SDA SRS 2 Crossover Parts list

inspiredsports

ben62670 wrote: »

That would be just fine, or the brace above. You can use any type of open cell foam to pad those huge caps;)

Thanks Ben,

I'm curious why you mention the brace above as it seems that would be messy running the wires over the high-pass that mounts in the open hole shown. I'm leaning heavily toward the side of the triangular brace.

BTW, thanks for your help with the mods!

ben62670

Just offering a second idea that may not have been seen without the pic:)

inspiredsports

Mounting the large (100+82=182uf) Aeon caps on the brace went smoothly. 2 small holes, some open cell foam underneath and wrapped up the back side, and some cable ties cinched down tightly.

I'm wondering if the ties will eventually loosen up due to vibration, but being pulled down into the foam seems like it will keep tension indefinitely.

I rotated the low pass cap boards 180 degrees to put the 2 stacks of 2X17=34uf caps more into the "taper" of the passive radiator which added small bit more clearance. There was 1-3/8" with the factory caps, and is now at a hair over 1".

Lots of new caps in there that I'm DYING to start burning in!

ben62670

I knew it was going to be tight, but those diagrams were top notch;)

inspiredsports

These SDA SRS 2's use 4 identical MW6509's in each cabinet, 2 for main Stereo and 2 for SDA Effect.

I had to replace 4 with the new replacement version from Polk Customer Service.

I've heard mixed reviews with many stating the old drivers are favored over the new.

My original thought was to use the new MW6509's for the Stereo side, and the old originals for the SDA side.

Does anyone have any thoughts on location before I start assembly? Originals are photo on the left, and new on the the right.

inspiredsports

ben62670 wrote: »

I knew it was going to be tight, but those diagrams were top notch;)

I did have to nip off a tiny bit of the tip of one of the 4 nylon spacer/fasteners on each board so it wouldn't put pressure on the new caps, but it's all good now.

ben62670

Yeah I saw that, but I was thinking you could press it in at a bit of an angle. It is on the bottom now so no worries.

inspiredsports

Any thoughts about position of old vs. new from my post #36

heiney9

inspiredsports wrote: »

Any thoughts about position of old vs. new from my post #36

Make sure the screw holes in the baskets of the new drivers are free of excess rubber from the surrounds. That was an issue a year ago or so. If you don't trim (or the factory hasn't trimmed) the excess from the holes you will deform the surround once installed.

I have no idea about how you should configure the old and new drivers. I'd split them up between L & R cabinets...........but beyond that not sure it really matters.

H9

P.s. Later SRS 2's have different drivers for the regular and dim circuits.

inspiredsports

heiney9 wrote: »

Make sure the screw holes in the baskets of the new drivers are free of excess rubber from the surrounds. That was an issue a year ago or so. If you don't trim (or the factory hasn't trimmed) the excess from the holes you will deform the surround once installed.

I have no idea about how you should configure the old and new drivers. I'd split them up between L & R cabinets...........but beyond that not sure it really matters.

H9

P.s. Later SRS 2's have different drivers for the regular and dim circuits.

Good call. I'm right at that point and the drivers they sent me, as you might have been able to see in the photos, are made with the rubber covering about 75% of the screw holes. I think I can notch them like the originals with an Exacto knife, but I'm not very happy having to do this mod.

I think I'm going to use 2 each of the 4 new drivers as the inner (main stereo) pair, and the old drivers as the SDA effect sets.

These are going to be tweaked about as much as possible when I'm done and I sure hope they sound as good as the newer 2.3 and 2.3TL sets that split the duties with various combinations of (I believe 8 ohm) MW6511/MW6513 and MW6510 drivers.

I think will like this original SDA SRS 2 with MW6509's as they are 4 ohm speakers that will pull a little more sound out of my NAD Amps.

inspiredsports

I've held off posting for as long as possible, but couldn't resist today. I'm only 110 hours in on these SDA SRS 2's, but these speakers are opening up magnificently . I have been furiously switching Amps, IC's and Cables back and forth with my SDA-2B's also recently rebuilt and now at just over 300 hours for clear comparisons.

