SDA SRS 2 Upgrade

[SCompRacer]

First off I’d like to say thanks to all those who have posted threads here at Club Polk documenting their SDA upgrades. Names like DarqueKnight, BlueMDPicker and ardvark1 are some I recall reading though there are more. A special thanks to DarqueKnight who cleared up some questions I had regarding components before I started.

There are no SRS 2 upgrade threads that I could find so I figured I would start one. While the circuit boards appear to be the same for some of the SDA’s, the number of components on them varies due to number of drivers/tweeters. Perhaps this thread will help someone attempting to upgrade their SRS 2’s in the future.

In regards to the parts, I decided to use Solen PB Series 400 volt caps based on DarqueKnight’s and others comments about them. I elected to use 12 watt instead of 5 watt resistors. I agree with DarqueKnight in that they are “More robust and durable.”

After receiving a copy of the 8.5” x 11” schematic from Ken at Polk, I magnified it to 11” x 17” making it easier to read. I compiled a list of components and ordered most of the them from Parts Connexion. Solen does not list a 40uf and 4.4uf cap so I ordered 39uf and 4.3uf caps. I don’t think that difference is a big deal using 5% tolerance parts, but those who feel differently should order a 1.0uf and .1 uf cap and piggy back them on the 39uf and 4.3uf caps to get the exact values.

SRS 2 Component List (Partial, more below):

(2) Solen-51560 PB Series 39uf Cap
(2) Solen-51558 PB Series 20uf Cap
(2) Solen-51556 PB Series 12uf Cap
(2) Solen-62366 PB Series 4.3uf Cap
(2) Mills-62746 MRA-12 2.7 Ohm Resistor
(4) Mills-62754 MRA-12 7.5 Ohm Resistor
Materials:
(100g) Cardas-62034 Solder. ($11.00)

Cost of these items is $82.70 at time of this posting.

If you wanted to use 5 watt resistors, order these part numbers and deduct $8.10 from the above amount.

(2) Mills-64619 MRA-5 2.7 Ohm
(4) Mills-64402 MRA-5 7.5 Ohm

You’ll also need two 750uf Silver Mica caps. Parts Connexion listed a 300 volt Silver Mica in 5% tolerance, but I went with 500 volt 1% tolerance parts from Handmade Electronics. A local place had told me they had some, but they turned out to be 10% tolerance parts.

(2) 4-10482 Silver Mica 750uf

Cost was $1.60 for these parts. (There is a handling charge of $2 added to shipping charges for orders under $20).

I upgraded the stock binding posts with Cardas HCBP-S Short Economy Binding Post’s from
DIY Cable. This thread by F1nut details how to go about it. The only thing I did differently to save some time was retain the Cardas mounting block for the low frequency posts instead of filing flats for the shoulder on the new posts. The center to center was the same in the binding post plate, so after enlarging the holes it was a drop in swap. I left the nuts on the binding posts loose and the posts hanging out as far as they could when I soldered the wires on them to avoid the possibility of melting the plastic.

The cost was $61.60 for four pairs of these, but you can halve that if you didn’t want to retain the bi-wire option.

I installed the 12 watt resistors standing, and found if you lean them slightly you will have just enough lead protruding through to bend over on the circuit board. The resistor closest to the tweeter output connector would have been a problem as the holes for the resistor leads are very close together. Fortunately for me, Polk had provided another hole further away in that same circuit trace that was clean and just needed to be tinned with solder.

If you shift the 12uf cap towards the tweeter/driver connectors and butt it against the coils, the leads from the 20uf cap will be long enough to make it through the board. I left the leads on the 750uf cap longer (C4 on the board) and mounted it towards the coils to allow ample clearance for the 12uf cap and lead. I stood the 39uf on end so I only had to use one lead extension. I used a high quality hook up wire to extend it. Hot glue was used to secure the components.

The total cost of the parts for my upgrade was $145.90. Due to my odd work hours, I got them installed early this morning but couldn’t play them very loud cause folks were still sleeping. At low volume, I could hear more detail and had a wider and deeper soundstage. Hopefully I’ll have time this weekend to experience the improvements I have heard others speak of.

EDIT: 11/19/05 Added .1uf and 1.0uf to make exact OEM values (4.4uf and 40uf). One speaker done to find if it makes a difference. I'll eventually report findings.

The results:
McLoki met Normanality at my place to pick up Norm's LSi15's in December '05. I asked them to pick the best sounding SRS 2 without telling them which one had the exact value caps. I used the Rive's Audio test CD2, tracks 63, 69 & 70. Track 63 is the original recording of D'Angelo Trio/La Pardida. Track 69 and 70 are left and right channel only. Both of them picked the right speaker, which had the exact value caps, so there ya go. I added exact values to the left speaker so they match.

[F1nut]

Looking great! Remember they will need a bit of burn in time before they sound the best.

One note about the resisitors, the 5 watt is all that is needed and in fact, has a lower inductance than the 12 watt.

[Mike Reeter]

Very nice work,I also have a pair of SRS 2's that I'm planning on upgrading soon...I think my first tweek will be replacing the tweeters...But,I'm no good with a soldering gun,would you be interested in performing these crossover upgrades if I shipped them to you? I would of course pay you for your time/trouble.

Thanks,Mike

[SCompRacer]

Thanks guys. And thanks for the vote of confidence Mike.

Swapping out the tweeters is a good move, I just did mine last week. I picked the SRS 2's up in late June and after hearing the replacements, I regret not getting them sooner.

Mike, I'd be happy to help you out but I do have a project I need to get past before doing them. I'll PM you with the details.

[ND13]

Looking good Rich.

[BobMcG]

It looks good, and was actually a lot fun wasn't it?

[schwarcw]

Great job Rich!

I'm going to order the parts for my SDA-2s soon. Did you ask Ken if Polk can email you a pdf of the crossover schematic? The one I got in the mail was like yours, small print.

Carl

[SCompRacer]

Thanks for the kind words....

It looks good, and was actually a lot fun wasn't it?

Yes, it was actually a fun type of work.

Did you ask Ken if Polk can email you a pdf of the crossover schematic?

I will have to request it. I didn't know it was available in pdf. Thanks.

[F1nut]

Polk will not email any schematic. What you got is the best you're going to get and yes, some of them are a little hard to read. At least you got one, eh?

[SCompRacer]

Actually, I have three. One 8.5 x 11 original, one 11 x 17 working copy and one 11 x 17 for the archives. I'm out of 11 x 17 laminate though so it was stressfull having a cup of coffee nearby.