SDA-2B Crossover Parts List

[inspiredsports]

I'm buying the parts to have my SDA-2B Crossovers rebuilt by a friend in the group.

The caps are easy and I believe going with 12u Sonic's for the highs (www.soniccraft.com 20% off in November), and then Dayton's for the lows (20u and 40u www.partsexpress.com) will be OK. Is there a reason to use the much more costly Sonics for the 20 and 40u's ???

I've found the original 2.7 Ohm 10% 5W resistor in a 2.7 ohm 10% 10W "audiophile" version from parts express. Is the wattage increase OK ???

Last, in the image below there are two "white circled" parts (bottom center of the board).

The light blue one (resistor?) shows "MCI 500" and the dark brown/black (polyswitch/thermistor??) shows SAN Mexico 1000 50%).

Can someone educate me as to the proper name and function of the circled components, and as to what their function is? Last, do these circled components need to be replaced?

Thanks,
Greg

[ben62670]

dark brown/black is the 750pf bypass. Just remove it.
The light blue thing is the Poly switch. Bypass it.
An increase in watts is fine. Use an audio grade resistor such as the Mill's or the Dayton Audio grade.

[zingo]

Those resistors are the sandblock ones and I wouldn't suggest them. The only resistors that are x-over worthy at PE are the 12w Mills. Mundorf are also very good from Madisound.

The little blue thing is the polyswitch, and that can be removed if you want or are having problems with it, and the black cap is probably a bypass, but I would need to confirm that.

[ShinAce]

Those resistors are the sandblock ones and I wouldn't suggest them. The only resistors that are x-over worthy at PE are the 12w Mills. Mundorf are also very good from Madisound.

The little blue thing is the polyswitch, and that can be removed if you want or are having problems with it, and the black cap is probably a bypass, but I would need to confirm that.

Confirmed!

Can't remember the material type for that cap though and somehow that bugs me.

p.s. They're rarely black. It's more of a purplish brown.

[gdb]

While doing the 2Bs, are you also doing the "TL" upgrade to allow the use of the RDO-198 tweeter. or are you staying with the 2000s or adding RDO-194s? Does the TL mod require different caps & resistors than a standard rebuild??Geoff

[ben62670]

The 3000/198 mod requires that you parallel a 5.8uf cap with the 2.7r resistor. That's it:)

[MillerLiteScott]

The TL upgrade is what really makes the 2B shine. The only extra cost is the 5.8 Uf cap and the tweeters which you should do any way.

Scott

[inspiredsports]

Clarifications:
-- I have the SL2000 replacement RDO-194's already on the way so it sounds like I should be OK with the "stock value" replacements.
-- What I described as "black/brown" could easily be described as "purple/brown" under other light sources. It says "1000" so I'm confused as to how it is 750pf?
-- I'm still not sure if I should try to save money by using Dayton's for the lows.
-- It seems most feel the Mills brand resistors have the best reputation within the group so I'm going to try to find those.

[inspiredsports]

Now you have me thinking. What is the difference in price of the RDO-194 and 198? I wonder if I can immediaely send the 194's back to Polk before opening them? I'll call Polk on Monday.

[Disc Jockey]

Same price for either one. I don't know Polk's return policies, but Polk CS can be described as exceedingly generous without exaggerating.

[inspiredsports]

zingo mentioned Mundorf brand "Metal Oxide Film Resistors" ($2.50 each) found at www.madisound.com, and many seem to like the Mills "Non-Inductive Wire Wound Resistors" found at www.parts-express.com ($3.75 each).

Is there a noticeable difference in the way they sound?

[Face]

Yes, IMO the Mundorf resistors have little to no coloration. Mills give a warmer sound, which you may or may not prefer.

[inspiredsports]

Ben, if adding the 5.8uf capacitor for the RDO-198, what type (film, poly, electrolytic) is it?

Is it "piggybacked" with the 2.7 (or 2.5) ohm resistor or put in the "C5" space on the board?

[inspiredsports]

Yes, IMO the Mundorf resistors have little to no coloration. Mills give a warmer sound, which you may or may not prefer.

I think I prefer a warmer sound so I'll go with the Mills

[Face]

Ben, if adding the 5.8uf capacitor for the RDO-198, what type (film, poly, electrolytic) is it?

