Dolby Podcast Episode 35, February 28, 2008
Terry Paullin, a professional home theater calibrator and frequent writer on the subject, shares home theater audio calibration tips with Craig and Jack. Terry joined us in an earlier Dolbycast episode about video calibration, The Calibrationist, Part 1, Video, on February 14, 2008. Listener, Chris, finds out how he can produce 7.1 channel content using Dolby technologies.
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Mentioned in this Episode
[intro music]
Jack Buser: Hello! And welcome to Dolbycast, the insider's guide to entertainment technology from the experts at Dolby Laboratories. I'm Jack Buser.
Craig Eggers: And I'm Craig Eggers.
Jack: And we're here to give you the straight talk on everything you need to please your ears.
[Musical interlude]
Craig: And welcome back to Dolbycast, Mr. Jack Buser. Hello.
Jack: How you doing? How you doing? I just want to say "Sparky" so bad. But I won't, because I'm being good. Hello, Craig.
Craig: That's good. That's really nice. That's really nice.
Jack: [laughs]
Craig: Well, you know what's interesting is we received so much positive feedback on our last edition with Terry Paullin that we actually invited Terry to come back.
Jack: We did.
Craig: Terry Paullin, for our listeners who might have missed the last podcast, is an ISF calibrator [see The Calibrationist, Part 1, Video on February 14, 2008 –Ed.]. He does professional room equipment calibration, and that includes audio as well as video. So we thought we'd invite Terry back and pick his brain with regards to how he sets up a room for proper audio calibration.
Jack: Absolutely. I'm really looking forward to it.
Craig: So we'll join Terry in just a moment here. But I think you do have a...
Craig and Jack: [together] Listener question.
Jack: Yes, we're actually somewhat making it through our stack of listener questions. So, hopefully those of you that have written us in... "Written us in." There's that little Kentucky accent coming out again, second podcast in a row. Who have written us...
Craig: Dude.
Jack: [laughs] And have been wondering where your question is, are we going to answer it? Yes, we will answer every question we get, if we can get to it. If you want to write us, our email is dolbycast@dolby.com. You can write us in any question you have about anything whatsoever.
Craig: And what's that phone number, Jack?
Jack: The phone number is 888-6-DOLBY-C. That's 888-6-DOLBY-C. You can call us. You can write us in, again, at dolbycast@dolby.com. We love to get your questions, and we'll be happy to answer them all here on-air.
But before I go any further, let me please answer this question from Chris. And this is another Chris...
Craig: Another Chris.
Jack: Because the last Chris was Kris with a K. This is Chris with a C.
Craig: OK.
Jack: Chris, actually, is a content producer, and he's wondering if there is going to be a Dolby Digital Plus encoder released, because he wants to mix 7.1 channel sound. So, Craig?
Craig: And the answer is?
Jack: And the answer is: yes, there is. And in fact, it already has been released. It's called Dolby Media Producer, and you can find more out about it on dolby.com. There are 2 editions. There's a network edition, and there's a standalone edition. And I see, from reading Chris's email here, that he's probably going to be interested in the standalone edition, because it's going to allow him to experiment around with 7.1 channel mixes and encode those into Dolby Digital Plus, or indeed even into Dolby TrueHD, which is lossless 7.1.
Craig: Dolby TrueHD, yeah.
Jack: So, Chris, hopefully that answers your question. We're going to go to a break. When we come back, we're going to be talking to Mr. Terry Paullin, who's going to be filling us in on everything about calibrating sound and what he does when he goes in to calibrate somebody's home theater system. We'll be right back.
[Musical interlude]
Announcer: If you have questions for the experts at Dolby Laboratories, email us at dolbycast@dolby.com. That's dolbycast@dolby.com. For more information and links pertaining to today's topic, be sure to log on to dolby.com/dolbycast.
Craig: And we're back at Dolbycast, with Mr. Terry Paullin. For our listeners, Terry is an ISF calibrationist, who makes home theaters not only look better but sound better.
Jack: Sound better.
Craig: And we thought we'd invite Terry to come back and speak with us about how he calibrates a home theater system for audio performance. So welcome back, Terry.
Terry Paullin: Thanks for having me.
