Rta 12c

[reeltrouble1]

Another nice vintage set, a pair of POLK RTA 12C comes into the RT1 family, these are very fine looking, the past care taken with them is obvious, this set is for my older son who has begun his own path to audio nervana.

A big thank you to Doro for holding these till he could pick them up along with treating my boys so well on their visit. They were also very impressed with the SVS demo Mark.

RT1

[reeltrouble1]

And another of the speaker array:

Had a quick listen and was impressed right off with the imaging.

[dorokusai]

Glad you guys are happy..those have been through a couple "family" members hands, so take care of them. Just passing on some goodwill.

Here are the spec's per you request:

RTA12C

39H x 16W x 11 7/8D
75 Lbs.
17Hz - 26,000Khz
10 - 500 WPC
4 Ohm
92dB Efficient
118dB Max Output

It's a great speaker, that why I bought another....wink wink.

I cleaned yours up real good prior to being boxed again, and everything was treated with CAIG products. I also repaired a broken grill mount with a damn near identical replacement part that I sourced from PE. Can you find the odd man out?

Your boys were very cordial and nice to chat with, sorry they couldn't stay longer, but the road was calling. Thanks so much for the Jackets and T-Shirt.

I tried to kill them with the SVS.

I was lax in ordering my stuff for you, so give me a week or so, and it will be at your door.

[Tour2ma]

Most unusual speaker in the Polk family...

[TroyD]

Man, those things have made the rounds up the I-95 corridor....


Enjoy 'em Ted !

BDT

[George Grand]

Too bad I never got to meet the original owner.

George Grand (of the Jersey Grands)

[reeltrouble1]

Certainly a bit different design than Polk's usual, however, drivers are familiar. What is the idea with the tweeter electronics?

As far as 95, well, they will be headed back up to New Jersey later this month. Will end up around Toms River.

RT1

[RuSsMaN]

Time alignment big poppa, time alignment. That, and the crossover is a little over-built (a good thing), compared to the rest of the series.

[dorokusai]

Real Time Array. It's the only RTA that really follows that idea IMO.

It aligns the voicecoils on the drivers so that, in theory, all the frequencies should reach the listener at the same time. High frequencies move faster than low frequencies. It results in better imaging and soundstage.

Another example....The stands for the Mon10..7 and 5 all have an upward tilt, so as to create in Russmans' words....a poor man's time alignment.

I have a pair of Mission Argonauts and B&W DM550 that both follow a time alignment idea as well. The Mission is more traditional, while the B&W is electronic(crossover related).

[RuSsMaN]

Hit the nail on the head Doro, short of the 'speed' statement.

The speed of sound, is this speed of sound, regardless of frequency. What is it, 720 mph at sea level, 650 mph at 40,000 ft? Now the size of the wave, that's another story.

What polk has done in the 12's (and accomplished with the 7's and 10's on stands as you mentioned), is align the voicecoil of the tweeter, with the voicecoil of the woofers.

Since the VC is the source of the sound, and woofers are typically 'deeper' than tweeters, setting the tweeter BACK to align (on a vertical plane) the voicecoils helps insure that the sound reaches the listener at the same time, from all the active drivers.

I think in the other RTA speakers, they probably used resistors to 'delay' the tweeter slightly, to compensate for the coils not being aligned. At least thats all I can figure.

Cheers,
Russ

[dorokusai]

There is a difference in frequency rates, and the effects of those rates on the conditions around or upon with which it travels.

Whether you subscribe to the theory that this is audible is another thing, I personally don't care either way, it's just another application to me.

If we could look at the schematics maybe that would determine the Bimmer effect.

Trivia question:

Why is an AM transmission tower warm or even hot to the touch compared to FM?

[HBombToo]

Originally posted by RuSsMaN


I think in the other RTA speakers, they probably used resistors to 'delay' the tweeter slightly, to compensate for the coils not being aligned. At least thats all I can figure.

Cheers,
Russ

This does not read right to me... true resistors should not change the timing of a circuit unless there are of course inductive or capacitive effects from a non perfect resistor(but now we are talking phase). I'm not even certain if I understand the relation between phase and coherence.... maybe someone can take charge here?

