This is my first post here and I wanted to participate and contribute back to the community as I have been lurking for a long time when making my purchase/upgrade decisions to switch to JBL. I have been building/tinkering with speakers for many years now and came across my first pair of serious JBL’s last year in the form of S4800’s. They provided me with a great listening experience over the last year and helped remove me from the troubles of the world.
I spent a significant time listening to them, and always wondered can they be better? I thought about upgrading to Be diaphragms, switching to active crossovers, etc. and figured I would first try to charge couple them as I have never experienced a CC’ed network.
My primary goals for the modifications were to:
- Minimally impact the external appearance/build quality of the speakers
- Dampen the cabinets better
- Charge couple/upgrade the networks without having to completely rebuild the boards/make new boards
- Make the speakers sound better for a reasonable cost
I used Solen fast caps in place of the OEM 100 VDC yellow cheese capacitors. I determined there was enough space to mount them vertically in all locations and re-use the existing PCB’s. Hot glue/zip ties were used to affix the capacitors and I find that this mounting is sufficient for home use without risk of damage to the networks. I wired the charging resistors point to point as if on a tube amp. I also used A23 12v batteries instead of the usual 9v because they are smaller, and provide a slightly higher biasing voltage. A separate battery is used for each network LF and HF/UHF to permit biamping in the future. The batteries are mounted with Velcro inside the speaker directly in front of the port tube, it is easy to reach in and change them.
While the speakers were apart I determined that one of the internal windowpane braces was not glued on the front baffle side from the factory (it rattled if you knocked on it). I had to implement a strategy to remedy this – I decided to cut small wood wedges and use them to pretension the brace.
Sonic barrier 3 layer damping was applied behind the woofer to the back and sides. The original 1” fiberglass was reused and the bottom chamber were damped with some 1” thick denim insulation.
My overall impression after the modifications is very positive. My original impression was always fantastic, the speakers handled many different genres and qualities of recordings without becoming too revealing, or fatiguing. After the modifications the bass is tighter, fast drum patters are more distinguishable. The charge coupling seems to have improved the transient response and individual musical notes are more strongly defined (cymbals have the most pronounced effect.
I am extremely pleased with the ~$200 in modifications, as they have elevated the performance of the speakers to a level that is much more enjoyable. I am convinced that charge coupling provides a positive benefit.
OEM HF/UHF network
OEM LF Network
Upgraded LF and HF/UHF networks
Upgraded HF/UHF network showing charging resistors point to point wired
S4800 makes a great speaker stand (temporary listening setup while I was working on the JBL's)