How do you get bass when you don't have bass management?

[sukothai]

I've heard mention in several threads in the past that it is difficult to create a universally correct .1 channel from a 4 channel quad source. My problem is that I do 80% of my listening in my car; which doesn't have bass management for DVD-A. I've followed debate of this issue in other threads with keen interest, but have never heard a satisfactory solution. I've been experimenting with my own conversions and the best solution I've found so far is to sum the 4 quad channels, attenuate the sum by 3-6 db and lay this down as the .1 channel. To me, this approach sounds great in my car and even in my full sized speakers plus sub at home.

The discussion of sufficient bass in the recent Rhino Chicago Transit Authority Quad release and associated .1 channel discussion has again caused me to doubt my methods. I'd like my conversions to be as correct as possible, so I'm re-examining my approach and looking for advice. Here are my questions:

1) Is an attenuated sum of the 4 channels a correct way to create the .1 channel?
2) Is there a better way to deal with the bass management problem in DVD-A?

Thanks for listening and please let me know if I'm completely daft. @:

 

[georgeshannon]

A sum of the attenuated 4 channels plus removing frequencies above 80 Hz is a good approach to a .1 channel. Removing the higher frequencies will reduce distortion in the SW.

 

[user 4725]

I've seen a method which recommends constructing a LFE channel by summing the four channels and then staring to filter from 80Hz, rolling off completely at 120Hz. You might find that produces a slightly better effect.

 

[DKA]

There was some testing which I was assisting on with a method which would help you go from 4.0 to 5.1 utilizing Plogue a few months ago. While the results weren't something I thought were satisfying (it really only worked well on a very small percentage of extremely discrete 4.0 titles, and those are the ones folks like to listen to "as is" anyway), the approach to the .1 was exactly what you describer above, sukothai.....taking all four channels and driving them to the sub.

Which begs the question: is there interest in a method-based way to go from 4.0 to 4.1 or, even, 5.1?

 

[sukothai]

Which begs the question: is there interest in a method-based way to go from 4.0 to 4.1 or, even, 5.1?

My first and greatest interest (and purpose of this thread) is to stay true to the 4.0 mix and solve the bass management problem with DVD-A. So; 4.0 to 4.1 only for this thread. However, being a surround enthusiest, I'm interested in all conversion methods and would like to hear about 4.0 to 5.1 in a different thread.

 

[Kal Rubinson]

I hope this does not side-track the discussion but none of these is possible:
"create a universally correct .1 channel from a 4 channel quad source"
"constructing a LFE channel by summing the four channels and then staring to filter from 80Hz, rolling off completely at 120Hz"
"a method-based way to go from 4.0 to 4.1 or, even, 5.1"
"So; 4.0 to 4.1 only for this thread. "

All of these schemes are bass management, not the creation of the .1 signal which is LFE and unique, i.e., not shared by anything on the other channels. Creating a signal for a subwoofer does not result in a .1 channel.

The OP properly asks "My first and greatest interest (and purpose of this thread) is to stay true to the 4.0 mix and solve the bass management problem with DVD-A." I do not know if there are add-ons for this but it should be inherent in the main system. (My car system has a dedicated subwoofer and all bass is rerouted to it. There is no .1 channel but the bass is satisfying.)

Kal

 

[DKA]

one VST option (and the one the SBU folks would most recommend) is this:

http://pcfarina.eng.unipr.it/Public/BassManagement/BassMan.htm

I have some issue with his +10 db stuff (actually, I think that's quite insane), but perhaps this would work for some people. Any program that can host VSTs for playback (SF, Foobar, Plogue) can utilize this. If anyone has any further more techie questions on this, I'd suggest asking on SBU.

I have no clue as to car-based solutions, etc. I take the subway.

No one is trying to hijack this thread, FWIW. What I had originally said was that, as part of an (as of the last effort made, failed) experiment, some steps were taken to do just what the poster asked. I asked an aside if there was even any interest in such an experiment. We're all grown adults here. I'm sure we can handle that.

 

[sukothai]

All of these schemes are bass management, not the creation of the .1 signal which is LFE and unique, i.e., not shared by anything on the other channels. Creating a signal for a subwoofer does not result in a .1 channel.

