LINE ARRAYS - THE REAL AUDIO ASSIGNMENT

LINE ARRAY - ITS NOT AS COMPLICATED AS I THOUGHT

                    The decision was made even before i joined the company to go for a Line array. Thanks to all the sales people of different companies. I did not have to convince people for a bigger budget. It was already there in their mind.

                    I have never worked with line arrays before. Though i have studied about them theoretically, i was a little scared about it especially for the rigging part. A little bit of details on the Line arrays.

DIFFERENT SOURCES OF ACOUSTIC OUTPUT: 

1. Point Source: A point source is a single localized point of acoustic output. It radiates sound in a spherical Pattern. The Sound pressure Level (SPL) decreases 6db for every doubling of distance. For instance at point x if the SPL is 100 dbspl then at 2x the SPL will be 94 dbspl. This is mainly due to the surface area of the sphere being directly proportional to the square of the distance. As shown in the figure below, the sound pressure needs to get dispersed over the additional area of the new sphere with higher surface area

                                                       Figure: Inverse Square Law - Sphere

In contrast, an infinite ideal point source will have no drop in pressure level. A infinite point source can be thought of as a Wall in a room being acting as single source of sound completely. In this context the sound pressure doesn't have to elongate to accommodate any new area.Hence there will be no drop in the sound pressure with distance. But its not possible practically to have such a source of sound.

The loudspeakers that are used as a cluster are normally point sources and obeying the inverse square law with distance.

Line Source: Line source is a number of speakers coupled together to act as a single source. The main advantage of a Line source is that, it defies Inverse Square Law. There is only 3 db loss for every doubling of distance in case of a Line source. Yup! This is achieved by using the interference that happens when more sources of sound(speakers) constructively. Back to basics!!! 

Constructive interference:

Destructive Interference:

But how can this help in defying the Inverse square law? Its time dependant!! How do we control time?? Lol!! We cant do suspended animation!! But there is another parameter that can help us in achieving the constructive interference that we require. The Frequency & the wavelength. Normally different sized drivers are used for reproducing different set of frequencies. The spacing between the drivers are in our hands. 

Have a look at the picture of the destructive interference again. For the destructive interference to happen at a particular frequency, the second wave should be half wave length apart. So, if its not half wavelength apart its going to be constructive interference!! So if we could get the distance between two drivers adjusted to less than half the wavelength of the highest frequency that the speaker is going to produce, then we can achieve a constructive interference between the waves from those two drivers. Yup! So if the drivers are placed with gaps lesser than half the wavelength of the highest frequency they are going to produce then we have succeeded almost half in creating a line source. Arranging the mid and low frequency drivers in such an arrangement might be easy, as the wavelength of low frequencies are big enough. But it might be little difficult in case of high frequencies as the wavelength is very small (approximatley 0.8 cm for a 16KHZ wave). A Line array Speaker is one which is manufactured with these constraints of spacing between them.

What else needs to be done to make a Line Source? In order to defy inverse square law, the Line source should have a height that is equal to four times the wavelength of the lowest frequency the line source is going to produce. But its nor possible to make a single speaker so tall and hence a number of speakers are stacked up to achieve this. Well!! So Line arrays are a number of line sources stacked vertically to achieve this. But imagine if the same concept of line source needs to be implemented for low frequencies?? Then sub woofers need to be stacked up for up to 45 meters height for a frequency of 30hz(4 x 11meters - wavelength of 30 hz). But it is not of much use and hence subwoofers are normally stacked in front of stage or below the line arrays.

Line Arrays and line sources are not synonymous. A Line array is number of line sources stacked up vertically.

But still, how does a line array defy the Inverse Square Law??

                                               Figure: Line Array - Cylindrical Waveform

Line array by all these constrains radiates pressure in a cylindrical pattern by taking advantage of the constructive interference that we discussed earlier. In case of a cylinder, the surface area is inversely proportional to the distance and not to the square of the distance and hence saving up the 3 dbspl for us. 

 I will update more on Line arrays soon.:)

 

My First & Real Audio Assignment - with Ahuja :p

IS THERE ANY AUDIO ENGINEER WHO HAS NEVER WORKED ON AHUJA REALLY THERE?? (ATLEAST IN INDIA)

As told in my earlier Post, I got selected as an Audio Engineer in a firm that has no connections to media at all in any ways. And i had to join in a short notice of 2 weeks. They wanted me to join as early as possible as they wanted to have a Live sound system of their own as early as possible to enhance the quality of their functions.

