RTA 12C's upgraded for forum member, w/ pics

TennMan

geoff727 wrote: »

Good eye. I used 6-24's for the tweeters. 8-24's on everything else. I think that's right.

Thanks for the info. Seems like a good idea to me. I have a couple of screws that are on the verge of not holding. I was wondering how to correct that problem when I do the crossovers. I think the t-nuts are a good permanent fix for screws losing their grip in the cabinet.

Did you install the t-nuts anticipating using mortite? I don't see where you say what type of seal you used on the drivers. Was it mortite?

geoff727

TennMan wrote: »

Seems like a good idea to me.

Ya, it is....if you don't have a set of Larry's backing rings, that is.

TennMan wrote: »

Did you install the t-nuts anticipating using mortite? I don't see where you say what type of seal you used on the drivers. Was it mortite?

Original seals on mid-bass drivers. New foam seals on passives. The tweeters have Mortite on the back. This isn't a seal, of course. It's just a bit of vibration damping.

geoff727

Playing on the system. Seeing the speakers 'deployed', I've decided I much prefer the look and added height the new bases afford. Now we'll see what the next hundred hours does.

mmadden28

Awesome! Nice job!

-New gold-plated connectors (all driver hook-ups got these).

Where did you get these from?

geoff727

mmadden28 wrote: »

Where did you get these from?

SOLEN online, under 'Accessories'.

quadzilla

Veruh veruh nyuce. I'm inspired, seriously. I think I picked up several tips I'll be using when I do my CRS+ > 4.1TL upgrade in the next few weeks.

TrashyTrucker

Very nice work Geoff,

Thank you for taking the time to share with us.

drumminman

geoff727 wrote: »

Hi folks,

This is a pair of RTA 12C's that I just finished a bit of work on; these belong to forum member filmfreak1138. He wanted some sonic improvements to these. The original vinyl veneer and grill cloth is still in good shape, so it was decided to leave it as-is.

These speakers received the following:

1. Crossovers (all 4) upgraded with a ClarityCap SA/AXON mix.

2. New, larger, taller, heavier bases built. Each base has 4 floor spikes on the corners.

3. New binding posts.

4. New wiring.

5. T-nut and metal screw driver and crossover mounting hardware.

6. Installation of 3-layer Sonic Barrier.

7. Replacement of original top crossover-to-enclosure connectors with newer, better ones.

8. Dynamat the driver baskets and JBWeld the driver magnets. Dynamat the passive radiators.

9. Give everything a good cleaning.

10. Re-do the finish on the grill logos.

11. Install RD0194's.

In the course of the work, I found (and re-did) several mis-drilled mounting holes for things, and one solder joint that was literally hanging on by less than a hair.

Okay, the details....and for some reason I took terrible pictures this time.

I'm very impressed not only by what you've done, but with the DIY "manual" you created for the rest of us RTA 12C owners. Looking forward to hearing your impressions of the speakers after everything has burned in. :cool:

Re: the RDO194 tweeters, did they fit? I'm under the impression that they're a little too large. Did you have to make any alterations to the tweeter plate or the mounting frame on the crossover? If so, how did you do this?

Also, can you post a link for the source for sonic barrier?

Thanks again and great work!

Fred

ohskigod

pure bad assery!!!!!

george daniel

man' that is very nice work sir--congrats.

geoff727

drumminman wrote: »

Re: the RDO194 tweeters, did they fit? I'm under the impression that they're a little too large. Did you have to make any alterations to the tweeter plate or the mounting frame on the crossover? If so, how did you do this?

The 194's fit just fine, but you do have to snap them into place; it's a very tight fit; the outer edge of the tweeter's faceplate has a very small lip that will fit on top of the tweeter mounting face. The rest of the faceplate fits right into the mounting face cutout with a tight snap. In short, the answer is no, no modification is necessary of the cutout.

drumminman wrote: »

Also, can you post a link for the source for sonic barrier?

http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=sonic%20barrier

geoff727

Thank you, folks, for all the kind comments.

virtualdean

geoff727 wrote: »

Crossover boards cleaned and some parts ready to go...

That roll of stuff is the new gasket for the passives. I had to destroy one of the originals prying the passive off the enclosure.

The caps are ClarityCap SA's for the high-pass components. All other larger value caps are AXON's. New binding posts are Vampire BP Hex. New Mills MRA 12's. And, at the request of Roger, the owner, I replaced the polyswitches with fuse holders (ACME Audio cryo-treated ones), so he can use high-quality fuses in the future and still retain tweeter protection.

(Those 2 ClarityCaps equal 4.4uf paralleled together. They replace that one yellow cap).

Very nice restoration and documentaion...

stubby

Love it. Despite all the electrical upgrades, which are very impressive, I like the "full" bottom base upgrade the most. I never liked the looks of the narrow "pedastal".

