pro-audio products

resonance equalizer

product review

by Ben Feggans

Since the very early days of tape transfer and vinyl cutting, the humble equalizer is still one of the most powerful tone shaping tools a Mastering Engineer has at their disposal. The search for the ultimate synergy of sound and functionality is a decision made early in ones career, and the right choice is often a lifetime investment. Indeed, here we are in 2012 and the Sontec 430 series equalizer from the late 70s is still in use by many top Mastering Engineers. Yet now there are a few other contenders clipping at its heels, including one from New Zealand that I have front of me, the Buzz Audio REQ 2.2 Resonance Mastering Equalizer.


Unpacking the reassuringly heavy Buzz EQ reveals a powder coated black metal case with side braces connecting the front and rear panels. From its solid aluminium face plate with sloping recessed holes, softly lit function buttons, military grade chassis and Elma switches, you can tell that the hardware has been impeccably made and is going to last a long time. The internal construction is modular for easy serviceability.

Tech Specs

Rather than doing a typical magazine review with focuses on the bleeding obvious that you could figure out by simply looking at the picture, I'm going to focus more on the sound and functionality of this beast. It's big, it's powerful, and it gets bloody hot!

For the more 'tech' orientated, the Buzz REQ uses a completely passive inductor/capacitor/resistor (LCR) circuit for equalization with an active Class A gain make up stage. Each channel has a saturation control, followed by a high pass filter, then four bands of parametric equalisation connected in series. The high and low band may be switched to bell or shelving. Generally this type of passive circuit suffers from a limited amount of bandwidth options, but the Buzz solves this problem by using an ingenious CMOS switching network to give a wide variety of sharp and broad bell curves required for mastering. These range from 0.25 of an octave to 2 octaves. For shelving, these curves behave more like a resonant filter when using a sharp Q, or a standard slope using a broad Q value. The mid bands can be switched between two frequency ranges as indicated on the front panel, which is handy. Each band may be bypassed independently by an illuminated toggle button.

The high pass filter has carefully selected frequencies designed for mastering, and the slope of the HPF varies from 12dB/oct at 25Hz setting to about 7dB per octave at 70Hz. The saturation control has settings ranging from 1-6 that change the low frequency response of the REQ as well as introducing low frequency harmonics generated by the steel audio transformer. Confusingly the 6th position gives the least amount of low frequency bump, and the 1st position give the most, although the distortion is the least on the 1st position. (All curves are available in the manual).

Noise floor is a very respectable -110dB below the +25dBu input level, and the frequency response is quoted as 5Hz to 125kHz (+0.2/-3dB).

In Use

So, off with the gloves and ready to dig in. The Buzz REQ was tested in two different mastering studios, the first being Studios 301 in Sydney, which has the Sontec 482, GML 9500 and EMI TG 12412 EQ for comparison. The second studio was King Willy's Sound (William Bowden), one of Australia's most experienced Mastering Engineers, with a studio that includes the Fairman TMEQ, Manley Massive Passive and modified Focusrite Blue 230.

After connecting and powering up at King Willy's, first impressions were that the Buzz REQ definitely has a sound and character that is unique. I would describe the overall tone as being rich, smooth and powerful. You can boost frequencies more than you may normally do without sounding unpleasant, especially in the midrange and top end. It was not uncommon to boost 3dB-6dB and still sound natural. It has a softer tone than either a new Sontec 482 or GML 9500, but is not as coloured as the passive Fairman TMEQ. This comes at the expense of not having the razor sharp accuracy that the GML processes. Surprisingly the Massive Passive, which has the most similarities to the Buzz in terms of being a passive equalizer, had quite a different sonic character and came up very well on the same material, including some soul and dub music. Although I'm certain that Willy's Massivo sounds different to the one that I used to own and this is always a minor irritation! It took some time to get the Buzz curves interacting in a similar manner to other EQs that we were used to, and this made quick comparisons difficult. I kept asking myself 'What sort of personality does the Buzz have, and what style of music or mix does it work best on?'

At Studios 301 the Buzz REQ was more at home. I brought up a jazz session that had been well recorded and mixed entirely ITB. It just required some low mid cut, nice vocal presence and top end- and the Buzz fit the bill perfectly. I used the saturation control on 5 to give the low end more drive and thicken up the vocals. The input level changes this effect so it's worth experimenting.

I then used the Buzz REQ on a couple of deep house tracks. They also required some analogue character to give the production a more organic feel, and fortunately needed some 60Hz low end boost (rare these days), which the Buzz has in spades. Using a higher Q value shelf it is even possible to give a boost or cut with a resonant peak much like a filter. However, I'm not quite convinced on the bottom end, as it appears to soften the transients by just inserting it. In fact, the Buzz does have a slight softening character that may or may not sit with what you are attempting to do. You may notice this on the top end of snares as well. Transients are king when mastering, and although the Buzz has a beautiful tone, it may be at the expense of some transient impact. Ideally you would be using the Buzz REQ with a cleaner active equalizer or plug-ins, so I don't see this as a major problem as they would not possess the smoother organic character of the Buzz.


There were a couple of minor irritations when using the Buzz REQ. The 'System A and System B' insert or bypass controls are spaced apart making it difficult to press them simultaneously. This would not be an issue with a mastering insert router. [These switches can now be linked in later versions] The Elma Frequency and Q switches had a lovely solid feel, however the Elma boost/cut stepped switches are very light in use compared to other EQs and perhaps the less expensive Palazzo switches may be better suited.

I would have preferred the high pass filter to be at the beginning of the chain, before the equaliser and transformer saturation. Having the high pass filter after the saturation means that if you add some transformer low end the high pass filter takes that low end away. It also means that you need another EQ before the Buzz in order to do the old 'scoop out the low end then add some subs back in' trick using the transformer. I'm sure these changes could be accommodated on request.[Correction, the high pass filter is at the beginning of the chain]

The Verdict

As you may have already guessed I haven't had enough time to fully understand the depths of this complex beast. What Tim has created is an EQ like no other; it stands shoulder to shoulder with the best mastering EQs on the planet, yet processes a unique colour that takes time to assess, especially if you are used to the sound of other mastering EQs.

In the end it comes down to what works in your room, your chain, and the type of sound that you prefer. Is the Buzz REQ a Sontec beater? In my opinion no, it's a different equalizer. There is something special about those Sontec op-amps…until they fail. Keep in mind that depending on its age and condition the older Sontec 430 series generally have a softer sound compared to the newer series, and many people that have compared the Buzz to an older Sontec prefer the sound of the Buzz.

Does it replace a Massive Passive? Once again, I don't think so. The only way to properly access the Buzz is on its own merits. The strength of the Buzz REQ for me was definitely more in the top end and midrange, much like the Massive Passive.

For a mastering equaliser of this calibre specified with Elma switches, the price is very completive and support exceptional. For many busy Mastering Engineers keen for a return on their investment this may just be the deal breaker. It's a solid work horse that you and your clients will enjoy.
[2012 Ben is a mastering engineer at Studio 301]

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