Question about the Polk LSi15...

jon s

Does anyone know exactly where the high frequency crossover board is located in this speaker? I wanted to see if I could upgrade the caps on the ring radiator. I removed the binding plate on the back and it is connected only to the mid-low frequency crossovers. I removed the ring radiator and could not find the high frequency crossover in the upper cabinet. Removed the woofer and still no luck.

I noticed a couple of things...
1. the low frequency crossover has the components facing the binding plates with the inductors facing away from them. This leaves literally no room to upgrade the caps. That's why the schematic specifies that the components cannot exceed 1.5" in height, that's the distance between the binding plate and the crossover board and everything is jammed in between.

2. The mid-range drivers are securely held in place. After removing the six screws, the drivers would not come off. I removed the ring radiator and tried to push the drivers out from inside the cabinet and they still would not come out.

BlueFox

I do not the answers, but I have a question. How difficult was it to remove the speakers? Are the screws torqued down tight?

Face

http://www.polkaudio.com/forums/attachment.php?attachmentid=18678&d=1155780535

Everything may be on one board. You'll want to upgrade the 12 and 18 uf capacitors for the tweeter. You may be better off using something like Daytons since they aren't tremendous.

jon s

BlueFox, the speakers screws come out readily but the speakers themselves appear to be glued or stuck to the cabinet.

Face, I looked at the crossover behind the binding plate. It only has the caps for the low and mid range speakers. the 12- and 18-uf caps are not there. if you look at the schematic, it shows the binding posts for the tweeter go directly to another board somewhere. I was thinking of going with the V-caps with the LSI15 but they are quite expensive. I might opt for Hovland or stick with Sonicaps.

jon s

I just noticed that Polk shows mylar bypass caps in the tweeter crossover in their specs for the speakers...

The LSi15 features:

• Superior musical accuracy, serious theatrical impact.
• Designed for high definition formats such as SACD and DVD-Audio.
• Built-in 8" subwoofer for true full-range performance from all audio and video sources.
• Available with either natural Cherry or Ebony real wood veneer side panels.
• Mirror imaged pairs for tightly focused highs and true three-dimensional imaging with minimized room reflections: Hear what you’ve been missing!
• Cascade tapered driver array improves image focus and detail.
• Ultra high performance Ring Radiator tweeters, previously unavailable in speakers at this price, for extended frequency response, low distortion, excellent dynamics with superior detail and transparency.
• 5 ¼" Dynamic Balance drivers with Aerated Polypropylene cones for wide response and low distortion.
• Cast aluminum driver baskets resist flexing and "ringing" for ultra-tight bass and coloration-free midrange.
• Side panels are 1-1/2" thick for a totally inert enclosure - you hear all the music and only the music.
• Precise, deep bass response provided by a floor-coupled PowerPort® venting system.
• Smooth, natural midrange reproduction thanks to patented Acoustic Resonance Control technology.
• Magnetically shielded for safe placement near video monitors.
• Premium crossover components for consistent high-end sound quality.
• Mylar bypass capacitor in the high-pass crossover extends and flattens high frequency response. Hear musical details you've never heard before!
• Open architecture low diffraction grille for spacious imaging.
• Dual (bi-ampable) gold plated 5-way binding post inputs for the most secure wire connections and the most versatile wiring applications.
• Adjustable leveling feet/carpet spikes for the ultimate stability on any type of floor.

Looking at the schematic, i do not see any bypass caps connected in the high frequency crossover.

Face

Maybe the word bypass was a mistake.

Why don't you just go you all out. Mundorf M-Caps on the bottom with Mundorf Silver in Oil for the top.

jon s

I don't think that's possible. The crossover board is very small and some of the components are mounted vertically. Space is real tight at 1.5" between the binding plate and the crossover board. All the components are in between, unlike the older crossovers where the components are facing away from the binding plates.

jon s

bump...

Face

I was looking at the crossover diagram of the LSi9, it appears to have a bypass cap.

jon s

After looking in the dark, I moved the LSi15s to a lit room and took it apart again. The crossovers for the HF is piggybacked on the LF board. The problem with the LSI15 is that the crossovers have absolutely no leeway to remove it from the cabinet. The internal wiring is measured to specific lengths and i can only get the board out halfway.

I had to remove the woofer and the stuffing to get a good look at the board. I finally found the 12-uf and 18-uf caps. The easiest way to replace the caps is by going in from the woofer opening. I could solder one cap going from the binding plate opening but not the other. It's really tight in there.

I decided to hook the LSi15s back up and disconnected the RTA-12Cs... The Sonicaps really make the RTA-12Cs sing. It is more open and the highs are extended and smooth. The LSi15 sounds dull in comparison. Conversely, the LSi15 has a lot better bottom end. The bass definitely goes lower and a tad tighter.

So, i am going ahead and ordering the four Sonicaps for the LSI15 and see how that improves the sound. Maybe I will get the best of both worlds. It is known that the ring radiator is an excellent HF driver, but my guess is that the implementation in the LSi series speakers really hinders its performance with its cheaper caps in the crossovers.

One last thing... Sonicaps does not have a 18-uf cap, they have a 17-uf or a 20-uf... should I piggyback two 9-uf caps or will the 17-uf be okay? Also, what kind effect does going down on the uf-rating have on the sound vs. going up in the ratings???

Face

Be sure to take pictures.

