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Old 25th August 2009, 09:45 PM   #1
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Question How to know which speaker is inverted?

After investing a lot of time and money building some fantastic line array speakers, I spent a lof of time listening to them, and they sounded really funny... after a while, I realized that one of them is wired backwards. (+ and - are reversed.) It's easy to fix, but how do I determine which of the two speakers is backwards? They are full-range, designed to play from 180hz up, so I dare not use the 9-volt battery trick.

Thanks in advance!

Your old friend (and too long not-heard-from),

Nappylady
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Old 25th August 2009, 10:33 PM   #2
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When you say 'one of them is wired backwards' what do you mean?

One of the speakers in the array, or one of the speaker cabinets?

I'm confused by the question, you say you built these speakers but don't know how to determine the phase connection of the speakers. How were you able to wire them at all without knowing this?

Also you specifically mention (+) and (-), ...er... how can you have (+) and (-) without knowing which is (+) and which is (-)? Again, it is a confusing question.

Likely the speaker terminals on the individual drivers is marked. We just assume the marked terminal is the positive terminal.

However, since the speaker's input swing plus and minus, it doesn't matter that much whether the marked terminal is plus or minus as long as you make a decision and stick to that configuration through out all your wiring.

I think if you want a usable answer, you need to clear up the question.

Also, how about we accept the convention where when we mean the entire speakers system or entire speaker cabinet, we call it a speaker.

But when we want to refer to one specific speaker, we call it a driver, that why we can have a consistent understanding of what is being said.

So, it is one speaker or one driver that is wired backwards, and if you know (+) and (-), how can you not know which of the two is backwards?

I think there are a few details you left out.

Not trying to be snarky, just trying to get the question clear and focused.

Steve/bluewizard
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Old 25th August 2009, 11:01 PM   #3
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I never use a 9v battery, always a 1.5v AA cell. That would be fine for you as well.
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Old 25th August 2009, 11:05 PM   #4
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Quote:
Originally Posted by Nappylady View Post
After investing a lot of time and money building some fantastic line array speakers, I spent a lof of time listening to them, and they sounded really funny... after a while, I realized that one of them is wired backwards. (+ and - are reversed.) It's easy to fix, but how do I determine which of the two speakers is backwards? They are full-range, designed to play from 180hz up, so I dare not use the 9-volt battery trick.

Thanks in advance!

Your old friend (and too long not-heard-from),

Nappylady
You can test with a 1.5 volt battery and a couple of crocodile clips leads.
The cones should move the same way with the same polarity from the battery.
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Old 26th August 2009, 02:24 AM   #5
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1 Pick a sine tone and play through each driver individually and measure the dB. I usually pick the crossover point.
2 Play the same sine tone through a pair of the drivers and measure dB. Higher dB will occur when they are in-phase (correct polarity connection) and vice versa.
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Old 27th August 2009, 11:20 AM   #6
Dr_EM is offline Dr_EM  United Kingdom
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Quote:
Originally Posted by richie00boy View Post
I never use a 9v battery, always a 1.5v AA cell. That would be fine for you as well.
Yes, this is also what I use. I've done it on dome midranges too and it does no harm
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Old 27th August 2009, 11:58 AM   #7
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I'll third the 1.5V battery, my general rule is that the +ve terminal on the speakers is the one that results in the cones moving out when you connect it to the positive on the battery

from another person who the forums hasn't heard from for a long time until very recently (about four years for me!)

Tony.
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Old 27th August 2009, 09:36 PM   #8
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Quote:
Originally Posted by wintermute View Post
I'll third the 1.5V battery, my general rule is that the +ve terminal on the speakers is the one that results in the cones moving out when you connect it to the positive on the battery
The exception would be in a system with driver polarity intentionally inverted, as with a 2nd order cross-over.

1.5V battery works fine, even for dome tweeters.
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Old 28th August 2009, 12:17 AM   #9
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The +/- terminals on drivers are not always correct. 1.5V battery is a good way to check.

I once met an abnormal case, a pair of big speakers with 2 woofers per side but came out poor bass. (big name, big brand!) Checked everything and finally found the woofers on one side of the speakers were out of phase, so they largely cancelled out.

Re-wired that driver then everything was brought back and played nicely. Funny that big name speakers came with the signature of the factory assembler -- so called "hi-end" stuff, ha!
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