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Yamaha RX-Z9 Auto Set-Up and YPAO Configuration

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What good would Yamaha be if their latest technological achievement in receivers didn't explore the latest fashionable craze in automatic setup and room correction? Only a few years ago it was difficult to affordably acquire the processing power to take on such a feat. Today, Yamaha is implementing this on mid-fi level receivers starting at only $600. As I learned during my review of the RX-V2400 , these type of systems are far from being infallible and leave much to be desired.

However, they do have merit for users who don't want to spend hours fussing with the setup configuration and tweaking of their systems and instead opt for a quick one-button solution to give them reasonably accurate results - and more importantly sound output from all channels.

However, I caution all users of such systems to take the time, and evaluate how your system ends up being configured to determine if the results make sense for your particular set-up and listening preferences. This is especially important when considering how the PEQ or equivalent auto room equalizer tailors the response of your speakers to achieve what it believes to be the flattest or most accurate frequency response.

I began as instructed in Yamaha's rather lengthy, but easily digestible, Users Manual. I placed the supplied microphone (which appeared to be a beefed up version of the one found on the RX-V2400) at the primary listening position of my home theater room and engaged the "Auto Set-Up" feature.

Wiring Check

The RX-Z9 had no problems passing the wiring check for my system. However, I caution installers to interpret negative results with a grain of salt. Complexity of room dynamics and/or some loudspeakers unique crossover/driver arrangements, can trick this system into reporting speakers as being wired out of phase when in fact they are not. If it should report any of your speakers are out of phase, first check the wiring and then use the Avia or equivalent home theater set-up disc, to audibly confirm the proper phase of each channel. This is a good measure to practice on any home theater install regardless if the device has the built in ability to check it for you or not.

Distance Check

The auto set-up did a commendable job at setting the distances of each speaker from my listening position, except the subwoofers. Yamaha informed me that it is accurate within 1/10 th of a foot, and user adjustable is 1/10 th ft step sizes. This is more accuracy that is needed in home theater and certainly more precision than found in many higher priced exotic processors. Automatically detecting subwoofer distances is a challenge given the large wavelengths in question and the complexity of room dynamics. I recommend using the RX-Z9's distance checker to properly set all nine speakers in the system, and tweak the subwoofer distances if needed. Having this feature proved very useful in setting my speaker distances, especially those front effect channels that were out of reach for me to measure manually.

Size Check

clip_image002temp_002_003.jpg Based on my experience with the RX-V2400, I was a bit concerned that the RX-Z9 would have the same problems identifying the size of my speakers. However, to my surprise, the RX-Z9 correctly identified all of my speakers as "small" the first couple of times I tested this feature. This was good news as it correctly diverted the bass from all channels to my dedicated subwoofers for proper bass integration and preservation of system dynamics both for the loudspeakers (avoid them trying to produce frequencies they aren't capable of producing) and amplifier power. However, moving the microphone a few feet back from my listening position yielded different results. By repositioning the microphone back just a few feet from my listening position, I achieved completely different, and in my opinion, unpalatable results. The Auto setup now identified all of my speakers as small except for my surrounds. It also set the crossover way too high at 200Hz. I believe the microphone was being duped into thinking my rear speakers were large because of boundary gain effects of my rear speakers due to close proximity to the rear walls. Incidentally, after the first time the RX-Z9 identified my rear speakers as "large", it also insisted on a 200Hz crossover setting. I had to manually set all speakers to "small" and adjust the crossover setting to a more appropriate one that suited my speakers and listening preferences.

YPAO (Yamaha Parametric Room Acoustic Optimizer)

One of the distinguishing features of the RX-Z9 is its inclusion of Yamaha's YPAO automatic parametric active room correction equalizer. Unlike many of the first generation receivers implementing room correction, the Yamaha YPAO system is comprised of a ten band parametric equalize which adjusts level, frequency, and Q factor. Graphical equalizers adjust only amplitude response at fixed frequency bands, thus are not an effective tool for room correction at all in my opinion. Yamaha does offer a graphical equalizer as a programmable user option for every channel for additional fine tuning of your system's response in case you wish to forgo the YPAO system.

The YPAO "Equalizing" feature of the receiver allows for several equalizing options:

Front

Applies equalization to all channels, except the mains, to attempt to achieve closest tonal response to the main channels.

Flat

Applies equalization to all channels to attempt to achieve flat response.

Low

Applies equalization to all channels with emphasis on low frequencies.

Mid

Applies equalization to all channels with emphasis on mid frequencies.

High

Applies equalization to all channels with emphasis on high frequencies.

