Thursday, September 11, 2014

Perception and Failed Illusions

Perception and Failed Illusions

Does a muffled band in a rehearsal room down the street sound more 'live' to you than a high def recording played through high quality stereo? Or have you listened to a recording and thought "whoa shit, I thought that was band, but it was just a recording played through speakers?"  Is it just live music that defies realistic reproduction or do these same perceptions apply to voices, fireworks and just about everything else we try and recreate through loudspeakers?

It seems there is something about a live band playing, even muffled and far away that divulges its aliveness. A certain rawness, dynamics, dispersion from the sources, perhaps multiple source locations. If these observations are taken to be correct or at least in the realm of close, what is especially interesting is that frequency response appears to have little to do with whether we perceive something to be real-time live. Comparing the muffled band a block away versus direct exposure to Hi-Fi wherein clearly the Hi-Fi has a distinct advantage in presenting a wider and less altered frequency response, yet somehow the live band sounds more real.

Quite puzzling indeed and perhaps this perspective lends some credibility to why so many audio people have such an affinity for audio gear that exhibits less than flat response and less that technically ideal sonic characteristics. Perhaps, just perhaps we are focusing on the wrong aspects as a starting point and that is why sonic realism is so illusive.

Oh, and just a thought on making sound reproduction more real. What if rather than focusing on frequency response and accuracy of the reproducer we instead focus on eliminating introducing aspects that identically alter all the instruments? For example; we can significantly compress a single instrument without undesirable side effects yet even minor compression on the whole mix is readily audible. Think FM radio versus the CD or when the PA vendor puts a left/limiter on the PA. Looking at the dispersion of instrument, cymbals have a 360 degree radiation pattern whereas a kick drum has more of a figure 8 radiation pattern.  Guitar rigs can be figure 8 or somewhat cardioid pointed forward. Each of these instruments have vastly differing and unrelated frequency responses that can be readily altered  by choosing a differing cymbal manufacturer, switching to a felt kick beater changing the guitar cab type, yet none of those changes alter their "liveness".

Frequency response can be altered before or after the sound reproduction process so it is important for things sounding desirable but has little to do with things sound real or live.

So based on this I am thinking I can add the concept:

"Nowhere in nature do multiple unrelated sound sources offer identical dispersion patterns, yet in pro audio we do it all the time"

to the two other fundamental concepts I have been distilling, which are:

"Nowhere in nature do multiple unrelated sounds radiate from a single point in space, yet in audio reproduction we do it all the time."


"Nowhere in nature does the exact same sound radiate from multiple points in space but in audio reproduction we do it all the time."

With the underlying idea being that the more we stray from what occurs naturally, the more illusive realism will be.

Ok and on another note, I have been putting together a small playback studio with some spare and older bits of gear from Rat.  I have a lot of old multitrack DA88 tapes from various past tours and am looking to do some multi-channel mix downs for use in sound seminars and demos and such. The tapes have all been backed up to ProTools but rather than buy or tie up one of Rat's Pro Tools rigs and since we have 5 DA98/88/38 series machines laying around, I figured why not bring them home and use them.

What I quickly found is that they were very hungry and had a overwhelming urge to eat tapes. I cleaned the heads and ran the error rate option and all 5 machines were all over the place so I opened them up to see what I could find. What was happening was the tape tension seemed to be low and excess loose tape was building up in front of the pinch roller. For some reason they lacked tape tension.

After a bit poking around and found some good info here that helped a bit and got me in the right area

And thought I would share what I found was the exact same issue with all 5 machines. The tape tension arm shown below was no longer moving freely

When you press play, the arm should wing to be on the tape as shown here. but instead was barely moving

So, with a very small tweezers and exacto knife, I removed the two plastic split washers

Which are very small, do not drop them in the machine!

Removed the tension spring

Removed the tension arm by gently rotating back and forth with a needle nose pliers. I snapped a wood q-tip in half and soaked it in some WD40 and used it to clean out the pivot hole. Then used alcohol on a q-tip to clean the pivot shaft. Then put a drop of some multi purpose ultra lube on the pivot shaft. Dont put any lube on the tension shaft that contact the tape.

 And then reassembled it all back together and everything worked perfectly and all the error rates dropped to zero. 

And since there is more to life than pure audio. a few adventure pics to lighten the load. There was a most wonderful week of amazing waves that came to visit our southern California shores

but not without consequences for the unprepared and when the waves get big enough to break things

It can become a spectator sport as well

But when it looks so good I just can not resist


Sunday, August 24, 2014

Building New Toys

So Peppers tour has ended and  walking into the production office after the last show at Isle of Wight I could not resist taking a photo. Three years of on and off travels and another chapter comes to a bittersweet end. I will miss seeing all my friends on world adventures till next time and oh the thought of being home for a while is very very wonderful.

