SDA-1 tweeter? problem

vane

Hello,

I have an old pair of SDA-1 (S/N RSDA1 4545 and LSDA1 4533)
that I bought in 1986 in Jeddah / KSA. The sound became very
"muffled" and high on bass so I tought my amplifier died
and they just been standing in my living room.
I apologize for this ill-treatment.

I read in this forum discussions about capacitors failing? in the crossovers.

Could someone give some more advice, how could I check what is
wrong and from where I could buy parts. I live in Finland and Polk is
not very well known here.


TIA

Juha Vane
Finland

dorokusai

A crossover rarely goes bad, it is most likely another issue.

Can you add some more information as to the before, and after you noticed there was a problem?

The "muffled" effect could simply be the polyswitch or protection device. When you noticed, then turned down the volume for a minute....then resumed higher volume, did it sound normal?

F1nut

Juha, Welcome to the forum.

First, let's verify which speaker you have. There are 4 versions, the SDA 1, SDA 1A, SDA 1B and SDA 1C? If you remove one tweeter and one mid driver you will see numbers stamped on the backs, what are they?

vane

Apologize for describing the problem inaccurately.
I hate to admit, but it's a looooong time that I last
really used my stereao system. I just didn't seem
to have time. Well, now I've ben looking at these big
speakers and want to buy a new amplifier with a remote.

What I remember the sound was amazing in the past, I
remember that when people were wondering what the
heck are those, I played something classical, and there
was no more questions.

Now they sound really bad, the right speaker sound a
bit better, but the left one tweeters are dead. There
is no difference if I turn the volume down or off and
back on.

There is something wrong and I would like to have some
advice before I start to take them apart.

Brgds,

vane

Hey this is a very active forum.

I'll remove the elements and look what numbers I see.

There is no way of identifying these by the serial number?
Mine are RSDA1 4546 and LSDA1 4543. These numbers are
in the sticker back.

Brgds,

F1nut

I, we have no way of telling from the serial numbers. Only Polk might have that information and I wouldn't bet on that. However, the numbers on the backs of the tweeters and mid drivers will point us in the right direction.

vane

OK, I'm home and took out one tweeter and found what I
believe is a date Dec 02 1986 and a stamped text on top
of the sticker that say SDA-1.
The midrange say Nov 03 1986 and also say "engineered
to use in SDA-SRS2. The cable between speakers has two
flat pins and the cable terminals for input cable are screw type,
a pin with a hole and red / black nut to tight the cable.
Hopefully this help to identify the type?
I'll sen an other mail with a picture of the
midrange speaker as I seem able only to upload one picture?

Brgds,

vane

Here is a photo of the midrange unit.

Brgds,

vane

Here is a front photo of the tweeter.

Brgds,

PS. Sorry that I don't know how to post several small photos in one mail.

F1nut

Ok, we're getting there. They are either SDA 1A's or SDA 1B's. Look on the back of the mid driver for the MWxxxx number, what is it?

vane

The number is MW 6509, so these are then 1B's?
There was a post about what is the difference between
all these SDA-1's but it ended in the boxes?
What is the difference?
Wondering why all these different models was made?

I remember when I bought these in Jeddah, the sales guy
who obiously knew something about these, said that the
locals are only looking for the biggest possible speaker....

Brgds,

F1nut

Bingo! You have 1B's. The 1's used SL1000 tweeters and all the rest used SL2000's. They all used different mid drivers and crossovers, call it constant improvements.

Ok, now for your problem. As Doro pointed out you may have a bad polyswitch used for tweeter protection. First, try swapping the tweeters from the left cabinet to the right cabinet and vice versa. This should tell us if it's the tweeters or polyswitch.

vane

Thanks for helping me with this.

I'll do as suggested and also go thru all flat connections, there can be some bad ones.
My vife was not so enthusiastic about the speakers remaining in our livingroom,
she hoped that the space the speakers occupy would be free.

When I get them working again, I'll let you know and then I probably need some
help about choosing an amplifier.
My intention is to build a modest 2-channel system and also hook my TV / DVD
player into it.

vane

Checked the flat connectors and now it sound much better.
My amplifier is probably bad so I'm not 100% sure if the
speakers are OK.

Thank you all for helping me, now I have to find a suitable amplifier.

F1nut

Juha,

Are you saying that the tweeters are working now?

vane

Hi,

Yes, the tweeters are working now. I was a bit suprised about
the quality of the cable connectors. The flat male part is very thin
for the female connector in the cable. Probably a cost issue.

I couldn't identify anything that I could think to be a "polyswitch",
how does it look like? There was 2 separate round crossover boards,
one on top of the terminal box and the other on top of a big coil.

F1nut

It's kinda yellow colored and looks like a disc with two leads. If you do a search for "polyswitch" I think there is a picture in here somewhere. I'm too tired........going to bed.

vane

OK, I found a photo of it, it's a very small blue disk like thing,
like a capacitor.

Thanks,

Juha

F1nut

You know, I think some are blue and some are kinda mustard yellow. Either way, seems like you've found it. If you need to order some contact Polk's customer service.