McLoki

If you tell them you need a 18, they will charge you for a 20, but get you the caps you need at 18uf.

Let us know how it goes.

Michael

McLoki

Any update on your crossover upgrade to the LSi15's? Did you just order the caps for the tweeter circuit? Any plans for the rest of the caps (used for the cascade array and 8" woofer)?

Thanks,

Michael

jon s

I just got the Sonicaps for the tweeter circuit. The way the crossover is built, there is no room to upgrade the rest. I am hoping to work on it today, but am limited due to a recent spinal injury. I have slipped discs in the cervical and the lower lumbar region and can't really move heavy stuff.

McLoki

I have not looked at the LSi15's yet, but on the LSiC it looks like if you replace the wires from the binding posts to the circuit board, you can flip the board over and have the caps facing up. Does that look like an option on the LSi15's or no?

jon s

Success!!! i was able to remove the 12-uf and 18-uf stock caps on the LSi15s and replace them with Sonicaps of the equivalent value (I had to special order the 18-uf caps from Sonicraft as it is not a standard value).

[picture 1] Looking at the pictures below you can see the woofer after removing the foam "grille". be careful removing the grille as the cherry veneer easily chips off, as I was unlucky in finding out.

[picture 2] The second picture is of the crossover looking through the woofer opening. You can see the so-called "Power Port" tube vent on the left. Looking at the wiring going to the mid-drivers and ring radiator, you can see that they are pretty taut with no slack. The two yellow caps are the 12-uf and 18-uf that have to be replaced.

[picture 3] I was able to tilt the crossover board out so you can see the side view of it. As you can see, the components are on both sides of the circuit board. Luckily, the HF components are above the board, not sandwiched between the board and the binding plate. With so little room between the two, it would be rather difficult if not impossible to upgrade the rest of the components. It also appears that the board may be dual layered. The leads for the tweeter caps do not protrude through the other side of the board but soldered from the top, unlike the older Polk crossover boards which are soldered from the bottom.

Removing the four screws holding the crossover board to the binding plate made it easier to remove the stock caps and attaching the new ones. Make sure you measure the leads of the new ones so you do not end up with too short a lead to solder together.

The second speaker did not have any slack so i was not able to pull the crossover out at all. But by pulling on the wiring, i was able to get some slack by pulling the slack from the mid-range side of the cabinet. Be careful so you do not end up pulling the glue used to seal the cabinets out of the opening in the MDF.

[picture 4] this made it a bit difficult to solder the new caps on. I had to solder the new caps to the old leads of the stock caps. i did not want to chance removing the leads and find out that the new leads do not connect properly to the circuit board. the 12-uf cap fit easily in its proper place. but the 18-uf cap ended up "floating" as their was no easy way to hot glue it down since the cap was way to big for the space left. i am going to have to cut a piece of wood and fit it between the space and hot glue the cap to the wood and also hot glue the wood to the crossover board to prevent any resonances later. But for now...

[picture 5] another view of the modded board. It was a tight fit to get the whole thing back into the cabinet but with some thinking, it was finally done. Put the woofer back in and was all set. It was not really necessary to remove the woofer from the first speaker as there was enough slack to pull the crossover out enough to work on it. But I had to remove the second speaker woofer so I could get some slack pulled through.

And the results???

Well, there was some improvement, but nothing like upgrading the Polk Model 10Bs and the RTA-12Cs. The high end had a wee bit more extension and imaging was slightly improved but it was nothing to brag about. The highs had a bit more sound to cymbals, where the decay seemed to last a bit longer.

The imaging was slightly better with a slight improvement in focus and details. There was also a little more "air" or ambiance but again, you would really have to had listened carefully before and after the mods.

Since the crossover is at 3kHz, it may be that the ring radiator is set too high in range to affect most of the music. It may require the components for the midrange to be upgraded as well to make a more significant improvement.

Was it worth it? not sure right now... will have to break the new caps in a bit. Would i recommend it to others? Only if they want to get that last bit of sound from the music, otherwise I would have second thoughts.

Face

Sonic Caps definitely need a hundred hours or so to break in. Thanks for the write ups and pics!

Pinsongs

Hi Everyone,

I am new to the forum, I have a pair of Lsi9's and Lsi15's and was fascinated and impressed by posts about updating the crossovers caps. There are some really sharp minds here.

I love the tweeter in them but they do seem a bit held back on the impact and transients of the mid and top end. Although the 15's have more presence than the 9's (Is a Zobel circuit causing the dullness in the 9's maybe?).

john s: since this thread is about 3 months old now, how do your speakers sound since you probably have had ample break in time on your caps? I was thinking about trying the tweeter first and then maybe progressing from there.

Thank you for a great forum like this.

Eric

McLoki

Welcome to Club Polk pinsongs - there have been a few threads about upgrading the LSi crossovers recently. From what I have read so far, the 9's seem to show the most improvement....

Here is an LSi15 crossover upgrade thread.....

Here is an LSi9 upgrade thread....

Here is an LSiC thread...

Here is an LSi15 AND LSiC thread...

enjoy and have fun,

Michael

Face

I recently upgraded a pair of LSi9's with Sonic Cap and Dayton caps, and Mills resistors, and they're definitely more open and detailed up top. The speaker as a whole is also less congested now too.

Pinsongs

Thanks guys for the welcome,

I will definitely go through and read about the mods for the lsi series.

Thanks Again,

Eric