Subwoofer level vs LFE level

Discussion in 'Beginners, General Questions' started by ShaheemP, Sep 14, 2005.

  1. ShaheemP

    ShaheemP Auditioning

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    Hi,

    I hope I am posting this in the correct section. The question I have is one that I am sure has been asked many times before and I hope I am not frustrating anyone by asking again. The question I have concerns setting your speaker levels with a sound meter. I have read threads on this forum and countless other forums regarding this but have been unable to find and answer to my specific question.

    Firstly my equipment:
    Receiver: Yamaha RXV-800
    Settings: all speakers are set to Small, Bass set to Subwoofer

    Subwoofer: B&W ASW600
    Settings: Crossover defeated, Volume control on 9 o’clock position, Slam setting ‘A’

    I can’t remember the name of my setup disc but it is not Avia or Video Essentials. In any event, what is confusing me is the following:

    My amp has a subwoofer level setting (0 to -20db) and in the setup menu it also has a Dolby Digital LFE level (0 to -20db) and a DTS LFE level ( -10db to 10db ). How do these relate to each other?

    One explanation I got was that I should use the subwoofer level when setting my speaker levels, i.e. disconnect the subwoofer when setting speaker levels. Once they are set I should select the test signal for the center channel, disconnect the center channel and then set the subwoofer via the subwoofer level setting to the same db as the speakers. I should then run the subwoofer test on the test disc and then adjust the LFE level setting until I get the same db as the speakers and do the same for the DTS LFE level using the DTS test signals on the disc. His reasoning was that since all speakers are set to small, the subwoofer level controls the level of bass that would normally be going to the speakers. The LFE adjustments are for the .1 channel which goes to the sub.

    Another explanation I got was that I should set both Dolby LFE and DTS LFE to max and then only adjust the subwoofer level setting using the subwoofer test section of the disc. The LFE settings will track the subwoofer level setting.

    Could someone please point me in the correct direction as it is driving me nuts. I used to set by ear but now that I finally have an SPL meter I would like to set correctly.

    Thank you in advance for any help.
     
  2. John S

    John S Producer

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    I would not set them to max. Just no reason to have the pre-amp section of your AVR maxed out.

    To set each of them properly with that sort of robust bass management, you would have to set each one separately.

    Your disc would have to have Bass that can run to at least your front channels in a minimum of stereo, then you set the bass level with that. Then it would have to have both DD 5.1 / LFE bass test to set the DD LFE bass level as well as a DTS 5.1-6.1 . LFE to set that level.

    On the plus side, that is some great bass management that is not available to most of us with even slightly older AVR's and/or Pre/Pro's.

    Running into this recently, I set the DD LFE and then matched it as well as I could. by running content that had both DTS and DD 5.1...
     
  3. rob-h

    rob-h Second Unit

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    I am not familiar with this model but generally, the LFE is set to 0db. Ther is really no reason to go lower. On most yamaha's the sub level is -10 to +10. You set the gain on the sub to 45% or so and then calibrate the sub to the same db as your speakers using the sub level . The DTS level is useful because the bass on a DTS track is mastered at 10db lower then dolby digital. This feature allows you to boost DTS tracks while not effecting dolby digital ones. No up and down with the sub level depending on which track you select.
     
  4. ShaheemP

    ShaheemP Auditioning

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    Thanks for the replies.




    Ah, so this explains why the Dolby Digital LFE setting runs to 0db while the DTS LFE settings runs to +10db. So I should then set my DD LFE setting to 0db and DTS LFE setting to +10db.

    Now when I set the levels of my speakers do I then disconnect the sub. Since my speakers are set to small I assume the sub will output part of the test signal and influence the reading. If the speakers were set to Large then I assume the sub would play no part of in the reading. If I set all speakers to Large and then set levels, will they be set wrong when I switch them to Small?

    John, from your post I understand that you agree with the first explanation in my post i.e. sub level for "normal" bass and LFE level for .1 bass. Rob on the other hand seems to be more in agreement with the second explanation i.e LFE level tracks subwoofer level setting. [​IMG]

    I can see why the new auto-setup amp are such a good idea [​IMG]
     
  5. rob-h

    rob-h Second Unit

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    The lfe level is a way to trim the LFE. Thats the only purpose it serves. Its normal level is 0db and I am 99% sure that it even states that in your manual.

