subwoofer calibration (1 Viewer)

[phyllis]

When i calibrate my subwoofer with my disk test tones it is 10 db higher than intrenal test tones.The disk does it in dolby digital and the reciever in analog.Could this be the difference?Am i doing somethin wrong? Any help would be appreciated!Thanx

 

[Chih Jieh Chang]

Internal test tones are supposed to be calibrated to 75dB and test discs (Avia) calibrate to 85dB. Please correct me if I'm wrong anyone

 

[phyllis]

I am calibrating everything at 85db at 00 on my denon 3801 eceiver with the disk test tones but my subwoofer is at 95 db.10 db to high!Everything is dead on with the disk and receiver test tone except subwoofer.

Ig i lower the sub in disk tones to 85 db i get no real impact my receiver tone goes to -12 with receiver tones at 00 and 75 db i am -2 and it feels like my house is going to fall apart! To get the same effect with disk it seems the 95 db volume level seems right.Could this be right?

 

[Harold_C]

Probably going to have to take this one a step at a time:

For starters, you need to tell us how you have your speakers configured (LARGE versus SMALL). To set subwoofer levels properly with a minimum of confusion, the AVIA disc really should be used with all speakers set to SMALL.

On your Denon:

a) Make sure your Subwoofer Mode menus selection is set to LFE and not LFE+MAIN. That LFE+MAIN setting duplicates bass in all Large speakers and the subwoofer. Not only is this a crappy way to configure a system, it will probably drive you stark raving mad trying to calibrate.

b) Your Denon will allow you to save different channel level settings for each different surround mode. Both the receiver's test tones and the Avia disc should force the receiver into Dolby Digital mode (assuming you've got the DVD player hooked up with a digital cable).

c) You mentioned something about "Tone". The tone controls on the Denon should all be set to "0" before attempting to do any kind of calibration. After that, you want to be very careful in how you use the tone controls (if you use them at all). Usually tone controls are only active for certain surround modes. So, if you do something crazy like crank in +12 db of bass boost on the tone controls, you are going to get wildly different bass levels as you switch from surround mode to surround mode. It's really best to leave the Tone controls at "0" for a good long time (weeks or months), until you are very familiar with the sound of a properly calibrated system.

d) The Denon has an LFE pad under the surround setup menus. This allows you to adjust the level of the LFE track for individual surround modes. It must be set to 0dB for both Dolby Digital and DTS when you attempt to calibrate the system, or you will get totally messed up. My guess is this is your problem. There is no reason to ever touch this control except for playing DTS music discs (it should be set to -10dB) or for a system where the LFE track is overdriving your subwoofer.

 

[phyllis]

HArold i have done everything you said.Speakers are small,only lfe chosen on sub choises,and did not touch the dts or dolby digital lfe button.The thing is i calibrated everything first using receiver test tones at 75 and all is good.Then at the same volume 00db i calibrated using the disk and everything is the same except the sub being exactly 10db to loud.

It sounds good,but curiosity got the best of me because of this anomaly.thank you for all the replies,i will just keep on tinkering.Later!!!!!!!!!!

 

[Vince Maskeeper]

Without getting too technical- check to make sure the LFE pad setting in the menu is at the max position, which won't necessarily be 0 (but it might be). This is a different control than the sub control- you should have a toggle for LFE (might have one for DD and one for DTS) that allows you to move it between -10/0 and/or 0/+10.

This controls how LFE material is handled- and if it is incorrect and you calibrate witha test disc, your settings will be wrong.

With speakers set to small small, and the pad in the right position- then you should clalibrate correctly. If you do, and the internal tone still jumps up by 10- I'd guess it is incorrect (probably set to create tone at full level and is then passed to LFE pad control which boosts by 10. Don't know if this is possible- maybe Harold could chime in since he knows the internal workings of the decoder better than I.)

-V

 

[Harold_C]

If you do, and the internal tone still jumps up by 10- I'd guess it is incorrect (probably set to create tone at full level and is then passed to LFE pad control which boosts by 10. Don't know if this is possible- maybe Harlod could chime in since he knows the internal workings of the decoder better than I.)

I'm afraid I'm totally at a loss as to what could cause ONLY the bass tracks on the Avia to measure 10 dB higher than the other channels.

I've seen no block diagram of how the LFE pad is handled, but (intuitively) I believe that it would have to be done in the digital domain prior to the bass management bass mixer module (where bass is redirected depending on the number of speakers). Further, I think the LFE pad would have to be a "cut only" function.

If I were Phyllis, I would calibrate using the Avia (observing all the cautions about tone controls, LFE pads, etc.) and call it day.

It is possible, I suppose, that Denon has somehow messed up their tone generator by 10dB. But, that would be a pretty egregious error and would probably violate Dolby's license.

I think there is something missing here -- like some kind of setting on the DVD player or something else that is not jumping out at us.

I would expect different test tones to produce slightly different results for subwoofer calibration, particularly if the test tones use different pink noise filtering. But 10 dB is not a measurement artifact!

 

[Vince Maskeeper]

Well, I know my Denon is correct- so it seems odd that they would change midstream. I also find it interesting that you say this would be a violation of license, as there is at least one known product line that suffers from this problem. I'd be really interested to see exactly what Dolby's licensing agreement says in these regards, as I find it impossible that uber-budget products like Awia have managed to live up to such stringent standards, yet they wear the dolby badge.

Vince

 

[Harold_C]

I'd be really interested to see exactly what Dolby's licensing agreement says in these regards, as I find it impossible that uber-budget products like Awia have managed to live up to such stringent standards, yet they wear the dolby badge.

That's why everyone uses the same chipsets. The onus to provide Dolby-approved implementation of all the digital-domain stuff likes with Cirrus Logic. It's kind of like anyone can build a Windows computer by buying an off the shelf chipset package from Intel or Cirrus or AMD. Same deal with these Dolby Digital processors. All of the functions basically reside with the Cirrus Logic chips and you just wrap your analog stages, controls, displays, and menus around that.

I don't think it's very likely that the Denon test tones are wrong. Rather, I think there is some piece of the puzzle missing in Phyllis' situation: some setting or measurement that is escaping us.

 

[phyllis]

Well guys thanxs for your help again!I believe i have done everything right.I have been reading this forum for a long time,and the basics of calibration or totally understood.I am going out and buying video essentials and see if are similar maybe my avia is deffective.I will post results later.