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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
yyzsantabarbara
4,971 posts
 
@diamonddupree Those numbers you listed was why I am still investigating more power. However, I really wanted make the AHB2 work because I like it more than other amps (I have heard a lot). For less than $3K I think I will improve my sound a lot by going mono. Even though the AHB2 is not officially rated at 2 Ohm because it cannot run a test tone for 30 minutes at 2 Ohm (the AHB2 in stereo can). I think that is inconsequential now after my test yesterday. Even if it clips the forward correction will stop that from getting to the speaker.

Since I have been investigating other amps. The 2 other lines I was considering are:

CODA #8
  • 150 | 300 | 600 (approx. first 18 watt class A but halved as impedance halved)
  • 250 | 500 | 1000 (approx. first 12 watt class A but halved as impedance halved)
  • 400 | 800 | 1600 (approx. first 8 watt class A but halved as impedance halved)
  • SNR 118

CODA #16 with a SNR 130 and first 100 watt Class A. I think it's power rating is as follows,  150 | 300 | 600.

The upcoming Class D Puriif amps with 1000+ watt in 2 Ohm. These ones maybe the closest sounding to the AHB2.

I was also considering the Luxman m900u which is similar in spec to the CODA #8 (150 | 300 | 600) but 3x the cost. It sounds great and the only one I have heard from this list.

I should be able to get a second AHB2 next month.
diamonddupree's avatar
diamonddupree OP
75 posts
 
@yyzsantabarbara a second AHB might not even do it. There's a pair of Belo Canto Ref 1000s available right here on Agon I think for less than $2k. 
mapman's avatar
mapman
22,509 posts
 
ref1000s do not have custom input stage for best tube amp results nor beefed up power supply.....stock icepower. So may not be best still for a 4 ohm load or use with tube pre-amp if needed, ....even though 500 w/ch. You need somewhat pricier ref1000m for that. ref1000m is what I have been using for a number of years now and still sound very good.  Drives every speaker I have  thrown at it to the max  (Ohm, Dynaudio, KEF)  and never breaks a sweat.
erik_squires
16,410 posts
 
If you are looking into CODA, try the Sanders MagTech.  Made by CODA with built in power supply regulation.  The only other big amps I know of who have any sort of regulation are the Krells.  I'm sure there are others though.

That was going to be one of my suggestions from the start, but I thought you wanted to stay with bigger brands.

Best,

Erik
erik_squires
16,410 posts
 
PS - When it comes to convolution filters and roon, I go 100% with Toole. I think they are too much, and if you want to go that flat, what is the point of your speaker brand to begin with?

With Roon, I prefer minimal EQ, using parametrics. It maintains the character of my speakers, reduces CPU demand on the Roon server, and does the least harm. Also, prevents over-EQing for 1 spot.
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