What happened to the loudness control?

Such intolerance for tone controls! Who makes equipment that keeps the acoustic impact equalized across the entire power spectrum?

If I'm listening at low enough levels to want a loudness button, the sound is compromised anyway and the button would improve my listening experience. I would be nice if it was out of the signal path when off.

No, I do not miss the "loudness" button nor do I miss the tone controls in my ref system.
(I do have both in my HT & bedroom AV receivers! My HT receiver has a "direct" button allowing me to bypass loudness, bass & treble boosts).

Loudness button is just a bass boost button that increases bass by 6-9dB. It's a filter. Tone controls are filters as well.
Both colour the sound while providing the function intended. If one considers purity of the signal then these control compromise it. You can use the best parts to create these controls but it WILL alter the original music signal.
The approach taken in higher end audio equipment was/is to use the shortest path between input & output while still providing the required function (preamp or power amp or D/A or step-up, etc). Has higher end audio acheived this goal? Subject of endless debate!! :-)
Less signal processing => less compromised sound & a better chance that you will be hearing the recording rather than the electronics.

The "purest" of audiophiles, the vinyl fans, think nothing of the RIAA equalization (drastic) that is applied to their signal. And yet the minor adjustments needed to restore tonal balance at low volume is viewed with horror. A loudness control can hardly be called "processing". It requires no additional amplification stage, and can be switched out if you prefer.

When properly implemented a loudness contour is a wonderful thing. It's well established that the human ear becomes less sensitive to both low and high frequency sounds as the volume level is reduced. A properly design loudness contour will counteract this effect and restore the intended tonal balance when listening at low sound levels. In analog equipment a loudness control should not be a fixed EQ button, but instead a variable EQ knob that applies different EQ at different volume levels. Only a few manufacturers ever did it right. In the digital domain, Tact preamps/room correction devices allow for multiple user defined loudness curves. I believe Meridian's digital speakers have a similar feature.

I wonder if all those who berate tone controls, EQ and loudness compensation always listen at high volumes because their systems only sound "right" at high volumes. Improper tonal balance due to low listening levels is a compromised sound.

I agree with Onhwy61.

However, proper implementation of tone controls and loudness contour controls would have an extremely bad effect on our declining hobby. Sales of cables, IC,s, etc ect etc would fall like a stone. IMHO, many folks are using cables/IC's, etc, as tone controls of some sort. Actually, its worst that that, because a lot of equipment is bought/sold for nothing more than tonal reasons which could be corrected by a versile TC or loudness compensation control. If you think I'm FOS, pay close attention to the questions asked by folks here (as well as the responses) and see how many questions arrise out of a search for true neutrallity. Most are "how do I get more bass", "How do I get rid of boomy bass", "How do I get rid of the brightness/glare", etc, all of which could be handled by properly designed and implemented frequency bending devices.

One of the reasons for not including such in high end equipment that I have always loved was "that the controls would be mis-used by the end user", even though this same end user was discriminatory enuf to buy that piece of high end stuff and could obviously hear its merits, never-the-less he would be an acoustic ignoramus and use the TC's distructively.

Humm.....just food for thought. By the way, I keep a seperate tone control (with low,med, and high frequency adjustments as well as high and low filters in my tape loop. I use it to compensate for some problems with old LP's and CD's. Don't have to use it often, but when I do its well worth it!