It is a shame those set lists did not go to fans but some things ya just got to let go. It has been a while since I have blogged.  Partially due to recovery from my bike crash, partially due to focusing on dedicating time to finishing Peppers tour, partially from immersing in the business side of Rat Sound and also because I have been working on some new speaker designs and concepts.

As far as bike crash recovery, I am mostly back up to speed with only the odd lump from my broken collar bone, a slight bit of shoulder rotator motion loss and most oddly, I seem to have an altered sense of smell. Some things I just can not smell at all and other things I am quite sensitive to. My sense of taste seems fine though. Ha, maybe light losing sight improves hearing, maybe losing smell will help hearing too.  Lucky me.

Here is a blog post I started a while back and never posted:

Comb filtering is a description of the cancellations created when a signal is re-summed with a time shifted version of itself.  The 're-summing' can be electronic or acoustic.  

If you wish to eliminate comb filtering you need to either reduce the number of source such that only one source can be heard at the listening positions. not allow time shifted versions of the same signal to sum electronically or alter the signals so they are sufficiently dissimilar.

In real world reinforcement applications, comb filtering typically is not solved, it is mitigated. Where it gets interesting is that the humanly configuration of our bodies and location of our ears is such that undesirable effects of comb filtering occurring in the horizontal domain is actually minimized when the sound sources are sufficiently far apart from each other and we are located somewhere between those sources which is why we prefer stereo instead of mono home stereos even when the sound radiated from both speakers is identical or similar.

I personally strive to minimize sending the exact same signal to multiple horizontally spaced speaker arrays. I want the guitar mic sent to the left PA stack to be a different signal than the guitar signal sent to the right.  I want them both to sound good, but not to be identical.  Same with bass, and as many other instruments as possible. This reduces comb filtering and minimizes creating power alley.

And for some newer stuff, last week I did a Dave Rat Seminar for Disney sound technicians. Super cool and I felt quite proud that I have shoveled enough knowledge into my sandbox that I am asked to interact with such a highly respected organization.

Doing the Dave Rat Seminars has helped me clarify some basic fundamental concepts. One of those concepts is:

"One of the driving reasons that humans gather in groups is to experience lasting memories."

We attend rock shows, sporting events, houses of worship, theme parks or political rally's in order to create a memory for ourselves and for others.Those memories are created by connecting the people that have something to say with the people whom desire to listen, watch or interact. The more of our senses immersed in the experience, the more powerful the memory. 

As sound reinforcement professionals, our specialty is the audio spectrum and to work with the visual, and other specialists to create the most powerful connections we can. If we keep our grand purpose in focus we greatly increase the probability of a desirable outcome. 

Sooo, on another note

As far as projects, I am currently working on designing what I believe to be the best sounding, loudest, clearest and most versatile stage monitor ever created. With the assistance of (in no particular order) Mario DiCola, Eighteen Sound, Jefferey Cox, Powersoft, EAW and the key people at Rat Sound, we are creating a stage monitor so clear and powerful, using only the most premium components, that no other stage monitor even comes close to its capabilities.

oooh, powersoft visit

Taking everything learned from building the Rat Sound dual 15"/10"/2" L-Wedge and everything learned from designing the EAW MicroWedge series of monitors and creating a stage monitor that is about the same size as the leading high power wedges and exceeds the capabilities of the L-Wedge and MicroWedge combined. I would very much like to share more as we have a working prototype that literally makes the top wedges currently available sound like they are broken when put side by side. Soon Rat will have 4 pairs of wedges with power that we will put out with some key clients and I will give more details.

Here is a photo of Mario, this is not the wedge but rather an early stage of component testing. 

Working with Mario and Eighteen sound has given us access to fine tuning every aspect of the custom loudspeaker design from voice coil material, voice coil length, cone type, weight, magnet type, strength and material and more. I wanted components for this wedge that have never before existed. Here is a laser testing parameters of one of the custom components.

My long standing relationship with EAW is the foundation for the cabinet construction, testing, specs and processor settings. The developing relationship with Powersoft will optimize the amplification and aspects while us at Rat have developed the actual design look, features and capabilities.

Can't have a new design without napkin drawings

Another project I am excited about is I am building a super compact portable sound system that is 8 inputs, 8 processing channels, 8 outputs at 50 watts per channel and the whole ting fits in a suitcase. I intend on using this as a demo system for future seminars to show the differences between mono, stereo and multi-source audio reproduction as well as use it to test some concepts I hope to apply on a larger scale for future arena tours.

As you can see, the small cabinets have mini pole mounts so you can build erector set type structures.

And now for the serious stuff:

Proof that beer and sound go together

That Leonardo guy was a sharp cookie

Oh, Another project was building a head mounted iPhone steady cam for Josh. I love power projects where you just make something useful from stuff laying around the garage

And finally, a video from Thailand at a little zoo on the beach of little otter with something to say.

