Bass Lesson 24 - Ohms, Watts?

If you’re looking into upgrading your amplifier to a head and stack setup, then you will need to know what ohms, watts, and other electrical terms mean. It's important that you or whoever is selling you gear knows what they are talking about so that you are getting what you fully paid for, and so you don't destroy whatever you did pay for.

The first thing to know is what an ohm is. An ohm is a measurement of resistance in an electrical circuit. The more ohms, the more resistance or more difficult it is for electricity to travel through the circuit. The more ohms, the more football players there are before you reach the end zone. Since some materials conduct electricity better than others, we need a measurement of how well they conduct, and that measurement is ohms. Nickel does not conduct electricity as well as copper, so we can assume that nickel’s measurement of resistance is greater than copper’s. More resistance = more ohms. 

 

Watts is the measurement of power that an amplifier can provide to make the speakers vibrate. This is always shown at a certain ohm reading. The Ampeg SVT – 350, for example, can provide 350 watts @ 4 ohms. This means with 4 ohms of resistance, the SVT – 350 can provide 350 watts of power to the speakers, and at 8 ohms, it can provide 200 watts of power. Because 8 ohms has more resistance than 4 ohms, some of the wattage is used to actually get the power to the speaker (like if you ran to a track meet, you would use some of your energy actually getting there and then have less total energy to compete with). Now let’s put this information to use.

Using an SVT – 15EN cabinet with this amp is acceptable, and here’s why. The 15EN cabinet has a resistance rating of 8 ohms and can handle 200 watts at this rating (all ohm and wattage information is found on the back of equipment). Since the cabinet is rated at 8 ohms, we can look at the amplifier and see how many watts of power it can provide at 8 ohms. The SVT-350H mentioned earlier can provide 200 watts of power at 8 ohms. It looks like the cabinet can handle this load. If the head produced over 200 watts of power at the 8 ohm rating, then the speaker may physically break or otherwise be damaged. Be sure to check how much power your cabinets can handle before just plugging them in.

In short, be aware of how much your amplifier will output at different ohm ratings. In music gear, ohms are almost always either 4 or 8. Also be aware of how much your speaker cabinet can handle and what ohm level it operates at. Keep these factors in mind and you'll be safe. If you have any questions about this lesson, you can check out the forums. If you have specific questions about your gear, it is advised that you call the appropriate company for specific stats.