1x Rd 0194, 2 x mw6600x Needed!

jwoods2112

A little turntable accident wrecked both 6600 drivers and the rd-019 is a reading 6.7 ohm across its terminals and can barely be heard on my left rta 12c

Accident won’t happen again if anyone has some spares they can share for a price?

Clipdat

How can we be assured that the accident won't happen again?

Gardenstater

6.7 Ohms for the RD0194 is pretty much spot on. DarqueKnight measured 6.6 Ohms. Maybe the problem is the polyswitch.

jwoods2112

Clipdat wrote: »

How can we be assured that the accident won't happen again?

TT Ground strap came off the phono stage and sent a god awful frequency to the speakers, surprisingly only the left speaker was damaged.

jwoods2112

Gardenstater wrote: »

6.7 Ohms for the RD0194 is pretty much spot on. DarqueKnight measured 6.6 Ohms. Maybe the problem is the polyswitch.

Thanks for reply, I’m a bit of a fish out of water as I’ve never killed a speaker as I did. There was still faint HF coming out of that tweeter but not strong like at the other speaker. I have the fused version crossover and fuse appears to be undamaged.

Is it possible I damaged some crossover components, or that the two mid range woofers being fried would limit output to the tweeter?

jwoods2112

Amp and preamp seem to be doing just great with another set of speakers I’ve now got running

jwoods2112

Called Polk parts today to see what they recommend on the two mid drivers, and they gave me the appropriate driver replacement part #s Midwest sells. Q is, am I better off with used originals or new from Midwest? Are Midwest’s made by same OEM?

Gardenstater

A few questions first. These are the RTA 12Cs? But maybe with a RTA 12B crossover? Supposed to be a 3/4A fast blow fuse in there? I'd swap fuses L to R and see what happens. Maybe the fuse is damaged and just barely making contact. That'd be weird but needs to be ruled out.

It's a very complicated crossover for sure. What do you get when you put an ohmmeter across the + and - binding posts.....nothing? Have you checked the MW drivers for resistance? How about + to - posts with jumper wires across the two MWs? Swapping tweeters next would be something to try. Would rule out tweeter damage after fuse is ruled out completely. May have had suspension damage from over excursion even if the voice coil didn't melt.

I haven't heard any feedback on those probably made in China copies that Midwest sells. I would definitely go with the originals because no matter what you get, they need to match what is in your other speaker.

jwoods2112

Will do further testing and report back Gardenstater, thanks for replies! Yes speaks are labeled 12c with crossover boards labeled 12b. I guess when Polk was young no parts went to waste! Maybe I have 12b mislabeled as 12c on the back label?

I did lots of work on these, new caps, epoxy on the magnets etc. anyway one mid driver is completely frozen and the other moves in and out like there is gravel packed in there.

Gardenstater

So if the magnets were epoxied on both sides I guess it isn't too likely that anything shifted. I'm wondering if the voice coils got mashed due to over excursion and bottoming out against the T-yoke aka pole piece. That is one possibility. It could be and/or spider damage.

xschop

Sounds like the coil ends got damaged.

jwoods2112

I assumed mid drivers were toast with one stuck in position and the other felt like a rocky road moving it in and out. Found a pair of 6600x on the bay, price not too inflated but not a screaming deal. seller had done a pretty nice epoxy job on the magnets, with recent measurements posted, hopefully it’s plug and play. Tough spending money on some really old drivers, but research pointed to matching what was inside the other speaker. Buy used or buy the knock-offs I guess. Wish the mid drivers matched up to something modern that has just a little more power handling, 6600x doesn’t stay wonderful when really pushed, so I don’t.

jwoods2112

Gardenstater, I took some measurements as you suggested, got 4 ohm at speaker terminals, both fuses tested the same, so I’m obviously going with replacing the mid drivers as I’ve no skills repairing obvious damage to their movement. I’m hoping the tweeter was undamaged by whatever frequency or wave form that was

pitdogg2

What is your amplification?

