Curve matching: Waves Renaissance EQ, emo-Q4 and the TB Equalizer

TLDR: the Waves EMO-Q4 has the same resonant shelves and bell boosts as Renaissance EQ, but not the same cutting behaviour. The filters aren’t adjustable and EMO-Q4 still uses more CPU. It has a better GUI but everything else is worse. Toneboosters equalizer has very similar curves to RenEQ and may be a better option for those looking for a bigger GUI.

In the last year I’ve moved my music-making to a Windows 10 dual-boot setup (I’m still using Linux for most other things.) This was mostly motivated by a sense that I wasn’t getting the low-latency performance that my i7 CPU should be capable of when running nice audio effects. Much as I’d prefer not to support the Windows monopoly, I’m really excited about some of the music production tools that have been released in the past few years by developers like Klanghelm and Tokyo Dawn. Apple consumer hardware remaining impractical (more USB ports and HDD bays please!), it seems like Win 10 is the least terrible option for this task at the current time. (It’s pretty awful though. Your computer/OS is a professional appliance and you should not have to dedicate time to turning off advertising.)

Deep breath

So, this article. One “benefit” of using a proprietary operating system is the chance to take a few more risks with DRM-encumbered software. Some of the older “industry-standard” stuff is now available at fairly reasonable prices, so I took a punt on a few things including Waves Gold.

Waves digital EQs

Waves Gold includes quite a few equalizer (EQ) plug-ins. These are used to re-balance the frequency content of audio. EQ is probably the single most important tool in the mixing process after basic level control, so producers tend to a) have lots of equalizers and b) have strong opinions about them. “Clean” digital EQ is actually quite well-defined mathematically so in principle there shouldn’t be much of a “quality” difference between digital EQs. What distinguishes them is the curves, generally controlled with frequency, gain and “Q” (the narrowness of the filter). How easy is it to make the frequency response graph that you want?

Waves have been making digital equalizers for a long time. Did you know they made Q10, the first digital EQ plugin, in 1993? You do if you’ve read the Renaissance EQ manual, which is a recommended read for computer music nerds. The manual makes it clear that a lot of thought went into the design of its slopes. There are two key features that remain somewhat distinctive; the “resonant shelf filters” which add a small cut near a boost or vice-versa, and the “asymmetric bells” which have narrower cuts than boosts.

Here’s the thing about Renaissance EQ (RenEQ); people really like it. It’s pretty old, but if you poke around online there’s not a lot of criticism, and plenty of people seem to be using it over newer and shinier alternatives. The main downside is the tiny, dated GUI. Waves Gold also comes with a much newer EQ called “emo Q4”, developed for live sound applications. It has a big pretty GUI, and there’s barely any info about it online; not many technical details, not much discussion. Given that “RenEQ with a better GUI” should be an absolute hit, it seems worth investigating those curves…


The screenshot above shows four plug-ins. On the left is the emo-Q4 and above is the RenEq. On the right is a noise generator, and at the bottom is a spectrum analyser (SPAN). Each EQ is working on the left or right channel only (REAPER makes this kind of thing really easy!) and SPAN is set up to show two spectra, one for each side. You can only see one here, because the curves match exactly! I’m using two resonant shelves, a bell boost and the high-pass filter. But there’s a trick – the emo-Q4 filter is not adjustable, so I had to adjust the RenEQ filter to match. The emo-Q4 does have a wider parameter range on the shelf filters though, so it can make some curves that RenEQ can’t.

Let’s look at an 8dB bell cut:


Now we see two curves in the analyzer! The RenEQ is narrower on cut. I can actually adjust the emo-Q4 Q to match it, from 0.80 to about 1.96. This Q is no longer correct if we change the gain, so the RenEQ cut width is gain-dependent. This makes a big difference to the workflow and so won’t help win over RenEQ users.

Finally, some quick and unscientific testing with REAPER’s performance meter suggests that the emo-Q4 has a slightly higher CPU usage, although both are pretty low at less than 0.1 CPU%. Final verdict; I like the layout of the emo-Q4 and the shelves are great, but some different design decisions were made from the popular RenEQ.

Toneboosters EQ

As an afterthought, I pulled up the demo version of the very affordable Toneboosters EQ. This has quite a few different bell types. The “digital bell 2” and low/high “shelf 2” options seem to follow some of the philosophy from the RenEQ manual so I thought they might be worth a look!


With a slight reduction in the Q value, I was able to get a great match from this low shelf and high-mids cut using identical frequency and gain values. The narrow default cut value was promising so I tried boosting…


Boom! The gain/Q relationship seems to be very close.

Closing remarks

There are other factors in EQ choice than the curves and gain/Q behaviour. The Toneboosters EQ has a bigger graph than RenEQ and the text is more readable; however personally I prefer being able to see all the parameters at once rather than the one-band-at-a-time approach of TB-EQ, ReaEQ or TDR Nova. I also find the overlapping coloured bands display of TB-EQ a bit distracting even if it is pretty. There are other features to consider; TB-EQ’s “gain effect %” parameter makes it very appealing for automating mid-mix. My current workhorse for mixing is the SlickEQ GE, which demands more CPU but has a great interface and some pleasant saturation options.

I mostly wrote this up because I was frustrated by the lack of online discussion of emo-Q4. If you’ve got something useful to say about any of these EQs, do use the comments section below!


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