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What is Floyd Toole saying about extra amplifier power and headroom?

I've been reading Floyd Toole's "Sound Reproduction The Acoustics and Psychoacoustics of Loudspeakers and Rooms" and came across a passage that I wish he went into further detail about. It has to do with whether having amplifier headroom has any noticeable improvement in sq. He happens to be talking about getting the bass right in small rooms, but in doing so, he also touches on the use of a larger amp for extra headroom: 

Remedies for unacceptable situations typically included spending more money on a loudspeaker with a “better” woofer (without useful technical specifications, that was a lottery of another kind) and a bigger amplifier (for useless headroom ...

It's the last part ("useless headroom") that I'm curious about. I have notoriously hard-to-drive speakers (Magico Mini IIs). Although the recommended amplification is 50w - 200w, in my experience, that's a bit of an underestimation. I'm driving the Minis with a Musical Fidelity M6PRX, which is rated at 230w @ 8ohms. (The Minis are 4ohm.) The combination sounds excellent to my ears at low to moderate listening levels, but I notice a slight compression in the soundstage at higher levels. My listening room, while small, is fairly well treated with DIY panels made from Rockwool, sound-absorbent curtains, and thick carpeting. So I don't think I'm overloading the room. But I have wondered if an amp with far more power than what's suggested (more headroom) would drive the speakers with a little less effort.

Those of you familiar with Toole or with driving speakers with power to spare, what are your experiences? If I went with, say, a pair of monoblocks that drive 600w @ 4ohm, would the extra headroom address the compression I'm hearing at higher levels? Or am I wasting my time and, potentially, funds that would be better spent elsewhere? 

Thanks!  


128x128diamonddupree
millercarbon's avatar
millercarbon
12,531 posts
 
Toole is right, headroom is useless. Literally. Headroom is by definition more power than you need. Translation: power you will never use. Translation: useless. 

You have made the rookie blunder of buying speakers that are hard to drive. Its not that they are 4 ohm. My Tekton Moabs are 4 ohm too. They are so easy to drive they sound marvelous with my little 50 watt tube amp. They would probably sound pretty darn good driven by my iPod. So (trigger warning!) you can forget impedance.

Buying speakers and amps is so easy. Yet it is not so easy some audiophile can't make it darn near impossible. All you do is eliminate from consideration speakers less than 92dB sensitivity. I know nothing about your speakers, except for having heard the name Magic and knowing that means they are crazy expensive and have a well earned reputation for being hard to drive. So without looking I will guess they are somewhere down in the mid to high 80's. [Fact check: 87dB. Tol ya so!] Which in itself is low enough to all by itself be a problem. 

Sorry, I only kind of glanced at the earlier posts, just enough to know you feel stuck with or married to those speakers. Oh well. Its not current. Its not headroom. Its not tubes or solid state or heat or ferrofluid or any of the other missing the point ideas. Those speakers simply eat power like its going out of style. The answer like I said is remarkably simple. Unless you yourself want to make it darn near impossible. 
mapman's avatar
mapman
22,456 posts
 
Its not "impossible". Like everything it just has to be done right to get the most out of it. The system is only as good as the weakest link. Not just any amp is likely to cut it with the Magicos.

I heard the minis off a very pricey VAC tube amp and a 6 digit system overall at Sound By Singer in a smaller showroom. That combo was top notch, as good as anything, at least at modest volume in a modest size room. The VAC had plenty of juice for the speakers in that room at modest volume. Did not try to go concert level though its not unreasonable to want to be able to do that. I do. But it may well take larger speakers as well to do that. Most monitors can’t, but Magico Mini’s are not most monitors.

Also headroom is not useless. It’s your insurance policy against clipping.
diamonddupree's avatar
diamonddupree OP
75 posts
 
@onhwy61 sorry, I don't have an SPL meter. And I'm not sure I understand the distinction between dynamic compression and soundstage alterations. I'll have to dig around and pay more close attention. Thanks!
diamonddupree's avatar
diamonddupree OP
75 posts
 
@mapman I've never been able to find anything showing the MF power output @ 4ohms but regarding current, the manual says, "current peak-to-peak: 140 Amps."

FWIW, it's a stereo amp (dual mono) and not an integrated one. Knowing that, would that point to the speakers being a limitation? And would an active crossover be the fix for that, something like this:

https://www.jlaudio.com/products/cr-1-home-audio-subwoofer-crossovers-96020

???

BTW, I already have a powered sub (JL Audio Fathom 110). And it seems to integrate with the Minis nicely. 

And the Bel Canto monoblocks are on my list of amps I want to try out. My local hi-fi store is a Bel Canto dealer so I think I can take them for a spin. 

diamonddupree's avatar
diamonddupree OP
75 posts
 
@millercarbon, I never said I felt stuck with or married to my speakers. The Magico Minis sound incredible to my ears. And I paid a fraction of what they cost new. So I have zero regrets. I'm here exploring tweaks to my system. If I wanted to read about your Tekton Moabs, there are 10,000 other posts on this forum where I can find that information. Give it a rest. 
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