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Anthem D2/D2v/AVM50/AVM50v/ARC1 tweaking guide - Page 1212

post #36331 of 42717
Quote:
Originally Posted by scheong View Post

Thanx Roger and Bob for responding to my post.

As part of the ARC procedure, I did set both the front left and subwoofer sound level to 75db using a SPL meter before starting the ARC measurement. After uploading the new ARC result, I spent the next couple of days just listening and enjoying the new setup playing various CDs, Bluray movies, and SACDs. I was (and am) really happy with everything.

That's why I was more than a bit surprised by the measured subwoofer sound level difference between the two calibration disks. Both disks were played by an Oppo 95 connected to the 50v via HDMI. I will re-do the measurements with the two calibration disks again later this week just to cross check myself.

Stanley

Stanley,
Please check that you have up to date firmware in your Oppo BDP-95. The folks at OPPO just re-confirmed for me that the Analog output SACD LFE level is correct in the two most recent firmware versions (from last December, and from just this month). I.e., it is attenuated -15dB compared to the other Analog channels just as is the case with Analog LFE output from other multi-channel audio formats.

However there WAS a bug in the firmware for the 95 from earlier last year which had the SACD LFE Analog output level on the 95 +5dB too hot.

Check in Setup > Device Setup > Firmware Information. The Main firmware version should end either 1219 (the one from last December) or 0302 (the one from this month).
--Bob
post #36332 of 42717
Does the BDP-83 have this 5dB fix?

If our SACD player has a +5 or +10dB LFE error and we setup an input for it on the AVM/D called "SACD" can it be configured to always apply -5 or -10dB to the LFE channel?

In other words can specific channel trims (LFE only, not sub) be applied on a source input basis or just globally?
post #36333 of 42717
Quote:
Originally Posted by tngiloy View Post

Many large 'full range' speakers use midrange and tweeters (which is basically your C5) stacked on top of a large woofer or two. The full range speaker makers usually try to isolate the speakers from each other in the cabinet enclosure, and you should try to isolate your center from your sub to reduce any possible negative interaction.

They also try to make sure there are no cabinet edges near the tweeter or midrange (these days). For example, look at the newer B&W Nautilus series compared to the old Matrix series. Not saying you need a spherical cabinet but do try to keep the faces of the cabinets that you are placing together flush with eachother. With the design of the Sub-2 (hexagonal) this will be difficult and look funny at best.
post #36334 of 42717
Quote:
Originally Posted by Bardia View Post

I think for $500 more, I will get the 95, just for 2 channel sake of having the balance output and have 3d for future.

But I must really decide on the pre/pro. Thanks for your input. I just need to find a stereo shop that has these installed so I can hear them. I bet that will be a challenge.

I'm going to give you a different viewpoint than the other guys...

Since you are keen on 2-channel I think the balanced BDP-95 is a good choice, but only with a great analog preamp. Assuming you only have one system, I would then suggest getting the D2 and using it in analog bypass for 2-ch mode. Then the "better digital parts" in the D2v would be irrelevant. Combining 2-ch stereo and HT is always a compromise, and this is the best compromise for reasonable money and complexity IMO.

If you are more keen on a 7.1 movie setup then the D2v or even 50v is better.
post #36335 of 42717
Quote:
Originally Posted by AVfile View Post

Does the BDP-83 have this 5dB fix?

If our SACD player has a +5 or +10dB LFE error and we setup an input for it on the AVM/D called "SACD" can it be configured to always apply -5 or -10dB to the LFE channel?

In other words can specific channel trims (LFE only, not sub) be applied on a source input basis or just globally?

As best I can recall the Oppo 83 has never had a problem like that. So no worries.

You can't save volume trims per Source in the Anthem. You can apply "temporary" trims per audio input format using the buttons on the remote, which might accomplish the same thing.
--Bob
post #36336 of 42717
Quote:
Originally Posted by Nick @ Anthem View Post

When ARC is active, LFE Bypass Xover is in effect. This means that redirected bass is crossed over at the Sub Xover frequency displayed in the setup menu, while LFE runs unfiltered at its native 120 Hz bandwidth.