Gardenstater

jwoods2112 wrote: »

Gardenstater, I took some measurements as you suggested, got 4 ohm at speaker terminals, both fuses tested the same, so I’m obviously going with replacing the mid drivers as I’ve no skills repairing obvious damage to their movement. I’m hoping the tweeter was undamaged by whatever frequency or wave form that was

Hopefully not damaged. I would still say that the way to get a better handle on that is to swap tweeters. If the same speaker still plays low in the tweeter dept. and the formerly low playing tweeter is now OK, then maybe it has to do with the frozen drivers. Maybe when they are not moving the impedance is less. Not sure. But if that was the case, then the tweeter might get less signal. If not that, then something in the tweeter circuit is damaged. Unless the fuse was too high of a value (should be 3/4A) that shouldn't be likely because fuse would've protected.

jwoods2112

I will swap the tweeters, and see

jwoods2112

pitdogg2 wrote: »

What is your amplification?

Yamaha pc2002m, probably way more gas than they need, in my medium sized room. when I first found these speakers I saw recommended power of 100-500w/ch! So I got an amp that does 240/ch. At least in my experience, 240 is way more than plenty, and I do know my room has a lot to do with things, but after moderately loud there is diminishing returns on sound quality. Maybe in a barn you could use 500w with these?

jwoods2112

Tweeters are amazingly back in stock at Polk fyi

pitdogg2

jwoods2112 wrote: »

pitdogg2 wrote: »

What is your amplification?

Yamaha pc2002m, probably way more gas than they need, in my medium sized room. when I first found these speakers I saw recommended power of 100-500w/ch! So I got an amp that does 240/ch. At least in my experience, 240 is way more than plenty, and I do know my room has a lot to do with things, but after moderately loud there is diminishing returns on sound quality. Maybe in a barn you could use 500w with these?

Well not all watts are created equal. Yes your room interaction is also a big consideration. I do not know what kind of current that pro-amp is able to push with those watts. I do know you can have some pro-amps that push both a lot of watts and higher distortion at the same time with little current. (more distortion in the signal verses a well built home stereo amp) It sounds like when that wire came loose a huge spike was sent to the speakers, it could very well have been enough to clip the amplifier and send a huge square wave, which is what it sounds like.

Buy several Rd-0194's while you have a chance, let Polk know you're amember here for a small discount. Polk will not continue to support them so it would be good idea to have a few on hand. As for the MW6600 you can also look for the MW6501. Both the MW6600 and MW6501 were used in the same speakers with no XO change. I've used them both in my SDA1 speakers. The SDA1 started with the MW6600 then went to the MW6501, both used the same OX and they both have the same sound signature characteristics. Food for thought.

jwoods2112

Update: swapped the tweeters, seems to be undamaged, simply a case of it sounding different in an environment without the mids working. Thanks for the replies y’all. Replacement 6600x’s showed up, packed superbly, through them in and back to having fun—so far!

One thing I noticed is that on my 6600x’s the doped cones are slightly glossy and have some sticky-ness to them, these are more dried out, not as glossy looking. Different batches I imagine?

jwoods2112

Pittdog, I get it regarding amp and watts, never been able to really read specs to determine high current. This Yamaha amp didn’t have any specs at 4 ohm output, it’s obviously built like a tank, might come close to doubling the wattage at 4ohm? Research on AK showed others using it successfully for home hifi—I’m a sucker for meters, it has gain controls, and doesn’t have a fan for cooling-pretty big heat sinks on the sides. Always sounds nice and clean. Would be cool to hear these speakers driven by something with class a power, or a known high current design.

pitdogg2

An amp that can double or nearly double the wattage from 8 to 4 ohm is going to have high current. IF yours does not mention any spec for 4 ohm then that in itself can be questionable. Meaning more than likely it is not a high current design.

you can clean the speaker cones and surrounds with original windex and a microfiber cloth. You may notice a ton of dirt coming off and the tacky glossy look should come back. The dirt in many cases looks like a rusty color. be sure to keep the cloth wet to keep from grabbing on the doping compound. DO NOT SPRAY THE DRIVER ITSELF.

