World's largest photo album- PA System

Last week we supplied a PA System for the Worlds largest photo album.  The record was atempted by Photobox at the Old Truman Brewery in London's Brick Lane.

Worlds largest photo album

Sound coverage was needed for background music, and various anouncments for up to 300 people.  We supplied and installed a pair of Yamaha MSR400 powered speakers, together with a Soundraft E6 mixer and a Sennheiser EW100 series hand held radio microphone.
The photo's on display were superb, and many of them were taken by amature photographers around the UK. The subject was World travel.

The Yamaha speakers were partly conceled behind the pillars

What is loud? Why do I need to know about dB SPL?

Perception of loudness is a complicated subject. Every person will perceive loudness differently, as everyone’s ears are different. In fact, everyone’s ears have a slightly different frequency response.

This is why, in sound engineering circles, there is a need to quantify sound pressure levels to define what is loud, and what is quiet. Or perhaps that should be; what is too loud and what is too quiet. The unit of measurement is the dB SPL (decibel). There are also more accurate measurements of loudness called phons, and subjective loudness, called sones, but these are rarely used and are outside the scope of this course!

For convenience we normally measure dB SPL from the mix position, but it can be useful to measure from other areas such as the front row and the stage.

For those new to dB SPL here is an idea of how different sounds compare in level:-

Recording studio	30dB SPL
Conversational speech	60dB SPL
Noisy office	80dB SPL
Church concert (contempory worship)	95dB SPL
Loud rock concert, front row	120dB SPL
Threshold of pain, average young person	130dB SPL
Concord take-off from runway side	140dB SPL
.357 Magnum handgun, (peak impulse)	165dB SPL
Under a Saturn 5 Rocket on take-off!	194dB SPL

This article was taken from my web site, you can read more about PA Hire and dB SPL here.

Analog vs Digital mixing desks

Firstly, I should say that everything I say here is purely my own opinion ;-) This is a debate that's been running for some time in the live sound and PA Hire world... the relative benefits of analog and digital mixing consoles.
Analog offers familiarity and ease of use, having been around since the dawn of sound re-enforcement, it's what most engineers will have learned their trade on.  Digital offers a brave new world of layers, built in effects and dynamics, and work flows that are completely different to the traditional analog cousins.

Digital has come on in leaps and bounds in recent years.  Interfaces have improved, sample rates improved along with sound quality.  Prices have come down a bit.  Progress in the analog world has been slower, with few manufacturers putting in much R&D into this area any more.

It appears to me that if you've got decent money to spend on a desk (like, over £7000), then digital appears to be the favourite option.  Analog desks in this price bracket tend to be vast and incredibly heavy devices, sometimes needing up to six people to lift them onto a stand. They need a big rack of outboard with them to compete in any sense with a digital board.  Digital desks are for the most part much lighter and easier to handle. They have all the outboard built in, so that's another rack that can be left behind.  Most people agree that the sound of digital desks holds up pretty well too.

The difficult comes when you're spending less money, as the choice of digital desks tends to dry up a bit under £7,000 or $10,000.  You are left with a few 16 or 12 channel offerings like the smaller Yamaha LS9-16 or the O1V-96.  There's a few left field offerings like the Presonus Studiolive as well, but their unusual interface could be perceived as a little bit rider-unfriendly.  If you need 32 channels, as many live sound engineers will, you're a bit stuck.

In the analog realm however there are a good few well respected desks in this price bracket, such as the Allen & Health ML and GL series, and the Soundcraft GB and MH series.  Some of their larger offerings are still pretty heavy, and you do have to wonder how their values will hold up with digital boards getting cheaper.

So perhaps the best decition is to wait untill the prices of digital mixing desks has dropped, and hire a mixing desk should you need one in the meantime!