Jack: So, when you go into somebody's home and calibrate for audio performance, what is the very first thing you'll do after walking into the room, generally?
Craig: And turning on the system. [laughs]
Jack: Turn on the system. Thank you. Thank you. Question answered. [laughs]
Terry: Well, I usually start by asking for a glass of wine.
Craig: [laughs]
Jack: [laughs]
Terry: I actually don't listen to the room as it stands. None of that matters. I'm going to be listening to test tones first, and what matters is how it sounds when I leave. So, we start with test tones. We set levels first.
And the thing that I think your listeners should appreciate is that every room has its own unique acoustic signature. They're all different. Even rooms that appear to be the same size, depending on furnishings and a lot of other things, can have different signatures.
So there is really no substitute for calibration and looking at that signature with something like a real-time analyzer, either octave or 10th octave, whatever. But after we set levels, the thing that I'm most worried about, I guess, is a standing wave. And those are generally created by the subwoofer. So, what we want to do, we can't necessarily make every seat in the theater perfect. We identify the sweet spot, sometimes known as "the money spot."
Jack: [laughs]
Terry: And it's usually where he and she sit. And we place the microphone between those 2 seats, and we calibrate, have everything as right as it can be in that position, and hopefully the rest of the theater isn't going to be too terribly bad after we've done that.
Craig: So, Terry, a lot of people don't have a dedicated home theater room, if you will.
Terry: Right.
Craig: And so they're enjoying entertainment in their living room.
Terry: Mm-hmm.
Craig: Room aesthetics, speaker placement, and basically what's on the walls, how does that impact what you do, and what type of suggestions would you offer our listeners?
Terry: Well, everything hanging on the wall and in the room affects the sound, one way or another, to some degree.
Jack: So it's got to go. [laughs]
Terry: There is always a very careful balance that an installer has to strike between what is acoustically proper and what is aesthetically acceptable.
Jack: Right.
Terry: And very often, the interior decorator, or the wife, has a lot to say about that. So we try to deal with what's there.
Again, before I would move anything, I would put calibration tones in the room and look at them with something better than a sound level meter and get a sense of what that acoustic signature is and try to deal with it. Usually, in the case of a standing wave, if you're not in a dedicated theater, and it's more likely that you won't be—most people will take a family room and turn it into what I call a “theater environment”—you're probably not going to have a standing wave, because the room's probably going to be open to the rest of the house. You might have something weird in the listening spot.
Craig: And for our listeners, a standing wave is also called a null point sometimes. It's the place in the room where, literally, you can stand and you don't hear any low frequency information.
Jack: What's going on with a standing wave?
Terry: Well, in the case of a subwoofer, which, hopefully, you've got your system set up where the subwoofer isn't working on anything other than frequencies below 80 Hz. The wavelength of those notes, those sounds, is so long that your ear can't isolate where it's coming from, and it's long enough that, depending on the dimensions of the room, they can be additive. And the effect that you find, if you have a standing wave, is that, in one spot, it's one level, and you can move over 2 feet and it's 10 dB higher.
Jack: Right.
Terry: And that is not what you want [laughs] in a home theater.
Jack: [laughs]
Terry: And the fix is usually fairly easy. Usually, if you take a subwoofer and move it 6 inches on a side of a wall, if there is a standing wave, you can move it out of the sweet spot, which is what we want.
Jack: So, is it trial and error?
Terry: Well, it's trial and measurement.
Craig: [laughs]
Jack: [laughs]
Terry: And then move something.
Craig: Or in Jack's case, error. [laughs]
Jack: Error, error, error. [laughs]
Terry: You move it, and then you measure again.
Craig: So, Terry, Jack and I have talked about this in previous podcasts, and one of Jack's favorite ways to really understand how to get the best bass performance in the money spot, the sweet spot, is to literally put the subwoofer there, and move around the room and listen to it. And in the place where, obviously, you get the best performance, you hear the best performance, is probably the place to put the subwoofer.
Jack: Then you swap them.
Craig: My friends at THX actually put a subwoofer on a set of rollers, casters.
Jack: Oh, funny.
Craig: And they move it around the room that way, and they listen in the money spot. So I'm curious as to how...
Terry: You actually have friends at THX. I'm surprised.
