yet another sub calibration question

Discussion in 'Archived Threads 2001-2004' started by Patrick_T, Jan 12, 2002.

  1. Patrick_T

    Patrick_T Agent

    Dec 14, 2001
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    I've done some searching but I am not quite clear on a point or two about subwoofer calibration. Ok, the first thing I don't quite get concerns subwoofer and LFE channel trim controls. Now, depending on what documentation I read they reference changing the sub trim controls or the LFE trim controls. Are these controls one and the same, or do some processors allow you to adjust both? Below is some test I cut from the svs manual for the CS series subs.

    Quote starts here:

    Finally, ensure your subwoofer amp's volume control (if it has one) is set full up, to start. It's a good idea to check the separate subwoofer level control of your sur-

    round receiver before you begin the test tones too. Keep it to no higher than -5 dB initially (that's one fourth up on a typical receiver channel limits of -10 dB to +10 dB) . Your LFE trim, if you have one, should be set to 0dB to start too. As the tones start, alternating from speaker to speaker (watching your sound meter

    now) set each speaker's volume to about 75 dB, using the receiver's channel controls (leaving master volume the same). We recommend you turn down the receiverís subwoofer level, before you lower your

    amp's volume control to keep input distortion to a minimum

    End Quote:

    So, they reference both a sub trim and a LFE trim. I am looking at getting the outlaw 1050 receiver and I have only seen reference to a sub trim, not a LFE trim. What if anything is the difference?

    Next, say I adjust all my speakers to reference level using AVIA. Now, say my center is +2 on my trim controls and my surrounds are +1 on the trim controls. Does this change how much bass is sent to the subwoofer or do the trim controls effect the amplifier section and not the line level being fed to the sub output? The reason I ask is that it seems that if adjusting the trim levels of various channels effected the amount of bass level sent to the sub out for that channel then when you run the AVIA test you would get varying sub level outputs depending on which channel is being listened to.

    I hope someone understand anything I wrote, sometimes putting confusion to words just doesn't work. Thanks in advance.

  2. BruceD

    BruceD Screenwriter

    Apr 12, 1999
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    Here are some answers, we may need more.
    Re-directed bass and LFE are two separate bass sources coming from different places.
    Your receiver has a crossover that gets used for re-directing bass when any of the 5 speakers are selected as small in the speaker setup menu.
    This re-directed bass just happens to get sent to the same sub-out receiver port and speaker that handles the LFE bass (LFE is the .1 channel).
    So, as you can see, there are two different sources for bass being sent to the sub-out port on your receiver where your sub is connected.
    Since there are two different bass sources, it makes sense there could be two different bass trim controls (this isn't always the case though).
    AVIA does not output a specific LFE (.1) channel test signal through the sub-out or .1 channel only. AVIA expects you will have bass re-direction engaged so they send the bass test signal through the other 5 channels.
    You will need to read the AVIA manual carefully and search this forum for "AVIA Calibration" to get comments by the AVIA author Guy Kao on how to best use it.
    I don't own AVIA yet, but will soon. I have the VE or Video Essentials DVD currently.
  3. Pete Mazz

    Pete Mazz Supporting Actor

    May 17, 2000
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    Yes, there are usually seperate level controls for "Sub Level" and "LFE". The LFE control is usually just a cut control, so the settings run from -10 dB to 0 dB. You will almost always leave this at 0. The sub level control is more akin to a volume control and will typically run from -10 to +10. This is the control you use to adjust the level of output from the sub to calibrate it to the rest of the system.

    To answer your second question, the answer is probably going to be "depends on your processor". Avia let's you level match, using the bass redirection capabilities of your processor, each individual channel to the sub. My guess is most processors will boost or cut the bass along with the rest of the signal sent to an individual speaker.

    This, I would guess, may cause mismatched levels if, say, your surrounds were 20' further away than your mains and the sub was 5' away. To level match the sub to one of the surround speakers, it would probably leave you with a higher sub level than, say, the level that balances with the main speakers. I would balance the sub to the mains and not worry about the rest.


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