RTA 11t Crossover service

[59ctd]

Thanks guys. After I posted on the 34/33 question this morning and started looking around where to get them I remembered I had some speakers repaired 20 years ago here in the Twin Cities. Looked them up and Midwest Speaker Repair is still here in the cities. New location but same great guys. I dropped by there and got all new Solen Metalized Polypropylyne caps to replace all three caps on each XO. 34uF was not a choice so they recommended a 30uF and 4uF piggybacked in parallel to equal 34uF. They said to replace the yellow poly caps I have too and since I was there I got replacements for those as well. And like mentioned earlier, these are WAY WAY WAY bigger than the small electrolytics they are replacing. It should all fit though and I think I will copy how Polk hot glued them together - most likely I think in a bid to reduce vibration of the components and solder joints. This I guess is now my weekend project to get these soldered in and fixed up and be done with them.

 

[Swerd]

Thanks guys. After I posted on the 34/33 question this morning and started looking around where to get them I remembered I had some speakers repaired 20 years ago here in the Twin Cities. Looked them up and Midwest Speaker Repair is still here in the cities. New location but same great guys. I dropped by there and got all new Solen Metalized Polypropylyne caps to replace all three caps on each XO. 34uF was not a choice so they recommended a 30uF and 4uF piggybacked in parallel to equal 34uF. They said to replace the yellow poly caps I have too and since I was there I got replacements for those as well. And like mentioned earlier, these are WAY WAY WAY bigger than the small electrolytics they are replacing. It should all fit though and I think I will copy how Polk hot glued them together - most likely I think in a bid to reduce vibration of the components and solder joints. This I guess is now my weekend project to get these soldered in and fixed up and be done with them.

Solen MPP caps are very good build quality. Most Solens I've seen had failure ratings of 400V, making them larger than MPP caps rated at 250V. And all MPP caps I've seen are significantly larger than NPE caps – as you've seen. Have fun with your assembly .

You probably didn't need to replace that existing yellow (Mylar ?) 12 µF cap, but another Solen 12 µF cap is not a major purchase.

In the past, I had tried using hot melt glue in the crossovers I built. It didn't hold very well. Instead of glue, I now use nylon cable ties. If I don't like my first parts layout, it's easy to cut the cable ties and try another.

Here's a build photo, with lots of cable ties, from several years ago. When I took that photo, I hadn't yet soldered anything. I was checking to see if I could fit the XO into the cabinet.

 

[59ctd]

Well, I finally got around to swapping the new caps in and putting them back in the RTA 11t speakers. OMG what a massive difference and improvement - just wow! They sound like I remember them sounding years ago. I've been reading more about older Polks and it seems like everyone agrees the RD0194 are an improvement over the old SL2000 tweeters. The same place I got the new caps has them and the price is reasonable so that will be the next thing for me to replace on these speakers. Pic is of the 1st xo after the new caps were installed. Much thanks to everyone who chimed in on my post with helpful info. It is much appreciated!

 

[59ctd]

OK, I just picked up two new RD0194-1 tweeters. Took out the old SL2000 tweeters and find they were wired opposite of each other for 30+ years. is the white or the black the positive from the XO? I am thinking these are wired like home AC and RVs where white is the neutral/ground and the black is the positive but let me know if I have that backwards.

 

[ryanosaur]

OK, I just picked up two new RD0194-1 tweeters. Took out the old SL2000 tweeters and find they were wired opposite of each other for 30+ years. is the white or the black the positive from the XO? I am thinking these are wired like home AC and RVs where white is the neutral/ground and the black is the positive but let me know if I have that backwards.

Are you saying that the Tweeter on each of your Speakers was wired differently?

If a schematic exists showing the proper connection, then that should answer it for you.

Regardless, Black should be Hot if they follow convention.

But if they borked something, you need to figure out if the Tweeter needs to be wired IN (Hot to positive terminal) or OUT (Hot to negative terminal) of Phase.

 

[59ctd]

Are you saying that the Tweeter on each of your Speakers was wired differently?

If a schematic exists showing the proper connection, then that should answer it for you.

