SH Spotlight Golden age of music: The difference between an analog compressor and analog limiter

Discussion in 'Music Corner' started by Steve Hoffman, Apr 2, 2007.

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  1. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    A music celeb. that I am helping get his catalog in order candidly asked me the above question (after not getting a straight answer after 40 years of recording.)

    I'll be happy to start it going but the real experts (Jamie, Barry, etc.) can continue on from there.

    I have stated in print many times that the analog Compressor/Limiter has to be the MOST MISUNDERSTOOD electronic device in recording/mixing/mastering. It's an essential device; most music could not be recorded without one, especially in the 20th Century. I won't bore you with what is inside the boxes (although that's pretty interesting).

    Here goes. Starting in 1925 with the development of the Western Electric System of electronic recording to wax disk (and later, around 1949, to magnetic tape), recordings needed to be "limited" so the instruments would stay in the same "space" with each other and also to keep the recording needle on the groove.

    There were (are) two ways to approach this, each valid, each used a heck of a lot in the history of recording. Probably 99.9% of all pop and classical recordings use some type of limiter/compressor in the circuit. Even the famous RCA-Victor "Living Stereo" recordings in the 1950's and the Mercury "Living Presence" recordings as well (Surprised?)

    So, there are two ways to do it.

    First: Compression.

    In the olden days, a compressor was called a leveling amplifier or optical compressor. It's purpose was to reduce or manage dynamic range. It would bring the dynamics of a performance down to a reasonable level for disk cutting (usually 20-30 db of dynamic range down from 100 or so depending on the music). This was needed to keep the music "above the noise and below the skipping point" of old phonograph records, both 78 and vinyl and the distortion point of analog tape machines and recording gear.

    Here is what I use and love, the Teletronix LA-2A Leveling Amplifier. See picture below. With the switch set to "compress", it is ALWAYS WORKING IN THE CIRCUIT and adds a distinctive flavor to the music as it works to smooth out the mix. You've heard this sound on many of your favorite records. Bill Porter's Roy Orbison and Elvis in Nashville recordings or anything from that studio in the Golden Age uses one as does almost every recording from the 1920's to the 1970's including everything from United/Western including all Beach Boys, Sinatra, Jan & Dean, etc.. It fools you because when used correctly, you are not even aware it's in the system at all. It's a truly magic machine.

    Second: LIMITING.

    This is a device that in the pure sense, does not interfere with the music until it hits a certain level in volume and then clamps down, hard. It "releases" the music at the rate you tell it to, sometimes leaving a drop in volume. It "limits" the sound from getting any louder and pushes down the music to keep it in place. You've heard this on albums like REVOLVER, etc. It's obvious when it's working and can be used (as the Beatles used it) as an effect as well as for the main purpose of keeping the needle in the groove. It was invented for broadcast use a loooong time ago to make sure the station did not overmodulate. Considered too "unmusical" for actual recording, over the years it's gained favor. When used correctly (to keep the occasional peak from wrecking a mix but otherwise preserving the original dynamic range of the recording) it works but we can always HEAR IT WORK.

    The famous Urei 1176:


    In the 1970's Bill Putnam's Universal Audio 1176LN solid state limiter/compressor blurred the line between a compressor and a limiter. You hear it used on almost all rock, pop, jazz and classical music from the 1970's and on into the 1990's. It's probably the most used compressor in recorded music. Many engineers still use it to record. I've always found it a bit unmusical but one can't have everything...

    So, any questions or comments, please. Do we understand the difference now?

    http://www.uaudio.com/products/analog/LA-2A/index.html

    The LA-2A and the 1176LN, below.
     

    Attached Files:

  2. Sean Keane

    Sean Keane Pre-Mono record collector In Memoriam

    Has one or the other (or both) always played a role in modern recording of pop music? Also, can a well recorded recording sound smooth and full without the use of either?
     