By summing the 4 channels to create a .1 channel I mean:

1) Capture the 4 audio tracks to Audition from a quad source.
2) Bounce them all down to a new single track.
3) Reduce the bounced down track by 3-6db in Audition.
4) Create a 4.1 DVD-A disc from these 5 tracks using the bounced down and attenuated track as the LFE.

Are you saying this is bass management? I thought bass management was something you did with a disc after it was produced, not while producing it.

- Ben

 

[sukothai]

one VST option (and the one the SBU folks would most recommend) is this:

http://pcfarina.eng.unipr.it/Public/BassManagement/BassMan.htm

The above SBU reference is for Dolby Digital. The LFE in the DVD-A spec is very different from the LFE in Dolby Digital. The DVD-A spec says the LFE channel is full range and could even be treated as an additional discrete audio channel. Most DVD-A setups use this channel for the subwoofer, but I have heard of discs that use it as another discrete channel. Maybe the prejudice against LFE is because most think of it in the Dolby Digital (or DTS) sense. Not the DVD-A sense.

Again, someone please set me straight if I'm not thinking correctly here.

- Ben

 

[Kal Rubinson]

By summing the 4 channels to create a .1 channel I mean:

1) Capture the 4 audio tracks to Audition from a quad source.
2) Bounce them all down to a new single track.
3) Reduce the bounced down track by 3-6db in Audition.
4) Create a 4.1 DVD-A disc from these 5 tracks using the bounced down and attenuated track as the LFE.

Are you saying this is bass management? I thought bass management was something you did with a disc after it was produced, not while producing it.

- Ben

Yes, it is. I was under the impression you wanted to do this in your car but it is bass management in any case. It will, of course, create a .1 channel although I would not call it LFE anyway. I recall an old MartinSound device that would do this as, indeed, would the late, lamented Outlaw ICBM, a consumer device.

 

[sukothai]

Yes, it is. I was under the impression you wanted to do this in your car but it is bass management in any case. It will, of course, create a .1 channel although I would not call it LFE anyway. I recall an old MartinSound device that would do this as, indeed, would the late, lamented Outlaw ICBM, a consumer device.

I'll have to disagree. The bass management that I am familiar with is the ability to control what signal goes to your subwoofer real-time while the music is playing. I have an Outlaw ICBM on one of my home systems, but in this case, I am creating a disc with a fixed signal that will be directed to the car subwoofer by the DVD-A player in my car. I create the disc at home on my PC and then play it in my car with the fixed .1 subwoofer channel. My goal is to create a disc that is just like any other store bought DVD-A disc with a fixed .1 channel. You will note that in my original post, I purposely did not call this the LFE channel, because it is not. I think there is a lot of confusion about the DVD-A .1 channel.

 

[seriousfun]

...The discussion of sufficient bass in the recent Rhino Chicago Transit Authority Quad release and associated .1 channel discussion has again caused me to doubt my methods. I'd like my conversions to be as correct as possible, so I'm re-examining my approach and looking for advice. Here are my questions:

1) Is an attenuated sum of the 4 channels a correct way to create the .1 channel?
2) Is there a better way to deal with the bass management problem in DVD-A?

...

(sorry if I was a bit harsh on the CTA thread. and you're probably far less daft than me )

Bass Management is strictly a speaker system issue. Tony Grimani and others at Lucasfilm came up with this to specify how consumers could integrate their subwoofers with main speakers in their (small) living rooms with multichannel systems. This involves summing all six channels to the subwoofer, applying a low pass filter there to keep high frequencies from the subwoofer, and applying a high pass filter to the mains . These filters form a crossover. The ideal crossover point is where each main speaker is down 3 dB - where it's not big enough or the room can't support bass from that location - but they chose 80 Hz to provide a repeatable standard that could apply to a wide variety of systems and avoid confusion and the need for sophisticated measurement.

The LFE channel was added to cinema sound to take the load from main speakers, letting a dedicated subwoofer system play the booms and bangs. The LFE content survives to DVD etc. mixes in a channel limited in frequency in most cases. No music or parts of the music are commonly if ever mixed to the LFE channel in a movie mix - there is already more than enough headroom for music in the main channels.