Yamaha YPAO Operational Details

Operation Frequency: 63Hz - 16Hz 1/3 Octave resolution
Qfactor: .5 - 10
Level:
-20dB to +6dB +/-.5dB increments
Frequency Bands:
10 bands per channel, 2 sub bands for a whopping total of 94 bands!

The RX-Z9 utilizes a total of eight (8) 32bit processors, and reserves four (4) of them for YPAO!

It is important to note that the microphone used for the RX-Z9 is specifically calibrated to work with the internal microphone preamp within the RX-Z9. It is not advisable to use an aftermarket microphone (even if of higher quality) or even the supplied microphone of another model Yamaha receiver (IE. RX-V1400/2400) with this unit .

Note : In order to toggle PEQ on/off in the OSD you must enter the "Basic Sound" menu and select "Graphic EQ". Yamaha claims this will be updated in future products to be more intuitive.

Not enough tone controls? You can engage PEQ, Cinema EQ and Tone Controls simultaneously!

A Note About the YPAO Yamaha Room Correction System

The YPAO system uses pink noise sweeps to map the response of the room at the listening position for each speaker. Pink noise delivers constant power per octave and the YPAO attempts to equalize the magnitude response accordingly. However, in attempting to achieve a "Flat" frequency response, this can have deleterious affects on impulse response and also reduce dynamic headroom in the amplifier if certain frequencies are boosted as opposed to being attenuated. If for example, the YPAO equalizes a +6dB gain centered around 3kHz, then the amplifier would be tasked to produce up to four times the power for that frequency band, thus reducing headroom and potentially causing compression, and/or distortion. Additionally, if the YPAO system attempts to compensate for a speaker deficiency by creating a boost because of improper crossover design and/or some other speaker anomaly or strange impedance characteristic, when coupled to an amplifier this can actually create a dangerous effect as it can potentially drive some amplifiers into oscillation when boosting under these circumstances. However, if the speaker is flat in performance and the amplifier is not taxed at the frequencies being boosted, then the this scenario is unlikely to occur, with the only possible penalty of compensating for the direct sound of the speakers as opposed to resolving a deficiency in ambient or reflected energy in the room. Ideally, these mid and high frequency issues should be dealt with at the source, namely the room (assuming the speaker and amplifiers are designed correctly).

If you consider the basic relationship of sound and propagation through air given the following formula:

l = v / f (where v = velocity (speed of sound =1140 ft/s STP and f = frequency (Hz) )

then we see the wavelength of sound for 63Hz = 18 ft and for 16kHz = .86 inches!

Thus altering high frequency room response will affect only a very small listening area above a couple of hundred Hertz. High frequency harmonics are generally close together, if not overlapping, and their corresponding intensities are far less than the fundamental, making them more dependent on listening position. Another issue to consider with high frequency room correction is that the measuring microphone may not accurately measure direct to reflected sound. The goal of room correction is to correct for room anomalies, not the loudspeakers (again assuming the loudspeakers are of sound design). Altering the frequency response of the loudspeakers in this fashion changes the direct sound to compensate for a deficiency in the ambient or reflected sound field caused by the room. This may in fact alter the direct to reflected sound at the listening position further deteriorating imaging of the loudspeaker and corrupting the critical first arrival of sound. Ideally active room correction would best be applied at frequencies below 200Hz where sound is more difficult for the listener to localize and where room modes are difficult to resolve with room treatments. Utilizing a more precise parametric equalizer may be applied to analyze room modes to construct notch filters to reduce the excessive room decay times (RT60- # of milliseconds it takes for a sound to decay by 60dB).

Alternatively, a point to consider is that some room correction systems actually do address speaker non-linearities as well as room interaction affects. The problem is that most systems are not able to distinguish between the non-linearities of the speaker versus the non-linearities induced by the room. In some cases in may not really matter. For instance, in the bass frequencies smoothing out the response may involve changing phase and gain at certain frequencies. As long as the correction is made for the listening position we probably don't care how much of the problem is speaker or room related. For that matter, I can understand why the Yamaha YPAO system does not attempt correction at very low frequencies. It would take much more reserve power than the receiver is capable of delivering. In this respect limiting the correction to a moderately low frequency is understandable and in fact quite necessary. Of course that doesn't change the fact that we would all like compensation down to the very lowest frequencies. Practically speaking Yamaha could NOT put a correction filter on the LFE output because the power necessary for correction would way overtax most subwoofers (amplifier and driver excursion). It may however behoove Yamaha to introduce their own active servo subwoofer integrating low frequency room correction with a system much like many of Velodyne's Digital Series latest product offerings. A system that initially measures near field power response of the speaker as well as impulse response and then takes into consideration a measurement which showed room decay time would probably make for an even more accurate correction system. Now if only a manufacturer would build such a system affordably :-)

 

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