spooki Posted January 2, 2013 Share Posted January 2, 2013 Hello again: I'm stumped once again on the right and wrong. I have an fun, old, and retubed UNIVOX 255R that has 2x12 wired parallel. My question is... The cord to feed the speakers is all one color and no markings. So how do I determine which is + or - ? It's mostly an open back amp but have gave thought to closing it up for a test run with the understanding that the movement of the cones is most important when closing one in. How do I tackle this? I tried playing a note or two with my finger on the cone, but it's really hard to tell for sure. Feels like it goes backwards, but I can't be sure. I have heard that a cone can be checked with the quick contact of a multimeter but my speakers are well marked. I need to know what I'm delivering from the amp, without doing something bad. Can that same test be run by just switching the wires with power on? Sounds a bit scary to me. Last question. If I were to leave it open in the back. Does it matter? Thanks again..... Just call me manyquestions. Link to comment Share on other sites More sharing options...
Aster1 Posted January 3, 2013 Share Posted January 3, 2013 Well, since I do this all day with rather expensive home audio & theater gear, let me tell you my trick. Find a weak AAA battery. Take the twin speaker lead and hold one of the two on the neg. of battery & just momentarily touch the other lead to the positive of the battery. You should see the cone move. Either in or out. If you have the polarity correct, (DC wise), the cone should move out. Of course if it moves in the + & - are reversed. Mark up the neg. lead now and test the other speaker. Then you're done. You've identified the + & -. Remember, just "tap the loose lead to the positive of the weak battery and release right away. You're fine with a speaker unless you end up leaving DC power to hold the cone in place. That would cause the voice coil to heat up some if you have too much current flowing thru it. (Kind of like holding a motor shaft and applying power to the motor) Capish? Aster Link to comment Share on other sites More sharing options...
L5Larry Posted January 3, 2013 Share Posted January 3, 2013 Well, since I do this all day with rather expensive home audio & theater gear, let me tell you my trick. Find a weak AAA battery. Take the twin speaker lead and hold one of the two on the neg. of battery & just momentarily touch the other lead to the positive of the battery. You should see the cone move. Either in or out. If you have the polarity correct, (DC wise), the cone should move out. Of course if it moves in the + & - are reversed. Mark up the neg. lead now and test the other speaker. Then you're done. You've identified the + & -. Remember, just "tap the loose lead to the positive of the weak battery and release right away. You're fine with a speaker unless you end up leaving DC power to hold the cone in place. That would cause the voice coil to heat up some if you have too much current flowing thru it. (Kind of like holding a motor shaft and applying power to the motor) Capish? Aster This is not the question. The OP clearly states his question concerns the polarity of the wire coming out of the amplifier! Link to comment Share on other sites More sharing options...
spooki Posted January 3, 2013 Author Share Posted January 3, 2013 Well, since I do this all day with rather expensive home audio & theater gear, let me tell you my trick. Find a weak AAA battery. Take the twin speaker lead and hold one of the two on the neg. of battery & just momentarily touch the other lead to the positive of the battery. You should see the cone move. Either in or out. If you have the polarity correct, (DC wise), the cone should move out. Of course if it moves in the + & - are reversed. Mark up the neg. lead now and test the other speaker. Then you're done. You've identified the + & -. Remember, just "tap the loose lead to the positive of the weak battery and release right away. You're fine with a speaker unless you end up leaving DC power to hold the cone in place. That would cause the voice coil to heat up some if you have too much current flowing thru it. (Kind of like holding a motor shaft and applying power to the motor) Capish? Aster Thanks Aster but that was not I was after. I"m trying to figure out as Larry stated in another reply. How do I tell the polarity of the wires coming out of the amp? Can I just power up and briefly touch the terminals on the speaker with the amp wires? Link to comment Share on other sites More sharing options...
RIX Posted January 3, 2013 Share Posted January 3, 2013 Hey Spooki your back with another neat question. Okay lets see if i can help. Since your speaker wire leads are both the same color you need to check to see if one side is ribbed or has writing and the other smooth or blank. You see this type of making especially with lamp or extension cords. The ribbed or side with writing is the negative and the smooth positive. If your lead are not marked either way I'm afraid I don't know how to tell without test equipment or opening up the amp and I wouldn't go there. Hope that helps. Link to comment Share on other sites More sharing options...