Regardless, Black should be Hot if they follow convention.

But if they borked something, you need to figure out if the Tweeter needs to be wired IN (Hot to positive terminal) or OUT (Hot to negative terminal) of Phase.

Yes the two were hooked up reverse of each other only at the tweeters. The white/black wires from the two XOs were hooked up identically and I just had them out and resoldered the wires in that feed the speakers and tweeters. These speakers are from June 1988 based on the stickers on the XOs and I bought them used from the Audio King outlet store probably around summer 1993. I knew they were not new and the price was hard to pass them up. I suspect a customer had them and blew out one tweeter and decided to unload them to A.K. for an upgrade and Audio King put one new tweeter in them. I double checked the one tweeter that seemed hooked up backwards and sure enough it has a date sticker on it from January 1993 so this one was not original to the speakers. Anyways I am confident I have the polarity on the new tweeters correct now.

 

[TLS Guy]

Yes the two were hooked up reverse of each other only at the tweeters. The white/black wires from the two XOs were hooked up identically and I just had them out and resoldered the wires in that feed the speakers and tweeters. These speakers are from June 1988 based on the stickers on the XOs and I bought them used from the Audio King outlet store probably around summer 1993. I knew they were not new and the price was hard to pass them up. I suspect a customer had them and blew out one tweeter and decided to unload them to A.K. for an upgrade and Audio King put one new tweeter in them. I double checked the one tweeter that seemed hooked up backwards and sure enough it has a date sticker on it from January 1993 so this one was not original to the speakers. Anyways I am confident I have the polarity on the new tweeters correct now.

Often drivers are wired in opposite polarity. Second order half section crossover frequently have a 180 phase shift, and if you don't reverse polarity of one of the drivers you get a null at or near the crossover frequency.

If you found them wired out of phase, then more likely than not, that is the way they are supposed to be wired.

 

[59ctd]

Often drivers are wired in opposite polarity. Second order half section crossover frequently have a 180 phase shift, and if you don't reverse polarity of one of the drivers you get a null at or near the crossover frequency.

If you found them wired out of phase, then more likely than not, that is the way they are supposed to be wired.

OK, you completely lost me with that one. Would it be just the tweeter hooked up reverse if that was the case here or both the tweeter and the low freq drivers?

 

[ryanosaur]

Often drivers are wired in opposite polarity. Second order half section crossover frequently have a 180 phase shift, and if you don't reverse polarity of one of the drivers you get a null at or near the crossover frequency.

If you found them wired out of phase, then more likely than not, that is the way they are supposed to be wired.

One was different from the other, though.

 

[ryanosaur]

OK, you completely lost me with that one. Would it be just the tweeter hooked up reverse if that was the case here or both the tweeter and the low freq drivers?

Ha. We posted at the same time.
Were both Tweeters wired the same, or different?

Above, it sounded like one tweeter was wired different from the other, unless I misread.

 

[ryanosaur]

Ha. We posted at the same time.
Were both Tweeters wired the same, or different?

Above, it sounded like one tweeter was wired different from the other, unless I misread.

Please, this is where absolute clarity and precision of description is an imperative.

 

[59ctd]

Ha. We posted at the same time.
Were both Tweeters wired the same, or different?

Above, it sounded like one tweeter was wired different from the other, unless I misread.

Correct one had the tweeter with white to the + terminal and black to the - which I understand is reversed.

 

[ryanosaur]

Correct one had the tweeter with white to the + terminal and black to the - which I understand is reversed.

And the other?

 

[59ctd]

And the other?

the other one had black to the tweeter + and white to the tweeter -

 

[ryanosaur]

@TLS Guy is most likely the person to help you.

So the Tweeters were wired opposite each other.

You have a complete schematic? Does it show the proper wiring, or is your schematic just of the XO components?

Can you post it for out inspection, please?

 

[59ctd]

@TLS Guy is most likely the person to help you.

So the Tweeters were wired opposite each other.

You have a complete schematic? Does it show the proper wiring, or is your schematic just of the XO components?

Can you post it for out inspection, please?

Yes the tweeters were wired opposite polarity of each other.

