[miatadan]

Only concern I have right now is the low efficiency of Magnepan speakers in general.
All models show 86dB/500Hz/2.83v.

Martin Logan 91 to 92 dB/2.83volts/meter

When I had the Acoustat Spectra 22's they were 84dB efficiency and if I was playing music at loud levels, I was working the amplifier really hard 300watts plus peaks of 900 watts compared to getting same levels with 30 watts plus peaks of 300 watts on average using Martin Logan Spires.

Dan

[Minn Mark]

Perhaps you should audition some Maggies at a brick-and-mortar store and hear for yourself?  I have a SS stereo amp, 225W @ 8 ohms, and listen at levels plenty loud for my taste in rock (AC/DC).  I don't have meters, but I don't think I come anywhere near the levels you indicate with my 3.6R's in my 13x20x7 basement room.

If these are your requirements, maybe Magnepan's aren't suited for you?

Cheers, 

Mark

[rollo]

   Yes however at 4 Ohm load amplifier choices are many as power doubles with solis stte or class "D". Tubed amps another story. I have heard Maggies play quite loud with 70W.ch. My AR Classic 60 gives them good power no strain. Try it.
   


charles

[miatadan]

Closest store that sells Magnepan is 4 or 5 hours from me.

One disadvantage to autoformers in solid state McIntosh amplifiers is that the power output is the same regardless of output tap...

My spl meter indicated volume levels of 112db+ when I was using 30 watts playing though the Martin Logan Spires.
 I do have to take into account that the Logans had internal 200 watt amplifier driving the 10" woofer which total power comes to 500 watts per side as only the electrostatic panel is driven by the McIntosh amplifier.

The loudest volume level in my room was 127 db , at this point meters peaking at 600 watts with the Martin Logan Spires

[harri009]

I find 150 tube watts to be plenty of power for me,  I don't listen above 100db though

[a.wayne]

Closest store that sells Magnepan is 4 or 5 hours from me.

One disadvantage to autoformers in solid state McIntosh amplifiers is that the power output is the same regardless of output tap...

My spl meter indicated volume levels of 112db+ when I was using 30 watts playing though the Martin Logan Spires.
 I do have to take into account that the Logans had internal 200 watt amplifier driving the 10" woofer which total power comes to 500 watts per side as only the electrostatic panel is driven by the McIntosh amplifier.

The loudest volume level in my room was 127 db , at this point meters peaking at 600 watts with the Martin Logan Spires

127 db !


 I would bet the distortion was peaking with the meters too ..... 

[Paul McNeil]

By a pro amp (which many amateurs will not reccomend) that will output >700 watts, and you may be happy. I was. I'm using the Crown XLS 2500 with my Maggie 1.7s.

[Carl V]

at one time I had a Crown Macro driving Tympannis or 20.1
(The most magical sound I had was WOLCOTTS & A3 then A1)

Music Reference RM9 or RM 200.
Or consider Audio Circle  AVA amps.

[mcgsxr]

2nd Crown user here.  I am happy with my XLS 1500 driving my 1.6's.

It is the only amp I have run my Maggies with.  Part of buying it earlier this year was "in case" I found a set of Maggies.  The Crown did very well driving my then Totem Model 1's too.

I would bet anything over 100wpc will get you going.  IF you listen loud, then you may want a lot more.

[Larkston Zinaspic]

I once heard Maggies with a Plinius SA100...it was unexpectedly very good. Nicely authoritative, plenty of finesse. I could envision two of those boat anchors run in mono...double your pleasure.

[miatadan]

Considering the 5-6 dB difference in efficiency, I will have to play music at lower level's if I purchase Magnepan's .

In general most of the Martin Logan models ( Theos, Ethos, and Summit-X ) has not been updated in 5 years and if I remember correctly the ElectroMotive ESL was released in 2011. The Montis and Neolith are the newest models. May be best to see what happens in first quarter of 2016.

