Topic: PEQ "Q" implementation / REW / multisuboptimizer

Hi,

Several questions to the RME team:
- Can you elaborate which "Q" implementation you are using in TotalMix PEQ (UFX II) and ADI-2 Pro PEQ? I just learned that there are various definitions of Q, and I would like to select the correct one. Relevant for "REW" EQ simulation and especially for the software "multisub optimizer" I am using for setting up my subwoofers using the new Room EQ functionality.

- Are there any plans to work with the REW author bringing your devices into the REW EQ/DSP list of preselectable  devices to automatically set the limits for available PEQs?

Thanks, Mark

BR Mark
ADI-2 Pro FS R BE / UFX II
Neumann KH120, KH310, KH810 / Audeze LCD-X

2 (edited by Mark_S 2024-06-12 19:49:36)

Re: PEQ "Q" implementation / REW / multisuboptimizer

Just did a quick measurement with my ADI-2 Pro using a PEQ a 100Hz, -10dB cut, Q=3, and it seems that "Q" is implemented per "RBJ" definition (see https://www.andyc.diy-audio-engineering … index.html).

@MC may kindly confirm that this implementation of "Q" is used as well in TotalMix EQ and Room EQ for all Firefaces.

I would like to attach screenshots of my measurement, however, do not know how to do this.

BR Mark
ADI-2 Pro FS R BE / UFX II
Neumann KH120, KH310, KH810 / Audeze LCD-X

3 (edited by ramses 2024-06-12 12:24:01)

Re: PEQ "Q" implementation / REW / multisuboptimizer

Mark_S wrote:

I would like to attached screenshots of my measurement, however, do not know how to do this.

You can see, that this forum doesn't allow for uploading content, but has img tags.
So the usual thing, place a picture to a cloud and link the URL.

See my blog for background and details:
https://www.tonstudio-forum.de/blog/Ent … rum-EN-DE/

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13

4 (edited by Mark_S 2024-06-13 17:56:51)

Re: PEQ "Q" implementation / REW / multisuboptimizer

Hi Ramses,

Thank you for your advise, will try to link external pictures:

ADI-2 PRO, PEQ 100Hz, -10dB, Q=3:
https://www.dropbox.com/scl/fi/6oc5kg5o … p&dl=0

Multisuboptimizer, PEQ 100Hz, -10dB, Q=3 (red = "RBJ" setting, blue = "classic" setting):
https://www.dropbox.com/scl/fi/5ex586lx … k&dl=0

It seems that "RBJ" is also referred to as "proportional Q" while "classic" is referred to as "constant Q". However, I am no expert in this field.

It is important knowing that a PEQ with exactly the same settings can lead to a different result depending on the specific hardware or software implementation. Therefore, I would appreciate if RME would provide more detailed background information on their specific implementation, e.g., in the technical appendix of their manuals.

Thanks, Mark

BR Mark
ADI-2 Pro FS R BE / UFX II
Neumann KH120, KH310, KH810 / Audeze LCD-X

5

Re: PEQ "Q" implementation / REW / multisuboptimizer

Soirry for the late reply. This topic needs some solid documentation and we will provide it. The PEQ is proportional (or variable) Q, where Q is defined at 6 dB gain. The amount of variable Q seems to match very well with other popular EQs, for example the Oratory settings give the exact curve published. But there seems to be no definition and no further explanation or even mentioning of the amount of variability with Q, so this needs some more investigation.

Regards
Matthias Carstens
RME

6 (edited by Mark_S 2024-06-15 16:23:55)

Re: PEQ "Q" implementation / REW / multisuboptimizer

Thanks for acknowledging that this is an important information for your users. Especially now, with implementing the fantastic RoomEQ which lets users try more complex headphone EQ (you mentioned oratory) or measuring based and computer optimized EQ curves (REW EQ preview and EQ optimizer, multisuboptimizer etc.).

Looking forward to find this info in one of your future manuals :-)

BR Mark
ADI-2 Pro FS R BE / UFX II
Neumann KH120, KH310, KH810 / Audeze LCD-X

7

Re: PEQ "Q" implementation / REW / multisuboptimizer

It's more simple than I thought, just got confused by the Q definition. We indeed use the most popular Variable-Q EQ, based on the EQ cookbook recipe of Robert Bristow-Johnson, as many others do as well, so will be compatible to most.

What confused me first was the definition of Q as '50% gain' in combination with 6 dB (50% is -6 dB...). The meaning here is that the bandwidth is measured at half of that value. So if you set the EQ to +6 dB, you would measure bandwidth at +3 dB points (only here it matches the classic way of measuring bandwidth aka -3 dB points). With +9 dB gain at +4.5 dB, and with +12 dB at +6 dB. Etc.

The popular RBJ EQ works much more 'musical' and audibly better than the classic, gyrator based EQs that were very popular due to their low price. Those have a very wide bandwidth at lower gains, influencing a far too broad range. The opposite could be said from so called constant Q EQs, which influence a much too narrow area when using gains below +6 dB.

The RBJ version reminds me of an older Electro Voice EQ mode called 'Constant Range' which also worked in-between classic variable Q and constant Q, by keeping the influenced area independent from the gain setting. They managed to do this with clever analog circuitry, but the name and the EQ vanished, and even Google will not easily find it.

Back to RME - our PEQ looks like this:

https://www.archiv.rme-audio.de/images/peq_q1.png

Note that the Q values in that pic were taken at -3 dB points, the 'classic' way, which results in a higher value with higher gain. Using the RBJ way to determine bandwidth Q will be 1 for any gain.

Regards
Matthias Carstens
RME

Re: PEQ "Q" implementation / REW / multisuboptimizer

That should answer all questions. Thank you!

I guess the implementation is identical for the ADI-2 Pro line as well?

BR Mark
ADI-2 Pro FS R BE / UFX II
Neumann KH120, KH310, KH810 / Audeze LCD-X

9

Re: PEQ "Q" implementation / REW / multisuboptimizer

All our units.

Regards
Matthias Carstens
RME