Dr. AIX

Mark Waldrep, aka Dr. AIX, has been producing and engineering music for over 40 years. He learned electronics as a teenager from his HAM radio father while learning to play the guitar. Mark received the first doctorate in music composition from UCLA in 1986 for a "binaural" electronic music composition. Other advanced degrees include an MS in computer science, an MFA/MA in music, BM in music and a BA in art. As an engineer and producer, Mark has worked on projects for the Rolling Stones, 311, Tool, KISS, Blink 182, Blues Traveler, Britney Spears, the San Francisco Symphony, The Dover Quartet, Willie Nelson, Paul Williams, The Allman Brothers, Bad Company and many more. Dr. Waldrep has been an innovator when it comes to multimedia and music. He created the first enhanced CDs in the 90s, the first DVD-Videos released in the U.S., the first web-connected DVD, the first DVD-Audio title, the first music Blu-ray disc and the first 3D Music Album. Additionally, he launched the first High Definition Music Download site in 2007 called iTrax.com. A frequency speaker at audio events, author of numerous articles, Dr. Waldrep is currently writing a book on the production and reproduction of high-end music called, "High-End Audio: A Practical Guide to Production and Playback". The book should be completed in the fall of 2013.

13 thoughts on “Making the LFE Channel Go Boom

  • March 30, 2015 at 7:08 pm
    Permalink

    Mark,

    It seems to me that in doing your music mixes, there would be two valid approaches:

    You could create a .1 track with monaural low bass information, attenuated by 10db, to be automatically boosted back up on playback, or

    You could simply omit the .1 track and mix all the channels full range, and rely upon the listener to either use full range speakers or bass management that sends the low bass from any smaller speakers to the subwoofer(s).

    I think that the second approach would be the best for surround music mixed naturally, though I could see the judicious use of the .1 channel for the cannons in the 1812 Overture and similar sound effects.

    Reply
    • March 31, 2015 at 6:32 am
      Permalink

      Phil, you’re suggestions are appreciated but there are challenges with both. Remember that the boosting of the LFE channel is used only on Dolby Digital .1 LFE channels and not on the LFE outputs of SACD and DVD-Audio discs. If the manufacturers of AVR handled music discs correctly, then there would no need to modify my LFE output. When I mix my projects, I don’t use bass management. That means the the main 5 speakers get all of the program material. I dial up the “boom” output to the LFE channel but I DO NOT raise the “non boom” knob (which would remove the low end signals from the mains). The result is that the mixes are enhanced by the addition of a subwoofer but they work just fine without. If you solo (isolate) the output of the subwoofer you will notice that the sound is band limited to about 70 Hz (not the usual 120 Hz in typical bass management). The effect is subtle but does make a difference in the overall sound.

      The omission of the LFE channel is problematic as well. I have received phone calls and emails from customers asking if I use the LFE channel. There was a set of the Beethoven Symphonies that didn’t use the LFE and customers with sub felt cheated. I think my approach is a good compromise. I’d be interested in how many customers have experienced excessive low-end levels. I’ve certainly not heard about any problems.

      Reply
      • March 31, 2015 at 7:18 am
        Permalink

        Mark,

        Are you even still creating new DVD-Audio disks?

        While the Oppo Blu-ray players can play DVD-A and SACD disks, the 10 db boost of the LFE channel on playback applies not only to “DVD style” Dolby Digital and DTS, it also applies to Dolby TrueHD and DTS HD Master Audio, which I assume are what you use on your Blu-rays.

        I’ve not bought your mixes on disk but as downloaded FLAC versions of your PCM 5.1 stage perspective mixes. Since no Dolby or DTS processing takes place on playback of these files, and thus presumably no boost of the LFE channel, I’ve not had any problem with the LFE being too hot. I play back all my multichannel material networked off my LAN through an Oppo BDP-93, running its multichannel analog output into my pre-HDMI Yamaha RX-v457.

