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Old 20th October 2012, 06:41 PM   #1
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Default Information on the Physics of Bass Reflex Enclosures

Hello All.

This is my first post here but I have been lurking for quite a while. A little background to introduce myself and then a request if you would please.

I am a quite experienced electrical engineer (background is electromagnetics and RF circuit design). I have done a few years of electrical audio design along the way.

I have never built a speaker before in my life but it is something that I have wanted to do since I was a kid.

But I am interested. I have access to some rather incredible test facilities at work (an anechoic chamber for example) and the best electronic test equipment that my company's money can buy. Call it a job perk.

I want to build some loudspeakers. Some incredible loudspeakers. To do that, I think it is important to understand the physics behind the acoustics and understand them well.

I am presently studying TS parameters now.

Can anyone here point me to sites/books/papers that they would recommend and they think would help me in understanding the physics, the mechanics and acoustics that is, of loudspeakers, particularly Bass Reflex designs?

Most of the best loudspeakers that I personally have heard utilize this design type and hence this is the one that most piques my interest.

Thanks.
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Old 20th October 2012, 06:47 PM   #2
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FWIW, undiluted papers, such as those that would delve into wave mechanics in detail, are fine with me. I would prefer lighter reading to start with though. Who wouldn't?
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Old 20th October 2012, 07:01 PM   #3
Pano is online now Pano  United States
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Welcome to the forum Frankie.
Loxahatchee?? Jeez, that was all swamp when I lived in PBC. Things sure change.

There are some great books that get recommend on this forum a lot. Wish I could remember what they are. Someone will.
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Old 20th October 2012, 07:24 PM   #4
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First of all, understand that acoustics are thermodynamic, and electrical analogues, while useful (the math is way simpler!), have their limits. Any time you get stuck, "follow the heat".

Join the AES. I think they still have bound volumes of the speaker stuff available; follow it up into the '80s, at least. Thiele's idea was a great paradigm shift, but it oversimplified things, and the later work of Small and especially Keele is important. (From my own path, I think finding the work of Novak and working through the math will give a better perspective on the Thiele/Small stuff and keep you focused, but it's not likely the quickest path.)

You probably should have a broad reference such as "Sound System Engineering" by Davis and Davis, or whatever the fellows building studios and stages are using now.

For lighter reading, Parts Express has a good library. Dickason's "Loudspeaker Design and Theory" is pretty comprehensive (though you won't learn much if you read all the AES papers first ), and Joe D'Appolito's Testing Loudspeakers is a must-have. Mostly, though, most of the published stuff is fairly lightweight and at best a popularization of the AES papers, at worst a regurgitation of earlier, misinformed works.


For a starter, try this site:
The Official website of D.B.(Don) Keele, Jr.
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Old 20th October 2012, 07:41 PM   #5
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Relatively light ready, get Dickason's Loudspeaker Design Cookbook. For heavier, theory based stuff, a must read is the AES Loudspeaker audio Anthology 1953-1977. It's a compilation of all the loudspeaker related AES papers written over that time period, and it includes the landmark T/S parameter papers by Thiele and Small. It can be had here.

Loudspeakers: An Anthology of Articles on Loudspeakers From the Pages of the Journal of the Audio Engineering Society,Vol. 1-Vol 25 (1953-1977): Audio Engineering Society: Amazon.com: Books
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Old 20th October 2012, 08:18 PM   #6
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Thanks guys, this is a great start for me. I'm thinking a mix of overview (for the broader picture) and heavy theory (to get a comprehensive understanding) is probably the right path to go down.

The lead engineer of our acoustics department (I work in the high tier portable & mobile radio business... think FBI, marines, state police) has offered me use of a spare license for their acoustics software and training on how to use it (the caveot is, appropriately so, that I will act as a liason, or bridge b/w the electrical and acoustical engineering groups, which is fine with me). The name of the SW eludes my memory, but I do know it's along the lines of $10K US for a license.
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Old 20th October 2012, 08:20 PM   #7
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Ouch! Just got bit by the half-hour edit rule. I envy all of you who can typo fast. (BTW, what good is the "contact administrator" thingie if you lose everything going to a new page?!?)

Anyway.... something messed up with cut and paste - Speakerdoctor is correct, Dickason's book is the "Loudspeaker Design Cookbook".

And I went on to say I'm not really a fan of the AES.... but I'll spare you the rant. What I really wanted to say was "Welcome!" You'll likely find as much good information here as anywhere else. There's no government funding for speaker research, and with the PC based tools we hobbyists now have, you stand as good a chance as anyone to seriously contribute to the art. So, good luck on your journey.


Or... yeh.... if you have $10K software at your disposal, AND time in an anechoic chamber...

Last edited by Keriwena; 20th October 2012 at 08:22 PM.
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Old 20th October 2012, 08:32 PM   #8
AuroraB is offline AuroraB  Norway
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What's wrong with good old Olsson, Beranek et al ?????
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Old 20th October 2012, 08:33 PM   #9
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Well, I've been with this company now for 15 years, and I still kick myself for not taking the leap into this endeavor earlier with the embarrassment of riches at my fingertips, such as the anechoic chamber (I'm buddies with all the acoustic engineers) the SW, and the electronic test equipment at my beck and call (I have BOTH a Rohde and Swarz UPL Audio Analyzer AND an Agilent U8903 Audio Analyzer in my office AND a full copy of Labview on my laptop). I can also sign out most any equipment that I need.

So, take all of that into account, and then I find this place, which after reading for quite a while I have concluded is chock full of very knowledgeable and competent speaker builders, and viola!, all the reasons not to do it are gone.

I think I'm gonna like this place. And have a lot of questions.
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Old 20th October 2012, 08:34 PM   #10
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Quote:
Originally Posted by AuroraB View Post
What's wrong with good old Olsson, Beranek et al ?????
Noth'n. They're in the AES Anthology.
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