When LFE Bypass is not engaged, i.e. when a more conventional crossover is in effect, "Sub Xover" which is seen in the setup menu (and not ARC Targets) performs exactly as labeled - set it too low and you lose too much LFE.

Thanks for the clarification. In summary I guess it would be safest to keep LFE Bypass on at all times. With ARC on there is no worry, but with ARC off it keep the "Sub Xover" working more consistently. The other way we could lose LFE and I can't think of a reason why you would want that. It's not like the LFE is preserved by sending it to the main speakers right? (If there is a concern with sending higher frequencies to the sub that's why subs have their own filters.)

Quote:
Originally Posted by Nick @ Anthem View Post

The ARC Target panels indicate the correction cutoff or range, not crossover frequencies as is often thought, although the two almost always use the same figures, the exception being what happens to the LFE portion of the sub channel assuming no manual overrides are in effect.

Why does ARC have cutoff ranges at all? Is it not desirable to have the solution computed over the greatest range possible (within reason) or would that be too time consuming?
post #36337 of 42717
Quote:
Originally Posted by AVfile View Post

Thanks for the clarification. In summary I guess it would be safest to keep LFE Bypass on at all times. With ARC on there is no worry, but with ARC off it keep the "Sub Xover" working more consistently. The other way we could lose LFE and I can't think of a reason why you would want that. It's not like the LFE is preserved by sending it to the main speakers right? (If there is a concern with sending higher frequencies to the sub that's why subs have their own filters.)



Why does ARC have cutoff ranges at all? Is it not desirable to have the solution computed over the greatest range possible (within reason) or would that be too time consuming?

Sure, leaving Bypass LFE ON is a good idea just in case you have ARC off for some reason. Also, if you have a sub that goes deep you should have THX Ultra 2 Sub set. And if the Sub is up against a wall you may or may not want to have Boundary Gain Compensation set. Then also turn Room EQ Filter OFF and Center EQ OFF unless you are sure you want those engaged when ARC is OFF.

Finally, keep in mind that actual output when ARC is On is a combination of the Volume Trims the Crossovers *AND* cuts and boosts implemented by the Room Correction parameters. When you turn ARC OFF, the Room Correction parameters stop being used, the settings above START being used but the volume trims and Crossovers ARC Uploaded remain in effect. Those Volume trims and Crossovers MIGHT NOT be the best choices in a solution you set up Manually. For example if the Room Correction was doing mostly cuts, then the Volume trims WITHOUT Room Correction might be a bit high.

The point is, it is not really easy to set up to use ARC with some Sources and NOT with other Sources (except of course for Analog Direct Sources where ARC, and all the other stuff, doesn't apply anyway).

------------------------------------------

Limiting the correction range allows ARC to concentrate its processing resources in the frequency range you want corrected. Which may result in a cleaner solution. Limiting the correction range in treble for the main speakers means that ARC may not make FAULTY correction based on BOGUS high frequency results from the mic.
--Bob
post #36338 of 42717
Quote:
Originally Posted by Bob Pariseau View Post

Stanley,
Please check that you have up to date firmware in your Oppo BDP-95. The folks at OPPO just re-confirmed for me that the Analog output SACD LFE level is correct in the two most recent firmware versions (from last December, and from just this month). I.e., it is attenuated -15dB compared to the other Analog channels just as is the case with Analog LFE output from other multi-channel audio formats.

However there WAS a bug in the firmware for the 95 from earlier last year which had the SACD LFE Analog output level on the 95 +5dB too hot.

Check in Setup > Device Setup > Firmware Information. The Main firmware version should end either 1219 (the one from last December) or 0302 (the one from this month).
--Bob

Hi Bob,

I am pretty sure I installed the latest official firmware for the BDP-95. I will check tonight. The bug you are referring to seem to only affect the multi-channel analog outputs, correct? In my case, I am connecting the BDP-95 to the AVM50v via HDMI. So this bug should not impact my subwoofer measurements with the SACD test disk.

For both Bluray and SACD, I have the BDP-95 decode to LPCM via HDMI to the AVM50v. Base on my understanding, I should not see any difference on the subwoofer measurement between either the Bluray AIX test disk and the SACD test disk. As I said, I will do the measurement again later this week to cross check myself.

Thanx for pursuing my measurement anomaly with Oppo. You and quite a few others make this thread a must read for me.

