FFT

So you wish you had some better tools. Geez, why do I have to carry this rack full of test gear around. I wish we could just reduce it down to half the size.

And then we did.

Well I just wish we could get it down to where it was just a card in my PC.

Done.

How about on the laptop?

Check.

If only I could just get an FFT Analyzer as an I-Phone app.

Mission accomplished – expensive though – who would want to pay $20 for a FFT analyzer?

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Face it- we are hopelessly spoiled. It may help your perspective to consider for a moment the challenges of those before us. LONG before us, in the field of acoustic measurement and system analysis – like folks that used stone knives and bear skins to set their delay lines.

Take a look at this simple setup and you will see how easy we have it. This will get you a screen grab of a waveform. Easy eh?

Want to do a system tuning? This should help.

Now take a look at the tools below . What do you think they are? What will they do? Any guesses? I would love to hear them.

I have some interesting historical books on this subject and thought it might be fun to take a look at some of these old tools. I have a tuning trip tomorrow ( I will have to remember to bring my forks) but then I will start to describe what the happened in the land before time (alignment)

The second edition came off the press in October of this year and I am quite happy with the result. First thing is that the book can sit on your lap or a table without flopping around. The graphics came out much better. I was able to get them reformatted so as to get the most crtical elements like MAPP and FFT plots to the maximum size allowable on the page. I also was much more directive in getting related graphics – like a series of 4 plots, to be placed together on the page so that they can be viewed together. This was not a minor effort. Probably 80% of the graphics were reworked but this time the effort seem to pay off. When I open the book – the sizes seem right and most importantly the data is visually clear enough to prove the points being made.

I have over two years of teaching experience behind me with the old book, and this was very helpful in terms of guidance toward the second edition. I expanded on things that were found to be the most useful in my seminars and reduced some areas that were redundant as well as ones that repeated themselves or said the same thing over again, repeatedly. While the publisher gave me a goal of 25% new material and 15% longer than the 1st edition, I just felt it would be cruel and unusual punishment to add 75 pages. I did manage the 25% new material but increased the density so that the expansion is less than 8% (40 pages). I have yet to hear a complaint that my book was too short so I tried my best NOT to make it longer.

The section on cardioid subwoofers was expanded and contains a much improved explanation of how the steering occurs and how frequency affects the directionality of subs.

The discussion of the behavior of modern line array speakers was also expanded and includes the use of all-pass filters for beam steering.

The design chapters were reworked very heavily with a much more linear set of design procedures for deriving models, spacing, splay angles etc.

A final chapter was added that provides example design for a theatre, concert hall, arena and house of worship. This chapter brings together all the concepts described previously and is almost entirely graphical (about 200 new graphics were created for it).

Hopefully this will help clarify what’s new. Any comments are welcome

6o6

And you think you have it rough!

Sound Systems: Design & Optimization – 2nd Edition