What happened to the loudness control?

Eldartford: What you wrote isn't exactly correct. Although few folks will turn their volume up to max, there are ocassions when that becomes neccessary. I have experiemented with amplifiers with sensitivities so low that my volume control was at max with some recordings.

But, the reason I stated 100% of the range is that the loudness control is a relative to the volume setting. By design, if it can't function properly over 100% of the range, the circuit is flawed by definition.

Secondly, all preamps have a dual knob loudness control if they have a bass control. Simply turn the bass up slightly to your preferece when you turn the volume down. At least you will get the proper amount of bass. Please understand the loudness control is simply nothing more than an attempt to eliminate one additional tone adjustment. It isn't much effort to tweak the bass control a smidge.

Lastly, the Fletcher Munson curves are an average, they aren't correct for all humans. Consequently, even if the loudness control followed the curves perfectly, it would still be wrong for many, if not most, of us.

Spatialking...Turning the volume all the way up is not using 100%of the range. In practice 50% of the range (eg: from 40% to 90% would be typical) and with a two knob loudness circuit tracking Fletcher-Munson very accurately over such a range is not a problem. Of course F-M is an average, but it is better than nothing. A bass control is NOT the same thing as Loudness, although people have to make do with it these days.

Eldarford: In the example I gave you, I used 100% of the volume control simply because there wasn't enough gain in the system. During that period, my volume control would be at max most of the time, not at 90% or any other setting.

Tell me how your loudness control compenstates for the roll off of your subwoofers? They certainly aren't flat nor do they have uniform output as the volume drops.

However, you have piqued my interest in loudness control circuits. I think I will revisit the current thinking of circuit topology and see if anything new has been done in the last few years.

Spatialking...If your volume control is always at the same setting, whether that is 100% or 60%, a Loudness control has no relevance. In this situation, if you don't like your sound, what you need is some kind of fixed equalization. Loudness controls are not intended to correct equipment/room frequency response problems, like the SW roll off that you mention. As to your suggestion that a SW efficiency (dB/watt) varies with SPL (watts), I have heard this suggestion before, but it is not true at all for my particular custom built subwoofer system. (I have actually made measurements to investigate this).

Eldarford: Really? You have consistent efficiency in your subs across the entire voltage input range? I would be most interested in your studies. Many, if not most, subs or speakers for that matter, have consistent efficiency across their entire voltage input range.

My comment above was spoken in the context of linearity, rather than efficiency. It seems in general these days, if your speakers efficiency is off across the input range, it is acceptable for the amplifier to make up for it. There is an arguement that consistent efficiency, as well as higher efficiency, results in better sound but I don't take a side on that one as I have heard bad and good systems at both extremes.

I am still very interested in seeing your test results. If you don't want to publish your results here, please email me directly.

Thanks,