RTA11TL Upgrade Project

[skrol]

Since the tweeter went out in one of my RTA11TL's I have gotten the but to tweak. I thank you all for you advice on X-over components. The advice will be put to good use.

CHECK SOLDER CONNECTIONS!
I did want to pass along something that I found when I opened up the speaker with the bad tweeter. The x-over utilizes a 4.4uF mylar in parallel with a 12uF electrolytic to produce the 16uF that is in series with the tweeter. The 4.4uF is soldered to the PCB and the 12uF is soldered to the leads of the 4.4uF. This is where I found a problem. One of the leads was inadequately (if at all) soldered causing an intermittent connection. This means that at times there was only the 4.4uF in series with the tweeter. The result is that lower frequencies would be allowed to pass to the tweeter and likely caused the failure.

Other items:
1) The Daycron batting is apparently misplaced. Instead of being directly behind the MW6510's, both pieces are laying horizontally below the MW6510's. Over the years it may have fallen.

2) While testing the cabinet for resonance, I found that the wires that go from the x-over to the drivers was buzzing against the metal speaker baskets. I plan to secure the wires after I upgrade the x-overs.

3) The cabinet sides do tend to resonate and there is no side-to-side bracing. I'll probably add some bracing and some sound deadening material.

The replacement tweeters are on their way. I can update this thread as the project continues. I do welcome any advice.

Stan

[MillerLiteScott]

Sounds great.

Where are you located in MD?

[John30_30]

hi Stan-

I recently picked up a set of RTA11T's, upgraded the crossovers, and had to fix the bottom radiators whose surrounds had totally deteriorated.
I really like the sound without upgrading the tweeters- which seems to be almost a standard to-do, otherwise.
However, I can't believe Polk used particle-board with vinyl coating to build these otherwise wonderful units. The speaker shop I worked in years ago, Norman Labs used walnut-veneered MDF, and it was true MDF.

I'm wondering about what you call resonance in your speakers. I know I can feel a vibration on the outside of the cabinet when there's music on, but I'd hardly call it resonance.

I've been toying with redoing mine with some 3/4" rosewood plywood scraps I've had laying around forever, and customizing the look to go with them being furniture quality units.
While rosewood hardwood is extremely resonant, 5-ply veneer-core plywood is not. I was also thinking about a sound-deadening inner coating like you mention, but I'm wondering how necessary that would really be.

[skrol]

Sounds great.

Where are you located in MD?

I am in the Howard County. I grew up in the Baltimore area.

[skrol]

hi Stan-

I recently picked up a set of RTA11T's, upgraded the crossovers, and had to fix the bottom radiators whose surrounds had totally deteriorated.
I really like the sound without upgrading the tweeters- which seems to be almost a standard to-do, otherwise.
However, I can't believe Polk used particle-board with vinyl coating to build these otherwise wonderful units. The speaker shop I worked in years ago, Norman Labs used walnut-veneered MDF, and it was true MDF.

I'm wondering about what you call resonance in your speakers. I know I can feel a vibration on the outside of the cabinet when there's music on, but I'd hardly call it resonance.

I am also a little surprised at some of the cost saving measures. But things were tough for technology related businesses in the late 80's - early 90's.

As far as resonance... If your tap on the cabinet, you can rear the and feel the cabinet sides vibrate (ring).

In some ways I am reluctant to change too much as while some of the characteristics may seem to be flaws, they were also part of the design and may have been compensated for in the tuning of the cabinet, damping and x-over. In the end it all comes down to the gifted ear of the designer and then the economics of production.

Stan

[zingo]

skrol, many of us have applied treatments to the cabs to address the resonance. Some have painted on a deadening material, so have applied internal braces, I and a few others have applied acoustic foam to the internal panels. I felt that this improved the cabinets and deterred me from wanting to rebuild them.


John30_30, what happened to the surrounds on your PRs? They are/were rubber, so deterioration isn't usually a problem. Were they damaged?

