Amp for 4 Ohm Speakers

[zumbo]

On the 16ohm posts, the power would be above 400WPC.

 

[PENG]

Actually, it's not. Depending on the difficulty of the load the speaker presents, you have the ability to connect the speaker to whatever posts you choose. It's your option, and a very cool option to have.

Just like the Linear Power 4ohm/2ohm internal taps, the McIntosh amps are more than capable of allowing a low ohm load connection to the 8ohm posts.

This time I have to disagree and would side with TLSG (I seldom do), to a point anyway.

Quote from the manual:

"The only adverse effect on the operation of a
Mclntosh amplifier when it is improperly matched
is a reduction in the amount of distortion-free
power available to the loudspeaker. Close impedance
matching is desirable for maximum distortion-
free power."

They use this "autoformer" thing, that's the different. You can read up on the "maximum power transfer theorem" if you wish. Note that this amp has very low damping factors too.

 

[AcuDefTechGuy]

Actually, on the 8ohm posts, it would be 210@4ohm. Or better.

On the 16ohm posts, the power would be above 400WPC.

So then why do they rate it as 105Watts into 4ohms/8ohms/16ohms, which was my original question?

Why wouldn't they rated it as 400 Watts into 4 ohms in the first place?

 

[zumbo]

This time I have to disagree and would side with TLSG (I seldom do), to a point anyway.

Quote from the manual:

"The only adverse effect on the operation of a
Mclntosh amplifier when it is improperly matched
is a reduction in the amount of distortion-free
power available to the loudspeaker. Close impedance
matching is desirable for maximum distortion-
free power."

They use this "autoformer" thing, that's the different. You can read up on the "maximum power transfer theorem" if you wish. Note that this amp has very low damping factors too.

Any time you reduce the ohm load, an amp intern becomes more distorted.

Any amp.

Shocked you posted such a reply.

McIntosh is giving you the ability to connect a low ohm speaker without adding stress, distortion, or any other negative reaction an amp may have to such a load.

 

[zumbo]

So then why do they rate it as 105Watts into 4ohms/8ohms/16ohms, which was my original question?

Why wouldn't they rated it as 400 Watts into 4 ohms in the first place?

And my original answer.

You(the customer) get the power you pay for, with the capability to power any speaker.

And I guess I should add, while maintaining optimal distortion specs.

It's all fairly simple stuff.

I guess the way they see it is that if you(the customer) are paying the price to own the best, then the whole dropping the resistance to produce more power would not be your(the customers) desire.

You(the customer) want a 400W McIntosh, then buy a 400W McIntosh.

Their amps are amps, and they react to a reduction in resistance just as any other amp. They just give you the option to connect a less resistive speaker to a separate post to remain within the given specs.

 

[TLS Guy]

Actually, on the 8ohm posts, it would be 210@4ohm. Or better.



I am the proud owner of two POA 2200 amps. Denon POA are the best amps for the money, by far.

No it is not. That is the whole problem with it. You will not get increased output into four ohms on the 8 ohm tap. Actually you will get 50 watts. Just like you would with a tube amp, tapped to the wrong setting.

One of the benefits of solid state amps is doing away with the output transformer.

You have to match the impedance closely. The dealer set my friend's B & W 800 Ds up on the 8 ohm setting, because B & W state they are 8 ohm nominal. However they go below four ohms in the bass.

On his 400 watt per channel amp they sounded terrible on the 8 ohm setting. I out it on four ohm and things were much better. Mac confirmed the speakers needed to be on the four ohm setting.

In difficult load speakers, especially those with wide impedance swings the last thing you need is an output transformer.

The nice thing about a well designed direct coupled solid state amp, is that it will deliver the power where it is needed.

Having had experience with one of these MAC power amps with auto transformers, I can not recommend them. In fact I would steer people well away from them.

I know why they did it and its called liability. With the transformer, there is no possibility of DC off set what ever. Mac owners tend to have very expensive speakers, and they did not want any possibility of having to buy an owner a new set of speakers.

However the trade offs in my view are far too severe.

 

[TLS Guy]

On the 16ohm posts, the power would be above 400WPC.

It would be 25 watts.

 

[zumbo]

It would be 25 watts.

RRRrrrrrright. It simply doesn't work that way.

Like I said, a McIntosh customer is going to buy the desired power amp for the chosen speaker. Their wallets are a whole lot thicker than mine.