Stanley
post #36339 of 42717
Quote:
Originally Posted by scheong View Post

Hi Bob,

I am pretty sure I installed the latest official firmware for the BDP-95. I will check tonight. The bug you are referring to seem to only affect the multi-channel analog outputs, correct? In my case, I am connecting the BDP-95 to the AVM50v via HDMI. So this bug should not impact my subwoofer measurements with the SACD test disk.

For both Bluray and SACD, I have the BDP-95 decode to LPCM via HDMI to the AVM50v. Base on my understanding, I should not see any difference on the subwoofer measurement between either the Bluray AIX test disk and the SACD test disk. As I said, I will do the measurement again later this week to cross check myself.

Thanx for pursuing my measurement anomaly with Oppo. You and quite a few others make this thread a must read for me.

Stanley

Actually that old bug (fixed some time ago) also affected SACD LFE level on the HDMI output.

Remember that it is not the absolute SPL level that you are matching. There's no reason to believe the tones on the two discs are recorded at the same volume. What matters is the trims you need to make to balance sub vs. mains. The level adjustments you make to balance sub vs. mains on the AIX disc should ALSO work for the Pentatone SACD test -- i.e., no need to use DIFFERENT sub volume trim just because you are listening to SACD.

Presuming you are using ANALOG-DSP and ARC in the Anthem, the speakers in the OPPO should all be set to Large (with Sub ON) and the volume trims in the OPPO for all of them should be at 0dB --EXCEPT for Sub which should be at +5dB. Set Analog down-mix in the OPPO to 5.1. Set that way, the volume trims ALREADY established by ARC in the Anthem will work correctly both for HDMI audio AND for this multi-channel Analog audio from the OPPO. You may need to lower the Analog Input Level in the Anthem for the 6-CH input by -1.5dB to match the absolute volume levels of the Analog input and HDMI input (and remove any chance the Analog input might clip). But that's a change that happens across all speakers so it doesn't alter the relative volume balance between them.
--Bob
post #36340 of 42717
Quote:
Originally Posted by Bob Pariseau View Post

Actually that old bug (fixed some time ago) also affected SACD LFE level on the HDMI output.

Remember that it is not the absolute SPL level that you are matching. There's no reason to believe the tones on the two discs are recorded at the same volume. What matters is the trims you need to make to balance sub vs. mains. The level adjustments you make to balance sub vs. mains on the AIX disc should ALSO work for the Pentatone SACD test -- i.e., no need to use DIFFERENT sub volume trim just because you are listening to SACD.

Presuming you are using ANALOG-DSP and ARC in the Anthem, the speakers in the OPPO should all be set to Large (with Sub ON) and the volume trims in the OPPO for all of them should be at 0dB --EXCEPT for Sub which should be at +5dB. Set Analog down-mix in the OPPO to 5.1. Set that way, the volume trims ALREADY established by ARC in the Anthem will work correctly both for HDMI audio AND for this multi-channel Analog audio from the OPPO. You may need to lower the Analog Input Level in the Anthem for the 6-CH input by -1.5dB to match the absolute volume levels of the Analog input and HDMI input (and remove any chance the Analog input might clip). But that's a change that happens across all speakers so it doesn't alter the relative volume balance between them.
--Bob

Hi Bob,

Yes, I understand. The relative sound level between sub and mains should be the same between the AIX disk and Pentatone SACD test disk...if things are working correctly.

Since I am connecting the BDP-95 to the AVM50v via HDMI, do I still need to go into the BDP-95's multi-channel setup menu to set speaker size, volume trim, and down-mix?

Stanley
post #36341 of 42717
Quote:


Also, if you have a sub that goes deep you should have THX Ultra 2 Sub set. And if the Sub is up against a wall you may or may not want to have Boundary Gain Compensation set.

Hi Bob. As I have 2 Seaton Submersives should I experiment with the above? Would engaging THX Ultra 2 sub override settings set by ARC?
post #36342 of 42717
Quote:
Originally Posted by thestewman View Post

Stud

First, I would be concerned with marring the finish on the top of the Sub2.

