Voices sometimes have a "rattle" quality to them (1 Viewer)

[chris_mitchell]

The audio part of my home theater system is:

Pioneer Elite DV-37 Progressive Scan DVD player
Denon AVR-3802 A/V Digital Dolby receiver
Boston Acoustics MicroSystem 9500

Often when watching DVDs, especially older ones (but not necessarily older ones), the voices from my center channel speaker have a ringing, sort of rattle quality about them, especially for higher pitched voices. I rarely hear this when watching TV (RCA DS4220RE Digital Satellite Receiver), but I do hear it sometimes on CNN. I had noticed the same problem on my previous mid-fi set-up (Sony electronics, Polk Audio speakers). I have the Cinema EQ turned on in my receiver to reduce brightness in the sound, but I don't know what else to do. Is it a problem with my settings somewhere or are my speakers just poor quality? Any help is greatly appreciated.

Chris

 

[Neil Joseph]

Do you hear it on certain DVD's only, and always in the same spot? The Fifth Element would be an example of this. It has to do with the DD compression.

 

[Vince Maskeeper]

Chris,

The truth is this comes up relatively often, and so far it's been tough to offer much in the line of a definitive answer.

As I'm sure you realize, audio in these productions pass through about a dozen stages between the natural creation on set and the final reproduction in your home. In that process- if at any point the audio signal exceeds the tolerances of the system, it will become distorted slightly (sometimes referred to as "clipping" or "overmodulation").

On some soundtracks I've found that this "edgy" sound in dialog is absolutely on the source material- likely overmodulated when being recorded (since the mics they use in these situations are very sensitive- often a quick peak in the voice can overload the element itself- or such a peak could overload the recording device, the preamp, etc)-- or overmodulated in processing (an analog effect or digital plug in is exceeded slightly and introduces a slight harmonic distortion). On these types of tracks, the ditortion is repeatable- and heard on any and all systems- I've gone so far as to "rip" ac3 tracks direct off DVDs and check them to find the distortion in the raw track itself.

The problem is, once a piece is overmodulated- there is no fix for it. Even reducing the volume after the fact, the material remains distorted. If it was the recording process that was the source, there is no way to repair it besides looping the dialog (replacing it with a dub later).

In the older days of audio production- with the limited dynamic range of some of the tape formats used for on-set audio capture- engineers were required to maintain a pretty hefty signal level to overcome the noisefloor associated with tape-- while leaving enough headroom to prevent clipping. So, it's not too surprising to find older tracks getting a little edgy when the voices onset got a little loud (heck, in the music recording world this was seen as an effect- often called TAPE SATURATION, and is sometimes credited as the source of the "analog" sound some people prefer). I really think slight tape distortion was considered an acceptible evil of the era...


But on other DVD soundtracks, I hear this edginess on some systems, and not on others-- leading me to think that the distortion is not in the source track itelf, but somewhere in the signal chain of the playback device. Headroom on audio converters, freq response of the amplifier device, and possible physical limitations of the speakers themselves are all additional possible causes of distortion in the playback stage.

So, the short answer is: there is not one definitive answer. It seems lower end systems are plagued by distortions instroduced by the components themselves, while higher end systems are more revealing of limitations of the source elements. Sort of a catch 22.

I'd love to see someone from Dolby do some serious research into these distortions in vocal tracks and find out exactly what the most common sources are- since it really is an issue that seems to be raised monthly around here.

IF you have some tracks and passages specifically in mind- feel free to post, and I'm sure someone could offer some feedback on what they hear in their system during those tracks.

-Vince

 

[chris_mitchell]

Thx, Vince, this was very helpful - at least I know it's not *necessarily* my set-up. Funny, but none of the movies we watched this long weekend had this problem, as I was going to post on a DVD that did and see if others around here hear it too )
As soon as I find an offending DVD I'll post again and see if others have a similar experience.
Chris