Can an SDA 6511 driver be used as a substitute for RTA 12C 6501 driver?

gstein

I picked up a few speakers this last weekend, including a set of PA RTA 12Cs and SDA 1Cs (with the wood veneer). The SDAs unfortunately had quite a few drivers that were damaged and no longer usable. At this point I think the SDA set are a parts set at this point. However, there are a few 6511s that appear to be in good working order.

One of the RTA 12 speakers has a 6501 driver that is rattling when the volume is turned up to around 9 o'clock.

My question is can I use one of the 6511s from the SDAs as a replacement for the 6501? Are the specs somewhat close or completely different?

pitdogg2

No! Too far off in specs

MW 6501 1.47 5.96 N 3.25 E - 3N/M
7.75 Ohms 31 Hertz

MW 6511 1.405 4.34 N 3.496 E - 3N/M 3.13 Ohms 29 Hertz

Your best bet is to sell the mw6511 to someone here and look for both mw6501 or mw6600 on ebay. Both of those drivers were used on the RTA12's while the xo stayed the same.
I've used both in my SDA 1 signatures that used the same driver with no discernible differences in sound.
There are 2 mw6501 driver ad's
And 1 mw6600 ad on ebay


Edit I see you have less than 100 posts so selling here you must have minimum of 100 posts

gstein

pitdogg2 - thanks for clarifying the driver differences. Since selling on PA forums is not currently an option, I guess I'll have to go the ebay route.

pitdogg2

Welcome to club Polk, stick around you be at 100 in no time.

gstein

pitdogg2 - what about using the MW6510 as a replacement for the MW6501?

I just realized the SDA 1Cs have two difference drivers, they have 2 MW6511s for the stereo driver and 2 MW6510s for the dimensional driver. I tested one of the 6510s and they measure around 7.2 Ohms on my DMM.

pitdogg2

MW 6510 1.39 6.32 N 3.41 E - 3N/M 6.57 Ohms 31 Hertz

Not optimal but you gotta do what you gotta do I guess....

When using a different ohm driver it does effect the crossover slope. One speaker may sound a little different and the SDA goodness may be affected.

gstein

So it sounds like it is ok and won't damage the speaker, but will likely change the acoustics. I guess I can swap it out and give it a listen to see if I can notice the difference between speaker A and speaker B, and can always purchase a MW6501 if the sound is too harsh or bad.

F1nut

Just get the correct driver and be done.

gstein

After testing, I think a new driver is just the beginning of the repairs that are needed to bring the RTA 12s back to life.

I just picked these up and did not want to test them until I had all drivers hooked up. I installed the 6510 and gave them a listen. The acoustics are not good, and not much better on the other speaker.

The tweeters appear to be working fine, but the 6.5 drivers were "bouncing" significantly, even when I didn't have the bass up all that high. Sounded terrible and did not want to turn it up past 9 oclock for fear of further damage.

All that said, I think these speakers will require a new crossover build. Anyone have any experience with the crossovers creating the drivers to move in and out more than normal, and if so, will a new crossover rebuild fix this?

pitdogg2

Post a picture of the speakers.
Front, back and XO

F1nut

Air leaks will cause the drivers to do that.

gstein

Thanks, guys...will post pictures in a few hours when I get back home. Also, I wasn't aware the RTA 12s were mirror imaged (just read up on that on the PA forum). I think I may have inadvertently connected the speakers backwards during my test. It's a learning process with each set of new speakers!

gstein

Here are some pics of the RTA 12s (believe they are the C model)

gstein

Any tips or techniques for isolating where a leak may be occurring?

I can take a look at the padding under each driver (and replace if suspect) and make sure all screws are tight, but would like to know if there are other areas to consider or any method to identify where a leak may be coming from.

pitdogg2

binding post cup, speakers and passive are the usual culprits.

One other thing. On those speakers the tweeters are connected out of phase to bring them back into phase due to signal getting reversed in the XO. So do not think that someone hooked them up wrong when you notice the black wire going to negative instead of positive. On this speaker that IS correct.

first just try to snug op the screws on everything. You can then push in on the passive quickly until it stops HOLD IN and count the seconds it takes the drivers to return to normal. You should get 3-5 seconds if you have a good seal. If they drop immediately and do not slowly return then you know you have a leak and may need new gaskets. Polk factory gaskets are paper thing that is normal.

gstein

Great advice, thanks!

