LSi9 Crossover Modification Project

[DarqueKnight]

Introduction

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?

Some Difficulties

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

Tools used:

100 watt soldering gun.
40 watt soldering pencil.
40 watt desoldering iron.
Cardas Quad Eutectic solder.
Electrical tape.
Measuring tape.
Hot knife.
Hot glue gun.
Vacuum desoldering tool.
Clip on soldering heat sink.
Packing tape.
20 gauge. solid core hookup wire.
Screwdriver.
Wire stripper.
Box cutter.
14" cable ties.
LSi9 schematic
Multimeter to test for electrical continuity.
LCR meter to measure resistor and capacitor values.
Small needle nose pliers.
Wire snipping tool.
Scissors.

***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
Shipping $6.95
Total $180.75

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
Shipping $16.00
Total $162.42

Total for all parts: $343.17

Modification Procedure

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.:)

[DarqueKnight]

Listening Evaluations


Figure 16. Listening evaluation of modified LSi9's. All I can say is WOW.

After the left LSi9 mod was completed, its sound was compared to the stock right LSi9 with music. The modified speaker completely "drowned out" the sound of the stock speaker. Imagine a vertical line down the center of the sound stage. It was as if the sound to the right of the vertical line just disappeared. However, when moving the balance control all the way to the right and all the way to the left, the sound pressure level meter measured the same sound level.

In addition to the much louder apparent volume, the modified left speaker had grown some BASS. This was good bass too: tight, articulate, nimble, detailed, and tactile.

The midrange and treble took on a clarity that I thought was unattainable by current Polk Audio speaker offerings. I have never before enjoyed an LSi speaker for music. Now, I was actually enjoying just listening to one LSi9 reproduce music.

With the right speaker modified and listening in proper stereo mode, every aspect of the LSi9's performance had been enhanced: sound staging, imaging, clarity, detail. I had never heard a sense of layering in the sound stage with either my LSi9's or LSi15's. Sounds were now in well defined layers front to back.

I felt kinda bad about relegating these back to dual mono HT center channel duty. However, my bad feelings were short lived once I heard the difference. The modified LSi9's added another thick layer of realism to movie soundtracks: The clear solid "thunk" of car doors closing. The subtle reverberation of a hollow core door closing. The subtle inflections in actors voices. Background sounds in the center that I had never noticed before. The modded LSi9's were also a better timber match for my modded SDA SRS front speakers.

I would go ahead and mod the LSi15's I use for surrounds, but I'll hold off because I expect to soon replace them with something prettier.

End Game


Figure 17. The usual suspects were rounded up and sent off to life imprisonment.

The accused were found guilty of grand theft of musical and soundtrack detail. Accordingly, they were given sentences of life imprisonment without chance of parole. Those culprits not sent off to prison had their voices silenced forevermore to prevent them from ever again interfering with the production of Such Good Sound.

[DarqueKnight]

Reserved for follow up.

[ben62670]

Sweet right up. I see you didn't want to risk breaking the board removing the resistors. I wasn't joking about the results of the before, and after. Night and day! Pics don't do those big caps justice. How about that glue Polk used!

[DarqueKnight]

Just another example of a wonderful speaker design crippled by mediocre crossover components.:(

[Dennis Gardner]

Nice writeup Raife, I've got to consider this for my LSi15s.

Do any speaker manufacturers use the more expensive components? I know mass production has its limits on availability of the numbers needed to fill a line and production costs must lineup with projected price points, but it seems that the drivers and cabinets are held back too many times by lesser parts.

[tugboat]

Just another example of a wonderful speaker design crippled by mediocre crossover components.:(

It's too bad they don't sell them like cars. Would be nice to get the upgrade capacitor and resistor option.

[Face]

Beautiful write up as always, thanks!

Do any speaker manufacturers use the more expensive components? I know mass production has its limits on availability of the numbers needed to fill a line and production costs must lineup with projected price points, but it seems that the drivers and cabinets are held back too many times by lesser parts.

Last weekend I auditioned the Gemme Audio Tanto, which also uses the Vifa tweeter. For a crossover, it only uses one Mundorf Silver in Oil capacitor, but for a price tag of $4,000+, it should have quality parts.

[ben62670]

Well it would be nice if they came with better XO's but the cold hard fact is that 99% of LSI owners are not into this hobby like some of us are. Also I bet 95% of LSI's are driven by receivers using substandard wires, and other components.

