JL Audio Fathom

@rauliruegas you keep saying the same thing over and over without explaining what you mean.  There is also no 1.1ohm impedance in the curve for the Sabrina that I have seen.  Sorry, I'm hijacking this thread and I don't want to do that.  I understand the autoformer matches the load that's how it is able to consistently deliver the same wattage regardless of load.

The autoformer more or less multiplies the impedance of the speaker making it an easier load.

the minimum impedance of the Sabrina according to Stereophile is 2.44 ohms and the Sabrina X is stated by them at 1.1. Mcintosh states to use the tap below the lowest impedance of the speaker. In this case try the 2 ohm. With that being said you can use any tap you want, it will not hurt the amp.

When you use the lower tap it will reduce the output voltage which will increase the current (current being good for low impedance speakers). It will generate more heat but Macs run so cool it will not matter.

However lower than needed will not improve it more. If you had a true 8 ohm speaker using the 4 ohm for example has no advantage over the 8 ohm as you just give up voltage as the “extra” current will not be pulled.

The down side of the autoformer is cost, size and weight. The other one is running the signal through a big chunk of copper but not sure it matters too much.

what I think you will hear when using the lower tap is a reduction in the highs and an overall smother sound. Try it and let us know what you think.

Dear @james633  : All speakers ask for current not voltage.

Before I posted in this thread I analize the Sabrina and Mac and from this " bad " realationship " I gave my advise to the owner to change the subs for ones that uses low and high pass filters crossing at around 100hz and with that the Mac will be running alot better in the 4 ohm tap and the subs will handled from there and down to 16hz and with all those the owner system will be improved in its overall quality level performance.

He says that is satisfied with the ML subs what seems to me that he has a misunderstood in the whole subject.

R.

Yes the correct answers is a high pass which will fix “everything” and take the system to another level. On the 8950 you can pull the bars out of the back that separate the pre-amp and amp to rout wires to the crossover then back into the amp portion. 
 

JL Audio CR-1 $3500 (analogue)

Sublime Acoustics K231 $600 (analogue, probably as good as the JL, new model has balanced inputs) 

Harrison Labs inline highpass  $27 ( single capacitor installed between the preamp and amp). This will be a 12db slope on the Mac’s input impedance.

Hi @james633  : " Harrison Labs inline highpass  $27 ( single capacitor installed between the preamp and amp) " 

It seems to me the best alternative/option for @upstateaudiophile  As a fact I'm doing something similar directly in my ML 20.6 monobloks that are coupled ( by design ) at the input and it's here where I changed the input cap for a lower and better quality cap that makes the high pass at around 87hz.

Your very good advice.

R.