SDA 2B - Need Help Giving My Crossovers Some Love - Capacitors

PreCd

I have a set of SDA 2As that were upgraded to 2Bs many years ago. I am enclosing a picture of my crossover and hope that you all can step in and tell me what I need to get started in replacing the necessary components on the board. Thanks for the help in advance.

As soon as I posted this I saw the large post on 2B parts list below. That should do it except for one question. What is the t1 E-0012-1 12j100v big yellow thing in the middle of the board?

inspiredsports

That is the 12uf high pass capacitor.

When you say "upgraded to 2B's", do you know exactly what was changed?

Post #3 here contains your schematic . . .

http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array%28SDA%29

F1nut

12uF, 100 volt cap.

PreCd

They were originally 2As. Back in 1986 when I purchased them I was also sold a Yamaha R9 which these speakers ate alive. My tweeters kept shutting down due to the receiver not being able to drive the speakers. So the vendor took them in and replaced drivers to 2Bs and brought the boards up to 2Bs. Last month the Yamaha R9 died (Yey!) and I purchased a Adcom GFA-555 amp and 565 pre. Now my Polks are finally happy. I have so much going on with my system now though. The speakers sound pretty good. Better than with the Yamaha and I was tickled pink after a week of listening. But now I can see I need some improvements. One speaker is fuzzy at times in the highs depending on the music I play. My Cd player is crap so a new Marantz Cd5004 is on the way. I am recapping the Adcom gear. Whew! I have my hands full.

Thank you for the reply. Any other guidance in this would be welcome.

inspiredsports wrote: »

That is the 12uf high pass capacitor.

When you say "upgraded to 2B's", do you know exactly what was changed?

Post #3 here contains your schematic . . .

http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array%28SDA%29

PreCd

Thank you for the reply. Any guidance from you on this would be welcome. I am not able to go full bore and do the 2B TL mod but I would like to get whats in there up to date. So I know I need the cap below and 2 others, 20uf and 40uf. What type is that 12uf cap? What else do I need to replace what I have?

F1nut wrote: »

12uF, 100 volt cap.

PreCd

I am new to any crossover projects and the values and types of the capacitors have me stumped. From my schematic I can see that I will need the following capacitors (not able to do the 2BTL upgrade):

2 each 20uf capcitors
2 each 40uf capacitors
2 each 12uf capacitors

The 20uf and 40uf look like bipolar electrolytic capacitors to me. When everyone talks about replacing the capacitors I am gathering that Sonicaps is the leader and am willing to stick to that. Are we replacing electrolytic capacitors with another type when we go to the Sonicaps? Also when I looked at the Sonicap I could not find a equal value cap in the voltage listed in the schematic. I am looking at the link below:

http://www.soniccraft.com/sonicaps.htm

Now, what type capacitor is the 12uf capacitor?
Do I need the Mills Resistor and where does that go?

Toolfan66

Why can't you do the tl upgrade? your about 80% there with replacing the caps. the resistor is cheap the 5.8 cap is not that much. Well the tweeters will cost you about $90 bucks I guess..

Toolfan66

The resistor is that little brown tower to the left in your picture. You can get the 12uf cap from sonicraft as well as the mills resistor..

Toolfan66

You will use two 20uf in parallel to get your 40uf..

Toolfan66

I would also get a .01-.05 resistor and bypass that polyswitch or just bypass it with a piece of lead that you snip from one of the caps you install..

PreCd

Toolforlifean:

Thank you for the replies. I see the resistor and will replace that with the Mills.

Coins my man coins. That is what is stopping me from the 2BTL upgrade. If I do this little bit now soon I could do the rest. I believe I need to do that upgrade according to everyone's testimony.

I tried to remove the crossover by unscrewing the bolt that holds it in place from the back of the speaker. The bolt just kept turning. Is there a trick to getting those crossovers out that I am missing?

Can you answer my questions in post #6 where I asked about the specifics of the components used in my smaller upgrade?

heiney9

The fuzzy-ness might be caused by a worn poly-switch. A poly-switch is to protect the tweeter if it's over-driven, much like a fuse except it resets itself. As they aged and/or are tripped a few times they loose their effect and since they are in the signal path can degrade the output. If you are careful not to overdrive the speakers in the future they can be removed as Toolforlifefan suggested.

The poly-switch is the small blue square thing between the "yellow" cap and the connector on the board.

H9

PreCd

Yes sir I believe that is the case as these have been tripped quite a few times. The receiver I have had attached to these speakers, Yamaha R9, just could not drive them so they reset frequently. If no one is in the house I am usually a medium to high volume listener depending on the day. That little poly switch may need to stay for me. I am glad that you mentioned that as a possible cause. What are the specs on the poly-switch and where can I find one?

Thank you for your important and helpful advice.