        I have Steely Dan’s Gaucho in multiple versions, including the multichannel mix in both SACD and DVD-A copies. While the 96/24 5.1 DVD-A copy sounds glorious, the 5.1 SACD sounds muddy, since its LFE channel was, per the SACD spec, not cut back by 10db. (The SACD’s CD-compatibility track sounds fine.) My past reading has suggested that SACD was “odd man out” with respect to not using the 10 db cut. My DVD-As appear to have uniformly had the 10 db cut built in.

        I’ve read in user support forums that some AVRs have a control buried in their menus to enable and disable the 10 db boost (though mine does not). I assume that such controls are limited to the LFE channel.

        However, general speaker trim controls – whether in the AVR or on the back of the sub itself, are not only an annoyance to adjust on a per-disk basis but would cut back the managed bass from the smaller speakers along with the LFE.

        Phil

        Reply
  • March 31, 2015 at 12:37 am
    Permalink

    Guess I’m a little slow but I’ve read all the installments on bass management and still can’t wrap my mind around the need for the +10 db boost of the LFE channel? Why isn’t it flat with the rest of the speaker array? Why don’t they just boost it on the mastering end if everyone needs it? I’m confused on this issue.

    Reply
    • March 31, 2015 at 6:35 am
      Permalink

      Because of the potential for digital clipping. If the mixes have a -10 dB level, the system can accommodate the very loud EFX and then be brought up to full level in the analog outputs of the receiver.

      Reply
  • March 31, 2015 at 1:26 am
    Permalink

    Hello

    The REL company’s long-established, well-reviewed UK range of ‘SubWoofers’ has two inputs that are controlled separately. One for the 5.1 for movies and the other directly from the stereo POWER outputs of an amplifier. http://rel.net/rel-story/technology/

    This way, the work with both stereo music to augment the bottom end of speakers and the Effects channel in movies.

    Regards

    Stuart

    Reply
    • March 31, 2015 at 6:39 am
      Permalink

      Thanks, it’s refreshing to see a company taking the time to understand the issue AND include a solution in their products.

      Reply
      • March 31, 2015 at 10:37 am
        Permalink

        Hey Mark
        I just want to also bring to your attention another product, check out the most musical sub I have ever heard. http://www.rythmikaudio.com/amplifiers.html. Especially the Amp model A370-xlr3. it also has dual inputs that allow for separate .1 and low Hz inputs. In my system I set the sub crossover at 40Hz in the AVR and then crossover the left and right channels with a highpass at 200hz (or there about) and send it to the other side of the amps, two subs. I am not aware of two many instruments that go below 40hz other than maybe a pipe organ

        Reply
  • April 2, 2015 at 5:15 pm
    Permalink

    I’ve struggled with bass management connection issues playing back DVD-A & SACD discs and now FLAC & DSF 5.1 files. The solution I came up with is a passive summing box that I built out of a pro DI box. It takes the left, right, and LFE channels and sums them to mono (with 1,000 ohm resistors) then balances the mono signal with the DI transformer. The balanced line from the box runs 30 feet to a remote digital crossover and power amps for the six subs. The box works very well and I wonder why no one has built something like it for the home theater market.

    Reply
    • April 3, 2015 at 9:46 am
      Permalink

      Very clever, Russ. And thanks for the detailed description. I’m wondering about the “power amps for the six subs” part of your comment. Do you really run six subwoofers or are these the low end drivers of your main speakers?

      Reply
      • April 3, 2015 at 11:40 am
        Permalink

        Yes, I run six subs. I’ll keep the description brief. The subs are grouped at different places around the room in a semi-“swarm” configuration. Each group of subs use different crossover, eq and delay settings and are powered by pro digital amps.

        Reply
  • March 14, 2019 at 9:36 am
    Permalink

    Hello! I wonder if somebody could help me. I’m having problems with lfe reproduction on my Denon X-1200W receiver and Yamaha NS-SW200 subwoofer. When Audyssey is on (AUTO mode), watching DD 5.1 content the subwoofer reproduces flobbing sound even at 40% volume. On Direct mode reproduction of low volumes is better, but the ‘flobbing” sound is again noticeable at high volume… I’m wondering what is causing this. The subwoofer is brand new… I would really appreciate any kind of help…

    Reply

Leave a Reply

Your email address will not be published. Required fields are marked *

sixteen − 1 =