Question about speaker polarity

[rollo greb]

I've just finished putting a new speaker in my amp, a Silvertone 1472 1X12 combo. The old speaker didn't have the polarity marked on it, so I'm not sure how to wire up the new one.

The amp has 3 lugs below the OT, and I've found out that they are a 4 ohm and 8 ohm tap, and ground. Would the positive go to the tap (8 ohm speaker), and the negative to ground? Or does it even matter with speakers?

Thanks, this is my first speaker replacement!

[Rob Mercure]

You're dealing with alternating current which drives the speakers and so for a single speaker it doesn't matter. The +/- marked on the speaker (which is an arbitrary designation - for what it matters it could be @ and *) are there so that when you have multiple speakers the cones of all of then will move in the same direction at the same time - it is important to match the terminal designations.

If it makes you happier connect the ground lead to "-" and the other output tranny lead to "+" cuz I suspect that's what most folks do. But, again, for a single speaker it doesn't matter (usually when you connect a batter + to the + marked terminal and the battery - to the - terminal the speaker cone will move outward from the cone side - but this isn't an industry standard only a common practice.).

Rob

[Enzo]

Where it matters is when multiple speakers are in use. For example in a combo amp with 2 or 4 speakers, they all must move the same directions together. And if you use an extension cab, its speakers must move the same way as the internal speakers.

[Robert M. Martinelli]

Hi,
there is a very simple yet very effective way to determine a speaker' s polarity - connect a 1,5 V battery to the speaker, first in one way and then reversing the polarity : the + on the speaker will be the terminal which, when connected to the battery' s +, causes the speaker' s membrane ( "cone" ) to move "forward". ( this means that, when an audio signal will be sent to that speaker, the positive portion of the signal will move the cone forward from the resting position ).

This could be very helpful to quickly match the phase on multiple speakers systems ( in case their polarity is not known ) to eliminate the risk of substantial losses on the low end due to out-of-phase wiring.

Hope this helps

Best regards

Bob

[Robert M. Martinelli]

Originally Posted by voxrules!

Hi,
there is a very simple yet very effective way to determine a speaker' s polarity - connect a 1,5 V battery to the speaker, first in one way and then reversing the polarity : the + on the speaker will be the terminal which, when connected to the battery' s +, causes the speaker' s membrane ( "cone" ) to move "forward". ( this means that, when an audio signal will be sent to that speaker, the positive portion of the signal will move the cone forward from the resting position ).

This could be very helpful to quickly match the phase on multiple speakers systems ( in case their polarity is not known ) to eliminate the risk of substantial losses on the low end due to out-of-phase wiring.

Hope this helps

Best regards

Bob

Sorry Rob, I didn' t read completely your post, you gave the same advice before - My apologies

[Enzo]

I find a 9v battery a lot easier to use than a 1.5v cell.

[Robert M. Martinelli]

Of course a 9V battery is a lot easier to use, the reason why I use a 1,5 V cell is to limit the current flowing through the coil, DC resistance is always a little lower than the AC impedance, usually a 4 and 8 Ohm speakers have respectively 3 an 6 Ohms DC resistances. That would mean 3 and 1,5 Amps flowing through the coil, and though this is no big deal for big power speakers, it could damage weaker coils. Maybe I' m just overly cautious......but given the price tags speakers have nowadays, my empty wallet, not to mention my wife threatening me with a gun, maybe it' s better this way

[Enzo]

Wow, my 9v battery doesn't put out a very convincing 3 amps. A 9v power supply might.

9VDC represent the peak voltage. of an audio signal of about 6VAC RMS. That would be about the same thing as a 9 watt transient through the speaker. That would be dangerous to a little transistor radio speaker, but any guitar speaker would have no problem with it. Assuming the voltage actually holds up at 9. And it doesn't. A couple 9v batteries on my bench here drop to under a volt when across a 4 ohm speaker. Even at a whole volt, that represents about a 1/4 watt into a voice coil of 4 ohms. Oops, even less, I forgot to make that peak. Fresher batteries might hold up a little more, but they won't throw out 3 amps.

Nothing at all wrong with being careful, but for speakers we encounter in our amps, a 9v is perfectly safe. We just touch it there momentarily anyway. In fact if we held it there, it would just run the battery down quick and the battery would get pretty warm.

[Robert M. Martinelli]

Enzo, you' re right, as I told you I was only overly cautious, actually I never sat down to calculate the current, just thought a 1,5 V cell was safer.... maybe I' m getting old, or maybe I' m just too scared about being shot by my wife
( only kidding, she' s the sweetest and most patient person in the whole world, bet no one else could have resisted so long living with me..... )
Regards
Bob

[Enzo]

Well, it's not like there is anything wrong with using a 1.5v cell. There are usually multiple ways to get the job done.