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Unknown speaker polarity??




 
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Author Topic: Unknown speaker polarity??  (Read 1947 times)
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wb1ead
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« on: March 05, 2018, 01:59:28 PM »

Guys and gals..because I'm into a renovation mode on some hi-end stereo speakers..it occurred to me I know not about determining the plus/negative of unmarked terminals beyond my much earlier knowledge of the ol' time battery "trick" of a D cell and movement of the cone when touched on the terminals..that one I know and yes it do work FB..however what if you have speakers totally hidden inside of cabinets that you cannot access to watch cone movement in or out?..there must be a way of measuring or adding components or voltages or whatever if all you're able to get to are the speaker wires..this is my problem here in the downstairs shack/workshop..speakers were built into the corners 40yrs ago and over the years disconnected/torn out with no markings originally put on to determine polarity..don't feel like ripping out the walls so...is there a way of determining polarity if you can't visually access the speakers??..if this was way too easy OK..but sumptin tells me it isn't   thanks all!  73 de DAVE
PS: if the answer involves test equipment tell me what that is..I got some but not a heap..
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AMer livin in "Moose Country"
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« Reply #1 on: March 05, 2018, 02:17:08 PM »

Use mono and find what polarity gives you the loudest bass.

Fred
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w8khk
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« Reply #2 on: March 05, 2018, 02:23:52 PM »

Guys and gals..because I'm into a renovation mode on some hi-end stereo speakers..it occurred to me I know not about determining the plus/negative of unmarked terminals beyond my much earlier knowledge of the ol' time battery "trick" of a D cell and movement of the cone when touched on the terminals..that one I know and yes it do work FB..however what if you have speakers totally hidden inside of cabinets that you cannot access to watch cone movement in or out?..there must be a way of measuring or adding components or voltages or whatever if all you're able to get to are the speaker wires..this is my problem here in the downstairs shack/workshop..speakers were built into the corners 40yrs ago and over the years disconnected/torn out with no markings originally put on to determine polarity..don't feel like ripping out the walls so...is there a way of determining polarity if you can't visually access the speakers??..if this was way too easy OK..but sumptin tells me it isn't   thanks all!  73 de DAVE
PS: if the answer involves test equipment tell me what that is..I got some but not a heap..

No test equipment needed, and yes, there is an easy way to get it right.

It is not really necessary to determine plus or minus terminals, that is, plus moves speaker cone forward, etc.  

The only reason for phasing the speakers is so that lower (bass) frequencies add, rather than subtract.  The bass frequencies will be accentuated if the cones in both speakers are moving forward at the same time, increasing the acoustic pressure in the room when moving forward, and decreasing pressure when moving backward.   It is easier to determine whether they are phased properly if the speakers are placed close together, but it is not absolutely necessary.  If they are built into the wall or mounted. leave them where they are.

Just play some music with the bass control advanced, (or use an audio generator set between 100 and 200 HZ (Cycles per second, for old people) and try reversing the polarity of only one speaker, while listening.  In one polarity, the base will be stronger, and with the wires reversed on one speaker, you will hear, and feel, a prominent null, or absence of the base frequencies.  Leave the wires connected in the manner that does not produce the null.

We posted at the same time!!!
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w1vtp
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« Reply #3 on: March 05, 2018, 08:54:11 PM »

I just face the two speakers in question face to face and connect for the loudest bass.

Same idea for a single cabinet with two speakers

Al
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N1BCG
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« Reply #4 on: March 05, 2018, 09:33:33 PM »

Since you’re dealing with woofers, place a single section of tissue or toilet paper over the area in front of the woofer and connect a 1-1/2 volt battery to the terminals momentarily. The movement you see initially will indicate the polarity you have.
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WBear2GCR
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« Reply #5 on: March 05, 2018, 11:11:31 PM »

Since you’re dealing with woofers, place a single section of tissue or toilet paper over the area in front of the woofer and connect a 1-1/2 volt battery to the terminals momentarily. The movement you see initially will indicate the polarity you have.


Yaaasssahhh!! Cheesy
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KC4VWU
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« Reply #6 on: March 06, 2018, 01:06:08 AM »

It's all 'bout dat bass!
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wb1ead
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« Reply #7 on: March 06, 2018, 10:36:03 AM »

Tnx guys!..yah it is all 'bout da bass..honestly I assume that midrange and especially tweeters probably doesn't much matter..??..for sure the woofers do matter..I did the "volume" test and although my cat went into "low rider" mode and headed for the upstairs..it DOES work..almost as if when hooked up incorrectly there was a major reduction in that "thump"..there is a pair of Pioneers that are finished that I did the test on..BTW BCG the tissue paper test must be for AC/DC type bands playing LOUD at a concert because even at "ear splittin'" volumes there was no detected movement of the tissue only more meowing and wailing from upstairs..the speakers were ported and rated for 200 watts..anyhoo again tnx !..I was sorta wondering if a certain voltage capacitor/resistor hookup wud tell the story but at the same time I have never seen anything ever mentioned so that's why I asked..I can rest in peace..the cat?..maybe..
73 de DAVE
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« Reply #8 on: March 06, 2018, 11:15:40 AM »

Music won’t work. That test is with a D.C. pulse from a battery, for example. Works well with JBL monitors (although many speaker terminals are labeled).

Glad you’re set! Good luck de-freaking your cat.
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KD6VXI
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« Reply #9 on: March 06, 2018, 11:29:41 AM »

The 9 volt battery trick is what we learned at autosound installation school, as much as it was.

The battery is self current limiting, and you could hear the thump.  With just two woofers or subs you'd wire them together and if you got a tick, instead of a thump, reverse one woofer.

You'd get to the point where you could tell, listening to your favorite track while you installed the rest of the system.

