Modifying the crossovers of the LSi9 speakers used in my home theater system has been on my "to do" list for a long time. It just wasn't a priority because I didn't use my HT that much and I perceived that the mod would be difficult because of the near postage stamp size of the LSi9 crossover board.
Since I had taken the HT system down for reconfiguration and upgrades, I thought I might as well go ahead and get the mod done. The modification produced astonishingly good results, and this thread's assertion that my unmodified LSi speakers "sucked" was confirmed.:) I have said many times that I never liked the LSi's bass performance and that I only liked them for home theater applications. My expectations for improvement were not high because I only use the LSi9's for home theater center channel duty.
Figure 1. My LSi9's anxiously await their transformation. Ummm....how many of these
procedures have you done before?
Note 3# on the LSi9 schematic states:
"Components must be able to fit thru 2.9" x 4.0" x 0.75" mounting hole."
We can assume that the LSi series crossover board is smaller than the mounting hole. The convenience and accessibility requirements of the modder, or of the repair person, don't seem to have been considered. Parts are crammed on both sides of the circuit board and are glued to the board.:(
Figure 2. The LSi9 crossover circuit board presents some challenges to the modder...
and to the repair person.
Figure 3. Another view of the LSi9 crossover board.
Figure 4. Each LSi9 required two 130 uF film capacitors to replace the 260 uF electrolytic
capacitor. Clearly, two, or even one, of these will not fit on the board.
Tools And Costs
100 watt soldering gun.
40 watt soldering pencil.
40 watt desoldering iron.
Cardas Quad Eutectic solder.
Hot glue gun.
Vacuum desoldering tool.
Clip on soldering heat sink.
20 gauge. solid core hookup wire.
14" cable ties.
Multimeter to test for electrical continuity.
LCR meter to measure resistor and capacitor values.
Small needle nose pliers.
Wire snipping tool.
***Note: The 100 watt soldering gun was not required for its heat output, but rather for its tip size. One of the lead mounting holes for the 1 uF capacitor was located between the two inductors shown in figure 3. The tip of my 40 watt soldering pencil was too big to fit in the space between the inductors. ***
The Mills resistors and Sonicaps were purchased from Sonic Craft (www.soniccraft.com). The 18 uF Sonicaps were custom values.
Mills MRA 1 ohm resistor 2 @ $3.50 = $7.00
Mills MRA 3 ohm resistor 2 @ $3.50 = $7.00
Sonicap 1 uF 200VDC capacitor 2 @ $5.80 = $11.60
Sonicap 18 uF 200VDC capacitor 4 @ $27.25 = $109.00
Sonicap 12 uF 200VDC capacitor 2 @ $19.60 = $39.20
The Solen 130 uF caps were purchased from Parts Connexion (www.partsconnexion.com).
Solen PB Series 130 uF 400VDC capacitor 4 @ $35.81 = $143.24
Paypal Surcharge $3.18
Total for all parts: $343.17
The drivers and crossover board were removed. I left the tweeter in place, but disconnected its leads. I did not pull the crossover wiring completely out of the cabinet because I was constantly reinserting the board into the cabinet during the mod process to make sure I was leaving enough clearance for the mounting hole.
The leads of two 130 uF Solen PB series polypropylene film capacitors were soldered together to make a 260 uF capacitor. Twenty inch lengths of solid core 20 gauge hookup wire were soldered to the capacitor leads and ran out of the mounting hole. The capacitor combo was placed on the bottom of the speaker cabinet 3.5 inches from the rear edge of the driver cutout. I marked the locations for the caps with blue painters tape. A glob of hot glue was used at the points where the capacitor bodies contacted the speaker cabinet. I could have also ran a bead of hot glue along the lengths of the capacitors, but I did not want to have trouble removing the capacitors if needed.;)
Figure 5. Solen caps soldered and wired.
Figure 6. Solen cap combo ready to be (lightly) glued in place.
The circuit board was unscrewed from the binding post housing. The leads for all the capacitors and resistors were desoldered and removed from their mounting holes. The 1 uF, 12 uF, and 18 uF film capacitors and the 18 uf electrolytic capacitor were removed from the board. I used a hot knife to gently scrape them off the board. The hot knife was also used to clean the board of glue residue. The 260 uF electrolytic capacitor and 1 ohm and 3 ohm resistors were left in place because it would have been very difficult to remove them due to the large amount of glue securing them to the board.
The 1 uF Sonicap was inserted in the same location as the stock 1 uF mylar cap. The 1 uF Sonicap was positioned so that it did not extend beyond the edge of the board. The 1 uF Sonicap was just the right size to fit in the space between the board and the binding post housing. On the left speaker, I had to slightly bend the lower binding post wire connection tabs away from the Sonicap. After the installation of the 1 uF Sonicap, the board was screwed back to the binding post housing. This made it easier to handle during the rest of the mod process.
The leads for the two resistors were clipped close to the resistor bodies. The ends of the 1 ohm resistor were covered in electrical tape since they would be close to the leads of the new components.
The upper lead of the 1 ohm Mills resistor was covered in 1/16th" heat shrink tubing to insulate it from the lead from the 18 uF Sonicap that would go between it and the body of the stock 1 ohm resistor.
Figure 7. Placement of the 3 ohm (left) and 1 ohm Mills resistors.
Figure 8. Placement of the high frequency 18 uf Sonicap.
Figure 9. Lead extension for the high frequency 18 uF Sonicap.
The upper lead for the high frequency section 18 uF Sonicap was insulated in 1/16th" shrink wrap. An extension was made of 20 gauge solid core hookup wire to allow this cap to be oriented parallel and on top of the 1 ohm stock resistor.
The 18 uF low frequency section Sonicap was oriented next to the high frequency 18 uF Sonicap and hookup wire was run from its leads to the board.
Figure 10. Low frequency 18 uF Sonicap to the left of the high frequency 18 uF Sonicap.
Figure 11. Some people might want to mount the Solens on top
of the other film caps. Think again. Stress fractures on the board
might occur, in addition to increased component vibration.
Figure 12. The leads for the Solen cap combo are ready to be soldered to the board.
Figure 13. The 18 uF caps were moved out of the way and the leads from the Solen
cap combo were soldered into their mounting holes next to the large inductor.
Figure 14. Side view of finished crossover secured with packing tape and cable ties.
Figure 15. End view of finished crossover.
The left speaker was done first and took 4 hours. The right speaker only took 1.5 hours since I knew what I was doing by then.:)