Audyssey XT32 distortion on RCA in signal, but not Airplay?

[Lattiboy]

Hello,

I have an issue (on both the Marantz 6012 and Denon 3500H) where I get a constant bass distortion from my left speaker when using Audyssey with my external DAC. I’m running it into the CD input RCAs. On both receivers!

I figured it was a line level input issue, but even after setting the source input to -10db the distortion remains. Also, if I use Airplay or other digital inputs the distortion isn’t present

To make things even weirder, when I run the DAC in “pure direct” mode there is no distortion, even at incredibly high SPLs.

I’ve attached a photo of my room correction results.

I’m running a Marantz SR6012 into two NAD 2400thx power amps, driving my NHT Classic Four speakers, being aided by two Infinity Sub R12s. The external DAC is the D1+ tube DAC from Maverick Audio.

EDIT: the distortion is present even with “L/R bypass” or Flat is selected, which makes no sense. I’ve also attached my levels post calibration.

 

[Lattiboy]

I should also add that the setup sounds great in pure direct mode, so I’m kinda confused the EQ is so intense....

 

[TLS Guy]

I should also add that the setup sounds great in pure direct mode, so I’m kinda confused the EQ is so intense....

Audyssey is good for levels and distance and nothing else.

It ruins sound quality as you have found out. NEVER use Audyssey to EQ anything. Your EQ curve is pretty typical and results in nasty harsh sound.

Just forget you ever heard of Audyssey Eq and enjoy your system.

 

[Lattiboy]

Audyssey is good for levels and distance and nothing else.

It ruins sound quality as you have found out. NEVER use Audyssey to EQ anything. Your EQ curve is pretty typical and results in nasty harsh sound.

Just forget you ever heard of Audyssey Eq and enjoy your system.

I mean, thanks for the input, but that’s not a common opinion. The bass management of Audyssey is incredible in my experience, especially in difficult rooms. I usually only apply it to sub 400Hz in the app and in the past it has done great.

 

[TLS Guy]

I mean, thanks for the input, but that’s not a common opinion. The bass management of Audyssey is incredible in my experience, especially in difficult rooms. I usually only apply it to sub 400Hz in the app and in the past it has done great.

I grant you, it may help some difficult rooms in the bass, but above about 200 Hz never. I totally agree with Billy Woodman of ATC that distant Eq of a system is not based on good acoustic physics.

 

[AcuDefTechGuy]

I totally agree with Billy Woodman of ATC that distant Eq of a system is not based on good acoustic physics.

Did he elaborate on what he said? What is "distant EQ"?

 

[Verdinut]

Did he elaborate on what he said? What is "distant EQ"?

The distant EQ is because of the current pandemic.

 

[AcuDefTechGuy]

The distant EQ is because of the current pandemic.

So the Mics need to be 6FT apart from each other too?

 

[TLS Guy]

Did he elaborate on what he said? What is "distant EQ"?

Yes, because you get a real mix of speaker problems and room modes. Nulls are pretty much impossible to deal with, and attempting it easily overloads amps and especially tweeters and can easily lead to distortion. In addition a lot of speaker irregularities are due to retained energy, and not amenable to equalization in any reasonable way. That was the gist of what we discussed on this topic on my interesting visit to Stroud, Gloucestershire.

It seems to me that Audyssey's pronounced tendency to boost HF is particularly troublesome as it is likely to cause tweeter failure. Remember every 3db in increase in power doubles the power in that pass band.

My experience of auto Eq has been uniformly bad. I have attempted it on five installations now and Audyssey has markedly reduced SQ. Its most noxious effects have been in the upper register. It does not produce a natural balance in the room at all.

Now in the studio, I had to use the mic from one of my older pre/pros, so I can not claim validity. The miserable Audyssey mic was DOA, and so far Mrantz have not been able to provide a replacement. Anyhow the mic number is the same on both. Audyssey again though produced they same type of response errors.

The point is that this room sounds absolutely superb, and measures very well. So if Audyssey was any good, it would have left well alone. Instead it mucks it up and badly.

 

[TLS Guy]

Did he elaborate on what he said? What is "distant EQ"?

It means when you have the measuring mic more than 2 meters away from the source and try to use the data for reliable equalization.

 

[lovinthehd]

The graphs aren't much to go by....what is the audible result of the distortion? I do note you have one sub at -12 which may indicate you have too high a gain set on the sub amp (or you landed exactly on the max amount the avr can reduce level). Odd that the same thing results with two different units, that would point to the source to me. Using several units with Audyssey, not had such an issue but I don't use external dacs either.