HBomb

[HBombToo]

Originally posted by dorokusai

Why is an AM transmission tower warm or even hot to the touch compared to FM?

because it is the tower that radiates not an antenna on a mast that radiates. That is the reason for all the ceramic isolation on the guy wires....

again when there is conduction there is resistance and the loss in power is dissapated as heat. "conservation of energy and mass ;) "

HBomb

[George Grand]

Ending up near Toms River is close to where the journey started. I found that pair at the McGuire AFB Thrift Shop!

George Grand (of the Jersey Grands)

[reeltrouble1]

Damm, I love learning about this sheeet. I had figured some of the crossover on the top of the cabinet although as said its over built compared to most things I have seen/taken apart. I thought I might try to launch something with it, yes just kidding. The setting back of the tweeter for alignment is most interesting, I did not catch that and yea, it would seem to be a better method than delaying through resistors or some other info. I will relay the lesson to junior. Thanks for the help guys.

GG--Guess they have come just about full circle then. Jr. has been known to pawn a few things in his life, if you see them again well now that would be something, however, he has been advised of pawning consequences, he did though buy these, hell should have, he only 30 friggen years old.

I have spent a bit of time at FT. Dix myself.

RT1

[RuSsMaN]

Originally posted by HBombToo
This does not read right to me... true resistors should not change the timing of a circuit unless there are of course inductive or capacitive effects from a non perfect resistor(but now we are talking phase).

I only mention it because I have seen it in some high-end designs. For example, if you have a front firing AND rear firing driver, placing a resistor across the pos/neg terminals of the rear driver can cause a slight delay, thus keeping 'timing' more correct with when the sound from both drivers reaches the listener (and still maintain absolute phase).

I haven't seen it on tweeters, but certainly on woofers. Now as to the values of the resistors, I have no idea where to start.

Cheers,
Russ

[dorokusai]

Is this what DefTech could be doing? or is doing?

[Tour2ma]

It is important to note that the sound speed in air (http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html) is determined by the air itself. It is not dependent upon the sound amplitude, frequency or wavelength.

Also interesting read (http://www.geocities.com/kreskovs/TimeAligned1.html) on cross-over design impact on time alignment. Bottom line appears to be that higher order cross-overs induce time delays...

[RuSsMaN]

Geocities? Thanks Tour, that's a reputable, noteworthy source. I'd put em right up there with the New York Times.

;)

That's interesting that the speed of sound has to do with the atmospheric condition, the air itself. I always though it was 'pressure' related, hence the altitude comment. So does this mean after a few bongs hits, and the air in my room is filled with smoke, my speakers will sound different?

Cheers,
Russ

[hoosier21]

Originally posted by RuSsMaN
So does this mean after a few bongs hits, and the air in my room is filled with smoke, my speakers will sound different?

Cheers,
Russ

yes they will,

but with the sound of a 1lb bag of fried pork skins being destroyed by a munchie fit, will mask any improvements offered by the smoke

[VR3]

Originally posted by dorokusai
Is this what DefTech could be doing? or is doing?

From what I know, that is what they do...

[Tour2ma]

Originally posted by RuSsMaN
Geocities? Thanks Tour, that's a reputable, noteworthy source. I'd put em right up there with the New York Times. Just one of many hits on "speaker time alignment".... and this one had pretty graphs... :)
At least you didn't put them at CBS Evening News level...

And since when do you smoke in the house???

ummmmmm... pork rinds....

[George Grand]

The speed of sound varies as to the density of air molecules. Higher up, less molecules, higher speed of sound. Lower down, more molecules, lower speed of sound.

The density of the molecules at lower altitudes is more resistant to sound waves as well as aircraft movement.

You guys really can't just enjoy the sound of a freakin' pair of speakers can you?

George Grand (of the Jersey Grands)

[Strong Bad]

No sh** George!

These guys are frying my brain with all this time alignment and speed of sound chatter!

Just listen and hush. :D


John

[dorokusai]

It was originally, simply an basic explanation of Polk's application in regards to the RTA12....the rest is just for information purposes.

I do enjoy them, and alot of other things...not all of us are SDA slaves.

[Toxis]

So how would you describe the sound on the RTA12's? Would you say they'd be better for a certain style of music? What are you running them with? I'm only asking because a local guy has a set for sale, but he wants WAY to much for them ($470/pr.). If they're really that good, I might make an offer.

[dorokusai]

They aren't $470/pr. good.