[skrol]

I was wondering about the foam panels. They seem rather thick and I am concerned that they would change the cabinet volume. However, they serve 2 purposes (dampen resonance of the cabinet walls and to absorb). The absorption has the effect of making the cabinet acoustically larger. Is it a wash as far as cabinet volume? If it works to bring the desired sound then I guess it is good.

Stan

[John30_30]

skrol, many of us have applied treatments to the cabs to address the resonance. Some have painted on a deadening material, so have applied internal braces, I and a few others have applied acoustic foam to the internal panels. I felt that this improved the cabinets and deterred me from wanting to rebuild them.


John30_30, what happened to the surrounds on your PRs? They are/were rubber, so deterioration isn't usually a problem. Were they damaged?

Hi zingo-

I'm mystified what caused it because all the other surrounds were/are supple. Both bottom radiators arrived with one brittle- intact but not flexible, the other was brittle and flaked away into pieces, as commonly seen in foam surrounds. I used a foam kit to rebuild them.
I was somewhat torqued at the seller for not mentioning that. He had kept them in his storage unit for some years, so who knows what happened.

[zingo]

Here is a quote from the foam mod on my RDO Monitor 5Jrs:

I decided to put high quality 1/2" foam on the interior panels on my Monitor 5 Jrs last night because I was in the tinkering mood. I cut the pieces to fit in a few minutes, making sure that I didn't cut foam pieces for the front baffle. After test fitting the pieces, I used the fantastic 3M 77 to glue them all in place. (Note: make sure that you are spraying the glue on the foam pieces and then fitting them into the speaker cabinet, not spraying into the cabinet itself. Also, spray the foam pieces outside and away from your drivers and cabinets) I then stuck the cabinets in front of a big fan and let them dry for a couple hours. After replacing all the components and drivers in the cabinets, I sat down for a little listen to see what the results would be.

I have read many reviews of sound deadening materials being used inside speaker cabinets with success. I started with the old "knock on the side of the cabinet" test. The results was not completely dead, as I was expecting with some 1/2" foam, but definitely reduced; only a very slight echo remained. From there I turned on one of my favorite albums, "Hiding Place" from a Christian vocal group named Selah. They are pretty well recorded both vocally and on the piano, as well as doing some great mixes with male and female voices. My first "foamed" impressions were a little more clear and defined. I can almost explain it terms of musical decay like you would have in a cathedral. This decay, or echo, had disappeared and left me with only the sound being reproduced, no extensions of it. The modification had not colored or changed the music in any other way, as far as I could tell last night. The bottom line is I accomplished what I was trying to do, improve the sound, and all with some foam and a little glue. Could I have used some more HIFI material and made a bigger difference, absolutely. But, I would have not been able to find out that so little could make a difference.

Let me know if I haven't answered your question Stan.

[John30_30]

I am also a little surprised at some of the cost saving measures. But things were tough for technology related businesses in the late 80's - early 90's.

As far as resonance... If your tap on the cabinet, you can rear the and feel the cabinet sides vibrate (ring).

In some ways I am reluctant to change too much as while some of the characteristics may seem to be flaws, they were also part of the design and may have been compensated for in the tuning of the cabinet, damping and x-over. In the end it all comes down to the gifted ear of the designer and then the economics of production.

Stan

Good points. I saw a thread where one of the guys used what looked like a vinyl-type or polymer resin as an inner coating. Just painted it on.

I'm also wondering about the variable of cabinet depth on acoustic performance. You know these speakers are deeper than they are wide, which I'm sure alot of research went into to get that particular ratio.

I dunno why I find that aesthetically cool visually, but my inner tweaker is wondering what an adjustable (in-out) back would do. I need to know when to leave well enough alone. ;)

[skrol]

I received my RDO198 tweeters today and after repairing the crossover, installed one of them so I could compare it to the SL3000. While I haven't had the chance to really put it through the paces, the RDO's are smoother sounding and less bright than the SL3000. I can't complain about the SL3000. I always liked the the way they handled brass and jazz piano where their brightness supported the liveliness of the music. I think it is more a matter of taste.