You would probably be better off with a center speaker stand for the C5 and then finding the best sounding place for the Sub2 between the L/F, Center
and R/F speakers if the sub has to be along the front wall.
I have heard that a vertical center speaker if it is going to be behind or just below the screen is optimum. I don't know the dispersion of the C5. You might want to investigate.

Stew

Thanks Stew, I have read that the center should be the same as the mains, S8s, if it's going behind the screen. I am not as worried about my finish on top of the Sub 2 as not long after I installed it it rattled the heat vent cover out of the ceiling and it fell on the sub leaving a bad 6" long dent in the wood. Maybe the best spot will be between the main and the center, I'll see when I get it.
post #36343 of 42717
Quote:
Originally Posted by SimonNo10 View Post


Hi Bob. As I have 2 Seaton Submersives should I experiment with the above? Would engaging THX Ultra 2 sub override settings set by ARC?

No. When ARC is active for a Source, those settings I mentioned are ignored -- replaced by the more sophisticated ARC processing.

Those settings are also ignored during ARC Measurement.
--Bob
post #36344 of 42717
Quote:
Originally Posted by scheong View Post


Hi Bob,

Yes, I understand. The relative sound level between sub and mains should be the same between the AIX disk and Pentatone SACD test disk...if things are working correctly.

Since I am connecting the BDP-95 to the AVM50v via HDMI, do I still need to go into the BDP-95's multi-channel setup menu to set speaker size, volume trim, and down-mix?

Stanley

No those OPPO settings only alter it's multi-channel Analog outputs. I somehow got the impression you were using both Analog and HDMI.
--Bob
post #36345 of 42717
Hi Bob,

Looks like the BDP-95 bug affecting the SACD LFE level on the HDMI output is still there. My BDP-95 is on the latest official firmware (BDP9x-65-0302).

SACD test disk sound levels:
LF - 60db, C - 60db, RF - 60db, LS - 61db, RS - 61db, Sub - 68db

AIX bluray test disk sound levels:
LF - 60db, C - 60db, RF - 60db, LS - 61db, RS - 61db, Sub - 63db

I will forward this info to Oppo.

Thanx for your help.

Stanley
post #36346 of 42717
Quote:
Originally Posted by scheong View Post

Looks like the BDP-95 bug affecting the SACD LFE level on the HDMI output is still there. I will forward this info to Oppo.

Make sure you tell them you've got the Oppo outputting SACD as PCM so they don't say it's your receiver.
post #36347 of 42717
Quote:
Originally Posted by Bob Pariseau View Post

Limiting the correction range allows ARC to concentrate its processing resources in the frequency range you want corrected. Which may result in a cleaner solution.

Yeah but from looking at where the dips and peaks start in my charts it seems ARC is set to "give up" just when the going gets tough. I guess this is by design to not "stress" the speakers from massive corrections.
post #36348 of 42717
Quote:
Originally Posted by AVfile View Post

Make sure you tell them you've got the Oppo outputting SACD as PCM so they don't say it's your receiver.

Will do.

Stanley
post #36349 of 42717
Quote:
Originally Posted by AVfile View Post


Yeah but from looking at where the dips and peaks start in my charts it seems ARC is set to "give up" just when the going gets tough. I guess this is by design to not "stress" the speakers from massive corrections.

I've no idea what you are talking about. You can change the Max EQ Frequency you know if you want ARC to correct higher up in frequency and believe the mic data up there is accurate. Keep in mind the mic data may NOT be accurate at the highest frequencies due to speaker directionality and environmental effects.

ARC's protective limit is that it won't try to provide more than +6dB boost to a dip. It doesn't pick a different default Max EQ Frequency on its own based on whether it sees treble problems.

If your speakers need a lot of correction across all frequencies, then instructing ARC to correct higher up may produce poorer results in the normal correction range due to the diversion of resources. Thus it is usually good to take what steps you can to improve the raw, uncorrected treble output first -- such as correcting speaker pointing or checking for improper grill mounting.
--Bob
post #36350 of 42717
Quote:
Originally Posted by scheong View Post

Hi Bob,

Looks like the BDP-95 bug affecting the SACD LFE level on the HDMI output is still there. My BDP-95 is on the latest official firmware (BDP9x-65-0302).

