Some improvements have been made to compressors over the years, where you take the signal and break it up into different frequency bands, and put a compressor on each of those bands, the idea being that only the frequency bands that have something loud in them will be compressed, and not the whole signal. But if there’s an explosion, which means the 60-70Hz bands have something extremely loud in them and the rest don’t, if you compress those bands and bring them down, you’ve done changed the frequency response, because you’re turning down just the bass. And Hollywood mixers get very upset when you do that. They’re okay with you turning the volume down. That’s one thing. But intentionally changing the frequency response is not okay with them. So we don’t use bands.

Our approach is different. We look at the time domain signal as it’s varying, estimate how loud it is, and make adjustments slowly or rapidly, depending upon what needs to happen.

What do you say to people who accuse you of tinkering with the artistic intent of a carefully crafted surround sound mix?
Actually, I say that we’re trying to preserve it. Whether it’s the user or the system turning the volume down, Dynamic EQ is tied into Dynamic Volume. So, if I make it softer, all of the things I said earlier about preserving the frequency response and the spatial impression are still in play, whether it’s done automatically or not. You can’t turn on Dynamic Volume without having Dynamic EQ on. So for that reason, we’re actually preserving the artistic intent of the surround sound mix, considering the fact that the user simply isn’t going to play it at the volumes it was mixed for. So, given the reality of real-world listening situations, we’re trying to translate the artistic intent as much as possible.

You say you can’t turn on Dynamic Volume without turning on Dynamic EQ—is the inverse true, as well?
No, you can turn on Dynamic EQ without engaging Dynamic Volume. If you have a dedicated room and you want to listen at reference levels, or for whatever reason you don’t want or need Dynamic Volume on, you can turn it off and Dynamic EQ will stay on.

It seems like a lot of what you’re doing is taking mixes that were intended for large cinematic spaces and modifying them so they work better at home. What about the DVDs and Blu-rays on the market that contain near field mixes, specifically designed for home theater?

Dynamic EQ and Dynamic Volume really aren’t affected by that, but what is affected is the target equalization curve choice in MultEQ. The high-frequency roll-off that is in the Denons and other receivers is called the Audyssey Curve. That assumes that the mix was done for theaters [and therefore mixed with increased high-frequencies to compensate for the sound passing through a large cinema screen]. So if you have a mix that was actually done for the home, we recommend that you switch to the Audyssey Flat Curve. The problem is, you don’t always know. I wish the studios would make it clearer, who does it and who does not. It’s not the majority of them, but there are some—New Line and a few others—who do this. So we have no way of making it automatic, because we have no way of knowing whether the mix was done for theaters or for home. But if you do know you’ve got a near field mix, you should set it to Flat.

Could it be made automatic somehow? Could the sound mixers put a flag in the bitstream?
Yeah, Tom is trying to get them to do that. He knows a lot of the post-production houses, and there are empty flags in Dolby Digital that could be used for things like that, but habits are hard to break. Those guys just don’t use flags. I think that it will happen eventually. I’m just not sure how soon it will happen.

What’s the next big problem you want to solve?
The next big problem relates to MultEQ: in our pro applications, our installer applications, we provide a few more options than what you have as a consumer. We’ve come up with a few preset equalization curves that work for different sized rooms, because different sized rooms require different amounts of high-frequency roll-off, depending on how much acoustical treatment they have. So today we do that with presets and guidelines. But what we’re working on is to make that completely automatic, so that a measurement of the reverberation time and knowledge about the size of the room and the position of the primary listening position—because that affects how much direct sound and how much reverberant sound you’re getting—will give us exactly the right EQ curve for that room. That’s a lofty goal. It’s a really difficult problem. But we have a good team that’s working on it now, and we have a whole series of experiments that we’re doing in the lab to figure this out.

When might we start to see that?
My best guess is that we might start to see models with that appearing… a year from now. That’s just a guess, though.

Click here to view slideshow of Audyssey-enabled receivers

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