I picked up an old Bose LSPS subwoofer module with a blown amplifier from my uncle yesterday. My idea was to remove the blown amplifier and convert it into a simple subwoofer for my daughter to use in her car. It looks like a simple two-driver vented box, but when I removed one of the drivers and the amplifier, the internals weren't just chamber and a vent like I expected. Instead, it looks like each driver is mounted in folded tube that terminates in a vent.
Anyone know what's going on inside one of these things? I was first thinking it's probably an offset-driver TL alignment, but one of the drivers is located near the end of the folded tube, and the tube looks like it has to traverse the length of the box at least twice before it meets the other driver. I've searched online but haven't turned up anything yet.
Another thing - the drivers seem to be wired in parallel and present a combined impedance that drops as low as 1.3 ohms (measured using my DATS). The curve looks like the classic double-peak of a vented alignment, but the lower peak is HEAVILY damped. The dip between the two peaks doesn't appear to be that damped though, which is what I would have expected if the heavy damping of the lower peak was caused by a fully-stuffed enclosure.
Later on today I'm going to take it apart a bit further to see if I can figure out what's going on inside it. One driver is easy to remove. The other, not so much ...
Anyone know what's going on inside one of these things? I was first thinking it's probably an offset-driver TL alignment, but one of the drivers is located near the end of the folded tube, and the tube looks like it has to traverse the length of the box at least twice before it meets the other driver. I've searched online but haven't turned up anything yet.
Another thing - the drivers seem to be wired in parallel and present a combined impedance that drops as low as 1.3 ohms (measured using my DATS). The curve looks like the classic double-peak of a vented alignment, but the lower peak is HEAVILY damped. The dip between the two peaks doesn't appear to be that damped though, which is what I would have expected if the heavy damping of the lower peak was caused by a fully-stuffed enclosure.
Later on today I'm going to take it apart a bit further to see if I can figure out what's going on inside it. One driver is easy to remove. The other, not so much ...
That's the model, yes.
This is what the measured impedance looks like. Note the significantly damped lower peak. Looks like I was incorrect about the dip at Fb at well - it also suggests that there's lots of stuffing in the enclosure. Didn't expect to see that in a Bose bass module.
This is what the measured impedance looks like. Note the significantly damped lower peak. Looks like I was incorrect about the dip at Fb at well - it also suggests that there's lots of stuffing in the enclosure. Didn't expect to see that in a Bose bass module.
It look to me the lower peak is significate smaller in amplitude than higher peak because of the very low 45 Hz vent (de)tuning frequency of the bass module, which is rather low for those 5-inch "subwoofer" drivers used by Bose. Apparently some active equalization is helping here.