Makes me want to get started on mine!

stubby

DON73

Superior work! It's very refreshing to have someone on this forum so skilled and at the same time patient with those of us who have questions.
Do you have any plans to do a Monitor 10.......or have you done one I missed?
Thank you for the detailed explanation and photos.

geoff727

DON73 wrote: »

Do you have any plans to do a Monitor 10.......or have you done one I missed?

I've done a couple of Monitor 5's, never worked on a 10. I do have a pair, though. I keep thinking that those, along with my RTA 15tl's, and one of my 7's as a center channel, could make a prett neat HT speaker system. If I ever have the room and the funds, that is!

I think the next speaker project is a pair of non-functional LSi7's I picked up off the 'bay last week, for a computer desktop system.

geoff727

stubby wrote: »

Love it. Despite all the electrical upgrades, which are very impressive, I like the "full" bottom base upgrade the most. I never liked the looks of the narrow "pedastal".

Makes me want to get started on mine!

stubby

If these were mine, this is what I would have done...

Strip the vinyl veneer off. Build the base right on to the bottom of the enclosure, so it's literally part of the enclosure. Then re-veneer over the top of the whole thing. That would give the most coherent look, I think.

Keep in mind, the spikes on the bases, while providing necessary stability, and eliminating back-and-forth rocking motion in response to woofer cone movement (it's microscopic, but yes, it's there) result in a "leaning" of the bass and mid-bass. This is actually what I was after, as an aspect of increasing definition. Just something to know in advance, though.

nclh7

Very nice!!

danger boy

Geoff, you do amazing work.... your attention to detail is top notch. I look forward to hearing your thoughts when the burn in time is complete.

wow.. 30#'s more per speaker weight.. that is incredible..

thanks for all the pics and info

geoff727

danger boy wrote: »

Geoff, you do amazing work.... your attention to detail is top notch. I look forward to hearing your thoughts when the burn in time is complete.

wow.. 30#'s more per speaker weight.. that is incredible..

thanks for all the pics and info

Thanks, Al. I hope Roger will be able to enjoy them. They have several CD's worth of time into them, and they are beginning to 'wake up' now.

geoff727

I know you wanted some impressions of the way they're shaping up, so I thought I'd put it in words. To those who have done a lot of upgrades, this is all old news. But I wanted to write it here anyway for those who may be curious.

I spent almost the whole day today playing and listening. That, in itself, is a good sign. If a system is keeping you listening and enjoying, and not making you want to go do something else, that's a good indicator of the enjoyability and lack of fatigue yielded by the system. So screw the errands, I'm listening to music!

I moved the listening seat closer to the speakers by 8 inches. This helped to snap things into place, compared to yesterday's listening. The speakers are 6'10' apart, centerline-to-centerline. The listening seat (where your head is) is almost right at 8 feet from the front plane of the speakers. The toe-in puts the listener directly on axis with the speakers. The bases, of course, raised the tweeter height to right at the listener's ear. So, your ears are right in the exact center of the tweeter's 'beam'.

I have been listening with the grilles off.

Initial impressions are as follows:

1. Bass and mid-bass clarity, tonality, and definition is much improved. Especially on some jazz recordings I was listening to which have upright bass doing the 'walking', I was paying much less attention to the bass, and getting more involved in the flow of the music. I attribute this to an improvement in the bass to the point where it's simply not something that objectionably stands out; also, the individual bass and mid-bass notes that are coming from the speakers are more correct and discernable. The bass is simply providing the foundation of everything else, not just 'blobbing along'. That's good.

2. The treble is smooth as silk. If there's etch or grain, it's beyond my ears. Actually, I like the very high treble on these better than my Maggie's (the QR Maggie's don't get the high treble quite right, but the true ribbon Maggie's do). Maybe bikerboy Jeff can hear something I don't, when we bring them to the get-together in April. He heard a treble 'item' on my Maggie's that I hadn't perceived before, and really had to listen for.

3. Top-to-bottom (treble-midrange-bass) balance is improved.

4. Top-to-bottom clarity is improved.

5. The speakers are much more dynamic. The softs are subtler and more gentle. The louds put you back with more oomph. Kind of like taking the gloves off...the touch is softer, but the punch is harder.

6. The sound is not strained at all. It's quite relaxed, even on the loud dynamic passages.

7. The stereo image height is correct. The image stability is also good, and is improving. Front-to-back image spaciousness and airiness is not bad at the moment. We'll see if this makes some more gains.

In all, the speakers are becoming much more musically involving. These things are all great. If they don't wipe the floor with your old SDA-1's in almost every area, I will be really surprised....amazed actually! Now, the critical items...

1. I can perceive the crossover point between the mid-bass and the tweeter. There is a slight timbral shift as the sound (like an ascending piano run, for example) goes from being reproduced by the mid-bass to being reproduced by the tweeter. In a perfect speaker, that crossover point is imperceptible. I will note, this actually improved slightly when I moved the listening seat forward. That surprised me a little bit; but, that's the way it worked out.

