speaker break in transformer question

[Randall]

I built a speaker break in jig with a filament transformer and a ac meter a la Ted Weber. I have always just used it on single speakers. Today a customer brought in 4 20 watt Webers to be installed in a Super Reverb, and he asked me to put them on the jig overnight. Question is, how does the math work out for the target of 1/3 power when they are all connected in parallel? Does the math use 8 ohms or 2 ohms?

"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. "

[nickb]

Just add the extra speaker(s) in parallel. So long as you don't exceed the transformer's capabilities. For example a single 8 ohm speaker will be about 6 ohms at 60Hz. P = V^2.R = 6.3 x 6.3 / 6 = 6W i.e the transformer supplies 6W to each speaker. 6W at 6.3V is about 1A so allow 1A of transformer current rating per 8 ohm speaker. I'd hate to be in your workshop when you are doing this.

BTW, I heard that speaker break-in was a myth...

[Tom Phillips]

AND if you decide to "beak in" multiple speakers at the same time then consider wiring them out of phase to reduce the sound level you have to listen to.

[Enzo]

Oh, Tom! You get a star for the day. I was just thinking what a pain that would be to listen to.

[The Dude]

Oh, Tom! You get a star for the day. I was just thinking what a pain that would be to listen to.

I don't break in speakers, so I had never given it much thought. That is indeed brilliant and deserving of a star.

[Tom Phillips]

Thanks for the star guys!
I only broke in a speaker with a low voltage drive from a filament transformer once a long time ago. I didn't notice any benefit that made it worth the trouble although it does seem like one way to verify that the speaker is good enough to pass the test without infant failure of any sort. What I do remember is how much noise there was riding on the AC line. I could hear all kinds of things that sounded like motors spooling up, clicks, pops & various buzzes etc. It was very enlightening and worth doing out of interest even if you are not breaking in the speaker.

[nickb]

AND if you decide to "beak in" multiple speakers at the same time then consider wiring them out of phase to reduce the sound level you have to listen to.

..or do the math, create a phased array and point it towards your least favorite building. Meh, heh, heh...

[Mick Bailey]

I was just thinking what a pain that would be to listen to.

Or your neighbours if they have to listen to 'Bitches Ain't Sh*t' played on a loop.

[bob p]

I don't understand why people fuss with transformers. If you want to break in a speaker, what's wrong with feeding it music? It's not like any of us are short on amps.

[Leo_Gnardo]

I don't understand why people fuss with transformers. If you want to break in a speaker, what's wrong with feeding it music? It's not like any of us are short on amps.

Sure, you could use music, best to choose something that has a lot of low bass content. Some techno-groove, or Switched-On Bach, reggae with Sly & Robbie rhythm section. Maybe boost the bass for better effect.

The idea is to flex the spider & surround which start out stiff. Personally I don't bother with artificial breaking-in, but I can see why people do it.

[bob p]

My personal opinion is that the breaking-in of guitar speakers amounts to over-hyped internet lore that originated from armchair tone fussbudgets, and the internet lore tends to be believed by people who read their posts... not that there's anything wrong with that, but IME I just don't find break in procedures to be all that helpful. I'm also not inclined to buy a speaker with heavy doping and then try to blindly modify the dope with chemical applications. For me, the best way to break in a speaker is to play music through it.

About 10 years ago I did an extensive break-in experiment when I bought two pair of Avatar 2x12 cabs and tried American vs. British speakers in them. I drove the speakers hard, with nonstop music and auditioned them at 24-hour, 48-hour, 96-hour and 192-hour intervals.

To make a long story short, I determined that the controlled break-in paradigm was a waste of my time. The effects of 8-days of pounding them with music made a small noticeable change in the tone of the speakers without ever really changing their tone signatures. IMO it wasn't worth the effort. I won't ever do it again, and instead I just play new speakers and make adjustments to the tone controls.

There's a thread on the forum about the week that I wasted trying to break in a pair of greenbacks that sounded too boomy and harsh in an avatar cab. That must've been 10 years ago...

[potatofarmer]

For bass and PA speakers, breaking in is actually important, and supposedly you can measure the change in Fs after just a day or two. IIRC Bill Fitzmaurice recommends 10V at 30 Hz for 24 hours, but that's assuming your woofer(s) can handle that kind of power.

Guitar speaker suspensions are much stiffer though, and considering they have an Xmax around, um, ZERO there's probably no appreciable change to the suspension over a dedicated break-in.

I did find a paper a couple years back when I was looking into this where people studied the fatigue behavior of speaker cones. I mean, it's paper; you flex it enough, it's going to weaken. Through testing they showed that there was a definite change in cone stiffness when you played sound through the speaker loudly, but interestingly enough if you never played through the speaker loudly enough, it didn't really happen and the cone would stay stiffer. Much of the change happened early and then would taper off. I'm butchering this poor paper by remembering it so poorly, but I believe the effect was audible, or at least measurable.

That's the only basis I've ever seen for guitar speaker break-in. Woofers and subwoofers need their suspensions worked out to match the design/advertised parameters too. Some people insist on breaking in headphones, but come on now.

[Enzo]

10v across 8 ohms is 12 watts or so, 10v across 4 ohms is 25 watts. That would be the main factor in can your speaker handle it.

A lot of this also depends on what you listen for and how you play. I had a customer complain of "cone cry" in a new Fender amp. He would demonstrate the "problem". I couldn't hear it, but he was very consistent when I A/B tested the two speakers in his cab one by one. But all I could hear was vibration of stuff near the amp in my shop, and various other things, but finally one test, and I could hear what he meant. There was this slight high freq buzz on the one speaker and not the other. Not really a buzz so much as an emphasis. Hard to describe. I ordered a new speaker under warranty, and left the amp with him until it came. A week or so later, I called him back to say the part was in, and he let me know as he played it, the distortion slowly faded away, and we no longer had an issue.

[bob p]

if anyone is interested in committing the time to a forced break in, bear in mind that using continuous LF sine wave power to loosen up the suspension that uses voltage anywhere near the speaker's power handling limit is going to get the voice coils hot enough to place your speaker at risk. If you integrate the area under an LF sine wave, that gives you a lot of power. and though a long duration monotone frequency will help to loosen up the suspension, and I'm not so sure that it'll do all that much for breaking in the cone across the entire relevant frequency spectrum (non-sub applications). if you're committed to doing it then chances are you're better off sweeping the signal or just pumping loud music through the driver.

[bob p]

A lot of this also depends on what you listen for and how you play. I had a customer complain of "cone cry" in a new Fender amp. He would demonstrate the "problem"...

I'm not a great player and I don't claim to have golden ears. So when I can hear a problem I figure that it's got to be real.

10 years ago Greenbacks in Avatar cabs were all the rage. I needed a 2x12 so I gave the Avatar/Greenback cab a try. I thought it sounded horrible, and described the exact problem, which was a combination of midbass boominess and harsh gritty sound on the upper E string, which I attributed to cone cry when fed any amount of power. Something about that speaker/cabinet combination was just wrong to my ears -- the setup just wasn't as great as all of the internet reviews made it out to be. Funny thing, after I started complaining about that, other people noticed it too. That's the power of suggestion for you.