SACD test disk sound levels:
LF - 60db, C - 60db, RF - 60db, LS - 61db, RS - 61db, Sub - 68db

AIX bluray test disk sound levels:
LF - 60db, C - 60db, RF - 60db, LS - 61db, RS - 61db, Sub - 63db

I will forward this info to Oppo.

Thanx for your help.

Stanley

I'll repeat that test on my 93 in a bit and report back.

ETA: Once I've had a chance to check this, I'll reply to your post in this in the BDP-95 thread, since we should move this discussion over there until we are sure there's not a problem in your OPPO.
--Bob
post #36351 of 42717
Quote:
Originally Posted by Bob Pariseau View Post

I've no idea what you are talking about. You can change the Max EQ Frequency you know if you want ARC to correct higher up in frequency and believe the mic data up there is accurate.

ARC's protective limit is that it won't try to provide more than +6dB boost to a dip. It doesn't pick a different default Max EQ Frequency on its own based on whether it sees treble problems.

I am talking more the cutoffs for each speaker not the Max EQ freq. From what I see the targets are not being set very aggressively. Getting +6dB boost would be better than nothing.

For the higher frequencies the charts show that all my speakers drop off 3-6dB at around 10k (the fronts rather sharply; the surrounds more gradually). Would that appear to be consistent (i.e. trustworthy) readings and therefore justification for increasing Max EQ freq?

I was more curious about the cutoffs though. For example, ARC set the cutoff on my Energy Veritas Center to 95 Hz (it should be good down to at least 60) and that is right at a large peak in my chart (60 - 100 Hz). Below that is a large dip (40 - 60 Hz). I was thinking of this as "giving up" on the situation but I guess they chose to let the crossover filter take over early instead of applying cut, boost, then crossover.

Thanks,
Stefan
post #36352 of 42717
Just to not leave things hanging, it appears that Stanley has indeed found an OPPO player bug re his discovery posted above that SACD .1 channel level is roughly +5dB too hot.
--Bob
post #36353 of 42717
Quote:
Originally Posted by AVfile View Post

I am talking more the cutoffs for each speaker not the Max EQ freq. From what I see the targets are not being set very aggressively. Getting +6dB boost would be better than nothing.

For the higher frequencies the charts show that all my speakers drop off 3-6dB at around 10k (the fronts rather sharply; the surrounds more gradually). Would that appear to be consistent (i.e. trustworthy) readings and therefore justification for increasing Max EQ freq?

I was more curious about the cutoffs though. For example, ARC set the cutoff on my Energy Veritas Center to 95 Hz (it should be good down to at least 60) and that is right at a large peak in my chart (60 - 100 Hz). Below that is a large dip (40 - 60 Hz). I was thinking of this as "giving up" on the situation but I guess they chose to let the crossover filter take over early instead of applying cut, boost, then crossover.

Thanks,
Stefan

It looks like ARC takes into account the AMOUNT of correction it would need to apply if it used a lower Cutoff on a main speaker channel. If the Subwoofer measures as capable, then ARC does indeed end up picking a higher Cutoff for the main speaker and relying on the Sub to support that speaker below that point rather than forcing a lot of correction.

A peak with a dip just below it in frequency can look to ARC like the main speaker's natural rolloff has already started at a frequency above the peak. I.e., that the "dip" is in fact not a dip, but just the extension of the natural roll off of that speaker -- which means the peak just above that in frequency is an even BIGGER problem.

Sometimes the eye can see things here that ARC doesn't spot, and so lowering the Cutoff to use some of the lower frequency energy might be a good "tweak".

One thing to keep in mind though: The Crossover is not like a switch. It doesn't happen suddenly at one frequency. It rolls into effect over about an octave of frequencies (a factor of 2). THAT MEANS when checking to see if a a Cutoff is well chosen, you need to check for how good the correction is (i.e., how closely the Calculated curve matches the Target curve) for an octave BELOW the Cutoff.

In other words, a Cutoff of 60Hz is only "good" if ARC is able to produce good correction down to 30Hz -- one octave lower. If not, then the Cutoff should be raised above 60Hz. A Cutoff of 100Hz is "good" if ARC has good correction all the way down to at least 50Hz. The response curve is -12dB down one octave lower, so residual errors in the correction below that frequency don't matter as the basic signal is already attenuated enough down there that you won't hear them.

