Building a proper control room – final tweaks using EQ, primary diffusion & installation of a sub-woofer

Hi there and welcome back!

We are slowly nearing the end of this series.
Today we will have a look at what EQ correction can do as a final tool. Furthermore, after a little bit of research on the web, I decided to tune the bass region a little more by installing and tuning a subwoofer. Meanwhile I also installed a primary diffusor on the back wall of the control room to diffuse the reflections there. But let’s proceed step by step.

If you ever worked with REW you will have noticed that it provides a module to generate correction curves for different types of EQ. In a first step I decided to simply use an EQ plugin that I had at my disposal, DMG Audio Equilibrium. So I let REW calculate a “generic” EQ curve, fine tuned the settings a little bit. The following graph shows what REW came up with.

EQ_correction_REW

Calculated EQ correction curve (REW)

I then took these settings to Equilibrium and saved them. The only problem now was that I wanted this EQ to correct everything that is played back on my system, not just my DAW. A possible solution to that problem is to use a loop back on your audio interface (RME Raydat in my case), send that to some plugin container where you insert the EQ and then send the signal back to the monitor output of your interface. As a plugin container I am using AULab on Mac, but there are equally usable containers for Windows out there.

Now let’s look at a measurement of the EQ’d frequency response. What we see is that the EQ certainly makes a difference but probably not as much as one would have expected. Well, you know you can’t remove things like comb filtering, since that’s coming from first reflections. An EQ would only shift the frequency of this comb filtering, but wouldn’t remove it. Moreover, the settings in REW may have been a bit to restrictive as far as the number of bands and settings of bands goes. I will show you next time what a dedicated calibration software (Sonarworks Reference 3) can achieve here.

fg_eq_ohne_diff

Frequency response after EQ correction without sub

rt60_eq_ohne_diff

EDT after EQ correction without sub

What made a lot more difference for my control room was bringing in a sub woofer – the Presonus Temblor T10 in my case – and tune it such to improve the frequency response up to about 300Hz. This took at least 50 measurements to get it correctly. However, it was well worthwhile the hassle as you can see from the comparison measurements below.

fg_sub_vergleich

Comparison measurements with and without subwoofer – frequency response

The bass response has been tamed quite a lot and is much flatter now, with less highs and dips. Very nice. Taming the bass response is probably not what you would expect from a subwoofer, but this is how you should use subs actually. The thought behind it is, that you have a lot more freedom in moving the sub arround in the room, thus finding a position that has shows interference with walls as speakers that are positioned near the front wall. And you can even take care of the phase between sub and speakers and use that as a tool to smooth out the frequency response. That would even work better with a dual sub setup but that is out of my financial reach at the moment.

rt60_sub

EDT after installing and tuning the subwoofer

etc_subdiff

ETC diagram after installing and tuning the subwoofer

waterfall_subdiff

Waterfall diagram after installing and tuning the subwoofer

What we see from the ETC diagram is, that there are still reflections on the table that we should care about for the sake of image clarity. So I  decided to rearrange my desk by angling it’s surface to reflect away from the listening sweet spot and move from the Qcon control surfaces to a touch based setup. More on this desk setup as well as a closer look on Sonarworks Reference and the according comparison measurements will be the topic of next weeks post.

See you then and take care,
Markus

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One thought on “Building a proper control room – final tweaks using EQ, primary diffusion & installation of a sub-woofer

  1. Pingback: Building a proper control room – outline and prerequisites | orthogonalrecords

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