Refreshing my RTA 15TLs

bcwsrt

A little back-story, first ...

I've had these speakers since new (1992) and bought a Denon DRA-1052RA receiver at the same time. I moved around quite a bit then as I had just started my career, but had this same system (along with Sony CDP-508ES D CD player and a couple different cassette decks and a crap turntable, the brand which I will save myself the embarrassment of mentioning lol) in four different homes in the first 15 years I owned it.

Anywhere it was, I always thought the sound was a little harsh and chalked it up to the speakers and/or the "digital" sound of CDs.

The past 15 years, the speakers (and the rest of the equipment) have been in their factory boxes, due to a combination of working too many hours and not having a room to set it up in at the previous house.

I retired two years ago and late last year, I got to wanting to unload some stuff in the basement after we had some minor flooding down there and also to prepare for an eventual move to Tennessee. The stereo equipment was taking up a lot of space, particularly the 15s, so I put them on FB Marketplace. I soon found out that even minty ones don't command a decent dollar. So, instead of using them for firewood or helping the garbage man load them in the truck one Monday morning, I hooked them back up to the Denon ... and proceeded to rediscover how much I liked listening to music through loudspeakers instead of the earbuds I'd become accustomed to.

But, that harsh sound I remembered was still there. So, @charley96 on here recommended doing the RD0198-1 tweeter upgrade. Ah, OK, not a big difference to my ears. But, then he let me borrow his Rogue Audio Cronus Magnum integrated tube amp and it's been game on ever since. The tubes and maybe equally, or more importantly, the current, of the Cronus totally transformed the sound of the 30 year-old 15s. After about 3 or 4 weeks of auditioning his, I got a new CM3 and have been making continual tweaks with cables, speaker placement, room treatments and listening to more music in the past two months than I probably have in the past two years.

I feel like I'm getting more out of the two channel experience now than I may have 30 years ago and plan on a reboot of my entire system over time. Next on that journey is a refresh of the 15s.

From some of my other posts looking for crossover rebuild help here, @pitdogg2 reached out asking if I wanted his help. I was more than happy to accept his offer and we connected yesterday for the first time. He took a look inside to make sure there were no surprises (there was a small one that he cleared up with the factory schematic) and we discussed the path forward.

This may sound a little anti-climatic with the other SDA-1C upgrade thread that's going on, but here's the list:

1. Sonicap film capacitors in the factory values (1 12uF and 2 20 uF, each)
2. Mills resistors in the factor value (1 2 ohm each)
3. Cardas binding posts (waiting for Ivan to confirm, but I think we are probably looking at the CCGR S based on how I remember him describing them yesterday)
4. J-B Weld MW magnets
5. Dynamat MW and PR baskets

I'm just after a basic "renewing" of these speakers with basic, proven mods and not necessarily wanting to tweak or change their "voice" or sound signature, which I've come to enjoy all over again. So, this thread shouldn't take too many crazy twists or turns or last a year, but please feel free to comment (even about hot dogs, buffalo chicken pizza or, hey, TV dinners if you'd like). Just enjoying getting back into the hobby after a long absence, building my system back out with new and refreshed parts/pieces/components and enjoying the music again along the way. And ... I appreciate all the help from the forum members here, the one I've known for four decades, the one I met yesterday for the first time and all the others I've spent countless hours reading their posts and learning from. These vintage Polk speakers may not be worth a lot of dough, but it's great that there are people who still enjoy them and are willing to lend a hand to others to keep them performing their best.

I'm enjoying exercising them in stock form one last time right now before pulling the MWs tomorrow for the J-B Weld process. Hopefully have them buttoned back up by next weekend to listen again and see what the Dynamat did. Parts will be on order sometime soon and then will reconnect with Ivan for the crossover refresh once the parts are on-hand.

A couple pics of how things currently look below, to get things started. I was surprised how small the factory crossover is after seeing some monster rebuilt ones on here.

xschop

With new caps and silk domes, you're 90% on the path to bliss.

plastic_avatar

Well written, @bcwsrt

This is the kind of thing I love to read.

I'm incredibly excited for you! And maybe just a little envious of that awesome listening room...

Please keep posting pictures and telling us everything you care to share.

And, other than saying 'I enjoyed your opener, can't wait for more, and would love to hear your continued thoughts on that tube amp.':

What's your favorite food?

txcoastal1

https://youtu.be/XfR9iY5y94s
vegemite sandwich

bcwsrt

plastic_avatar wrote: »

Well written, @bcwsrt

This is the kind of thing I love to read.

I'm incredibly excited for you! And maybe just a little envious of that awesome listening room...

Please keep posting pictures and telling us everything you care to share.

And, other than saying 'I enjoyed your opener, can't wait for more, and would love to hear your continued thoughts on that tube amp.':

What's your favorite food?

Thanks, p_a and I’m not gonna lie, I’ve enjoyed your thread, criticisms, onion rings and all.