  3. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Reread my post, carefully!:)
     
  4. Sean Keane

    Sean Keane Pre-Mono record collector In Memoriam

    Okay. But why can't sound just be captured on tape and not have to go through this?
     
  5. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    As I wrote above:

    A compressor was called a leveling amplifier. It's purpose was to reduce or manage dynamic range. It would bring the dynamics of a performance down to a reasonable level for disk cutting (usually 20-30 db of dynamic range down from 100 or so depending on the music). This was needed to keep the music "above the noise and below the skipping point" of old phonograph records, both 78 and vinyl and the distortion point of analog tape machines and recording gear.
     
  6. Sean Keane

    Sean Keane Pre-Mono record collector In Memoriam

    Okay, sorry. I read it pretty fast. So if the CD were around fifty years ago and disc cutting never came into play, would there then never have been the need for a limiter or compressor? If so, The Beatles would have sounded quite a bit different, eh?
     
  7. Grant

    Grant In holiday HELL

    Location:
    United States
    Reread the post sloooooowly!;)
     
  8. David R. Modny

    David R. Modny Senior Member

    Location:
    Streetsboro, Ohio
    I'll always remember an amusing story that Stephen Barncard once wrote regarding the recording of Almost Cut My Hair during the Deja Vu sessions. Perhaps, it's from the box set notes.

    Basically, to paraphrase, he mentioned that the sessions were fairly spontaneous and that he barely managed to patch the Limiter into the chain --- while the live take was *already* going -- a hair before Crosby let loose with one of those big vocal peaks!

    EDIT: It was actually Bill Halverson that did the actual patch - Barncard was an observer. I found the original text and attribution.
     
  9. Sean Keane

    Sean Keane Pre-Mono record collector In Memoriam

    If it brings the dynamics down by that much, then how can a vinyl record ever compete with real-live dynamic range? I keep reading on this forum that vinyl sounds way better, but CDs don't have to have their mastertape's dynamic range cut that much, if at all (I don't know).
     
  10. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    So we understand the difference between COMPRESSION and LIMITING now, right?

    :)
     
  11. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Great story!
     
  12. bhazen

    bhazen Beatles Forever

    Location:
    Newport Hills, WA
    I do now, but reserve the right to confuse/conflate the two in future.
     
  13. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    Of course.

    This is information that the average music lover doesn't need (or want) to know. But for those of you who are interested in what makes your favorite recordings sound the way they do, here ya go...
     
  14. Lord Hawthorne

    Lord Hawthorne Currently Untitled

    Location:
    Portland, Oregon
    You are not casting pearls before swine, Steve. Thanks for the tutorial.
     
  15. David R. Modny

    David R. Modny Senior Member

    Location:
    Streetsboro, Ohio
    In relation to the broadcast application of limiters/compressors:

    I'll just add that many commercial analog VTR's from days gone by -- workhorses like the old 3/4 inch Sony 5600 for example -- have a user switchable limiter built right into the machine.

    And, for that matter, any AGC (i.e. Auto Gain Control) circuit that one is likely to find on a consumer VCR (for auto level setting of audio) is simply a "down 'n' dirty" form of a fixed limiter and/or compressor...depending on how it's implemented.
     
  16. Metralla

    Metralla Joined Jan 13, 2002

    Location:
    San Jose, CA
    But what does it actually do?
     
  17. Steve Hoffman

    Steve Hoffman Your host Your Host Thread Starter

    From my first post:


    A compressor is also called a leveling amplifier or optical compressor. It's purpose is to reduce or manage dynamic range. It would bring the dynamics of a performance down to a reasonable level for disk cutting (usually 20-30 db of dynamic range down from 100 or so depending on the music). This was needed to keep the music "above the noise and below the skipping point" of old phonograph records, both 78 and vinyl and the distortion point of analog tape machines and recording gear. It is ALWAYS WORKING IN THE CIRCUIT and adds a distinctive flavor to the music as it works to smooth out the mix. You've heard this sound on many of your favorite records. Bill Porter's Roy Orbison and Elvis in Nashville recordings or anything from that studio in the Golden Age uses one as does almost every recording from the 1920's to the 1970's including everything from United/Western including all Beach Boys, Sinatra, Jan & Dean, etc.. It fools you because when used correctly, you are not even aware it's in the system at all. It's a truly magic machine.


