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LRS Comes for Good

Further Magneplanar LRS listening impressions including how they render some classic rock material. What works, what falls flat, and some speculation as to why.

Dismal Wizard used Aunt Nancy Pelosi’s CARES Act stimulus payment to purchase the Magnepan Magneplanar Little Ribbon Speakers shown flanking Rocky and Missy (in red). The Maggies (audiophile speak for any Magneplanar speaker) are merciless. Things that sound ordinary on box speakers sound gorgeous and things that sound impressive on box speakers can fall flat on the Maggies. It’s all about the coherency and dipole radiation pattern of Maggies. They respond differently to finished records that do box speakers.

In short, the Maggies seem not to like records that are heavily processed in production. Compression and reverb are evil. The end result is a flat, lifeless mess. More simply mixed records like singer songwriter fare and jazz present well, sometimes brilliantly.

References

  1. https://youtu.be/d3IiH-SjhBE Secret Magnepan Loudspeaker Set up Guide.
  2. https://youtu.be/YNrttBfo29s Penn State video explaining monopole and dipole acoustic radiators.
  3. https://youtu.be/PXw_f-9ArUk, Snarky Puppy recording Immigrance, Part 1. Bob Reynolds VLOG
  4. https://youtu.be/dP2KX_AIKDE, Snarky Puppy recording Immigrance, Part 2. Bob Reynolds VLOG

Revision History

  • 2020-10-9: Added Bob Reynolds VLOG titles showing the recording of Snarky Puppy’s Immigrance record.
  • Revised recording process discussion to better explain what happens in the session, mixing, and mastering phases of the process.
  • Explained dipole vs monopole loudspeakers with attention to how the back wave and front wave add and how placement affects the superposition of the two at the listening position.
  • Explained how Maggies are coherent, that is fundamental and harmonics are in proper phase relationship.

Records auditioned

This past week I went back and auditioned a slew of classic pop records from my miss-spent youth. Some are old friends and others are things I found kicking around in Qobuz or Tidal. All of these are things I like and many were first heard on Acoustic Research 4’s or Advents. Most have also been heard recently on my Dhalquists.

  1. Beatles: Abbey Road
  2. Beatles: Seargent Pepper
  3. Moody Blues: Days of Future Passed
  4. Pink Floyd: The Wall
  5. Pink Floyd: Dark Side of the Moon
  6. Judy Collins: Colors of the Day
  7. CSNY: Four Way Street
  8. Elton John: Elton John
  9. U2: War, The Joshua Tree
  10. Tim Buckley: Dream Letter
  11. Okuden Quartet: Every Dog Has His Day …
  12. Blood Sweat and Tears: Child Is Father to the Man
  13. Cowboy Junkies: The Trinity Session
  14. King Crimson: In the Court of the Crimson King
  15. Blues Project, Projections

What Makes Maggies different?

Magneplanar speakers do not have a baffle but they do have a front and back and radiate from both sides. That is, they are dipole radiators. The back wave is born 180 degrees out of phase from the front wave. This means that Maggies must be placed with some care as the front side and back side energy superimpose at the listening position. How they are placed affects the low frequency voicing by determining how the back wave is reflected toward the listening area. To work properly, they need to be 1 to 2 meters (3 to 6 feet) off the rear reflective surface.

Put another way, adding 6 to 12 milliseconds of delay (343 meters per second in air) to the back wave lets the magic come out. Basically, the back wall distance determines which reflected frequencies combine constructively making them more prominent and which reflective frequencies combine destructively making them less prominent. This is most apparent in the lower frequencies. Placement is largely a matter of taste.

Box Speakers have no back wave

Box speakers go to great pains to kill the back wave by enclosing the speaker in a baffle containing absorbing material that swallows up the rear wave. In the Dhalquists, the woofer is in an infinite baffle (damped box). The various tweeters have heavy felt attached to absorb the back wave. The drivers are staggered to put the radiating surfaces in a plane and the crossover is designed to control phase shift through each passband.

Maggies are Planar Speakers

Magneplanar speakers are basically a printed circuit trace hand applied to tensioned mylar film. The film and conducting trace have a very low mass making them very quick and very phase coherent. The bass and treble drivers are in the same plane so low frequency fundamentals and their harmonics are in phase.

The bass panel reproduces frequencies below about C4 (C3 in Europe) — 256 Hz middle C). The tweeter reproduces the rest of the pass band. The relative size of the two drivers determines the tonal balance of the speaker.

