RTA12

mrmuckel

One side quit. Tested for air leaks (neg.) Solutions?

pitdogg2

We're going to need way more info than you have provided.

mrmuckel

Sure. I did change out two top speakers that had frozen. Could the new ones not be providing enough force to activate the radiator? What else can I provide?

Gardenstater

Lots! It's always best to give a little bit of background story because something you might not think is important, may be.

How did you make sure you have no leaks, as in what exact method did you use? Do both passive radiators move equally freely when you exercise the cones manually? What were the drivers that you had and what did you put in?

mrmuckel

Smoke test by burning incense inside case then sealing. No smoke, no odor.
Interesting difference in cone movement. The original cones move freely while the two now ones seem stiffer. The reaction to movement is much less. Problem found?
I have pics of original and replacements.

Gardenstater

RTA12, RTA12B, or RTA12C?

Don't use incense or smoke or anything like that under low pressure. It might damage the speaker and it isn't likely to leak out of a small crevice without pressure and you don't want to pressure test anyways.

Push the passive in and hold it there. The Midwoofer should move out as you push and hold the passive in, then slowly retract partially over a period of several seconds and should not go back completely to the home position until you release the passive.

The MW# must be correct for the model of RTA12 you have. The passives are tuned to match the MW and the cabinet enclosure volume.

mrmuckel

Had to retype for some reason.
Smoke test by burning incense inside case then sealing. Bo smoke, no odor.
Interesting difference in cone movement.The original cones move freely while the two new ones seem stiffer. The reaction to movement of radiators is much less. Problem found?
Here are pics of new ones and original.

Gardenstater

I'm not saying this is the whole problem but that Made In China substitute isn't a decent match for the MW6500. The compliance is 3x stiffer (stiffness inversely proportional to Vas) than the MW6500 and you can see the Qs are completely different and Fs is very different as well.

pitdogg2

mrmuckel wrote: »

Smoke test by burning incense inside case then sealing. No smoke, no odor.

Just when you thought you seen and heard it all ....
Congratulations you're at the top if the heap.

Those midwest "replacements" are junk. They're a jack of all trade speaker, master of none.

mrmuckel

No surprise here. A search indicated 6503 would be a good fit. OWell. Any suggestion where proper units can be found? How about wiring? I know some speakers need particular sequence to avoid wave canceling or decreased output.

Gardenstater

mrmuckel wrote: »

No surprise here. A search indicated 6503 would be a good fit. OWell. Any suggestion where proper units can be found? How about wiring? I know some speakers need particular sequence to avoid wave canceling or decreased output.

I'm gonna say first do the leakdown test properly the way I said above and then report on the results.

Yeah you absolutely need the polarities to be correct or else one driver could cancel the other one out. If you touch a 9V battery briefly against the terminals you can verify that + to + and - to - will cause the cone to move outwards. Look at the schematic too. Black wire is positive and White is negative. Black nut on binding post is negative and Red is positive. Red should be on the left.

The Polk MW6503 is fairly close to the MW6500 but that made in china one isn't a Polk MW6503.

mrmuckel

Leak test…both units responded similarly with push in and release. Time out, instant…time back in, 0.5 sec. delay with fully in at release. I understand the delay should be slower. Test of polarity on new units showed opposite reaction to battery. See photo.
Test on original units showed similar reaction with positive to red dots. See photo.


System is RTA12 A. No red wires blue instead.

Gardenstater

mrmuckel wrote: »

Leak test…both units responded similarly with push in and release. Time out, instant…time back in, 0.5 sec. delay with fully in at release. I understand the delay should be slower. Test of polarity on new units showed opposite reaction to battery. See photo.
Test on original units showed similar reaction with positive to red dots. See photo.
System is RTA12 A. No red wires blue instead.

It's good that they both did the same on the leakdown but 1/2 sec is way too fast so they both may have leaky gaskets and/or cabinet joint leaks. Should be at least 3 secs. My 1979 7Bs take more than 3 secs to pull in partially while still holding the passive in.

If I understand correctly you are saying that those made in china ones had one of them marked with a red dot on the negative terminal and therefore you had one wired in with the wrong polarity and it was cancelling out the other one. Correcting that will most likely make a huge improvement.

Polk used Black/Blue for positive on midwoofers and White/Green for negative. Binding post nuts: Red = positive (on the left) and Black = negative (on the right). Never did they ever use red wires for midwoofers afaik.

I see one MW6501 and one silver basket MW6500 in your one picture. I think the MW6500 is the original equipment and they should both be MW6500.

mrmuckel

I’m going to take a break. More tomorrow. Thanks for your insight. Muckel out.

boston1450

mrmuckel wrote: »

Leak test…both units responded similarly with push in and release. Time out, instant…time back in, 0.5 sec. delay with fully in at release. I understand the delay should be slower. Test of polarity on new units showed opposite reaction to battery. See photo.
Test on original units showed similar reaction with positive to red dots. See photo.


System is RTA12 A. No red wires blue instead.

Question. Maybe I misunderstand your post....Did you push in & hold passive in ? As you hold the passive in (keep'n it in) you will notice the MW woofer goes out. Count how many seconds the woofer goes back to resting spot (while still holding in) . 3 to 5 seconds is good. Any less is probably a leak. Lightly check all screws. Don't over tighten them.