With home systems and car systems , bass management is used to integrate the subwoofer. Set the crossover and the subwoofer plays the lows while the mains play the highs, and everyone's happy. This should be used unless your main speakers truly go down to 20 Hz (or as low as or lower than your subwoofer). I have a Sony MEXDV2000 that applies this crossover (playing SACD at 48k...nothing's perfect) to everything - what car system do you have?

There is no need for a music mix to include an LFE channel. We've done well with one or two channels to handle bass well for decades, and now we have up to five speakers to handle that. Some (maybe most) music mixers make the mistake that unless the LFE channel is lit up consumers aren't getting their money's worth (I wish that was the only problem with marketing SACD/DVD-A), so the do the mix you suggest or put bass guitar and kick drum down there (cello in Eleanor Rigby on the Beatles' Love), resulting in a mix that really doesn't work anywhere. Mixes without LFE channels work everywhere, at least as well as 1- or 2-channel mixes have for about a century, dependent on the speaker system that follows.

What car system do you have? Does your subwoofer only play when you game a 4-channel mix with a summed LFE channel? I can't imagine that the car system doesn't have an appropriate crossover to make its subwoofer play no matter what the source. If x.0 discs don't seem to have enough bass, a summed LFE channel is nothing more than an equalizer and phase shifter for the low end. A properly integrated subwoofer is the answer.

 

[Kal Rubinson]

I see but what would you call it other than bass management?

I do think a .1 channel that contains anything other than LFE (i.e., rerouted bass) is unfortunate since it requires a subwoofer. Those signals would be rerouted to the subwoofer in systems with a properly installed sub and play through the main channels in systems with full range speakers.

 

[sukothai]

There is no need for a music mix to include an LFE channel.

Agreed, music has no need for an LFE channel, but it does have a need for low frequencies to be directed to the sub and I'm now thinking the reason this is an issue with DVD-A is because of pre-HDMI DRM. For the same reason you cannot legally get to the digital stream of DVD-A channels -- the car receiver cannot process the main channels and direct them to the sub. With pre-HDMI DVD-A, the receiver is stuck with the analog output from each channel and is not allowed to process the digital stream. That's why the Outlaw ICBM was created with 6 analog in/outs. It does all the work in the analog domain.

I came up with this channel summing solution after using the ICBM with, and analyzing the anolog outs of, retail DVD-A discs. I noticed the .1 channel was typically just the mixed down audio of all the main channels. I didn't want to add the equivalent of an ICBM to my car system, so I added the .1 channel to my quad conversions and it has worked great. I suppose you could say I'm doing my bass management as I convert the quad source. The difference is only the volume level can be tweaked at play time. I've found it best to leave the track untouched (other than a little attenuation) and let the self powered sub in the car do any frequency filtering necessary.

My car system is a JVC KW-AVX706 and a standalone self powered sub. It does all the crossover stuff and would make Tony Grimani proud with DTS and Dolby Digital. The issue is with DVD-A. DVD-A does not let Tony decide what goes to the .1 channel. The author of the DVD-A disc gets to make this decision.

I have considered rewiring the car so all main channels go through the sub and use the sub's built in crossovers, but I believe I'm doing the exact same thing by bouncing these main channels down to a .1 channel in software; which then drives the sub. I was hoping for some validation of my approach, but it is turning out to be much more controversial than I expected.

- Ben

 

[sukothai]

I do think a .1 channel that contains anything other than LFE (i.e., rerouted bass) is unfortunate since it requires a subwoofer. Those signals would be rerouted to the subwoofer in systems with a properly installed sub and play through the main channels in systems with full range speakers.

