JL Audio Fathom

Just use the 2 ohm tap. the autoformers are use to match the load to the amp so it does not need to work as hard. Using the 2 ohm tap should make the highs sound a touch softer, effectively making the bass louder.

if you want a deep dive into how a Mac work the stereophile review of the MC462 is a good read… it also has near perfect measurements.

Dear @jastralfu  : Look, Mac works with autoformer from 1967 but that just not says they are perfectly rigth about because it's not. Any additional device in an ampp design ( as the autoformer ) only degrades the MUSIC signal no matter what.

No, that Mac is not really ready to handled with aplomb that 1.1 ohm speaker impedance.

Those are facts that I can see or you don't understand very well or you have a misunderstood about.

@james633  is rigth: " autoformers are use to match the load to the amp " but not for that to low 1.1 ohm impedance in a critical and very often present in MUSIC as 90hz and wha surround that 90hz.

That's the issue.

R.

@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.