speaker break in transformer question

[loudthud]

Some years ago I bought a gizmo from Parts Express that measured Thiele-Small parameters. The instructions suggested that speakers be broken in before measurement and there was a 5Hz output from the device that could be used for that purpose. I used a function generator set to sweep mode. It doesn't take much power to get a big cone excursion at very low frequencies and it's not a pain to listen to it.

[The Dude]

For clarity of my own opinion. I said, "I don't break in speakers". That doesn't mean I don't think there's validity to the process. I just don't mess with it.

[bob p]

There are some people who swear by it, just as there are some people don't think it's worth their time. If I had to guess, I'd say that end users are more likely to fuss with this sort of thing than the tech types. Like you, I thought it was a diminishing returns sort of thing so I don't mess with it either.

[bob p]

Some years ago I bought a gizmo from Parts Express that measured Thiele-Small parameters. The instructions suggested that speakers be broken in before measurement and there was a 5Hz output from the device that could be used for that purpose. I used a function generator set to sweep mode. It doesn't take much power to get a big cone excursion at very low frequencies and it's not a pain to listen to it.

The first time that I reconed a speaker, I followed instructions that directed a 30 Hz signal be used to assist in centering the cone as the adhesive set. I decided to use a signal generator and a stereo receiver to do this, and I was careful not to use too much power. It didn't take long for the stereo receiver to pop the fuses on it's output board. Stereo receivers don't like the duty cycle that comes with 30 Hz sine waves.

[Enzo]

Oh amen on the don't mess with it. I have no doubt the break in makes a difference, but it is a small thing and I do not concern myself with it unless a customer brings the specific complaint.

[Randall]

I got the inspiration to cobble up a break in jig from reading Ted Weber, who knew a thing or two about speakers. I did it mostly for fun. I hardly have even used it because it's a difficult to actually be around. I do the math to make sure it doesn't get over ted's 30% mark. For the record, I installed the four speakers in the SR, and hooked up the jig and let 'er rip.... For no more than 20 minutes. Gave me fits, and I quickly decided it wasn't good for the cab or chassis to rattle at one frequency at that level for that long. Even the power lamp glass was resonating. I pulled it and agreed with the customer that playing his cd thru it or even a looper pedal of his own playing would be just as good or better.

[bob p]

The last time that I did break-ins was at home, 10 years ago, with guitar cabs. I used CDs on a CD changer. Eight days of high volume, out of phase speakers at the far end of the house practically drove me crazy. The CDs were bad enough, but there's just no way I could have tolerated a monotonic sine wave or a sweeping signal -- they really grate on you after only a short while.

Back in the late 70s when we were working on the EV TL box designs we used a pink noise generator that randomly changed bands to stress test the systems. Granted, the anechoic chamber made it easier on the ears, but pink noise was a lot easier to listen to than sine waves. If you can get your hands on a noise generator, or a CD of randomized bands of pink noise, I think that would be a better approach than the weber transformer method. As a ghetto method at home I sometimes used inter-station FM static to feed horn drivers; that was in the days before every FM receiver had automatic noise suppression.

Today I just can't bring myself to do break ins. In the absense of a proper noise generator I think that feeding a real music signal in the relevant frequency bands is the best approach. A looper pedal or any other sort of re-amping method sounds like a good approach. I think that if you're going to do it for a guitar cabinet, what would matter is giving the cabinet real-world type of signal inputs, rather than an LF sine wave that's just intended to loosen the suspension. I think Weber's method is actually pretty lame. It's definitely a ghetto method used by a small cap builder and recommended for the DIY guy who doesn't have proper test equipment that the large cap manufacturers use.

FWIW, my comments about break-in in this thread are aimed at the guitar speaker application, not PA or sub applications. It's true that driver compliance matters in TS applications, but with the kinds of speakers that are popular with guitarists, Qts tends to be high enough to preclude their use in TS arrays.

I can't say that I agree with the comment attributed to Bill F that break-in primarily acts to lower Fs.

A little math helps to explain why my guitar break-in experiments were so disappointing. When you're doing a Weber type break-in, instead of just blindly applying sine waves it might be helful to understand exactly what you're doing. What you're actually trying to do with LF sine wave break-in and chemical doping is to modify the total Q of the system (Qts).

Qts = ( Qms * Qes) / ( Qms + Qes )

Total Q for the system (Qts) is derived from the combined effects of the mechanical suspension (Qms) and the effects of the electrical suspension system (Qes). Qes won't really change with break-in, though Qms will change, and Qts changes because of it. The break-in effects are most noticeable in drivers that have Qts in the range below 0.4. Popular guitar speakers typically have Qts in the range of 0.7 or more and break in doesn't lower Qms enough to help all that much, so I don't bother with it for guitar speakers.