Is it "piggybacked" with the 2.7 (or 2.5) ohm resistor or put in the "C5" space on the board?

The capacitor is added in parallel with the resistor. Use a Sonic Cap there since it's also in the HF circuit.

[inspiredsports]

It looks like Sonic lists a 5.6uf / 200VDC, but not a 5.8. Is this OK?

[F1nut]

When doing the 4.1TL upgrade using the 5.8uF cap, put one end in the hole marked "H" and the other in the top C5 hole. If you don't do this, it isn't going to function properly.

Sonicap's make fantastic shunt caps. I highly recommend them for the 20uF and 40uF. Note, for the 40uF, get a 10uF and a 30uF as Sonicap doesn't make a 40uF. You have to mount the 10uF under the board and there's no room for a 20uF. You mount the 30uF up on it's end on the top of the board.

Ask Elliot to custom value the 5.8uF's.

The 4.1TL upgrade is well worth doing as it seriously outperforms just upgrading the crossover parts using the RD0194-1 tweeters.

Make sure you replace the polyswitches with jumpers.

[F1nut]

Just looked at your pic. You'll find the "H" hole off to one side of the small inductor, so you'll have to move the inductor over a bit. No biggy really.

[inspiredsports]

I'm not well versed enough to know what the technical difference may be, but I think my ears are "smart".

I was thinking of using the less expensive Dayton's on the low side, but you prefer the more expensive Sonics all the way around. Can you "hear" a difference in the bass using the 20 and 40 (10 + 30) Sonics?

[F1nut]

If your ears are smart, get the Sonicap's. Keep in mind that it will take anywhere from 200 to 400 hours to burn in. Don't judge the sound until then.

Follow my directions above. I was the first to do this mod and worked out all the bugs.

[inspiredsports]

Sorry for so many questions.

When Piggybacking to get 40uf, what ar the pros and cons of (20 + 20) versus (10 + 30) ??

I understand the possible size issue to fit a board, but is there an electronic issue if size doesn't matter?

(Yeah, guys, I KNOW SIZE MATTERS).

[F1nut]

It would be better to have the split as even as possible, but the 30 & 10 will be fine. What you really don't want is something like a 39 & 1.

In retrospect, with the 2B's you actually can use two 20uF's. The bottom 20 will kinda hang off a bit, but will be fine. Use hot glue and a zip tie to hold it in place. I had to use a 30 & 10 when I did the CRS+ upgrade to the 4.1TL because of the tight quarters inside the cabinet, you don't have that problem. Before you ask, yes the CRS+ pin/blade crossover is the same as the 2B pin/blade, so you can perform the 4.1TL upgrade even though it was designed for the CRS+. This upgrade can also be performed on the 2B blade/blade model.

BTW, I believe we've dubbed the 2B upgrade, the 2B TL.

[inspiredsports]

Thanks, I searched "2B TL" and found nothing, but "2BTL" with no space yelded paydirt at the link below!

http://www.polkaudio.com/forums/show...highlight=2BTL

You're right that room is not an issue in the 2B so all can be mounted on top of the board. I think I'll go 20+20 to fill the 40uf spot.

[inspiredsports]

So here is my final parts list for my SDA-2B mods:

I based it upon the great information I got from the group in just a matter of hours. I interjected my personal choice of using the Sonic 2.7 ohm 12W Non-Magnetic, Non-Inductive Wire-Wound Mills Resistors that might introduce a "Warmer" sound versus the Mundorf 2.7 ohm 10 W Metal Oxide Film Resistor that feature a "cooler" sound, introducing less "coloration" to the source sound.

I elected to upgrade the factory SL2000 Silver Coil Tweeters not with the standard RDO-194 replacement, but with the RDO-198 (which replaces the SL3000). The RDO-198 causes the need for the addition of the 5.8uf Cap to the circuit (Special Order from Sonic Draft) in conjunction with the 2.7 ohm Mills Resistor.

I also elected to dampen the spokes of the 6.5" drivers and 12" passive radiator using Dynamat Extreme.

The finishing touch will be a modest speaker wire binding post upgrade.

