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Old 22nd October 2007, 01:08 AM   #1
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Default 4-ohm Speakers on 6-ohm Amp? (newbie question)

What would be the result of connecting 4-ohm DIY speakers to my Onkyo amplifier which specifies a 6-ohm minimum speaker impedance?

I know it's something you're not *supposed* to do, but what's the real deal? I'm no serious audiophile, and I don't listen loud. Just looking ahead at my next couple of projects and evaluating options.

Thanks much,

Cam
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Old 22nd October 2007, 01:14 AM   #2
Ron E is offline Ron E  United States
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Asking an amp to deliver a significant fraction of its rated power into a lower impedance than it is rated for will likely cause early failure. If you don't listen loudly and your speakers are of reasonable sensitivity, you will not have problems.

Your mileage may vary....
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Old 22nd October 2007, 02:00 AM   #3
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Hi Ron and Cam,

I've oft wondered that myself. Ron, would you venture a guess as to what you might be able to run? I know we shouldn't at all but could you pull an honest 5 watts from a 50 watt amp without future concerns?

EDIT: Mostly I am thinking of an 8 ohm channel with a 4 ohm speaker.
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Old 22nd October 2007, 02:17 AM   #4
BWRX is offline BWRX  United States
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If you really want to find out open up that Onkyo amp so you can measure the supply rail voltages and see what output devices are used. Look up the datasheet for the devices and determine if they can source/sink current that will be drawn by a lower impedance load while being operated at the amplifier's supply voltage.

If you don't want to do all that I would wager that the Onkyo amp will be ok driving a lower impedance load as long as you don't push it. If you find yourself turing up the volume and it starts sounding worse then the amp just wasn't designed to be worked that hard.
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Old 22nd October 2007, 02:39 AM   #5
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I'm sorry but I don't agree at all with allowing a receiver that was designed to run a 6 ohm load running a 4 ohm load. The engineers that designed it came up with the minimum load specification and that should be followed to the letter.

Prior logic and reasoning is like saying that its ok to play with fire as long as the fire is small because you might only get burned a little. Well, you play with any fire and you will get burned. You overload any amplifier that is NOT designed for it and it will sooner or later let out the magic smoke.

I suggest that if the amplifier is NOT designed to run the load you take it to the local flee market and promptly sell it and purchase one that will.
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Old 22nd October 2007, 03:45 AM   #6
BWRX is offline BWRX  United States
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Consider that loudspeakers do not present a flat impedance vs frequency and that some speakers will actually have a much lower impedance than nominal at certain frequencies and the nominal load specs are more like guidelines than set in stone rules.

Quote:
You overload any amplifier that is NOT designed for it and it will sooner or later let out the magic smoke.
That is basically what I was saying. You can safely use lower impedance loads as long as you don't overload the amplifier. Distortion will increase rapidly as the amp becomes overloaded, so trust your ears and turn it down if you start hearing a lot of distortion. Simple as that.
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Old 22nd October 2007, 10:26 AM   #7
sreten is online now sreten  United Kingdom
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Hi,

Amplifiers rated as 8 or 6 ohm loads generally have aggressive
protection to stop them thermally overheating. They will struggle
with 8 ohm reactive loads just as much as 4 ohm resistive loads.

Generally speaking the protection works and if you use 4 ohm
speakers with 8 ohm amplifiers you do not get any more power,
in some cases less, depending on the protection.

Its not a good idea if your a party animal, but generally it is OK.

/sreten.
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Old 22nd October 2007, 10:31 AM   #8
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Quote:
You can safely use lower impedance loads as long as you don't overload the amplifier
No, No, No!!!!

When you use a lower impedance load you are overloading the amplifier.

The amplifier was rated for a load not to be less than 6 ohms period.

Where does it state you can use a 4 ohm load?

It surely also doesn't state that if you don't push it a 4 ohm load is ok.

The only instance where you can get away with this is with a tube amplifier.
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Old 22nd October 2007, 11:14 AM   #9
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They have to say that to cover themselves and the average consumer who knows absolutely nothing.

The issue is simply the current draw, so if you listen pretty quiet at all times there is no reason not to go with the lower load than the label says.
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Old 22nd October 2007, 11:24 AM   #10
sreten is online now sreten  United Kingdom
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Quote:
Originally posted by burnedfingers

No, No, No!!!!
When you use a lower impedance load you are overloading the amplifier.
The amplifier was rated for a load not to be less than 6 ohms period.
Where does it state you can use a 4 ohm load?
It surely also doesn't state that if you don't push it a 4 ohm load is ok.
The only instance where you can get away with this is with a tube amplifier.

Hi,

You stick to your "understanding" and I will stick to mine.
You take the numbers rather than reality too seriously.

/sreten.
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