Modifications to the RTA 15TL

F1nut

Sorry, there are people here with more experience using caps you haven't used that know how much better they are. Since you've never tried any your comments mean nothing.

pitdogg2

leesonic wrote: »

I knew there would be people on here that would whine and moan if I didn't use the Solen caps. Usually, I would have used PEX caps from Erse Audio, or Dayton caps. I've done plenty of crossover restorations using these caps, and have had no complaints, both on my own stuff and speakers I've restored for others. You can see my threads over on AudioKarma, same user ID as this one.

Caps are a subject that people have strong but very misguided opinions on. Some people with unlimited funds prefer caps with 24ct gold foil, using the finest snake oil as the electrolyte, soaked in pure silk sheets from free range (not battery) silkworms, and hand-rolled on the thighs of dusky maidens. Me, I've already said what I use. The fact is, a Dayton, Erse, or Solen cap is going to be miles better than a 20 year old electrolytic, so don't lose any sleep over it, just listen to the music.

I asked that you report back only because I would of liked your impression. I've used Solen in the low pass but in the high pass they for me can be very fatiguing and or shrill.
Forgive me for trying to get another point of view.

Sea

Good Morning All. After spending several years accumulating and restoring Carver Amazings, I have found mayself back dabbling with Polks again. I still think my fully modded SDA 1C are the best speakers I own,

Anyway, I have just acquired a pair 15tl's in great shape from the original owner. I am trying to decide whter to go down this update path. Great work by Decato.

My first question for all of the experts here is are these supposed sealed cabinets like my RTA 12c's and other models with passives. I do not get any movement of the passive cones when I press on the drivers.

Sea

Thank you to decato for his great work.

I have just acquired a pair of 15tl's. Quick,question. I assume these are supposed to be sealed cabinets since they have passive radiators. I do not get the expected defection of the drivers when I press and hold one of the cones.

FestYboy

You shouldn't press on the driver, you SHOULD press on the passive. A single MW won't displace enough air to significantly move the passive. Think of it like a hydraulic circuit.

pitdogg2

Sea wrote: »

I do not get any movement of the passive cones when I press on the drivers.

You should be pushing the passive not the drivers. Since these have 2 passives it might not work the same

Sea

Yes. I found a post suggesting to push on both passives at the same time. My enclosures are sealed well. Thanks.

pitdogg2

Excellent

Sea

My postings were delayed for some reason. Maybe because it has been so long since I posted. I think the meantime I found d a post somewhere suggesting that both the front and rear passive should be pressed at the same time. The cabinet is indeed sealed. Thanks.

Sea

My postings were delayed for some reason. Maybe because it has been so long since I posted. I think the meantime I found d a post somewhere suggesting that both the front and rear passive should be pressed at the same time. The cabinet is indeed sealed. Thanks.

leesonic

I did the passive radiator modification today, as described on page one of this thread. Basically, this involves removing the SW104 passive radiator with the most weight on it (called "low resonance" by Polk), swapping the SW100 front "high resonance" one to the back, and using an SW105 passive in the front.

Here are some pictures of the passive radiators. The SW105 has a small mass in the center, the SW100 has a larger mass, and the SW104 has two of these masses stacked on top of each other. There is no real difference otherwise in their construction when viewed from the rear.





Here is one of them next to my Dayton/Advent Frankenspeakers.



Regarding my comment above about people complaining over what caps or resistors I used. It wasn't intended to upset or offend anyone. I too have done a lot of crossover work in my time, I've been into this hobby since I was probably around 10 or 11. Other kids used to read comic books, I used to read HiFi magazines. The fact is, pretty much any cap would be an improvement over 30+ year old electrolytics that have dried up. Everyone has their favourite flavour of caps, each to their own. It would be a dull old World if we all liked the same. The other fact is, I'm pushing 50 now, so I probably couldn't hear the difference between Mills and Dayton resistors. The mind is a very strange and peculiar thing, if it's telling us that one cap, inductor, or resistor sounds better than another one, we can't argue with that.

We're all cool, right? Like Sir Richard Starkey AKA Ringo Starr would say : "Peace and love, peace and love".

Lee.

leesonic

Who? Fluffy?

He's been off his food a little bit lately. He tries to drink milk, but it goes right through him.

tonyp063

At least you don't have to worry about shedding.

Ogrebelle

Hi, I debated posting this here v. posting it as a new topic. I opted for here but if you guys think it should be a new topic feel free to let me know and I can move it.

Question. Specifically regarding this Decato Mod (but could be a general discussion as well), what result would you get from using 16 awg copper foil inductors over the 16 awg wire-wound air core inductors? Also, what would be the result of using either a 1.70 mH and/or a 1.80mH inductors (readily available stock sizes) over the seemingly oddball 1.75 mH inductors?

Same questions relating to the 19 awg 0.22 mH inductors...

As I said these particular questions are specific to the Decato Mod but I am very interested in this as a general discussion on the topic as well. I would just like to better understand the effects of these changes in any instance (changes in awg, mH, wire v. foil construction, etc.).

Thanks for your perspectives and experience.

Ogrebelle

I just moved this to a new topic "Crossover Questions (Inductors)" in Vintage Speakers hoping to get more views and comments. Things seem to happen pretty quickly on this forum so the fact that no one has chimed in after 14 hours or so I thought it best to move it. In hindsight I should have just started there anyway. Please go there to comment...

