a matter of spl
In my experience, what you are describing is a matter of SPL.
Crank up loud, get close to the speaker with your guitar, and you are there.
The CLR will get ridiculously loud but also sustains and rings at reasonable volumes too.
I personally don't want to expose my ears or my fellow musicians on stage to loud SPL levels. The extra ring and feedback is not worth the SPL to me.
Richard
Yes, it is a matter of sound pressure level, to a degree, because as volume diminishes, the ability of the speaker to vibrate the stings falls of precipitously. However, it does not need to be terribly loud, as you pointed out, to achieve various feedback effects, from subtle colors to all out higher order harmonic sustain. especially if you are in relatively close proximity to the amp. However, with a monitor, regardless of where you stand, you will never get a similar set of harmonics to that which a 12 run by a an variably sagging power amp will, nor will the tone and harmonic content be continuously variable as volume is increased, as it is with a real guitar speaker. Remember, the lexicon of sounds that we all grew up listening to were (first and foremost) all created by a guitar in front of 12 inch speakers and (usually) a somewhat (or often VERY) loud power amp running them. Full range speakers will never shake the stings in that manner, and so cannot create the entire experience (ala Robben Ford, Hendrix, Larry Carlton, Eric Clapton, Duane Allman, Van Halen, Scott Henderson, and the endless list of others.)
Don't get me wrong, it can sound great in certain applications to use a full range monitor with the Axe. I did a 60's show for several months that leaned much more towards the pop side than the rock side, and I used a mackie DL12 for that. it is a coaxial monitor rated at some ridiculous wattage (2000) and, although not as good as the rcf stuff i have heard, is still light years better than any non coaxial monitor one could find. For all those clean and semi dirty tones (Beatles, Beach Boys, and a bunch of other clean and semi distorted tones) it sounded great. It did killer Motown sounds (on the cleaner, less pushed side) and so on. ANY non coaxial monitor is a total non starter for any sound. They just sound bizarre, and NEVER reproduce anything like a proper feedback relationship with the guitar.
But for situations in which I want a real soloing voice for rock and fusion in which there is a fully dynamic relationship between the guitar and the amp, the axe (for me) works best with a real tube amp (pushed hard)and guitar speakers, cab sims off, power amp sims on, but tweaked for the amp and various patches. It behaves like a real amp, but with HUGE benefits an amp could never achieve in terms of flexibility and variety of sounds. I might someday entertain the idea of using both a real amp and coax monitor (perhaps the CLR) and have the best of both worlds (sound men will hate me, however). It is true that lots of "production" sounds translate better with that setup, including the cab sims (for instance, the Beatles Vox based sounds I was able to get were GREAT, and would not translate as well with the Axe married to a real amp). But, if i Have to choose, and for now I Do, I would choose the AxeII with the real amp setup for material in which I really wanted to have a credible guitar voice.
Scott suggests below that the CLR reacts much more like a real guitar speaker in terms of its feedback relationship. Perhaps I will be surprised, but I am reticent to throw a grand towards something I have never heard, and the arrival time of which is completely uncertain. So in the mean time, I will continue to use an amp in most settings, and a monitor for only very quiet or super small settings.
