Calibrating Ascend/HSU XR55 System. Help!

[JackT]

I'm in the process of going through the audio calibration of my system with the Avia Guide to Home Theater disk.

One of the last audio calibrations for the subwoofer is this 6-channel sweep, which is for LFE level calibration. It seemed to me that the XR55 is NOT performing the customary 10dB boost of the LFE channel of the Dolby Digital signal. (That is, the low frequency signal is much attenuated on the LFE channel relative to when it is sent over a main channel and "bass-managed" to the sub.) This would be bad if it were true, because there's nothing I can do about it.

I know some of you have xr55s out there. Have any of you observed anything like this?

Thanks for any help....

[curtis]

I don't think Dolby Digital boosts LFE by 10dB. I thought that was DTS.

With Avia though, you are suppose to match all the channels.

[muzz]

Sound to me like you are running the 6 analog inputs, is this correct?

Some AVR's do NOT add the 10db boost at the receiver with analog input, even some pretty expensive ones.

This go's back to SACD/DVD-A.

What are you using for a DVD player? Toshiba HD DVD?

[JackT]

Sound to me like you are running the 6 analog inputs, is this correct?

Some AVR's do NOT add the 10db boost at the receiver with analog input, even some pretty expensive ones.

This go's back to SACD/DVD-A.

What are you using for a DVD player? Toshiba HD DVD?

Thanks for the reply!

After much research, I have discovered that the Avia Low Frequency Pink Noise 6 Channel Pan test is incorrectly mastered. (This is according to Ed Mullen of SVS.)

BTW, I observed this with the SPDIF input and Dolby Digital (which is what the Avia disc is).

[Lee Bailey]

The Avia disk does not send an LFE signal.

This is from the FAQ for the Avia disk:

One must realize that LFE and low bass content are NOT one and the same thing. The subwoofer portion of the tests was intentionally placed in the main channels rather than only in the LFE. This allows more complete evaluation of how the sub integrates into overall bass reproduction.

[Dread Pirate Robert]

I'm in the process of going through the audio calibration of my system with the Avia Guide to Home Theater disk.

While Avia does have a number of useful test signals for subwoofer setup, personally I wouldn't rely on it to set the subwoofer level with an SPL meter. Aside from the mistakes in some of the test signals, and in addition to typical SPL meter inaccuracy in the bass region, the room interaction at low frequencies is such that a standard level calibration done to perfection could actually end up being wildly off the mark. The only way to properly calibrate and integrate a subwoofer is to graph your frequency response using a free tool such as Room EQ Wizard so that you can see what's really going on in detail, enabling you to make informed decisions (and compromises) on setting up your sub. Using a parametric equalizer such as the Behringer Feedback Destroyer (BFD) to flatten or otherwise shape the frequency response is also highly recommended for most situations. Short of this, setting the subwoofer level by ear by playing familiar and varied material until it sounds right is probably better than using Avia and an SPL meter.

I don't think Dolby Digital boosts LFE by 10dB. I thought that was DTS.

Dolby Digital decoders are supposed to boost the LFE channel by 10 dB when a subwoofer is present, and the same applies to DTS. The boost can vary without a subwoofer, or the LFE can even be ignored altogether in this type of setup.

By the way, DTS used to be mastered without accounting for the 10 dB boost, which caused issues in many multi-channel music releases, and the reference encoder used to boost the surrounds by 3 dB--both problems have long been addressed, but Dolby Digital supporters still bring it up at times. And Dolby Digital originally had really bad phase cancellation between the main channels and the LFE channel--this too has been fixed, although DTS supporters likewise still bring it up.

After much research, I have discovered that the Avia Low Frequency Pink Noise 6 Channel Pan test is incorrectly mastered. (This is according to Ed Mullen of SVS.)

Yep, not that I would doubt Ed, but I decoded the actual track, and sure enough, it's just plain wrong (like some of the subwoofer test signals on the DVE disc, too).

The Avia disk does not send an LFE signal.

Correct, which means that while it can be useful for testing bass management of the main channels, it's useless for testing the proper decoding and processing of the LFE channel. They were trying to do the right thing, but it seems that nobody involved in making the major calibration discs did a sufficiently thorough or accurate job, unfortunately. On the bright side, it is my understanding that the Avia guys are working with SVS in order to get the subwoofer signals in the next generation of Avia right.