Craig: I actually have friends, yeah. Yes.
Jack: We have lots.
Terry: Wow.
Jack: Actually, I was talking to mine just yesterday. [laughs]
Craig: They use our technologies all the time.
Terry: The process that Jack advocated there is certainly one thing you can do. It's kind of the reverse of leaving the subwoofer alone and measuring what it's doing in the room. Again, it turns out that you don't really have to do much. Because your ears can't isolate low frequencies, the subwoofer can go pretty much anywhere in the room that it doesn't cause a standing wave.
And there are more options there. I mean, there are more good options than bad options. So we generally start with what is aesthetically acceptable to all parties, and that's usually a subwoofer in a corner, and then we see what kind of damage that does to the acoustic signature.
Jack: [laughs]
Craig: [laughs]
Terry: And then, if we have to move it, we do. One hint, I guess, for your listeners, if you can work it into the budget, [laughs] and you can get clearance from the aesthetic police, is to have multiple subwoofers in a room. If you have two subwoofers in a listening environment, it's very improbable that you'll have a standing wave.
Jack: That's an interesting point. We actually had a listener question about exactly this, so I'm glad you brought it up. And the listener was saying, "Two subwoofers. What's the deal? Is it better to have 2? If so, why? What's going on?" That's a very interesting point.
Terry: Yeah. I would say it's better to have 2, for that exact reason. You reduce the probability of a standing wave a lot. It's also nice to have the bass reinforced. You can either have larger subwoofers. All you're dealing with, with a subwoofer, is the laws of physics. You can have a cone that travels further, you can have a larger cone, or you can multiple subwoofers.
Jack: Right.
Terry: And often times it's more aesthetically acceptable in a room to have 2 10-inch subwoofers instead of a 12 or 15 somewhere.
Jack: Interesting. Now, do you have problems with cancellation if you do 2 subwoofers? Do you have to be careful?
Terry: Well, if they get in just the wrong places, you can have that. But I'm just saying the randomness of the way low frequencies are propagated is such that you're not going to have a standing wave, probably. I understand that in a future Dolbycast, you're going to have Tony Grimani on.
Craig: Mm-hmm.
Terry: And he is the absolute guru at that. So, more from him on that topic.
Craig: Is that right? Excellent.
Jack: Oh, interesting. OK, OK. Very cool.
Craig: So, in home theaters, we have a lot of different options with regards to sound reinforcement. We have full-range speakers. We have satellite sub systems. We've got systems that employ full-range speakers across the front and maybe satellite type speakers in the rear. Talk about that for a moment. Do you have preferences?
Terry: Yeah, I do. The number one rule: you want to keep tonal balance amongst the 5 speakers.
Craig: Right.
Terry: So we don't like to have different drivers, necessarily: huge drivers up front and smaller drivers in the rear. It's always best, I think, to let the subwoofer do the heavy lifting. So you basically cross over to the sub at 80 Hz, and basically keep the 5 other speakers from having to reproduce anything below 80 Hz.
Jack: Right.
Craig: So, in the case of a bookshelf type speaker system, a lot of the bookshelves will go down to 80 Hz.
Terry: Yes, they will. But you still want to set the receiver on small. That's the clue to the receiver to send the low frequencies to the sub. You'll still get a lot of reinforcement. It's still better to have the other speakers that have 8-inch cones and can go down pretty low, but you don't want them to do most of the work below 80 Hz.
Jack: You would ideally have 5 identical speakers?
Terry: I would.
Craig: Or 7 identical.
Jack: Very cool. Or 7 identical speakers. Very cool.
So, that brings up the questions of dipoles and direct radiators in the back. What's your opinion on those?
Terry: Well, you're going to have to start with whose sound propagation philosophy you want to believe in.
Jack: [laughs]
Terry: I'm actually an advocate of the THX approach, which says dipoles in the rear. What we want to do is have the front end be very direct. We don't want any side reflections.
We want everything that comes out of the front sound field—the left, center, and right—to hit your ears at the same time and not go through any other path. In the rear of the room, we want exactly the opposite: we want diffraction. We don't want your ears to be able to locate anything coming out of the surrounds, particularly in movie material. That's what the mixers put in there is just sort of ambiance kinds of sounds. That's why we like dipoles in the rear.
