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Thread: DIY Speaker Polarity Switch Box, another easy project.

  1. #1
    Founding Member TREETOP's Avatar
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    DIY Speaker Polarity Switch Box, another easy project.

    This is something I made a while back when setting up a 3-way front stage with an outboard crossover network with 12db/octave slopes.

    I was toying with switching polarity on each speaker individually, and groups of speakers together, to get them to work together properly. The problem I was having, was during the "listen/power down/disconnect speaker/flip polarity/rewire speaker/power on/listen again" process, too much time had passed for me to make a direct comparison between before and after. Add the complication of doing this to more than one speaker at a time, and you can probably relate to my frustration.
    Brainstorming for a solution, I first started making a box with a bunch of banana plugs and wire jumpers between inputs and outputs. Needing 4 banana plugs per speaker channel, I ran out of parts and patience too quick and had to come up with something better. Plus I wanted something even easier to use.

    Here's what I came up with.

    I got 6 DPDT (double pole double throw) switches. I chose on/off/on switches rather than on/on, so that I could also turn each individual speaker off during testing if need be. They needed to be the latching variety rather than the momentary type. I used toggle switches, but slide switches or even Frankenstein style knife switches will work.

    Here is the type of switch I used:
    http://www.radioshack.com/product/in...ductId=2062537

    On each switch, I soldered the two input wires (positive and negative from the amplifier channel) to the two center terminals.
    I then soldered the two output wires (positive and negative to the speaker) to the two terminals on one end- with polarity the same as the input.
    I then soldered two jumper wires diagonally across the outer 4 terminals, one from each corner to the opposite corner on the other side.

    What this does is interrupts the speaker completely when the switch is in the off position, connects the speaker with polarity "correct" when the switch is thrown one direction, and connects the speaker with reverse polarity when the switch is thrown in the opposite direction.

    I drilled 6 holes in the lid of a project box, mounted the switches to the lid (adding some hot glue to prevent rotation), drilled 2 larger holes in the box body for input and output wires as groups, ran the wires through and assembled the box.

    With 6 switches to 6 speakers, and the wiring extended to the box, I could now flip polarities in real time from the driver's seat without even moving my head position.

    The beauty of this thing is that you can leave it installed as long as you want, until you're certain of how you want your polarities set. Then you can just remove it and wire each speaker back up according to the desired position on the switch box.

    Wiring:




    Top, completed:




    Size reference:


    Wired up (pardon the mess, I was rewiring the crossover RCAs at the time):


    Installed, tucked away but within easy reach:


    Diagram (sorry I don't do Photoshop or MSpaint, just drawings LOL):



    I've also made these for other applications, here's a smaller 2-channel one that I made. This came in handy when setting up my horn loaded compression drivers:



    Hopefully this can help someone who might have the same situation I was in.
    The only thing I'd recommend, is use smaller wire if you can. I used the Stinger sheathed 14ga that I've used in the rest of my setup and it was a little bit of a challenge to solder the terminals that have 2 wires attached. I used some bent nose needlenose pliers, that helped, but I could have simply used 16ga or even 18ga just for testing.
    Last edited by TREETOP; 09-06-2010 at 02:41 AM.

  2. #2
    Big Daddy Chad's Avatar
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    Foxy did this A LONG time ago..... and I made fun of him for it :p

  3. #3
    Founding Member TREETOP's Avatar
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    I remember, I posted pics in a related thread on another forum over a year ago and he posted one up too.

  4. #4
    Big Daddy Chad's Avatar
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    Once you get it right, there's no reason to have a switch in line, 180 degrees is a BIG switch, look for smaller increments.

    No reason to go at an over-easy egg with a chain saw.

  5. #5
    Founding Member TREETOP's Avatar
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    Quote Originally Posted by Chad View Post
    Once you get it right, there's no reason to have a switch in line, 180 degrees is a BIG switch, look for smaller increments.

    No reason to go at an over-easy egg with a chain saw.
    Quote Originally Posted by TREETOP View Post

    The beauty of this thing is that you can leave it installed as long as you want, until you're certain of how you want your polarities set. Then you can just remove it and wire each speaker back up according to the desired position on the switch box.
    180 degrees is about what's needed when using a 12db/octave slope, since phase is shifted by that amount at the crossover point. Often times it's advantageous to manipulate polarity electrically before messing with phase electronically.
    But yeah when I can find $3 switches that will shift phase by increments of less than 180 degrees, I'll rewrite this for you. ;)

  6. #6
    Big Daddy Chad's Avatar
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    Leave the console out an get it right in one hour or less. It's 180 degrees man. No need for switches unless you are bouncing it. One quick blow-thru with a simple RTA per side, or one good ear, will tell you what's up, and you know that.

    The foxy argument was strong.

    In other words, I feel that there is no reason to have to flip polarity, it's there or it's not, and that's the FIRST part of tuning, not an afterthought.
    Last edited by Chad; 09-06-2010 at 05:15 AM. Reason: spelling

  7. #7
    Devil's Advocate Adam_MSS's Avatar
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    I like it :headbang:

    You had a problem, devised a solution, and implemented it elegantly. I've not been as thorough as Chad during initial setup (I like to just get it to a point where it makes noise, then have the option to put my car back together) and have had to change polarity after the initial install/tune (polarity switch was in the processor) and even then I can see where this would be handy for just testing an idea quickly while troubleshooting.

    I've been really impressed with your execution on all of the things you've posted thus far.
    You don't use science to show that you're right, you use science to become right. - R.Munroe

    The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. - W.L.Bragg



  8. #8
    gyroscopes and infrared FoxForce's Avatar
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    Where did you get the little box? Or did you make it?

    I have less than preschool level soldering skills, so I terminated each connection with rings.

    Uncle Chad is right; he told me how and I obliged. I wasn't considering the "off" position but having it is worth 50% of the project alone. Having this in your system is just tits.

    Nice fit and finish, Cory. I ain't got the patience for that...nor did I have the room so the switches are crammed on either side of my e-brake in the center console.

  9. #9
    Tester Extraordinaire ErinH's Avatar
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    I agree with Chad on necessity. The only real area I can see an argument for it is in the top end. It's harder to tell there... goes back to ITD/ILD.

    However, this is a great little DIY and I appreciate you posting it up.

  10. #10
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    Just to jump on with Chad and his argument, we need to understand that the phase shift you experience at a crossover point is only electrical. When you put the damn thing in a car that phase shift will be considerably different, in either the positive or minus direction of the electrical shift.

    The phase shift is also dictated by distance. So, if the crossover is built on a flat baffle, where both drivers would be equidistant from the listener, then the phase shift mimics the electrical shift. Since this is almost never the case in a car, we need to focus on the acoustic shift.

    Neat little project, but in reality it's just picking if either 0, or 180 degrees of shift is closer to the actual acoustic shift. It has definite value, but would be even more valuable if further work was put into finding what the actual shift is. Like Chad said, think increments.

    When dealing with crossovers, never think in terms of electrical. That's black and white mathematics, and goes out the window when the less than perfect conditions of the real world are implemented. ALWAYS think in terms of acoustic.

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