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Magnepans and Amplifier Current

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#1
I'm looking to get some Magnepan 1.7i. From what I've read, they are low sensitivity, like my KEF LS50 speaker. But they also apparently like high current to be at their best.

I'm looking at getting Purify ET400a-based monoblocks. They are rated at about 425W into 4 Ohms and current is like 25A. These are supposed to be like the successor to the Hypex units. Now I know I'm on ASR and these amps should all sound the same, but for those who believe in audible differences I've heard that the Purifi is supposed to be even better sounding with improved soundstage and clarity.

The other option is Hypex NC1200-based monoblocks. They are rated at about 700W into 4 Ohms and current is like 40A.

Given the above, which is likely to get the best out of the Magnepan 1.7i speakers?

Thanks!
 

CDMC

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#3
I'm looking to get some Magnepan 1.7i. From what I've read, they are low sensitivity, like my KEF LS50 speaker. But they also apparently like high current to be at their best.

I'm looking at getting Purifi ET400a-based monoblocks. They are rated at about 425W into 4 Ohms and current is like 25A. These are supposed to be like the successor to the Hypex units. Now I know I'm on ASR and these amps should all sound the same, but for those who believe in audible differences I've heard that the Purifi is supposed to be even better sounding with improved soundstage and clarity.

The other option is Hypex NC1200-based monoblocks. They are rated at about 700W into 4 Ohms and current is like 40A.

Given the above, which is likely to get the best out of the Magnepan 1.7i speakers?

Thanks!
I have owned 6 pairs of Magnepans over 25 years, from SMGa's up to 3.5r. If I had a dollar for every time someone incorrectly said they require a lot of current, I would be rich. It is simply not true.

The easiest way to look at this is from the amplifier perspective. An amplifier is a voltage device. In response to a set input from the preamplifier, the amplifier outputs a set voltage. This continues until the amplifier in unable to supply sufficient current to maintain the voltage and starts to clip. Ohm's law dictates the required current, it doubles from 8 ohms to 4 ohms and again into 2 ohms. The only fly in the ointment is that speakers with a high phase angle can require more current than a straight Ohm's law calculation would show.

In the case of Magnepans, they are almost a perfect resistive 4 ohm load with low phase angles. Some drop to 3 ohms, but not at low frequencies where the most power is needed. Lets run some quick calculations:

Purifi 1ET400- 425w into 4 ohms- This is 41.2 volts and 10.3 amps of current. At 3 ohms to maintain the same voltage the amplifier would have to put out 13.7 amps which would net 565 watts. The Purifi is rated at 25 amps of current.
Ncore NC1200- 700w into 4 ohms- This is 53 volts and 13.2 amps. At 3 ohms to maintain the same voltage you are at 17.6 amps which nets 933 watts. The NC1200 is rated at 40A peak current and its limiter cuts in at 38 amps.

As you can see, Magnepans are not getting close to the limit of the current capabilities of either of these amplifiers. Any amplifier that is designed to drive a 4 ohm load will comfortably supply enough current for Magnepans.

The real issue, as you point out, is that Magnepans have low efficiency and require a lot of voltage (e.g. watts). The question is how loud do you listen and how large is your room? I know with my 3.5s and 700 watts to each (high passed at 80hz), they could only put out about 102db peak in my room (which is loud, but not extremely loud). There is only so much output the panels are capable of.

In most cases, the Purifi will have enough power for the 1.7s. Going to the NC1200s will net you 2 db more output, if the 1.7s are capable of actually putting out more output. In terms of quality, the Purifi measures a bit better, but both the Ncore amps and Purifi measure better than the limits of a 16 bit recording and the differences are likely inaudible. So the question is do you want excellent measurements or really excellent measurements?
 

CDMC

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#6
You could be even richer if you'd read what Magnepan has to say about their own speakers:

amps "with high current capability" work well

https://www.magnepan.com/faq#receivers
You mean their incredibly outdated and inaccurate information? They have a lot of it:

“There are a few general design recommendations we can offer:

  • Subwoofers - The subwoofers that move a lot of air and are impressive in a demonstration are usually "sloppy" and become tiresome during extended music listening. Integrating a "musical" woofer is both expensive and tricky, but it can be done. Here is where your Maggie dealer will prove to be most helpful.
  • . . .
  • Speaker Cables - As with other ancillary equipment, we can't keep up. But we can offer this advice: a system's total performance is dependent upon on a balanced approach. Sometimes spending less in one area and more in another will result in a total performance improvement. This applies to cables and speaker wire as well as other ancillary equipment."
or maybe this gem:

"The most common question is about the amount of recommended power for Magneplanars, but, first, it is important to understand the role of current and the power supply. High current and the capability of the power supply is a good indicator of the QUALITY of the amplifier. The amount of power you will need is a matter of QUANTITY. High current and total power are two separate issues. The ratio of the power at 8 ohms and 4 ohms defines the quality of the sound probably more than any other aspect of the sonic performance. Typically, if the engineers got this right, they probably did a good job in other areas of the design."

or this one:

"Everyone understands they need plenty of power, but the role of power supply is not understood. There is one important concept you need to understand when shopping for an amplifier or receiver: and it is somewhat like understanding "good" and "bad" cholesterol. The ratio is very important. An Gold Standard for an amplifier would be to double the power at 4 ohms. This concept is important even if you are buying an 8 ohm speaker."

