How can I squeeze more life from a pair of Onkyo SKF-200F ?

[ThomasW]

Did speaker builder magazine go into things like impedance curves back then?

All the articles in Speaker Builder (now a part of AudioXpress) are submitted by readers. So the data was and is limited to whatever the designer provided.

Electronics Illustrated, Popular Electronics, even Popular Mechanics contained speaker building articles way back when.....

The earliest DIY designs were horns since amplifier power was so expen$ive.....Lots of people think transmission lines are some current rage. There were multiple Speaker Builder articles about TL's in the 1970's

To the OP.....instead of buying random speaker components where you have no real idea whats going to happen, buy this book..."Speaker Building 201: A Comprehensive Course in Speaker Design" by Ray Alden

[Dennis H]

I remember buying this one shortly after it came out. My friend google found it in someone's audio bibliography -- all I could remember is it was a Sams book.

How to Build Speaker Enclosures
Alexis Badmaieff & Don Davis,
© 1966 Howard W. Sams & Co., Inc., Indianapolis, IN

general, port tuning & testing, chokes & crossovers (dated but interesting)

[servicetech]

To the OP. See if your local library has any speaker building books, the price is right

[fjhuerta]

The OP said he'd like a sub but can't afford it right now. Instead of wasting good money on dubious mods to his speakers, regardless of how educational that might be, I'd suggest he put the money in his sub piggy bank. A sub will make a real improvement in his sound and is a very good first DIY project.

My first DIY project was an Adire Audio Tempest sealed box. 7 years later, I still use it.