Toole and why I like Tone Controls

Tim, it would be nice but doing it requires complicated programming of several DSPs running in concert and in control of the entire frequency range at 1/2 Hz intervals in a 48 bit system. You need to have the native frequency response of the system to start which means you have to do impulse testing with a microphone. Then you create filters that make the system's frequency response perfectly flat and this is the canvas you work from now overlying the inverse of the Fletcher - Munson curves and programming the computer to hop from one to the other at the right volume. 
Now if the front end of the Class D amp were digital the appropriate electronics could be added. I think the company that is most likely to do this at a reasonable price would be Anthem. They have room control built in to some of their units so the basic computing power may be there.
Trinnov has it all except the programming for Dynamic Loudness. You can link your PC to the Trinnov and program target curves into memory so you could create inverse F-M curves and switch to them manually but the programming to do it automatically is not there yet.
Erik, yes, just way more sophisticated. You have to see the computer programming in action. The problem with the Tact system is that it is complicated and consumers had a lot of trouble using it correctly. Tact decided to go direct marketing which was a big mistake. They did not have a trained dealer network to help them out and eventually it all just crashed. The current crop of manufacturers learned from this and have simplified their systems but they also removed a lot of the functionality that made the Tact system so effective like the dynamic loudness and the most amazing bass management which has yet to be matched by anything I have seen. I can change high and low pass filters independently 1 Hz at a time and choose any slope for either filter independently from 6 dB to 80 dB per octave. I can do all this on the fly with my laptop on my lap. The computer also has total control over time and phasing between all the individual drivers and sets the delays automatically when the system is impulse tested. The improvement in sound quality is such that I now digitize my phono amp through a Benchmark ADC. May sound like heresy but there is no turning back. 

In my experience the best tone control is no tone control.

Ideally, the best tone control you can have is a properly calibrated room and system. If this is your situation, you'll have as close to an ideal response curve as is practical. No tone control necessary. Though, with some terrible recordings you may wish you had one. Unfortunately, that's our problem, and the recording engineer's fault. I've learned to live with that, but I understand the desire to make a bad recording sound good...
When I first started out, I used to think flat response curve was my goal, and couldn't figure out why it looked great on the screen and sounded like crap in the room. I didn't trust my hearing, as I hadn't yet learned to listen, and I hadn't learned to respect the 50/50 balance between measurements and listening as I do now. After 13 years of calibrating I'm 100% sure that a dead flat response curve is not even close to the holy grail. No room here to discuss what is ideal, but using DSP, EQ or tone controls to get as close to a flat response curve as possible is almost always a fool's errand.

I've been called in to "fix" many systems that were calibrated using Trinnov, Audyssey, and manufacturer's proprietary auto EQ systems including Krell and JL Audio. None of those systems approach the quality of sound you get from properly, physically, calibrating your system - the room's acoustically acceptable, the speakers and listening position are properly coupled to the room, all participants in the system are respecting and working synergistically with physics. Step 1. Always!

After that, DSP, EQ, and tone controls can be used like a pinch of salt - not a fistful or a backhoe full of salt - to knock the tops off the most egregious problems. That's it! No more! And no more than 5dB of attenuation...preferably no more than 2dB. If your setup requires that you mash the tone control or max out the DSP it's time to set everything at "0" and start over. Parametric EQ is best, with a "Q" of 0.7 being ideal, and only nudge what needs to be nudged. If you have a 20dB hump in your response curve at 32Hz, don't EQ it! Find out what the hell is causing that nightmare and fix it. It's likely a loose sheet of drywall or a floor resonance.

The more tone control or EQ you use the more mangled the phase becomes, and although it's hard to pickup on a meter, your ears and brain know that something's not right. This is a problem in the time domain which affects frequency. That's when your brain starts running its' natural hardware and software, trying to reconcile what it hears with what it knows that should sound like. Our own internal EQ. And that's when listener fatigue starts to kick in, and you may find that after 30 minutes or so you can't wipe that look off your face, you know the look that you get when you bite into a lemon. Not the look that most of us are after...

