EQ: Generic proportional?

[Talesin]

Hi John.

I have some driver EQ settings intended for use in a DCX2496 that were provided to me by the designer of my speakers. The DCX2496 uses a proportional definition of Q, which you clearly describe in your REW EQ documentation:

Bandwidth = sqrt(gain)*centre frequency/Q

I've since moved past using an actual DCX2496 unit, and have for years been using a REW exported impulse response of the specified EQ convolved with my live music stream by my player. (Roon or HQ Player, depending on my mood.) The catch is that I'd really like to add low and high pass filters to my exported impulse response in addition to the parametric EQ, but the REW DCX2496 filter definition doesn't allow this even though the Behringer hardware itself supports it. (See section 4.3.3 of the manual. Note that I do not see high-shelf or low-shelf in the DCX manual, though you offer this in the REW DCX filter definition. Maybe this is just some label confusion?)

Even if the REW DCX definition adds the actual DCX LP and HP definitions, those are only good for either 6 dB/octave or 12 dB/octave, and I'd actually prefer more flexibility than that, at least 1 through 4 pole options. The only approach that I can think of at the moment is to generate a separate impulse response with the LP and HP definitions I want via the generic filter option, export it as a normalized impulse response WAV file, re-export my DCX2496 driver EQ impulse response as normalized WAV, and then find a 3rd party tool that can combine the 2 WAV files into a single new impulse response.

Is there some better way to accomplish this without leaving REW, especially as I don't currently have an IR merge tool on my Mac? Or could a modified DCX2496 EQ option be made that offers the LP and HP filters in a more flexible/extended (1st/2nd/3rd/4th order) form?

Thanks for any suggestions!

(Btw, apologies... I tried to provide a direct link to the DCX2496 manual, but the forum software viewed it as spam, so I unfortunately have to leave you to google it separately.)

 

[John Mulcahy]

I have added the crossover filters the DCX supports (Butterworth 6, 12, 18, 24, 48 dB/oct, Bessel 12, 24 dB/oct, Linkwitz-Riley 12, 24, 48 dB/oct). That will be in the next beta release. You could also use the StormAudio equaliser setting, which has Butterworth and LR crossover filters up to 8th order.

If you want to start with your existing DCX filter settings, export the corresponding filter IR, import that as an impulse response then apply whatever additional EQ you want with any equaliser that has the features you want and export the impulse using the "EQ filtered IR" option.

Edit: I checked the documentation from when the DCX was first implemented, at that time the EQ section definitely offered shelf filters rather than LP/HP (which makes sense, given the crossover filtering already covers LP/HP requirements). The manual still talks about a gain setting for the "LP" and "HP" filters that raises or lowers level, so I think they remain shelf filters and the manual is using the wrong terminology for them.

 

[jtalden]

Yes, the EQ in the DCX has low and high shelf at 6 or 12 dB/octave at the selected frequency and gain.