It’s actually really a listening “corner.” The left side and rear are open to basically the rest of the basement. Also, the lower part of the ceiling you can see on the left is only 7ft vs 8 ft on the right. Far from ideal. So, to combat the deficiencies in the listening area, I decided to give room treatments a try. First time experiment with those, but it worked! Pretty noticeable improvement in stereo separation, imaging and depth and width of soundstage. I liken it to being more like listening through headphones in that regard. Plus, the panels on the front wall really tamed the negative effects of the rear facing PRs on the 15. The bass from the listening position is tighter and more pronounced. Room treatments are no joke for improving your system’s performance. I may add some “clouds” on the ceiling and possibly some corner treatments later, but for now, I’m pretty happy with the changes just these six panels have made. GIK Accoustics products, BTW.

My favorites are BBQ and seafood, not necessarily in that order.

On the tube amp … I will gather my thoughts on the Cronus and report back. I took copious notes as I was auditioning the borrowed unit. In short, it was an eye-opening, shocking and at times a somewhat surreal experience hearing these speakers sound like they never had before. I had no idea that what I thought was a totally competent receiver, wasn’t, as far as these speakers are concerned.

bcwsrt

xschop wrote: »

With new caps and silk domes, you're 90% on the path to bliss.

Excellent, and what I was hoping for! I'm looking forward to the process and seeing (and hearing, of course!) what happens.

skrol

I had similar experience with my RTA-11TL's that also had the SL-3000 tweeters. They are much smoother with the RD0198 and XO upgrades. They do improve more with some run time.

I kind of got lost in the thread... Are you still using the Denon DRA-1025R (1052) to power them? I had been using a Denon DRA-825R to power my 11's for many years. Then I had a chance to grab a Denon DRA-835R. In spite of the slight wattage rating difference, the 835 was night and day better. The 835 is more of a dual mono design and drives more current. Bass was much tighter, cleaner highs and better imaging. I later upgraded to a Parasound pre and amp. Now the RTA-11TL's are serving in my HT, driven nicely by a Marantz SR-7010.

The RTA-11TL seem fairly easy to drive but I think the 15TL is a bit more challenging. More current drive is always a plus.

bcwsrt

Oh nuts, you're right, I had some finger slippage there, sorry. A DRA-1025RA is what it is (was). But since November, I've been using a Rogue Audio Cronus Magnum III. I've kind of forgotten the various Denon models of the period, but what you describe with going to the 835 is very similar to what I've encountered with the Rogue tube amp. I had read about the benefits of more current, but never experienced it until a couple months ago. When you see the 135 watts the 1025 is rated at, you think you are good-to-go, but clearly that's not the whole story. The Cronus is only rated at 100 wpc, yet sounds leaps and bounds better.

heiney9

With just some simple refreshing, RD0 tweeters and good caps/resistors/driver treatments you'll be amazed at the transformation. The Rogue is an excellent piece of gear and it looks like the final step of room treatments is already done.

Once you get all done, then you should explore rolling some old stock tubes; a whole other adventure that's immensely fun and very rewarding.

H9

bcwsrt

I’ve still got the old Denon to burn the crossovers in when the time comes. Gonna try to resist the urge to listen to them at all during the burn-in so I’m not distracted by changes in the sound related to that.

The amp and room treatments were pretty substantial improvements. I’m actually expecting the speaker results to be more subtle, but maybe I’ll be pleasantly surprised.

Ivan gave me some tube recommendations awhile back, which I’ve already been enjoying the results of.

This has been one of the best central Illinois winters I’ve had in quite awhile playing around with all this stuff. 👍

bcwsrt

Just to correct the parts list in my above original post, it’s actually (2) 12 uF and (1) 20 uF capacitors, each, not the other way around.

1 Vishay Mills 2 ohm MRA-12 resistor, per.

And we went with the CCGG S Cardas posts.

skrol

The burn-in was interesting with my RTA-11TL and Monitor 5B. At first they sounded harsh and grainy and I was initially disappointed. But within a few hours you could hear them smooth out. I thought it was my ear/brain adapting and walked away for a while to reset. It was real. After that it was much more gradual.

bcwsrt

I didn’t get as far as I’d hoped today fighting with the majority of the spade connectors on the drivers. There’s no visible corrosion that I can see, but man, those things were extremely stubborn. Did get parts ordered, too, though.

A question about the stock wiring harness … it seems a little cheesy to me, but I don’t see where a lot of the folks here replace it with any heavier gauge wiring. Some have, yes, but it doesn’t seem all that common.

Is the general consensus that it is adequate? I’m not going to mess with it one way or another, at least for the time-being. More just a curiosity.

bcwsrt

Got half the J-B Weld done. Will finish the bottom joint (top in this pic) tomorrow afternoon.

Kinda surprised at the 7 week range in dates of the MWs. Most are mid-late March. The February one is definitely an outlier, though the one factory SL3000 I still have is February 1992, also.

bcwsrt

All the J-B Weld-ing is done and the Dynamat is on. Well, actually, I used a product called Sound Assassin that I had leftover from covering the floorboard and rear wheel wells in my Jeep a couple years ago. Didn't take much more than a half sheet to do all 8 MWs and the 4 PRs. I didn't go quite as crazy with it as some.




