Can under-powering a Guitar speaker do damage?

Here's a question I get often: "You recommend a 150 watt speaker for my 40 watt amp? Will my amp have enough power to push it? I have heard that under powering a speaker can do harm." Guitar speakers are typically very efficient (high in SPL) and therefore do not require an abundance of power to push them effectively or to make them loud. The SPL on most of our guitar speakers is 98-103dB at 1 watt, 1 meter from a microphone. A 3dB gain can be achieved by doubling the amp power. A 5 watt amplifier, for example, could potentially give you 109+dB of output on a 103dB speaker. Sure, some speakers sound “better” with more power, but adequate sound quality can be achieved at lower volumes as well. Also, achieving higher speaker SPL requires a strong magnetic motor, lightweight moving parts (cone, voice coil, suspension), or a combination of both. Most guitar speakers use lightweight, full paper cones and lighter voice coils in conjunction with adequately sized magnetic motors. This allows for pushing them effectively with lower power. The power rating on our speakers is simply a maximum thermal limit. If you ensure your amp is rated lower than the speaker you are considering, the speaker’s power rating is not an issue (this only applies to guitar speakers). Plus, it is not very practical to apply 150 watts to a single, say 12”, speaker. While a particular guitar speaker may be able to handle 150 watts thermally, the result may not be very musical. So, you might ask, why Eminence does not rate their guitar speakers based on how they will sound? Well, we do not know if the amp you are using is bass heavy or high gain, if the cabinet is sealed, ported, open, or if your guitar has humbuckers or single coils, or etc., etc. In other words, there are just too many variables, so we must cover all the bases and let you know what the speaker can take at an extreme.