Saturday, February 1, 2014

Big Owie

I am blogery slacker, just mining for the time to set aside and brain data dump some things to share. I did have a bit of a hutch in my get-a-long as well. I love surfing and snowboarding but decided to take divergence into a 40 mile bike ride.

Which seemed like a reasonable enough idea. Off to the trails in Ojai staring in Ventura and oh maybe 15 miles in or so, KABLAAAM. Another bike rider flying down the trail on a brake-less fixie bike broadsided me and sent me flying. Owie to the bicycle

Owie to my shoulder

And super owie to my head left me 8 days in intensive care and a multi-month recovery

 Anyway, I am mostly healed up and getting back to my scatterbrained and quirky self enough to do some surfing

Hang out with My dog Bones

And especially spending time with my awesome gal and amazing daughters.  Oh yeah, and Gene too! 

Oh, and ya know something really cool about doing some hospital time and getting all screwed up? All the friends and family that come to visit. I can't begin to describe how magic it was to be laid up in a hazy world and feel so loved. Truly amazing and thank you so so much.

On another note, I have designed some BSS 960 fader link knobs 

and printed them out on my 3D printer 

that allow us to EQ left and right at the same time.

ILet me know if you want a set and will print some up. Am thinking 30 in a light gray color plus 2 printed in glow in the dark plastic so you can have a few that mark 250hz and 2.5K

Oh, so today I am in Brooklyn for a Peppers gig at Barclays Center today where I have the most curved line array hang I have ever mixed on.  Hmmmm, not sure I am digging it but we will see.

and then tomorrow Peppers play the Superbowl Halftime show.

And how about some audio nerdery I was working on before I got bike crashed.

Some thoughts on Equal-Loudness Contours (Fletcher-Munson curves)

Compensating for Fletcher-Munson curve effect was quite popular in home Hi-Fi for many years with the "loudness" button that boosted some lows and highs on nearly every home stereo receiver for decades. Interestingly it has all but vanished on current home hi-fi equipment.  Also of note is it has never become popular in live audio reinforcements systems. My personal experience is that it is something where studies and measurements show that it exists yet when I push the loudness button on my home stereo receiver, it makes the music sound unnatural and overly bass and treble heavy. Plus and more importantly the adding of a perceptual based compensation network brings with it some doubt.  Was the recording made with a predictive intent for this button to be pressed to induce a desired alteration? When the band plays soft or loud in the rehearsal space, where is Fletcher and Munson compensating for my hearing? Am I hearing it incorrectly so it needs to be fixed?

My take on it is, yes I believe that it does exist, at low volumes sub lows and HF are less perceptually prominent.  Yes, they can measure and approximate a compensation that electronically corrects for volume dependent frequency perceptions. And I believe that the utilizing the concept of attempting to compensate may be short sighted.

Perhaps just perhaps we as humans already naturally expect to hear less sub-lows and high frequencies at lower volumes, we expect naturally to hear a differing balance at higher volume levels. Perhaps an  automated volume dependent compensation circuit is an unnatural event and though it may correct for our hearing, perhaps these loudness buttons have faded from favor, vanished from usage because though technically an argument can be made that it is a valid correction. For us live engineers there are additional challenges in as we deal with a dynamic range that is so great and the distance variations to listeners so vast and then add in ear plug usage, differentials in age related hearing loss/sensitivity of the listeners and so on.

That is not to say that having control over volume dependent tonality is not useful and valuable. And conversely, a major issue with many sound systems is that the tonality changes with volume in undesirable ways. Most typically when turning up a sound system resulting in having everything go into limit except the 2" drivers which creates a reverse Fletcher-Munson curve scenario, that is difficult to compensate for.

I have had some success with applying Fletcher-Munson curve type compensation in live audio in the form of implementing subs and tweeters on auxillary sends with manual control of the volume that the subs and tweeter limiters.  Soft songs have full subs/tweets, louder sound push subs/tweets into limit offering a Hi-Fi sound at lower volumes and a 'rock' sound at higher volumes.  I do find this useful as a manual control and this had a side effect of increased intelligibility of  the artist speaking between songs. That said, it has been years since I felt compelled to implement that control and on modern high end systems, it just does not seem necessary to add that complexity, at least for the artists I have been mixing.

One aspect I have been focusing on more recently is "Should we try and force the sound systems to maintain the same HF EQ at long distance listening positions or is it a do we as humans prefer to hear some HF roll off when the source is far away?"  As systems improve, we are gaining the ability to throw HF father and farther yet in my opinion, a bit duller less edgy sound when listening from long distances can often be a more enjoyable experience and it sounds more natural as long as sufficient intelligibility and volume is maintained.

Ok, no promises but will try and blog and share more soon.