First day at work: Joining formalities- Insurance Forms, PF Forms, PF Nomination, Who should be informed in case of death, Accident Policy, etc.. Almost half a day gone in filling of various forms some of which i dint even know what are those for. Second half of the day was gone in waiting for the reporting letter. Even before i could get the reporting letter, I got a call from the person who interviewed me saying there is a party at the CEO's Bungalow, and i have to arrange for the audio system.LOL. I was not even sure of the place and the language. I was struggling to speak to people as they hardly spoke english. It was either hindi or kannada and i dint know both of them :p. Atleast i was able to understand little bit of hindi. Thanks to the hindi movies that i watched with subtitles.:p Atlast they arranged a vehicle for me and took me to the venue.

I saw some technicians already setting up the system that the company owned. It was a few rusted Ahuja Speakers and a 100Watts amplifier. I was thinking wat i have to do with this? I never learnt about ahuja systems. All that i know was the so called "PRO AUDIO". Lol. The technicians connected everything and they switched on the system. The sound was hopeless. The HF driver of one of the speaker was gone and it was distorting so badly. I tried explaining the technicians about the problem. But they were least bothered as i was new to that place and they have been doing functions like this. They saw me like a villain who came to spoil their work. Luckily there was a single person in the technician who could understand tamil. I convinced him to change the faulty speaker and finally they replaced it with a spare speaker that they had. The sound was better eventhough this speaker also had HF problems. Finally the party started and it went on well. 

In the middle of the party, the person who interviewed me came and introduced me to my CEO as an M.tech in Audio Engineering.LOL. He was very happy and he asked me very innocently for fixing goose neck Microphones in all our conference rooms. As he was speaking with me, i got lot of attention and i got a Juice served too immediately. LOL. Finally the program went on well. And by then, half of the crowd knew me and they all said : TODAY, the sound was good. Lol. I was very happy that day for having completed M.Tech. Just because i was present there and i had an M.tech degree, People felt the sound was good. Haha. I dont know if they had said that to encourage me. 

It was after that function i realized the importance of AHUJA. Speak Audio - Ahuja is there if its INDIA. I realized i had to learn to work with Ahuja Systems. After all, none of the company in the world can provide speakers in the price range that ahuja can give.:) I went to my store, found all the ahuja products and learned about each of them and their working. I really never knew till then that Ahuja amps had so much of features in it. If you want MORE SOUND at Cheaper Price, Ahuja is the best!!! :)

So Guys who have dreams of becoming a Audio/Sound Engineer, Learn how to work with Ahuja Systems. You will come across them atleast once in your lifetime :)

An Audio Engineer - Am i?

THIS BLOG IS ABOUT THE STORY OF ME SO FAR!!!

Well! I was an average guy in class right from school and never really bothered much about studies. My wish was to become a software engineer and enter in to Infosys (Which was my dream company at that time). As expected i got lower grades in my 12th grade public examinations(managed to pass though). 

The only course i could afford to get in an engineering college - Media Technology (But ended up getting a degree in Electronics & Media Technology. Lol. The course name itself got changed). I had to select between three courses - Civil, Media, Food Processing and i selected Media, thinking i will still have the chance of getting in to software industry which i was interested in. "The first course in engineering in media", "Studios", "Graphics", "Animation", "Gaming".."blah..blah.." These words were good enough to convince my parents and relatives and me as well to an extent. So i have finally joined in  Media Technology.

COLLEGE: The first day of college and there was a test - tat too in "ENGLISH" for splitting of students in to different sections. Different groups of students from different branches are mixed up and put in different sections. I was put in "B" section along with some ppl from media tech and the remaining from E&I. First day at college, met uthiesh raju, dilip kumar, charles dickens, allwin n many more. I sat in the first bench thinking i should study well as i got less grades in my school. CHARLES Dickens - the first fight (LOL!! - Charles hope u remember :P). But later he turned out to be one of my best buddy. College life started going normal with routines. The first year with common syllabus does not create much of problems and i managed to get average grades.

MEDIA TECHNOLOGY: Starting of Second year -  Media technology from different sections put together in to a single class. Ragging by seniors, new staffs, Electronics subjuects, Maths, Programming Languages etc..We were under the Department of Electronics & Communication.  It was going fine and suddenly the confusion starts. "Where are the studios", "No media subjects", "No media Staffs". Lol, most of our classes went in discussions and arguments. But as i was not much interested in media, i was not really bothered. I was always interested in learning technical things. Finally two staffs were appointed and one among that was Mr.Leo. 