The SDA SRS 2's are on a 20' wall in a 20X28' acoustically good room dedicated to my 2 channel rigs. The cabinets are 7" from the back wall, 4' from each side wall and 10' apart center to center (8', 2" center gap). My listening position is absolutely ideal with my leather recliner dead center and ears at 8', 2" back from the front centerline. My ears are 41" off of the ground which by coincidence is the exact height of the center-line between the 2 vertically stacked RDO194-1's in each cabinet.

My first comment is that the original SRS 2's that I have (1986 4 ohm with all MW6509 6-1/2") love to be turned up, but the volume is not apparent. I was listening in the dark to my recently acquired Dark Side of the Moon SACD and kept turning up the volume. I had set up my Extech db meter to capture maximum the maximum db level reached at my listening position and was stunned to see 106db when I turned the lights back on. The speakers never even strained or sounded loud. I need to be careful here so I can hang on to my hearing a few more decades.

Going back just 100 hours ago to minute 1, these speakers sounded horrible, had nothing a 6,000 Hz, nothing below 120 Hz and no soundstage. Today, the tweeters just continue to sweeten and the bass is all there (which makes sense as the caps are Aeons and everything is Dynamatted and Mortited). As far as the new tweets and high pass goes, I've literally been able to hear the soundstage creep from just inches to the left and right of each cabinet to a full 5 feet down the left and right wall. I was listening to Genesis "The Lamb Lies Down on Broadway" double CD this morning with my eyes closed and trying to pinpoint apparent sound sources. Some were close to even with my ears, a full 8 feet forward and coming out of the side walls (and my only drug of choice is a couple of cups of caffeine).

What's been amazing is the day by day improvement. I've literally been able to listen to the soundstage creep inch by inch down the sidewalls, and open up also from ceiling to floor.

The MIT AVt-2 IC's and Speaker Interface Cables are part of this mix too as they only have about 160 hours on them, but I burned them in mostly with the 2B's and had not been noticing much of a change after 100 hours. However, the 2B's are not a perfect control speaker as they are probably need about 100 more hours to be completely cooked (All Sonicaps). The stellar sound coming out of 2B's will be covered in another thread. I can say that I judge the AVt-2 upgrade probably is responsible for 30-40% of the soundstage imaging improvement. MIT says improvements happen after 48 hours and after 336 hours so I'm only half way to nirvana.

At any rate, if these SDA SRS 2' continue to keep getting better (as the Sonicaps in the high-pass are said to do for up to 400 hours), I will soon be bankrupt. My home office in my listening room. With these speakers on 24/7, the sound pulls me way from my computer and into that easy chair. I've been in my office for almost seven hours today, and pulled away by the music at least half of that time :eek:

On last comment. I have been using the IsoTek Full System Enhancer & Rejuvenation Disc for AT LEAST one 65 minute cycle on each component EVERY DAY, and I am convinced I am hearing improvements much more rapidly than other who have posted similar reports.

oops, a client on the phone I forgot to call back . . . gotta go !!!

NJPOLKER

Congratulations on alot of excellent choices and work. I have SRSII's and SDA2a's both upgraded in similar ways so understand what your hearing.
Isn't the pride of accomplishment great?

inspiredsports

NJPOLKER wrote: »

Congratulations on alot of excellent choices and work. I have SRSII's and SDA2a's both upgraded in similar ways so understand what your hearing.
Isn't the pride of accomplishment great?

Thank you. Yes. The rush is amazing; it takes me back about 34 years to 18 :eek:! I haven't worked with my system for about 17 years and I had forgotten how much I enjoyed it. But I've gotta say, I believe the collective braintrust of this group has taken the level of Polk sound quality forward by a magnitude of 10 since SDA's were introduced.

