I purchased a pair of brand new Advent speakers in November of 1979. My speakers are original with the exception of the foam surrounds and the crossover capacitors and resistors all of which were replaced for the first time as shown in the following pictures.
Replacing The Foam Surround
I peeled the old foam surround from the speaker and the adhesive from the speaker basket frame. Then cleaned the frame with a cloth dampened with isopropyl alcohol.
I used my fingers and an X-ACTO knife with the blade perpendicular to the speaker cone to gently scrape the foam surround material off the cone that didn't peel off. No isopropyl was used on the speaker cone.
I cut away the dust cap with a small X-ACTO knife being very careful to stay away from the speaker cone and spider.
Then I placed shims between the magnet and voice coil to center the speaker cone.
Large picture of woofer with ruler on top for reference.
I used (Surround Kit For 10" Advent Steel Frame) part # 260-953 from Parts Express.
The foam surround is attached to the back of the speaker cone and to the front of the basket frame on these speakers. The center curved area of the foam surround faces to the front of the speaker. The new dust cap is a smaller diameter than the original and you can see the outer area of the old dust cap still attached to the speaker cone.
Here are the original woofers after I replaced the foam surrounds, and dust caps. I worked on the speakers very patiently and they turned out very well. The cones centered up nicely and the whole process was very straight forward.
Here is group of images of the woofer and tweeter drivers from one of the loudspeaker cabinets.
Large Advent speaker cabinet with drivers removed. The cabinets are filled with foam damping material. You can see the outline of the square magnet structure pressed into the foam by the woofer.
Replacing The Crossover Parts
The original capacitors were Unicon brand rated at 13uF and 50V.
I replaced the capacitors with M.D.L. brand rated at 15uF and 100V Non Polarized.
The old capacitors measured 14.2uF and 14.6uF. The new capacitors measure 15.6uF. (1 capacitor in each speaker cabinet crossover).
If you are replacing the capacitors and you can't find the correct value capacitors for your crossovers, as an example you could use a 10uf and a 3.3uf capacitor connected in parallel in place of a 13uf capacitor.
Make sure the rated voltage of the new capacitors is equal to or higher than the original capacitors and the capacitors must also be bi polar or (non polarized).
At the time I replaced the capacitors, the 15uF capacitors must have been the closest value available from my parts supplier or the closest value at a price I was willing to pay.
If you planning on replacing your capacitors, I would suggest staying as close to the value of your original capacitors for optimum performance and to reduce the risk of damaging your tweeters.
A higher uF value capacitor used on this crossover will lower the crossover frequency to the tweeter and pass more energy to it.
The original resistors were a Culber 1 ohm, 10 watt with 10% tolerance and a Rockwood (1.5 ohm?) 10 watt with 10% tolerance.
The 1 ohm resistor measured 1 ohm and the other resistor measured 1.9 ohm. The 1.5 ohm resistor from my other speaker had failed open.
The replacement resistors in each crossover consist of a 1 ohm & 1.5 ohm Dayton Audio Grade resistor both rated at 10 watts and 2% tolerance.
The New Advent Speaker Manuals.