SDA-2A Crossover Upgrade

bcline · March 2009

I just joined the forum though I've owned a set of Monitor 5bs for 20 years and numerous inwall's and surround speakers for the whole house audio. I just recently purchased a set of SDA-2As and think I might be interested in upgrading the crossovers.

I know there has to be a thread somewhere for that speaker's upgrade, but I sure haven't been able to find it... maybe I suffer from search engine deficiency syndrome. Could someone help direct me as to what I need to do for this upgrade or give me the lowdown on how to do it and what parts I would need to purchase? I have not torn into them yet, but assume they have the original drivers. Is the crossover mod worthwhile with the old drivers or is it essential to get the newer drivers for the speaker. Thanks.

NJPOLKER · March 2009

Welcome to the Forum
If I were you I'd take some pictures of your speakers and post them here.
The pictures should be of the fronts and backs, and of the x-overs. This way everyone will know what we are working with. With good pictures its a lot easier to assist you with upgrades.
If pictures are not going to happen then we'll try another way. Do they have two drivers, one tweeter and one passive sub?

zingo · March 2009

The crossover mod is worth while and will give you years of great listening.

SDA 2A schematics: http://www.polkaudio.com/forums/showpost.php?p=677948&postcount=3

SDA 2A parts list: http://www.polkaudio.com/forums/showpost.php?p=921621&postcount=4

Disc Jockey · March 2009

It can be done by itself but it's best in combination with the replacing the existing tweeters with the upgraded RDO194 tweeters.

As far as the parts list goes, most people will opt not to replace the inductors, just the caps and resistors.

bcline · March 2009

Thanks for the help so far... I will tear into it and get pics together. I do know that they are really 2As. I have noticed many favor upgrading the SL2000s to the RDO194s I haven't really felt the "harshness" of the SL2000s in my monitor 5bs over the years, but then again, I have been diagnosed with a slight hearing loss in the high frequency ranges, so that might not make it sound as harsh. I might check into those as well for my SDAs and M5b set.

It would seem many on the forum favor the Sonicaps, are they considered the best for the money by most everybody or is this one of those "everybody has an arguable opinion" things? I've noticed most seem to be migrating with sonicaps, dayton, and solen. Is there any huge difference in these brands?

NJPOLKER · March 2009

I've noticed most seem to be migrating with sonicaps, dayton, and solen. Is there any huge difference in these brands?

Sonicaps are a step or two above Solen and Daytons in most peoples opinions. I agree and would use Sonicaps or higher grade caps in the high pass and Solens in the low pass.
Just don't forget that the new caps are much bigger than the OEM caps no matter which caps you choose. Also you should order some Cardas solder when placing your order with Sonic Craft.

Disc Jockey · March 2009

NJPOLKER wrote: »

Sonicaps are a step or two above Solen and Daytons in most peoples opinions. I agree and would use Sonicaps or higher grade caps in the high pass and Solens in the low pass.

Agreed, although my personal preference is the Dayton 1% in the low pass due to the tighter tolerance.

I can't imagine the price or size of 2 130uf Sonicaps in that low pass :eek:

bcline · March 2009

Couldn't even find the 130s in Sonicaps... only Solens @ about $44.00 each. Need 4 for the two speakers. If I go with Sonicaps for the other two sets I'm up to about $300.. Youch, I hope this is worth it! That's as much as I paid for the speakers.

ben62670 · March 2009

Solens suck. The Dayton 1% are not worth the extra dollars. The 5% are real tight. Don't worry about it. The stock Polk caps are 20%.
Ben

Systems · March 2009

bcline wrote: »

Couldn't even find the 130s in Sonicaps... only Solens @ about $44.00 each. Need 4 for the two speakers. If I go with Sonicaps for the other two sets I'm up to about $300.. Youch, I hope this is worth it! That's as much as I paid for the speakers.

I know Im in the minority but I would use Bennic low ESR bipolar electrolytics for the shunt caps in the low pass section.Or alternatively use one bipolar and one film cap.

IMO throwing so much of your budget at film caps for this part of the circuit will not offer big improvements for the amount spent.By all means get the best film cap you can afford for the hi pass section, but for the shunt cap across the woofer, it is it's value that is most important not the dielectric material it was made of.

ben62670 · March 2009

GV#27 wrote: »

I know Im in the minority but I would use Bennic low ESR bipolar electrolytics for the shunt caps in the low pass section.Or alternatively use one bipolar and one film cap.

IMO throwing so much of your budget at film caps for this part of the circuit will not offer big improvements for the amount spent.By all means get the best film cap you can afford for the hi pass section, but for the shunt cap across the woofer, it is it's value that is most important not the dielectric material it was made of.

Well everyone knows I love GV, but I must say that film caps as shunts do offer substantial gains over electrolytic. GV are we still friends? BTW bennic's are Dayton's as far as I know...

Systems · March 2009

ben62670 wrote: »

but I must say that film caps as shunts do offer substantial gains over electrolytic.

Thus my reason for the IMO.I guess we disagree on this point.;)

GV are we still friends?

Absolutely not.:D

bennic's are Dayton's as far as I know...

