So in the last post I talked about Ohms and Wattage rating as it relates to PA speakers and amplifiers. In this part of the post I want to address another common Ohms question. What is the difference between series and parallel wiring inside of a guitar cabinet? Well first off, here’s what that looks like. Then I’ll explain.
Parallel wiring is exactly the same as described in the first post with the examples I provided about PA cabinets. Two matching impedance speakers on the same channel lowers the resistance by half.
Series wiring is two matching impedance speakers wired together to increase resistance. This would be useful if you had a couple of speakers that you wanted to run, but your amplifier was not stable at a lower ohm rating.
Series parallel wiring is very common in guitar cabinets because it allows the cabinet to retain the same resistance as its individual speakers. This makes it easier to match up cabinets and amplifiers without doing a ton of guesswork.
Here is a real world example: Marshall 1960 series cabinets typically are wired 16 ohms internally. This means that when you hook up one 16 ohm Marshall 1960 cab to a Marshall head you use the 16 ohm output. Remember the discussion from the last post where by doubling the number of speakers hooked up to a single channel of a power amp you lower the resistance by half? That’s why the Marshall cabinets are wired 16 ohms. If you want to run a stereo pair of Marshall cabinets (a full stack) there’s two 8 ohm outputs on the back of the head that you run one line into each of the cabs. This allows the amplifier to deliver more power to the two cabinets without risking damage to any component. Not everyone wants to run a full stack, but those who do can utilize the same equipment just by simply adding to their existing setup.
Now, if you ignore everything else that I’ve said up to this point and only remember one thing. This is what I want you to remember. No matter what the wattage rating, ohm rating blah blah blah is on any amp or speaker combination that you’re using, one rule trumps every other.
IF IT SOUNDS BAD IT IS BAD!
Regardless of speaker wattage and amplifier output, one thing remains the same. If it sounds like crap, then you’ve got two potential problems. Either bad matching equipment, or you are expecting too much from equipment that does not work properly together.
For example: You have a 100 watt amplifier and a 100 watt speaker. You may think that because the speakers handling capacity is not exceeded by the power amp then it must be o.k. to crank the crap out of your amp because hey, it can only make 100 watts and that’s what the speaker can handle. That should work fine, right? Completely wrong. Although matching these components mathematically makes sense, the resulting output would be terrible sounding because you are forcing the amplifier to operate at it’s utmost extreme. Therefore, you are overtaxing the amp by turning it up all the way and thus sending a distorted and dirty output signal to the speaker. So no matter how good the speaker is, or how high the wattage handling, this would still sound bad. You could hook a 1,000 watt speaker up to a 100 watt amp and crank it to the max and it will still sound like crap. This a common occurrence that you could call under powering a speaker. It’s also a common misconception that you blow speakers because you push too much power when in fact it’s just the opposite. By under powering a speaker you send the speaker a dirty, distorted, output that will ultimately produce a poor quality sound no matter what you do. By overpowering a speaker (even drastically) you get a much better result. The amplifier does not need to work nearly as hard to deliver the speakers maximum wattage capacity. Therefore, the amplifier is not being overworked and producing a perfect clean, undistorted signal at the current output level. Sure, you could blow the speaker if you cranked it up all the way, but hopefully your ears would stop you from doing that. That’s where I was going with the whole, if it sounds bad, it is bad thing.
Let me leave you with a quick analogy. Two cars, one is a 4 cylinder, one is an 8. Both cars are capable of going at least 100 mph. If you want to go 100 mph in the 4 cylinder, you need to mash the throttle right to the floor. The car eventually will get up to speed, but it will be putting way too much strain and wear on the motor to achieve that speed. In the 8 cylinder, you can achieve 100 mph by only pressing the throttle down half way. You’ve got plenty of throttle left, and could go faster than 100 mph, but you don’t need to. You only wanted to see if the car could hit 100. Thus the 8 cylinder motor is relaxed and efficient at that speed, where the 4 cylinder is about to blow up. Make sense? So the moral of the story is, listen listen listen. If you are playing and stuff sounds distorted and bad, then you are potentially risking doing permanent damage to your speakers. So if you aren’t sure when things start to sound bad, give me a call at 800-373-8393 X100 or email bfoley@daddys.com so I can sell you a pair of top of the line ears that will make it much easier for you to hear the difference.