Aster1 Posted January 4, 2013 Share Posted January 4, 2013 Guess I didn't read that totally correctly. Sorry. I don't want to get you off track here. Are we to be presuming you DON'T have an external speaker jack? If you do, then with an ohm meter check ground of ext. spk jack (or maybe even just a good amp chassis ground for continuity with one of the 2 wires from the amps speaker output transformer. (The ones going to the speakers you can't tell polarity on.) To really follow up, to know the polarity from the amp doesn't matter here. Not to sound glib, but unless you are running multiple speakers that would cancel bass if "out of phase" + & - mixed up "it don't matter. With a sine wave (sound) it requires a woofer (or any driver) to complete one positive excursion & one negative excursion to create one waveform cycle. It if goes in first then out it vs, out first then in, it don't make NO NEVERMIND (again unless you have multiple speakers on the same amp wired OUT OF PHASE. If you could send a 1hz signal thru the amp and watch if the cone moves out 1st you could then properly figure phase w/o opening up the amp cabinet. Since you have 2 speakers and must know the phase of both speakers just make sure the same wire is connected to the plus of both. I'm presuming you are wiring the speakers in parallel? Aster Link to comment Share on other sites More sharing options...
spooki Posted January 4, 2013 Author Share Posted January 4, 2013 Guess I didn't read that totally correctly. Sorry. I don't want to get you off track here. Are we to be presuming you DON'T have an external speaker jack? If you do, then with an ohm meter check ground of ext. spk jack (or maybe even just a good amp chassis ground for continuity with one of the 2 wires from the amps speaker output transformer. (The ones going to the speakers you can't tell polarity on.) To really follow up, to know the polarity from the amp doesn't matter here. Not to sound glib, but unless you are running multiple speakers that would cancel bass if "out of phase" + & - mixed up "it don't matter. With a sine wave (sound) it requires a woofer (or any driver) to complete one positive excursion & one negative excursion to create one waveform cycle. It if goes in first then out it vs, out first then in, it don't make NO NEVERMIND (again unless you have multiple speakers on the same amp wired OUT OF PHASE. If you could send a 1hz signal thru the amp and watch if the cone moves out 1st you could then properly figure phase w/o opening up the amp cabinet. Since you have 2 speakers and must know the phase of both speakers just make sure the same wire is connected to the plus of both. I'm presuming you are wiring the speakers in parallel? Aster Thanks again Aster, I'm still a little lost but let me start by answering a few of your questions. No--- there is no speaker jack. The wire that looks like a household electrical cord comes from a transformer and goes directly to the first speaker closest too the electronics. Yes --- the two speakers are wired parallel and both are clearly marked + or - . I did use my ohm meter from each speaker wire coming from the transformer to the metal chassis of the amp. I was thinking I would get an open with one, but not the case. Also as Rix mentioned, I did find very small writing on one of the wires going to the speakers. That's the closest thing for discovery that I've came up with. (and if indeed that one is the negative, I do have them backwards. I'm out of spades and they are soldered now. So I'll get them swapped later. Thanks again. Link to comment Share on other sites More sharing options...
spooki Posted January 4, 2013 Author Share Posted January 4, 2013 Hey Spooki your back with another neat question. Okay lets see if i can help. Since your speaker wire leads are both the same color you need to check to see if one side is ribbed or has writing and the other smooth or blank. You see this type of making especially with lamp or extension cords. The ribbed or side with writing is the negative and the smooth positive. If your lead are not marked either way I'm afraid I don't know how to tell without test equipment or opening up the amp and I wouldn't go there. Hope that helps. Good idea Rix, I had to get my magnifying glasses out and sure enough...... little tiny letters and such. Thanks man........ Link to comment Share on other sites More sharing options...
spooki Posted January 4, 2013 Author Share Posted January 4, 2013 Wow! I think I finally figured out how to reply without all the past info added in. Sweet......... Big thanks to both Aster and Rix for your help. I switched the wire with the ( little tiny writing ) on it to the negative post on the first speaker in line, and I now am pushing both speakers. Mission accomplished. To Aster: As little as I know about your explanation's and the world of speakers, I found it very educational. My direction of thought was I need the speakers to be pushing because I am thinking about closing in the cabinet . It is an old stand up combo and I will of course leave the head part open for cooling purpose. But thru all my studies in past. They made clear a closed back cab needs to be pushing. Not a big deal with an open back. Is this true or false in your opinion? Thanks again to all and I find embarrassment in asking so many questions. I really don't play that well but sure do enjoy learning and trying new things. The tinkering and learning helps keep the frustration away of not playing well. Stay focused and keep at it. Right????? :unsure: Many thanks again.......... Link to comment Share on other sites More sharing options...
