[rw@cn]

Hi Rollo,

 there was nothing wrong with the borrowed Levinson. Fantastic amp, "if you like SS". The issue was it was too powerful and offered too much gain in my system. Just too much amplifier for my tastes. I couldn't imagine a 28B on my 20.1 R's, lol. You got to be crazy Rollo  . I even had an Adcom 5802 that was clean at 450 wpc. That amp would also cause the fuse area, blue arcing light show. It would also move the panels across the floor. It never got over say 9-10 o'clock on the preamp (excessive gain issue). Both the Levinson and Adcom were more than enough horsepower. Let's just say I would cringe when a guest would come over and adjust the volume knob. Easy there tiger..... Neither the Adcom nor Levinson lacked any voltage or current. Quite the opposite was delivered.

 Going back to your 28B, I can bet you are not even using 1/4 of that amps capability, IF THAT.  So in MY mind, why buy such a large amp? Just my opinion here. Your money of course  . Guess I need to visit someone with 20.1's that has a kilowatt or more and see what's up. You would blow the fuses waaaay before you clipped the amp.

 I use a couple mono tube amps now. Each are rated at 45 wpc of full class A SET glory. They use the monster 6C33C output tubes. With a sub I get more than enjoyable sound levels. Matter of fact I even had the police over a few times, UNINVITED of course. Wasn't even pushing my amps then either. Anway enjoy your 28B's Rollo.

cityjim

When you say "fuse area" are you implying that you have bypassed the fuses?

Sorry, but I am having a hard time understanding your complaint about too much power. You really don't have to use so much power to get listenable music. How loud to you listen with your favorite amp. If you listen at the same level with the high powered amps, is the arcing visible then?

[berni]

I have 20.1 and nearly 1kw amp. Before that I had a smaller one and the difference is more then audible. Magnepan are low efficient, they say 85dB/ 2,83V  at 500Hz ,I say it is even less ..
If you want to listen at let say 85 db and the dynamic range of a good recording has a peak ok 20-30 db, what will a small amp do? Clipp, and that is what you can hear.
Also, what do we need to play this fast signal with 115db(20-30 above the listening)? If it is played as recorded, then the amp must deliver the power to bring the 85/dB efficient speakers to 115dB, you can calculate by yourself how much power is needed.(3db louder doubles the power) ABOUT 1 KW¨!

The power of an amp has nothing to do with how loud you listen, it means that the signal is well transported and not clipped.         

[rollo]

I have 20.1 and nearly 1kw amp. Before that I had a smaller one and the difference is more then audible. Magnepan are low efficient, they say 85dB/ 2,83V  at 500Hz  , but his can change ..
If you want to listen at let say 85 db and the dynamic range of a good recording has a peak ok 20-30 db, what will a small amp do? Clipp, and that is what you can hear.
Also, what do we need to play this fast signal with 115db(20-30 above the listening)? If it is played as recorded, then the amp must deliver the power to bring the 85/dB efficient speakers to 115dB, you can calculate by yourself how much power is needed.(3db louder doubles the power) ABOUT 1 KW¨!

The power of an amp has nothing to do with how loud you listen, it means that the signal is well transported and not clipped.       

  Si Senor, clipatitus. Oh my!!!


charles
SMA

[rw@cn]

I have 20.1 and nearly 1kw amp. Before that I had a smaller one and the difference is more then audible. Magnepan are low efficient, they say 85dB/ 2,83V  at 500Hz  , but his can change ..
If you want to listen at let say 85 db and the dynamic range of a good recording has a peak ok 20-30 db, what will a small amp do? Clipp, and that is what you can hear.
Also, what do we need to play this fast signal with 115db(20-30 above the listening)? If it is played as recorded, then the amp must deliver the power to bring the 85/dB efficient speakers to 115dB, you can calculate by yourself how much power is needed.(3db louder doubles the power) ABOUT 1 KW¨!

The power of an amp has nothing to do with how loud you listen, it means that the signal is well transported and not clipped.       

Which says to me that the problem cityjim is experiencing has to do with an excess of power into his speakers either that or something is wrong with his speakers (since he saw the  arcing with two different amps). Perhaps he couldn't get the volume he wanted with his tube amps (and tube amps exhibit clipping in a different manner than SS amps). Perhaps they ran out of gas. I am hoping that cityjim gives us a more detailed report of his problem and equipment.

[berni]

Arcing in my opinion has do with bad contacts or wire.. especially due to the fact it happened with two different amps.
If you load to much power into your Mg , the weakest point is going to "arc" or burn out. This should be  the fuse. But it can happen that it goes over the fuse and damage the ribbon.

[*Scotty*]

berni, have you noticed that your midrange panel crosses over at 330hz and is limited by the fuse value of 5 amps to 100watts of power input between 330 and 3000Hz.
 Doing the math results in a peak SPL level of 105 dB maybe 108 dB for very short duration peaks.
A 1000 watts is not going to go through the 5 amp fuse. This means that the speaker will never see 115dB peak SPLs above 330Hz either. 
 In the past Magnepan speced their loudspeakers at a maximum SPL capability of 105dB and they are still fused with the power input limitation that the maximum SPL constrains them to. You maybe able to get the bass panels to slap against the magnets if you hit them hard enough but this won't be music any more. I rather doubt that the bass panels will exceed 110dB with acceptable levels of distortion.
 The fuse values place a hard upper limit on the amount of power you can put into the speakers and there is no getting around that fact.
This of course has nothing to do with how they sound with amplifiers of varying designs and power ratings.
Scotty

[andyr]

berni, have you noticed that your midrange panel crosses over at 330hz and is limited by the fuse value of 5 amps to 100watts of power input between 330 and 3000Hz.

Scotty

My own mid-panel fuses have been removed. 

This of course has nothing to do with how they sound with amplifiers of varying designs and power ratings.

And has nothing to do with the fact that - IMO, at least - the reason to have higher power rather than lower is to have the headroom to faithfully reproduce transients.    I would suspect even a fast-blow fuse will not blow when several 100 watts pass through it for a millisecond.

Regards,

Andy

[Crimson]

And has nothing to do with the fact that - IMO, at least - the reason to have higher power rather than lower is to have the headroom to faithfully reproduce transients.    I would suspect even a fast-blow fuse will not blow when several 100 watts pass through it for a millisecond.

Absolutely. Higher power offers more headroom without clipping. That's about it.

[berni]

Of course 115dB is over the top for Maggies, but I wanted to show the ratio of high dynamic range of music and the power needed to reproduce it.
So compresion will occur, it can be because of the fuse, the limitation of the speaker or the source being played, but it can also be compressed already by the amp not delivering the power!
You choose which compresion would you like to change or eliminate or do you want to have them all?
Like others mentioned it is all about the headroom and reproducing  transients.

[rw@cn]

Try this: http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm

[andyr]

Absolutely. Higher power offers more headroom without clipping. That's about it.

What I believe you are talking about, Crimson, is the headroom required to, say, deliver an orchestral peak which is, say, 10-20dB above the level you are listening at.

That's certainly important but I'm talking about "instantaneous headroom" - ie. the amount of power which is required to be delivered in, say, a millisecond, to faithfully reproduce the leading edge of a loud transient.  AIUI, that's a much bigger figure than that required for an orchestral passage lasting a few seconds.

Regards,

Andy

[josh358]

What Andy said. A fast blow fuse might blow when subject to twice its rated current for 1/10 second. It's more like a VU meter than a peak meter. The fuses also cover only part of the spectrum, tweeter or tweeter and midrange.