- by Vince Lepore
in Road Tests
As part of its expansion into the live sound market, Waves has released a variety of plug-ins catering to the professional sound reinforcement user. One recent entry in this category is X-FDBK, a feedback detection and elimination tool used to assist the process of ringing out house P.A. or monitors.
Before the Gig: X-FDBK
Let me start off by saying I readily admit to being skeptical of feedback eliminators, and I’ve rarely used them in the past. I’ve always done just fine ringing out wedges, and I never really felt I needed “help” from a plug-in. However, I went into this review with an open mind. If a tool works and helps me achieve better results in less time, I’ll be the first to admit it. I do like the fact that Waves says upfront that the plug-in is to be used before the show and not during the show, because what live engineer would want a feedback eliminator running in the background during a gig?
The X-FDBK’s relatively simple user interface — that hides some very powerful features — endeared me to this plug-in, even before putting it into practice. The upper two-thirds of the interface are occupied by the frequency response graph, which displays meters for input and output gain, as well as an input analyzer (RTA) and of course, the filters that are being applied by the feedback elimination process.
Below the frequency response graph are the plug-in’s main controls, shown in Fig. 1. Starting from the left, there are settings for low and high sensitivity. This has an impact on the level at which the plug-in detects and reduces feedback frequencies. Although the plug-in can sometimes seem a bit sluggish to grab onto feedback, I preferred the low sensitivity setting, as high sensitivity took cuts that were too deep, applied too many filters, and erroneously triggered filtering off my voice. The low setting was a good balance between detecting valid feedback frequencies and not cutting too much too quickly.
To the right of the sensitivity controls are the setup, add, and reset buttons. “Setup” is the most important button in the plug-in. This activates the X-FDBK detection engine and tells the plug-in to start applying filters. When the detection engine is turned on, the setup button is red.
One nifty little feature is that the plug-in automatically kicks out of setup mode after one minute of use, preventing it from accidentally being left on during a sound check or show. During the detection process, multiple filters will be applied in rapid succession if necessary to eliminate feedback. Sometimes it might be preferable to add one filter at a time, which is what the “add” function is used for. “Add” is a momentary button that engages the detection engine only while being held. During this momentary detection process, a single filter will be added if feedback is detected, and, of course, “add” can be used multiple times if necessary. Finally, next to the “add” button is the “reset” button, which resets all filters back to their default state.
X-FDBK has 20 available filters, each individually selectable, and all are user-adjustable — see Fig. 2. Filters that are automatically applied by the X-FDBK detection engine can be adjusted, manipulated and tweaked independent of the process, and filters can be added manually by the user as well, allowing for a fine degree of user control.
What turned out to be my favorite part of the plug-in are the Global Q and Amplitude controls. As you might guess, these allow the user to adjust the Q or Amplitude of all filters simultaneously. If you feel that the plug-in took cuts that were just too deep in amplitude, you can adjust the cut of each filter individually, or you can adjust them globally using Global Amplitude, and, of course, the same is true for Global Q.
X-FDBK in Practice
That brings us to the million-dollar question of how X-FDBK performs in the wild. I put X-FDBK through its paces on a combination of a DiGiCo SD10 with a Waves SoundGrid Server. When I first engaged the plug-in on an aux bus, I heard a slight but noticeable “phasi-ness” before any filters were even applied. [Note: this sound only occurs on instantiation, while the plug-in is loading, and not during regular operations. —Ed.] That said, as a skeptic going into this review, I really enjoyed using X-FDBK, and I can see myself continuing to use it.
If you are worried that robot plug-in overlords are going to steal your monitor mixing gig, I’m also happy to report that X-FDBK still requires a skilled audio engineer to operate. There are many prerequisites to using X-FDBK effectively. For example, the wedges I rung out were already pre-tuned to have relatively flat frequency response. This contributes to the wedge’s feedback stability before the plug-in was even applied.
Successful X-FDBK usage also assumes proper microphone gain structure and proper aux send levels prior to beginning the ringout process, so there are a lot of things that must be right to get great results. Bringing microphones right to the verge of feedback before engaging the plug-in seemed to produce the ideal result.
The Bottom Line
The best part of X-FDBK is that it nails frequencies more quickly and accurately than a human engineer ever could. When used properly, it can produce equal or better sounding results while saving valuable time — in stereo or mono. On each pass using X-FDBK, I found myself adjusting individual filters after the ring out process was complete, but overall, I was happy with the results that I achieved in less time than I would have required doing it by ear. At $149, the Waves X-FDBK plug-in is an excellent ringout tool for the live engineer.
At a Glance
A complete automatic feedback suppression solution, the X-FDBK plug-in identifies the precise frequencies that cause feedback and surgically cuts them, dramatically shortening the setup time of monitors and P.A. systems.
- Fast, effective feedback suppression
- Simple operation
- Operates in Mono or Stereo modes
- No 96 kHz support
- Supported Live Platforms: MultiRack Native, MultiRack SoundGrid, DiGiCo, eMotion LV1 mixer, Avid VENUE
- Sampling Rate: 44.1/48 kHz
- Street Price: $149
- Manufacturer: Waves
- More Info: www.waves.com