Phasing / polarity matters at all frequencies.  However, the lower the freq the more deleterious the effect of improper polarity.

The additional cool factor of the 9 volt was, on 4 or more subwoofer systems, you could wire all subs in parallel, then go back and see which ones where going in the negative vs positive direction.  Some subs have a couple inches of travel, it's quite pronounced.

--Shane
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WBear2GCR
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« Reply #10 on: March 06, 2018, 02:43:29 PM »

Assuming unmodified, factory built speakers, it is safe to assume that all drivers are in proper
polarity WRT to each other. THEN, the DC test will work.

It will NOT work on most midranges and tweeters mounted in a system with crossover components
because the crossovers act as high pass filters, which means a cap in series with these drivers, that blocks
the DC component.

In addition, the polarity of one or more of the mid/tweeter drivers MAY be inverted depending on the type
of xover used. For example 2nd order filters (12/dB/oct) will invert the polarity within the passband.
In which case the polarity is usually inverted by the mfr... etc.

If it's a homebrew or modified speaker, this can still be determined, but it's not so simple as a battery.

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wb1ead
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« Reply #11 on: March 07, 2018, 10:12:52 AM »

Well Bear I gotta comment on that last statement..you is absolutely right on..when I pulled apart the Pioneer 3 ways a few weeks ago..I found the woofers and midrange factory marked on the terminals with + or -..no problem however the tweeters were not..now I left the wiring in place without removing it on the tweeters and left well enuf alone..later when they were completed I decided to get into another restoration and guess what the terminals on that pair of 3 ways were?..the woofers and midrange made by RCA were marked and the tweeters WERE hooked up in the opposite way according to the markings on the 3 way crossover board..my 1st instinct was.."huh someone done put the wrong polarity wires on dem tweeters at the factory?"..maybe that's why the Pioneers were not marked to avoid confusion?..thank you for the insight on that and the rest thank you again as the built-ins are now wired correctly and yesereee the right side WAS inverted..no wonder it sounded "off"..my cat forgave me but wears earplugs now when I'm working in the shop..MEOWWW!!       73 de DAVE
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« Reply #12 on: March 08, 2018, 11:38:28 AM »


One way to determine IF the mids or tweeters are "in phase" WRT each other's channel is to place them
left and right of you, equally, and play the speakers with all of the other drivers in the boxes temporarily disconnected.
IF they are "correct" the sound will appear to come between the two speakers - a mono signal is best. IF they
are reversed WRT each other, then the sound will appear to come outside of the center and often "thrown" off
to the side, one side or the other, or else just be diffuse...

Determining the proper relationship between any two drivers in a single box is more difficult (like the mids and
tweeters).
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« Reply #13 on: March 08, 2018, 11:39:48 AM »


btw, the Pioneer drivers are almost certainly marked, maybe by a difference in the terminal shape, or a color dot
or else embossed on the insulator that holds the solder tab/terminal.
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« Reply #14 on: March 15, 2018, 05:13:40 PM »

The german manufacturer of drivers and speakers Visaton ( http://www.visaton.de/en/literatur/software ) has an EXCELENT software to design speakers. They design with the real speaker impedance and characteristics, Thiel-Small parameters etc and not just with e.g. 8 Ohms. It is freeware
There you can see the effect of reversing tweeters and mid-tone drivers. I used that program to design a two-way system and had real good results conform the predictions.
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WBear2GCR
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« Reply #15 on: March 16, 2018, 12:13:41 PM »

Yes, simulation software like the one from Visiton is good.
No doubt it is much better than "shooting in the dark".

But, one needs the T/S parameters of the drivers.
In the case of old or unknown drivers, one would need to measure the parameters.
This is really not terribly difficult, and I have done it many times.

You need a power amp, power resistor of the right value (usually high, like 50 to 100 ohms), a
signal generator and a scope. The method can be found online or in an old article in Audio Amateur/Speaker Builder magazine.

Essentially you measure the resonant frequency and the Q of the driver, impedance, and use a formula to derive
the T/S parameters. Algebra.

Even knowing the T/S parameters that does not give you the actual acoustic response
of the drivers. This is critical to know when creating a crossover, since the "ideal" crossover from a simulation
assumes "flat" drivers. Should the driver have a rising or falling response - especially at the xover frequency -
the resulting acoustic response will be substantially off.

Btw, mfrs frequency response curves tend to "lie sweetly". Especially since they are taken on IEC baffles (think
of a large piece of plywood - like a full sheet for LF drivers) the baffle face is MASSIVELY larger in dimension than
any usual speaker cabinet. This means that the real world response due to the relatively tiny speaker dimension
will have various nasty ups and downs that are not at all in the factory sweep. There are other issues to contend
with to get "flat-ish" acoustic response as well.

But, the simulation is a very good way to "get in the ballpark".

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« Reply #16 on: March 16, 2018, 03:46:59 PM »

It is indeed sometimes a problem when you don't have the T/S parameers of an unknown driver. I had also a few and did measure the T/S.
There are many drivers, also older ones, in the database of Visaton, that you can use to do the simulation. I think that they use the real acoustic response when simulate with their drivers. I did design a 2 way system especially for tube amps (constant impedance over the frequency range) and got very nice results compared to the simulation. I did measure using a borrowed microphone (I did not have one, but later compared with an Electret and got very simular results).
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WU2D
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« Reply #17 on: March 24, 2018, 07:51:36 AM »

I always did it with DC and watched which way the coil moves with a safe static voltage.
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w1vtp
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« Reply #18 on: March 25, 2018, 11:01:33 AM »

My method works. I've used it in various temporary PA installations over the decades and never had a problem.  Again, Just face the two speakers close and toward each other and use the polarity that gives the best bass performance.  Project done

Al
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