Bookshelf Elevens

Bookshelf Elevens


Project Category:
Bookshelf Speakers

Project Level:

Project Time:
1-8 Hours

Project Cost:
Under $100

Project Description:
2 way bookshelf speakers based on an Optimus Pro77 set from a thrift store. The original woofer surrounds were shot and bought replacements from Parts Express to restore them. Ended up also replacing the metal cases new plywood boxes.

Design Goals:
Replace the woofer in a set of older speakers I picked up for $5.

After realizing the replacement drivers would not fit in the metal box fronts, building simple new wood cases was my decision. Wanted to see if I could make this set work again with little investment.

Driver Selection:
WP-5211 5-1/4″ Poly Cone Foam Surround Woofer Pair 8 Ohms 299-2238 factory buyout

Optimus Tweeter Sd-72

Enclosure Design:
1/2 MDO plywood boxes.

Inner dimension 8.25″ h x 5.25″ w x 4.5″ d

No port yet, maybe in the future…

Enclosure Assembly:
Glued and brad nailed cases with poly-fill stuffing. Drivers are flush mount and screwed. Silicon caulked the tweeter plate to the face.

Crossover Design:
Used the original Optimus Pro 77 crossover which has

4.7uf 50V bi-polar electrolytic caps in series with the coil/tweeters,with the 0.4mH coil in parallel with the tweeter

Tips & Tricks:
Use a router circle plate such as the Jasper for the driver cut-outs!

saves hours of time in the end for $30.

Total investment of $25 and 5 hours of time.

Sound is clean strong and will give years more music

About the Designer:
Architect/fabricator and music lover

Project Parts List:

WP-5211 5-1/4″ Poly Cone Foam Surround Woofer Pair 8 Ohms

1 comment

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  1. 1

    You might take this to the next level by building Zilch’s famous Minimus 7 upgrade crossover that is documented over on the Audiokarma forum. I did this for my Minimus 77 (same speakers, older model to yours) and it sounds great.

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