It's possible when I took out the mid woofer and replaced it, I may have connected the wiring incorrect. I'm going to double-check the wiring on the mid woofers on both speakers today. I'll also check for leaks as suggested and perform the passive woofer test as you suggest.

I have a set of PA Monitor 10s w/ Peerless tweeters, so I'd like to get the RTA 12s working so I can perform an A/B test comparing the two speakers.

gstein

After examining the wiring on the mid woofers I think I connected them wrong.

Note: left speaker still has temporary SDA mw6510 driver I was using to test. I plan to purchase a replacement mw6501 driver per F1Nut’s recommendation.

pitdogg2

Yes black or blue should be positive for your woofers.




you can find that in this thread and look for RTA series. Yours look to be RTA12C

https://forum.polkaudio.com/discussion/38755/polk-audio-speaker-wiring-schematics-amp-more-all-models-except-sda#latest

gstein

Thanks. Wasn’t able to find a schematic, very helpful.

Regarding the model, I thought they were the “C” model since the sticker on the back shows R12C.

pitdogg2

True I fixed my post. The difference is a tweeter and a polyswitch. IIRC B had a fuse maybe and SL1000 tweeter either way the schematic is the same as far as wiring.

gstein

Ok, making some progress. On the speaker that has two good working mid woofers, I correctly connected the wiring on the mid woofer with the two white wires and the one black wire (this was previously connected backwards), Also, I tighten all screws on the mid woofers as well as all screws on the passive woofer. All the screws on the passive woofer required 1/4 to 1/2 screwdriver rotation to get them snug. When I did the passive woofer test, by pressing woofer in, it slowly released back to the "resting position" after about 4-5 seconds.

Hooked the one speaker up to my garage Sansui 2000X. I realize the 39 watts is not the ideal amp, but wanted to see how the speaker sounded to my prior test.

Oh man what a difference. Can't wait to get the replacement 6501 driver and repair the other speaker. Then I'll hook them up to either the Heathkit AA-1600 or Adcom 555 amplifier to see how they sound with a better, more powerful amplifier. I also plan to compare the RTA 12s against the Monitor 10s that I have as well.

Thanks for the help! This forum is awesome.

pitdogg2

Unfair comparison between the m10 and RTA12.

gstein

I know, just curious more than anything else. Also want to compare them to several other speakers that I have, including AR3a and Marantz Model 600.

Faustin

The Adcom 555 will open up the 12's to their true potential. I originally had 10's with Peerless tweets that I bought new in 1979. Bought some 12's that I restored. Like Pitdogg mentioned, no comparison. But I understand your desire to compare several different speakers. As a side note, if you do a search on the forum you should be able to find my thread in regards to my 12s. I sold them a while back.

gstein

Received the replacement MW6501driver and installed in the left speaker. Ran a quick test using the vintage Heathkit and what a huge difference compared to my initial impression. After getting the repaired drivers installed, and sealing the cabinets, the speakers sound very good, even though I didn't have them near a back wall (ran out of room with other speakers being in the way so I just put the RTA 12s in front of the existing speakers). Listened to some Ben Harper and it was so incredibly clean and clear, sounded like he was directly in the middle of the room singing live. Initially thought I may sell these, given the other speakers I own, but now I think I might have to find a place for them in the rotation!

When I have time, I am going to setup the Adcom 555 w/ the RTA 12s to compare against the Heathkit.

Thanks all for the help, much appreciated!

Kryten

gstein wrote: »

When I did the passive woofer test, by pressing woofer in, it slowly released back to the "resting position" after about 4-5 seconds.

Glad you are making progress. Just to reiterate, you each speaker has a tweeter and two midwoofers. The big round thing at the bottom is called a passive radiator which basically makes the cabinet seem larger. Many vintage Polk speakers do not have a dedicated low frequency woofer driver.