The radiating areas are long and narrow compared to the wavelengths being reproduced. This lets each driver approximate a finite length line source for most frequencies in the passband. This means that the speakers tend to radiate cylindrical waves while box speakers radiate as a point source. This affects how the music fills the space and the perception of the various instruments being reproduced.

Some reviewers feel that Maggies are base shy. My spectrum analyzer (an iPad app) says differently The Maggies, even the LRS, easily reproduce low bass. The spectrum analyzer’s waterfall display shows that the Maggies are putting upright bass and bass guitar notes in the 40 to 60 Hz range into the room with authority and detail. I would say that a subwoofer is needed only for organ music.

Wonkie Drumming

The low mass makes them able to reproduce high frequency and transient sounds with aplomb. They are particularly good at reproducing what Jacob Collier calls “wonky rhythm” or “wonky drumming”. Really strange signatures like 15/4 are the rule of the day in popular and jazz music. Each beat may have 4 or so percussion events with each of the sounds being small, just taps with huge swing (percussion off the signature beat or skipped signature beats). Rim taps (not shots) and head taps with various sorts of sticks are all the rage today. This sort of play is very understated and lets the melody and harmony instruments dominate.

Maggies are also brilliant at reproducing hand drumming, tuned tom toms, and brushwork common to jazz. And if the recording and mix engineers managed to capture the cymbals, they will sound like live. Drumming is tough to reproduce because each sound is essentially a wide bandwidth impulse. The drum sound is a composite of the impulse plus the free response of the drum membrane at the resonant frequency plus overtones resulting from striking the drum head off center. The speaker splits up the various parts of the sound directing some energy to the low frequency driver and the rest to the high frequency driver. To have a realistic drum sound, the speaker must preserve the relative loudness and phase of the reproduced sound energy.

Because they are so fast, Maggies preserve all of the phase relationships among the various fundamentals and overtones, keeping them all separate so that they superimpose naturally at your ear. Record [11], Every Dog Has Its Day has both wonky and regular jazz drumming and a brilliantly recorded drum solo that puts the kit right in the lounge. Tuned toms and cymbals are right there.

This phase coherence also allows Maggies to reproduce depth provided that microphones were placed properly, phased properly, and synchronously sampled for digital transmission or mixing.

The Production Process

The process of record production happens in three phases, the session, mixing, and mastering. There is a clear separation of responsibilities in each phase. In his VLOGS, Bob Reynolds gives shows how he learns his horn parts and how the studio records the parts in session. Bob is an excellent sax player and story teller. These to videos are worthwhile.

Session Recording

In session, the musicians create the music and the recording engineer records it to media. The goal is to capture the instruments cleanly with equalization introduced to compensate for room acoustics and to remove undesirable artifacts like the buzz of a drum support loose part. Some additional equalization may be applied so things can be fit together but this can happen during record mixing just as easily. The goal here is to get good clean capture of each artist. The take is monitored using high quality headphones of known characteristics. The goal is to recognize problems so they can be mitigated during recording.

Mixing the Record

Mixing puts all of the parts together. The producer chooses the tracks to appear, combines them by setting faders and pan pots, and may filter them further so they fit together without excessive energy in any range. The region around 2200 Hz will be cut some to make room for vocal information present around here.

The mix engineer will do most of this work using monitoring speakers that help him identify mix problems. They may not be high definition, they just need to reveal issues in the mix. The mix engineer and producer will use high quality headphones to make artistic judgements. Increasingly, these are planar magnetic headphones from Audeze or other upstart manufacturers or classic dynamic headphones like the Sennheiser 550 HD and 650 HD.

Mastering the Record

The mastering phase prepares the mix for distribution on real world media. In this phase, a CD mix, LP mix, and streaming service mixes will be produced. In this phase, the mix equalization and compression are tailored to an audience, listening environment, media, and playback media. A radio mix will be produced specifically for consumption by commuters driving to and from work. The mastering engineer will do this work assisted by automated mastering tools. Any problems with the producer’s mix that affect mastering will be mitigated.

So How Does This Effect Playback?

It all depends on the record. Tracking (recording the individual microphone channels), mixing (combining the channels into a performance), and mastering (preparing the channels for the distribution and playback) all influence the sound. The choice of instruments, musician skill, microphone choice, and track equalization have a big effect. It never gets better than what was captured at the session. Everything has to be put together to preserve the timing — so that the instruments are all playing together (in time).

