Marcl brings up a VEY important point - which I don't think a lot of people understand.
The fact that something may "limit the dynamic range of a system" DOES NOT mean that it will have any effect whatsoever on the dynamic range of the music you play through that system otherwise.
(Even though it may "limit the extreme ends of the range" it will NOT alter the dynamic range at levels in between those extremes.)
Having less power, or a lower S/N ratio, limits the dynamic range of a system in exactly the same way as my not owning a Formula 1 racing car "limits" how quickly I can get to the grocery store.
Unless I have an opportunity to go faster than my current Nissan will allow, having the car which COULD POTENTIALLY go faster will have no effect on how quickly I get there.
(And, even if I had a hybrid, which actually shut its engine off when not moving, it wouldn't go any slower than my Nissan when stopped at a light either.)
The MAXIMUM dynamic range a SYSTEM can have is limited by the difference between its noise floor and the loudest sound it can play without clipping.
So, for example, let's say you're playing a track, and the loudest cymbal crash is 32 dB louder than the average level of the guitar solo...
As long as your system is playing within its limits, it doesn't clip on the cymbal crashes, and the guitar solo isn't "lost in the noise floor", the relationship BETWEEN their levels will not change.
If you turn the Volume up 20 dB, they will BOTH get 20 dB louder, and the cymbals will remain 32 dB louder than the guitar.
And, therefore, your system HAS NOT ALTERED THE DYNAMIC RANGE OF WHAT YOU'RE PLAYING.
(When you turn it up you will perceive it as being more dynamic because our brains are wired to do so.)
Please note that this is a very slight simplification.
The dynamic range of content can be altered using something intended to do so - a "limiter" or "range compressor".
Loudspeakers in particular can also do something similar at very loud listening level (because their efficiency can actually change when the voice coils in the drivers get very hot).
However, under normal circumstances, and specifically regarding electronics, as long as the peaks aren't clipped, and the noise floor isn't high enough to be annoying, a system WILL NOT alter the dynamic range of what you're playing.
(When an amplifier is perceived as "having limited dynamics" it's usually really because it lacks sufficient power to reproduce occasional loud peaks without clipping them.)
There is also a technical distinction that, under some circumstances, we can actually pick out sounds that are at a level below the noise floor.
HOWEVER there is also a distinction the other way.
According to the folks who know how human hearing works our hearing has a maximum dynamic range of about 140 dB.
The quietest sound a human can hear, at least at certain frequencies, is "0 dB SPL", and the loudest noise we can stand is about "140 dB SPL".
(The sound rubbing your fingers quietly together makes is probably around 20 dB and a jet engine revving close by can get above that top limit.)
HOWEVER the PRACTICAL range of our hearing is much much lower.
In the middle of a quiet night you can hear blood rushing through your veins...
But just try to hear a quiet whisper after you've been operating a chainsaw for a few hours without ear protection...
Or after you come home come from a loud concert.
In real life the absolute highest quality vinyl recordings have a dynamic range of about 60-65 dB.
And, because of that, if you turn the volume up to where the loud parts are "really really loud", you can hear the surface noise...
Back in the days of vinyl it was widely understood that...
"You wouldn't hear the surface noise while the music was playing... but you absolutely would hear it after the music stopped."
"And, if you turned the music up really loud, after the music stopped the surface noise would often be very loud and quite annoying".
But both modern digital recordings, and modern amplifiers, have such low levels of background noise that we've come to expect it to be inaudible at normal listening levels.
THERE ARE REALLY TWO IMPORTANT POINTS YOU NEED TO TAKE AWAY FROM THIS.
1. As long as your entire system has significantly higher dynamic range than the content you're listening to, and your ears, it will NOT limit or reduce the dynamic range of what you're playing.
2. As long as your system has sufficient dynamic range to play the content that you're playing there is no audible benefit to increasing the dynamic range of your system.
Let me spell that out in plain English...
As long as your system isn't clipping, even a tiny bit, then more power won't make it sound better.
As long as you can't hear the noise floor of your system, even a little, then lowering the noise floor won't make it sound better either.
And, as long as you never ever exceed either of those two limits, then there is no reason to worry about dynamic range, and no specific benefit to improving it.
NOW...
Regarding amplifier power....
You've probably heard us, and many other folks, say that "having an amplifier far more powerful than you need will ensure that you get better dynamics".
This is often true in practice... but probably not for the reason you thing.
The reason is quite simple...
Music is VERY dynamic...
That means that, for example, in well recorded music with drums or cymbals, the peak levels on those drums may be a LOT louder than the average level.
So, literally, if the average level is a loud 10 watts, a single really loud whack on the drum may produce a single drumbeat that requires 500 watts to reproduce without clipping.
And, because of how both our ears and drumbeats work, if that drumbeat DOES clip, you probably won't perceive it as clipped...
Rather what you will perceive is that "the drum sounds less dynamic"...
So that more powerful amplifier will seem to sound "more dynamic" because it avoids those occasional clipped peaks.
(HOWEVER, other than when it's actually clipping, the dynamic range of the unclipped music will not be any different.)
Regarding speakers....
There are actually two ways in which loudspeakers CAN alter the dynamic range of content.
The first is that, as I mentioned above, when voice coils get very hot they change resistance, which causes less current to flow, and the speaker actually "draws less power".
The second is that, unlike modern electronics, the "magnetic motor system" in most dynamic speakers are not perfectly linear (for a variety of reasons).
This means that many speakers actually "get less efficient" as they start to approach the limits of their power handling capabilities.
These effects are usually collectively described as "dynamic compression at high listening levels"...
(But they really only affect speakers, and a few tube amps, and do NOT affect the VAST majority of modern sources, preamps, or amplifiers.)
The 2x4 HD will partially do what I need but my preamp and sub amp (Hypex NC252) are both XLR which means that I give up dynamic range on the subs if i just use RCA ins/outs. Thus the miniDSP Flex which has a bunch of stuff I don't need, but the balanced ins/outs I do need.
This is a good question for KeithL ..... dynamic range of balanced vs unbalanced.
While using unbalanced inputs may increase susceptibility to noise, resulting in lower signal to noise ratio, which could be equated to dynamic range in that context .... in practical terms your subs will still play full range without increased distortion at high levels if you use the unbalanced solution. I use the 2x4 HD to feed my L/R to the subs and I'm happy with the result.
It is unfortunate that miniDSP doesn't make the 2x4 Balanced anymore. I use one of them also, even though the wiring to the Phoenix connector is annoying and my subs have unbalanced inputs anyway.
