Sound Systems

A line array system is made up of multiple speakers of different sizes and frequency ranges all connected together but at different angles forming an overall curve. Because of the different angles of the speakers, delays needs to be put in place so that there are no phasing problems between the speakers. This allows a tighter and very clean sound and since the sound is more focused it means that less sound energy is lost through the crowd so they are perfect for gigs in large locations.

A distributed system is when speakers are placed at each side of the stage at a concert. These speakers can either be speakers made up of tweeters and subs or full range speakers. These speakers are not as focused as the line array system as the speakers are omnidirectional and this means that the sound energy is more susceptible to being lost in a crowd so they are more suitable for smaller concerts. If they are used at larger concerts they will need to be backed up with fill speakers that have delays in place so people further back can hear as well as people at the front and also that the sound is in phase with the front speakers.

The fill speakers are used to fight against what is called the inverse square law. These means that every time the sound energy gets further away from the source it decreases in decibels in other words double the space each time the sound energy drops by 6db.

Drive Rack

The drive rack is a component that has all the system processors that connect between the mixing desks output and the power amp inputs. Since everything passes through them it is important to have a decent quality rack instead of a lower range one. By system processors I mean dynamics processors, EQs and time alignment delays.

Dynamics processors are basically you compressors and limiters. A compressor are used to control the overall level of a signal, stopping it from getting to loud or too quiet without you constantly monitoring it yourself and keeps the sound under control. Too much compression kills the dynamics in a song. Limiters are a much more extreme form of compression with rations of 10:1 up to infinity:1 whereas compressors only go from 1:1 to 10:1.

Equalizers are an essential item in any rack or studio. They allow the user to cut and boost frequencies to get the particular sound that they want. In the live scenario the drive rack EQ is used to treat a room. Each room in a live environment can have its own affect on sounds and how they react based on how they are made up. The engineer would put mics in the room then push the gain up as far as it could go on them till feedback starts happening. The gain would then be pulled back till just before the feedback happens and then use a 31-band equalizer to adjust the frequencies to prevent standing waves.

Time alignment delays are delays that keep all frequency related components in phase when they reach the audience. The delay times are normally extremely small for example being a fraction of a millisecond. When the proper time alignments are in effect, the result is a full and powerful sound that spreads throughout the whole room wherever the gig is at. 

Bound for boston 13th december Stage Management

This gig is an example of when I was tasked with a different job than doing sound or setting up.  I was the stage manager for the gig and my job was the basically make sure that each band was ready to get up on stage straight after the band previous to them so to make sure the gig runs smoothly and on time. 

The band list and times were:

1: Mandela Skies (10.00-10.30)

2: Not Our Day (10.30-11.00)

3: Room 34 (11.00-11.30)

4: Sizlack (11.30-11.45)

5: Circle the Sky (11.45-12.00)

6: We Are Band (12.00-12.15)

7: Twisted Pepper (12.15-12.30)

8: No Hot Ashes (12.30-12.45)

9: Swing Bins (12.45-1.00) 

I didn't know many members of the bands but i just asked the people i did know i asked who the others were and that sorted out my problem. I got each band together, made sure they were all tuned up and ready to go then told then to stand next to the stage whenever whatever previous band was on their last song. 

Student BBQ 2nd June.

Me and Jason Cameron were tasked with setting up the sound for the end of year student BBQ at the amphitheatre beside the canteen at the main Strand Road NWRC building. The day before the gig we meet up with the band and asked what they needed for the gig then started making out our stage plan for it. From asking people in class who did gigs in the amphitheatre before what they needed to mic up much considering the size of the place and found they just let everything go through amps and just use vocal mics really. 

The band was Medium Rare and they said they needed three vocal mics, 2 DIs for their semi-acoustics and a monitor for the vocals to hear each other for doing three part harmonies. We decided we were going to mic up only the kick on the drum kit but when we got to the theatre and started setting up we didn't feel that we needed it. One of the guitarists had 2 separate semi acoustics for himself that he was going to change between songs and we had a spare DI with us so we set it up with his alternate guitar already plugged in and set up so he could easily change between guitars and get right into playing. We muted which ever guitar he wasn't using during the songs.

The channel list was as follows:

1- Guitar 1 DI

2- Guitar 2 DI

3- Vocal left  PG48

4- Vocal centre  PG48

5- Vocal right   PG48

6- Alternate guitar DI

The soundcheck went well and here we sorted out what everyone wanted in the monitor then we went ahead with the gig. I sat out in the crowd and signalled to Jason which things needed turned up or down. The gig went really well and when the band was finished we played a playlist out of a iPod while we put around all the mics and instruments used by the band.