But as almost all of you reading this post know, it's a slippery slope. I am tweaking everything I own now trying to squeeze more sound quality from it, and buying better new or used when I can't. I'm not sure I can control it. I guess the newness will wear off . . . . . eventually .

inspiredsports

On climbing mountains:

Sometime in 1921, Everest climber George Mallory is famously said to have replied to the question "why do you want to climb Mt. Everest?" with the retort: "because it is there"

Some summit, some die, some quit in between.

I've been asked for quite some time "Why do you keep trying to find a way to "TL" your SRS 2's?" Besides the obvious "because it is there", I've listened to the exquisite sound coming out of my "TL'd" SDA-2B's!

I think I'm close to the summit and will soon be the proud owner of the club's first 1986 SDA SRS 2 Blade/Blade "TL's" !!

http://www.polkaudio.com/forums/showthread.php?p=1012125

inspiredsports

Lasareath wrote: »

I have around 11 Extra 6509's, If you want 4 I'm sure we can work out something.

The only thing is that I bought a pair of SDA-1B's for $400 and had the seller ship me just the MW6509's, So those 8 cost me around $55 each!

Sal

Thanks Sal, I appreciate the offer!

I haven't updated this thread for a while, but in the same eBay buy where I got the SDA-1B crossovers (that are different from SDA SRS 2 crossovers by only 1 resistor), I picked up 2 SW120's passives and 4 MW6509's from the same seller.

He was in Ohio just 30 minutes away on the turnpike so I figured it was all a deal at his selling prices plus a couple of gallons of gas.

I'm going to replace the new 6509's I purchased from Polk in November with the vintage units from the eBay buy, give them a listen, and decide which ones to keep/sell.

I just got off of the phone with Sonic Craft and they are custom valuing my 5.8uf caps for my new SDA SRS 2 "TL" mod experiment as I write.

My Shotgun Cables and IC's arrive later today so I'm going to be in real good shape sound-wise very, very soon.

inspiredsports

Here are front and back views of just the high-pass circuit board of original SDA-1B/SDA SRS 2 (the only difference is where the "3.5" is typed in, this resistor is a 2.0 on the SDA1-B and a 3.5 ohm on the SDA SRS 2).

Can someone diagram where the 5.8 uf capacitor and 2.7 ohm resistor will best mate to this particular board for the "TL" mod?

I have a set already modded for RDO194-1's with Sonicaps and Mills resistors and know what that looks like, but am showing the unmodded photos as there is more room to see what's going on on the board.

(Where's Ben been lately? Chasing Chickens?)

heiney9

inspiredsports wrote: »

Can someone diagram where the 5.8 uf capacitor and 2.7 ohm resistor will best mate to this particular board for the "TL" mod?

(Where's Ben been lately? Chasing Chickens?)

That is the question of the day? Can you add those (2) components, somewhere in the circuit, to get the desired effect? That's really been the question all along once you get past the theory of modding for "TL". We all can see what the differences are in the various circuits/x-overs...........but it's the "re-engineering" of the early SRS2 x-over that's the real mustard on the hotdog.

I would hope by now Ben would have caught the chickens

inspiredsports

OK, but in post #26 at http://www.polkaudio.com/forums/showthread.php?p=1012031 we have Disc Jockey in a conference with Ken S. and Matt Polk saying it's "no problemo".

########## Matt Polk's words #######################################

"Yes, that modification should work. The 5.8 uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal and not the one that is in series with the small inductor.

The inductance of the tweeter voice-coil causes the impedance to rise at high frequencies contributing to a gentle roll-off. The by-pass cap modification allowed us to compensate for that roll-off without disturbing the carefully tuned relationship between the tweeter and the drivers in the crossover region."

Regards, Ken, Polk Audio

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

The SDA-2B and CRS+ schematics aren't that far off from the SDA-1B/SDA SRS 2 so it should just be a couple of jumpers or leads soldered in somewhat the same locations as in those circuits.