    Of course, I use it in recording and mixing, never in actual mastering.
     
  18. apileocole

    apileocole Lush Life Gort

    Here's some rambling which kinda runs together and might be crashingly dull to read for all I know, but might help a "layperson" (like me) to wrap their heads around the uses of compression and limiting in recording. This might all sound pretty silly to a pro.

    It's been possible for a long time to record the whole audible range of anything including a full symphony and to play it back at real life levels. But for aesthetic or artistic pleasures, comfort and other practical reasons, sometimes volume ranges and volumes of a sound in relation to another sound need to be manipulated. That's where compression and limiting come in. You have peaks (the absolute top volume point) where limiting plays more of a hand, and dynamics (a relative thing - the volume of one sound in relation to itself and/or in relation to another sound, while dynamic range can describe the difference between the loudest and softest sounds) where compression plays more of a hand. And there are a few other factors.

    To some extent, in many practical recording environments, we might argue that some compression and/or limiting is a kind of compensation. In person, in a natural unamplified acoustic environment, you will probably have no problems hearing the individual instruments in a symphony orchestra no matter how loud one was compared to another. In recordings, for whatever reasons, things can get indistinct, particularly softer sounds getting lost against louder sounds. You could try mic'ing everything separate, but not only are there limits to how practical or desirable that is, you're just adding many pickups each with the same concerns.

    Mics aren't human ears. I've had it related to me - if the opinion and my recollections are accurate - that most microphones in practical usage do not seem to have the same depth/distance sensitivities as human hearing. Volume seems to drop away at an "unnaturally" progressive rate the further something is from a mic. In order to "pull things up" into a pleasing distance and relation to each other, you have to reduce the volume differences, aka the dynamics, preferably without losing the desired depth and range. Imagine the effects this has on the point discussed above.

    A Telarc CD (any classical title of theirs), with no compression used, attempts to be the literal sound from a distance in the hall as a microphone hears it. Living Stereo (say a great one like Lt. Kije), mic'd closer and involving some compression and limiting in the process, tries to make the sound you get from your stereo more like the orchestra would sound to your ears sitting a few rows back at the live event, with an "ear" toward a pleasing musical effect. There are other approaches - Living Stereo is downright purist compared to many other recordings, and on the other hand Barry here has done realistic recordings without compression - but between these two examples, the Lt. Kije feels more to me like the concerts I've heard than a Telarc CD.

    Then there's practical concerns. Say you have a very soft voice and a big band backing the singer hitting a loud passage. You want to make it all out in the recording. If there's a huge difference in volume you have to be able to "turn down" or restrict the loud sounds while keeping the softer sounds up enough, or your playback system and environment will have to play the soft sound loud enough to be heard while the loud sounds might blow off the roof.

    Let's set aside the points of keeping needles in grooves or whatever. How many places can you reproduce a real orchestra, rock band, big band, trumpet etc, and would you want to listen to it full blast everywhere, every time you put on every record? But when you turn it way down, you can loose softer sounds. We have to capture good volume ranges to capture the expressions of sounds, but there's a point where compromise can be helpful.

    There is a point where you blend things like a band in relation to each other and that mixture just plain gels together well. Then let's say you want to hear Roy Orbison's ringing notes loudly, but also hear his soft notes and breaths, and pull it into a nice upfront presence. Or you want to hear John's soft falsetto counter vocal as easily as Ringo's crashing drum strikes. Well you can use compression and limiting tools for that. Compression and limiting in recording and mixing is a tool which can help to achieve that blending, and do it at volume levels that are desired and practical to play it all at.

    Like every tool, it takes human skills and taste to use to best advantage. :)
     
  19. Bob Lovely

    Bob Lovely Super Gort Staff

    Steve,

    Very informative tutorial...

