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Old 14th February 2005, 04:32 PM   #1
Urloony is offline Urloony  United States
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Default How to change impedance with two 8 ohm speakers?

I have two 8 ohm 6-1/2 in. woofers I'd like to use in a center channel design. The problem is keeping the impedance of the speaker at 8 ohms. Is there a way to modify the crossover in order to keep the total impedance of the speaker at 8 ohms instead of 4 or 16? I'm planning a WTW center channel with a 4 ohm tweeter. I've considered just using two 4 ohm woofers instead but was hoping to use the ones I have at least for now.
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Old 14th February 2005, 04:55 PM   #2
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One xo for each driver should do it.
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Old 14th February 2005, 05:54 PM   #3
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Why do you need to keep the impedance at 8ohms?

And, one crossover per woofer is not going to help.
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Old 14th February 2005, 06:01 PM   #4
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The only way to do that is to have a 4 ohm dummy load in series with the woofers in parallel. Your best bet is to make it a 4 ohm speaker or get two 4 ohm drivers instead.
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Old 14th February 2005, 10:45 PM   #5
Urloony is offline Urloony  United States
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The rest of the speakers in the system are all 8 ohms. The amp is also set 8 ohms and I'm trying to be safe and not trip the breaker in the amp. How would I set up a dummy load for each speaker? I've thought about just adding an 8 ohm resister on each driver but thought this may only effect DC resistance and not impedance. Is this the way to go or is there something else you guys have in mind?
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Old 15th February 2005, 12:04 AM   #6
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I wouldn't really recommend attaching a dummy load, as you're just making your speakers less efficient and wasting energy. Think of it this way: you're running 10 total watts to your speaker, the actual drivers are only getting 5 watts each and the resister has to dissipate 5 watts.

If you want an 8 ohm total MTM you really want to start with 4 ohm woofers.

You can get some nice dayton 6.5" shielded 4 ohm speakers for only about $20 each.

I'd save your 8 ohm woofers for a TM project some day and get the parts your really need for an 8 ohm speaker.
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Old 15th February 2005, 01:41 AM   #7
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Aha! I've got it. Just use one of the woofers. Problem solved.
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Old 15th February 2005, 02:30 AM   #8
Stocker is offline Stocker  United States
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If the amplifier has a circuit breaker, and you are not afraid of opening the amp to reset it as required, try it one time. Wire the speakers up with some chumpy capacitor for the tweeter to protect it and wire it all together. No box or anything required. Crank it. loud. Louder. When your ears hurt, and the breaker hasn't tripped, you know you don't have a problem.

If the breaker trips, come back and ask again.
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Old 17th February 2005, 03:22 PM   #9
Urloony is offline Urloony  United States
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thanks for the replies guys, I just got brave and wired it all up and it works fine. I guess the amp doesn't have a problem running speakers of varrying imedance.
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