My top/left photo of my SDA-2B mod post in # 54 at http://www.polkaudio.com/forums/showthread.php?t=74945 shows the basic positioning of that particular circuit. Damn, I wish I'd have photographed the back side of that board, but I guess I can take it out easily enough.

So now it's just a matter of determining the 2 similar connection points on the SDA-1B/SRS 2 board.

inspiredsports

OK, so here's the "money part" . . .

Matt wrote, "The 5.8 uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal, and not the one that is in series with the small inductor."

In my image below, "RES 1, RES 2 and RES 3 are paired with the adjacent components IND 1, IND 2 and CAP 3. and ALL HAVE CONTINUITY WITH THE WHITE WIRE so I believe they are the ones where Matt warns "not the one that is in series with the small inductor."

The 3.5 ohm Resistor (would be 2.0 ohm in the SDA-1B crossover) is, as Matt put it, the "resistor that is in series with the input signal" (Black wire).

I'm pretty sure my diagram properly locates the 5.8 uf Cap parallel with that 3.5 (2.0 if 1B). What I'm up in the air about is, should I add the 5.8 cap . . .

A) --- PLUS the 2.7 ohm resistor leaving the 3.5 in place ??
--- REPLACING the 3.5 with the 2.7 ??
C) --- LEAVING the 3.5 in place and NOT USING A 2.7 ??

If I were a betting man I would choose "B)".

PLEASE HELP!

Systems

Which speaker is MP refering to when he is talking about the 5.8 uf cap?That schem already has the treble lift circuit but with a smaller 4.4uf .I doudt he means to add yet another cap parrallel to the 3.5 ohm to form yet another treble lift circuit.

ben62670

inspiredsports wrote: »

OK, so here's the "money part" . . .

Matt wrote, "The 5.8 uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal, and not the one that is in series with the small inductor."

In my image below, "RES 1, RES 2 and RES 3 are paired with the adjacent components IND 1, IND 2 and CAP 3. and ALL HAVE CONTINUITY WITH THE WHITE WIRE so I believe they are the ones where Matt warns "not the one that is in series with the small inductor."

The 3.5 ohm Resistor (would be 2.0 ohm in the SDA-1B crossover) is, as Matt put it, the "resistor that is in series with the input signal" (Black wire).

I'm pretty sure my diagram properly locates the 5.8 uf Cap parallel with that 3.5 (2.0 if 1B). What I'm up in the air about is, should I add the 5.8 cap . . .

A) --- PLUS the 2.7 ohm resistor leaving the 3.5 in place ??
--- REPLACING the 3.5 with the 2.7 ??
C) --- LEAVING the 3.5 in place and NOT USING A 2.7 ??

If I were a betting man I would choose "B)".

PLEASE HELP!

B. Pull the 3.5r resistor, and replace with a 2.7r resistor. Piggy back that resistor with the 5.8uf cap.

ben62670

Slight change of plans to get to the same place.
1) Pull the 3.5r, and the poly switch.
2) Insert 5.8uf cap in the holes marked yellow in the attached photo.
3) Piggy back the 5.8uf cap with the 2.7r resistor.

inspiredsports

Disc Jockey wrote: »

I can't help you with the resistor value question but if the crossover circuit is the same as the 1B, you should be able to do this simply. I looked in to the TL upgrade on a pair of 1Bs I ws going to buy, and this is the response I got from Ken (great CS as always):

Hello,
I forwarded your question to Matthew Polk:

"Yes, that modification should work. The 5uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal and not the one that is in series with the small inductor.

The inductance of the tweeter voice-coil causes the impedance to rise at high frequencies contributing to a gentle roll-off. The by-pass cap modification allowed us to compensate for that roll-off without disturbing the carefully tuned relationship between the tweeter and the drivers in the crossover region."

Regards, Ken, Polk Audio

The above is what Disc Jockey posted earlier in http://www.polkaudio.com/forums/showthread.php?t=78812 in post 26.

GV#27 wrote: »

The 1B already has a 4.4uf and 750pf paralleled with a 2.7ohm res.The 2B does not.