My disc plays just fine on a system without a subwoofer. The 4 mains still have the full range and are untouched. When I play it through my QRX-9001 and 4 M&K S-5000's -- it sounds fantastic. I wish I could fit the S-5000's in my car. :banana:

 

[neil wilkes]

LFE is not a sum of the main channels with an LPF applied.
It is a dedicated channel all of it's own, and is created during the mixdown.
Re-routing from main to Subwoofer is bass management.
A Subwoofer is not the same as an LFE, although the 2 terms are often and incorrectly mixed.
LFE exists to extend the response of a typical system from 20-20 to lower than this, often as low as 10Hz. It also extends the headroom in the main system by allowing subsonic content to be deliberately fed to a dedicated channel and not take up range & excess energy levels in the main channels.
A subwoofer, on the other hand, is there to take all the bass summed from the main channels on sub/satellitesetups where the bass response may be crossed over as high as 500Hz, although 250 - 300 is more commonplace. A summed bass signal is not a .1 channel. A subwoofer is not the .1 channel either. It's the entirebass content, with nothing at all below the crossover point included in the main channels.
An LFE is additional to the bass response in the main channels, and in mixing the main channels are correctly treated as full range 20Hz - 20kHx as a mnimum (mine go from 40Hz to 35kHz).

Correct monitoring requires correctly setting up too. All too often the .1 on DVD-Video discs is at +10dB relative to the mains, and needs correcting.
Your Bass Management should be set correctly for your system, and the correct setting is dependant on your personal likes & dislikes, but I would begin by calibrating the entire system using measured files where we have an absolutely known level (RMS) of in-band filtered Pink Noise. Once your monitoring system is accurate, all else flows smoothly.

Would anyone be interested in a detailed method to do this?
You can do it with a Radio Shack hand-held dB meter, or get really, really exact.

 

[seriousfun]

My disc plays just fine on a system without a subwoofer. The 4 mains still have the full range and are untouched. When I play it through my QRX-9001 and 4 M&K S-5000's -- it sounds fantastic. I wish I could fit the S-5000's in my car. :banana:

As with everything - whatever works. But are you sure you don't have the bass management engaged at 80 Hz on your Denon or Pioneer receiver (I'm not sure from your profile which is used with your S-5000s. The S-5000s were designed to work with an 80 Hz crossover point, and I wouldn't call them full range.

 

[sukothai]

LFE is not a sum of the main channels with an LPF applied.
It is a dedicated channel all of it's own, and is created during the mixdown.
Re-routing from main to Subwoofer is bass management.
A Subwoofer is not the same as an LFE, although the 2 terms are often and incorrectly mixed.

I agree with you mostly, though I've got questions about some details in your reply. But this thread is not about what an LFE or .1 channel is or isn't, it is about how to make a DVD-A quad conversion sound good in both my house and my car.

I'll try to restate my problem. My car receiver will not apply cross-over logic to the mains with a 4.0 DVD-A; so I get zero signal out of my subwoofer with a 4.0 DVD-A in my car. I am trying to create a DVD-A that has two peronalities:

1) It has the full range of sound in the mains; so it will sound correct with my sub-less QRX-9001.
2) It has at low frequencies in the .1 channel; so it plays well in my sub-plus car.

The easiest way I've found to accomplish the above is to bounce the mains down to the .1 channel. Do you see a problem with this method?

Thanks, - Ben

 

[sukothai]

As with everything - whatever works. But are you sure you don't have the bass management engaged at 80 Hz on your Denon or Pioneer receiver (I'm not sure from your profile which is used with your S-5000s. The S-5000s were designed to work with an 80 Hz crossover point, and I wouldn't call them full range.

As stated above, the S-5000s are hooked up to my Sansui QRX-9001. There is no 80 Hz crossover point on a QRX. And they sound just fine without a subwoofer. But this thread is not about the home system, it is about the 4.0 DVD-A problem with the car system.

 

[seriousfun]

And they sound just fine without a subwoofer.

Surprising, but again, whatever works! I worked for M&K for a long time, I know those speakers intimately, and I never listened to them without a subwoofer.

But this thread is not about the home system, it is about the 4.0 DVD-A problem with the car system.

I understand, but electrical and acoustical considerations convince me that an analog crossover right before the power amplifiers is best, whether the system is in a home or a car. I though about putting one of our ManagerMAXs in my car with an appropriate power supply (then I can run SACD at full resolution) but I haven't tried it.

Again, it's unfortunate to me that many mixing engineers have chosen to create an LFE channel for a music mix as you have, but life goes on.