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Discussion Starter · #1 ·
Hi.


This thread concerns only Delta 410, 1010LT and 1010. I don't know if the problem exists with the Revo.


I have now a HTPC based on XP (WinMe before), so I give a trial to the Maudio 5.10.00.0031 wdm driver (I have a delta 1010). I have encoded a small 3 second ac3 file with simultaneously :


1000 Hz -20dBFS on FL FR C SL SR

80 Hz -20dBFS on LFE


So all channel have the SAME level. Dialogue normalization is encoded at -31dB (thus no attenuation should be done by the decoder during the decoding process).



The bass managment setup is given in the snapshot "Bass Management 5.10.00.0031.png" :


- no filtering

- no reroute

==> LFE +10dB ON
 

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Discussion Starter · #9 ·
I tested v5.10.00.0029 driver yesterday.


I recommend this new version because some bugs have been solved (see below).


First, here is the peak meters view with bass managment OFF.


==> All is CORRECT. You can see each -20 dBFS signals on each channel.


So now we know that the audio levels encoded on the ac3 are correct.


Emmanuel
 

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Discussion Starter · #10 ·
v5.10.00.0029 and Bass Managment ON


- no filtering

- no reroute

==> LFE +10dB OFF LFE channel level is totaly WRONG with Bass Managment ON
 

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Discussion Starter · #12 ·
Center reroute :

===========


Some obvious math : if FL, FR and C play A level, each give 20 log A decibels.


When C is reroute, FL and FR must play A + A/2


X = 20 log (A + A/2) = 20 log (3A / 2) = 20 log A + 20 log 3/2 = 20 log A + 3.52dB


In the ac3, 20 log A = -20 dBFS. Thus FL and FR should play at -16.48 dB.


It is difficult to see exactly the FL and FR levels on the peak meters, but it seems more closed to -15dB than -16.48 dB

 

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Discussion Starter · #13 ·
LFE Reroute :

==========


of course totaly wrong because LFE level is already wrong.


I have also to test bass redirection on the sub channel. Result tomorrow.
 

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These are great tests! I experience the same type of thing on my system. It is a shame because I don't have a center channel and want to route LFE to the mains, but getting the bass right is basically impossible.
 

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Emmanuel,


Just talked with a tech manager at M Audio about this bass problem and have sent a link to this thread for use by the new programmer.
 

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Quote:
Originally posted by Pultzar
Can anybody confirm if these problems also exist with the Revo?
Yes it does! Just received a call from M Audio to discuss this problem (because they did receive all 7 emails as stated above).
 

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While he's at it, the new programmer might want to take a look at the Sonica Theater's behaviour under similar circumstances, something funny going on with that too, at least in 6.1 and 7.1 mode switching between bass mgmt on and off.
 

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Discussion Starter · #20 ·
Filtering Test

==============


Encoded C level : 30Hz at -20 dBFS


The filters implemented in the Delta Bass Managment are -12 dB/oct.


- With Crossover freq. set to 60 Hz the signal should be attenuated by 12dB (30 Hz is one octave below 60 Hz) and the C level should be -32 dBFS


- With Crossover freq. set to 120 Hz the signal should be attenuated by 24dB (30 Hz is two octaves below 120 Hz) and the C level should be -44 dBFS.


These two values are theorical asymptotic values. Real values are a little smaller.


The C levels after filtering in both cases seem "correct" because they are closed to -33 and -48dB.
 
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