The schematic I have is from @kevintomb on page two of this thread. When I worked on the XOs I recall the + input was hooked to the black wires and the - input was the white wires thus I figured white is neutral/neg and black is hot/positive.

 

[ryanosaur]

Yes the tweeters were wired opposite polarity of each other.

The schematic I have is from @kevintomb on page two of this thread. When I worked on the XOs I recall the + input was hooked to the black wires and the - input was the white wires thus I figured white is neutral/neg and black is hot/positive.

OK... Those drawings don't show the Driver Polarity, unfortunately.

Do you have REW and a measurement mic that you can run some sweeps with?

 

[59ctd]

I have the test mic that came with my Yamaha Aventage receiver and I believe it will tell me if the polarity is reversed. It never indicated reversed when I had hooked it up before me doing work on the RTA 11t main speakers years ago when the tweeters were opposite of each other but maybe that was because of the high vs low frequency. I know for certain the receiver has indicated to me when one of my two subs is out of phase with the other.

 

[TLS Guy]

I have the test mic that came with my Yamaha Aventage receiver and I believe it will tell me if the polarity is reversed. It never indicated reversed when I had hooked it up before me doing work on the RTA 11t main speakers years ago when the tweeters were opposite of each other but maybe that was because of the high vs low frequency. I know for certain the receiver has indicated to me when one of my two subs is out of phase with the other.

On the photograph of that high pass crossover you posted, it shows the white lead as going to the negative of the tweeter and the black to the positive terminal.

Your circuit shows a second order half section high and low pass filters. So that is why the black should go on the positive terminal as your photograph shows.

In this situations, Audyssey usually says there is an out of phase condition which ever way you wire it.

The reason is that the phase is only corrected at the crossover region, to avoid the cancellation null in the crossover region. The drivers are out of phase below and above the crossover region. They can't cancel in those regions as only one driver has output above and below the crossover region.

The trouble comes when you add a non matched center, and then you can get center and main drivers out of phase with each other. I have already run into that. This is particularly prone to happen, when you have two way mains and a three way center. I bet this happens far more often then is realized, and leads to poor integration.

I have found the best solution audibly, is to wire the drivers in phase and accept the null in the center response.

 

[Swerd]

@59ctd

Usually a driver's positive terminal is indicated by a + mark, a red dot, or the positive terminal is larger or wider than the negative terminal. Even if the terminals aren't clearly marked, you can find out which terminal behind the tweeter is positive and which is negative, with a AA 1.5V battery.

Use some tape to attach two 5-6" long wires to the battery, one to each end. Hold the wire attached to the negative end of the battery to one of tweeter's terminals, and briefly touch the wire from the positive end of the battery to the other terminal. If you've got the positive end of the battery touching the tweeter's positive terminal, the tweeter's dome will move forward with a pop. When you stop the connection, the dome will move back again. If you've got the positive end of the battery touching the tweeter's negative terminal, the tweeter's dome will pop backwards. Once you've figured it out, mark the tweeter's positive terminal with a red marker or nail polish. Be sure to do this for each tweeter.

Looking at the crossover schematic, I'm not certain if Polk intended for the tweeter to have the same or opposite polarity as the woofers. But I am sure they never meant one speaker to have it's tweeter with the same polarity as the woofers, and the other speaker with opposite polarity. The crossover schematic does look like a 2nd order filter. Usually, that means the tweeter's polarity should be opposite that of the woofers.

If it is a 2nd order filter, and Polk hooked up the tweeter with the same polarity as the woofers, that would explain the prominent dip in the frequency response of those speakers between roughly 1,500 and 4,000 Hz, centered at about 2,500 Hz. Reversing the tweeter's polarity should make it largely disappear.

There is about a 7 dB drop going from 1,500 to 2,500 Hz. You'll definitely hear a change that big. However, if your ears are used to hearing that, it may sound 'normal' to you. Reversing tweeter polarity will make it sound brighter at first. I think it's worth it. Getting the frequency response as flat as possible is better than a 7 dB suck-out, especially across the upper mid-range, where our hearing is most sensitive.