[josh358]

I wouldn't worry about the efficiency except insofar as it means you need to buy a bigger amp. Most people don't listen at levels that require more than a few hundred watts, though a few do (based on reports of SPL meter readings). If you have some SPL readings it will help determine what size amp you need. Note that the a larger amp won't generally increase subjective loudness, since that's determined by average levels so just about any amp will play plenty loud. What sufficient power will do is prevent clipping on the peaks, which can damage tweeters because of the high HF content and can sound bad (trumpets) or be inaudible, depending.

I wouldn't recommend the Crown XLS for Maggies, BTW, tried the 2500 and it sounds OK but in a level matched comparison it doesn't compare to a good audiophile amp. I'm not alone in that assessment. The caveat being that if you're on a really tight budget, you'll be delighted -- last years' XLS's are on sale and at the price, its hard to see what can match them.

[Davey]

If you have a set of speakers that require X amount of power to play at your preferred SPL, then you procure an amplifier that can supply X amount (or more) of power.
This is not complicated. 

Dave.

[I.Greyhound Fan]

I have a pair of 1.6's being driven by a Pass Labs X250 amp with 500wpc at 4 ohms.  The power meter on the front shows that the the amp rarely if ever leaves its class A operation which is about 25wpc.  I have seen the meter occasionally move on thunderous bass at loud levels.

[josh358]

I have a pair of 1.6's being driven by a Pass Labs X250 amp with 500wpc at 4 ohms.  The power meter on the front shows that the the amp rarely if ever leaves its class A operation which is about 25wpc.  I have seen the meter occasionally move on thunderous bass at loud levels.

Is it a peak or averaging meter?

[josh358]

If you have a set of speakers that require X amount of power to play at your preferred SPL, then you procure an amplifier that can supply X amount (or more) of power.
This is not complicated. 

Dave.

No, but no one seems to want to go to the trouble, even though it's less trouble than bringing an amp home and deciding it's too small.

A. Play music as loud as you ever do
B. Measure the highest level with a Radio Shack meter
C. Add 10 dB to allow for peaks and at least 3 dB of headroom, so a total of 13 dB
D. Start with Magnepan's sensitivity number, subtract 3 dB, then multiply power by 10 for every 10 dB above that number. So 93 dB requires 10 watts, 103 dB requires 100 watts, 113 dB requires 1000 watts, etc. This is the 4 ohm *peak* power that you need.*

*There used to be a power amp calculator online that worked for dipole line sources but I can't find it anymore. The ones for point source omnis won't work! But for a typical 8' listening distance you can just use the 1 meter reading, dipole room gain and 1/R attenuation with distance pretty much cancel at that point. In practice, if power is marginal and the amp will be driven into clipping, tube watts are about twice transistor watts, since tubes soft clip. Also, a good solid state amplifier will be derated while a cheap one won't be.

Finer considerations:

- Note that subjective loudness doubles for every 10 dB of power. So the 1000 watt amplifier will sound only 4 times as loud as the 10 watt one! Also note that the ear will overlook some peak clipping, typically 11 dB -- but not always, you'll hear it on trumpets.

- The peak-average ratio of acoustical music is 10 - 20 dB and the ear determines subjective loudness on the basis of average levels (which is why the VU meter is an averaging device -- it allows a DJ to match subjective level of tracks). What this means is that within reason, *amplifier power doesn't determine how loud you can play a system with acoustical music." It determines whether the amplifier will clip and be used in its nonlinear range where it doesn't sound very good.

- The smaller Maggies require less power. This isn't because they're less efficient but because they start to distort at lower levels so you won't want to play them as loud. Dacey found that the MMG had a 1/R^2 radiation pattern, it isn't a full length line source.

- In practice, I think most people will be happy with 200 watts or so but listening level preferences vary by several orders of magnitude (true) so measure to be sure.

- Reproduction of acoustical music at realistic levels is impossible with dipoles, but for near realistic levels, you need an amplifier the size of a Mack truck. This is for the very loudest music, though.

[Davey]

Well, this topic is confusing enough for many audiophiles.  Talk of tube-watts, soft-clipping, de-rating, etc, etc, just confuses the issue further. 