I don't have the coin to own the correct McIntosh for my particular needs, but that is not going to cause me to try to find reasons to knock them.

OTOH, I recommended Denon POA 6600. Period.

 

[zumbo]

For what it's worth, I have been waaaaaaay down the cheater amp road. It simply doesn't work.

Buying an amp because it gives a low ohm spec that seems to fit a speaker is not the best option.

The best option is always to buy the best amp you(the customer) can afford, regardless of the speakers specs. Unless you have some really crappy speakers.

In my current budget, and experience, I am having great luck with the old-school Denon POA amps.

 

[TLS Guy]

RRRrrrrrright. It simply doesn't work that way.

Like I said, a McIntosh customer is going to buy the desired power amp for the chosen speaker. Their wallets are a whole lot thicker than mine.

I don't have the coin to own the correct McIntosh for my particular needs, but that is not going to cause me to try to find reasons to knock them.

OTOH, I recommended Denon POA 6600. Period.

It does work that way, because as you up the tap to 16 ohm, voltage is increased but current output is limited. All transformers work that way.

So as you up the tap in impedance you limit the current available. I confirmed it up close.

So if you use one of those amps, ideally you need a speaker with a very flat impedance curve and that is few.

Fortunately for Mac the impedance drop is usually in the bass. So you must set the tap for the impedance where most of the power is. Fortunately power demands tend to fall in the area of impedance rise. If not the results would be really bad.

As impedance rises if the amp has to be set to four ohm, voltage and therefore power at those frequencies is limited. However as stated they get away with it, because power demands are limited in the region were these amps become voltage limited. However this is not all speakers.

I will state the bottom line. For the vast majority of speakers a direct coupled amp with high current capability will do the best job and not one with a transformer interposed between the speaker and the output devices.

 

[3db]

I too side with TLS on this Zumbo. Transformers have to obey the law's of electrical theorey. If you up the voltage output on teh secondary by inceasing teh windings, then the current capability has to drop and visa versa. A transformer's equation looks like this:

Vprimary x Iprimary = Vsecondary x Isecondary x effeciency rating

Your advice however on getting a solid amp to drive a difficult load is sound...excuse the pun

 

[cpp]

good reading

see 2.2.5 Speaker Distribution or “Constant Voltage”

http://www.jensen-transformers.com/an/Audio Transformers Chapter.pdf

&

http://www.radioremembered.org/outimp.htm

 

[zumbo]

Sent email to McIntosh. I will be disappointed if the outcome is not in my favor.

I always assumed the amps performed in the same manner as the Linear Power amps. You can see the movable taps in the middle of the amp. If they were left on the 4ohm tap while connected to a 2ohm load, the amp would attempt to double down.

There were debates on the actual power, but as you all know, that depends on the speaker/s connected.

 

[zumbo]

Eat crow! As you move up, the power doubles.

My reply from McIntosh:

4 ohm speakers on the 8 ohm connection gets 210 watts, but generates more heat than the amp can dissipate and is bad for it.



4 ohm speakers on the 4 ohm connection gets 105 watts and is the correct connection



4 ohm speakers on the 2 ohm connection gets 52.5 watts

 

[zumbo]

I honestly can't believe I had to send that email.

 

[AcuDefTechGuy]

4 ohm speakers on the 8 ohm connection gets 210 watts, but generates more heat than the amp can dissipate and is bad for it.

4 ohm speakers on the 4 ohm connection gets 105 watts and is the correct connection

So the bottom line: it is a 105 WPC amp.

 

[zumbo]

So the bottom line: it is a 105 WPC amp.

Just as any other 105WPC amp. However, it does double down. That puts it in the top tier amp category.

While it may be called "Auto", there is nothing auto about having to manually move the +.

As mentioned, I would love to have a proper McIntosh to power my 4ohm Quarts. The ability to connect 4ohm speakers without all the negatives that come with it is fantastic.

On a side note, 105WPC would not be the spec of choice for me. Just stating facts of the amp in question.

 

[AcuDefTechGuy]

However, it does double down.

What do you mean?

 

[zumbo]

What do you mean?

Really? Gonna need to get the mods to deduct some of that rep.

105W@8ohm. 210W@4ohm.

105 x 2. Double power.

 

[its phillip]

Eat crow! As you move up, the power doubles.

My reply from McIntosh:

4 ohm speakers on the 8 ohm connection gets 210 watts, but generates more heat than the amp can dissipate and is bad for it.

I wouldn't call that a good thing...