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MultiWay Conventional loudspeakers with crossovers 

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28th February 2008, 12:48 AM  #11 
diyAudio Member
Join Date: May 2004
Location: Sydney

I got a 4 year BSc pure maths as my first Uni degree 23 years ago. My advanced maths are all gone but only the basic stuff. I agree with John K that we don't really need advanced maths to do what is required in speaker design because of the availability of computer software.
The good news is that we can now leave the maths to MJK, John K, and others to do... Regards, Bill 
28th February 2008, 01:02 AM  #12 
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Join Date: Nov 2006

Bluto
I don't know if you've tried Ray Alden's book, "Loudspeakers 101" (first edition  there is a new edition, but I haven't seen it), but it is pretty good for what you want to learn. He goes through step by step doing the calculations for speaker and crossover design. You don't need to be able to derive the formulas, and most of the algebra is of the simplest type ie V=IR, change to I=V/R, etc. Also, you need to know how to use a calculator to make it give the right answer; ie 2(21)(2)=______ I believe he goes through that as well. If you are patient and repeat what you don't get the first time through, you will get it. Some of the formulas Mr. Alden goes through in his book are really, really, long. But then, trying to design a speaker doing hand calculations would be nuts. The book was great to help develop an understanding of the symbols and terms. To actually design speakers, I use Crossover Pro from Harristech. JJ 
28th February 2008, 01:20 AM  #13  
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Join Date: Feb 2002
Location: Clifton Park, NY

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28th February 2008, 02:29 AM  #14  
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Join Date: Apr 2002
Location: Newcastle, Australia

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Yesm, leave it to the guys who use the heavy stuff on a regular basis. ;)) 

28th February 2008, 04:14 AM  #15 
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Join Date: Oct 2005

Regardless of Bluto’s AKA, I don’t think him a fool at all. I feel like I’m in the same boat. I want to understand this stuff too, but using someone else’s plug & chug formulas will never lead you to more that a simple understanding of what’s going on. For example, if I wanted to understand why Lynn Olsen’s Ariel speaker cabinet starts out as something that looks like a transmission line and ends in a labyrinth (?) and what advantages or disadvantages that might bring to the table, I’m not going to learn that in Speaker Building 201.
I got farther in math than Bluto (1 yr college calculus, 1 yr calculus based physics, yada, yada) but between what I’ve forgotten and what I’ve never learned, getting started on the path to understanding this stuff can be intimidating. I think Bluto can learn this if he has the time and interest and a road map to follow. Maybe you guys can help us out by suggesting a curriculum for a BS in speaker building with a minor in audio electronics. I was thinking about combining some of the basics (algebra, calculus, physics, etc) with some practical stuff like howto books while making a few published designs along the way to learn the practical side. Any takers? My input to Bluto would be that the Loudspeaker Design Cookbook is probably a great second book. I would start with something a little more basic like the Speaker Building 201. Looney Btw, if anyone can answer the Ariel question… 
28th February 2008, 05:15 AM  #16 
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Join Date: Mar 2007
Location: Canandaigua, NY USA

I have no natural abilities with math, but I can slog my way through reasonably complicated stuff. As long as I get it into a spreadsheet or dedicated program right then and there, I'm ok. An hour or so later, I've forgotten everything! IMO, the usual TS based loudspeaker calculations are pretty easy if they're presented well. There was a series way back in Speaker Builder that did an excellent job. My old Loudspeaker Design Handbook did a good job, but I haven't updated in a long time.
Here's a secret for electronics math. Shop used book stores for intro Electrical Engineering textbooks from the '40s to the '60s. Things from authors like Timbe & Bush, Terman, and the electrical measurement books by Stout, Harris, and Farmer. They were designed for people who actually had to build things, and the explanations and math are far better presented, than the modern texts designed for math prodigies. For a horrible example in mechanics, look at an old book on vibration, vs a modern one. From clear and simple, to completely unfathomable. IMO, it's no wonder that freshly minted engineers need so much training before they can do anything. For modern books, find a used copy of Barnsted's (sp?) Circuit Analysis that goes into depth, but is pretty clear. Some people like the ARRL handbook, but I find the index and organization dreadful. 
28th February 2008, 05:44 AM  #17  
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Join Date: Jun 2002
Location: USA, MN

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As to curriculum, the class that really began to open things up for me was "Analysis of Dynamic Systems" Basically this was an applied differential equations class that involved solving mechanical translational/rotational, electrical, hydraulic and thermal systems the hard way before they taught us the shortcuts. Some call this a "Springmassdamper" class. The prerequisite for that is Differential and integral calculus and a class on differential equations (most importantly laplace transforms), as well as a year of physics and engineering statics and dynamics. After that a formal introduction to circuit analysis, control theory and a course on engineering acoustics should lead you well on your way to having the tools to learn anything you want. During that, to get Audio specifics, you spend a lot of time reading old Journal articles. This is not to say that all of that is "required" to make great sounding speakers. It is only required to understand the process  in the connotation I have for the word understand in this particular situation. My first book on this stuff was by Weems  I looked at the equations he gave, and by comparing them to his design writeups it became apparent that none of his "designs" were done after the sort of cookbook equations that he gave in his books. Vance Dickason's LDC made me hunger for whatever was behind the alignment tables  then I learned that the whole alignment  QL thing he recommends as a design process is really rather excessively particular about adhering to alignments  and crossovers can't realistically be designed without measurement and modeling software and/or a lot of trial and error. One can always get a copy of Speaker Workshop, work through the long unofficial "manual"  really a tutorial written by Jay B.  and I really think there is a lot more useful content in that guide than there is in the LDC.
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Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. Carl Sagan Armaments, universal debt, and planned obsolescencethose are the three pillars of Western prosperity. —Aldous Huxley 

28th February 2008, 08:09 AM  #18 
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Join Date: May 2005
Location: Melbourne

I guess I am just a tad more comfortable with the maths than Bluto but still know nothing. There is a symbol which I can't recall that is often used in calcs put up by MJK and others. I believe that it represents the square root of 1. I try to understand this, look it up and am told that it is an imaginary number. If I could see how this is used in an actual equation with a result it might make sense to me but at present such things are beyond what used to be called gibberish or double dutch. No offence meant to anybody.
Sometimes just seeing something worked through can help a lot. a big problem is that a lot of teachers, and mine was like this, cannot really explain or work through a sample. They are so capable that they leave steps out which they have done mentally so what you see on the board does not help understanding. jamikl 
28th February 2008, 05:47 PM  #19  
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Join Date: Jun 2002
Location: USA, MN

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An imaginary (aka complex) number is really a number that is used to describe magnitude and phase. The complex number 3+4i has magnitude=sqrt(3^2+4^2)=5 and phase=arctan(4/3). Aside from the mechanics of working with them, that is enough to get you by....
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. Carl Sagan Armaments, universal debt, and planned obsolescencethose are the three pillars of Western prosperity. —Aldous Huxley 

28th February 2008, 09:34 PM  #20 
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Join Date: Mar 2007
Location: Canandaigua, NY USA

I curse the chowderhead that called that number "imaginary". That description messed me up for years. For the way we use it, there's nothing imaginary about it. Complex is just fine, thank you very much. There has to be a better way to teach math, but "the new math" wasn't it.

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