VSX-72TXVi/VSX-74TXVi Surround Sound Calibration

[timn99]

Who has the above Pioneer Elite receivers, and has calibrated their 5.1 surround with a Radio Shack SPL meter. Just wanted to see if I had the right approach.

To get started, I first did the Auto MCAAC calibration with the internal test tones and all speakers were set to "Large" by the receiver. It came out with the channel levels, speaker distance, standing wave set to "ON", and Acoustic Calibration EQ settings. Speaker distance was pretty much spot on as I verified with tape measurement. Since I'm still waiting on my SVS PB12+ sub, I reset fronts to Large and everything else to small. Also since I read its better to used the full bandwidth pink noise tones in AVIA, I then played the AVIA tones with volume set to reference (0 dB) and adjusted the channel levels to 85dB reading on the SPL meter. This was done by hitting the channel level button on the remote, which toggles between each speaker and adjusting the gain accordingly. For kicks with my AVIA-adjusted channel levels, I played the receiver internal test tones again for each speaker and it seems like the SPL readings for the internal test tones are about 10-12dB lower (reading of about 73db on SPL meter). Is this expected? Did I miss anything, or is there anything else I should do?

 

[MDS]

The test tones on AVIA are at -20 dB whereas the receiver's internal test tones are at -30 dB (THX standard) and that accounts for the difference. Although the level of the tones on AVIA is different, it is the exact same pink noise as the receiver's internal test tones.

 

[timn99]

This is where I saw a discussion of using the AVIA test tones versus the receivers internal test tones. Any thoughts?

http://www.soundandvisionmag.com/idealbb/view.asp?topicID=37023

 

[MDS]

I only read the first page, but I think the main author (SoundHound) gives conflicting information.

- He says the test tones on a receiver are 'filtered' and only contain one octave of pink noise around 1 kHz. That would mean it only contains frequencies from 500 Hz (one octave below) to 2 kHz (one octave above). I don't quite follow that because it is not the definition of pink noise. Pink noise is full bandwith random noise with the characteristic that each octave over the entire range is at an equal amplitude. As far as I know, all receivers follow the THX recommendation and use full bandwidth pink noise measured using the Long Term A Weighted average.

- He says to use the A weighting on the SPL meter because it makes the meter more sensitive to the mid frequencies. That is backwards. The C weighting makes the meter more sensitive to the mids because it more closely matches human hearing - we are not as sensitive to changes in amplitude at very low and very high frequencies.

- He says to calibrate with the sub off because the receiver's bass managment will route frequencies below the xover to the sub. Well, if you are going to use a sub, you want calibration to be done with the sub in play. Besides, AVIA's LFE test track plays the tone in both the fronts and the sub because that is how you will be using it and you want to calibrate for a seamless transition from the mains to the sub - not calibrate in isolation and then after the fact calibrate the sub. This recommendation was to avoid having the other channels too high or low but that is exactly what you will get if you calibrate one way with A weighting and sub off and then switch to C weighting with the sub on.

- He makes the common mistake of saying that 'reference level' is the level at which the mastering engineer intended it to be heard. Reference Level is defined by Dolby as 105 dB peaks at the listening level and to arrive at that level you use a -20 dB full bandwidth pink noise signal and adjust the levels so that the meter reads 85 dB (85+20=105).

BUT, reference level can be anything you want. It is simply a level from which everything else is relative. If you calibrate to Dolby Reference Level at 0 dB on the volume dial, then when the dial reads -10 dB you are 10 dB below reference. If you decide you want 0 dB to be 75 dB at 0dB on the dial, then -10 dB on the dial is still 10 dB below 'reference'.

The recommended way to calibrate from Dolby and THX and practically anyone else you will read is to use C weighting, Slow response and calibrate to a level of your choosing - 105 dB if you want to match Dolby reference level or any other number you want.

Note: The AVIA narrative suggests using 75 dB as the target. Given that the tones are at -20 dB (per Dolby standards) you would need to hit 85 dB to get Dolby Reference Level. They suggest 75 dB only because for a small HT room, real Dolby Reference Level is extremly loud. If you were to use the receiver tones or the DVE disc, you would have to target 65 dB to match the AVIA suggestion because those tones are at -30 dB.

Also be aware that you only get those SPLs when the input signal averages -20 dB or -30 dB (whichever tone you used). Play a modern hyper-compressed CD where the average level is closer to -10 dB and it will be MUCH louder.

 

[timn99]

MDS....thanks for your very insightful response to the thread I mentioned. It does seem to me that many posters and sometimes even speaker manufacturer always talk about calibrating with the RS SPL, and many times the AVIA is mentioned for use. Are they just assuming that most people's receiver don't have internal pink noise test tones?

 

[MDS]

Like any other topic, there are arguments for and against one approach vs another.

In favor of AVIA
- The tones match the Dolby recommended test tones (-20 dB full bandwidth pink noise).
- AVIA has other audio tests that are useful such as checking phase of the speakers, sweeps to check frequency response, etc.
- AVIA plays the LFE in both the sub and mains when calibrating the subwoofer channel, theoretically offering a better match for what you will actually hear when playing a real DVD.

Against AVIA
- Using a dvd with test tones, some will argue, really only optimizes the calibration for playing DVDs because the dvd player itself may subtly influence the sound.
- The average level of dialog on DVDs is -31 dB, so you would be better off using the internal test tones which are at -30 dB (or Digital Video Essentials, which is the same).
- Playing the LFE in both the sub and mains at the same time masks the true level of the sub because the mains contribute to the level. DVE does not do that. The AVIA site has an explanation as to why they chose their approach of playing the LFE in both the sub and mains.

I have AVIA and DVE and have used both. The last time I recalibrated was when I moved to a house and I just used the internal test tones. Although there are good arguments on both sides, IMO it's really much ado about nothing. As long as you get each channel reasonably close in level, calibration will be beneficial regardless of which approach you use. The internal test tones are just more convenient to use.