Why whole house surge protectors are not enough

So, MOVs are not perfect, or instant.  They live in two states, denial and confusion.

Hah!

I mean, on and off.  When off, they conduct no current at all.  However when they DO turn on they are not perfect, which is what is meant by Maximum Limited Voltage.  Essentially this is Ohms law:

V = A * R

In other words, the voltage that remains at the MOV is proportional to the current it's shunting AND the MOV's resistance.   In a perfect world, R would be 0 and therefore V would be zero.  A perfect switch, and no voltage across it, but since MOVs are not perfect, even when they've fully activated and are conducting they will have some voltage across them.

BTW everybody, current projections put Idalia over my house Wednesday morning.  I'll report back and let you know about any consequences of my preparation if I can!

Isn't it so that depending on their specs, MOV's can "clip" those occasional transient peaks of current to your amps so your speakers can not express those flash cymbal crashes for example. 

That's the reason that I pulled my Richard Gray MOV power conditioner out from my system and placed a Seimens Pro 140 at the circuit breakers. I'm in S Florida so it's a risk but I don't want any MOV's by my equipment. I think the Shunyata designer feels the same. 

I have a tricked out PI Audio UBER Buss power conditioner though. 

Isn’t it so that depending on their specs, MOV’s can "clip" those occasional transient peaks of current to your amps so your speakers can not express those flash cymbal crashes for example.

Not even a little bit true. You are confusing current with voltage.

An MOV activates when the (for instance) voltage between neutral and hot exceeds a limit, like 300V. Each MOV sits across a pair of wires and does nothing most of the time. There’s no current, no noise, nothing. It just sits there until a high voltage happens and then it turns into a closed switch.

A huge amplifier, playing at maximum output might cause the voltage to DROP below 120V. We call this sagging. The MOV would be even less inclined to activate with a big amp like that.

By the way, Richard Gray’s devices famously use a resonant tank to stabilize the AC voltage and eliminate noise and are parallel devices. If you don’t want it in line you can plug it into the other AC socket and it will still work. They do an excellent job of eliminating noise and keeping the voltage stable even when your amp is causing the voltage to sag.

Having said all of that, I encourage you to use Furman with SMP. It uses series mode protection instead of MOVs, though they do have an edge case that uses an MOV.

It may help you to understand that having a high voltage at your speaker requires more CURRENT (amps) from the wall which will probably lower the Volts at the wall socket. If an amp played music loud AND raised the voltage at the wall you’d have an infinite power device and not even Elon Musk can do that.

The plethora of things audiophiles do, like run dedicated lines with extra thick wires, use power regenerators and voltage regulators is all to keep the voltage at the AC outlet from sagging.

Sorry, current. My Gray was an old model from 2008. The Gray had chokes. Chokes compress dynamics I've been told. 

I have a 30A dedicated line connected to my Uber Buss power conditioner with a 30A Neutrik connector.

My UBER Buss does a better job with noise than the Gray. Power Factor Correction of 1 if memory serves me.

Caelin Gabriel of Shunyata advises the whole house surge suppressor at the breaker box, and no suppressor at the equipment rack and Garth Powell of Audioquest feels strongly for the opposite due to potential RF noise.