Go easy, and fix the problems at their source. Then, light on the tone control if necessary. And if you absolutely must, have a tone setting (+bass/-treble) for that rare occasion when you're listening to an 80's CD of Mike and the Mechanics. Good luck!

Not so audiophilenm, at least in the digital world. I was just like you until about 2000. I just played the music at whatever volume it sounded best but there are several factors that even the smartest audio person can not control for. If I measure any system, even set up by a master the frequency response measurements will look like the rocky mountains. The usual response is, "I didn't know it was that bad." Second, the two channels are never identical. I have seen them vary as much as 10 dB in spots. You can't know how this screws up your imaging until you hear a corrected system. Third is you have no way of managing you individual speakers in time. The sound from various divers is getting to you at different times at different phase angles. This is most critical for subwoofers but also can greatly effect imaging. I have never corrected someone's system (and these are died in the wool audiophiles) and had them think it made their systems sound worse. Their usual response is "I did not know it was that bad." So, until you have measured your own system and had a look at what it is doing then corrected it both in the time and frequency realms, you have no idea what your system can sound like. You are determining what the prevailing winds are by licking your finger and sticking it up in the air. 

Erik 

I agree that tone controls can make good sense and suit the needs or desires of many people.   And also I think the fear many audiophiles have of contaminating the purity of their signal are likely overblown.  Personally I’d never decry anyone’s choice to use tone controls or and EQ.

That said, I had a “transparent” digital eq in my rack for years and years (RDP-1).   I found that I essential found I never felt the need for it.  Once my speakers are dialed in nicely I tend to enjoy pretty much everything played through them.  Also, my CJ tube amps may be acting as a subtle tone control for my speakers.  If so, it’s a set-and-forget tone that I seem to like across the board :)

Further, I don’t really like the idea of fiddling with EQ per track.  That’s a more fidgety approach to music listening than I want to engage in.  Simply accepting the sound as it is leads me to focus on the music more.  (Though when I DO want to play with the sound I tend to do it via acoustics, whether it’s pulling a curtain on the side wall for a more or less spacious lively sound, putting a pillow behind my head or the like).

But that’s just an account of the approach I take.  Someone else may be the opposite where if, for instance, they find a track too shrill or lacking bass it would detract from their musical enjoyment so they activate tone controls.

Simple Path makes sense, EXCEPT, lack of controls leaves you with no control when adjustments would increase enjoyment.

Controls, done right, do nothing until desired/engaged. Optional Tone Control Bypass are liked by many.

Idealy: REMOTE VOLUME, and REMOTE BALANCE.

I see this as distinct/related/interactive parts

1. TONE controls

2. BALANCE Control

3. IMAGING Refinement (assuming decent imaging to begin with).

4. LOUDNESS: AUTOMATIC Low Volume Contour.
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1. TONE Control.

1a. Generally, I prefer listening to what artist/engineer put out. If I don’t like it, I am not likely to listen again. However, they certainly can be beneficial.

1b. Tone Controls, in some situations, can ’fix’ asymmetrical/difficult listening spaces, finding a general adjustment for the system.

1c. In the past, other systems, I’ve tried for ’perfection’ with advanced equalizers, pro microphones, ... it was a trap, back to basics please.
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2. BALANCE. System’s Balanced, Great.

2a. After that, I find for some tracks, tweaking balance a little can make a large improvement. Adjusting Imaging ’opens up’ all the instruments. It could be/occasionally is the engineering; your side wall; a system imbalance; a slightly weak tube ...

2b. Remote Balance is the easiest to make very slight and quick adjustment from the listening position.

2c. PHONO/TT setup (skip to 3 if no phono)

Anti-skate is critical for balance/imaging/groove/stylus wear.

Get it right, re-check it occassionally. (re-check tracking force occassionally also). I just learned a lot due to an arm with only one 2.5g weight.

https://forum.audiogon.com/discussions/fidelity-research-fr-54-tonearm-anti-skate

1. TT dial/hanging weight/rod with notches often are not perfect, or even close!

2. Stylus shape varies the effect of inward skate.

3. Smooth disk method works very well.

https://www.youtube.com/watch?v=M4VT-JsG_MM

4. Stylus with brush effects both downward force, AND inward/anti-skate. Using the smooth disk, leaving the brush DOWN while adjusting anti-skate proved successful.