There are different requirements tugging in the other direction though. A Cutoff that's too high will move high bass into the subwoofer -- making it localizable (i.e., you can tell the sound is coming from it). This is particularly a problem if Center is given a high Cutoff because then dialog starts being heard from the Sub.

Try to keep the Cutoff for Center no higher than about 90Hz to prevent this. Of course if your Center really isn't capable of going that low, then you have a problem -- best fixed by replacing it with a more capable Center speaker.
--Bob
post #36354 of 42717
Quote:
Originally Posted by scheong View Post

Yes, I understand. The relative sound level between sub and mains should be the same between the AIX disk and Pentatone SACD test disk...if things are working correctly.

Just to reiterate, unless you are using a spectrum analyzer, the AIX disc is not useful for LFE channel calibration.

Did you find a THX Optimizer disc? That will be much more useful wrt PCM confirmation.
post #36355 of 42717
Quote:
Originally Posted by Roger Dressler View Post

Just to reiterate, unless you are using a spectrum analyzer, the AIX disc is not useful for LFE channel calibration.

Did you find a THX Optimizer disc? That will be much more useful wrt PCM confirmation.

Roger, I don't follow your concern here with the AIX LPCM test tracks. So far, every test I've done with them is consistent in result with other test tracks (including the THX stuff found on some discs). The AIX results are also consistent with what I would expect given my ARC solution (e.g., the small increase in Sub level associated with the retained Room Gain).
--Bob
post #36356 of 42717
Quote:
Originally Posted by Nick @ Anthem View Post

When ARC is active, LFE Bypass Xover is in effect. This means that redirected bass is crossed over at the Sub Xover frequency displayed in the setup menu,

Good.

Quote:


while LFE runs unfiltered at its native 120 Hz bandwidth.

Not so good. The problem with LFE is that it is not always properly limited to 120 Hz. So it is best to have an LFE filter all the time. And being able to set it, say, for Movies (120 Hz) and Music (80 Hz) is a great idea.

Quote:


Behind-the-scenes DSP is in effect to prevent combing the frequency response as a result of adding a signal to its delayed counterpart (all filters cause delay according to slope, frequency, and type).

Where would a delayed counterpart come from? LFE is not redirected bass, it is a different channel.

Quote:


Some time ago a magazine which checks bass management under all user options stated that when it came to non-standard configurations ours was the only one that they observed getting it right, primarily because of avoiding comb filtering issues.

That's good, as far as it goes. I presume they were testing with some sort of test signal that puts a frequency sweep into all channels simultaneously. It's a reasonable test, but does not represent most real-world content. No harm in dealing with it as you have, of course.

Quote:


I wish I could remember which magazine it was.

Probably one with David Ranada. Stereo Review? We helped make test signals for him back in the day.

Quote:


When LFE Bypass is not engaged, i.e. when a more conventional crossover is in effect, "Sub Xover" which is seen in the setup menu (and not ARC Targets) performs exactly as labeled - set it too low and you lose too much LFE. This is indeed why we provided a Movie and Music configuration starting long before ARC.

If "Sub Crossover" is a crossover, then why would any LFE signal be lost? If it is lost because it is a lowpass filter without a complementary highpass (and redirection), then it is indeed an LFE filter and not a crossover as I thought.

Is there a block diagram somewhere? Something like this? The 110 Hz filter is the one I'm referring to as the LFE filter. Is that the user adjustable "Sub Crossover"?

post #36357 of 42717
Quote:
Originally Posted by Bob Pariseau View Post

Roger, I don't follow your concern here with the AIX LPCM test tracks. So far, every test I've done with them is consistent in result with other test tracks (including the THX stuff found on some discs). The AIX results are also consistent with what I would expect given my ARC solution (e.g., the small increase in Sub level associated with the retained Room Gain).

Your result does not mean that every user will get a consistent result. If the bandwidth of the subwoofer changes, the SPL will change because the AIX LFE channel is 20 kHz wide. Two correctly calibrated subs, one that covers 10 Hz to 100 Hz and another that covers 30 Hz to 80 Hz will read different SPLs. But if you play the THX signal thru them, they will both read the same, as they should.
post #36358 of 42717
Quote:
Originally Posted by Roger Dressler View Post

Just to reiterate, unless you are using a spectrum analyzer, the AIX disc is not useful for LFE channel calibration.

