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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
diamonddupree's avatar
diamonddupree OP
75 posts
 
@mapman thanks. Learning a ton. So I ordered a MiniDSP active crossover and should have it tomorrow and I'm going to try what you suggested. It's relatively inexpensive so I figured why not? The software also offers a bunch of parametric EQ customization, which I may play around with once I eventually get a mic to measure the room response. But my first concern with the MiniDSP (I don't know if you read my post from above) is that it seems to act as a DAC when I don't really want it to. I'm currently using a Mytek Brooklyn DAC+. The MiniDSP would come after it in the signal chain. What I'm wondering is, since the MiniDSP is a DAC, will it take over for the Brooklyn DAC? I really don't want it to. If the Brooklyn is already converting digital to analog, would the MiniDSP need to convert it again? Would it convert it back to digital and then back to analog again? If I run the Brooklyn into the analog input on the MiniDSP, would that bypass the DAC conversion in the DSP since it's already receiving an analog signal? I'd much rather have the Brooklyn handle the conversion and just use the MiniDSP to handle the high pass filter to the mains. I know, lots of questions. Thanks again for your responses! 
diamonddupree's avatar
diamonddupree OP
75 posts
 
@mapman oh, and yes, I've been listening way too loud! I shouldn't be doing that but sometimes I just can't stop myself! 
yyzsantabarbara
4,929 posts
 
@diamonddupree I was referring to the MiniDSP UMIK-1 microphone and not any DAC. This mic is tightly integrated with the REW software.

@diamonddupree Get the miniDSP UMIK-1 microphone for $100. Then download on a Windows 10 computer REW software. I am not sure if it works on a MAC.

mapman's avatar
mapman
22,399 posts
 
My understanding from quick read is the minidsp device can function as an active crossover and it’s internal implementation is digital. Crossover goes between pre amp and amp, both analog. So the digital crossover must then first do Analog to digital conversion, then work its magic digitally then convert back to analog for output to amp. That is a different function in the system than the DAC. The DAC takes a separate digital source and converts to analog for an analog input into a pre amp.
So the digital part of the minidsp is really a black box. It all happens internally and being digital that enables many potentially marvelous things not possible with analog. How marvelous or not? The only way is to try and hear. It either will make things sound better or not depending how you use it. I would not get hung up on the extra conversions between digital and analog it does. That just an ingredient in the final results. It’s the final results that matter. Personally it sound like a very smart design and I may try it myself possibly someday unless I spot something that sounds even better by then.
atmasphere's avatar
atmasphere
11,928 posts
 
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.
Actually in practice a DBA is easier to set up than a single sub, since you don't have to work so hard getting the bass right at the listening chair! When I installed my setup, I already had speakers that made deep bass (flat to 20Hz) so I only added two subs. I only placed them once. Only hooked them up once (IOW didn't play with phase). I used cheap speaker cable. I didn't mess with the amplifier crossover settings more than once. It worked perfectly the first time. By comparison I have a single sub in my bedroom, and moving that thing around so I finally got bass where I wanted it (and not all the bass is there, its a bit of a compromise) was a bit of a pain, plus the sub is sitting in an obvious space, but where it would be convenient doesn't work- no bass in that location.

Well its 45 amps per monoblock X 2 = 90 amps total.....nothing to sneeze at especially with a most efficient Class D design.
Uh- can we do a bit of math here? If 45 Amps, giving the amplifier the benefit of the doubt, so driving a 1 ohm load. The power formula is Power = Isquared x R where

power is in watts
I is amps (in this case 45) and squared

R is the resistance of the speaker

This means that if the amp makes 45 amps it also is capable of 2025 watts. If we are talking 4 ohms, then the output power is 8,100 watts. Clearly this isn't happening. A speaker that only dips to 4 ohms isn't going to need that sort of current in any event. The OP simply has no worries in this regard. The fact that the amp is class D is irrelevant in this regard and will behave as an ideal voltage source driving this speaker.

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