The only cap that is "in series with the input signal and not the one that is in series with the small inductor." is the one I've marked in my image and diagrams in post # 53 above

GV#27 wrote: »

Which speaker is MP refering to when he is talking about the 5.8 uf cap?That schem already has the treble lift circuit but with a smaller 4.4uf .I doudt he means to add yet another cap parrallel to the 3.5 ohm to form yet another treble lift circuit.

I'll defer to ben above and below.

inspiredsports

Ben, are you following that there is a question as to adding both the new 5.8 and leaving the existing 4.4 ?? I am so pumped to get this done I can TASTE IT! I sure hope this is the fix.

My Shotguns arrived at 6 PM and I got a chance to hook them up at 8. They are some F'in MOJO MAGIC WIRES, magic I tell you! right out of the box. If I can get these paired with 198's, I will be hallucinating every time I power up! And with no burn in. I can't imaging what will happen as they season a bit.

I have to check my actual modded board with the Sonicaps on it to make sure I have room, but I think I'm OK (I used photos of the original board as they have more room to see what's going on).

I think I can handle this one myself, but may pack up and ship to you when the new 5.8's and 2.7's that I ordered today arrive here in a few days if I get cold feet.


Edit: Yeah, there's going to be trouble. We used that spot already. I think I will be mailing to you.

ben62670

If that's the ones I modded just leave the resistor in place. I am sure I put it in the holes I marked. Piggy back that resistor with the 5.8uf cap, and yes leave the 4.4uf in place:) I am glad to see this Mod Polk approved.

inspiredsports

ben62670 wrote: »

If that's the ones I modded just leave the resistor in place. I am sure I put it in the holes I marked. Piggy back that resistor with the 5.8uf cap, and yes leave the 4.4uf in place:) I am glad to see this Mod Polk approved.

Yes, these are the ones you did for me in December.

OK, you mean piggyback the 3.5 ohm with the 5.8 uf? (and don't replace the 3.5 with the 2.7 ohm I have coming ??)

I think a 2.7 is supposed to be used based upon what Matt wrote to Disc Jockey as DJ relayed it to me in post # 28 at http://www.polkaudio.com/forums/showthread.php?t=78812

EDIT:

I can't tell for sure if Matt said 2.7, or if DJ just assumed because that is the value used in the SDA-2B and CRS+ mods. I guess I should get clarification because I don't want this to be wrong.

Matt wrote, "Yes, that modification should work. The 5uf cap, also known as a "By-pass cap", should only be added across the resistor that is in series with the input signal and not the one that is in series with the small inductor."

I guess if we take Matt literally, the 3.5 ohm is the "resistor that is in series with the input signal" and DJ made an assumption based upon the other TL mods.

Systems

inspiredsports wrote: »

The only cap that is "in series with the input signal and not the one that is in series with the small inductor." is the one I've marked in my image and diagrams in post # 53 above

As well as the cap you added,the 3.5R ,12uf ,2.7R and 4.4uf are inseries with the input signal.

ben62670

Sorry. I'm tired:( You do have to pull the 3.5 resistor. You should put the 5.8uf cap in the holes the resistor is in now. Then piggy back the cap with the 2.7r resistor.

Systems

ben62670 wrote: »

If that's the ones I modded just leave the resistor in place. I am sure I put it in the holes I marked. Piggy back that resistor with the 5.8uf cap, and yes leave the 4.4uf in place:) I am glad to see this Mod Polk approved.

Having 2 paralleled RC combos cascaded in series seems just a bit odd.Adjusting the values in the 4.4uf 2.7R combo would make a lot more sense.


Im still not clear what model MP was refering to,was it the 1B?

inspiredsports

ben62670 wrote: »

Sorry. I'm tired:( You do have to pull the 3.5 resistor. You should put the 5.8uf cap in the holes the resistor is in now. Then piggy back the cap with the 2.7r resistor.

That's what I thought.