Will Automatic Audio Calibration Lead To Great Sound Or Even Optimal Sound?

Room Acoustics

Home theater processors today are loaded with settings that make it a confusing problem at best for consumers and installers alike to get the sound quality promised by the high quality equipment available on the market today. Don’t worry though most manufacturers today include products that claim to solve all of your problems by running their particular brand of software that can tackle even the most challenging situations you encounter. These include solutions like ARC, Audyssey, Dirac, EMO-Q, MCACC, RoomPerfect, Trinov and YPAO. The claims made by some of these systems include the following:

• Correct the colorations introduced by your room.
• …adjusts the music signal to your room acoustics, removes the negative effects and presents only the pure music for you to hear. And it works perfectly in any kind of room, and with any kind of music system.
• …an automatic sound field adjustment system that enables you to precision-tune your system to your living room, just like a sound professional, but with minimum effort.
• …for Professional Grade Automatic Acoustic Calibration.
• …correct early reflections for studio-quality sound.

• …ensures the speakers’ award-winning sound isn’t lost in a less-than-perfect room situation.

Claims like these convince most consumers that whatever sound performance they are getting the receiver or preamplifier has done the best job possible at optimizing their equipment. As a professional in this field I have significant experience with these products and opinions on their relative success and failure. To summarize my opinion I will say upfront if you believe all of these claims, I have a bridge from Brooklyn to Manhattan we should discuss the sale of. I know many people are skeptical of professionals and their opinion’s of products. I believe an examination of the problems to be solved in home theater can be taken such that a layman can understand some of the limitations these calculations will have at addressing the problems found in home theaters irrespective of the issues associated with details of each particular product.

The first thing to discuss is the issue of room acoustics and how effective these software applications are at dealing with this. The first thing to understand is what are room acoustics? In it’s most basic sense it is how sound behaves in an enclosed space or the physics of sound waves in a room.

The primary phenomena associated with this is how quickly the sound fades away in the room or how much echo there is in a room. There are specifications for this in a theater setting. The physics of this are definitely not altered by any calculations performed in the receiver or preamplifier. However, the rate at which sound decays in a room will dramatically impact the sound heard either for good or bad depending on the room. A theater is supposed to be a relatively dead space acoustically and the reverberation is added to the recording when the movie scene calls for it. When a room is too live acoustically it will add more reverberation to the sound than that heard by the mix engineer. The echo heard in the movie scene will sound too strong if your room is too live acoustically. Excessive echo can reduce the dialog intelligibility of the dialog and clarity of the sound. This effect is something akin to a projection image being degraded by ambient or reflected light in a room. The only way to get room decay to be reasonable is by having a reasonable amount and distribution of absorptive and diffusive acoustical materials in a room. Many people do not add specific sound absorbing or diffusing products to their theaters, but expecting some software to reduce this problem is misguided. In other words if you have a room with a lot of glass, bare walls, tile or wood flooring do not expect any of these packages to help you reduce the impact of the room echo on your sound system.

Another thing associated with the rooms acoustical performance is where the speakers are located in the room along with where the listeners are located. Adjusting settings in the audio processor to correct for poor speaker or listener location is very misguided if it can be solved by moving one or the other. For example, take the absurd case of a speaker pointed at the wall instead of the listener. Would you turn it around our boost the treble and volume to compensate for it being positioned poorly. This is an extreme example, but an easy one to understand. Similar less obvious positioning errors occur regularly in systems that are simple to difficult to fix, but a much better solution can frequently be had by making these changes than trying to solve it with audio settings alone. Obviously, these software solutions will do nothing to modify the positioning of your equipment or seating. I find speaker positioning to be critical to good sound and these products again offer no guidance with this.

Denon Audyssey vs. Manual EQ With No Changes In Settings On Subwoofer

Room acoustics and speaker performance can also change the frequency response at the listening position. This is where the audio settings can be of use and one of the primary things these products offer that is complicated to do well, but they are not the only method available to improve this. Pointing or moving the speakers properly can dramatically improve this without resorting to modifying the audio signal and possibly increasing distortion. Trying to adjust the audio settings to fix a low point in the frequency response caused by a room null is a big mistake. You can throw all of the power you want at a null and you are only likely to cause distortion because the physics of wave cancellation is causing the null and you will not fix it with more power at that frequency. The best way to fix a null is to either move the speaker or the listener or add another subwoofer to help cancel the null since these typically are worst at frequencies the subwoofer operates in. My experience is that these automated systems almost always yield a frequency response much worse than can be obtained by manual adjustment of the equalization in these products implying that the receivers system or logic being employed are not optimal as suggested in the marketing information.

