 aproximation you'll get exactly 600 watts. If you have a fair grasp on basic algebra its not as difficult as it looks.  If you want to figure out how much power your amp should deliver just calculate the equivalent resistance by using the Req formula or a site like RF's and then do steps 1) and 2) and you're golden. -Fishy |
Main Forums
Today's Posts- Home Audio Forum
- Home Video Forum
- Home Theater Forum
- Car Audio Forum
- Accessories Forum
- All Forum Topics