Did you find a THX Optimizer disc? That will be much more useful wrt PCM confirmation.

Hi Roger,

No, I don't have a THX Optimizer disc. Can you recommend one? I will try a search on Amazon.

Stanley
post #36359 of 42717
Quote:
Originally Posted by Roger Dressler View Post

Your result does not mean that every user will get a consistent result. If the bandwidth of the subwoofer changes, the SPL will change because the AIX LFE channel is 20 kHz wide. Two correctly calibrated subs, one that covers 10 Hz to 100 Hz and another that covers 30 Hz to 80 Hz will read different SPLs. But if you play the THX signal thru them, they will both read the same, as they should.

I'm still not with you. If the problem is that the subwoofer is not capable of reproducing the full bass range -- and thus reads a lower SPL (compared to a sub with wider range) when you play this test track -- why SHOULDN'T its output be raised to compensate? When playing real content, the frequencies it can reproduce will be a bit overemphasized, but the frequencies it can't reproduce will be missing. On, umm, balance, isn't this the desired result?

ETA: And as for Stanley's case, the AIX tracks are reading the "correct" results -- the results we would expect after an ARC setup -- whereas it is the SACD test which is unexpectedly hot for the LFE channel. If I understand your concern, it would be that that AIX track might produce an SPL that is confusingly higher than a more constrained bass test track would produce. I.e., switching to a different, more constrained, comparison track instead of AIX could only make Stanley's observed SACD anomaly worse. Right?
--Bob
post #36360 of 42717
Quote:
Originally Posted by Roger Dressler View Post

The problem with LFE is that it is not always properly limited to 120 Hz. So it is best to have an LFE filter all the time.

LFE is not redirected bass, it is a different channel.

If "Sub Crossover" is a crossover, then why would any LFE signal be lost? If it is lost because it is a lowpass filter without a complementary highpass (and redirection), then it is indeed an LFE filter and not a crossover as I thought. Is there a block diagram somewhere?

The 110 Hz filter is the one I'm referring to as the LFE filter. Is that the user adjustable "Sub Crossover"?

Responses numbered to correlate with excerpts above:

1. Sampling rate for LFE is 240 Hz, no? Therefore it cannot have content above 120 Hz. Tom Holman's book (2nd ed) page 60:

http://books.google.ca/books?id=nnLA...0%20Hz&f=false

So my question is that even if the encoder's 120 Hz filter is not selected and the input signal has content above that frequency, how would it be possible to encode it without the result being loaded with aliasing artifacts? That would be a lot more concerning than any other implication discussed here on the playback end.

2. LFE may be a different channel but that doesn't stop anyone from putting the same content as other channels in it, for example with a pop album recreated in surround for DVD-A or Blu-ray. It's not like the kick drum or bass guitar are exclusive to the LFE track in the surround mix - there is overlap if not wholesale copy from L/R, which can remain full range in the recording. Even if it's only crossed over, limiting L/R bandwidth in the recording, there is still overlap and the phase effects from adding signals in the electrical domain (the summed sub channel) are a lot nastier than in the acoustic domain (phase-matching fronts and sub) since that involves decorrelation to varying degree. It also happens that most of the energy from kick drum and bass guitar is usually right around 80 Hz.

ETA: Page 3-6 in 46_DDEncodingGuidelines.pdf (use the file name as search term) in the last paragraph before section 3.5 says that essential info should never be exclusive to LFE and that LFE info essential to the listening experience should be copied to the fronts to ensure that it will be heard if the LFE channel is discarded, which is not only allowed but most often the case during downmix (AVM/D preserves it). In other words there's plenty of shared content out there between front and LFE channels.

3. The crossover configuration options in the Dolby Licensee Information Manual have all channels being summed with LFE before any filtering takes place, therefore once the summed Sub channel is run through the low-pass filter, redirected bass and LFE are rolled off alike. Again, this is not what happens when LFE Bypass is selected, as ARC always does. LFE Bypass selection is in the same setup menu as the crossovers in case anyone's looking for this.

4. It isn't.
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