RT55 Crossover refresh

Tbone289

I refreshed the crossovers in my RTE55s last weekend, and took a bunch of pictures. I thought I'd post them here for posterity. It is worth mentioning that the 4 RT55 crossovers I own are identical in every way to the RT55i crossovers I've seen posted here, with the same cap and resistor values as the RT55i schematic. I believe that the crossover alterations mentioned here and in the schematic took place sometime during the production of the RT55, before Polk began producing the RT55i. Therefore, the only differences between the late-run RT55 and the RT55i are the tweeters and drivers.

Empty cabinet. "RTE" export versions are RT55 models with black oak veneer:



Original xover, "top", showing capacitors C2 mylar, C3 & C4 electrolytics, inductors L1 (air core) & L2 (laminate core):



Original xover, "bottom", showing wire-wound ceramic resistors R1 & R2, C1 poly:



Xover unpopulated, and showing new Mills resistors R1 & R2 relocated to the "top" of the board. This opens up the full bottom side of the board for fitment of the larger film capacitors:



16uf Solen on the LPF (C4):



2x1.5uf Clarity PX in parallel for C1, 9.0uf for C3 in the high-pass:



Fully re-assembled and ready to mount in the cabinet:

pitdogg2

Nice pictures....gulp whoops

Tbone289

pitdogg2 wrote: »

Nice pictures..

Thanks...

pitdogg2 wrote: »

..gulp whoops

?

westmassguy

Very nice, and creative!

pitdogg2

Tbone289 wrote: »

pitdogg2 wrote: »

Nice pictures..

Thanks...

pitdogg2 wrote: »

..gulp whoops

?

They do not show up for me....Gulp whoops..... In case they do for everyone else...goofy face...... in case I'm the only one in that aspect....

well we all know how well this is working for some of us.

I can't even copy it and paste to show you what I see on my end.

just my .02



Bring back ZITFUL....good grief

Tbone289

Ah, that makes sense now that you explain it. It's not working out too well for the most part, is it? I debated on whether it was worth posting at all, but decided I might as well since I took the time to take the pics. They are nice pics, BTW... Geez, the smilies don't even match what you select....

I can see the pics whether I'm logged in or out, so I'm not sure what the issue is.

Tbone289

westmassguy wrote: »

Very nice, and creative!

Thanks. I try not to be restrained by the exact location of the original components when i do these. Many times you can relocate things and use different solder points and still keep the circuit intact. Figuring out how its all going to fit is fairly entertaining for me. (I don't get out much )

westmassguy

Tbone289 wrote: »

westmassguy wrote: »

Very nice, and creative!

Thanks. I try not to be restrained by the exact location of the original components when i do these. Many times you can relocate things and use different solder points and still keep the circuit intact. Figuring out how its all going to fit is fairly entertaining for me. (I don't get out much )

That's par for the course, especially with the newer Polk crossovers. I lot is crammed on a small circuit board

Tbone289

westmassguy wrote: »

That's par for the course, especially with the newer Polk crossovers. I lot is crammed on a small circuit board

I've only worked on "RT" series so far, but I was actually very pleased when I saw the size of the board in these 55s. There's lots of room to work with compared to the smaller bookshelves like the RT3 and RT25i, or even the RT7. The RT55 has a more complex circuit though, with the 2nd-order LPF.

schwarcw

The RTi55s are a great sounding speaker! I'd be interested to hear your impressions of any sonic improvements.

Tbone289

The new components haven't had much burn-in time, but noticeable immediately was an improvement in the midrange. A slight chesty, congested quality is now gone, with better transparency and a more focused image.

msg

Hey Tbone - how are these working out for you? Great photos and nice write-up, btw!

Tbone289

Thanks!

The improvements I mentioned above still apply. I haven't noticed more improvement over time. I use the speakers for HT though, so I don't listen to them "critically". I'm satisfied with the project simply from the standpoint of increasing the quality and lifetime of the components. So any other sonic improvements are really just a bonus, IMO.

Tbone289

Sorry for the necro--just restoring the pics.

I refreshed the crossovers in my RTE55s last weekend, and took a bunch of pictures. I thought I'd post them here for posterity. It is worth mentioning that the 4 RT55 crossovers I own are identical in every way to the RT55i crossovers I've seen posted here, with the same cap and resistor values as the RT55i schematic. I believe that the crossover alterations mentioned here and in the schematic took place sometime during the production of the RT55, before Polk began producing the RT55i. Therefore, the only differences between the late-run RT55 and the RT55i are the tweeters and drivers.

Empty cabinet. "RTE" export versions are RT55 models with black oak veneer:



Original xover, "top", showing capacitors C2 mylar, C3 & C4 electrolytics, inductors L1 (air core) & L2 (laminate core):



Original xover, "bottom", showing wire-wound ceramic resistors R1 & R2, C1 poly:



Xover unpopulated, and showing new Mills resistors R1 & R2 relocated to the "top" of the board. This opens up the full bottom side of the board for fitment of the larger film capacitors:



16uf Solen on the LPF (C4):



2x1.5uf Clarity PX in parallel for C1, 9.0uf for C3 in the high-pass:



Fully re-assembled and ready to mount in the cabinet:

pitdogg2

HEY I can see those LOL

Very nice @Tbone289 one of these day that will be me doing my RTi55's

Tbone289

LOL 4 years later you finally get the satisfaction!

Tony M

I thought this was a new thread too until I saw 2014. But it's all good to those of us who have Rt55s and might want to upgrade those Crossovers too.

Tbone289

That's my hope. The post was useless without the pics, IMO.

Carbo3D

Tbone289, after doing a 5-speaker shootout with various other Polk speakers I'm really noticing my RT55is have a midrange deficiency, as you described it as "a slight chesty, congested quality". Is this common with the RT55i model? I just picked these up last month and I'm still evaluating, but I don't know if they are known as midrange vampires. What's the word on the street?

Tbone289

No, I wouldn't say that it's common for the model. But I can think of a couple of things you might keep in mind that could be contributing to the issue:

1. The RT55i is now over 20 years old. Electrolytic capacitors in the crossovers could be going out-of-spec by now.
   
2. Placement. The RT55i, being a rear-ported bass reflex loudspeaker, can sound chesty in the midrange and bloated in the midbass region if it is located too close to the front wall.

Carbo3D

Tbone289, now I know why the mids were lacking from my recently purchased pair of RT55i's: when opening up the crossovers to re-cap I discovered each speaker had the 2 ohm resistor burned out and one was missing from its circuit board! In the first photo the resistor is completely gone, while in the second it melted and reattached on its side against the 3ohm. Good grief! Luckily after replacing the resistors and recapping, the speakers now sound terrific. Granted they are "only" being used as my center channel, but believe me, voices are much more natural and defined. No more EQ needed to correct the earlier "congested" sound. Can one of you experts explain what causes a burn out like this? Is it simply overdriven by an amp?

F1nut

Clipping will do that. You'll likely find the missing resistor in the Dacron or at the bottom of the cabinet.

pitdogg2

This is the reason why we up the wattage when recapping. 5w3.5ohm would become a 10w or 12w 3.5 ohm resistor. Not much help if you're going to overdrive your receiver or amp into clipping on a continuous basis though.

Davedev07

Just found the exact same thing!

Davedev07

Davedev07

Exact same problem as above..