Craig: And that's why Sparky and you disagree on this particular subject here.
Jack: [laughs]
Terry: [laughs]
Craig: As you know, I'm a big fan of direct radiators, because I listen to a lot of DVD SACD music.
Jack: Interesting.
Craig: I want that discreteness in my music.
Jack: So I'm right between both of you, because...
Craig: Stand aside!
Jack: I have dipoles in the back, but I play a lot of games, where it's absolutely critical to be able to locate exactly where your enemy's coming from around you. So I'm right between both of you. [laughs] I actually bought the dipoles.
Craig: Some speakers have switches on them that enable you to do that...
Terry: I think you're giving the speaker system too much credit there. What determines what comes out of the left and right, either on movie or game material or discrete, 6-channel audio, is the mixer. [laughs]
Jack: Right.
Terry: If the guy mixed something in the left rear, it's going to come out there.
Craig: That's true.
Jack: That's true.
Terry: And the fact that it's a dipole really doesn't matter.
Jack: Interesting. Interesting. Well, let's talk a little bit more. I want to talk about, actually, room acoustics a little bit when we come back. We've talked a lot about the system. But let's talk, when we come back, just about how important the room is to the overall sound of the system.
[Musical interlude]
Jack: Hey, listeners! You can now call in your question to our new toll-free phone line: 888-6-DOLBY-C. That's 888-6-DOLBY-C.
[Musical interlude]
Craig: And we're back at Dolbycast, with Mr. Terry Paullin. I know, Jack, you wanted to talk about room acoustics and how the room impacts the whole environment.
Jack: Absolutely. Well, we've talked a lot about just some basics. If you do have the luxury of being able to set up the room and decorate it the way you please, even if it is your main living room and also your home theater, the idea of getting a big, heavy couch or drapes on the windows, simple tips like that. Are there any simple tips that you have for people that you've been generally able to make fly?
Terry: Not really. You have to make peace in the family first, [laughs] before you call the installer in. You've got to decide: are floor standing speakers going to be allowed? Do the speakers have to be white? A lot of real fundamental things that an interior decorator, or someone with more power in the house, might get to decide.
And so, what I always start with, when I sit people down for Home Theater 101 is to make them understand that there is a trade-off between what is performance-correct and the aesthetics of the room. And that's not for me to decide, really. It's for the guy who's going to write the check.
Jack: Right.
Terry: So they need to get comfortable with all of that first. And then I explain the performance trade-offs between the choices, and then they just have to go from there.
Craig: Terry, hardware floors are very much in vogue. What do you do if somebody has a home theater setup, and they've got these beautiful hardwood floors?
Terry: Well, they're very reflective. And I'm going to tell people, for one thing, don't spend a lot of money on a THX system that has the directivity of the center speaker very carefully narrowed if you're going to put a reflective surface either on the floor or on the ceiling, because that's going to defeat the money that you spent for the THX certification. So we recommend large, thick area rugs where there is a hardwood floor. It's just not a good thing to have. You can imagine a stereo set up in a gymnasium, and that's...
Jack: [laughs]
Craig: [laughs]
Jack: That's right. That's right.
Craig: So, one of the topics we covered, just earlier, and I want to come back to it for just a second. There are crossovers on subwoofers, and then, when you set up and calibrate your system, when you go into the system menu of your AV receiver, it sometimes asks you, "Do you have large speakers? Do you have small speakers?" And it even asks you, "Do you want to set the crossover point for your subwoofer?"
What's the best way to approach this? Do we want to set the crossover point for our subwoofer in our AV receiver? Do we want to pass full range, or limited range, if you will, to our subwoofer and let our subwoofer crossover do the hard work and heavy lifting? What do you do?
Terry: Well, for one thing, the controls in a receiver are often a little bit cryptic, and they don't always do what they say they do. And what you really want to do is get one of those systems or the other out of the way so that you're not trying to roll off bass frequencies in 2 different places.
Jack: Right.
Terry: So, what we really try to do, by simply taking the receiver and setting the speaker size to “small”, you're telling the receiver, "Send everything below 80 Hz to the subwoofer."
Craig: All channels. All channel information.
