Mark Payne's Production Blog

SFL Real World testing of Ether Sound capability on Yamaha M7CL-ES

2010-11-30T03:53:00.000-08:00

I hope you find this information helpfull.
We have some more ideas and developments around the use of ES in live applications comming soon.
I should have some very exciting stuff to show you in January!
mark at sflgroup.co.uk

Bench Testing the Line6 2.4 GHz XD-V70 Radio Mic System

2010-11-29T08:25:00.000-08:00

Introduction

At SFL we are currently reviewing the radio systems at our disposal in the light of post 2012 digital switchover and the clearing of TV channel 69 (and other) bands.

Its is likely that we will want to replace with GB specific product from the likes of Shure and Sennheiser who both at the time of writing have convincing CH 38 / 39 /40 reaching equipment in the guise of UHF-R (Shure) and G3/300/500 (Sennheiser).

More is More

Any readers that have attempted good intermodulation free production planning with more than say 8 channels of radio and some IEM (In Ear Monitoring) thrown in for good measure will know that we exponentially require more UHF bandwidth as the number of systems increase.

So the idea that we can have "another world" up in the 2.4Ghz area to expand the radio system playground.... this can only be a good thing.

Line 6 make a nice looking 24 bit digital system working in the 2.4GHz area ( http://uk.line6.com/xd-v/ ). My job over the last day or so has been to evaluate it for our needs for general use and hire stock. The apparent advantages of such a system would be as follows:

>115dB dynamic range with no companding (great for general accuracy and measurement applications)
Great signal to noise performance
License free operation
Immune to issues of DSO leading up to 2012 and beyond
12 channel compatibility
Integrated antenna distribution

Gain Brain

http://line6.com/media/pdf/Line%206%20Wireless%20microphones%20Whitepaper%20UK.pdf

Testing for Headroom

The above white paper from line6 explains that with such huge dynamic range in play (>115dB) there is no need for gain trimming at the transmitter as we are used to doing with traditional systems to optimise signal to noise performance. Indeed the V70 hand held unit and V70L belt pack transmitter indeed have no gain trims either in the form of electronic pots of menu options.

The belt pack system on V70L is advertised as having a 6.5V Peak to Peak maximum sensitivity at 3% THD.

I measure 6V peak to be just before visible clipping on a scope at 1KHz. That compares well to the spec. I cannot measure THD, I just watch the scope!

Below Clipping

Opps.. Over!

You may be interested to know that the first LED on the audio meter (on the RX) comes on at -70dB below full scale (defined by me as 6V P2P). The last "maximum top of the scale LED" comes on at -30dB below full scale. Hence in now way is the top LED a peak LED.. it is 30dB below peak.

You may also like to know that a DPA mic on a suitable standard TA4 connector ("Shure Type") works out of the bag. Also a Beta 98 plugged in on a TA3 to TA4 converter lead works out of the bag.

I conclude that this thing has ample headroom. At 24bit sampling we should have >115dB of dynamic range. We could argue that there is at least 45dB of dynamic range under the first LED, 40dB covered by the set of audio LEDs (bottom to top) and 30dB above the top LED to clip.

If I take a DPA 4066 with max SPL of 144dB before clipping with 6mv/Pa sensitivity.
We know 1Pa=94dB SPL

Raise 94dB to peak SPL (144dB) is an increase of 50dB.

We need 50dB (this is based on 20Log, its a pressure... do you agree?) of headroom above 6mV (I think this is RMS). This is a hence multiply factor of Antilog (50/20) = 316

6mV * 316 = 1.90V approx (I will assume RMS)
1.90/0.707 converts to peak = 2.6
Double it for Peak to Peak = 5.2V

Hey presto the V70L has 6V Peak to peak in the bag. You can grab a DPA 4066... yell down it like a madman and have headroom. There is no need to gain trim.

How Flat is Flat?

Here I use TuningCapture to plot the frequency response and impulse response from a log sine chirp.

In this test I compare the signal through the V70L belt back and compare the performance to a piece of wire doing the same job!

The control trace is in yellow with the performance through the V70L in red. Notice the V70 has usable bandwidth from 20Hz to 16KHz within 2dB. You can also see that the latency through the system is fixed at 4ms. In spatial terms that's just over 1M of latency. Not worth a worry in my world.... just good to know what it is.

To be honest right now I cannot fault it. Next I need to test to see how nicely the system plays with computer wifi working alongside it but for now this system gets a big "PASS" from me.

Regards

Mark Payne

2009-02-06T14:50:00.000-08:00

A couple of my pics from a Yamaha factory visit in 2008.

Top people. Top company. Top products.

Above: PM5D Assembly, lots of love and care. Build me a good one!

Above: M7CLs Ready to Go.

Above: This is a manufacturing cell team working on building PM5D at Yamaha.

I cannot tell you just how much quite attention to detail happens when these guys build stuff.