    The difference between a compressor and a limiter is pretty easy to understand really. Perhaps, what is more confusing for our members is the proper use of these devices "in the chain" of recording, mixing and mastering. Then, just to add more confusion on how these devices affect recorded sound, there is the striking difference in sound between analog and digital compressors and limiters. The proper or improper use of these devices can mean the difference between an enjoyable listening experience and one that is highly annoying.

    Thanks!

    Bob-:)
     
  20. jdmack

    jdmack Forum Resident

    Location:
    Silver Spring, MD
    I'm going to post this knowing full well that someone more knowledgeable than I may jump in and correct me, so be sure to scan all future posts.

    Many musical instruments, particularly drums, have an initial attack to the sound that is momentarily much louder than the rest of the sound. This is called a transient. Without a compressor or limiter in the recording chain, one would have to set the recording levels very low to allow room for these transients to occur. Controlling the level of transients (which are nearly instantaneous) does not necessarily affect the perceived (or measured) dynamic range of music. It just allows one to record at a high enough level to get a better signal to noise ratio. Of course, if one takes that philosophy to an extreme, you get the infamous loudness wars that have been discussed in other threads.

    J. D.
     
  21. bdiament

    bdiament Producer, Engineer, Soundkeeper

    Location:
    New York
    Hi J.D.,

    "Very low" is relative. I would say that without a compressor or limiter in the chain, one has to set their recording levels carefully - more so than they would if they were using dynamic compression - but this is simply good recording technique. If you want to capture a sound as it occurs in real life, you must leave room for the transients.


    Controlling transients with any sort of dynamic processor will most definitely effect the perceived and measured dynamic range. Perhaps there will be some listeners who will not hear the change but by its very nature, a compressor or limiter is effecting the dynamics of the signal.

    Compression tools, like any other in the engineer's arsenal, are "colors" (or "effects") one can use to change the sound. In my view, they are there to be used if one desires their effects but are hardly necessary in order to make a proper recording.

    Best regards,
    Barry
    www.soundkeeperrecordings.com
    ...uncompressed, unlimited, all the time.
    www.barrydiamentaudio.com
     
  22. lukpac

    lukpac Senior Member

    Location:
    Milwaukee, WI
    Really? Maybe he wasn't talking about the released take? Because there's a breakdown/false start before it, and it seems like there may have been a take or takes prior to that.

    I'll have to go back and re-read Recording The Beatles; I thought it implied that the two varied more in the specific settings, rather than an inherent difference in process.
     
  23. Doonie

    Doonie New Member

    Location:
    ...
    I would guess, by the mastering stage, the dynamics of the signal on the tape you're working with have already been brought down enough to fit onto whatever medium your mastering to?
     
  24. markytheM

    markytheM Forum Resident

    Location:
    Toledo Ohio USA
    Steve, I really appreciate the way you educate us on such mysterious and misused techiniques. Lord knows I've made a lot of recording mistakes in the last 30 years. Compression was the mystery effect and it took me years to realize what can, should or musn't be done. Limiting was a little easier to understand. But it took me a few years just to realize how different compressor/limiters were from each other. And I still have a lot to learn.

    When you said on the forum (somewhere a couple years ago) that the Manley Vari-Mu can achieve the same sound as the old Beatles Fairchilds- I knew I had to have one. Not only because it was the Revolver sound but just the fact that you seemed to recommend it. Now I gotta get the damn Teletronix.:laugh:

    What I'm trying to say really is: I've learned so much from you and others on this forum. Things that have enhanced my listening skills 1000%. Things that would have taken me years to learn or maybe not at all. Thank you for that.
    I've learned that all the bullship can be unravelled once you really know how to listen.

    Peace Love and Fairchild is father of the Manley
    Marky
     
  25. John Carsell

    John Carsell Forum Resident

    Location:
    Northwest Illinois
    And as always, thank you for your guidance.
     
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