Or this great one?:

"A new type of amplifier (Class D) has become more popular because it is a "green" design and uses less power plus it is smaller in size compared to conventional amplifier designs. We have heard reports of Class D amplifiers shutting down when driving 4 ohm loads or sound quality that is less-than-desirable. Quite frankly, some sound very poor on Maggies. However, more recent designs of high-end models are much better. Because we do not have the time to determine which models of Class D designs are compatible with Maggies, we must take a conservative approach. Direct-coupled, Class A/B designs with high current capability have proven a good choice for many decades."


They should have left it at: Make sure your amplifier is rated into a "4 Ohm capacity". Their speakers are an almost 4ohm resistive load, not some nightmare Watt Puppy, Apogee, or Infiniti Kappa.
 

MRC01

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#8
[Magnapan says] ... "The ratio of the power at 8 ohms and 4 ohms defines the quality of the sound probably more than any other aspect of the sonic performance. Typically, if the engineers got this right, they probably did a good job in other areas of the design."
This, IME, is generally true. There aren't a lot of power amps that double their power from 8 to 4 ohms. But if you find a random sample of 5 different amps that do, I'll bet at least 4 of them (if not all 5) are well designed and robustly built. Take it as a rule of thumb, not a law of nature. There are a lot of good amps that don't achieve this goal, but there are very few bad amps that do.

As for advice for the OP: the most important part of selecting an amp is to ensure that the maximum power you will ever use, is within the amp's continuous power output rating for your speaker's load (4 ohms). In some ways, it can be argued that Magnepans are actually EASIER to drive than other speakers, because they have a smooth, flat impedance vs. frequency curve.
 

richard12511

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#9
I think people mostly say that because they’ve heard other people say that. The people they heard it from likely only said it because they heard someone else say it. Even the people with first hand experience that are saying that are likely just speaking from the experience of hooking up a new beefy amp and being fooled by expectation bias.

They are 4 ohm, though, which is tougher than a lot of entry level speaker. They seem to be a fairly easy 4 ohm load though, at least from what I’ve seen.
 

RayDunzl

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#10
There aren't a lot of power amps that double their power from 8 to 4 ohms.
I would say, with only fractional differences, they all (Ok, typical SS amps) do, within their operating limits.

Apply 2,83 volts to your 8 ohm speaker.

1 watt of power.

Using the same amplifier, apply 2.83 volts to your 4 ohm speaker.

Boom. 2 watts. You doubled down. Congratulations.
 

MRC01

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#11
I would say, with only fractional differences, they all (Ok, typical SS amps) do, within their operating limits.
What I meant was whether the amplifier's max continuous output power into 4 ohms, is twice what it is into 8 ohms. This is rare, even among SS amps. At their limits, most run out of current before they run out of voltage.
 

RayDunzl

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#12
What I meant was whether the amplifier's max continuous output power into 4 ohms, is twice what it is into 8 ohms. This is rare, even among SS amps. At their limits, most run out of current before they run out of voltage.
I would say, that for an amplifier that claims to double going from 8 to 4 ohms, the specification for the 8 ohm output is underrated.

I have an amp that is rated 250/350 into 8/4 ohms.

Had they specified it as 175/350 instead, it would seem to "double".
 
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Sir Sanders Zingmore

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#13
What I meant was whether the amplifier's max continuous output power into 4 ohms, is twice what it is into 8 ohms. This is rare, even among SS amps. At their limits, most run out of current before they run out of voltage.
Surely it's only theoretically possible. If you have an ideal amp with zero losses.
Can't happen in the real world
 

MRC01

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#14
Surely it's only theoretically possible. If you have an ideal amp with zero losses.
Can't happen in the real world
Doubling from 8 to 4 is certainly possible in the real world. It doesn't require an ideal amp with zero losses. An ideal amp with zero losses could continue doubling from 2 to 1, to 1/2, etc. but that's not on the menu here.
 

CDMC

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your nihistic sophistry is not helping the OP
Neato, you managed to combine latin and greek words into a poor insult. Apparently I am on the wrong site, I thought I was on Audio Science Review. The OP made a statement that is factually incorrect and repeated so often, I felt the need to refute it, as it seems to come up periodically. I supported my refuting of the statement with evidence. I also provided a conclusion, which was that either amp would work. Last I checked, that is how things are supposed to go here.