Finally at the end of second year we had a separate department with media subjects and staffs. Luckily inspite of so many fights we still had some papers on maths and some other technical subjects were not removed, which has helped many of us in various ways.

Third Year: Well!! This is the year most of the things had happened both good as well as bad. Quite a number of new staffs were appointed. One among that was Mr. Emmanuel Jerry Rajadhas - the one who is responsible for wat i'm today. Though we never had a subject on Audio, he use to come and take classes during free hours and teach audio. I have never imagined even in my wildest of dreams that i will enter in to the field of audio or even learn about audio. If it was not for him, i would have surely not known even tat such a field exists. Although i did not have much of interest in audio initially, i started learning it as it was the only useful thing that was happening those days. Most of our classes were free as no staffs will come. The studios were getting ready. Atleast we had hopes of seeing the studios before we finish our course..

Electronics & Media Technology: The Next confusion - Should we be given a B.E degree or B.Tech degree. The title of the course should be Media technology or Electronics & Media Technology?? Arguments & Fights favoring both the sides and finally decided with the Electronics & Media Technology. Very Few people were worried about what we were studying rather than the degree or the name of the course. 

Night Classes on Audio: Though i was not very close with jerry sir initially, after the fight with him on an issue, became close with him and started attending the evening time classes after college hours. It was a very few number of ppl who stayed for these classes and it use to go on really late. There were instances where we have stayed overnight and attended classes for the next day straight away. Never knew a person can make learning so much easier and interesting. Yup, Learning became fun and interesting for the first time. Started liking the evening classes more than the college. His classes were so interesting that, there were instances where few of my friends bunk the college and come to college in the evening for jerry sir's classes. He was able to relate with anyone so easily since he had a vast knowledge on almost any area that you can imagine. Whatever questions on any area asked by any person, he will have an answer to say. He inspired me to read a lot and learn new things and gain knowledge on various domains. I started reading and doing studies on own in audio as well as other areas of engineering. I use to read and get my doubts cleared in the next classes. Even for the stupidest of doubts he use to explain and make us understand. We were helping him in the making of the audio studios from the very beginning. The cables, Patch Panels, the tables, PC, tables, - we were a part of it in the making. We stayed more time in the studios than in our hostel rooms at those times. Though i had started learning audio  with interest, still i had my dreams on getting selected in a software company through campus interviews. After all, that was my childhood dream. 

CAMPUS INTERVIEWS: It was towards the end of 3rd year, companies started coming to the campus for recruitment. And Infosys was one among them. It was my dream company which i always wanted to get in to. I prepared the whole night for the aptitude before the interview date and i was confident of clearing the aptitude. I did clear the aptitude round and went on for the personal interview which was the last round. It was almost like final if you clear the aptitude round for the infosys. The personal interview is just for a formality. But to my surprise i have not cleared the personal interview. Around 8 people were rejected from the people who cleared the aps round. and i was one among the rejected few. That was the worst day of my life i thought. Many other companies came for interviews. but i did not get in any of them. And finally i decided to go for higher studies as i did not get any good offers. 

MULTIMEDIA TECHNOLOGY: I joined again in the same college and again a new course Multimedia technology. I did not know seriously if i was doing a mistake by selecting a new course again. But then, i thought i can atleast learn things from jerry sir if i stay there. These two years is the time when i started a lot of self learning and started studying things on own. Though the college syllabus was very easily manageable, i still use to read whenever i get free time. I learned anything and everything that came my way. I came to know that it will be useful for me somewhere. Things that i learned with respect to audio during these days  were very minimal. I still wanted to get a chance to go in to a software company. I got an offer from wipro through the campus interview.I was very happy and i thought finally i am getting in to a software company. 

AUDIO ENGINEER: When everything was going fine, there was an interview call from a company for the post of Audio Engineer. It was forwarded to me and i thought i will just go and attend since it was told that they will pay my travel expenses and food and accommodation. The interview lasted for 3 hours. The job profile was too big and the responsibilities were bigger for a fresh candidate. Till then i have seen line arrays only in pictures, Let alone line arrays, i have not worked on normal audio systems itself on my own. I had only theoretical knowledge. But in interview it was told to me i have to buy a line array system and operate rhat and maintain it. The interview panel was satisfied with my knowledge on audio and they selected me. I was in a dilemma as i had an offer from wipro and on the other side this offer. "Two Roads diverged in a yellow wood" Lol. Finally i had chosen this offer as an audio engineer and joined here. That is how i became an Audio Engineer. I have done quite a few projects here on audio which i will update in my next post. Well!! I am an audio engineer too!!