What is the best way to connect speakers or cabinets?
Wiring up speakers to provide the most effective load and making sure that all of them are in phase will help in creating the best sound possible. This is not too difficult, as long as you understand a few things about loading and how to connect your speakers to provide an optimal resistive load.
MESA/Boogie amplifiers can handle 4 and 8 ohms effectively. Never run below 4 ohms in a tube amplifier unless you are absolutely certain that the system can handle it properly; this can cause damage to the Output transformer. A few of our bass amplifiers can handle 2 ohms effectively without damaging them. Please consult your owner's manual if in doubt about your amplifier's impedance handling capability. You can always have a higher resistance (16 ohms plugged into an 8 ohm speaker output, for example) without damaging results, but too low of a resistance will likely cause problems.
Wiring Multiple Speakers
There are generally three ways to wire multiple speakers together. They are as follows:
Series - When you wire (hook-up) speakers in Series, the speakers resistance (as measured in ohms) is additive - i.e. putting two 8 ohm speakers in Series results in a 16 ohm load.
Parallel - When wiring in parallel, the resistance of the speakers decreases. Two 8 ohm speakers wired (hooked up) in Parallel results in a 4 ohm load. It’s easy to calculate the effect of a resistive load when all the speakers are all the same resistance. It is really not suggested to wire different resistive load values in Parallel (8 and 4, 16 and 8 etc.) The formula for figuring the total impedance in Parallel is the multiplication of the two loads divided by the sum of the two loads - i.e. putting two 8 ohm speakers in Parallel results in a 4 ohm load. Connect the Positive side of Speaker A to the Positive side of Speaker B - Connect the Negative side of Speaker A to the Negative side of Speaker B.
Combination of Series & Parallel - This is really just two sets of Series wired speakers connected in Parallel. This is how you maintain a consistent load with multiple speakers. The importance of this is more evident when you have more than one cabinet to connect to your amplifier. This is when you need to figure out the loads and how to wire them up without applying too low of a resistance on the amplifier.
To wire a 4x12 cabinet in Series/Parallel where four 8 Ohm speakers are wired in Series/Parallel equaling a total load of 8 Ohms (as in the illustration below):
- Connect Positive side of Speaker A to Positive side of Speaker C.
- Connect Negative side of Speaker A to Positive side of Speaker B.
- Connect Negative side of Speaker C to Positive side of Speaker D.
- Connect Negative side of Speaker B to Negative side of Speaker D.
Connecting Cabinets to Amplifiers
Matching - When connecting speakers to an amplifier and you have only a single speaker, you just match that single speaker's impedance to the amplifier, and you are done. In many cases, you will have a number of speakers, and then you must calculate the “load” that the amplifier will need to support. When a Combo amplifier is used, think of the amplifier's chassis as a head and the speaker(s) as a separate cabinet. Plug your Combo's speaker(s) into the amplifier chassis as you would any extension cabinet.
Mis-matching - When running a higher resistance (for example: 8 ohm output into 16 ohm cabinet), a slightly different feel and response may be noticed. A slight mismatch can provide a darker smoother tone with a little less output and attack. This response is a result of the amplifier running a bit cooler.
Sometimes when using more than one cabinet a mismatch will be the only option. The connection in the following illustration represents roughly a 5.33 ohm load.
(8 ohms x 16 ohms divided by 8 ohms + 16 ohms)
It is also fine to use a Series or Parallel Box to achieve a safe mis-match.
Paralleled Out Jacks - Lastly, the Paralleled Out jack found on the jack plate of most of our cabinets allows you to plug one cabinet into another in a parallel connection. For example, plugging one 8 ohm cabinet into the Paralleled Out of another 8 ohm Cabinet will create a 4 ohm speaker load for your amplifier. Therefore, make the connection to your amplifier by plugging the first cabinet (that has the second plugged into its Parallel Output) into the 4 ohm speaker output of your amplifier. This connection would be equivalent to plugging each 8 ohm cabinet into two of an amplifier's 4 ohm speaker outputs. This cabinet feature come's in really handy when there is only one speaker output of the necessary impedance is found on an amplifier.