Terry: Yeah, all channels. And so that's what you want to do, regardless of the size of the cones in the other speakers. You want the subwoofer to do the heavy lifting. So, at that point, then the crossover control on the subwoofer itself is immaterial. It just doesn't matter. It's not there.
Jack: Right. You should turn it off, at that point.
Terry: Well, everything that's coming in is going to be below 80 Hz, so you don't have to worry about rolling off at 120.
Jack: There you go.
Craig: That brings up a good question, Jack. Do all subwoofers have a crossover on and off?
Jack: Some do. I know mine does, but I have seen them were it just has a crossover level. So, generally, what I've told people is, if you've set the bass redirection up properly in the receiver, and there's nothing but a crossover point, just a dial, just make sure it's all the way up, and then you can't go wrong. You don't have to worry if you've turned it down to 60 or something like that and you're accidentally rolling off lower than what your receiver is doing.
Craig: Yeah. I guess my concern is that I would never, ever turn the crossover frequency all the way up.
Jack: Really? On the sub?
Craig: Well...
Jack: You're filtering the receiver. Who cares if it's...
Craig: Yeah. As long as you're filtering in that receiver.
Jack: That's right.
Craig: But you really have to do that. You have to set up your receiver to do that.
Jack: Absolutely.
Craig: Because what you don't want are 150, 200 cycles coming out of your subwoofer.
Jack: Absolutely.
Craig: Because now you're bringing directionality back into the mix from the subwoofer and it's not supposed to do that, right?
Terry: Here's a good time to advocate professional calibration.
[laughter]
Terry: What you really want to do is bring in somebody that's got the right instrumentation and has a signal generator, can put 80 Hz in a system and see if the crossover is rolling off where it's supposed to.
Jack: Our previous podcast where we had you in, we were talking a lot about finding an ISF calibrator. How would you recommend a listener go about finding somebody to do audio calibration?
Terry: I started to say a lot of the guys do both, but that really isn't true. I don't know too many people, besides me, that actually do that.
Jack: [laughs]
Terry: People that are in the "building a complete home theater" business will do that. They'll have the right equipment.
Jack: Mm-hmm.
Terry: Boy, there's a thing called the Acoustic Alliance.
Craig: Home Acoustic Alliance. Gerry Lemay.
Terry: Home Acoustic Alliance, run by Gerry Lemay. He has a website, and I'm sure he can direct people to somebody in a local geography that has the right stuff and maybe has even been certified with his class.
Jack: Absolutely. If there's one thing that I've learned from the past 2 podcasts, it's how important professional calibration is, both from an audio and video standpoint. Just from having this conversation, I realize I can't wait to get home... [laughs]
Craig: I have a question for you.
Jack: Yeah.
Craig: Do you set your surround sounds hot, or do you set them flat?
Jack: No. No. Oh, and this is a good question for you. This is one thing that I've done in my house. Sitting on the coffee table is always a little Radio Shack SPL meter. You got any kind words? [laughs]
Terry: Well, I think they're probably better than your ears.
Jack: Right.
Terry: It's a $40 piece of test equipment, compared to a professional's going to bring in a $3, 500 real-time analyzer, so you would expect that they could do a better job. No, it's not a bad thing. But that's just level setting.
Jack: Right.
Terry: You can't chase a standing wave with one of those.
Jack: That's very true.
Terry: And you can't find where there are odd peaks in the room with a sound level meter. But they're not a bad device. I carry one.
Jack: Sure.
Terry: I mean, I have it, in case my real-time analyzer dies.
Jack: [laughs]
Craig: Terry refuses to listen to Sparky's home theater, because Sparky likes his surrounds hot.
Terry: [laughs]
Jack: [laughs] And what about auto-cal. I'll come clean. I'm a fan of the auto-cal on my receiver. For whatever reason, it just did the job for me. And now, someone else used the exact same receiver, albeit in a different room, and had a very different experience. Do you have any words about auto-calibration?
Terry: Well, as you might expect, I don't use it myself, because I come in with a whole different set of equipment and a different process that I believe to be better than auto-cal processes.
Jack: Sure.
Terry: However, the people that I've talked to that have used it... Let me back up and say I was fortunate enough to have dinner, at the last CES, with Tomlinson Holman.