Gardenstater

jwoods2112 wrote: »

Update: swapped the tweeters, seems to be undamaged, simply a case of it sounding different in an environment without the mids working. Thanks for the replies y’all. Replacement 6600x’s showed up, packed superbly, through them in and back to having fun—so far!

One thing I noticed is that on my 6600x’s the doped cones are slightly glossy and have some sticky-ness to them, these are more dried out, not as glossy looking. Different batches I imagine?

And different environmental conditions. They are pretty old now. My MW6500 cones were super sticky when I bought the speakers in 79. Now they just grab the finger slightly when you slide over it.

Good result on not having a damaged tweeter and getting good MW replacements!

I remember lusting after those ones (earlier and lesser model than yours) after I spent as much as I could afford without pain, in college. Those MWs will respond well to further modding, should you choose to do so. Jazzhead is happy with his mods.

jwoods2112

They are a great loudspeaker, I got them along with some other stuff, just before the covid lockdown days, from a local guy. I only wanted the other stuff (some crusty NAD stuff and a denon tt) but he insisted everything must go or not at all. Needless to say the rta 12c’s were the only magic in that lot.

As for the old Yamaha pro amp, I can only say price was right and it sounds awesome with the right preamp. currently using a tube preamp with it= sounds crisp, clean, full range, and man do rta 12c project wide image

dromunds

Denon makes some dang nice TT’s. Which model did you acquire?

jwoods2112

Dp 45F kind of mid grade I imagine. Used it for awhile sounded great but was tough to keep automatic functions running, so I sold it for a decent amount. It was a cool looking machine at night nice red light that shown down on the platter. Moved on to a dual 704=less cantankerous

boston1450

What NAD came with it ? I had a NAD 3020 20wpc hooked to Polk Monitor 7 with peerless tweeters & it was pure bliss. NAD has some fine gear.

F1nut

This Yamaha amp didn’t have any specs at 4 ohm output, it’s obviously built like a tank, might come close to doubling the wattage at 4ohm?

It's not a high current amp.

Research on AK showed others using it successfully for home hifi

In the land of cheap is the main criteria using a piece of kit successfully takes on an entirely different meaning.

Edit: forgot to mention, depending on the source your speakers are either 4 ohm or 6 ohm nominal. Either way, your pro amp isn't really a good match.

Jazzhead

jwoods2112 wrote: »

pitdogg2 wrote: »

What is your amplification?

Yamaha pc2002m, probably way more gas than they need, in my medium sized room. when I first found these speakers I saw recommended power of 100-500w/ch! So I got an amp that does 240/ch. At least in my experience, 240 is way more than plenty, and I do know my room has a lot to do with things, but after moderately loud there is diminishing returns on sound quality. Maybe in a barn you could use 500w with these?

I have the original RTA-12's, so yours are much more advanced in several ways. My experience (and comments made by others) is that this line of speakers (the original, B, and C) can quickly lose composure when pushed without some mods to control the driver backwaves slapping around inside the cabinet (the sound will devolve into a roaring, inarticulate mess). Add a clipping amp into the equation and it just gets worse. As mentioned above these speakers thrive on gobs of clean, high current amplification. Mine are in a 14 x 26 ft. room, and with the right mods my ears cry uncle before they lose composure. You could easily drive these with 500@8/1000@4 wpc (or more) of clean power, and they would sound more rich and detailed throughout the entire volume range - especially at lower volumes.

jwoods2112

Trying to find out more info on the amp, all I could find is Yamaha’s attempt at a performance chart for it. Should be said that I never push this setup into a danger zone, similar sized room to Jazzhead’s and sound pressure levels go nuts far below any extremes on the equipment. But here’s the chart, hopefully I don’t have to sell the polks LOL

jwoods2112