Bennic manufacters Daytons film caps I believe.

ben62670 · March 2009

GV#27 wrote: »

Thus my reason for the IMO.I guess we disagree on this point.;)

Yeah I have tried many different combos(trying to save money), and I feel the shunts matter less than pure signal path caps, but I have found shunts are not to be dismissed. Teacher:)
Cheers
Ben

Systems · March 2009

ben62670 wrote: »

Teacher:)
Cheers
Ben

That was uncalled for.I stated it was my opinion.

ben62670 · March 2009

GV#27 wrote: »

That was uncalled for.I stated it was my opinion.

Dude seriously I have learned more from you than many others here. You have been a wealth of knowledge

Systems · March 2009

Sorry Its late , I guess I'm reading things the wrong way.

bcline · March 2009

OK guys... remember I'm new to this. I do have a little knowledge of circuits, but I'm losing you on which caps are the shunt caps. In looking at the crossover circuit diagram, I see a 20 uF cap in parallel with each of the 6510 drivers. I see a pair of 130 uF caps parralled with each other and in series with the dimensional 6510 driver. Are these the shunt caps you are referring to?

Also I noticed there is a 750 pF (0.000750 uF) cap in parallel with the 12uF cap on the high pass end. Is that also an important one to replace? In essence, which caps should I absolutely replace here and should I go with film or bipolar electrolytic? I know...everybody has a different opinion, but I really want to know these opinions.

One last thing... Is it important to replace the resistor as well on these speakers? Do the mills resistors add much over the generic one that polk installed?

BTW I was thinking that Bennics must be Daytons... they look exactly alike down to the colors.

Thanks... I'm learning!

ben62670 · March 2009

Drop the 750pf. Just simply remove it. The caps that go from positive to negative are shunt caps. These are the less important ones (20uf's). The 12uf cap is the most important cap in this speaker. The 130uf caps unfortunately are in series with the signal. It is only for the cancellation signal so opinions will vary. They are important:( Replace the resistors with Mills 12 watters;)

bcline · March 2009

Thanks for the clarification Ben... now that you say it.. duh, obviously the 20 uF caps are shunts. My brain ****.

So, if I'm replacing the 130s... the only ones I have found with that capacitance has been Solen... anybody know if I can get anything but Solens at this level?

NJPOLKER · March 2009

try partsexpress.com and look for Dayton capacitors

NJPOLKER · March 2009

http://www.parts-express.com/crossover-capacitor-index.cfm

here is a link

bcline · March 2009

That's where I've been looking. Daytons only go to 100uF as do all the others except Solen.

Disc Jockey · March 2009

If you're going to order the sonicaps for the high pass, ask them what they have. They have a line there that they do not have listed on their website but they have them available for those higher values. I forget what the brand name was but they were pretty reasonable price-wise.

Systems · March 2009

ben62670 wrote: »

The 130uf caps unfortunately are in series with the signal.

bcline · March 2009

Thanks GV... I was looking to see if I might be able to replace the 2 parallel with a single... Obviously, Polk was just trying to make a 260 uF capacitor with them.

I'm just going to throw this out there. Some have suggested that bipolar electrolytics might be OK for the low pass. These obviously are much cheaper and I still expect the electrolytics I'm seeing at parts express are probably better than what came with the speaker. Your thoughts? I'm looking at these film capacitors above 100uF and wonder if they will even fit.. they are huge!

NJPOLKER · March 2009

bcline
Ben didn't mean what he said about the Solens.
You will have to make up the 130uF value by using a two caps tied together.
If I were you I'd go the way GV says in the above post. And Solens don't suck.

Thats for the link GV I may buy a couple myself

Disc Jockey · March 2009

That's a pretty good deal on those Solens, and probably your best bet.

Make sure you dry fit everything before you start soldering and gluing.

bcline · March 2009

ben62670 wrote: »

Drop the 750pf. Just simply remove it. The caps that go from positive to negative are shunt caps. These are the less important ones (20uf's). The 12uf cap is the most important cap in this speaker. The 130uf caps unfortunately are in series with the signal. It is only for the cancellation signal so opinions will vary. They are important:( Replace the resistors with Mills 12 watters;)

I was trying to figure out what the purpose of the 750 pF cap is. Simply adding 0.000750 uF to 12 uF seems a little strange. Especially when you have 5% tolerences at best. Any idea what the engineers were thinking with this one? Do they know something we don't here?

NJPOLKER · March 2009

If you plan on going with the Solen 270uF's you better hurry. They only have 2 left at that price, I just bought the 2 for my 2a's.
Thanks again GV

NJPOLKER · March 2009

bcline wrote: »

I was trying to figure out what the purpose of the 750 pF cap is. Simply adding 0.000750 uF to 12 uF seems a little strange. Especially when you have 5% tolerences at best. Any idea what the engineers were thinking with this one? Do they know something we don't here?

Nobody knows more than the guys around here.

Systems · March 2009

bcline wrote: »

I was trying to figure out what the purpose of the 750 pF cap is. Simply adding 0.000750 uF to 12 uF seems a little strange. Especially when you have 5% tolerences at best. Any idea what the engineers were thinking with this one? Do they know something we don't here?

It is a bypass cap and its purpose is to improve the hi frequency response of the 12uf.Little caps charge and discharge quicker than big ones.It may have helped the stock cap but it's not necessary with better film caps available today.

SDA-2A Crossover Upgrade

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