I had a pair of Realistic Nova-18's that were in need of repair. These were purchased new sometime around 1993-1994. The foam surrounds on the woofers were rotted out. At some point I replaced the original paper-cone tweeters with piezos. They weren't much of an upgrade. In fact, I always thought they sounded overly harsh / bright. I guess didn't know any better, at the time.
Surveying the damage
After failing to find a replacement woofer that was close match for the speaker cabinet, I decided to repair the old woofer instead. In spite of how bad the woofer looks, the only thing wrong with it is the foam surround.
Here is the original insulation that the speaker came with. I never liked the idea of having fiberglass insulation in a vented speaker cabinet.
The original crossover was just a single bipolar electrolytic capacitor that was wired inline with the cone tweeter. I must have bypassed it when I installed the piezo tweeter. The inductor is something I wound by hand onto an old solder reel. This must have been my attempt to "improve" upon the stock crossover design. Not exactly sure what I was thinking here. I'll chalk it up to youth, inexperience, and having more time than money.
Here is a closer look at the original stock tweeter-capacitor.
Newbie speaker refoaming
I started by removing the bulk of the old foam by running my finger along the edge of the speaker cone.
I was able to salvage the old gasket by cutting through the foam underneath it, with a box cutter.
Since this is a simple paper-cone woofer I was able to get away with using solvents to get rid of the old foam and glue. Acetone worked great for dissolving the old foam, but it took a lot of effort to remove the old glue from the speaker basket.
After trying and failing to dissolve the glue, surrounding the dust cap, I finally ended up cutting it with an X-Acto knife.
Nobody makes foam surrounds that are an exact match for this speaker. That said, I was able to find some foam that fit inside the gasket, and overlapped the speaker cone a sufficient amount. Here I trimmed the outer edge of the foam, using the old gasket as a pattern.
I made shims out of an old notecard and used them to keep the voice coil centered while attaching the new foam surround. This part is critical. You don't want the voice coil to rub against the pole piece. It makes the speaker sound bad, and it can damage the voice coil. See the video below to get an idea on how easy it is to get the speaker mis-aligned when the foam is removed.
With the shims in place, I laid the new foam surround upside-down and applied speaker glue to the inner edge. Then I flipped it over and glued the inner edge to the speaker cone. The glue sticks really well and it sets up really fast.
Then it was time to glue the foam surround to the speaker basket. The shims make this easier to do. When you lift up on the speaker cone, the shims will keep it from lowering back down. This provides clearance for the foam while one is applying glue to the speaker basket.
This is what it looks like with both edges of the foam glued in place.
With the surrounds in place, I removed the shims, then turned my attention toward removing as much of the old dust cap as I could. After trying unsuccessfully to dissolve the old glue with Acetone and Xylene, I finally had success, using Toluene. I applied small amounts, using a q-tip, around the edge of the dust cap, then used a dull x-acto blade to carefully separate the remnants of the dust cap from the speaker cone. Toluene is nasty stuff to work with, but it was the only thing that would do the job. The picture below shows the speaker with the original gasket glued back in place, right before I glued down the replacement dust cap.
I used screws to attach a new crossover to a piece of hardboard, then glued the hardboard to the side of the cabinet, using hot glue. I also added an L-Pad, in case I ever need to tweak the tweeter volume. Below is a picture taken after I finished rewiring.
Here I'm using foam insulation in place of the fiberglass that was removed earlier.
Here is the ugly hole, left over from my youthful speaker indiscretions.
I fabricated a plate out of hardboard to cover the old tweeter hole and to provide a place to mount the new tweeter.
This is the end result after repairing the woofer and replacing the tweeter.
Newbie speaker refoaming - Part 2
Below is some video that I took while refoaming the other woofer:
|10 inch Refoam Kit (F10-4)||Midwest Speaker Repair||$24.95|
|Paper Dust Caps (with lip) - 2.5 inches||Midwest Speaker Repair||$2.00 each|
|Pro-Grade HEAVY-DUTY Nitrile Rubber Speaker Glue||Springfield Speaker Repair||$6.95|
|Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter||Parts Express||$19.75 each|
|Dayton Audio XO2W-2K 2-Way Speaker Crossover 2,000 Hz||Parts Express||$29.50 each|
|Speaker L-Pad Attenuator 100W Mono 1" Shaft 8 Ohm||Parts Express||$10.30 each|
|Acoustic Eggcrate Foam 2 Pcs. 2-1/2" x 12" x 12" for Speaker Enclosures Only||Parts Express||$7.49|
|1/4 (1/4CAT) x 2 x 4 Hardboard Panel||Menards||$4.34|
Last Update: 4-15-2018
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