Link:
http://forum.polkaudio.com/discussion/182247/crossover-questions-inductors#latest

AlanH212

Hi, All

I bought my RTA 15TLs back when they first came out and about fifteen years later, looked into whatever it might take to maintain and improve them. That's when I found this forum, which gave me a lot of great advice. I'm here now after all this time to thank everyone, especially decato, F1Nut, and VR3.

Getting the silk dome tweeters was a no-brainer, and I figured that I'd have new crossovers built for me using decato's mod, but didn't follow through back then. When I moved from NYC to Tucson ten years ago, I revisted this thread, and got in touch with VR3 to do the mod. That was nine years ago, and I think it was his first RTA 15 mod. He did a great job and here's his thread on it:

https://forum.polkaudio.com/discussion/122245/rta15tl-mod-thread)

I sent him the crossovers with the internal wiring, we discussed the design and agreed on the parts (including new wire and binding posts). He put them together really well, point-to-point, and they fit perfectly. I put the cabinets on new brass points, a bit taller in front. Put some banana plugs on my old 12-gauge wires, and I was set. They sounded great immediately, and burned in very nicely.

I started out as a classical musician, became a music critic and record reviewer back in the days of LPs, did a lot of recording back in the days of 1/2" tape, moved on to make a decent living at last (programming, technology, banking, finance) so I could afford nice things like the Polks, and finally "retired" as the COO of an art museum. I've done recording all along the way (classical and jazz) and am fairly demanding when it comes to sound.

With the modified crossovers, the RTA 15s are rich and detailed, nice and even bottom to top, nothing missing, strained, booming, or shrill. Very natural and revealing without sounding clinical, they suit my ears and the music I listen to exceptionally well. I figured it was time to come back here just to say how pleased I am with the great sound I continue to get out of these speakers, with all of your help. Thank you!

abebar

This is probably a stupid question.... But do the speakers remain at 8 ohms after the crossover mods? I'm assuming the answer is yes.

I just performed the modification on one speaker, and it is now reading 4 ohms across the input terminals.

pitdogg2

If just switching caps and resistors yes it should stay at 6-8 ohms whatever the factory value was. If you switched inductors then yes it can go down.

abebar

I replaced the L1 inductor in the HP circuit from the 0.4 to the 0.22 as indicated in the provided schematic. I was still expecting the same overall impedence though. I don't see any shorts or opens. All solder joints appear clean and intact. Not sure what to do next here...maybe just hook it up to an amp with good internal protection and give it a listen?

F1nut

abebar wrote: »

This is probably a stupid question.... But do the speakers remain at 8 ohms after the crossover mods? I'm assuming the answer is yes.

I just performed the modification on one speaker, and it is now reading 4 ohms across the input terminals.

You are measuring resistance not impedance. You cannot obtain the nominal impedance with a DVM.

abebar

Good point F1nut.

I'm going to finish the other crossover and measure that one. Assuming they're both consistent, I'll hook them up and see if they sound full range. I have a old Denon AVR 2500 that has good over current protection and I also don't care about it. That will be a quick and easy way to find out if I wired something incorrectly. Wish me luck 🤞😃

SeleniumFalcon

Another hint: if the speaker isn't producing sound, during the measurement, you're not measuring impedance.

abebar

Its sounds great! I hooked up both modified and original and listened to them for about an hour. The stock configuration had WAY more midrange and harshness. The modified speaker sounded natural and balanced. I can't wait to finish the other one and position them semi-permanently.

False alarm. All is well 🙂

decato

I'm glad to hear that these mods are still bringing joy to listeners!

boston1450

They sound incredible on vinyl too

abebar

Okay... Another question. I have been enjoying these reborn speakers for the past few weeks as my primary 2-channel system and I realized that I did not reverse the polarity on the 198 tweeters. Can anyone explain to me the purpose of that phase inversion? I can't imagine these sounding better than they currently do... What am I missing?

decato

abebar wrote: »

Can anyone explain to me the purpose of that phase inversion? I can't imagine these sounding better than they currently do... What am I missing?

A second-order crossover will put the four woofers' and single tweeter's signals out of phase with one another, causing a dip in the frequency response centered on the crossover frequency. By inverting the polarity of the tweeter, the response of the woofers and tweeter will be summative. You should take the time to fix your crossover. You'll notice better driver integration and a more cohesive midrange. Let me know how it works out.

engie490

Here's a picture of what changing the polarity of the tweeter can do:

abebar

Wow, okay. That freq response improvement is more that I would have ever guessed. I'll crimp new connectors on today and flip them. Thanks guys. I'll post my thoughts afterwards. I've been listening to them at least an hour per day for a month, so any significant change should be noticable.

mrwirez

Hello Polkies! Long time lurker. I'm looking for someone that rebuilds the RTA-15TLs. I don't know the first thing about it. I bought the speakers new in 1991 and they sat for the last 5 years as we've been busy. I recently brought them up and they sounded ok. Then I blew an SL3000 Tweeter. So it's time for an upgrade. I contacted the fellow that used to do them on from here and eBay, but no longer does that work. Any ideas? Thanks.