Bass management along with speaker crossover settings is another thing these products promise to set for you. I do find that sometimes they get these right, but they also fail at this about 50% of the time. The biggest problems tend to occur when the settings on the subwoofer are wrong. The auto calibration products offer little to no guidance on how to optimize the settings on every subwoofer, but if this is not done correctly bass management along with the LFE channel will be severely compromised. If you luck out and get these close to right the crossovers may be very close to right using many of these products. Unfortunately, the number of settings on these products vary along with their meaning and accuracy. For example, the phase switches are frequently labeled backwards. Determining what the proper values are for every situation requires some instrumentation to measure the LFE frequency response, the absolute phase of the subwoofer and the frequency response of subwoofer and speakers in your system. Knowledge of the actual size of the components in the system is also useful in determining the best crossover points. Listening is also required to determine if the system is functioning correctly with more dynamic material using the crossover settings chosen. Following a blind procedure based on a few measurements from the seating position and adjusting on the receiver alone is not going to yield optimal bass management in many cases.

Speaker levels are a basic audio setting found in all receivers. These settings are used to balance the sound coming from individual channels. Auto calibration can get these right, but they do fail to get it even reasonably close a relatively high percentage of the time. I suspect poor microphone placement and poor test signals are the primary causes of this. The errors in this are greatest with respect to the subwoofer level which is frequently set so low that the automatic on circuit does not work properly. It is very rare that the reference sound level setting determined by the auto calibration system matches the actual reference level for a recording to within 1db.

Speaker distances are the primary setting associated with phasing the subwoofer and the speakers. I find this works the best of everything in these systems. Probably because if it did not the users would easily discredit it by using a measuring tape. The other settings require equipment that they do not usually have available to verify. Dramatic errors in distance are usually an indication of a phase error that was missed by the auto calibration system.

Complex phase correction of the speaker sound is where the automated systems are strongest. It is not possible to do this manually. This technology can improve the sound quality. Unfortunately, this cannot typically be used to the exclusion of the frequency response. The only products I have seen that have this level of flexibility are the higher end Pioneer Elite receivers and the Audyssey external multichannel product. While more subtle in nature than anything else in system adjustment this is an improvement found from auto calibration routines. It is overwhelmed by the other errors if they cannot be fixed independently.

These products also promise to detect speaker and subwoofer phase errors. This appears to be hit and miss from what I see in the field. Sometimes they get it right and sometimes not. Certain products are more difficult to determine this for than others and it is tricky to do this at the seating location reliably. A better approach and one I use is to measure each woofer at the speaker itself along with a phase check at the listening position. I am not aware of any automated system that does this.

Additional audio processing options available in these products are frequently extensive and can include things like PLIIz, PLIIx, Neo6, THX, DSX, Re-EQ, Dual, Panorama, C. Image, Depth, C. Width, Lip Sync Delay, LFE Att, DRC, DNR, X-Curve, HiBitSmp, Dialogue, Midnight, Loudness and PQLS. The auto calibration software does nothing to set these yet many are set very poorly from the factory. Someone needs to go through all of the additional processing options which at times change per input and per data type. Problems produced by not getting these right include increased levels of distortion, reduced dynamic range, poor lip sync and reduced sound clarity.

Listener preference is another area where these packages are very weak. I frequently alter the settings from reference based on the following situations and I have encountered no automated system that requests user information in these areas before proceeding:

• Listener hearing deficiencies
• Listener usage at lower than reference volume levels
• Equipment cannot handle the power in certain frequency ranges at reference SPL levels (most common at lowest and highest frequencies). Software that does not honor this can damage equipment. I encounter blown tweeters from software boosting treble too much as an example. Doing this well requires knowledge of the power levels required for specific speakers to hit different SPL levels at the seating positions.

Sources also need audio settings to be set correctly for the system to sound it’s best. These automated systems offer no guidance here, but almost all cable, satellite and Blu-Ray players are not setup to deliver the highest quality data to your receiver making any receiver of much less benefit than possible.

When a system is setup correctly you will get the best sound from your surround system possible. This is a very important thing and when done well the sound system will tend to disappear and you are transported to another world as intended by the mix artist. At this time the best approach I have found is to do these things manually. I have done this thousands of times for clients with these automated systems with great success for less cost than most people assume. Here is a link to reviews from some of these clients. I believe the best sound will result from a combination of manual calibration, proper equipment selection and good room acoustics. A professional like myself can help with all of these to get you the best sound possible from your equipment investment. Many times I can also save people money by recommending lower cost gear that can more than offset the consulting fee. A detailed comparison of the measurement errors for one of my own systems between Audyssey and Manual calibration is shown here.