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[DoubtingThomas]

The Parametric Equalizer description for a "High-Shelf" filter is confusing to me.  

On one part it says

"boost or cut all frequencies that are higher than a certain frequency"

indicating that the set frequency is the starting point for the adjustment.  Then later it says

"The frequency is the exact middle of the shelf's rise or fall."

which really makes no sense (to me) at all considering the prior statement, or what I'd consider a "high-shelf" adjustment to do.

Is the "frequency" setting for the "high-shelf" filter the starting point or the exact middle of the effect?

High-Shelf

Allows you to boost or cut all frequencies that are higher than a certain frequency.  The boost or cut will increase as the frequency increases at different rates depending on the Q (higher is steeper, lower is more gradual).  The gain setting is how much total boost (or cut) there will be at the top (or bottom) of the shelf.  The frequency is the exact middle of the shelf's rise or fall.  The channel setting lets you specify which channels are affected.  A Low-Shelf is the opposite of a High-shelf, it boosts or cuts all frequencies below a certain frequency.  Here's a picture illustrating the response of two different shelving filters http://en.wikipedia.org/wiki/File:Shelving-eq.svg.  I don't know the exact parameters they used to create those examples, but the red trace in the illustration is probably a -3dB low shelf set at 150Hz with a Q of .5.

[mwillems]

The Parametric Equalizer description for a "High-Shelf" filter is confusing to me.  

On one part it says

"boost or cut all frequencies that are higher than a certain frequency"

indicating that the set frequency is the starting point for the adjustment.  Then later it says

"The frequency is the exact middle of the shelf's rise or fall."

which really makes no sense (to me) at all considering the prior statement, or what I'd consider a "high-shelf" adjustment to do.

Is the "frequency" setting for the "high-shelf" filter the starting point or the exact middle of the effect?

I can confirm that the frequency is the exact middle of the rise; I wrote the quoted description, and I should probably clarify that the "certain frequency" I meant is not the "frequency" parameter.  It's just hard to describe that the set frequency is the middle of the transition band until you explain what the filter actually does, if that makes sense.

Because the bandwidth required for a shelf to transition completely depends on the height of the rise and the Q, there's no "corner" frequency like with a high or low pass filter.  The frequency you set in MC is the middle of the transition band (3dB of rise for a 6dB shelf, 1dB rise for a 2dB shelf, etc.).  See this thread for some measurements confirming that point: http://yabb.jriver.com/interact/index.php?topic=86791

[DoubtingThomas]

With a shelf... what is the middle?  To know the middle assumes a top frequency.  What is top?

I'm trying to simulate a treble control.  With control over the starting freq and rise.

Is this the right control to use?

[mwillems]

Yes a high shelf is what you want to use to simulate a treble tone control; most traditional treble or bass tone control knobs are just very low Q shelving filters.

Have a look at these graphs of two relatively high Q shelving filters: https://en.wikipedia.org/wiki/File:Shelving-eq.svg, look particularly at the blue trace on that graph (which is a high shelf filter). You can see that the graph of the shelf response can be divided into three "areas": 1) the frequencies below which the shelf has no effect (from DC to about 1KHz), 2) the transition band where the shelf adds increasing amounts of boost (between 1KHz and about 12KHz), and 3) the area above the transition band where no additional boost is added (from 12KHz on up).  The frequency in JRiver is the exact middle of the transition band (3.5KHz-ish in this example).  The effective top and bottom of a given shelf's transition band will vary depending on the Q and, to some extent, the amount of boost or cut being applied.

Now, have a look at figure three of this article by Rod Elliot; it shows the frequency response of a conventional bass and treble tone control circuit: http://sound.westhost.com/project94.htm . The graphic on Rod's article requires a little explanation. It shows both a bass and a treble tone control, because we're just talking about treble control, just focus on the right-hand side of Rod's graph (i.e. above 800Hz). The different colored lines represent differing amounts of boost (as though you were turning the tone control knob up), but the Q for each line is the same.

With that context, you can see that the treble tone control circuit is just a very gradual shelf (meaning it has a low Q).  It starts rising around 800Hz, and it only finishes it's transition outside of the audio band entirely around 50KHz.  The tone control curve has the same shape as the shelves illustrated on the wiki, but because of the low Q it takes many more octaves to finish its rise. For that reason, if you were looking at a graph of the tone control response that only showed the response between 800Hz and 20KHz, you might get the impression that the response just never stopped rising, but that's not so.

To approximate Rod Elliot's tone control, I'd probably set the JRiver frequency to 4KHz or 5KHz, set the Q pretty low to start (maybe .25 or .3) and then experiment with dB.  You can get a rough idea of what it's doing by turning off all other DSP, and then watching the DSP analyzer while playing JRiver's built in pink noise test tones (but keep in mind that that will be a very rough approximation, modelling software is a better bet to really see what's going on).  

It can be hard to sort out what's happening with PEQ because there's no native graphical representation of what's going on, and I've been sporadically bugging the devs about it for a little while, but I think it's pretty far down on the to do list.  Now that DSP presets can be saved (and presumably parsed where-ever they are) I might just break down and write (or port) a graphing VST plugin (but it won't be anytime soon).