POLK SDA-1B REBUILD

jdesalvo2

CAN ANY ONE TELL ME SHOULD I REPLACE ALL DRIVERS AND TWEETERS VS JUST CAPS, RESISTERS AND OMIT POLY SWITCH. SPEAKER ARE WORKING ,BUT OLD?

Nightfall

If the midwoofers are working, don't replace them.

Everything else is game.

jdesalvo2

SO TWEETER YES MID NO.

jdesalvo2

THANKS NIGHTFALL

Faustin

What tweeters do the speakers currently have? If they are sl2000 , sl2500, there are newer more desireable replacements that can be purchased from Polk, such as the RDO 194 and RDO 198. And as Nightfall said, as long as the 6.5's are working and not making a "rubbing sound" they are fine. The older 6.5's are prone to magnet shift if they are bumped too hard or dropped due to the glue drying out. Then they will freeze up or have a scraping sound. They magnets should be glued with Locktite Power Grab. There are many posts available in regards to this subject if you do a search.

ken brydson

Why are you SHOUTING??

jdesalvo2

Sorry, I'm new here.
Yes , I have the SL 2000, The mids are mw 6509 no rubbing sound.
How can I check tweeters?

Nightfall

Put your ear up to them?

It is beneficial to upgrade your tweeters to the RDO-194's even if they're fine.

Epoxy the magnets on your midwoofers to ensure the magnets don't shift.
Mass load the midwoofer baskets with dynamat or a similar product. (There are many)
Upgrade the caps on the crossovers to Sonicap or Claritycaps.
Upgrade the resistors on the crossovers to Mills.
Put a strip of BH5 behind the midwoofers to prevent sound bouncing directly back at the cones.

jdesalvo2

How/where do you install dynamat,BH5 and what is BH5?
Are you leaving original fiber insulation in there to?

Nightfall

Dynamat: Here's the where. How I think is self explanatory.
http://forum.polkaudio.com/discussion/comment/637226

BH5: Blackhole 5.
http://forum.polkaudio.com/discussion/148198/blackhole-5-damping-material-in-the-sda-srs-1-2tl

Keep the original polyfill, just make sure it's all above the passive radiator. Staple it if you have to.

Do some searching. Upgrade threads are all over the place, including where to epoxy the magnets and crossover upgrades.

Schurkey

The 1Bs are SUPERB speakers once the typical weak-spots are addressed. The only real deficiency is that the 1B MUST have a common-ground amplifier. It cannot be made compatible with the isolation transformer like the two newer-generation SDA speakers. Well, yes, it can be made compatible, but the sound quality suffers so it's not worth the modification.

Don't forget the spikes on the base of the cabinet if the speakers are parked on carpet.

Test for cabinet air leaks with the "push test"; push in and hold the passive radiator--the mid-woofers will push out, then slowly return to the mid-position. When you release the passive radiator, the mid-woofers will pull inward, and slowly return to the mid-position. The question is how long it takes the mid-woofers to return to that mid-position. 3--5 seconds is typical. Less than that indicates a cabinet air leak that will hurt bass.

I think the 1Bs are lacking in treble; removing the polyswitch and the 2-ohm resistor in the high-frequency crossover in favor of a 1.5- or 1.75-ohm resistor will increase the treble output in relation to the midrange/bass.

The huge SDA air-core inductor can be replaced with a 10uH magnetic core inductor from ERSE, if the inductor is unwound a few turns to get to 9.6uH. Makes for better bass, but will lower the speaker impedance. You'll need a decent amplifier to keep up.

