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Old 1st July 2005, 06:56 AM   #1
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Default 4 ohms vs 8 ohms

I have a little problem.

Maybe someone might help?

I'd like to hook two Bose 101 Music Monitor to a Luxman R-405

that is working only on 8 ohms, with two outputs sets (A and B).

The Bose ask for 4 ohms drive.

What's the solution? Please help!!
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Old 2nd July 2005, 04:53 AM   #2
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your amp wont like it. perhaps run a 4ohm non inductive power resistor in series with load for 2 channels.

I would think you should be able to run 2 channels in parrallel with a .1ohm resistor in series before they connect together allowing you to use the full amp. I think that will work but am not positive. I assume the amp has a common ground for the - terminals.
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Old 4th July 2005, 09:42 PM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
I agree the amp will not like it.
Your info indicates that the Bose are 4ohm speakers and using A + B will give you 2 ohms when in parallel. However your amp my have a switch that offers A alone or B alone or A + B in series. If you can confirm this last option then the amp will be safe since you will be loading it with 8ohms which you said was it's rating. But speakers in series do not sound nice.
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Old 13th July 2005, 06:01 AM   #4
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Use a different amp, or run another 4 ohm speaker in series with your speaker.

IMO most amps should be made for 4 ohms, but most home amps are 8 ohms min

What I do for my setup: (My receiver is 100W/ch @ 8ohm)

My speakers are 2 boxed car speakers with two 8" woofers + tweeters, 4 ohm in each speaker.

I wire the two 4 ohm speakers in each box in series and in phase so I get an effective 8 ohm speaker for each channel.

That's the best way to do it without having to waste power in a resistor, or overload the amp. Just connect speakers in series.
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Old 14th July 2005, 08:43 PM   #5
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I wonder if the Lux is able to run two sets of speakers, each 8 ohms. If so it will be able to run one set at 4 ohms, provided the A/B switch parallels the speakers, unlike the Fisher SS units that series the units when both A and B are operated. You can check that rather easily with 4 speakers for a short time.

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Old 16th July 2005, 12:53 AM   #6
anatech is offline anatech  Canada
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Your 405 runs the A and B sets in parallel when they are both selected. You can run one set of speakers only. Two and the Lux will spite you by expiring. Nice sounding receiver but it has been prone to poor solder connections and a factory error with some units where the bias was set too darn high. A little TLC may be in order.

-Chris
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