Kevin

heiney9 wrote: »

The fuzzy-ness might be caused by a worn poly-switch. A poly-switch is to protect the tweeter if it's over-driven, much like a fuse except it resets itself. As they aged and/or are tripped a few times they loose their effect and since they are in the signal path can degrade the output. If you are careful not to overdrive the speakers in the future they can be removed as Toolforlifefan suggested.

The poly-switch is the small blue square thing between the "yellow" cap and the connector on the board.

H9

PreCd

I see where F1nut suggested that by removing the poly-switch and replacing that with a Mills .5 ohm 12 watt resistor it would significantly improve my sound. I think that removing it is too good to pass up so I will listen to that advice!

It is great to have people who know what it is going on to teach me what to do.

I would still like to hear an answer to my questions in Post #6. Thanks again to everyone who takes the time to share their wisdom. Great stuff.

Joe08867

PreCd, your answer to number 6 is you are correct. Looking at the pin blade 2b crossover schematic you need 2x12uf, 2x20uf & 2x40uf to do both crossovers.

May I suggest Sonicaps as well? They are really good in 2b's.

pitdogg2

PreCd wrote: »

I would still like to hear an answer to my questions in Post #6. Thanks again to everyone who takes the time to share their wisdom. Great stuff.

you can use all Sonicaps even for the electrolytics unless there're too big a value (i.e.130uf in the SDA2a)

the yellow 12uf cap is of mexican origin i believe maybe mylar but it doesn't matter you're going with Sonicaps which are very good poly caps. Most folks here have used them with very good results. I know it made a BIG BIG difference on my SDA2a's and SDA1 signatures.

inspiredsports

Jeff or Elliot at Sonic Craft (www.soniccraft.com) have helped dozens (perhaps hundreds) of us

They run 15% Off specials and may have one coming up soon or extend it to you just for the asking.

Caps are listed at: http://www.soniccraft.com/sonicaps.htm
Mills Resistors at: http://www.soniccraft.com/mills_resistors.htm

As someone posted above, you piggyback 2 20uF caps to get the 40uF value for the low-pass section of the crossover. You can go with a cheaper brand 40uF in the low pass section without as big a compromise as using lesser caps in the high-pass sectiion, but it IS a compromise you will probably regret later.

On the high-pass caps (12uF and 5.8uF if you TL) you can spend a lot more for just a few fractions of a percent gain, and you can spend a lot less but get almost zero improvement for your effort.

If you "TL" it adds the cost of 2 RDO198-1's from Polk for $48 each and the cost of 2 5.8uF caps from Sonic Craft @ approx $15 each, a total of $130 more. You will get something of that back selling your current tweeters here when you reach 100 posts.

All done, you can recap, add Mills (brand) resistors, and TL for about $325 (assuming the 15% off) and get back some money later for the pulled tweets, so net is under $300. Not TL'ing you are are approx $200. In my humble opinion TL'ing is the way to go.

Are the domes of your tweeters clear/yellowed/silver in color, or black?

PreCd

Pittdog2: Thank you for the info.

inspiredsports: That is great information and thanks for the details. I just love it when someone else spends my money! :biggrin:
All joking aside you have a valid point and if I do the upgrade I am sure to be happy. I am not happy now as the highs in these speakers, especially left, are not pleasing to hear.

My tweeters are the clear SL2000s:

Let me ask another question. Upon inspecting my drivers I found two of them on the right to have the middle pushed in a bit. Probably happened when my kids were little as I have not taken the grills off in some time. When I talked with Polk about that the fellow told me not to worry as that was only a dust cover and does not affect the sound. Before I start sinking money into the speakers I would like an opinion on this. Below is the area I am speaking of circled in white but this is not a actual pic of my driver:

Thanks,
kevin

Joe08867

The pushed in dustcap shouldn't cause any harm and if it real bothers you that much you can try to suck it out with a vacuum softly. Really though it isn't going to hurt the sound.

heiney9

You will definitely want to get a pair of the new silk dome tweeters RD0194-1 if you are NOT TL'ing the xover. If you TL the x-over you MUST get the new silk dome RD0198-1 tweeters. The SL2000 tweeters don;t age well. They didn't sound great new and they degrade overtime.

H9

pitdogg2

Joe08867 wrote: »

The pushed in dustcap shouldn't cause any harm and if it real bothers you that much you can try to suck it out with a vacuum softly. Really though it isn't going to hurt the sound.

Been there done that it works. But you want to use the nozzle and have someone else hit the on/off button while you hold the driver and nozzle. Just put the nozzle over the dustcap have the other person turn on then right back off. Do not try and move the nozzle while it is on. What you do not want to do is try and pull off the nozzle while the vacuum is on you could pull the driver too far out and ruin the driver. That is why you hold the driver to keep from pulling voice coil out of position. BE CAREFUL FWIW DO NOT USE A SHOPVAC unless it is the tiny 1 gal.model all others will be to strong of suction and you need the nozzle to be the same size as the dustcap.

