Dolby effecting the HF when checking mixes

Discussion in 'Mastering' started by Terrapin, Oct 13, 2009.

  1. Terrapin

    Terrapin Guest

    Hi All,

    So I've hit a roadblock thats really been getting me down, hoping someone can shed some light on the situation.

    I've been taking my mixes and checking how they sound on various systems other than studio monitors; ipod, home far all seem in the ballpark. Then I get to my car stereo. Upon first listen they seem okay and then I hit the little Dolby NR button on the tape deck that my ipod is plugged into and voila, I loose like 6db of everything above 4k! Good bye cymbals and some vocal clarity. When I listen to commercial albums on the same system and hit the Dolby button nothing happens, all high frequency information is retained.

    Do commercial releases go through some step during mastering that adjusts for this or do my mixes need some serious tweaking?

    Thank you!!
  2. hueseph

    hueseph Well-Known Member

    Oct 31, 2005
    Vancouver, BC, Canada
    Wow Dolby. People still use that? I thought a track needed to be encoded with Dolby before you could use the button for playback. I don't know. It's been a long time since I've had to consider using it.
  3. Terrapin

    Terrapin Guest

    I had the same thoughts about Dolby, confuses me as to why it kills all the high frequency on my mixes but not on commercials mixes.
  4. Massive Mastering

    Massive Mastering Well-Known Member

    Jul 18, 2004
    Chicago area, IL, USA
    Home Page:
    The tapes in question were probably encoded with Dolby. It's not a one-way street...

    Cassette tapes? Wow...
  5. RemyRAD

    RemyRAD Member

    Sep 26, 2005
    OK, here is what is happening.

    The reason why your commercial recordings sound OK is because they are mastered at a very hot level. Dolby B is a "dynamic" noise reduction system. And it first requires that the recording be encoded. But if it's not encoded and it is of a very high-level, the Dolby is not reducing any of the high frequencies. It starts to reduce the high frequencies at lower volume levels which is what you're dealing with. So you shouldn't be pressing the Dolby button. Back in the day, we used to have a little saying. We would look in our magic romper room mirror and say "Do be a good bee. Don't bee a Dolby." Saying that while clicking your heels together and simultaneously chanting, "I want to go home". Then you turn the volume up loud. So if it sounds OK with the Dolby off, you're golden. Then go out and pay a nice mastering engineer. You're good. Everything is good.

    Dolby = bad
    Mx. Remy Ann David
  6. Terrapin

    Terrapin Guest

    Remy, thank you very much, great answer!! Makes sense with dolby wanting to take out the low level hiss. I will trudge forth with confidence!

    Massive, I'm not actually using a cassette tape just one of those tape adapters so I can play the tracks from an ipod in my car. Although I still do pull out the old box of tapes once in awhile! :)
  7. niclaus

    niclaus Active Member

    Dec 28, 2007
    Paris, France
    I guess you are talking about the music industry, because, in the movie business, Dolby has helped improved the sound quality very much....
    Dolby SR works pretty well... But yeah, that's if everything was done properly and you still have the reference signal and everything.....

    But, again, i guess you were talking about the music business.

  8. Kapt.Krunch

    Kapt.Krunch Well-Known Member

    Nov 21, 2005
    Couple things missing here.

    First of all, I wasn't aware that a car tape deck/radio's Dolby circuit affected anything except the tape playback. In other words, FM doesn't go through the Dolby circuitry, only the tape does. Pressing Dolby on or off will certainly have no effect on FM. Right?

    You said you were listening on home stereos and iPods, and then your car. The same media? iPods don't play tapes. Are you comparing MP3s for the iPods, to CDs for the home stereo, to cassette tapes for the car?

    IF the tape deck has auxiliary inputs for iPods, etc., that circuitry wouldn't run through the Dolby. I doubt anything that still has a cassette has auxiliary inputs.

    This leads me to believe you may be using one of those 1/8" mini jacks to cassette shell adapters, and playing a portable CD, or the iPod, through the cassette are trying to listen to a cassette version through that system.

    If it's a cassette tape you're actually listening to, did you encode it with the same Dolby (B, C, ?) that the tape deck is decoding? If not, then yes, it's going to greatly attenuate the highs and make everything sound muffled. In a nutshell, Dolby encodes by boosting certain frequencies, and then attenuating those frequencies upon playback with the same Dolby scheme engaged. So, while the amount of actual tape hiss hasn't changed, the frequencies of the recorded material have gotten boosted, and when decoded, the recorded material frequencies came back to where they are supposed to be. At the same time, the tape hiss that is inherently present on a tape moving past heads have also been attentuated. Signal back to where it belongs, tape hiss reduced. Playing non-encoded tapes attenuates the highs, because they haven't been boosted. Playing encoded tapes with Dolby turned off will sound brighter, and normal hiss will be present.

    If you are playing an iPod through an adapter, then tape hiss is not an issue, so you don't need Dolby. keep in mind, though, that a cassette deck has a lower high-frequency limit than digital (maybe 15KHz on a good one), so it may attentuate your highs a bit, also.

    And, levels of different media will also reveal differences. You're comparing apples to oranges.


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