[Toxis]

that's fine, but again, how would you describe the sound. I'll probably offer him like $250-275...

[dorokusai]

I think they have a very open soundstage, beyond the physical design.

It simply feels larger to me....like it is more than a box radiating sound. The bass extension is better than a Mon10, easily, and the high end follows with the imaging....it's not box like anymore. I keep thinking "open"....but that's just my opinion, and on my junk.

It's the only RTA, I would even think about owning, and I do. It's the only one that is true to the definition IMO. The other RTA's are nothing special.....just speakers.

[Polk65]

Q: So how would you describe the sound on the RTA12's?....
A: Pointed towards a 45 degree listening angle, the stage seems to me to be painted across the wall both between and behind them, almost as good as my old 2.3TL's. I count the hours until I can press my power button ON. The sound is very open, almost like a laboratory test speaker for the SDA series.

Q: Would you say they'd be better for a certain style of music? What are you running them with?
A: Euro 2+ hour Goa/Techno/Schranz mixes, Blues, some Classical.

Q: I'm only asking because a local guy has a set for sale, but he wants WAY to much for them ($470/pr.). If they're really that good, I might make an offer.
A: Listen to them, if you like make an offer of $200 or less. If he wants more walk away (but leave your telephone number). $200 or less is the average selling price.

GOOD LUCK!

P.S. Bass response is a little weak imho. You may 'feel' the need to add a sub-woofer. Even with my Polk psw550, I don't 'feel' as much bass as that from my old sda 2.3TL's.

[dorokusai]

Bass response "weak"? I love the 2.3TL comparison....that makes alot of sense.

[RuSsMaN]

Anyone seen my baseball?

[reeltrouble1]

chuckle chuckle yea, ya think the 2.3tl might be a tad more speaker!!

The 12c are mighty fine speakers that most anyone who has any interest in audio would enjoy. As I said the imaging was very apparent the moment I hooked them into the B&K 7270, so we did some listening (father & son time), both with and sans the subwoofer their new owner (my son) gets a big smile on his face says cool, snatches them and hauls them up to his room, he plays with them all of yesterday, finally comes back down stairs and says " I think I need some better gear for these."

I explain the time alignment as it was relayed to me, he says ok, nice to know if someone asks me but he could really give a crap about all that right now, he just likes his new speakers.

Guess that about says it all.

RT1

[Tour2ma]

Like Father, like son, eh Ted?

Agree on $200 being around the top end for these. Tad more perhaps if mint and boxes, manual part of the deal...

As I think others are hinting, I don't find their bass to be weak by any means.... not SRS big, but I certainly don't feel they require a sub for music.

Type of music... Really good on some, but really not good on others. Not good bits included harsh highs and/ or bloated bass on some selections. It seemed the more "complex" the music, the more they struggled.

They looked like rock speakers to me, but found the above to be true in that genre'.

On the right music, I agree with the openess of the soundstage mentioned above, and "right" = simple...

[Tour2ma]

Originally posted by George Grand
The speed of sound varies as to the density of air molecules. Higher up, less molecules, higher speed of sound. Lower down, more molecules, lower speed of sound.

The density of the molecules at lower altitudes is more resistant to sound waves as well as aircraft movement.
Analogy doesn't ring true here, since a plane must push through air whereas sound uses air to move...

I thought for sure speed would decrease with altitude since we know the speed of sound increases in denser mediums such as water and again in solids. Where in air the speed is ~770 mph, in water it's 3240 and in steel it's over 10,000 mph...
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/soundv.html#c1

While it does turn out that sound does slow with increasing altitude, it's surprising (at least to me) that air density does not play a significant role. Temperature is the determining factor (colder ===> slower).
http://www.grc.nasa.gov/WWW/K-12/airplane/sound.html
Issue with temperature is that since sound must "excite" air molecules to travel, colder molecules are less excitable than warmer ones.

[George Grand]

That's my limit. Enough. I just want to listen to them.