5. I use my protractor/overhang/null point disc, it has enough smooth area

https://www.amazon.com/dp/B01MU6AD2E/ref=sspa_dk_hqp_detail_aax_0?spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExVTQzSDhOUThNS0EyJmVuY3J5cHRlZElkPUEwNjY1MDI1OVdUU0MzS0k5V1ZRJmVuY3J5cHRlZEFkSWQ9QTA5OTI2MjcyNTBJWEI0TkkwNzZBJndpZGdldE5hbWU9c3BfaHFwX3NoYXJlZCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1

6. I saw a video of someone using a blank CD. However, small diameter, be ready to catch the arm before it goes off the outside edge onto .....

7. Listening. This disc is my final confirmation/tweak.

Side 2, tracks 2 and 3: Three distinct guitars, and equal audience noise.

https://en.wikipedia.org/wiki/Friday_Night_in_San_Francisco

It is a very good example of 2a. above, how a slight tweak can make a large difference.

Eurythmics, Any: Annie Lennox/Dave’s Symetrical effects; Cassandra Wilson, Blue Light Till Dawn; Fontella Bass, New Look. Your favorite. Voices engineered to be dead center. (as long as they are not moving around the stage, i.e. live performances). Get them center, then, look a bit to the left: can you imagine them over there? Look a bit right, can you imagine ... tweak, dead on!

NOT Hot Sardines. (Great Jazz Band). Singer is OFF Center, leaving room for tap dancer, staying close to Piano. She may be right (saw her live at SOPAC), or left, Donna saw her live at Joe’s Pub, at this performance

https://smile.amazon.com/dp/B07NBPDG8P?tag=amz-mkt-chr-us-20&ascsubtag=1ba00-01000-org00-win10-other-smile-us000-pcomp-feature-scomp-wm-5&ref=aa_scomp_srdg2
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3. IMAGING.

3a. Balance as noted above.

3b. Boost favorite instrument, i.e. Jazz Bass; Piano; Sax/Trumpet/...; Voice. At decent volume, just change the engineer’s choices to suit. Just a slight touch, only for that track ...
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4. LOUDNESS: (AUTOMATIC Low Volume Contour). TRICKY
Essentially Bass Boost at Low Volumes. Good but hard to get right. Only needed if you listen at low volumes, i.e. while reading, or dreaded unwanted visitors arrive ...

4a. Mis-named, thus mis-understood, often improper implementation.
LOW BOOST; LOW VOL+; some name short enough to print on panel face.

4b. It does not know your speaker’s efficiency, so, how can it be automatically correct?

4c. Boosting/retaining bass, i.e. Jazz Bass, Low Piano notes, at low volume listening is much better than losing it.

4d. It should begin and work below your ’normal’ listening level, thus 2 volume controls are needed for proper implementation.

4e. Some old pre-amps/receivers had two volume controls.

First, Loudness Volume Control to un-engaged position. Then main volume for preferred listening volume. Then reduce volume using Loudness Volume Control, thereby progressively engaging LOW Volume Boost.

4f. Lacking that rare feature, you need to achieve the same arrangement with a pre-amp with LOUDNESS engaged when you want it.

First get a volume ’mix’ with Loudness OFF.

You need to find when your preamp’s loudness contour begins when ON. Then set pre-amp just above that, and use your amps volume to get your preferred volume, and volume increase, and back to ’normal’ when done listening.

Then, use the preamp to reduce volume, thus beginning the progressive bass boost. Also back to normal when done listening.

If you have two cartridges with different outputs, use the amp’s volume.

Loudness OFF. Amp half way up. Preamp half way up. Raise preamp, then lower preamp, until you hear bass weaken. Raise a bit, that’s where you want Loudness Boost to begin. Loudness ON: lower pre-amp volume: bass remains, not apparently boosted.

Amp volume control for louder, Preamp volume control for reduced, below normal volume listening.

Easy!