Modern Multitrack Sessions

In a popular recording, the drummer and bass player may be in isolation booths. They are listening to a monitor mix in their headphones and playing along with that mix. Everybody is playing to a click track that serves as a metronome for the session.

The Bob Lawrence video shows the horns being recorded in a separate room built specifically to record the Snarky Puppy horn section. The room is off square and the framing is open to give diffuse reflections off the walls, ceiling, and wood floor. The horn players are listening to the rest of the band via a monitor mix tailored to their needs. Snarky Puppy is big with 3 percussionists, several keyboards, bass, a guitar or two, and synths. This is a lot to mix together and to keep separate so each part can be weighted and placed properly. Tracking the horns separately helps.

Virtual Sessions

It is not uncommon for a record to be recorded in virtual session. Musicians will record at home or book a local studio to record their parts listening to a master track provided by the artist that depicts the melody and rhythm of the track and may include the lead vocal. It will have a click track that represents the base timing of the piece. The artists will play their parts in time with the click track and in tune with the base track of the record. The tracks will be returned to the producer, typically as ProTools or Logic sessions to be imported into the production session for mixing and mastering.

During the Session Takes

Typically most tracks go through a microphone preamp, equalization, and finally an analog to digital converter. Live recordings often catch the sample stream from the front of house tracks at the preamp. The goal is to get a clean mixable capture of the artist’s contribution to the record.

The sample stream is divided into frames that indicate the number of samples present, the sampling rate, and the time of the first sample and the frame number. This metadata allows the original sample stream to be reproduced and for gaps to be detected. The audio workstation holds this data in memory for manipulation and playback.

During Production

The mix engineer introduces effects during production. The recorded signal passes through additional filtering, compression, limiting, reverberation, and other devices to get the producer’s desired sound. The production engineer will establish the instrument balance and placement with their choice of fader and pan pot settings.

In a normal musical recording, the mix is straight-forward. It aims to properly weight each instrument in the sound field that is to be reproduced in the listening space. Producers use a number of different playback rigs to evaluate the mix. Studio monitors are usually designed to let the producer spot and correct errors in the tracking, for example, a room resonance or a loose part buzz on a drum kit. Various other rigs reproduce auto sound, important to pop, and various lounge playback systems, typically with bookshelf speakers. It is rare for high definition speakers to be used in making mix decisions but high definition planar magnetic headphones are commonly used.

In a record like The Wall lots of reverberation and filtering are added along with environmental sounds and sound effects to tell the protagonist’s story. In the case of The Wall, there is too much manipulation. Box speakers are kinder to this material (that back wave is suppressed). but the Maggies make it sound weird.

Pink Floyd’s Dark Side of the Moon has a number of environmental sound loops like the till and coins of Money. Or the deep heart beat. Both the environmental sounds and the music are mixed relatively free of reverb and distortion and Dark Side comes off as a shining gem of a rock record.

Many “classic rock” albums sound flat and just off. Sometimes, its a single track. At other times, it is the whole record. The King Crimson record is a good example. It comes off flat and boring on the Maggies but sounds pretty good on Dhalquists. Another mellotron rich record, Moody Blues Days of Future Past, survives better but is still flat compared to the Dhalquist rendering. The Dhalquists are more listenable for these records.

In some cases, the Maggies do better than the Dhalquists. Blues Project’s Projections cleans up and sounds good on Maggies. On my box speakers, the opening tracks are aggressively bright. Some of it is the lead guitar effects but the mix is hot also. A similar thing happens with Us’s War. The Maggies sort it and take the edge off (sorry pun not intended, Edge).

In Mastering

One of the nice things about digital recording is that, once the track is captured, things can happen at leisure. Filtering, weighting, and combining of the tracks can take as long as it needs to take as the resulting samples contain the position and timing of each frame of the mixed recording.

The production team will make a performance master that is the finished result of production. The mastering engineer will derive master recordings for CD, LP, lossy streaming services, and lossless services and sales. The masters sent to Apple Music, Spotify, etc are equalized and compressed to the specifications of the service.

The producer may also make radio edits that deal with off-color language, length needed for air play, and playback in various environments, most commonly by car radio. The master is equalized and compressed to compete with car wind and road noise. Vocals will be manipulated to stand above the ambient noise.