[tugboat]

Well it would be nice if they came with better XO's but the cold hard fact is that 99% of LSI owners are not into this hobby like some of us are. Also I bet 95% of LSI's are driven by receivers using substandard wires, and other components.

Damn the coat hangers and all-in-one York systems! When will people learn! :D:p

[ben62670]

Damn the coat hangers and all-in-one York systems! When will people learn! :D:p

Trust me they are better off not knowing;)

[DarqueKnight]

Do any speaker manufacturers use the more expensive components?

Dunlavy used Solens. I would expect Duntech speakers to use the same or some other premium brand since Duntech and Dunlavy designs are very similar. I don't know what companies such as Wilson Audio use in their crossovers.

I only know of two kit oriented speaker companies that use Sonicaps: GR Research (http://www.gr-research.com) and Bella Extreme (http://www.bellaextreme.com).

[Dennis Gardner]

I've always trusted the driver choices and cab designs of the Polk engineers and I'm sure that for the market they shoot for, the components they choose serve them well, I would just like to see a new signature line that gets the best of both worlds with Polk's purchasing/pricing power passed along to buyers again.

[heiney9]

I've always trusted the driver choices and cab designs of the Polk engineers and I'm sure that for the market they shoot for, the components they choose serve them well, I would just like to see a new signature line that gets the best of both worlds with Polk's purchasing/pricing power passed along to buyers again.

It's kind of "par" for the course with mass produced products. I have an aftermarket chip in my car and I can't for the life of me understand why the factory didn't use the fuel/timing maps the "tuners" came up with. 100 times better. Same with speakers lots and lots of variables and they are trying to be consistent and hit a very broad market.

H9

[dkg999]

Sometimes I wonder if the "custom shop" methodology that firearms manufacturers use would be viable in the audio/speaker market. The same market segments between casual buyers and hobbyist/enthusiasts exists in both the firearms and audio markets. For those of us without the time (or the preference to spend time on other things) and/or the skill, it would be great to be able to order a set of upgraded x-overs from the Polk custom shop.

[leadfoot1]

Great write up and pics. I like ready about these kind of things. I agree, a custom shop would be great. This idea is also used in golf.

[olilugo]

Great job DarqueKnight, to me is always impresive when some one takes a product and takes it to the next level. I agree with the rest of the people you should have a pimp my speaker custom service.

[McLoki]

Great write-up. I am jazzed about doing the upgrade to my LSi's again. (After reading about Jon S's results of just upgrading the HF circuit, I put it on the back burner)

Regarding the bypass cap - in most vintage crossover upgrades it is recommended to not put it back in. Did you try it with and without or is that recommendation based on something in the older crossover designs? (just curious)

Great idea to mount to 2 130uf caps to the cabinet - is there any issue with 20" leads to the caps? (my first upgrade was going to be to the LSiC - almost the same crossover as the LSi9)

I was planning on mounting the resistors as you did, and just flip the board over (screw it back to the posts upside down) to replace the caps. Would that have not worked? (only mod needed to do that would have been longer leads to the terminals) Just trying to get a feel for how to go about it before I start.

Thanks for the update - I can't wait to give it a try now.... :)

Michael

[anonymouse]

I was planning on mounting the resistors as you did, and just flip the board over (screw it back to the posts upside down) to replace the caps. Would that have not worked? (only mod needed to do that would have been longer leads to the terminals) Just trying to get a feel for how to go about it before I start.

Michael

Doubt that will work. There will be no place for the Sonicaps then. And I suspect all the caps will hit the rear end of the lower driver if you try to cram them all in there.

[McLoki]

Doubt that will work. There will be no place for the Sonicaps then. And I suspect all the caps will hit the rear end of the lower driver if you try to cram them all in there.

I don't think I am descibing it well....

Stock now resistors and inductors face up, caps face down.

I was going to replace the resistors and flip the board over so the resistors and inductors face the terminal posts and the caps face up. Then mount all the caps on the same side of the board as where they are currently mounted. With his great idea of mounting the dual 130uf caps inside the cabinet, I would also do that so they are not on the board.

There would be no more or less caps than what Darque currently has, just they would be mounted lower on the board rather than on top of the inductor. No great reason to do this, I just did not think of mounting them on the other side like he did. (effectively surface mounting them rather than through hole....)

