87 PU SC Passenger Side Sub Woofer Box Fix
May 29, 2017 | 01:24 PM
#1
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Joined: Mar 2017
Posts: 14
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87 PU SC Passenger Side Sub Woofer Box Fix
My PU came with a dealership option sound system upgrade that cost $280 in 1987. This included a nicer digital stereo with decent radio features, a tape player, upgraded side speakers, and a sub woofer box behind the passenger seat.
When I got the truck that sub was blown. The bass dial on the stereo, when turned all the way down, allowed it to transmit almost no power there so the rattle wasn't heard. I wanted to rebuild the box but it is a discontinued part. Thus I searched for speaker drivers to drop in to hope that would be a fix. I found one speaker driver that was spec'd as a true 'sub woofer' after a lot of searching. The diameter is 4" so the options are very limited. I also needed the bolt patter to match up to make it work. The one dimension I couldn't control was the depth of the speaker. The dept came out to about 16-17mm more than the original part.
I decided the best path to take would be designing and printing a part to go in between the main housing and the back panel that comes off after removing 6 bolts. I designed the part in CAD and uploaded it to a site that prints the part and ships it. Printing was $10 and shipping was $6 or so. It came in about 4 days.
To my surprise I had measured everything well enough that it just snapped on. I cut some gasket out of Fel-Pro blue for the seal between the part I printed and the housing as well as between the speaker and the housing. Initially I had some vibration, which I believe was due to an imperfect seal (as this is a sealed speaker) but for whatever reason it seems to have worn into the gasket and made a better seal because it no longer vibrates, at least that I can hear.
The difference in quality of sound is amazing. The modern 4" sub woofer must be superior to old ones because in that tiny little cabin the bass is tremendous. I leave the bass at half power because otherwise it gets out of balance with the rest of the sound in most songs. The only issue I've had is a hickup in the output once or twice, I think the components on the board are getting loose. The board components - choke, caps, etc. are not potted or mechanically stabilized. They are not so large but I think with 30 years of truck vibes it takes a toll. For the most part it works at 100%, however.
When I got the truck that sub was blown. The bass dial on the stereo, when turned all the way down, allowed it to transmit almost no power there so the rattle wasn't heard. I wanted to rebuild the box but it is a discontinued part. Thus I searched for speaker drivers to drop in to hope that would be a fix. I found one speaker driver that was spec'd as a true 'sub woofer' after a lot of searching. The diameter is 4" so the options are very limited. I also needed the bolt patter to match up to make it work. The one dimension I couldn't control was the depth of the speaker. The dept came out to about 16-17mm more than the original part.
I decided the best path to take would be designing and printing a part to go in between the main housing and the back panel that comes off after removing 6 bolts. I designed the part in CAD and uploaded it to a site that prints the part and ships it. Printing was $10 and shipping was $6 or so. It came in about 4 days.
To my surprise I had measured everything well enough that it just snapped on. I cut some gasket out of Fel-Pro blue for the seal between the part I printed and the housing as well as between the speaker and the housing. Initially I had some vibration, which I believe was due to an imperfect seal (as this is a sealed speaker) but for whatever reason it seems to have worn into the gasket and made a better seal because it no longer vibrates, at least that I can hear.
The difference in quality of sound is amazing. The modern 4" sub woofer must be superior to old ones because in that tiny little cabin the bass is tremendous. I leave the bass at half power because otherwise it gets out of balance with the rest of the sound in most songs. The only issue I've had is a hickup in the output once or twice, I think the components on the board are getting loose. The board components - choke, caps, etc. are not potted or mechanically stabilized. They are not so large but I think with 30 years of truck vibes it takes a toll. For the most part it works at 100%, however.
May 31, 2017 | 12:17 PM
#2
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Joined: Feb 2015
Posts: 858
Likes: 13
From: Mogadore, Ohio
Nice job. The replacement woofer having a much larger magnet than original and deepening the cabinet a little helped you get a bigger sound from that small enclosure.
What kind of dog you got?
What kind of dog you got?
May 31, 2017 | 04:43 PM
#5
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Joined: Jun 2013
Posts: 3,112
Likes: 582
From: Portland, Oregon, USA
Wait, those 4" speakers were supposed to be subwoofers? I thought they were just regular full range speakers. You learn something new everyday!
I like your fix. It looks solid! I bet it sounds so much better!
I like your fix. It looks solid! I bet it sounds so much better!