I think the basic misunderstanding from many audiophiles is....that if you have the power available you will be using it.  That's simply incorrect.
A 1000 watt amplifier will NOT sound 4 times louder than a 10 watt amplifier.  It will sound exactly the same.....assuming you're operating inside the rating of the 10 watt amplifier.

Tube watts, soft-clipping, de-rating, nonlinear range, etc, are all objective limitations that actually/really/positively reduce the power available from an amplifier.  Subjectivity is irrelevant for that conclusion.

Magnepan's are an interesting case.  Very inefficient but generally not capable of counteracting that with a 3db reduction per doubling of distance that a true line source would.  It's closer to 6db than it is to 3db actually.

There are not shortcuts in audio.  You need to have the right tool for the job.
If you want to pull a nice 5th-wheel around you need a big truck.  You can't soft-clip your way to the job with a Mazda Miata. 

Cheers,

Dave.

[josh358]

Well, you know me, I can't help but go into the theory. But in practice, it's simple -- measure, add 13 dB, calculate. None of this will be precise but it doesn't have to be.

I didn't know audiophiles had the misapprehension you mentioned. Really, in practice, it's pretty simple -- if your transistor amp is undersized, it will clip and you risk damaging your tweeters. If a tube amp, it will start to sound soft and compressed. Either way, studies have found that the ear is surprisingly insensitive to peak clipping so you may not hear the clipping at first -- typically up to 11 dB which is a *lot* of peak clipping!

I don't think there is much need to choose an underpowered transistor amp unless the bigger ones are too expensive, but in practice tube power is limited so the old rule of thumb -- you need half as many tube as transistor watts -- is a useful one. The soft clipping really does make a big difference, you won't fry your tweeters and you won't fry your ears, you'll just get that gentle tube overload sound that you hear on so many old recordings -- not offensive at all. Walter Sear wrote a classic AES paper on this in the70's (IIRC) which pointed out that the overload characteristics were why tube consoles sounded better than the transistor consoles of the day.

I know you measured the MMG's radiation pattern as 1/R^2 but I assume the larger ones behave like a proper line source because they run almost floor to ceiling. At lower frequencies, an MMG starts to look like a point source. Or really, a number of point sources strung along like Christmas tree lights. But with floor and ceiling reflections, the larger ones should approximate an infinite line -- actually a shaded line that's about 2-1/2 X the height of the listening room. So I think they'll fall off more like 1/R. (It also depends on how close you are, since you're listening in the transition point between near and far field.)

In practice it can be more problematic, I want to choose amps that will drive my IVA's comfortably at their limit but it isn't easy to figure out what that limit is! So I'm having trouble sizing the bass amp. Satie has measured more than 120 dB out of his braced Tympani IV woofers (he measured a 6 dB improvement when he braced them). I was pushing my IVA's above 110 dB when I was experimenting a few weeks back and they were OK with it on rock. The IVA's are listed as 87dB/1W/m @500Hz in the table, which makes them more efficient than most models. 200 watts will give you 110 dB at the listening position. So -- how much higher to go on the bass amp? I'm not really sure because I'm not sure how loud they'll go before they sound awful or blow the fuse.

[I.Greyhound Fan]

Is it a peak or averaging meter?

The meter on the Pass amp measures current draw.  At idle, it sits slightly less than half full scale, reflecting the standing bias current of Class A operation. As the amplifier exceeds its class "A" rating the needle on the amplifier will register the increased bias being drawn by the output stage."

[josh358]

Interesting, thanks. I took a look at that thread and it suggests that the meter doesn't read peaks:

"If one does it the way Nelson Pass suggested then there is no need for rectification at all. You just have to care you don't mess up the circuit's properties.

"I once did it on an ordinary class AB amp (abouit 20 years ago). I simply connected the series connection of a POT and a cheap meter across the emitter resistors of the output stage. No rectification, no filtering (the latter might be beneficial, specially in in my case). What the meter then showed whas the current load on the amp. On a highly biased amp like the X-series amps it is an indicator showing the actual "working area" of the amp. And as already remarked it looks quite cool."

A schematic would tell us for sure.