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
OP,

Although I've heard Magico speakers they were not your model.  Much good advice above (save for one comment on headroom).

I really think that you're trying to drive that 7" too hard.  And due to the slopes of the crossover there is not a "brick wall" at 37hz and 38hz.

I have a tri-amped system using an electronic cross-over spec'd for my system as in cross-over points and slopes.

You need to take the low bass load off the amp, which will take it off the speaker as well.  I think you might try a cross-over at 100hz give or take.
Go here and check out all the possiblilties:
www.marchandelec.com/electronic-crossovers.html
Phil Marchand can be a big help.
BTW, I have the XM-44 (It is tunable with different circuit cards).

Regards,
barts



Perhaps what @mapman was saying about increasing current flow could help this situation. I'll have to look into it. Thanks for your thoughts!
The thing is, when you have thermal compression there is a tendency to turn up the volume/throw more power at it (if there is increased current then there is increased power) but that does not help if there is thermal compression - in fact it makes it worse. But if you are planning to get some of the bass energy off of the woofer, then it will have less thermal compression. So Erik's suggestion should be looked into, as well as a Distributed Bass Array, since the shape of the room really isn't relevant (I'd talk to Duke at Audiokinesis about that since he is really one of the few selling a DBA-dedicated sub system). 
A DBA has its own benefits regarding good bass throughout the room but only 1 sub is needed to offload work and reduce risk of compression initially although a DBA might introduce some unique connection requirements that would have to be addressed sooner or later so best to consider that up front.

DBAs add complexity and would also likely take more time and effort to get right initially as a result. If it were me I would solve one problem at a time....resolve the problem at hand first with existing sub then consider adding DBA after that is resolved, but only if worth it for you.

OR try those Bel Canto Class D amps as well if you can with no financial risk. That would keep things simplest and might make a big difference. How much will depend on the Magico’s ability to go loud without significant compression and how well the current amps truly can stand up. Other Magico mini owners would probably be best ones to provide information on how well they go loud and dynamic. Compression is real but may or may not be a significant issue case by case. Smaller speakers certainly up the risk. Sometimes you never know until you try. It’s nice to only have to add subs to extend the bass, not as part of a solution to fix it. Unless you are a "bass hound", I would expect the Minis driven to their max to be all the speaker most would need in most rooms, at least if room is not too large.
If it were me that owned the Magico Mini’s like any very good speaker, I would do anything I could ie throw the kitchen sink at it as needed to allow it to perform at its best before adding anything else.

That’s what I did with my big Ohm 5s and it payed off 100%. No subs!!

I never felt a need to add a sub even with the Dynaudio Contour monitors, though for some more extended recordings it would certainly have helped.

I do use a sub with my kef ls50s. Those are the smallest monitors I have run regularly but wonderful within their limits and with a sub they are top notch, up to a certain SPL level that is more than satisfactory in the small room they are in. THe kefs + sub cannot compete with the much larger Ohm 5s in a much larger room with no sub in terms of going loud and clear.

The Ohm 5’s with the 500 w/ch Class D Bel Cantos are the bomb. You turn up the volume and they keep going louder and clear until you reach those very high SPL levels that eventually get uncomfortable and can even cause damage to to the ear no matter what. THing is you never realize how loud the things are actually playing until you try to talk to someone and hear. That’s always a good sign from a distortion perspective! I know Ralph would agree with that. Compression is not an issue.

My goal was to be able to do that. It took the 500 w/ch Class D BEl Cantos to do that. The previous 120 w/ch Musical Fidelity was no match. Nor the 330 w/ch Carver amp prior to that (voiced like a tube amp, limited current delivery into 4 ohms). The Carver did very well with the Magnepans I had prior to the big Ohms though.

Magico Minis.....those are very good standmount speakers.....larger than many if not most.   I would not expect them to compete with larger speakers of similar quality in terms of ability to go loud, but would expect them to be more than capable alone in a small to modest sized room driven to their max.  Again, would be nice if other Magico mini owners would chirp in with their actual experiences trying to crank up the minis.
@barts thanks, lots of customization with that unit. Are you familiar with the MiniDSP? Any thoughts on how they compare? Much appreciated.