[DarqueKnight]

Regarding the bypass cap - in most vintage crossover upgrades it is recommended to not put it back in. Did you try it with and without or is that recommendation based on something in the older crossover designs? (just curious)

What bypass cap? None of the capacitors in the LSi9 crossover are bypassed (in parallel) with a much smaller value. Are you referring to the 1 uF mylar capacitor? That cap is in parallel with the 3 ohm resistor in the tweeter circuit.

In tweeter circuits, a lower quality electrolytic or film cap is often bypassed with a higher quality film or other type (eg. silver mica) of much smaller value in order to improve the transient response. That does not seem to be the case in the LSi9 tweeter circuit.

Great idea to mount to 2 130uf caps to the cabinet - is there any issue with 20" leads to the caps? (my first upgrade was going to be to the LSiC - almost the same crossover as the LSi9)

The leads were clipped to a length of 14" prior to soldering to the board. I didn't expect any issues. It certainly sounded good. Also, 14" is shorter than the 17" to 19" length of the wires that connect the drivers and tweeter to the crossover.

I was planning on mounting the resistors as you did, and just flip the board over (screw it back to the posts upside down) to replace the caps. Would that have not worked?

The thought of doing this did not occur to me. I don't see any problem with doing this as long as there is enough clearance for the inductors.

[McLoki]

Thanks for the clarification. Wish you were closer so I could hear the results for myself....

You are correct about the bypass cap. I saw the 1uf value and assumed it was a bypass - my mistake. Thanks for setting me straight. I do not think the LSiC has this cap - wonder why and if there would be any value to adding it.....

When I opened up my LSiC - this is what I found....

[DarqueKnight]

I don't have an LSiC schematic, but it appears that the LSiC board and components are the same as the LSi9 except for the inclusion of the 1 uF capacitor in the HF section.

I used a pair of LSiC's prior to the LSi9's and the LSiC's were brighter sounding with less bass.

[GV#27]

I'm wondering how much improvemnt could be had by replacing the 1.2mh steel laminate core inductor with an air core.Although better behaved than ferrite cores ,steel laminates can also saturate at high power levels causing distortion and compression.

Air cores don't saturate so their characteristics remian stable at all power levels.The fact that it is in series with the driver that reproduces the mid band, means that using an air core"may"well bring about improvments in midrange resolution.To keep DC resistance the same as the stock coil would require an air core of 16awg. It will be substantially bigger so may need to be mounted off board.

It's not practical to replace the 9hm coil with an air core due to size and the DCR would be to high.It's at very low frequencies that laminates are best used, but in the midrange their choice is usually economical ,less copper so they are cheaper.

Just thought I'd throw the idea out there as another tweak that might bring about more improvement for the dollar than replacing the 260uf shunt cap in the woofer circuit from elecrolytic to polyprop.

[ben62670]

I did an LSIc with Dayton's. The owner did not want to spend that kinda cash for a center. I agree on the inductor. Many times I have seen that the inductor is the leading cause of distortion in XO's. If you are thinking of going this far you should build a point to point XO board. This would require removal of the woofer to get at the board, but I feel the XO board is about maxed as it is between the board itself, and the legs that support it.

[Face]

If it wasn't for the cascade woofer array, it would be easy to just mount a external two way crossover with plenty of room to play.

[knownalien]

Dark,
assuming I pay for the parts and shipping, please email me how much you would charge to do this mod to my lsi9's. thanks.

knownalien@msn.com

[DarqueKnight]

Knownalien,

I prefer not to work on other people's speakers. Forum member ben62670 does do this kind of work for very reasonable rates. Examples of some of his modification projects are posted on the forum.:)

[ben62670]

Thanks DK
Ben

[DarqueKnight]

I see you didn't want to risk breaking the board removing the resistors.

The narrow bodied mylar film caps were easy to slice off with the hot knife blade since the bead of glue was narrow and the rounded edges of the caps made it very easy to get the tip of the knife under the caps. The small 18 uF electrolytic cap was also easy to remove due to the small amount of glue used and due to the rounded edges of the capacitor end.

The resistors and the 260 uF cap were each sitting in a long puddle of hardened glue that was much wider than the tip of my hot knife blade...so they were allowed to stay.

How about that glue Polk used!

I assume Polk didn't intend for these crossovers to be worked on, either by a modder or a repair person. I assume that if a crossover component gets damaged it is more cost effective for them to just replace the whole unit rather than deal with troubleshooting and component removal and replacement. That, or they have some special tools that facilitate easy removal of the glue and components.