Hello, I read with great interest your exchanges on this subject even if I do not have this amp.
I'm surprised by this statement: "transient spikes don't clip the amp's output. Clipping a solid-state power amp can blow your speakers out in a short time."
I have the impression that many of us spend our time sending square signals to our favorite HP, it could easily be likened to power amp clipping, right?
Besides, what is the operating class of this Matrix amp?
@DanielePanza
I did some additional reading on this topic and it appears that my previous explanation was incorrect and should be disregarded.
This article was an informative read. This is my updated understanding. I recognize that this understanding is still surface level and I welcome input from anyone who can offer an informed perspective to correct me where I get things wrong.
Clipping a power amp does not cause direct current (DC) to be fed to the outputs. Apparently, this is a widely parroted myth. An amplifier will only produce a DC output signal if the amplifier's circuitry has become damaged. Running an amp under conditions where it is constantly clipping may eventually lead to damage to the amp circuitry, but that is not usually the case for transiently clipped signals. It is true that DC from a damaged power amplifier will likely destroy a speaker, but that is not the most common reason why a clipped amplifier signal will destroy a speaker.
Amplifiers are rated for their maximum power output with preproduction of either a sine wave or full range input signal at a arbitrarily specified cutoff threshold of a certain percentage of total harmonic distortion. For example, one of the amps that I own is rated for an output power of 700W, 0.03% THD at 8 Ohms per channel with a 20Hz - 20 kHz input signal and 800W, 1% THD into 8 Ohms per channel with a 1 kHz sine wave input signal. Those ratings would be considered the maximum clean power of the amp into 8 Ohms per channel. If an amplifier is driven beyond the rated clean power level, the THD
and the total output power both increase beyond the clean power ratings. An amp driven to square wave clipping can exceed the rated clean output power by several multiples. If this level of power output goes beyond the power handling capacity of the connected speaker it can overheat the voice coil(s) and cause speaker failure. It is the large amount of extra signal power that causes the speaker to fail and not the clipped nature of the signal.
This explains why it is fine to cleanly reproduce a distorted guitar sound. So long as the total output power of the signal does not exceed the rated capacity of the speaker it will be fine no mater how much distortion is contained within the input signal.
The author of the article makes the argument that using an amp with lots of excess headroom above the rated power handling capacity of a speaker is a poor choice because too much power is what kills speakers. The mismatch caused by using a high power amplifier with a lower power rated speaker makes it easy to destroy your speakers if you don't know what you're doing. It is undoubtedly true that a high powered amplifier turned up so that it puts out more clean RMS power than the rated capacity of the connected speakers will destroy those speakers. Most speakers can handle transient spikes of power that go beyond their rated RMS power handling capacity so long as the RMS power of the signal is still within the rated power handling capacity. The advantage of using a high power rated amplifier is that you avoid any risk of clipping when large transient spikes in power occur.
I previously stated that it is perfectly fine to use a high powered amplifier with a lower power rated speaker so long as you gain stage the signal appropriately. Nothing I have read so far has lead me to discount that assertion. So long as you turn up the amplifier's input gain incrementally it is quite likely that you will reach sound pressure levels that are unbearable well before you reach a power level that will destroy your speakers. This assumes that the cabinet you are using can put out high sound pressure levels. If you connect a GT800FX to a 1W rated speaker I would expect you to destroy the speaker before it gets to bar band performance volume levels.
My previous recommendation to use an amp with at least 2x the power rating of your speakers was based on the understanding that a clipped amp can easily kill a speaker. As I just discussed, that is only partially correct. The logic was that more clean power = less chance of clipping = less risk to destroy your speakers. My evolving understanding of this subject leads me to conclude that while this recommendation may be fine it is also not necessary. Pairing a speaker with an amplifier of the same rating can in fact be fine (e. g. a 100W amplifier with a 100W speaker) because the amplifier should have sufficient clean power to drive the speaker to appropriate volume levels. However, you don't want to drive that setup beyond the clipping point of the amp because that is a recipe to destroy the speakers. It is also fine to run a lower powered amp (e.g. a 50W amp into a 75W speaker) so long as you don't drive the amp into clipping (again, you risk destroying the speakers if the amp clips too much here). If my understanding is correct, it is always fine to run a low powered amp into a high power handling speaker cabinet (e.g. a 10W power amp into a 100W speaker cab) even with tons of clipping because the speakers can handle the extra RMS power. This is why you can clip the power section on a 100W tube guitar amp into a 300W guitar cab all day with no problems but you might blow your speakers if you do the same using a single 100W rated cab.
The bottom line is that too much power into a speaker is the issue. There happen to be several ways to achieve that undesirable outcome and using an under powered amplifier is only one of those ways.
