PSA: Be aware of differing EPI woofer polarity!

[GordonW]

Just a heads-up/reminder for anyone who is substituting cllassic EPI woofers (the Burhoe "module" woofers, and such):

I have been just going through a bunch of the classic EPI 8" woofers, figuring out which ones are good, which ones need minor repairs, and which need to be fully reconed. In this process, I have been testing all of them with a 9V battery, just to quickly verify continuity.

Well, I have rediscovered, the need to HEED the polarity dots on EACH speaker- and if it doesn't have a polarity dot- to DETERMINE the polarity before installation, using a battery. At least ONE THIRD of these woofers have REVERSE polarity- in terms of which terminal is positive- compared to the rest. I think these may have had their magnets charged/gaussed in batches- and some batches were put together with opposite magnetic polarity! In fact, I would actually check EVERY one before installation- to make sure it's labeled consistently, with its actual polarity.

In all- no big deal, as long as that's known, though. A quick battery check to make sure that you know which battery polarity makes the woofer move outward- that's all that has to be done to find the correct polarity for that woofer...

Regards,
Gordon.

 

[leesonic]

I have eight Advent metal frame 10" woofers. One of them has reverse polarity to all the rest. I personally wouldn't use a 9V battery to test a speaker when a 1.5V works just fine.

 

[swechsler]

I have eight Advent metal frame 10" woofers. One of them has reverse polarity to all the rest.

Is that one at least marked properly?

 

[BlueVUMeters]

Wow, makes you wonder if this could be an issue with other manufacturers as well. You kind of just take for granted that the terminals are marked correctly. Reminds me of that post someone made of the edcor transformer with the lead colors mixed up.

 

[wiredbecker]

Thanks for the heads up, Gordon! I picked up a pair of EPI M50s recently, I'll be sure to check polarity next time I set up these tiny speakers for use.

 

[JRhoBurton]

I hope their tweeters did not have the same issue. They are harder to check. I have a pair of M60's awaiting refinish and reassembly.

 

[ET16]

So if you go + to +, - to -, with a battery and the cone pops out, the polarity is correct?

 

[leesonic]

So if you go + to +, - to -, with a battery and the cone pops out, the polarity is correct?

Yes.

 

[tarior]

So if you go + to +, - to -, with a battery and the cone pops out, the polarity is correct?

Unless it's a vintage JBL.

 

[sax6]

That could seriously impair sound repro... crossover out of phase ?

And it could be in only one out of two in a pair ?

Isssshhh !

 

[GordonW]

So if you go + to +, - to -, with a battery and the cone pops out, the polarity is correct?

That's correct.

Regards,
Gordon.

 

[GordonW]

That could seriously impair sound repro... crossover out of phase ?

And it could be in only one out of two in a pair ?

Isssshhh !

In theory, yes, it could affect only one unit in a pair. I've not specifically found that issue- but the ones I have, appear to be close to the same age, indicating that they used both polarity woofers at very similar times. If two cabinets of slightly different production ages were paired together (which could easily happen in a warehousing situation in a large store or store chain), back in the day, this COULD happen.

Regards,
Gordon.

 

[GordonW]

Unless it's a vintage JBL.

And even with those older JBLs- I usually wire the cabinets, so that the woofers are in correct "absolute phase" to the amp, even if that means I'm connecting the positive amp terminals to the negative speaker terminals...

At least JBL was pretty consistent, with polarity in each model. I've never seen similar-vintage, same-model JBLs have different polarity. Either they're all positive, or all negative, but never mixed, in terms of all drivers of the same model.

Regards,
Gordon.

 

[tarior]

And even with those older JBLs- I usually wire the cabinets, so that the woofers are in correct "absolute phase" to the amp, even if that means I'm connecting the positive amp terminals to the negative speaker terminals...

At least JBL was pretty consistent, with polarity in each model. I've never seen similar-vintage, same-model JBLs have different polarity. Either they're all positive, or all negative, but never mixed, in terms of all drivers of the same model.

Regards,
Gordon.

In those days, their QC was pretty top flight. Finding two with opposite polarity would be unheard of.
I know that JBL "reverse" polarity throws people who aren't familiar with it.