Which amplifier tap... 4 ohm or 8 ohm

Randy Myers

Randy Myers

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I have a new pair of Harbeth arriving today. My McIntosh amplifier has 2, 4, and 8 ohm speaker connections. The Harbeth are 6 ohm. Which tap should I use 4 or 8? I know the normal answer is to try both and see which I like better. I have always used the 8 ohm connection on this amp, but I am asking opinions. Would the 4 or 8 connector be better, and why would you think so.

Thank you
 
I'm not familiar with your amp but I thought many of the Mac amps used autoformers where the speaker impedance wouldn't matter.

I've always heard the Harbeth are easy to drive although inefficient. My thought would be to use the 4 ohm tap which would be designed to handle lower impedances than your other taps. 4 ohm should just produce a bit more current which I feel is a good thing.

I once had a CJ power amp with the option of 4 or 8 ohm taps, I also had 6 ohm speakers, I was told by CJ to use the 4 ohm tap.
 
Mr Peabody said:
I'm not familiar with your amp but I thought many of the Mac amps used autoformers where the speaker impedance wouldn't matter.

I've always heard the Harbeth are easy to drive although inefficient. My thought would be to use the 4 ohm tap which would be designed to handle lower impedances than your other taps. 4 ohm should just produce a bit more current which I feel is a good thing.

I once had a CJ power amp with the option of 4 or 8 ohm taps, I also had 6 ohm speakers, I was told by CJ to use the 4 ohm tap.
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Thank you sir. The McIntosh does have autoformers, but also has 2, 4, and 8 ohm terminals. I will try the 4 ohm :)...
 
I talked to McIntosh and he basically said that either would not be an issue. He did suggest, as you did, to try both. He also said to see if I could find a review where they ran impedance tests on the speakers. I did and here are the results.
1746722479820.png
I would tend to think that the speaker never drops down to the 4 ohm range, and when they state that the speakers are easy to drive this is probably what they are referring to. I would also conclude that the 8 ohm connection is probably the best to use to start with. I also see what McIntosh is saying; that either would probably work just fine.

Agree?
 
I usually listen to each tap for awhile before I decide. The higher impedance tap will be louder so you have to adjust the volume to compensate for that. Looks like either the 4 or 8 ohm tap will work just fine.

To me that looks like an 8 ohm speaker with just a small dip below that.
 
So far playing using the 8 ohm and they are working great. I agree, it definitely look more like a 8 ohm speaker. Harbeth rates them at 6 ohm, but they might be a little closer to 8 than 6.
 
Randy, why don’t you contact the speaker manufacturer? I would think that they should have the best answer for you.
 
It’s my understanding that speakers have a “nominal” impedance rating. The resistance can vary significantly with frequency. For full understanding, one must look at the impedance/frequency graph. Some speakers dip towards 2 ohm at a certain frequency. Amplifiers differ in their ability to handle the low resistance.
 
Bones13 said:
It’s my understanding that speakers have a “nominal” impedance rating. The resistance can vary significantly with frequency. For full understanding, one must look at the impedance/frequency graph. Some speakers dip towards 2 ohm at a certain frequency. Amplifiers differ in their ability to handle the low resistance.
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Exactly. Impedance rating is an average. The impedance, or the resistance a speaker gives to an amplifier is dependent on frequency.

The suggestion that McIntosh gave me was to see if any impedance graphs have been done, which they have. I posted it above. The graph shows that the Harbeth C7 never dip close to 5 ohm, let alone 4. When I look at the entire graph I see that many times it hovers just above 6 ohm, but over all usually higher.

This leads me to the conclusion that the 4 ohm tap would be too low and therefore 8 ohm is the best choice. According to McIntosh, as expected, neither one would cause the amplifier to have an issue, and therefore both would work just fine.

Thank you to everybody for your input!
 
Porsche said:
you want to use 4ohm, It will control the drivers better with more power
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Please explain a bit further if you would. I am asking opinions and wanting to learn a bit more. I thought with the speakers never approaching 4 ohm, in any frequency, that the 4 ohm tap may not be the best. I am definitely open to learning. Thank you for your input.

I do not believe it is a factor here, but I do not listen at high volume levels and never drive the amplifier into even feeling warm to the touch. The McIntosh amplifier is rated at 150 WPC; but as we know that standard is non-existent at this point in time. Again, it means nothing, but the McIntosh amplifier is at the high point of recommended power by Harbeth.
 
I’m not sure there is a “right or wrong” answer here. Every time this question comes up, unless for rare cases, the answer is to listen to both taps, and pick the one that sounds best to you. Different people have differing sound preferences. Just like other audiophile pursuits, like cables. Most cables are “correct” for the purpose, but people make their choice on other factors, one being the sound in the system.
 
Bones13 said:
I’m not sure there is a “right or wrong” answer here. Every time this question comes up, unless for rare cases, the answer is to listen to both taps, and pick the one that sounds best to you. Different people have differing sound preferences. Just like other audiophile pursuits, like cables. Most cables are “correct” for the purpose, but people make their choice on other factors, one being the sound in the system.
Click to expand...
Thanks you for replying. I will try the 4 ohm also!
 
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