There's more, but you've already been given enough to get started.

jdesalvo2

Schurkey I called Rogue Audio and yes my Pharaoh is common ground amp..Spike's yes, poly switch remove add 1.75 or 1.5 resister,I'll relay info to my electronic repair guy./ Vince at Gallaxie Electronic,s Pittsburgh,
PA/GREAT!!!
I'll take care of spikes,bolting speaker in,mortite seal,
and just ordered new tweeters RDO194,s.Please keep in mind I only want to rebuild to original condition at this time.The high's and mids sound great,now that I have enough power the bass very nice. 28 years later I,m really enjoying my SDA,s 350 wpc @ 4ohm now, compared to my old Carver 160 wpc @4 ohm. Replaced old duel tt with Rega RP8/ apheta cart.Out with old Carver cd player 1982,in with Sony 5000ES Simm 110 dac.
I like the new audio components, but I was running out of cash so this rebuild will save me for buying a new set of speakers @ 5 to 12 thousand or more.
So this rebuild will be great. Dropping off cross overs tomorrow,Polk said 1 week delivery ,so by next weekend I should have every ready to reassemble and start enjoying again.
Have pair of rta 12c,s ordered tweets for those also.
Then I can get them rebuild as well.
Thanks for all your input.

Schurkey

jdesalvo2 wrote: »

Schurkey I called Rogue Audio and yes my Pharaoh is common ground amp..Spike's yes, poly switch remove add 1.75 or 1.5 resister,I'll relay info to my electronic repair guy...
...So this rebuild will be great. Dropping off cross overs tomorrow,Polk said 1 week delivery ,so by next weekend I should have every ready to reassemble and start enjoying again.

Let's be clear: You are not replacing the polyswitch with a resistor. Remove polyswitch, remove 2 ohm resistor from each high-frequency crossover. Replace 2-ohm resistor with 1.5--1.75 resistor, replace the polyswitch with a jumper wire--or twist the polyswitch leads together and solder them so as to bypass the polyswitch. The purpose of this is to eliminate the degrading effect of the polyswitch, AND to increase the level of the treble in relation to the mid/woofers.

If you don't agree that the treble volume is too low compared to the mid/woofers, you wouldn't change the resistor value; and you might even add a quarter- or half-ohm as compensation for the resistance of the polyswitch you're removing. Depending on your assessment of the treble volume, you'd use a 1.5-to-2.5-ohm resistor in place of the stock 2-ohm.

For me, the treble of the 1B was weak from Day One; in three different rooms over the course of almost thirty years. I recommend reducing the value of that main resistor!

There are three other resistors in the treble crossover, each a 2.7-ohm unit. Those get replaced with Mills 2.7-ohm resistors. Don't change the value of those guys.

The electrolytic capacitors are well beyond their expected service life, so you'll be replacing them, too. The consensus is to use film caps rather than fresh electrolytics as the specs on the film caps are so much better than what can be had as an electro; and the film caps don't have the service-life problems of the electros, either.

Mortite (a brand name for "rope caulk") is a mistake. Yes, it works great--until you have to remove a driver at which point it becomes an INCREDIBLE hassle. Stock-type gaskets in good condition will seal the driver to the baffle. If the fastener holes in the particle-board have deteriorated, use Hurricane Nuts and machine screws instead of the stock wood screws.

jdesalvo2

Schurkey thanks again for your info I'll forward this tread to Gaxlexie Electronic's.

jdesalvo2

The SDA 2B cross over work was complete a week ago.Every part on cross overs has been replaced.
Speakers back together with all new tweeters,but no new seals or screw to bolt replacement yet. No black hole no.5 has been purchased yet also.
Breaking speakers in for now,enjoying the vibes.

Can I purchase new seals for all speakers?

How much black hole no.5 do I need and where to place them at what specific size pieces?

What size nut / bolt, length diameter?

jdesalvo2

Its been a while I found my black hole no.5 info above,apologies.

machone

You can make your own gaskets using armacell. It comes 2" wide x 1/8" thick x 30 ft and has an adhesive back. You can buy it at Home Depot. Just tighten the screws a little at a time to allow the gasket to compress.

F1nut

If the stock gaskets are not damaged, there is no reason to replace them.

Hurricane nut thread should be 8-32, same for the screws, of course. One inch long will do the trick.

drumminman

1 sheet of Black Hole 5 will be plenty, with a little left over. Remember that you use 4" wide strips from the bottom of the MW's to the top of the cabinet, on the back wall facing the magnet of the MW's.