Aster1 Posted January 5, 2013 Share Posted January 5, 2013 Thanks again Aster, I'm still a little lost but let me start by answering a few of your questions. No--- there is no speaker jack. The wire that looks like a household electrical cord comes from a transformer and goes directly to the first speaker closest too the electronics. Yes --- the two speakers are wired parallel and both are clearly marked + or - . I did use my ohm meter from each speaker wire coming from the transformer to the metal chassis of the amp. I was thinking I would get an open with one, but not the case. Also as Rix mentioned, I did find very small writing on one of the wires going to the speakers. That's the closest thing for discovery that I've came up with. (and if indeed that one is the negative, I do have them backwards. I'm out of spades and they are soldered now. So I'll get them swapped later. Thanks again. Spooki, You may have done this already, but you would need to have no connection to any speakers when you test the amp speaker leads to chassis ground. Does the amp have a grounded AC power cord plug or just a 2 wire style? Unless something has been changed since I was in my Audio & Electronic Engineering days in school, sealed or unsealed, one out-one in motion of a woofer (or driver) makes one cycle. From 0 to full positive amplitude back to 0 then to 180 degree out of phase neg full amplitude back to 0 again. Just for my own curiosity, why are you wanting to seal the speaker box? If it was designed correctly open & the enclosure back was designed correctly, it will be much more efficient than a sealed box. You just need the sound off the back wave of the speaker to have enough time delay before coming around the front to avoid a cancelling effect. Glad you found the "tracer" on one of the wires. If you are still really concerned if it is correctly negative you will need to test to ground. Most amps use ground as a common potential from the transformer, but not all. Best of luck Aster Link to comment Share on other sites More sharing options...
spooki Posted January 6, 2013 Author Share Posted January 6, 2013 Spooki, You may have done this already, but you would need to have no connection to any speakers when you test the amp speaker leads to chassis ground. Does the amp have a grounded AC power cord plug or just a 2 wire style? Unless something has been changed since I was in my Audio & Electronic Engineering days in school, sealed or unsealed, one out-one in motion of a woofer (or driver) makes one cycle. From 0 to full positive amplitude back to 0 then to 180 degree out of phase neg full amplitude back to 0 again. Just for my own curiosity, why are you wanting to seal the speaker box? If it was designed correctly open & the enclosure back was designed correctly, it will be much more efficient than a sealed box. You just need the sound off the back wave of the speaker to have enough time delay before coming around the front to avoid a cancelling effect. Glad you found the "tracer" on one of the wires. If you are still really concerned if it is correctly negative you will need to test to ground. Most amps use ground as a common potential from the transformer, but not all. Best of luck Aster Hi again Aster. You have been great help throughout this and I follow you on the cone movement. It makes perfect since to me and I'm happy with that. I can't tell any difference either way regardless. I just play at home and never push that hard anyway. Just always find excitement in learning. To answer some of your questions. Why close it up? Just for grins mostly. I have changed out the old speakers and one of the new is the Swamp Thang. So basically, I've interrupted the original design and purpose, and as I said, ( just for grins sake ). I'm at a happy point now and going to leave as is. It was indeed a 2 prong plug until today. I have been meaning to change it and finally did. I never got shocked, but I run my two amps in stereo though my RP 350 pedal board and was always getting a small pop thru the speakers when touching one or the other for adjustments. That is gone now. Not knowing much about household wiring, I looked at many conversions online. I never did see anything like what is called the dead mans cap. The two wires consisted of one going to the fuse, the other going to a post on the transformer. Same color but the small lettering went to the fuse. What diff? when you have a plug that goes either way? I wired as such. Green to base of metal chassis, black to the fuse, and white to the post on transformer. No more, no less. Am I missing something? All seems fine and like I said, that annoying pop thru the speakers on the touch this, touch that, is gone. I do realize I had no business going in, but did stay away from everything else. I have been automotive wiring all my life and know the potential of condensers and stuff. We used to give a points condenser a quick charge per battery voltage and you could get a pretty good bite from it. Ha! just dated myself. Points? what are those? Anyway, thanks again for all your help and education. I'm good with the outcome unless you find a possible glitch or fault in the way I wired it to 3 prong. I'm sure I'll be back again with more questions of a different sort. Link to comment Share on other sites More sharing options...
Aster1 Posted January 7, 2013 Share Posted January 7, 2013 Just always find excitement in learning. To answer some of your questions. Why close it up? Just for grins mostly. I have changed out the old speakers and one of the new is the Swamp Thang. So basically, I've interrupted the original design and purpose, and as I said, ( just for grins sake ). I'm at a happy point now and going to leave as is. I'm sure I'll be back again with more questions of a different sort. Yeah, I know about changing things just for the fun of it. And it can be fun too. Sometimes for me as much as playing. Keep learning & tinkering. As long is it's safe, you will have fun & learn stuff. Don't go cutting up a real vintage piece of gear unless you don't care about the value of it however!! Aster Link to comment Share on other sites More sharing options...
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