To expand a bit on the original topic of DRC comparison, recently I've also had a chance to experiment with the WiiM Room Correction (RC) feature.
First I have to say that I'm absolutely impressed that WiiM is continuously developing and enhancing these kind of advanced functions, and even introducing them retroactively to older products!
The SW support side seems quite incredible too - e.g. I found a bug with RC function early in my tests, reported it to WiiM, and they delivered a fix in a couple of weeks. Amazing!
How it works
Back to topic, here's how WiiM RC works in principle:
- You open the WiiM Home App, select the setting for the WiiM device in question and choose "Room Correction"
- You have the option of editing some basic settings like:
- target curve,
- frequency range where correction is calculated and applied,
- max gain and Q,
- smoothing level,
- whether to correct the subwoofer range (i.e. below the sub crossover frequency) or only above it,
- whether a single or multiple sweeps are used to measure the in-room response,
- and recently also the option to include a mic calibration file for external microphones (i.e. not available if you use your built-in phone mic).
- You then start the process by playing a test sound through the speakers, after which you have to option to select "stereo" or "individual channel" correction - basically whether the same PEQ filters are calculated for and applied to both channels or each channel gets their own PEQ filters. There is a limitation at the moment where you can only use the "stereo" correction option if WiiM Bass Management is also enabled.
- You then point the phone mic (or external USB mic, if you have one) towards the loudspeakers and record some sweeps.
- WiiM RC then calculated the correction PEQ filters, and lets you save them with a custom name (so you can have multiple ones).
- If needed, you can switch between RC-calculated PEQ presets and even edit the filters manually in the EQ settings view in the app.
More information on the process (with pictures) can be found in WiiM support pages.
The results after WiiM RC can absolutely be good, but as always rely a lot on which settings you choose, and how 'flat' your microphone response is.
The default WiiM RC settings are OK but IMHO not ideal, and some IMHO important options are missing (more on this at the end of the post).
In addition, many phone built-in mics will surely have a terrible frequency response, potentially degrading the response - e.g. my Samsung S23+ is pretty bad.
Testing RC
Let me give an example of how using a different mic influences the response after WiiM Room Correction:
Red dotted line shows the uncorrected response. Note that this is an ultra-nearfield scenario so the target response should be almost flat.
The
orange dashed line represents the response after WiiM RC when the built-in S23+ mic is used to measure. You can see the lows are boosted a bit.
The
blue solid line represents the response after WiiM RC when an external USB-C earbud microphone is used to measure. You can see the lows are boosted by a lot - result of the microphone significant response roll-off in the lows.
The best-looking response (
green solid line) is what I got when I used a calibration file with the same USB-C earbud microphone.
You can read how I calibrated the earbud microphone against a Cross-Spectrum Labs calibrated Dayton Audio EMM-6 measurement microphone in
my thread on the WiiM Forum.
These were the RC settings I used in the app:
And this is how the correction results looks in the app:
What is missing?
While WiiM RC in its current state works pretty well, I do see a lot of room for improvement in the future.
I summarized these in the
related WiiM Forum thread, but I'd like to mention them here for completeness:
- A pre-gain control is missing, which could be used to reduce the level going into EQ to avoid digital clipping; especially when positive-gain EQ filters are used!
- Individual channel room correction when bass management is enabled is missing.
- At the moment a single control defines both maximum positive and negative PEQ gain. Separate controls for the positive (boost) and the negative (cut) gain range of room correction filters would allow deep cut filters, but not strong boosts - which saves amplifier headroom and avoids temporal ringing.
- The capability to import custom correction target curves is missing. At the moment there are only three predefined curves are available (B&K, Harman, Flat).
- Perhaps the built-in microphone of the WiiM Voice Remote could be used in the Room Correction feature. This might be an easy way to more consistent correction results for many users without access to calibrated measurement microphones.
- Variable smoothing option is missing. This would reduce the risk of over-correction in mid and high frequencies, while still allowing precise correction in low frequencies.
- At the moment only sweep measurements with simple smoothing are supported, which is also not the best choice for corrections at mid and high frequencies. I'd like to see the option to use MMM instead since MMM gives much more consistent results between attempts and averages out a lot of the perceptually irrelevant reflections.
- The default RC setting values could IMHO be improved to provide better correction for most users out of the box. Mainly to use a downward sloping target curve (B&K is fine), limit the correction range to below ~500Hz, only allow PEQ cuts (no boosts), and use some kind of variable smoothing.
Note that these only apply if you use WiiM automated Room Correction. You can still use PC with REW and a calibrated measurement microphone to manually measure your system, calculate there the PEQ parameter values against your preferred target curve in REW, and manually type these PEQ parameters in the WiiM PEQ function. So there is a way around the current RC limitations.
While not strictly part of RC, IMO the following features which are missing today would take WiiM RC a step further:
- Simple tone control (individual treble-bass control, or a single "slope" control) to easily tune overall system tonality to taste (post-RC).
- REW PEQ setting file import function.
- A way to backup and restore configuration (including RC and EQ settings).
- An automated loudspeaker correction function which could directly import PEQ presets based on anechoic loudspeaker measurements from e.g. the amazing spinorama.org maintained by @pierre. I guess something along the lines of AutoEQ app functionality for headphones.
(link to related thread on the WiiM forum)
Summary
All in all I have to say I'm quite happy with how WiiM RC works, especially given that it was added for free after many of the WiiM products were already in the market for quite a while. At the moment I'm still using my own REW generated correction filters loaded in WiiM EQ, but I can see myself moving to it if a few of the missing features are added in the future.
Hope this will be interesting to some!