Our contenders for today are the DD and DTS soundtracks on the R1 DVD of the blood sucking vampire sequel 'Blade 2'.

When the 'Blade 2' DVD was released, a controversy arose in the HT community. Some fellow enthusiasts reported that the DD track on this particular DVD appeared to have quite a bit more bass response than the corresponding DTS track throughout the whole movie. The difference was said to be the most appreciable in the Rave Party Sequence.

It was assumed that the difference pertains mostly the LFE channel and that it might be souped up around 3-4db overall on the DD track, similar to the mastering 'error' that occured on the U-571 DVD from Universal, where the LFE channel of the DTS track is a full 4db louder than the DD counterpart.

Yet, others reported the 2 tracks to basically have the same frequency response. Controveries like this are the very reason for this part of my website. A graph can say more than a thousand words.

What i found out:

• The DD track does not have more bass response in generell.
• Only in one scene, out of around 10 i measured (basically every bass loaded scene in the movie), was there a difference between the 2 tracks that goes beyond the typical characteristics of the DD and DTS codecs and the used bitrates. This scene is the aforementioned Rave Party Sequence.
• The difference in that particular scene was not in the LFE channel, but in the main channels (most likely also in the center, didn't measure that).
• DialNorm on the DD track is 0dB, so that the explanation for the differences some people heared might be the DialNorm Compensation feature in many receivers. See conclusion below.

Lets have a look at the graphs now. Look at the main page for an explanation how these are obtained.

Note: 0db on the vertical scale of the graphs indicates 115db SPL, which is only achievable by the Lfe channel; all non-lfe channels max out at 105db, thus -10db on the scale.

Description:

• Opening Fight (first appearance of Blade)
• DD 448kBit/s vs. DTS 768kBit/s
• DialNorm 0db !!!
• upper window is the right channel, lower window is the lfe channel
• red is DD, turquoise is DTS
• lfe data above 120hz is irrelevant!!!

Analysis:

• Basically identical apart from the 2 typical characteristics of the DTS encoder at 768kbps: Frequency response drop above 15kHz and -3dB @ 90hz. Interesting that the frequency drop above 15kHz is not the typical 10db, but only 3db and in later graphs below even almost none. Reasonable to assume that MiCasa didn't use the normal CAE-4 encoder, but something else, maybe a software based encoder.
• I suspect the little difference in response of 2-3db @ 8hz is measuring error or a glitch in the matrix ;O) The graphs are just too identical to assume any difference in the mix here.

Description:

• Rave Party
• DD 448kBit/s vs. DTS 768kBit/s
• DialNorm 0db !!!
• upper window is the right channel, lower window is the lfe channel
• red is DD, turquoise is DTS
• lfe data above 120hz is irrelevant!!!

Analysis:

• This is the only scene i have measured that had any difference in bass response that can not be attributed to the encoder characteristics. Bass below 18hz is filtered with around 15db per octave on the DTS track. For what reason? Beats me!
• -3db @ 90hz and -3db above 15kHz as usual

Description:

• Mega Bomb (in sewers)
• DD 448kBit/s vs. DTS 768kBit/s
• DialNorm 0db !!!
• upper window is the right channel, lower window is the lfe channel
• red is DD, turquoise is DTS
• lfe data above 120hz is irrelevant!!!

Analysis:

• yawn! :O)

Description:

• End Fight
• DD 448kBit/s vs. DTS 768kBit/s
• DialNorm 0db !!!
• upper window is the right channel, lower window is the lfe channel
• red is DD, turquoise is DTS
• lfe data above 120hz is irrelevant!!!

Analysis:

• Here the only interesting thing is that it appears that they transfered around 2db of response below 10hz from the Main channels to the LFE. Irrelevant oddity at best.
• Boring otherwise.

So, the only real difference was in the Rave Party Sequence. But actually in the mains, and not in the LFE, as suspected. But why then did some people hear a strong difference throughout the whole movie?

My guess: 'DialNom Compensation'

I will not discuss here what DialNorm does in general, most reading this will most likely know. The DialNorm Compensation that is build into receivers of several brands, adds 4db to all Dolby tracks in order to compensate for the common 4db difference in volume between DD and DTS tracks. This works on most tracks, since DialNorm is '-4db' in most cases, so the compensation levels the playfield again. But when a track is recorded with a DialNorm of '0db' (which is rather rarely the case) the DD track ends up being 4db to loud, because the compensation wasn't needed, but is added anyway.

A soundtrack being 4db louder as the counterpart, will first and foremost impress with a stronger fuller bass response, although in reality the difference is throughout the whole frequency response. Adding these 4db overall panalty and the filtered bass response of the main channels in the Rave Party scene, the DTS track sure would sound 'weak' bass wise in that scene particularily.

Since i basically measured every bass heavy scene in the movie and only found this one scene to differ, i would consider this to be a non-issue. The Rave Party scene sounds not all that different and is basically just as immersive on the DTS track if playback levels are matched properly. Actually, the bass response of the LFE channel is so much stronger below 20hz anyway, that it should dominate the bass energy that is played through the main channels or that is routed to the bass.

So 'Party On' folks and listen to whatever soundtrack you prefer.

Best regards
Bjoern Roy