This is the sentence where we make some stupid snake joke, or worse, a juvenile double entendre. Moving on, this is a cool new 500-Series bus compressor. Last year, Serpent Audio released the SB4000 compressor as a DIY project. Response was positive, but the designer wanted to enhance features and launch it in the market. The SB4001 is Serpent's first commercial offering.

Although stuffed into a double-wide 500-Series format, the SB4001's functionality surpasses the original SB4000's. To provide a reference, the unit's heritage is the SSL 4000 G Series bus compressor. But that's just a starting point. Compression is handled via quad VCAs. There are six ratio settings; ten attack times; a sidechain filter with several settings; fixed and variable release; wet/dry parallel blend; a front-panel sidechain input; and a harmonic enhancement feature called Grind.

As could be expected, we started using the SB4001 on bus compression duties. Restricting ourselves to settings (ratio, attack, release) found on the classic SSL, we found that the SB4001 does indeed sound similar to that genre of dynamics processor. That's fine. But to be honest - so what? How many SL 4000-based units are already available? We wanted to know what, if anything, makes this unit special. At that point, it was just a serviceable clone.

Obviously, the first place to tweak is the internal sidechain filter. Six settings - off; 60, 90, and 120 Hz high-pass; Boost; Slope - affect the signal that triggers compression. Slope adds a linear boost/cut with a crossover around 1 kHz to the sidechain. Meanwhile, Boost provides a high-shelf boost at 1 kHz and a gentle 60 Hz roll-off to the sidechain. Essentially, these make the compressor circuit more sensitive to highs and less to lows, with Boost resulting in more responsiveness to mids and Slope to highs. On a drum bus, for example, this means the kick drum isn't pulling down the entire signal. You get more smack with less pumping. Using the high-pass settings (our favorite being 120 Hz), low-end denizens such as kick, bass, and synth are also less likely to trigger the compressor. Of course, this depends on application, but this is a setting we often have engaged.

Moving to the release adjustments, the choices are: A1, which uses the same auto-release timings as the original SSL; A2, which is faster; and variable ranging from 0.1-1.2 seconds. We found that auto-release worked well for some bus applications. But on other things, especially individual instruments, we preferred the variable option. You don't want to be handcuffed by preset release times. Continuing with drum tests, the Blend knob is something we foresee will be used often. Our opinion is that parallel compression done inside a unit seems to manage phase cleaner than two tracks in a workstation. Also, having a blend knob will help you get sounds faster, and you don't have to worry about plug-in phase smearing. Sometimes a ten percent blend is all that's needed to thicken a track without sacrificing the dynamics. We found the Grind button to be totally happening on drums. In particular, snare drums go from being snappy to hitting you in the stomach with a cinder block. Talk about stepping up your game. Grind gave the kick drum more chest-moving impact. We think most people will leave this button engaged on drums.

So, after a week of using the SB4001, our conclusion is that it is an affordable SSL-type compressor, with similar sound, but better features. We were going to write a calm but generally positive review and leave it at that. That's when we had a wonderful accident.

Since the SB4001 is a 500-Series unit, it was installed in our API Lunchbox (no surprise) next to some preamps we often use. Dave was doing a vocal session, and he decided to patch in the SB4001 instead of his standard Empirical Labs Distressor (Tape Op #32) or 1176 choice. Using the variable release set to the longest time, we heard no pumping. We tried to make it pump. No pumping. At one point we started to check our patching to see if the unit was connected! We could hear the volume reducing, but it didn't sound like a typical compressor. When pressed, we couldn't name another box that sounds like the SB4001 does on vocals. We know many people fear tracking with compression, but this unit will make you rethink that position. If you have a singer who does not work the mic correctly, using a 6:1 ratio, longest release, and setting attack and blend to taste, you can print a vocal take that will be much easier to use come mix time. Speaking of vocals, the SB4001 can make a great de-esser. Plugging a standard TRS cable in the front jack and hooking up an external EQ will allow you to target those moments of sibilance and duck them. I don't know of any other 500-Series compressor that offers that connectivity.

Finally, we tried the SB4001 on acoustic guitar - that is to say, a featured acoustic, not those strum-stabs that play on the chorus. It's really important to be transparent or else your recording will sound like an amateur joke. Setting the threshold to grab only the top transients (a buzz cut, if you will), we were able to get more control, without approaching that block-of-cheese compressed sound. For fun, we depressed the Grind button, and it gave the guitar a woody thickness that fell short of boominess. It was like changing the mic or mic preamp. Not always the best choice for acoustic, but it was nice to have the option. From using other SSL- style compressors, I would have never tried this, but it goes to show that stereotypes about gear (and people) are often wrong. You've got to try things that don't seem right at face value.

Rather than negatives, we have a list of usage notes regarding the SB4001. First, when sliding the SB4001 into your Lunchbox, extra care is needed. The double-wide unit is double-bladed, and you need to make sure both blades sit firmly in the backplane. We used a flashlight in the air vents to make certain we were hitting home. In use, the detented controls require a good bit of force to move. The lack of front-panel real-estate necessitated by the 500-Series format means pots are placed closer together than on a 19'' rack unit. Consequently, it's easy to accidentally nudge the variable knobs when adjusting the detented ones. The other thing to be mindful of relates to I/O set up. The SB4001 works stereo or mono (left channel only) - but not in dual mono (independent of one another).

All units are made in America, and feature a hand-made thru hole audio path. Engineers of means should consider multiple units, because you'll want these on different buses. And at this price point, that's not an unreasonable suggestion.

If this were only a bus compressor, the Blend, Grind, and variable release functions would be worth the price of admission. But after trying it on individual instruments, and in particular on vocals, we highly recommend the SB4001. We've used some killer compressors that have similar features, including the RND Portico 5043 (Tape Op #59), Elysia Alpha, and Buzz Audio Potion, but we've yet to see so much at this price point. Of course, you have to own a 500-Series rack with two available spaces, but for this flexibility, that's a fair trade. Now, we hope a standard rack-unit version of this guy comes out soon, because the mastering engineers are going to be all over that one. ($1099 introductory price;

-Garrett Haines & Dave Hidek, 


Tape Op is a bi-monthly magazine devoted to the art of record making.

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