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  #21  
Old 03-13-2018, 02:41 PM
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Quote:
Originally Posted by crwilli View Post
Eric,

While I can’t find it right now, there is a picture of a slide from a McIntosh engineer that shows the impact on sound from moving to the 2,4 or 8 ohm taps. If I remember, generally, less highs at the lower taps up to 3 dB and more bass at a higher tap...
I can't dispute that possibility since I'm not familiar with that particular study/experiment but I would find that extremely surprising since I've never read, heard or seen anything from official factory sources suggesting this to be the case.

If indeed that is true, this would of course have serious performance implications given the reactive nature of loads inherent in most loudspeakers.

Perhaps an excuse for another tour!
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  #22  
Old 03-13-2018, 05:16 PM
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Don’t need an excuse for another tour!
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  #23  
Old 03-17-2018, 09:00 AM
Charles Charles is offline
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There is no question that miss matching the impedance will alter the bass. That's why it is important to use the nominal impedance supplied by the manufacturer as a guide. For example if it is 5-8 ohms use the 8 ohm tap. If it is 2-4 ohms use the 4 ohm tap. This is for modern day Mac amps. Older Mac amps were much more current strapped. Modern day Mac amps have plenty of current if you follow my suggestions. Then it is a matter of efficiency. The more inefficient the speaker the more watts you will need to get the best most relaxed sound. I can't speak to tube amps as I haven't owned a Mac tube power amp in many years.

Also, in my opinion Mac has taken a very intelligent approach to the relationships among current, impedance, and watts. The brute force approach would be a D'Agostino approach. His amps have tremendous current capacity at any impedance but produce less watts the higher the impedance. For example one of his rated at 300 watts at 8 ohms will generally produce 1,200 watts a 2 ohms. But at 8 ohms it will produce 300 watts and a little more (dynamic headroom) before it clips.

What this means is an amp with a mega power supply capable of producing many hundreds even thousands of watts at low impedances. A modern day Mac amp like a 601 or 1.2KW has plenty of current if you don't miss match the impedance. It is impossible to miss match the impedance with an D'Agostino amp.

Mac amps should run very cool even when stressed. If your amp is hot you may have an impedance miss match which I think inadvisable.

Last edited by Charles; 03-17-2018 at 11:22 AM.
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  #24  
Old 03-17-2018, 12:58 PM
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Speaker impedance is not fixed, therefore it is impossible for the impedance to be exactly matched to any single amplifier tap.

The idea is to match impedance the amplifier is most likely to see with a given speaker the majority of the time for a given speaker. This can even vary according to the program material. For example many 8 ohm "nominal" speakers can dip to as little as 4 ohms in the 50 - 60 Hz range. The impedance seen with such a speaker is going to be very different when playing a string quartet as opposed to organ music.

Last edited by 62caddy; 03-17-2018 at 02:47 PM.
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  #25  
Old 03-18-2018, 05:13 PM
Timobi Timobi is offline
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After about a week of experimenting with both the 4ohm and 8ohm taps I find myself liking the 8ohm better with my Martin Logan CLX electrostatics and MC601.

The first month I used the 4ohm exclusively thinking these speakers would be better served that way.

No.

There's just more air with the 8ohm. Bass was just as good so no issue there. Today I switched back and forth and 'missed' the open ness that the 8ohm brought.

So there you have it.
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  #26  
Old 03-18-2018, 05:17 PM
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Quote:
Originally Posted by Timobi View Post
After about a week of experimenting with both the 4ohm and 8ohm taps I find myself liking the 8ohm better with my Martin Logan CLX electrostatics and MC601.

The first month I used the 4ohm exclusively thinking these speakers would be better served that way.

No.

There's just more air with the 8ohm. Bass was just as good so no issue there. Today I switched back and forth and 'missed' the open ness that the 8ohm brought.

So there you have it.
What is the nominal for your speakers?
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  #27  
Old 03-18-2018, 05:20 PM
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From the ML site...

Quote:
Impedance
6 Ohms, 0.7 at 20kHz Compatible with 4, 6, or 8 Ohm rated amplifiers.
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  #28  
Old 03-18-2018, 06:12 PM
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Forget the numbers. It sounds better at one setting than another. It’s the right setting!
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  #29  
Old 03-18-2018, 08:26 PM
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I changed to 4 ohms and the sound went from mediocre to fantastic!
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  #30  
Old 03-18-2018, 08:33 PM
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And that’s why it takes a village!
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