Safe Break-in Voltage

The following was ‘Borrowed’ from Uncle Spot’s website.

I took the copy because I often link to external things only to see them disappear shortly afterwards. 

…’breaking in’ a speaker.

If you really want to speed up the breaking in period, the easiest method is to connect the  speaker to a variac. Having said that, let’s look at the precautions you need to take. Since you will be driving the speaker with a steady state signal, you don’t want to drive it at its rated power or it will burn up the voice coil. 1/3 power rating is a safe figure to use. So, let’s say you have a 50 watt speaker and it is 8 Ohm. 1/3 power is about 17 watts, and at 8 Ohm, that works out to be around 11.5 volts. Using a 12.6 volt transformer will put 20 watts into the speaker. I wouldn’t have a problem with that in our products, but just to be safe, you might want to go with a 6.3 volt filament voltage, which will put about 5 watts into your speaker. With a variac dial in the voltage you want on the secondary. That way, you can dial in the 11.5 volts we originally calculated at the 1/3 power level. I’d also suggest performing the operation in a garage or closet, because listening to the loud 60hz hum from the speaker will grate on your nerves very quickly. Also, if you leave the speaker out of the cabinet, the rear radiation of the speaker will cancel alot of the front radiation and reduce the noise. You need to lay the speaker face up though, so the cone can move as much as possible since the whole idea of this operation is to loosen up the cone and spider. Laying the speaker face down would trap air between the cone and the surface of the table and restrict cone movement. You’re going to be surprised how much the cone moves and how loud the speaker is, even at 1/3 power.

Here’s the math for determining the correct voltage to use in case you have a different wattage and impedance rating than our example above:

  1.  Take the power rating of the speaker and divide it by 3.
  2.  Take that number and multiply it by the speaker’s Ohm rating (4, 8, or 16)
  3.  Use your calculator to find the square root of that number.
  4.  The result is the voltage you need to use to drive the speaker at 1/3 its rated power.

If you decide to try this process with your speakers, don’t hold me responsible if something goes wrong. Like everything on this site, it is your decision as to what you try yourself and what you don’t.


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