This team are responsible for every stage of the build process from picking parts to final packing.

A privilage to see it.

Mark

Three Phase Mains: Current in the Neutral?

2007-06-11T15:30:00.000-07:00

This is a favorite interview question of mine:

Given a three phase suppy at 63Amps per phase, standard Star 5 wire configuration with all three phases fully loaded. How much current flows in the neutral?

A. 63 Amps

B. 189 Amps

C. Zero Amps

.... well there are three phases L1 L2 L3 and they all share the same neutral wire.... hmmmm

And the answer is ....

C. Zero amps

Assuming the phases are balanced in terms of current load and the power factor per phase is the same. The relative phase offsets of 120 degrees per phase means that if you sum the voltages at any point in time over the three phases you end up with a total voltage of zero volts, so zero current flows.

This is what it looks like:

Another question follows: If the loading is hopelessly unbalanced... what is the worst case current in the neutral?

Here is a clue... how much bigger is the neutral wire compared to the three live wires?????

Care to comment?? ;-)

Mark SFL 1, West Ham United 0

2007-06-09T15:12:00.000-07:00

Some technical audio notes form my sound design for Global Day of Prayer at West Ham United football stadium London UK. 27th May 2007

Sound, Lighting, LED and Video production by SFL.

Ave it!

I Win!

I win, no more than a 5 dbA drop from front row in the ground blocks to the back top seat at the back of the west stand. It was actually better than I calculated. The reverberant field lifted the levels up in the gods but the intelligibility was still spot on.

Why Fly?

There were no people to be on the pitch so what is the point of flying when you can achieve front row level control by taking the system back 20M?

Design Objectives

As always my design objective (for contemporary stuff) was to come up with a 100dBA (1min LEQ) capability with 10dB of amplifier headroom and achieve no more than a 6dB level drop from front to back.

Opps Lots of boxes

I used over 100 boxes of d&b Q series (Q1 and Qsub) with some additional B2 in infra mode. All the sub systems were in CSA (cardioid sub array). SFL's Mark Young mixed the band and Graham Preston mixed the orchestra, they both nearly wet themselves over the system/stage separation provided. They were able to mix the orchestra up at ANY level they wanted.

Cardioid Sub Array

The CSA took the sub energy away from the stage and tightened up the bass in general.

No Time

We had to rig the systems through the night, in the wet (nice). Qcalc did a great job as normal but the distances were large and small angle errors were going to have a big effect on array performance. I lasered the boxes into the stands which really helped to get it all right from the off. The production schedule gave me only 30 mins to align the whole system with real noise so I had to have the mechanics of the arrays right from the off. No time to physically tweak.

Things That were Magic

Some things that really worked on this gig:

Radio (Mike Wilson) did a great job for me as system No2. Everything we rigged worked first time. Brilliant.

RopeC... you cannot do a gig like this with distributed amps without remote control. RopeC is a piece of genius. Gotta love CanBus

AES/EBU .. I went digital to all the amps from the PM5Ds at FOH. It's great but what a lot of lesons I have learnt. Beware of what happens over 100M. In preparation I found all sorts of problems that I might write up later.

My own private wirless network allowed VNC control of my FOH PC. This enabled me to play sources, control the PM5D's and tweak the system with RopeC from the stands on my (damp) laptop.

Trust no-one

"Trust no-one" part 1.. never build anything on site that you have not previously tested. I was worried about these ground stacks. The last two boxes are a little tricky to get on. A bit of a risk assesment was going on here.

"Trust no-one" part 2.. hmmm thats a lot of digital cable. better check it... opps it does not work very well!. Then I learnt a lot about impedance matching and conversion. Also the difference between reclocking DAs and simple (no latency) edge conditioning buffers in the D12 amps... The fix on the cheap is if you want over 100M you convert to from 110Ohm to 75Ohm and run it on video coax before converting back again. Glad I learnt these limitations in the wearhouse, got my trusty HP osilloscope out again!

"Trust no-one" part 3. Our consoles for both FOH and monitors were preloomed and preprogrammed at SFL. The whole 96 channel split system was configured, patch checked and line checked from stage box to three ends (FOH, Mons and TV).

Some other pics:

People comming in

Craig's LED Screens

When it rains, stuff gets wet.

SFL People:

Craig Lawrence, Overall SFL Technical Production Manager and LED
Mark Payne, Sound Systems Design
Mike Wilson, FOH Speaker Systems
Mark Young and Graham Prestion, FOH Sound
Colin Hounsome, Monitors
Tom Jeffery, Lucy Kay, Dan Appleby, Stage setup and management.
Adam Evans, Choir Monitors
Monkey Tim Pitman, double shift crew madness
James Cremer Evans, Rigging
Ollie Jeffery, Lights
Mike Simpson, Camera Director
Clair Stroud, Graphics Op
Nick Pemberton, Sound wanderer and water management!
Audrey Payne, Crew Nanny