Paul Hales of Pro Audio Technology Points Out the Risks Associated with Automated EQ
Paul Hales of Pro Audio Technology says there are more direct ways to deal with room acoustics than using equalization as a primary tool.
If dealers were to believe the online audio groups and marketing departments of some technology companies, they’d think that equalization is the magic bullet that solves bad sound.
Knowledgeable audio professionals, however, know better. Paul Hales, owner and product designer of Pro Audio Technology, is one of those pros, and he spends a lot of time talking about this controversial topic.
Hales’ approach to room acoustics runs counter to many of the opinions that dominate Internet discussion groups. Hales’ preference is to optimize acoustics by addressing the acoustic domain first.
The veteran audio engineer stresses that while he is not anti-equalization (EQ) and acknowledges that it can be very beneficial when used carefully, he feels that automated programs are not solutions that professional integrators should primarily rely upon to create great systems. With real sound in real acoustic spaces, you cannot “fix it in post.”
EQ is Not a Complete Problem Solver
Examining the problem of room acoustics and the best way to deal with the problems associated with small-room acoustics, Hales says that any dealer that ignores the physical room acoustics and instead relies solely on automated EQ is taking unnecessary risks.
“Room EQ is a controversial topic, I’ve spent a lot of time talking about it actually, and I’ve spoken out against it in general. It’s not that room EQ in itself is bad, but when an integrator or system designer relies on it instead of getting room acoustics correct, then you are making a big mistake there,” comments Hales.
“The right way to approach this and I think the researchers at Harman would even agree with this—get the room acoustics right in the acoustic domain—in other words, get the acoustics right first and then buy the best speakers you can.”
Hales emphasizes there is no substitute for a properly designed room.
Other than expensive active acoustic systems, which are impractical for residential applications, “there are no electronic processing methods that can alter the natural acoustic properties of the room,” says Hales.
“These things are dictated by room dimensions and surface materials. It is always best to optimize room proportions and acoustic properties of the room surfaces— then install the very best audio equipment you can afford. This approach will always yield the very best results.”
Realistically he says that it is possible to design and install systems in environments that are acoustically controlled, but it is challenging. Hales points out there are solutions from acoustics companies that combine décor-friendly aesthetics with acoustical properties, and homeowners can augment these products with traditional furniture, rugs, pillows and other items that are usually found in homes.
Moreover, Hales states that power cables, filtering devices, and other audiophile components aren’t magical problem-solving devices either, but there is some merit to some of these products.
“I don’t believe in a lot of the audiophile claims of superior, ‘magical’ directional cables, etc. Generally speaking, well-designed, high-quality cables from reputable manufactures will perform well in home theater systems,” Hales comments.
“[Solutions] such things as power conditioners can be tricky. In general, clean power will always be an advantage, but our PRO systems require very high power from the main supply [one thousand to ten thousands of watts] during dynamic peaks and sometimes power conditioners are unable to supply enough current quickly enough and can actually degrade performance. Careful system design is required.”
Using a Scientific Approach to Designing Home Theaters
With immersive audio systems continuing to gain momentum in the home audio market, more speakers are being installed into rooms.
According to Hales, today’s object-based, immersive audio systems and the placement of products such as in-ceiling speakers put more of a burden on integrators to hide these products in home spaces.
Some of the burden he refers to include running cables to these “hidden” locations, but the end benefit of object-based audio is worth the extra work.
He continues by saying that having all these speakers, including the possibility of multiple subwoofers requires careful design, and the use of automated EQ systems is not enough to solve the issues associated with acoustics in small rooms.
“If you have really good loudspeakers you won’t need EQ and you won’t want EQ. You are going to want to hear the sound the loudspeaker was designed to reproduce,” stresses Hales.
“So, I think particularly in the midrange of home theater, many integrators, because of these automated systems, I think they feel like they can rely on them to fix any problem they may have and that is a problematic way to go. If you think of the two extremes—if you have a very reverberant room no EQ could make that room not reverberant, and conversely if you had a very dead room no amount of EQ is going to change that room from being very dead.”
Elaborating on the shortcomings of automated EQ, Hales says that ultimately the acoustics of a room cannot change due to its dimensions and the materials used to construct the space. The only thing that can be done is change the sound coming from the speakers.
“Every other point on the continuum between those two extremes it is also true the EQ isn’t going to affect the acoustics. It’s just common sense that the acoustic properties of the room are not going to change. The only thing that that is going to change is the sound coming from the loudspeakers,” he explains.
“So you can make minor adjustments, but you can’t fix acoustics problems in the electronic domain. You’re really just changing the response of the system, you are not changing anything acoustically at all. Now in low frequencies, you can affect the way standing waves [are] perceived. You can’t eliminate standing waves; that’s another thing. The acoustic properties of the room are more a physical reality, you can’t change it with electronic EQ.