Even if it's completly pushed in it well have no affect on the sound it's just there to keep stuff out of the VC motor assembly

inspiredsports

As much as the caps in a 1986-1988 speaker are crying to be replaced, your first 2 X $48 should go to new tweeters. If you only had $100 to spend, I would replace the tweeters before doing the caps/resistors, but in reality you HAVE TO DO the crossovers.

The rub is RDO194-1's (exact SL2000 drop-in replacements) and RDO198-1's ("TL" requiring the 5.8uF cap) tweeters all cost 2 X $48.

Now you are only the 2 X $15 5.8uF capacitors different in your two restoration scenarios (my post #17 above), and SL2000's still for for from 25-$40+ per pair on the secondary market.

So now it becomes a mission to find the $300 and go to town on those bad boys



WARNING: If you do this and like what you hear, it will soon be the year 2015 and you will be looking back at the $7-40K you happily poured down the rabbit hole this hobby will have become for you.

PreCd

I like the scenario where I upgrade the tweeters to the 198s and install the 5.8uf cap, removing the poly switch and putting the Mills resistor in. How would that work in the interim?

inspiredsports wrote: »

As much as the caps in a 1986-1988 speaker are crying to be replaced, your first 2 X $48 should go to new tweeters. If you only had $100 to spend, I would replace the tweeters before doing the caps/resistors, but in reality you HAVE TO DO the crossovers.

The rub is RDO194-1's (exact SL2000 drop-in replacements) and RDO198-1's ("TL" requiring the 5.8uF cap) tweeters all cost 2 X $48.

Now you are only the 2 X $15 5.8uF capacitors different in your two restoration scenarios (my post #17 above), and SL2000's still for for from 25-$40+ per pair on the secondary market.

So now it becomes a mission to find the $300 and go to town on those bad boys



WARNING: If you do this and like what you hear, it will soon be the year 2015 and you will be looking back at the $7-40K you happily poured down the rabbit hole this hobby will have become for you.

PreCd

Thank you Pittdog and Joe for your response about the pushed in dust cover. I run with the grills on so out of sight out of mind!

inspiredsports

PreCd wrote: »

I like the scenario where I upgrade the tweeters to the 198s and install the 5.8uf cap, removing the poly switch and putting the Mills resistor in. How would that work in the interim?

You could certainly do that step first, and the more expensive big caps later. The images in post #54 might help where the paralleled 5.8uF capacitor and 2.7 ohm resistor are shown at the far left in capacitor position "C5" on the board:

http://www.polkaudio.com/forums/showthread.php?74945-SDA-2B-Crossover-Parts-List/page2&highlight=SDA+crossover+parts+list

PreCd

What is the purpose for using the resistor in parallel with that 5.8uf capacitor?

PreCd

Joe thank you for the information. I will use the Sonicaps for whatever I do on this project!

Joe08867 wrote: »

PreCd, your answer to number 6 is you are correct. Looking at the pin blade 2b crossover schematic you need 2x12uf, 2x20uf & 2x40uf to do both crossovers.

May I suggest Sonicaps as well? They are really good in 2b's.

PreCd

Ok so here is what I am going to do. I am going to upgrade to the RDO198-1 tweeter and install the 5.8uf cap and 2.7ohm Mills resistor. Here are the steps I will take:

1. Remove existing 2.7 ohm resistor. ( Do I need to strap anything?)
2. Install 5.8uf Sonicap capacitor.
3. Install 2.7ohm Mills resistor in parallel with 5.8uf Sonicap capacitor.
4. Remove poly-switch and install strap.
5. Install new RDO198-1 tweeters. Install new blades to both wires to allow for the size different in SL2000 and RDO198-1 connections.

Does that sound like it?

This will help me out I think until I can get the other caps for the full capacitor upgrade.

inspiredsports

PreCd wrote: »

What is the purpose for using the resistor in parallel with that 5.8uf capacitor?

The resistor controls how much energy reaches the tweeter in relation to how much reaches the 6.5" mid/woofers. The 5.8uF cap filters out certain frequencies the tweeter does not properly reproduce.

PreCd

Thank you for the lesson inspiredsports. It helps me if I learn what the purpose for the replacement is for. In the picture below taken from http://www.polkaudio.com/forums/showthread.php?66784-Photos-of-the-upgrade-for-the-SDA-2Bs&highlight=2BTL the resistor is placed in hole R2 and hole C. Is this acceptable?

audiocr381ve

PreCd wrote: »

Thank you for the lesson inspiredsports. It helps me if I learn what the purpose for the replacement is for. In the picture below taken from http://www.polkaudio.com/forums/showthread.php?66784-Photos-of-the-upgrade-for-the-SDA-2Bs&highlight=2BTL the resistor is placed in hole R2 and hole C. Is this acceptable?

Why is the polyswitch jumper at the 12uf position? That's not right.