Using a Variac on speakers - a quiet idea

[rooster]

Jim - Eh? I'll take your word for it but electrically this is impossible since a 60 cycle wave from the wall socket is symetrical. Well, at my house anyway. Which is to say that once a half cycle completes, the speaker would never know if it started it's motion with an 'in' or 'out' movement. You see this right?

This said, I have this very odd article apparently written/authored by Ken that talks about Fender 59 Bassmans vs. Marshall Plexis. I am not clear whether he actually wrote it though because they spelled his last name wrong, 'Fisher'. In it he says some things that are incorrect and now you have brought it all back to me. !! Anyway, it was published by GP mag some time ago, a special edition called "The Marshall Story". Did you ever see this? I will copy it and post it. ...But first I have to go fetch it. This will take about two weeks, long story.

[Scumback Speakers]

Jim - Eh? I'll take your word for it but electrically this is impossible since a 60 cycle wave from the wall socket is symetrical. Well, at my house anyway. Which is to say that once a half cycle completes, the speaker would never know if it started it's motion with an 'in' or 'out' movement. You see this right?

This said, I have this very odd article apparently written/authored by Ken that talks about Fender 59 Bassmans vs. Marshall Plexis. I am not clear whether he actually wrote it though because they spelled his last name wrong, 'Fisher'. In it he says some things that are incorrect and now you have brought it all back to me. !! Anyway, it was published by GP mag some time ago, a special edition called "The Marshall Story". Did you ever see this? I will copy it and post it. ...But first I have to go fetch it. This will take about two weeks, long story.

In testing the speakers in the out of phase position, the suspension and cone didn't seem to move as freely as the ones that were in phase. Can't tell you why, and electrically it may make no sense, but that's what I felt/heard when testing them after being in the FBI box for 15-20 hours.

This probably won't be the last time that what I've experienced/heard/felt didn't jive with theory, though.

[rooster]

One other thing, when the speaker is in a Plexi circuit - or an amp with the same phase inverter, driven to distortion, the 'in' cycle of the speaker is very different than the 'out' cycle - not as symetrical. So, this said, it is possible that an amp of this type with the speakers wired reverse polarity would sound different than if it was wired forward polarity.

And that should be interesting to some. It also speaks to the article I referred to... although Ken (if he wrote the article), doesn't seem to focus on this exactly. Which is all the more confusing. Eh, I'll post the article.

[aflynt]

Sorry to resurrect this old topic, but I'm playing around with breaking in a couple Celestion Heritage G12-65s for my #102 Dumble clone and have a few questions about this technique. I rigged up the two speakers as described in the first post with them facing each other with 1/2" foam separators around the edges. I have them hooked up to the the variac in series, out of phase.

I noticed a few things that are a bit curious:
- with both speakers facing each other it's quieter with one speaker hooked up to the variac than two. (I double checked the voltage on each speaker to make sure it was the same both ways.)
- with both speakers facing each other and only one hooked up to the variac, both speakers are moving a whole lot.
- at 13.1 volts per speaker it's still pretty damn loud.

Since it seems that facing the speakers together will cause both speaker's cones to move with just one driven by the variac, would it be necessary to use as much voltage as normal? It seems that perhaps the opposite cone is already being pushed and pulled a bit simply due to air displacement.

-Aaron

[aflynt]

- delete me -

[rooster]

OK, I know of what you speak of and I think it's a valid thought because the passive speaker seems to be quite animated. But I think the process is better when all speakers are variac'd.

I will also add that after all is said and done, one of the quietest ways to variac a speaker is to skip the speaker cab. If that is all you do then the sound should be manageable. The phase reverse method is quieter, yes, but I don't bother with this these days.. And I typically put the speaker on a concrete floor, face up, and have at it. Your voltage choice is safe, btw, but I typically choose 17VAC. Yeah, I know that may seem a bit rad but it gets the job done. Seriously, these days I laugh at my former attempts to break-in a speaker at voltages around 10VAC. In hindsight this was akin to breaking in a car motor by idling it in the driveway. A speaker with doping on it is something that needs to be shaken up.

Um, and no, I offer no warranty with this advice.

[aflynt]

OK, I know of what you speak of and I think it's a valid thought because the passive speaker seems to be quite animated. But I think the process is better when all speakers are variac'd.

I will also add that after all is said and done, one of the quietest ways to variac a speaker is to skip the speaker cab. If that is all you do then the sound should be manageable. The phase reverse method is quieter, yes, but I don't bother with this these days.. And I typically put the speaker on a concrete floor, face up, and have at it. Your voltage choice is safe, btw, but I typically choose 17VAC. Yeah, I know that may seem a bit rad but it gets the job done. Seriously, these days I laugh at my former attempts to break-in a speaker at voltages around 10VAC. In hindsight this was akin to breaking in a car motor by idling it in the driveway. A speaker with doping on it is something that needs to be shaken up.

Um, and no, I offer no warranty with this advice.

Thanks for the response! I know what you mean about running it in a cab. I tried that first and think I may have discovered the brown note when I got to about 10 volts.

I might just untie them and try it with the speakers both facing up. It's kind of funny but when I'm in the same room with the speakers they don't seem that loud, but when I go upstairs (running them in the basement) they actually seem louder.

17 volts huh? Hmm... For my 65 watt 8 ohm speaker that would work out to about 55% rated volume. I guess that would be safe.

-Aaron

[roberto]

"Variac break in times are as follows:

We can simply resume that tab: you have to run the cone at 1/3rd of the nominal power at 60Hz for 2-3 hour for light break-in, 8-12 for medium, 20-24 (in three steps of 8 hours each) for full process.

I absolutely agree about an isobox with cones facing for phase cancellation (this will make also easier to add a fan and then use a continous process), but leave at least 2 inches between the speakers.