I would love for you to show me any decent amplifier that cannot drive a 4 ohm load comfortably. Outlaw, can, so can ATI, NAD, Emotiva, Rotel, Denon, Yamaha, Marantz, and any Class D module made by Icepower, Purifi, Hypex, and Pascal. A person shopping for an amplifier to power Magnepans does not need to worry about their amplifier's current capability, only how much power it puts into 4 ohms, as they need a lot of volts at 4 ohms because they are low sensitivity.
 

CDMC

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#16
I would say, that for an amplifier that claims to double going from 8 to 4 ohms, the specification for the 8 ohm output is underrated.

I have an amp that is rated 250/350 into 8/4 ohms.

Had they specified it as 175/350 instead, it would seem to "double".
I have only seen one amplifier that actually doubles it output when the impedance is halved, the Sunfire Load Invariant. When Audio Critic tested the Stereo it clipped at 310 watts into 8 ohms and 620 into 4 ohms (rated at 300/600). When running the full suite of tests they found at 8/4/2 ohms it delivered 56v in a 20ms burst at phase angles from -60 to +60 degrees, but couldn't figure out if if sagged into 1 ohm because it ran out of current or their test machine wasn't working right at that high of power level.
 

Shazb0t

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#17
your nihistic sophistry is not helping the OP
Dude literally provided an entirely evidence based answer to the OP's question with the calculations to back it up and this is your response? Poor effort.

If your response is purely based on taking offense to someone calling out the Magnepan website then come on; it's clearly outdated and has some dubious statements as highlighted above. Why would acknowledging that reality really be offensive?
 
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Vasr

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#18
One thing to keep in mind about discussion of Magnepans. As a company, website, audience - they are stuck in a time-warp that moves at a glacial speed. You never see anything change but over time you notice something has changed but aren't really sure if it has. :)

Their web site which along with Outlaw belongs to the Craigslist school of web design was written at a time when there were actually some serious limitations with available electronics - people are so spoiled now with 300w amps being considered under-powered. It wasn't written with the audio engineer nerds that hang around here in mind but customers that may not have seen much more than the selection of Sony receivers in their local store or paper advertisements. The website basically told them there was more to it in a way they could comprehend and to consult a local audio dealer that was knowledgeable or call them.

The high-current need came about a time when a very large number of available receivers and amps weren't rated for 4ohms and not just because of UL certification or legal CYA. Most of the Japanese brands were giving fake and nonsensical power ratings in their specs (this persisted for a while even after FCC stepped in). Lot of the lightweight units had skimpy power supplies that couldn't provide enough current capability even for the advertised specs.

To compete, NAD (as an example) at that time had taken the approach of basing their advertising on dynamic headroom - the ability to provide a much higher peak power than continuous power with "high current capability". Since so many devices had no 4 ohm rating, the advice for Maggie queries was to look for one that advertised high current capability or alternatively headroom to be hopefully able to drive a less common 4ohm AND inefficient speaker at the time. That advice has stuck. It may be outdated now when amps and receivers routinely give 4ohm specs.

But, from experience, just a 4 ohm power rating that appears fine isn't enough. Some of them (for example. fairly recent Denon AVRs even) run so hot driving 4 ohm speakers (even simpler loads like Magnepans), that I wouldn't rely on them to last for long unless you provided external cooling systems whenever it was in use. I had a low-end NAD receiver once that would shutdown very often driving SMGa.

So if I was looking for an amp for a Maggie (especially Class AB), I would prefer one that gave its current capability in its specs along with 4ohms power rating for no reason other than those tend to be built to run without getting "too hot under the collar" driving a 4ohm load. It doesn't mean the higher the current, the better. You just need a "minimum hygiene" after which it doesn't make any difference. If the specs are specifying a current capability most likely they have enough. Or you can over-provision with power. Anything that claims above 200W into 4 ohms would have no problem providing enough juice for any normal level.

With contemporary Class D those concerns are far less (if not zero) since providing sufficient power and running cool has never been much of a problem for any decent module based unit.

Look for Magnepan to update their site for Class D amps sometime in 2030s.
 
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#19
I own a pair of Magnepan 1.7i speakers and drive them with Hypex ncore 250w modules and find they go sufficiently loud for my purposes. I am sure that the Purifi modules suggested would be an excellent match.
As @Wes stated earlier money spent on diffusers and absorbers (and I might add Dirac room compensation software) is likely to have a greater impact on final sound quality than another decimal point gained in amplifier distortion figures.
 

March Audio

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#20
I frequently get asked about Maggies and have to explain the points @CDMC has made about them. There appears to be a mythology that has grown up around them in the audiophile community that they require welding type amps. Not the case.
 

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