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Multi-Way Conventional loudspeakers with crossovers

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Old 30th May 2002, 08:45 AM   #1
Vivek is offline Vivek  India
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Default Speaker thump

Hi all,
I just completed a pair of bookshelf speakers. The crossover for the woofer is a first order Butterworth and second order Butterworth for the tweeter.
Now when I switch on the amp, the woofer cones move back. Normally, I have seen the cone move forward in other systems. Is this a problem?
Since the order of the crossovers is not the same, should the tweeter be connected in or out of phase with the woofer?
Thanks for any help.
Regards,
Vivek.
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Old 30th May 2002, 10:21 AM   #2
TG is offline TG  Ukraine
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Hello Vivek,

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Now when I switch on the amp, the woofer cones move back. Normally, I have seen the cone move forward in other systems. Is this a problem?
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May be. Depends on your amplifier. The simplest way to check it is to connect 1.5 V battery directly to your speaker inputs: plus to positive (red) input and minus to negative (black). If woofer cone moves forward, than all's OK. If not, re-phase your woofer.

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Since the order of the crossovers is not the same, should the tweeter be connected in or out of phase with the woofer?
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It depends not only on order of the crossovers but also on cutoff frequencies of each of them and on placement of woofer and tweeter. I usually drive speakers with sweep tone, record it from microphone and look when it less distorts the form of oreiginal signal.

Good luck!
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Old 30th May 2002, 01:31 PM   #3
Vivek is offline Vivek  India
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Hi TG,
The woofer has + and -- marked and I have soldered and connected the wires accordingly. I do not understand why this is happening.
If the cone of the woofer moves back, do you think I should check the tweeters as well?
Regards,
Vivek.
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Old 30th May 2002, 01:46 PM   #4
TG is offline TG  Ukraine
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-------
The woofer has + and -- marked and I have soldered and connected the wires accordingly. I do not understand why this is happening.
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This might be because of some manufacturer's mistake. It happens... It's always recommended to check this before installing drivers...

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If the cone of the woofer moves back, do you think I should check the tweeters as well?
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Yes, I think so. But it will be hard to do this without special equipment since movements of tweeter's dome (or cone) are almost invisible (very small magnitude). Check the woofers with battery and then connect tweeters the way it sounds best to you.

Good luck!
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Old 30th May 2002, 03:37 PM   #5
UrSv is offline UrSv  Sweden
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I would say that it could perfectly normal. When you switch on your amp the supply rails and circuits parts "come up" with diffenent speeds. If your negative half (of your amp, not you) comes up earlier than the positive you might get a negative voltage on the output, cone moves in, or if the other way round you get a positive voltage out, cone moves out. That's the way it is and if you are worried about it I would probably check for absolute phase system wide instead i.e. send a positive pulse into your input and check the cone for outwards motion then find where it went wrong if not the same phase...

Tip: Elektor had a project for absolute phase measurements a couple of years ago where there was a sender that could send pos or neg pulses and then there was a receiver with a microphone that would indicate what phase came out.

/UrSv
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Old 31st May 2002, 09:16 AM   #6
Vivek is offline Vivek  India
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Thanks to you guys.
Regards,
Vivek
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