The PRs have some kind of cardboard glued to the bottoms of the baskets, so I only did the spokes. I was surprised to see that. I thought all the Dynamatted PRs I saw here had most of the basket covered with it.



Back up and listening this evening. Jury is still out on any audible effects of the Dynamat-like product, but made sense to do it while everything was apart. I definitely have more piece of mind with the J-B Weld on the MWs, even though to describe the process of doing it as "tedious" is a gross understatement.

Tracking says the parts will be delivered from Sonic Craft with tomorrow's mail.👍

plastic_avatar

[chuckles]

You are correct. Tedious is inadequate as an adjective. We should find more words to tack on to help warn people.

- Easy, but time-consuming and tedious. Monotonous and sometimes soul-crushing if you think it'll go fast. The more drivers, the less you'll enjoy yourself. -

I hated that part so much on my 1C, I don't know that I have it in me to go back and do the same thing to my Monitor 12.

However, welcome to the club! We're glad you made it through. Have a seat and take a breather

bcwsrt

“Soul-crushing” gets closer than I could have. Lol Dynamatting actually seemed thought-provoking and fun, by comparison.

xschop

Looking on the bright side, your magnets appear to be concentric from factory. Good job.

Gardenstater

Nice work. I would've considered removal of the cardboard on PR's and replacement with Dynamat. Gotta be more effective than the cardboard at damping ringing.

bcwsrt

Thank you. I did give that a passing thought. But I just wanted to be done! 😂 They’re so easy to yank, maybe I’ll do it after I recover. 😀

Gardenstater

bcwsrt wrote: »

Thank you. I did give that a passing thought. But I just wanted to be done! 😂 They’re so easy to yank, maybe I’ll do it after I recover. 😀

Yep by all means don't "go crazy" but on the other hand, if ya don't gots the thwack, somethin's outa whack

PS: I would also relocate those stickers on the PRs, maybe to the basket between windows and flange, and cover the entire spoke.

bcwsrt

Thanks, again. The feedback is appreciated and was one of the main reasons for starting the thread. Just as long as you promise all that won’t “suck the life” outta anything. 😋

Parts are here!

Gardenstater

Sweet. I promise you the diaphragms only want to be responding to the electrical signal (and acoustic backwave in the case of the PRs) and not a vibrating stamped steel basket.

bcwsrt

If I'm thinking about it right, it seems like the PRs wold be more susceptible to resonances since the baskets are larger. Could be why the cardboard material is on there from the factory.

I'd imagine it takes some volume for the benefits of the Dynamat to show up, though? I should get a better chance to see what's up with what I've done to this point on Sunday when Mrs. srt is gone for awhile.

Gardenstater

I did mine in two phases. First the MWs, then a couple weeks later the PRs. Got the most benefit from the MWs but definitely improvement with PRs too. Lets not forget that the MWs have a sensitive moving voice coil (to vibrations) involved. I won't describe what it sounded like to not prejudice you further

bcwsrt

I like that answer!

Gardenstater

Also, when you look at the product you used on edge, does it look like a solid butyl rubber or is it more like a butyl rubber foam material. I would be leery of products that claim to be both thermal insulators *and* road noise insulators. Another issue could be the thickness of the foil. Yeah making that thin allows greater flexibility around contours when installing in a jeep but the way this stuff works to dampen mechanical vibration modes is by the constrained layer dampening and the thickness of the foil matters.

bcwsrt

Well, when I was searching the various Dynamat threads, some alternates were discussed and it sounded to me like pretty much any similar product would be fine. I had this handy, so I used it. It is solid rubber, for sure, but yes the foil is relatively thin. If it works, great. If it doesn’t work at all or doesn’t work as good as it could have, I wasted a few hours.

But, didn’t Dynamat start out as an automotive product?

Gardenstater

OK well that's good if it's solid. I had never heard of the product so I did a little research and found no tech info.. Just the statement that it was good for thermal and road noise and they said they used to use HushMat but now it is their own product called Sound Assassin. Made me think that they got the supplier manufacturer for HushMat to sell to them too and called it Sound Assassin. The HushMat Megabond is the only picture they deign to show and definitely appears to be a foam but maybe their other products are not, but makes me wonder why it would be so good for thermal insulation as claimed. I just don't like it when comnpanies don't give tech data.

https://hushmat.com/pages/comparison-chart/

Gardenstater

OK the Megabond foam is definitely a different product and the other stuff is very thin (2mm) with a thin aluminum skin, thickness not specified, and they make the claim that their product is thinner and denser than the other ones and somehow doesn't conduct as much heat as the other ones, which definitely does not compute in my brain but whatever. Sorry if I caused any confusion but I was curious.

https://hushmat.com/products/door-kit-silver-foil-with-self-adhesive-butyl-10-sheets-12inx12in-ea-10-sq-ft

Gardenstater

Just one more thing. Dynamat Xtreme is thin as well (just 1.7mm) but they specify the aluminum thickness as 4mil = 0.004". Perhaps that is the difference pending you measuring your stuff.

https://www.dynamat.com/wp-content/uploads/2021/03/2036-Xtreme-Arch-Sell-Sheet_Web.pdf