    If you are calibrating your speakers with pink noise, the sub has no effect on the SPL db unless you have the sub selected in the menu. Only the speaker selected will output the signal.
     
  6. John S

    John S Producer

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    Well my AVR does not allow both DTS and DD LFE to be set separately. it goes from -10 to -10 just lake any other channel I have available.

    It does remember my settings per mode , per source though. So if I set the sub channel higher with DTS running on my DVD source, that will be there everytime a DTS source is playing, leaving the Dolby channel setting alone.


    Different means to an end I suppose. I like your bass management option beter though in all honesty.

    The LFE is a separate channel, it naturally does not contain the bass for any of the other channels, the only way to get that bass to the sub is with bass management, setting speakers/channels to small and setting the cross over to your sub where you want it.

    Now once you do set your speakers small the LFE channel including the bass from your other channels will / should go up and down.

    Only newer AVR's will let you calibrate them separately. For most of us, we set to small, and then calibrate using say a stereo mode and a DD LFE only mode. Works out well in most instances. I can see some benefit to allowing calibration separately for the two levels. One being just the LFE channel, and the other being just the bass being redirected to it.
     
  7. ShaheemP

    ShaheemP Auditioning

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    I think the cause of my confusion is the channelling of sound under 90hz to the sub if the Small setting is selected. My understanding is that the pink noise signal is full range (20hz-20khz), so when running with Small the pink noise under 90hz is reproduced by the sub.

    If I get the chance tonight I think I will do the following.
    1. Set DD LFE level to 0db.
    2. Set DTS LFE level to +10db.
    3. Set all speakers to small.
    4. Set Bass to subwoofer only.
    5. Set the amp levels of all speakers to 75db with the subwoofer connected and on.
    6. Set the amp level of the subwoofer to 75db (ok, maybe 78db for that extra bit of wow [​IMG] ).
    7. Recheck the speaker levels to make sure they still peak at 75db.
    8. Select the DTS test signal on the disc and then check if the DTS sub signal produces 75db.

    Now to figure out a way to get the wife and kids to go sleep early so that I can play with the settings without getting requests for Barney or Lion King [​IMG]

    These small and large settings have got me thinking. Wouldn't the perfect system be one that has a subwoofer for each speaker (to handle the bass portions directed to that channel) and one subwoofer dedicated to playing the .1 channel?
     
  8. rob-h

    rob-h Second Unit

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    My fault! I thought I read that you were not using a setup disk. I thought you were using you internal test signal. You are correct about the signal under the crossover being sent to the sub if you select small.

    Your last question is a toughy. Most pros (and thx) dont like the idea of multiple bass sources placed in diffrent areas of the room. The bass waves interact in funky ways and can cancel each other out. On the other hand some guys swear by full range speakers all around. I go with the pros on this one. I have multiple subs but they are colocated.
     
  9. ShaheemP

    ShaheemP Auditioning

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    Last night I did the following.

    I used the internal test tone of the amp to set the levels to 75db. The only problem was that the test tone does not play through the subwoofer at all - it only sweeps through the other speakers. The amp though, does have a signal generator that you can vary between 35hz - 88 hz (it can go higher but for my purposes I stopped at 88hz).

    I then used this generator to set the subwoofer level as close to 78db across the range specified above. At the lower frequencies it was closer to 78db and at the upper frequencies it was close to 80db.

    I then popped my test disc in to see how the levels would compare - by the way the disc is called DiscWasher. Amazingly all the channels were more or less on 75db albeit at a higher volume. Test tones had 75db at about -28db on the volume control read out and the test disc had 75db at about -33db on the volume control readout.

    The only reading that was off was the subwoofer reading - it was peaking at 86db. Lowering the subwoofer level to get it to 78db also decreased the other speakers to about 70db.

    I left the subwoofer level at the reading I got using the internal test tones and popped in Queen Live at Wembley. It being 10:30 at night I could not turn up the volume to hear if I was overdriving the sub. The volume was at -42db where my normal listening is done at -36db to -32db depending on recording. Suffice to say I was happy with the results. Previously when only using the test disc to setup, the Queen disc sounded very low on bass - as if there was no sub channel on the DTS track. It did not sound like a wall of Marshalls but at least it put a smile on my face.

    I will have to wait for the weekend to do a U-571/Saving Private Ryan test, to see if the sub can handle volumes in the -36db to -32db. If there is no bottoming out of the cone then hopefully I will start listening to the movies and not to the equipment.[​IMG]
     

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