 

[AcuDefTechGuy]

Yes, because you get a real mix of speaker problems and room modes. Nulls are pretty much impossible to deal with, and attempting it easily overloads amps and especially tweeters and can easily lead to distortion. In addition a lot of speaker irregularities are due to retained energy, and not amenable to equalization in any reasonable way. That was the gist of what we discussed on this topic on my interesting visit to Stroud, Gloucestershire.

It seems to me that Audyssey's pronounced tendency to boost HF is particularly troublesome as it is likely to cause tweeter failure. Remember every 3db in increase in power doubles the power in that pass band.

My experience of auto Eq has been uniformly bad. I have attempted it on five installations now and Audyssey has markedly reduced SQ. Its most noxious effects have been in the upper register. It does not produce a natural balance in the room at all.

Now in the studio, I had to use the mic from one of my older pre/pros, so I can not claim validity. The miserable Audyssey mic was DOA, and so far Mrantz have not been able to provide a replacement. Anyhow the mic number is the same on both. Audyssey again though produced they same type of response errors.

The point is that this room sounds absolutely superb, and measures very well. So if Audyssey was any good, it would have left well alone. Instead it mucks it up and badly.

So even though the frequency response graphs produced by the auto EQ look good, something else is amiss that’s not showing on any graphs?

I have heard a few different auto EQ, and I never thought any of them sounded good, but I cannot explain why since the frequency responses look good.

 

[TLS Guy]

So even though the frequency response graphs produced by the auto EQ look good, something else is amiss that’s not showing on any graphs?

I have heard a few different auto EQ, and I never thought any of them sounded good, but I cannot explain why since the frequency responses look good.

Looking good is a big part of the problem.

As you move away from a source be it live musicians or a speaker, then the proportion of reflected versus direct sound increases in favor of the reflected sound.

Reflected sound however has a lower frequency content than direct sound. So there is a natural HF attenuation. So there should be HF roll off as you move away from the speaker. If you correct for that effect the sound will be harsh and unbalanced.

That might sound superficially good for close multi miked pop music, but for natural instruments, in the concert hall, recital hall, opera house or church it is disastrous.

Incidentally this also drives home the point that listening panels prefer wide dispersion speakers, whose off axis response mirrors the axis response but with some smooth HF roll off, of axis.

Let me just illustrate the point.

Here is the FR of a main speaker at its current location at 2 meters.

The droop above 15 KHz is from omnimic.

Now the "sub/LFE"ouput is blended in at 40 Hz. Note that there is slight roll off and you will see why below.

Here is the FR of the center at 2 meters in its current location. It is rolling off 12 db per octave at its calculated F3 of 48 Hz.

Now lets see the room response.

First row. 12 ft back from center speaker. These results are with the front three and surrounds.

HF decline is starting at 6 KHz. You can not time the speakers for all seats and the impulse response shows that.

Now lets look at the second row, MLP.

Note that the speakers are pretty much perfectly timed for the MLP. HF roll off is now starting at 4.5 KHz. There is slight LF rise starting at 30 Hz.

So that position gives a good rendition of a high priced seat in the concert hall.

Now lets look at the third row.

Like the frontrow, the speakers are not perfectly timed for that position. The HF roll off is steeper. Now there is stating to be significant rise below 50 Hz. This is to be expected given that the rear seats are about 3 ft from the back.

However you can see why I elected to mix the 40 Hz sub/LFE output the way I did. It also shows why you have to be careful not to turn subs up too high.

The room is 29 ft. long, and 16 ft wide with 9 ft ceiling.

So you see you have to be very careful correcting FRs at any seated position.

 

[TheWarrior]

Audyssey manipulates frequency at the expense of phase. I think someone even asked the lauded Chris K. that exact question and his response was "thats why I created Audyssey..."

At low frequencies the room controls the response due to such large wavelengths being produced between parallel walls. Mapping out Room Modes shows the correlation of physical dimensions to measured response. Getting bass right means employing enough subwoofers to ensure all listening positions are as close to each other in measured response as is realistically possible. Budget and ability to position and/or hide all of these subs is usually the limiting factor.

As mentioned above, dips cannot be compensated for with DSP, yet Audyssey makes them disappear.

However, Audyssey does not in any way influence Room Modes - how could it? It has no idea what size room it is in. Therefore it is modifying the sound to meet a 'standardized' room curve and is adept at modifying the signal to measure as smoothly as possible.

If you looked at any response measurements from the side, you would see more of a spiral with a rise and fall in amplitude for any given frequency allowed to sound out its entire cycle time. And that is where Audyssey performs its 'magic'. It manipulates that cycle to cancel out peaks and dips to conform to its standardized room curve.

That is not in any way conducive to accurate reproduction.