Stan

[John30_30]

I received my RDO198 tweeters today and after repairing the crossover, installed one of them so I could compare it to the SL3000. While I haven't had the chance to really put it through the paces, the RDO's are smoother sounding and less bright than the SL3000. I can't complain about the SL3000. I always liked the the way they handled brass and jazz piano where their brightness supported the liveliness of the music. I think it is more a matter of taste.

Stan

Interesting to hear that. I like some punch and brightness in horns, strings, vocals also, and can't really complain about the stock SL2000's in my 11T's.
However, redoing the crossovers was a must. The highs were so harsh before, it would induce this creepy lockup feeling in the back of my neck. My wife is even more sensitive.

p.s.
I'm listening to Eva Cassidy now on a rainy morning, and I think the tweets do her justice.;)

[skrol]

It seems that I made a bad assumption:(. I should have known better but I hope someone will learn from my mistake.

When one of my tweeters (SL3000) were not working after 17 years of faithful service, I assumed that it had gone bad even though these speakers are pampered. I did find that there was a manufacturing flaw in the crossover before I installed the replacements (RDO198-1). As I wrote earlier the 16uF is actually comprised of a 4.4uF mylar with a 12uf electrolytic soldered to its leads in parallel and that it was not soldered properly. I fixed this but later found that the new tweeter was intermittent. This turned out to be another bad solder connection to the crossover PCB.

Of course this got me thinking... I connected the assumed bad SL3000 to an audio source and BINGO, it works. So it looks like I spent $100 for no reason.:o I suppose I could sell either the RDO198's or the SL3000's to cut my losses.

Stan

[skrol]

Another RTA11TL question. For those with RTA11's, where is the Daycron batting placed?

Mine has it only at the top above the upper MW6510 and above the lower MW6510. There is none on the back, sides or the entire lower area where the PR's are located. I would have expected to at least find it on the back to attenuate the back wave.

I may experiment with different locations and later try more quantity and different material.

Stan

[Face]

I'm not exactly sure where it should be placed, but I know it shouldn't be in front of the PR's.

[zingo]

One of the things with the RDOs skrol, is they need to be burned in. I have given mine about 150 hours in the past, but your first impression of them will not be totally accurate. Give them atleast 100 hours, then try the comparison again.

Someone correct me if I'm wrong, but I believe the batting goes behind the mid drivers.

[musicmaniac]

It seems that I made a bad assumption:(. I should have known better but I hope someone will learn from my mistake.

When one of my tweeters (SL3000) were not working after 17 years of faithful service, I assumed that it had gone bad even though these speakers are pampered. I did find that there was a manufacturing flaw in the crossover before I installed the replacements (RDO198-1). As I wrote earlier the 16uF is actually comprised of a 4.4uF mylar with a 12uf electrolytic soldered to its leads in parallel and that it was not soldered properly. I fixed this but later found that the new tweeter was intermittent. This turned out to be another bad solder connection to the crossover PCB.

Of course this got me thinking... I connected the assumed bad SL3000 to an audio source and BINGO, it works. So it looks like I spent $100 for no reason.:o I suppose I could sell either the RDO198's or the SL3000's to cut my losses.

Stan

If you do decide to sell the RDO198's please let me know. Thanks

[John30_30]

Another RTA11TL question. For those with RTA11's, where is the Daycron batting placed?

Mine has it only at the top above the upper MW6510 and above the lower MW6510. There is none on the back, sides or the entire lower area where the PR's are located. I would have expected to at least find it on the back to attenuate the back wave.

I may experiment with different locations and later try more quantity and different material.

Stan

I seem to remember it's that way with my RTA11T's, basically around the mids and maybe some around the tweets too. Not quite the same model, and I don't know if the differences are only electronic, frankly.