Strabane Campus

For this gig we had to set up in the foyer of the Strabane campus. Since it was a very small room we didn't need to mic up anything apart from the the 4 vocal mics that were going to be used and we also used two DIs, one for the yamaha keyboard and one for the nord.
The guitars went through a cube 60 each and the bass went through a behringer amp.

The vocal microphones were plugged into the first 4 channels then the DIs into 5 and 6. We also plugged a iPod into the desk for music in between amps. 

The gig went very smoothly and was quick to set up since nothing needed miced up. I had to adjust the amps during playing and the space was quite confined but apart from that the gig went really well.

STAGE PLAN

CHANNEL LIST

1- Vocal left

2- Vocal centre left

3- Vocal centre right

4- Vocal right

5- Nord DI

6- Yamaha DI

22/02/11 Limavady Campus Gig

I set up at this gig with Jason Cameron and Niall O Doherty, who were the runners for the stage while I worked on the mixer and set up my iPod for music. The bands that were playing were Twisted Pepper and Medium Rare Twisted Pepper were the first band up consisted of a drummer, bassist, guitarist/keyboardist/backing vocalist,and the main vocalist. Medium Rare had a drummer, 2 guitarists using semi acoustics with one doing backing vocals, bassist/backing vocals, and 2 vocalists.
The hall itself wasn't the biggest and with the drums and amps set up we decided not to mic up the whole kit, just the kick, or the guitar and bass amps. This was because they came through clear and loud enough on their own due to the acoustics of the hall. We set up 4 vocal mics, 2 of which were being moved to the side for Twisted Pepper since they only used 2, then we would bring the other two back on the stage for when Medium Rare played. Two DIs were used, both for the semi acoustics in Medium Rare with one being used for keyboards in Twisted Peppers set. All leads were ran on the outside of the stage and were taped down to avoid an tripping hazards.

There was a problem with the monitors when were setting up for the gig. The monitors we were using didn't have the right connection for the Limavady techs desk and was causing a very noisy signal when turned up loud enough to be useful. So we decided not to use them and have the performers rely on the front of house.

Both bands played really well however Medium Rare had some very slight issues with timing, most likely due to the fact they had no monitor but they did carry it off well.

Channel Listing
1- Left Vocal
2- Centre Left Vocal
3- Centre Right Vocal
4- Right Vocal
5- Keyboard(Twisted Pepper)/Semi Acoustic(Medium Rare)
6- Semi Acoustic 2
7- Kick
Bass came out the amp for both bands and electric guitar came through the amp in Twisted Pepper also.

STAGE PLANS

Twisted Pepper layout

Medium Rare layout

Standing Waves

Today in class we experimented in room 11 was the concept of standing waves. A standing wave is a sound wave that reflects off a surface back in the same path as it came from and continues this pattern back and forth over and over again. This can cause the certain frequencies to be emphasized or can cause them to be cancelled if the wave ever went out of phase. There are 3 different types of standing waves: Axial, tangential and oblique.
Axial standing waves are the reflections between 2 surfaces, tangential are the reflections between four surfaces and oblique are reflections between 6 surfaces.

In class today I was put into a group with Eoin and William and we were tasked with finding out the length of point B of room 11 as shown below.

We found the length of B to be 7.265m. To find out which frequencies standing waves would occur at we used the equation Hz= Speed of Sound/2 lambda (2 times the length of the room)

So the equation became Frequency= 344/14.53 which equaled 23.67 Hz as the fundamental frequency. Then we multiplied this fundamental frequency by different whole numbers to find out what overtones more standing waves would occur at and found this:

1- 23.67Hz
2- 47.35Hz
3- 71.02Hz
4- 94. 70Hz
5- 118.37Hz
6- 142.37Hz
7- 165.72Hz
8- 189.40Hz
9- 213.07Hz
10- 236. 75Hz

The frequencies we found were then generated on the computer and played through the speakers. We could just about hear the lower frequencies as they were like a low rumbling and I could feel some in my lower chest area. When the frequencies were played out we noticed that the railings and windows in the room started to strongly resonate with some of the frequencies especially when they were played louder. Overall you could definitely tell that these frequencies were being influenced by the room as moving the speakers positions had an affect on the reflections specifically they’re amplitude felt affected when this was done.

Standing waves can cause problems in the live environment as the emphasis and cancellation of frequencies brought from the standing waves can produce a very muddy sounding mix to the audience and negatively effect their listening experience.
In a studio situation these can be dealt with quite effectively through the use of diffusers, which try to reduce the amount of parallel surfaces in the room, and sound absorbers, which absorb frequencies for example bass traps soak up a considerable about of bass frequencies as best as possible. However live venues and live sound engineer generally don’t enjoy this type of control of the environment so to deal with standing waves the engineer will simply have to listen out for these waves by sweeping through the frequencies on the EQ and reducing or cutting these frequencies.