"In the low frequencies you can minimize some peaks that occur because of standing waves, but you can’t fill in the dips. The dips are caused by cancellation and if you try to put more energy into the frequency in which the cancellation occurs, it still cancels. You can only really minimize the peaks of the standing waves. You are actually better off positioning the subwoofers so that they cancel the standing waves so the standing waves never occur in the first place,” says Hales.
Based on the science of room acoustics Hales points out the frequencies standing waves occur at are determined by the dimensional sizes of the room, which EQ cannot fix, but EQ does have a place in integrators’ toolboxes.
“What EQ can help with,” says Hales, “is that due to the amount of speakers in today’s immersive systems, unless the listener is sitting where the speakers are aimed, which is the Dolby spec, there will be people sitting in locations that aren’t ideal for immersive listening. EQ can help compensate for some of these issues.”
“So some of the listeners may be positioned far off axis of those speakers, so a little EQ to adjust the response at the listening position for the fact that you are sitting so far off axis, which is usually a boost of the midrange and treble, can be beneficial. You just have to keep in mind that you are boosting the midrange and treble everywhere,” he points out.
“So if someone is on axis of the speaker they will end up with too much midrange and treble. We do a bit of that to the front wide speakers, for example. If they are on the sidewalls, by definition the listeners are pretty far off axis of that speaker and we’ll try to EQ the response at the listening position to mimic more the on-axis response of that speaker. You just have to be careful and not do too much of it or otherwise the total sound in the room will be too bright and aggressive.”
Pro Audio Technology Home Theater Recommended Practices
Offering some tips to optimize the speaker layout of a modern home theater system, Hales says there are several methods that work.
One effective method that Hales recommends is to position the subwoofers 25 percent of the way in from each side of the walls on the front and to do the same in the rear of the room. This placement method, according to Hales, will drive the second order of the standing waves going left to right in anti-phase, thereby minimizing them.
Adding more cancellation Hales advises integrators if the 25 percent of the way rule is applied to side-to-side and up-and-down subwoofer installations, they can place one subwoofer 25 percent of the way in from the wall and 25 percent of the way up on the front wall. From there, integrators can place another subwoofer 25 percent of the way down from the ceiling and another 25 percent of the way in too.
“Now you are canceling it left to right and top and bottom so you’ve canceled two modes,” says Hales.
Providing greater detail on why room design should be done in the acoustic domain, Hales says that ideally, qualified audio engineers should be consulted.
Automated EQ systems he continues, “just don’t know enough about the realities of the room and speakers for example. The automated systems don’t have any awareness of speaker directivity and that makes a big difference because, for example, our speakers tend to be large horn designs that are pretty directional,” he emphasizes.
The result in these types of situations and Pro Audio Technology speakers specifically, less midrange and high frequencies are reflected to the listening position when compared to wide dispersion speakers.
“They [automated EQ systems] don’t know the speakers are more directional so they’ll always try to EQ for the target curve, which will invariably, with our speakers, cause it to either pull a bunch of mid-bass out because it will perceive too much mid-bass, or it will put a bunch of midrange and treble in to get that directivity and you will end up with a bright and aggressive sound,” Hales notes.
One other method Hales suggests is less scientific or analytical, but it uses the experience of integrators to tune systems: Listen with your ears.
“The way I approach it is that I use my ears and I EQ the left and right speakers using music because I know exactly what the music is supposed to sound like. That gives me the EQ for the front three speakers,” he suggests.
“I get those right by ear, and for the other speakers I use a combination of measurements, experience, and empirical knowledge to subtly EQ the speakers that may be off axis, and then I leave it alone.”
Summarizing this approach, Hales points out it allows the natural sound of the speakers to reach the calibrator’s ears without EQ altering the sound coming from the speakers.
Through the combination of having proper manufacturer training, along with proper tools and the experience of installing well-designed speakers, using a combination of analytical tools and simply listening will deliver the best possible results for the customer—and results that are more accurate than generic “one algorithm fits all” automated EQ solutions.
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Bob is an audio enthusiast who has written about consumer electronics for various publications within Massachusetts before joining the staff of CE Pro in 2000. Bob is THX Level I certified, and he's also taken classes from the Imaging Science Foundation (ISF) and Home Acoustics Alliance (HAA). Bob also serves as the technology editor for CE Pro's sister publication Commercial Integrator. In addition, he's studied guitar and music theory at Sarrin Music Studios in Wakefield, Mass., and he also studies Kyokushin karate at 5 Dragons in Haverhill, Mass. Have a suggestion or a topic you want to read more about? Email Robert at firstname.lastname@example.org
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