Hello Venki,
Keep in mind, you do not need any impedance characterization if your multiway speaker system employs a constant impedance type of a crossover network. Such a crossover makes the amplifier SEE constant load impedance. With a fullrange speaker, since there is no crossover, we need a different approach to do its job.
Venki >> The crossover is passive and does not alter the power send to the loudspeaker (in the passband other than for the losses) and even in stop band it does take the chunk of the power (as heat). Hence I dont think you can compare crossover to the amplifier design which the way I understood "actively" changes the current/voltage to feed constant power to the drivers. May be my interpretation is wrong 
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Coming directly to your questions:
- what if the composer wanted to make a section of the song sound low. Will this amplfier change that.
No. Input signal is not touched and it will very much control the output.
Venki >> If the output power is not related or altered when compared to the input, my basic knowledge tells me that it will affect how it should sound.
In a different context, during my demo trip to Pune, one of the FM had specifically asked if the loud and soft passages would be affected.
He referenced the song Maan Mohaana from Jodha Akbar.
The song starts very softly in the background of a courtroom conversation and then gradually grows up to its full volume.
I had played that sequence to satisfy his query.
If he is reading this thread, he or any one who attend that session can pitch in to confirm the same.
- what if the driver is playing with its resonant frequency in the pass band. Especially subwoofers. Increasing power at output will result it damaging the driver.
Pass band should always cover frequencies slightly above the resonance frequency of the loudspeaker. A subsonic filter is normally included to do this.
Venki >> This is incorrect for sub and in some case for woofer as well. e.g. a well designed TL can have its resonance frequency (of the system) set to .75 of Fs. Only correct if you are talking about mids and tweeters (atleast 1 octave above Fs as rule of thumb).
- will eq have no effect on the system if we use your design.
EQ that you are refereing to is altering the input signal. So such EQ will affect the output response.
- imo most of the amplifiers have internal feedback to control the gain. Beyond that as one of the FM said eq (electrical or mechanical) should do the trick. And eq should be done based on a sweep/noise not with music.
There can be different approaches to solve a given problem. Each person is free to choose the approach he/ she is comfortable with
- can this design achive full bandwidth irrespective of the physical limitations of the driver?
No. We need to use the driver within its physical limitations. However, a given driver can be made to sound much better and truer with this method.
e.g. the 3" full range that I use in my designs sounds like a midrange with most amplifiers in the market. But with my system, it will wow you with its treble response. However, it is limited at its low end and so I use it with a woofer.
Again. FMs from Thane and Pune have experienced this and can pitch in.
I am referencing a few articles to help you understand the concept.
I hope that it will help.
1.
https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00298262.pdf
2.
https://www.electronicdesign.com/analog/make-your-audio-system-sound-better-smart-amp-technology
The article in link 1 explains in great detail how a soft tool can be used to characterize a loudspeaker. You can buy the evaluation system if you want to dig in deep.
I hope that this helps but do let me know if you have any further queries.
Venki >> This looks like a technology to a. Thermally protect the speaker (probably by reducing the levels before the speakers reaches its thermal limits) b. The smooth out HF and probably attenuate LF again with the intend of keeping the driver almost in its linear region. They are not talking about actively altering the output power based on the impedance. May be my understanding is wrong, other FMs who are experts can pitch in.
Regards,
Ravindra.
