DIY sites

[navin]

Originally posted by 7V
Also, many people were totally turned off high school physics at school. I suspect that many would-be speaker designers need to relearn the basics of high school physics.Can anyone else come up with a simpler explanation of Q or expand on navin's version?

one day when i can afford to retire i will spend more time on this site right now i butt in and out between work. unfortunately high school physics turned me on. i was (still am) too ugly for the women anyway.

changing mech Q (in spring physics) would depnd on the spring qualities as well as the load (if any). and dont forget that a loudspeaker suspension is actually many srpings in series and parallel (if you can visualise the suspension to be one spring and the spider(s) to be another) spring qualities are dependant on the thickness of wire, number of turn, distance bet turns, dia of turn etc....

[navin]

BTW sorry if I offended anyone.

[navin]

maybe these links can help

http://physics.nad.ru/Physics/English/spri_txt.htm

http://www.maximacar.com/enclosure_design.htm

http://www.physics.csulb.edu/151lab/exp9/theory.html

http://theory.uwinnipeg.ca/mod_tech/node33.html

i am sure there are better (can anyone find a copy of Fundamentals of Physics by Resnick / Halliday) we used that in school.

[7V]

Originally posted by navin
BTW sorry if I offended anyone.

I'm sure that you didn't.

[uli]

Hi,
Q stands for quality which is the inverse of the damping of a
filter at its working frequency.
Example:
Filterfrequency say 100Hz, Q=0,7 damping -> 1,414
20log1,414 =3 thus 3dB damping.

Uli

[Colin]

I thought Q was the funny old guy in the James Bond films.

Anyway, back to the speaker building sites ... If you're new to speaker building, it might be worth tackling a kit speaker first off. There are lots of them out there - pick something simple (not your ultimate speaker), learn from that and then launch into designing your own. Some of the kit sites have information on them which is of general use.

Regarding books, there is a little book called AN INTRODUCTION TO LOUDSPEAKERS by Vivian Capel, published in by Babini (www.babanibooks.com). It's very simple and straightforward - only includes one speaker design but good on general principles.

Colin

[wintermute]

Originally posted by Timn8ter
Not to be contrary, especially to such knowledgeable fellows but, if the first book I read on loudspeaker design was the Cookbook I may have given up right there. It's very involved and possibly overwhelming to someone just getting started. I usually recommend The Great Sound Stereo Speaker Manual by David Weems to get started. Once you're comfortable with that the Cookbook will be much more enjoyable and understandable.

Good point. I only just bought the 6th ed Loud speaker design cookbook (haven't had a chance to read it yet).

I cut my teeth on:

"Designing, Building, and testing your own speaker system with projects" By David B Weems. Would recommend it for newbes as it's not too technical.

List of chapters:

1. How a speaker works
2. Kinds of speaker enclosures
3. Speaker box construction
4. Closed Box speaker systems
5. Ported Box speaker systems
6. Crossover networks
7. Fun with a computer program
8. How to choose and use your speakers
9. Testing your speakers
10. Projects

Appendices
A Usefull Formulas
B Wire data for Homemade coils
C computer programs
D mail order houses.

Regards,

Tony.

[f4ier]

Ray Alden's "Advanced Speaker Designs (for the hobbyist and technician)" is another good beginner's book. Vance Dickason's Loudspeaker Design Cookbook should make more sense after reading Alden's book.

Of course, all theory and no play is no fun at all. Theory should make more sense if you play around with simulation software...

begin shameless plug {
Subwoofer Simulator -- bass enclosure simulation program
Crossover Simulator -- electrical filter (crossover) simulation program
} end shameless plug

.... to help make better experimental enclosures and crossovers. Almost everything you'd need to successfully design loudspeakers from the ground up can be found at the FRD Group site.


Steve Ekblad maintains one of, if not the biggest, audio links page.


HTH

Isaac

[DIY_Peter]

Originally posted by Dave Jones


I can't recommend starting with that book. It's tough going for a complete newbie. I speak from very recent experience. There are far too many terms that he uses without defining, or without defining adequately. It gets very, very frustrating.

For example, on the first page of chapter one, he gives,

Q -- ratio of reactance to resistance (series circuit) or resistance to reactance (parallel circuit)

Qts -- total Q of driver (woofer) at fs, considering all driver resistances

I couldn't figure out what that meant the first time I read it, and if the awful truth be known, I *STILL* don't know what it means. I've now seen enough graphs of low-Q this and high-Q that to have an intuition for what the effect of Q is, but that's about it.

I've read the book three times now, and I still can't understand most of it. Furthermore, the name is deceptive. It's not a cookbook at all. It's more like a sophmore textbook for wannabe cooks. We freshmen can't make heads or tails of it.

Finally someone who has the guts to tell the truth about that book. I had exactly the same feelings about it. I have a science background and I can say that if I ever wrote something like that during my student days, my professor would throw it out of the window.

The guy probably knows a lot about speakerdesign, but he sure can't write a decent scientific work.

Not a good beginners book.

[Nappylady]

Hmm.

After seeing plots of impulse (step? correct me if I'm wrong) response for different Q woofers, I think a good analogy is a car suspension. A good mechanic friend of mine told me that checking a suspension is easy--stand on the bumper and bounce once. If the car goes down and up once, your suspension is good. If your car goes up and down a bunch of times, your suspension is shot.

Good suspensions have low Q, bad ones have high Q. High Q will give you a horrible ride, and floppy, slow bass. Low Q will get a smooth ride, and tightly defined bass.