2. At a certain frequency (or a small range of frequencies, maybe) in the midrange, I believe there is a resonance being set into motion in the outer enclosure walls. This was noticeable on certain voices. On one Julie Andrews recording, every time she sang a certain note in the lower portion of her register, I could hear that panel resonance coloration kick in. Then, when she changed key and was singing a different set of notes, things magically cleaned up. We'll see if your ears can confirm my suspicions (anyone in Seattle have an MLSSA or CLIO with an accelerometer?). The only way to fix these kinds of things are usually to brace the heck out of the enclosure, which is going to alter the bass frequency response in these speakers (not for the better), unless we want to totally rebuild the enclosures and account for the internal volume change afforded by the internal braces. Another way is to build the thing out of fancier materials...thick baltic plywood layers, resin phenolics, aluminum, etc. Pricey options (but wait till you see what I have planned for my Monitor 7's, 10's and RTA 15tl's. Hint, hint).

In short, I think we have made a large improvement; the total price you paid (purchase + new tweeters + upgrade costs) I think is totally justifiable for what they're sounding like. And things should continue to improve over the next little while. They have probably 30 hours or so onto them right now. More later...

On3s&Z3r0s

Wow... that is just phenomenal work. Kudos for such a beautiful job.

audio_alan

Very nice! Excellent work and attention to detail.

Thanks for taking all of the pictures and sharing with us. I'm surprised that they gained 30 pounds though. From your pictures, it looks like you needed to remove 30 pounds of glue from the cabinets! What a mess that was! :eek:

danger boy

nice write up Geoff... sounds like there was some very decent improvements in the overall sound.

I am curious as to why with the increased inside material for sound absorbtion that one of the speaker is resonating at certain frequencies? wouldn't the sonic barrier control that?

geoff727

audio_alan wrote: »

From your pictures, it looks like you needed to remove 30 pounds of glue from the cabinets! What a mess that was! :eek:

Boy, you got that right. At least the glue doesn't weigh anything. But I think I freed up a cubic litre of space inside each speaker! All that glue took up a whole garbage bag. Felt good to have it gone.

geoff727

danger boy wrote: »

... sounds like there was some very decent improvements in the overall sound.

Yep, there are, without a doubt.

danger boy wrote: »

I am curious as to why with the increased inside material for sound absorbtion that one of the speaker is resonating at certain frequencies? wouldn't the sonic barrier control that?

Let me comment on this in the morning.

geoff727

On3s&Z3r0s wrote: »

Wow... that is just phenomenal work. Kudos for such a beautiful job.

Thanks. Roger is bringing them to the Seattle get-together, so I hope you can make it.

filmfreak1138

The first thing I want to say, Geoff, is, thanks for the incredible amount of work you have put into these speakers! You have gone above and beyond the call of duty, and I am grateful for your patience, time, and hard work. I appreciate what you went through dealing with a cheapskate like myself, making sure I got the best stuff possible for the money I was willing to spend. Whether you were looking for the best price on parts or finding FREE shipping offers, as soon as you learned that you could save a few bucks, you would call me and say, "you can save money here, so let's upgrade there and add this here."

If the Polk forum folks knew about the fun time you had dealing with me in keeping the price within the range that I originally wanted, they would have told you to just drop the project and toss the speakers in the bay! What started as a simple upgrade turned into a major overhaul that has far exceeded my expectations. I am SO glad that you talked me into a lot of the upgrades because once those speakers hit my home I will be one happy mother until the end of time!

And… we only went $70.00 over budget!

Thanks again! I'm looking forward to seeing, and HEARING, these speakers at the April meet-up!

Geoff, I like your first review. It made me feel better about that money thing. I can't wait to read the next one when the speakers hit the 60hr mark. It just made me feel a little more sad that I can't see or hear them until April. Thats good news for you readers.

So, if any of you folks would like to hear and see these RTA's come to the Seattle get-together. You are welcome.

Joe08867

First off, Awesome job. They look great and your write up was very good.

Secondly, I had an issue with resonance at certain frequencies on my SDA2's and used a strip of dynamat about 2 inches wide in an X pattern along the sides and back and it worked wonders. I also tried doing the area behind the front panel but it actually seemed to deaden the sound to much so I removed it. That sucked, that stuff is super sticky. I also used sonic barrier on top of the dynamat for absorption like you did.

I also tried bracing a set years back but the results were not quite as good. I didn't blow apart the cabinets and just added the bracing in sections. To form an X horizontally from front to back just above the PR and another vertically between the drivers front to back. I believe this would have worked better if I had taken the cabinet face off but I was afraid to damage the original structure to much.

Joe,

geoff727

geoff727 wrote: »

But I think I freed up a cubic litre of space inside each speaker!

What's funny is, the first thing I thought when I got out of bed today was, "did I actually write that last night?!" Yep, I did.