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I am wondering whether anyone has tried to swap out 8" (200mm) sub behind the rear seat in the factory B&O system with another high quality thin profile 8" driver. I have not yet pulled the actual driver out to measure it, but I am curious if anyone has tried this, maintaining the rest of the factory set-up, and if so, what you tried and what you think of the results. I recognize that there are issues of matching driver impedances and that the low quality enclosure for the 8" driver may not be very good or optimal for a different 8" sub, but I got to thinking about it and am wondering whether anyone has tried to do a simple driver swap.
To make it worthwhile you should fiberglass the inside of the existing enclosure to make it stronger. A couple layers of mat or some "fiberglass milkshake" should do (google it, it is fiberglass bondo mixed with FG resin/activator). Otherwise the stock enclosure is a flexible plastic tub.
You may have enough watts. Supposedly the B&O system is 675 watts total... figure 200-250 watts of that must be for the subwoofer. You could get a 8inch subwoofer to sound great off that amount of watts. I don't see how many ohms the stock sub is, so pull it out of the enclosure so you can match the driver's impedance, see if its DVC, calculate mounting depth, etc.
I've done some additional research and I believe that it is a DVC driver with each coil being 4 ohms. I will pull it out and measure it this weekend. I will also do some basic measurements to figure out how much actual power the amp uses to drive the voice coils. I appreciate everyone's input and really just wanted to know if anyone has tried this yet. I've done many of my own installs of audiophile level systems in my vehicles over the years, but really don't want to get that involved with this system. I recognize that I won't get booming bass with a single 8" driver, no matter whose driver it is, but I am hoping that I can at least clean up some of the muddiness of the factory B&O sub. Thanks all.
So I took out the B&O factory sub to do some basic measurements. It is an 8" dual voice coil sub. Each coil is about 4 ohms (I measured 4.4 on one and 4.3 on another). I don't know how the coils are wired within the amp, but my very rough guess based on very rough measurements is that the sub gets about 150 watts max from the amp. If someone has actual specs, I hope they post them. I have been unable to find any specs for the B&O factory amp. In terms of dimensions for a replacement within the same enclosure, the enclosure cutout is about 7.25" in diameter. The recess in the enclosure where the sub basket rim sits is 9" in diameter. There's about 3.5" of depth to hit the inner extrusion points in the enclosure. If you grind them down where the sub magnet would sit, you can probably get a 4" deep sub in the factory enclosure. As for the sub, it is a basic factory sub. it's a paper cone with a foam surround mounted to a stamped basket. The magnet is about 3.75" in diameter and about 1" thick. The sub is 3.25" deep as a surface mount unit. The cut-out size matched the enclosure at about 7.25", and the total diameter of the basket is about 8.25" Pictures of the factory sub are attached.
I did some poking around and the Rockford Fosgate P3SD4-8 is a close match electrically and it will fit in the stock box. The specs for that driver for a sealed enclosure look to be close to the factory enclosure size, but this is more by the eye test than actual measurements. There are a few other DVC 4 ohm drivers that will fit without too much trouble as well, e.g., MB Quart DS1-204 400. The Rockford Unit is ever so slightly more sensitive (1 dB). I will probably pick up the Rockford Fosgate sub and replace the factory sub just for fun and to see if makes any difference. It can be done without hacking up the factory enclosure, so the factory sub can always be dropped back in. If anyone has other suggestions, please post.
you can get a decent measurement on the airspace of the enclosure by using something to fill it, then measure. water would be the best choice but when dealing with electronics it's not always advisable. i have used wine corks, packing peanuts, and on one occasion spray foam. just fill it up, them measure what you take out.
05-22-2019, 11:25 PM
Swap Out 8" Sub Driver in 2019 B&O System?