George Grand (of the Jersey Grands)

[methenyiac]

I have a pair of RTA 12s in my listening room, right next to a set of KEF 104.2s. Soon, I'll be selling the KEFs. Although they're reknowned on sources like AudioReview.com, for me they don't deliver the magical highs of the old Polks. If I was a bass fanatic, I might choose differently. But all that the others have said about broad imaging from the Polks is true. These guys sing from outside the box! Price is also an issue, though-- The KEF's eBay price is over $600, while RTA 12s seem to go for less tham $200. Choosing between two great speakers is easy when one choice leaves $400 in your pocket. It only makes it better, for this audio cheapskate, that the Polks cost me $15, in perfect operating condition. I was making a donation to a local thrift store and there they were at the loading dock, not even priced yet. Charity has its rewards...

[dorokusai]

Where are you located Methenyiac?

[cfrizz]

Henry! How many times do I have to tell you SPEAK ENGLISH!!!;)

Doro, No more trivia ? that give me a headache & stop dissin my beloved RTA-8T's! :p

George Grand, you're the only one out of this whole group that's making any sense.:D

The rest of ya, stop analyzing & just enjoy the music!:rolleyes: ;) :D



Originally posted by HBombToo
because it is the tower that radiates not an antenna on a mast that radiates. That is the reason for all the ceramic isolation on the guy wires....

again when there is conduction there is resistance and the loss in power is dissapated as heat. "conservation of energy and mass ;) "

HBomb

[methenyiac]

dorokusai, I'm located at the foot of the Rockies, far from you. Why do you ask?:)

[dorokusai]

Meth - I saw a KEF model that I have always been interested in....too bad you're not closer.

Cathy - I'll let you kick me in the butt when you come to Polkfest.

[methenyiac]

Well, Doro...Just give me a call and I'll hold the phone in front of both pairs of speakers. What kind of music do you prefer? I have a lot of (no further hints necessary.):->

I'd be happy to jot down a few thoughts about the difference. I'll plop down in front of both for an hour and pretend I'm a critic on assignment. I'd hate to appear to hijack the topic of this thread, but so what.

My first, unscientific impression of the two is that the KEF is more realistic, more neutral, while the RTA12 has a sweetness and spatiality to the treble that I find captivating. If I hadn't heard that effect, I'd never miss it. And I'd marvel at the rich, full sound of the 104.2s. Which will be for sale soon, stay tuned.

[methenyiac]

By the way, what is an RTA 12c? My speakers say RTA 12. Is there a big difference?

[George Grand]

Cathy,

These are the same guys who busted the **** out of their toys when they were kids, cause they just didn't know how to PLAY with them. So they busted them.

George Grand (of the Jersey Grands)

[cfrizz]

I believe it George!!! Or worse they took them apart to see how they worked & then couldn't put them back together again.:D



Originally posted by George Grand
Cathy,

These are the same guys who busted the **** out of their toys when they were kids, cause they just didn't know how to PLAY with them. So they busted them.

George Grand (of the Jersey Grands)

[shack]

Originally posted by cfrizz
I believe it George!!! Or worse they took them apart to see how they worked & then couldn't put them back together again.:D
Then again...there were those who took them apart and not only were able to put them back together....but made them sound better in the process. You know....guys like Henry Kloss, Roy Allison, Paul Klipsch...and yes even Matt Polk, to name a few. Thank God for the "geeks" that not only liked the music, but liked the technolgy too.....

[reeltrouble1]

WTF

I started this thread to talk about my kid liking his speakers and to get some info, now were talking about busting things.

He is still loving the 12C's could care less about the science of RTA. Doro did him a favor turning him on to these for little coin.

I have "busted" lots of things, some hard some soft, come play with me.

RT1

[Airplay355]

hey george,
sound needs molecules to travel so if theres less molecules won't the sound travel slower? i'm just thinking of the whole bell jar expiriment and how sound doesn't travel in a vacuum, so wouldn't sound be faster with more molecules to vibrate?

[reeltrouble1]

Originally posted by dorokusai

Cathy - I'll let you kick me in the butt when you come to Polkfest.

hehehehe and when Frizz kicks it my camera will be ready!! ;)

[BottomFeeder]

I'm new to the forum and have just bought some RTA12C's in absolute mint condition. I love the "open" sound, how the music never seems to be coming from the boxes, but from the air or stage. IMO, the imaging is great. I also think the bass is good as well.

I'm lovin' em!

[reeltrouble1]

Well, congrats, they are fine speakers, the best of the RTA line IMO.

RT1

[ohskigod]

the rt-12b was my first vintage polk.. will allways have a soft spot for those things.