[Harp-L] Breaking in speakers (Ted Weber method)

[George Brooks <gbrooks@xxxxxxxxxxx>]

Below is a cut-and-paste on breaking in speakers from Ted Weber's FAQ . 
 I have used his method on two different amps with great results each 
time.  The FAQ is at:

http://www.webervst.com/sptalk.html

You will have to scroll down quite a ways.  The cut-and-paste below 
gives you all you need to know, but the FAQ entry also contains, at the 
bottom, a handy little applet that lets you plug in the speaker 
impedance and power rating and calculates the break-in voltage for you.

Warning: this method produces a very loud hum.  You will probably not 
want to be in the same place as you amp or speaker while this is going 
on.

===========================

From: Jeff Brinson

I recently purchased a replacement 12" speaker for my amp. I like its 
tone, but it seems a little shy on the low end and a little tight 
overall. Is there anything I can do to loosen it up or improve its 
tone? I've heard of people beating on the magnet and other methods, but 
I'd like to know what you suggest.

Jeff, most speakers are a little tight when new due to the stiffness of 
the cone surround and spider. After several hours of playing at high 
levels, they begin to loosen up and have more overall body and sound 
projection. I've heard of beating on the magnet also, and quite 
frankly, I'm not sure what benefit it is supposed to yield. An AlNiCo 
magnet is a metal alloy, so it conducts electricity. This means that 
physical shock will cause the magnet to induce an electrical current 
into itself, which will in turn generate a magnetic field, and that 
field, if strong enough, can partially demagnetize the magnet. A 
ceramic magnet, on the other hand, is essentially non conductive and 
therefore has a very high resistance. That's the reason powdered 
ferrites are used in high frequency coils and transformers, so currents 
won't be induced in the core and adversely affect the transformer 
action at high frequencies. Ceramic speaker magnets are also made of 
powdered ferrites. If a person was purposely trying to decrease some of 
the magnetism of a speaker, the intent is probably to lower the self 
damping of the speaker itself thereby allowing the speaker resonance to 
add some low end. In my opinion, that's a poor method of increasing the 
low end.
OK, on to '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 
filament transformer. 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. Another option is to use a variac into 
the primary side of the 12.6 volt filament transformer and 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.