################################################## ###

2 EACH - RDO-198 Polk Tweeters @ $48.00 ea. = $ 96.00

################################################## ###

ELECTRONICS: ALL Sonic Craft
2 EACH - 12.0 uf Sonic Caps @ $20.85 ea. = $ 41.70
2 EACH - 20.0 uf Sonic Caps @ $28.60 ea. = $ 57.20
4 EACH - 20.0 uf Sonic Caps @ $28.60 ea. = $ 114.40 (Piggybacked to replace the stock 40uf)

2 EACH - 5.8 uf Sonic Caps @ $12.90 ea. = $ 25.80
2 EACH - 2.7 ohm Sonic Mills @ $ 3.85 ea. = $ 7.70

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 246.80

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

################################################## ###

Dynamat Extreme 10425 Xtreme Wedge Pack
1 Sheet (18" x 32"): $17.99 + $6.47 S&H = $ 24.46
http://www.amazon.com/exec/obidos/AS...bsitementcommu

################################################## ###

Dayton BPP-SN Premium Binding Post Pair - Satin Nickel
http://www.parts-express.com/pe/show...number=091-624
$13.00 blk/red pair (was $23.99) $ 26.00
(nonrelated stuff got free S&H w/purch over $49)

################################################## ###

TOTAL COST OF UPGRADE PARTS $ 393.26

Again, THANKS TO ALL IN THE GROUP for your great help !!

P.S.: Hi resolution wrap-up photos will follow when mods are complete

[Face]

You will be more than pleased. I also completed the TL mod to my 2B's and was pleasantly surprised.

[MillerLiteScott]

I have also done this mod and it is an excellent mod. It took my crossovers at least 400 hours to burn in and I still noticed some improvement (even warmer/creamy top end) about 2 months after that with after normal listen.

I do not know what speaker wire you are using but I had just as dramatic improvement as the crossover upgrade by installing a pair of MIT Shotgun S3 speaker interface cables.

Watch you wallet on this forum.:D

Enjoy,

Scott

[F1nut]

Eh, we have a finicky search engine.

By lack of room, I meant inside the cabinet. You will not have room to mount two 20uF caps on top of the board.

Just looked at the link you posted. DO NOT mount your 20+20 like that. Mount one upright and the other under the board. Hanging caps off the ends to that extreme is bad juju.

May I also suggest that you get some gold plated binding posts from SonicCraft. Vampire, Cardas or WBT.

[inspiredsports]

So to be clear, you fell that it is best NOT TO CANTILEVER the piggybacked (30+10) or (20+20) in the 40uf spot as seen in the first image at http://www.polkaudio.com/forums/show...highlight=2BTL

In an earlier post, you wrote . . .

. . . note, for the 40uF, get a 10uF and a 30uF as Sonicap doesn't make a 40uF. You have to mount the 10uF under the board and there's no room for a 20uF. You mount the 30uF up on it's end on the top of the board . . .

I'm afraid I don't have enough room under board to squeeze in a 10uf (30+10), let alone a 20 (in a 20+20 configuration).

There are nylon 4 pins that hold the board to the large 4" diameter coil and those pins provide about a 1/2" rise, way LESS clearance than the thickness of a 10uf, let alone a 20uf.

I think I need to keep the modded caps on top, or find 8 (4 each cabinet) much taller nylon pins/risers. This pin seems to be a really specialized part that I'm afraid I may never locate in a "taller" version.

Now, remembering the board is mounted paralell to the vertical back wall of the cabinet, the 30uf standing on end in your preferred method is still cantilevered out a huge amount toward the front wall of the cabinet. I'm not certain there is any difference in the leverage the hanging cap exerts on the solder joints.

Also, either way, the caps will rest on the large coil on the board just below the 40uf mounting location, maybe even helped with a bit of holt melt glue. There must be a way to handle both caps on top without violating good circuit design form.

[ben62670]

Look at the top right corner. All you need to do is drill a small hole just large enough to pass the cap lead through(red dot). Have your glue gun ready to glue the caps securely in place. Once the lead is through attach it to the puddle of solder on the outside edge of the board. You will need to use a short piece of wire to extend the caps top lead to the original caps lead hole on the left of the cap.
Ben

[inspiredsports]

That's inventive, in great form, and I LIKE IT !!!