What does more power do for Magnepans?

I tried to go back and study some of the math about maggies and power. These were pointed out by others; I am just trying to pass on their work and analysis correctly.

First thing I ran across was the way Magnepan spec's the efficiency. 86db/1m/2.83V. Evidently 2.83V into 4ohms is 2 watts and not the traditional ~db/1m/1w scale. At 1m/2w efficiency works out to 83db.

If you listen to music at a level that produces 83db peaks (fairly restrained, but still dynamic) and sit 3 meters away it flows like this.

2w/1m = 83db with one speaker
Second speaker adds 3db for 2w/1m = 86db
Subtract 3db for each additional meter away from the speakers 2w/3m = 80db
Each additional 3db doubles power required - to add 3db – 4w/3m = 83db
Figure the peaks @ 83db are 6db above the average spl = 1w/3m/76db

This ignores room loading, absorption, and the fact that the 2w/1m/83db is with a test tone, but on the surface, the amount of power needed doesn’t seem that great for modest listening levels.

If you listen at a level that produces 95db peaks it would go something like this…

2w/1m = 83db with one speaker
Second speaker adds 3db for 2w/1m = 86db
Subtract 3db for each additional meter away from the speakers 2w/3m = 80db
Double power for each additional 3db;
4w/3m = 83db,
8w/3m = 86db,
16w/3m = 89db,
32w/3m = 92db,
64w/3m = 95db

64w. Still not a lot of power for what, to me, is a fairly loud 95db peak.

It doesn’t match my (admittedly limited) experience, so I am fairly assured that I have stated something incorrectly or there is another important factor that is missing.

You won’t hurt my feelings by pointing out the flaws in the above but I do find the result interesting if it holds true

Jim S.

One thing wrong with your calculation. One subtracts 3db for every doubling of the distance, therefore 2m=-3db, then 4m=-6db, not 3m=-6db. 3m would be close to -5db, I suspect.

Bob P.

The biggest problem with that calculation is that to obtain a subjective doubling of loudness requires ten times the amplifier power. See: (http://www.gcaudio.com/resources/howtos/voltageloudness.html)

Thanks Bob,

A fundemental misunderstanding on my part. Does change the result, doesn't it!

Jim S.

I think I have corrected a couple of mistakes. Still ignores room loading, absorption, and full spectrum of frequencies.

86db/1m/2.83V = 86bd/1m/2w. Not 83db/1m/2w.

If you listen at a level that produces 96db peaks it would go something like this…

2w/1m = 86db with one speaker
Second speaker adds 3db for 2w/1m = 89db
Subtract 3db for each doubling of distance away from speakers. 3m = – 5db, or 2w/3m = 84db
Double the power requirements for each additional 3db;
4w/3m = 87db,
8w/3m = 90db,
16w/3m = 93db,
32w/3m = 96db.

32w. Not a lot of power for what, to me, is a fairly loud 96db peak.

I sat down yesterday and checked the SPL’s at the levels I listen. Loud to me is measured peaks at 85db on a RS meter. There may be unmeasured spikes in there from transients, but certainly no higher than 90db.

The reason this intrigues me is; I recently went to an active biamp setup from a passive biamp on 1.6’s with rather startling improvements. Much greater clarity and coherence all around, and at higher volumes. Having started on the more power helps bandwagon, I have being looking to pull the trigger on more powerful amps than the current 170w Arcams’ that I own (probably better quality too).

I want to be “smart” about it, but the analysis on paper doesn’t match my limited experience. No substitute for auditioning to learn is there?

Jim S.