Jack: Cool.
Terry: And his company does that as a big deal. And their technology is in the Denon receivers, which, they've got two-thirds of the market. And a lot of people use it, and I would have to say with mixed result.
Some people believe, as you did, that it was a great improvement, and others believe it made things worse. And of those that said it made things worse, who knows if they were following the process properly and setting things up. So, without having been there, physically, to see what happened, I really can't speak to how accurate it is. But we did hear their pitch and get a demonstration, and I have no reason to believe that all that stuff shouldn't work pretty well.
Jack: Interesting.
Terry: It seems like it ought to. You're still using a microphone and putting it in several places, which is not as good as a real-time analyzer that can show you the real-time signature of the room as you move things and adjust things.
Jack: Interesting.
Terry: But I think, next to having a room professionally audio calibrated, yeah, I think you probably can rely on them. I think they're pretty good.
Jack: Cool. Well, very cool.
Terry: There are several standalone boxes. It doesn't have to be built into the receiver.
Jack: Right.
Terry: Audyssey and others make boxes that do that.
Craig: So, tough question for you, Terry. Without naming names...
Jack: [laughs]
Craig: I'll set this up. Our producer, Scott, sent out a web address of a gentleman that's got a $6 million home theater system. So, without naming names or where they're at, tell us about the biggest, baddest home theater system you've ever done.
Jack: Yeah!
Terry: Well, the $6 million guy needs to be rushed to medical care.
Craig: [laughs]
Jack: [laughs]
Terry: He obviously needs counsel.
Craig: Opinions expressed on Dolbycast are not necessarily those of Dolby Laboratories.
Jack: [laughs]
Terry: OK. Yeah, I don't [laughs] think that's necessary.
Craig: [laughs]
Jack: [laughs]
Terry: The best theater I did was in a place called Ruby Hill. It's not terribly far from where you live, Craig.
Craig: It wasn't my system?
Terry: No, it wasn't.
Jack: [laughs]
Terry: Your system in your bedroom comes close, but this one would have to win.
Craig: OK. [laughs]
Terry: I did it about a year ago. It's actually going to be on HGTV, if they ever get that episode out to the street. But I was there for the videotaping.
Jack: Cool.
Terry: Anyway, it was a 12-seat, dedicated theater. The room was about 22’ by 35’. We used a 3-chip DLP projector.
Jack: Cool.
Terry: We had 4 subwoofers in the room.
Craig: Wow.
Jack: Nice.
Terry: Yeah, I know.
Craig: Cool.
Jack: No standing waves there. [laughs]
Terry: Yeah. A Klipsch front end and a lot of video processing.
Craig: What kind of a screen did they have, Terry?
Terry: They had a 2.35 masking screen.
Jack: Oh, cool.
Terry: By the way, this kind of gets back to the video stuff, but 2.35 is the only right way to see most action flicks. It's very, very cool and uses the full resolution of the image.
Jack: That's very cool. That's very cool.
Terry: But anyway, yeah, that theater, it didn't [laughs] come anywhere close to your $6 million guy...
Jack: [laughs]
Terry: But I would put it up against any other theater built, anywhere.
Jack: Very cool.
Craig: 7.1, Terry?
Terry: No, it wasn't.
Jack: No kidding? Wow. Very cool.
Craig: It was 5.1?
Terry: It was 5.1.
Craig: Wow. Well, that just proves...
Jack: That speaks to...
Terry: We have to have more 7.1 content before I can actually tell somebody they need to buy 6 and 7 channels.
Jack: Well, listen, Terry, on that note, I will say it has been wonderful having you here at Dolbycast. And please come back and see us again someday.
Terry: I'd be happy to.
Craig: We definitely want to talk in the future about front-projection systems, because there's a whole science and art to setting up a front-projection system, and doing it right.
Jack: Well, you know how I'm rabid about that stuff. Absolutely.
Terry: Lots to be talked about there.
Jack: [laughs] Why do you point at me when you say "doing it right"? We are Dolbycast!
Craig: What is the gain level of that wall in your house, man?
Jack: [laughs] Listen. On that note, then, my name is Jack Buser.
Craig: And I'm Sparky.
Jack: [laughs] And together, we form Dolbycast.
[music]
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