After some discussion about EQ solutions for various applications in another thread, I found myself in a unique position to get some impressions of the FBQ-1000.
It was alleged that the old model, the Feedback Destroyer DSP1124P, was noisy and therefore unsuitable for use in equalizing L/R or Center channels. (A claim which, given the rest of my experience with this brand, I have little trouble believing). It found popularity as a subwoofer equalizer due to the enormous flexibility of the filters, and in that application the noise the device produced was outside the frequency range of system and consequently inaudible. It appears however that few people, if anyone, bothered to look at the full-range capability of the FBQ-1000 in the home-theater setting.
Since my FBQ-1000 is not yet integrated into my main system for the purpose of EQ'ing my subwoofers, I had the opportunity to give it a shakedown in a 2.0 setup.
The test system is as follows:
Alesis Monitor One MkII Passive
Behringer Feedback Destroyer FBQ-1000
2x10ft VTG Audio Commercial 10AWG
Ameriquad XLR-TRS, 4'. Star-quad balanced cable, Neutrik connectors
Having not acquired my desired digital media player yet I fed this system program material from my phone, which is a Sony Xperia Z3v. This method and device have their limitations, and those are taken into account in my observations.
Per Wayne P's suggestion and AudiocRaver's post about noise floors, I did a quick-and-dirty evaluation of the noise floor of the system. There's a faint but audible hiss from the tweeters that is unaffected by changing the volume knobs on the XLS-1000, even running them wide open. Using the SPL meter in my phone (highly unscientific), I was unable to measure a level on that hiss over the noise floor of the environment (2nd floor room in a relatively quiet residential area). I consider this more a source of measurement error than an affirmation of the quality of the system. The XLS-1000 had nothing connected to the inputs, so this is an indication of the amp's self-noise.
The next test was to introduce the FBQ-1000 into the signal chain. The hiss was unaffected by the volume knobs until up past about 80% open. From 80%-100%, there was a noticeable increase in the hiss, but only just. This increase was smaller than the variance on my phone's SPL meter readings, and only apparent to my ear within 18" of the tweeter.
After testing for noise "dry", I introduced filters using the parametric EQ feature of the FBQ-1000.
ASIDE: By its nature, a feedback suppressor is a device which detects persistent oscillations which satisfy the Barkhausen Stability Criterion, isolates their frequency, and subsequently creates a narrow-band parametric EQ to suppress that frequency in the original program. Done well, this effect is transparent and fast-acting so you don't have howling mics in front of a live audience. If these filters get stacked up, it can cause audibly destructive filtering to occur, but that's often the lesser evil. Done poorly, the application of these filters can have unpleasant effects on the signal that reaches the audience... but the technology is not new and processors have gotten progressively faster and sneakier since this idea was introduced decades ago.
The FBQ-1000, in addition to its normal duty as a feedback suppressor, will allow the end-user to manually set up to 10 fully parametric EQ filters, with an impressive level of specificity. Each filter is variable 20Hz-20Khz, tunable in 1/60th-octave increments, 1/60th-octave to 2-octave bandwidth, -48dB - +16dB gain, and can be switched ON or OFF independently.
With no signal, the presence of the filters was undetectable to my ears unless I opened up the amp gain all the way and swept the frequency with the EQ gain maxed out (up or down).
For the final test, I applied more practical filters to a test track from my phone and swapped back and forth between having the filters ON and OFF.
My conclusion, with all its margin of error, is that the FBQ-1000 can exist and operate transparently in a full-range application and provide robust EQ capability. If you need a solution for a L/R or Center channel and you have 1RU of space, this device will suit your needs quite nicely. The controls are fairly intuitive, though one does benefit mightily from reading the manual (as with any equipment).
I may go back and revisit this test with my BGW Systems Model 150 amp, and more senstive measurement setup... but for all but the priciest setups, I'd say Behringer does a great job.