How to Bridge Subwoofers

Step-by-Step Guide

1. 1

   Step 1: Locate the specification labels for your system.

   Your amp should have a label near the speaker output jack that indicates the output power (measured in Watts) and the minimum impedance (measured in Ohms).
   
   Be sure that your use the values for bridged mode, it is usually double the minimum impedance as stereo mode (meaning you need a much high impedance to run a bridged system) and up to four times the power output.Your sub-woofers should also be labeled with an impedance value (in Ohms) and a value indicating the maximum power input that they can handle (in Watts).The majority of amps on the home theater market are only stable at 4 ohms when bridged.
   
   Most car stereo amplifiers can do 2 ohms.
2. 2

   Step 2: Write down these values.

   You should have at least four different values written down.
   
   Amp Bridged Output Power Amp Bridged Minimum Impedance Speaker Power Rating Speaker Impedance , To do this you should add together the speaker impedance number for all of your speakers.
   
   You want the impedance to be at least equal to the minimum impedance value of your amp on each channel, but not to exceed 16 Ohms unless your amp is specifically rated for impedance values above 16 Ohms.The formula for finding total impedance for speakers wired in series is Z1 + Z2 + Z3 …. = Ztotal.
   
   Where Z is the impedance of a given speaker.
   
   For example, if you have three speakers with impedance values of 4 Ohms, 6 Ohms, and 8 Ohms your total impedance wired in series would be 18 Ohms (4+6+8=18).
   
   The formula for finding total impedance of speakers wired in parallel is a little trickier.
   
   It is (Z1 x Z2 x Z3…) / (Z1 + Z2 + Z3…) =Ztotal.
   
   So say you have two speakers with impedances of 6 Ohms and 8 Ohms.
   
   This time it would look like this: 1) Multiply the values. 6 x 8 = 48 Ohms 2) Add the values. 6 + 8 = 14 Ohms 3) Divide the top by the bottom to find your total impedance. 48/14 =
   3.43 Ohms (rounded) You can also use an impedance calculator such as this one http://www.speakerimpedance.co.uk/. , This will be based upon the total impedance and the power output of your amplifier.
   
   You can use variations of Ohm’s Law to do the calculations yourselfor you can refer to the online calculator above.
   
   You do not want to overpower and blow your speakers. , The output power should be stamped near the output jack on your amplifier and measured in Watts.
   
   You speakers should also be labeled with a wattage.
   
   The output wattage should meet or exceed the sum of all of your speakers.
   
   For example if you have two subs that each pull 200 W, you would want an amp that produces a minimum of 400 W.
   
   Ideally you would have an amp that produces more than what is required, this is referred to as "head room" and helps to avoid clipping., Wiring powered devices can be dangerous.
   
   If you are working on a car stereo system you can simply disconnect the battery terminals.
3. 3

   Step 3: Calculate the total impedance of all of your speakers.

4. 4

   Step 4: Calculate the power each speaker will receive.

5. 5

   Step 5: Verify that your amp has enough power for your subs.

6. 6

   Step 6: Unplug your equipment.

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