SDA SRS purchase?

gildonsda

Hi all,

First wanted to introduce myself. I started my Polk journey with a pair of Monitor 11s about 20 years ago, and have gradually added a few more pairs over the years (Monitor 5 Jr., RTA-11T, SDA 1C).

I ran across a set of the original SDA SRS (blade/blade) in my area. They are in great cosmetic shape, with all original drivers and crossovers.

When I went to check them out last week I noticed that some of the MW6503 drivers had small cracks/splits in the rubber surrounds (4 drivers in one column on one speaker, 1 driver on the other speaker). The 15" PR and all other surrounds looked great.

The speakers have been stored in a garage in FL for the past 7 years or so, covered with plastic. There is no rust or water damage visible.

A few questions for you experts:

1 - Any idea what would cause the surrounds to crack like that? Heat? Improper usage?

2 - Assuming everything else tested out fine, what would these speakers be worth considering the good cosmetic condition and need to replace 5+ drivers?

3 - I understand Polk carries a replacement driver (RD6503-2). Could I simply replace the 5 damaged drivers, or do I need to replace 8 to maintain symmetry? I'm not sure if the new drivers are an exact sonic match.

Thanks for any insight you all can provide!

gildonsda

Polkie2009

Welcome to the site Gildon, hopefully some of the folks here who are experienced in reconditioning and upgrading their SDA's will chime in with the answers you need.

Moose68Bash

It's not difficult to replace the foam surrounds on the drivers. I've done it, and I'm not a terribly accomplished speaker repair guy.

If I chose to replace the drivers, rather than repair them, I would replace them all with the same drivers.

However, if I were going to go that far, I'd replace them with the drivers for the SDA SRS 1.2TLs and replace the tweeters with RD0-198-1s, have Vr3 Mods upgrade the crossovers, internal wiring, SDA interconnect and inductors, and provide custom binding post plates with Neutrik connectors so that the interconnect would be compatible with the TL'd crossovers, etc.

While I was waiting for Trey's components, I'd apply BlackHole 5 to the insides of the cabinets and Dynamat Xtreme to the "baskets" of the drivers and PRs. I'd also install a good set of spikes.

That's a pretty deep dive down the rabbit hole, but you'll find lot of the members of Club Polk down there with you.

And, more important, those speakers will bring a big grin to your face every time you give them a listen -- with other good components!

Others will have more informed opinions than I, but I think a good price for them would be $1,000 or less in their present condition.

leftwinger57

Not an expert either here but butyl rubber surrounds should not rot or crack especially in a humid and kinda wet climate like Florida unless they got all day sun on them for many many years. Polk still sells 6503 mids so I would go that route and not have them refoamed or surrounds. Yes the mods are way better than the stock version and it's not all that hard if you have some cash and a little sweat equity. I took my '87 2Bs from bone stock to the next level and it was night and day difference. Oh one other thing I did blow one 6503 and I got mine on E-Bay for $19 and it's a year newer and sonically the same.

westmassguy

You cannot replace the butyl rubber surrounds with foam, and current replacement rubber surrounds are too thick. Both will change the T/S parameters of the woofers.
Best to keep an eye on eBay, or spring for new replacements from Polk.

leftwinger57 wrote: »

Not an expert either here but butyl rubber surrounds should not rot or crack especially in a humid and kinda wet climate like Florida unless they got all day sun on them for many many years.

Lew, I've seen some cracking on older Monitor 10s and SDAs. Many things can accelerate aging, Heat, UV Rays, and Pollutants in the air to name a few.

gildonsda

Thanks for the feedback! Unfortunately a complete rebuild is not an option right now. Just would want to get them in good working order.

The surrounds are soft and pliable, not brittle. I guess they have small slits or V-shaped tears and not cracks (poor word choice on my part).

Could this be hiding a more serious problem? Amplifier overdriving, etc?

westmassguy

Sounds like deliberate physical abuse be someone.
http://forum.polkaudio.com/discussion/163519/found-product-for-butyl-rubber-surround-repair#latest
I would attempt the repair from the back side first, so it doesn't show.

gildonsda

Thanks westmassguy. The pic from stogieguy in that thread is exactly the type of issue I was trying to describe on these surrounds. I'll check out the recommendations that were mentioned there.

gildonsda

Picked them up today. Need to replace a tweeter as well but overall they are in great condition. Oh, and these things are BIG! ;-)

Thanks again for the advice. Looking forward to getting these babies tuned up.

F1nut

I guess they have small slits or V-shaped tears and not cracks

Cat claws.