Re-Equalization (Re-EQ) is a feature found only in THX Certified AV Receivers and Pre/Pros. The problem it’s addressing is one of correcting the overall sound quality of a film soundtrack that was mixed for a large theater to the home environment. Large theaters are equalized following the “X-Curve”, a standardized response curve. Oddly, the curve itself was developed to solve the same issue, but in reverse. Material mixed in small rooms sounded too bright in large theaters, so using the technology of the time (early 1970s), the X-curve was created to correct the issue. Theoretically, the vary existence of the X-curve should have made Re-EQ unnecessary. But it didn’t work that way.
Original data collected to develop the X-curve was limited in resolution, and therefore, accuracy. It turns out, there is a small but noticeable error, which creates the same problem in reverse: material mixed on a large X-Curve dub stage sounds too bright in the home. Tom Holman, developer of THX for theaters and homes, described the Re-EQ curve in the original Home THX specs. Some of us early home theater adopters had already noticed the problem, and were very relieved that Re-EQ made those bright-sounding Laser Discs sound smooth and natural. It worked.
So why, then, in 2011, is the Re-EQ function more and more ignored? It has to do with how soundtracks are handled for home video. In the early days, the only choice was to take the original masters and do a straight transfer to the home formats. Nothing was changed at all, in fact, the more accurate the transfer, the better. That started to change when DVDs came along. The film industry started to think it might be a good idea to re-master those theater-centric soundtracks for the home. So, what did they do? Rather than send the material off to a mastering lab with a reference home theater, the material was sent to music mastering labs. Now, while that might sound like a good idea, in fact the music industry is remarkably un-standardized when it comes to the monitoring environments used. What came out of that is re-mastered tracks that not only no longer required Re-EQ, but also had changes made in overall equalization and dynamics that now made it impossible for people with calibrated home theater systems to duplicate the theater experience.
Is there any hope?
Actually, yes! The folks at DTS made sure that the new Blu-ray audio spec included DTS Master Audio along with Dolby TrueHD. Yes, it’s competition. We could debate technical advantages of one over the other all day, but what it gets down to is which company positioned itself where it could work with content producers in a way that was helpful and beneficial. DTS did that. What’s coming out of their efforts is really good mixes intended for the home. And since they knew that’s where it was going, they took care of Re-EQ in the re-mastering stage. Get your BD player going, and pick the DTS track, then turn off THX Re-EQ (usually, just turn off the THX Surround mode).
But is that an universal fix? Sadly, not yet. In the mass of legacy DVDs it’s pretty wild. You have to listen to make the choice. Is it too bright? Then kick on THX Surround. Is it too dull? Turn THX off. And, listen carefully to those Blu-ray discs. It’s not 100% by any means. But at least it’s a start.