Me operating a Yamaha M7CL digital desk

Conference PA systems

Yesterday I supplied a small PA system to a conference suite at the MK Dons stadium Hilton in Milton Keynes.  The client needed to project his voice to the back of a large room full of people, without straining his voice.  We used a headset radio mic (Sennheiser EW300 series), connected to a Soundcraft E6 mixer.  Speakers were Yamaha MSR100 powered speakers.
The Yamaha MSR100s are very compact size but produce a remarkable sound quality and volume for a small box.  We had custom covers made for ours as they don't come with a cover.
I was impressed by the size of the stadium and the facilities on offer!

Yamaha MSR100 speakers, great for small conference events

The MK Dons Stadium in Milton Keynes

Subs up for more bass

Getting a good kick drum sound on a gig many engineers would agree, is a factor of how good your subs are.  A pair of 15in drivers is not really going to cut it unless it's a really small gig.  Horn loaded 15s or band pass 15s maybe!  A key fact to consider is this:- to double the perceived volume you'll need to need to more than double the power.  In fact, you'll need around 10 times the power to double the volume (a 10dB increase).  So that's like going from your 1KW system to a 10KW system.
But there is another way... doubling the number of subs will generally increase  your bass output by 6dB.  So let's say you take your 1KW rig, and instead of 1 15 inch sub each side, you put 4 15inch subs each side.  You will have more than doubled the bass output.  For the same power!  I'm assuming your amp will cope here, by the way... It may be asking a lot to go from an 8ohm load per side to a 2ohm load per side with 4 cabs a side connected.  I've blown amps up using them like this in the past.
But what about the mid range and high end?  Yes, you can gain around 3bB each time you double the number of cabs on the high end.  But you'll need to watch out for comb filtering, and lobing.  For small(ish) events, sometimes just pumping up the bass with more cabs can be enough, if you've got good quality tops.

If you are interested in hiring sub-woofers, have a look at my website here: www.soundtruth.co.uk

Tuning for your PA System or Sound System

When setting up a PA system it can be a real challenge to 'tune' your set-up to sound right in any given room.  This particularity applies when you're setting up from scratch with new amps, crossovers, speakers that you've not used previously.  Any given speaker will have a different frequency response, different optimal crossover points, and so on.  Different amps will exhibit different amounts of gain.  And of course, different rooms will have modes, surfaces and reflections to consider.
In these cases it's very hard just to use your ears to set up the system.  After a few minutes of listening, ears can 'adjust' to a particular sound, and your system can end up sounding wrong.  If you have no choice, it's best to take a short break and come and listen again.  But there are other tools out there to help.  One of which is the real time analyser, or RTA.
In basic terms, this is a device, or software application, that splits the sound into different wavelengths, and measures their relative intensity.
The application I tend to use is call True RTA.  It can be installed on a laptop for portable use, but is best used with a good quality condenser or measurement microphone, rather than the built in laptop mic.

True RTA real time analyser

Real time analysers can be used in a live setting for fine tuning a system response.  Playing pink noise through the system provides one method of analysis.  Some programs like True RTA also provide a sweep tone, which can give further insight into the frequency response of the system, and also to some extend the room modes.

True RTA in use on an outdoor festival

If you are interested in fine tuning your PA System, whether in the UK, Africa, or US, please don't hesitate to get in touch with me.  I offer Sound System tuning to churches, schools, colleges, and other music venues.

KT Tunstall rocks at Thelastfestival 2010

Last week we did the sound for KT Tunstall at Thelastfestival, which was put on by CBS for last.fm.  On front of house we used 4 stacks of HK Audio DEACON, monitoring was done with HK Audio Contour CT112 wedges in bi-amp mode, driven by HK digital field controller.
KT's on stage set-up included a bank of effects pedals, including a Akai E2 Headrush loop pedal, and a Korg Kaoss pad.  Four DI boxes where used for the setup, these where Radial Engineering boxes.

KT Tunstall on stage

Due to the bar being positioned at the back of the venue (London's Village Underground), the mixing desk was positioned at the side, but happily still offered a good view of the stage.  The mixer in question was a Soundcraft GB4 32 channel.  Various outboard was used, including a Mackie Quad comp for lead vocals and guitars.
If you have an event coming up, contact me for PA Hire, Lighting hire or other requirements.