Modifications to the RTA 15TL

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.

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!

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

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?

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

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.

mrwirez wrote: »

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.

I think you are going to get a lot of recommendations to swap the SL3000s out for the latest generation RD0198-1s as your first upgrade. I did this a few months ago now. I honestly didn't notice a very significant difference (maybe a little less sizzle on the very top end), but I also upgraded my amp around the same time, so it is hard to know for sure. I only say all that to offer up one of my SL3000s if you want to stay with those to get back up and running as you consider mods. You can have either the original February 1992 dated one I have, or the August 1996 warranty replacement. Just cover shipping cost for me via PP F&F. The two do look different. The earlier one has a "blacker" dome, whereas the replacement is more silver in color. I'll post photos if you're interested in going that route.

As far as all the other possible mods, I'll let the experts here chime in. Oddly, I was just getting ready to start a thread on what is going on with the refresh of my own RTA-15TLs which I also purchased new, when I saw your post. Mine's going to be a pretty minimalist approach compared to what you see in this thread and others here, but the recommendation to let everyone know at least your general location is a good one. I ran into the same thing with the fellow you are talking about, but ended up getting help from a member about 30 miles away from me. The folks on here have a ton of experience and knowledge and are more than willing to help.

skrol wrote: »

pitdogg2 wrote: »

The SL2000 tweeters AFAIK were never used in the RTA15tl (there was never a RTA15T). They would have came with the SL3000 tweeters.

Welcome to the forum!

True. The RTA15TL only came from Polk with the SL3000. Some early 15's were labled RTA15T but they had the SL3000.

Even my boxes are labeled RTA15t. They are tl. Upgraded the tweeters is a bonus & worth every penny

Boston; I saw that on the drawings too, along with a hand written note that later models didnt get the poly switch.
Ordered the RD0198-1 pair last night, deciding on capacitor and resister brands.

Finally got some time to work on this project. Cleaning oiling is done. Got to the bottom of an issue with my 2220B and started listening to these.
Very happy with the condition of the bass drivers, clean all the way down to the known tubby Polk bottom end. Fortunately my room allows me to space them some from the back wall.
Listened with the wrong tweeters first to get a baseline. Swapped in the RD0's. I pretty much noted the same as the OP here as they were even more edgy in the upper mid range.
So then I sat and mulled over replacing the inductors feeding the woofers.
Had some issue with the caps being sold out so spent some time on that too.
In the end I decided to replace the woofer inductors and got all the crossover parts ordered.
Popped in Cosmic Messenger to listen to the first track only.....ended up listening to 4.
The bass on that one really meshed well on these speakers..
Wondering about these old caps, the poly switches and my hearing....I feel there is little above 8 or 10k coming out of these..
Now that old Marantz with 20 WPC drove these things to "Call the Police" levels with ease.

I will post up some more thoughts after I get a listen with the updated crossover.

Cheers!