Heck, it was only a few weeks ago I pulled the passives on bottom, in fact all the mids and tweets too, to do XO's.

I do recall the inside base being bare of foliage and drywall screws sticking up through it. That kinda weirded me.

[IrishNiner]

I know this is off topic but I wanted to thank John 30_30 for mentioning Eva Cassidy. I had not heard of her and went to check out her music. Wow! Fantastic! I am now a new fan of hers and will turn my friends onto her as well.

Thanks,

Farrell

[skrol]

On a friend's suggestion (why didn't I think of this?:o), I contacted Polkaudio regarding the positioning of the Dacron damping material. Ken at Polk said the Dacron should be placed above and behind each mid-woofer. As in "Configuration B". Where the diagram attached shows "Present Configuration" this was what I found when I originally removed the drivers and looked inside. Unfortunately, for Configuration B I don't seem to have enough Dacron material. I tried "Configuration A" and the bass seemed a little muddy. I now have it positioned as in "B" as best as I can and until I get more material.
Stan

[John30_30]

I know this is off topic but I wanted to thank John 30_30 for mentioning Eva Cassidy. I had not heard of her and went to check out her music. Wow! Fantastic! I am now a new fan of hers and will turn my friends onto her as well.

Thanks,

Farrell

N.P. She was a Baltimore native, fwiw. Figured I'd throw that in, since Polk is based there. :)
Her story is heartwrenching, which when you know some of her live performances were with full knowledge of her imminent demise, well....that's the real blues.

Also, considering most of her 'studio' material was homemade, it's quite good, quality-wise.

[IrishNiner]

Interesting life story. Great music.

I think I read on a web site devoted to her music/life that 8 of the 10 albums released were after her passing. Word of mouth has made her even more popular.

Farrell

[skrol]

My upgrade project has been on hold while I look for a new CD player and have no decent reference source. My CD player died and I fear hooking up my turntable as I have curious young children. I did apply damping material to the cabinet sides and back and to the woofer and PR baskets. The bass seems cleaner and the thump test indicates reduced cabinet ring.

I have also been gathering parts for the XO's (Claritycaps and Mundorf resistors). I initially was planning to only replace the caps and resistors for the tweeters as I had heard that replacing the inductors and caps for the woofers make little difference. The woofers do have electrolytic caps. Any thoughts?

Also, anyone have ideas for securing or wrapping the internal speaker wires to keep them from rattling against the drivers and cabinet?

Thanks
Stan

[Face]

I would replace the woofer caps also. Besides the fact that they do drift over time, a better quality cap will increase SQ, just not as drastically as a shunt cap in the tweeter circuit. You have to be careful while playing with inductors. Watch the DCR, make sure it's close to the OEM specs.

IIRC, the woofer caps in my Monitor 7's drifted over 20%. So I would at least spring for Daytons for the low pass.

Which Mundorf resistors did you pick up? I recently swapped over from Mills resistors to the green Mundorfs and was pleased.

You can use velcro to secure the internal wiring.

[skrol]

You bring up a good point about the caps. I probably will not touch the inductors. The resistors that I bought are the Mundorf MR10 1.5 ohm and the capacitors are Claritycap PX.
Stan

[Face]

You should be pleased with the results. Now get to it. :)

[skrol]

I was pleased with the results with the RDO198 tweeters. I can't wait to see what this does.

[skrol]

I can't seem to find 34uF caps. I will likely have to parallel (30uf // 4uF) or (33uF // 1uF) unless I can find a source. I am reluctantly having to do this (15uF // 1 uF) for the 16uF on the tweeters.

Anyone know of a source for the 34uF caps?

[ben62670]

Just get the 33uf. The stock caps are 20%, and 33uf is well within spec. Even 15uf would fall within spec for the tweeter.
Ben

[skrol]

Thanks. I didn't realize that the stock caps were 20%. I'll take your advice on the 33uF. I already have a couple 1uF that I can use to adjust as needed.