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Quick amp question...harmon kardon using magnaplaners and std spkrs

 

alan cagle
Posted on   
Got a HK6250 that has switch for 4 ohm or 8 ohm.
Just got in magnaplaners...taking 4 ohm...but still wish to use additional existing 8 ohm.

Switch is either /or. So flipped to 4 ohm and all fine with magnaplaners. worried about tying in the 8 ohmers.

Listed above outputs is the below:

4 ohm mode:

1 or 2 : 4 ohm min.
1 & 2 : 8 ohm min.

right left
Have System 1 speaker outputs pos/neg neg/pos
right left
System 2 speaker outputs pos/neg neg/pos

What is the 1 or 2 , 1 & 2 mean ?
How do I correctly attach, and where, the 8 ohm spkrs ?

Appreciate any help from my tech friends !
 

Ellwood Davis
Posted on   
Speaker impedence works like this:

1 or 2 speakers means that the minimum impedence in ohms the receiver will see is 4 ohms, which is the lowest it can handle.

If you want to use two sets of speakers simultaneously, you have to calculate the total impedence like this.

1/Total = 1/speaker1 + 1/speaker2
1/Total = 1/8 + 1/8
1/Total = 1/4
1/Total = 4 ohms

Since P=I*I*Z, then I = SQRT(P/Z), so what they're saying is that the most current (I) the amp can deliver (since that's what you're really buying) is limited to a total minimum impedence of 4 ohms.

Here's what happens if you're using one 8 ohms and one 4 ohm speaker:

1/Total = 1/8 + 1/4
1/Total = 3/8
1/Total = 2.66 ohms

The result is a demand of 23% more current that the amp can provide. This is the kind of scenario where something called clipping occurs, and speakers can be damaged.

1/Total = 1/4 + 1/4
1/Total = 1/2
1/Total = 2 ohms

The result is a demand of 41% more current that the amp can provide. This is the kind of scenario where something called clipping occurs, and speakers can be damaged, and at this rate...a fried amp too.

I've owned Magnapan speaker before, and you really don't want to add another set of speaker with it. They are already taxing your Harmon Kardon enough.

Hope this helps.
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