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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
erik_squires
16,552 posts
 
I think he’s referring to the overall truth that getting bass right is complicated. Too many focus on larger and larger speakers with lower -3dB points and bigger amps when the problem is the room and speaker integration with it.

Power in a consumer amp isn’t nearly as important as low output impedance, low noise at 1W and low distortion. You would be amazed at how much bigger a speaker / amp combination sounds in a well treated room.

Now onto your particular speakers... You are going to be limited by the maximum displacement of the 7" diaphragm. Assuming you have dealt with the room well, and it sounds like you might have, your next step would be to add a subwoofer.

I’ve written a couple of articles here which may help you.


https://speakermakersjourney.blogspot.com/2020/01/the-snr-1-room-response-and-roon.html


https://speakermakersjourney.blogspot.com/2020/04/how-to-not-buy-subwoofer.html

While I’m very pleased with the SNR-1 in room response, the truth is that the 7" woofer will limit the maximum volume before compression occurs. I’ve been to the Magico demo room and hears the S1 Mk II where they also do an impressive non-sub demo, but physics are real. For music, you can get impressive bass out of 7" (as I write), but it will always be limited by the physics of the maximum travel of the driver. In this demo, Alon used "merely" 150 watt amps. :)

https://www.6moons.com/audioreviews/magico/mini_2.html

When I want rock-concert levels, a subwoofer is my best choice, and what I use when watching action flicks. :)
mapman's avatar
mapman
22,605 posts
 
More power and headroom alone may help get bass right especially at high SPLs by avoiding clipping, but alone is most likely not a complete solution in most cases.

Current delivery and related damping factor of an amp also contributes. How much will vary but more difficult load speakers generally benefit from more current delivery capability to control the bass better, meaning a beefier amp than one perhaps of similar power but less current delivery capability. Power and current are not the same thing.

For example Magnepans are not very efficient and benefit from more power but not nearly as much from more current than many dynamic models. Smaller dynamic designs with more extended bass tend to be the least efficient and to also present a more challenging load, so more power and current is typically the key there.

OF course then room acoustics are a big factor for bass frequency response and all that goes with that as well, but that has nothing to do with the gear itself. Once you have an idea of approximately where the speakers will be located, its much easier to get the gear matching right first, then deal with the much harder room acoustics after. Having flexibility in final speaker location is a big help when it comes to bass and room acoustics in general.
diamonddupree's avatar
diamonddupree OP
75 posts
 
Thanks @erik_squires, IMO, all speakers, even floorstanders, could use a subwoofer and I have one in my system, a JL Audio Fathom 110. It has a 900w class D amp and auto room correction. I have the LP freq. on the subwoofer set to 38hz; the Minis go down to 37hz. With the room correction and the LP freq where it is, I feel like I have the sub and satellites integrated pretty well, at least to my ears. I’m using a single sub because I don’t think the room can handle a second one, and after reading Toole, it seems like I have the recommended placement just about right.

Edit: Here's my room:
https://systems.audiogon.com/systems/9016

What do you think the effect would be of adding extra headroom? Or should I be looking more at low noise and low distortion?

Thanks for the links. I’ll read them now.
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