SDA wiring checkpoints

jimbo1421

Hello,

In other threads I described a problem with my SDA-1Bs where the phantom center is much reduced; center vocals sound as if they come from a long way away. See: http://www.polkaudio.com/forums/showthread.php?t=85190 and http://www.polkaudio.com/forums/showthread.php?t=85454

Polk CS sent me a document entitled "Quick Tests To Determine Proper Functioning of SDA Loudspeakers", which describes both white noise listening tests and resistance tests between various connection points. I have done both.

I used a white noise generator from my laptop for the listening tests. My SDA-1Bs passed these tests except in one particular: The "Quick Test" file described an "odd, spacey quality" when listening to the pairs of dimensional speakers by themselves, with the balance all the way to the right or left; I didn't hear that quality; the white noise seemed to come from far left to near left, center, and near right to far right.

The results of the resistance tests are in the attachment. Notice that some of the measured values are as much as minus 21% of the reference values that I got from the "Quick Test" document, whereas +/- 10% is considered normal.

So what does this all mean? I know little about electronics; I am just following directions. Do the results of my tests account for the missing center image? Whether they do or not, what is my next step?

Regards,
Jim

PS: I would like to post the "Quick Test" file here, but it came in an email prohibiting unauthorized distribution. I have asked for permission, but have not heard back.

PPS: Unplugging the interconnect cable causes the center image to sound as expected.

jimbo1421

bump…

Can anyone interpret the results of these tests?

Jim

F1nut

Looking at your test results, you have problems. I'd say either some of your wiring is wrong and/or something is wrong with your crossover(s).

Also, I noted in another post that you said the drivers are MW 309's. They should be MW6509's.

Can you post detailed pics of both crossovers with the wiring connected?

jimbo1421

F1nut wrote: »

Looking at your test results, you have problems. I'd say either some of your wiring is wrong and/or something is wrong with your crossover(s).

Also, I noted in another post that you said the drivers are MW 309's. They should be MW6509's.

Can you post detailed pics of both crossovers with the wiring connected?

Thanks for your interest, F1. All the midwoofers are MW 6509s. Not sure where that 309 number came from-typo?

It will take a few days to get pictures developed. I am still in the 35mm film age.

Regards,
Jim

F1nut

No problem, I'll be here. 35mm still takes the best pictures.

F1nut

Hey, just a quick question. Do you have the right speaker on the right side, left on the left as you look at the speakers?

Also check that you have the speaker wires connected properly, positive to red, negative to black. If they are correct, swap them. Postive to black, negative to red at low volume and see what happens.

jimbo1421

F1nut wrote: »

Hey, just a quick question. Do you have the right speaker on the right side, left on the left as you look at the speakers?

Also check that you have the speaker wires connected properly, positive to red, negative to black. If they are correct, swap them. Postive to black, negative to red at low volume and see what happens.

Yup and Yup. I will try the swap.

Side issue: I just pulled the bass radiators to take pictures and noticed that the styrofoam cones are mounted about 1/8" off center when viewed from the inside face through the hole in the basket. From the outside face the black circular thing is also off center with respect to the rubber surrounds. I see no signs that any of the parts have detached from each other. Is this a problem?

Thanks again for your interest,

Jim

jimbo1421

F1nut wrote: »

Also check that you have the speaker wires connected properly, positive to red, negative to black. If they are correct, swap them. Postive to black, negative to red at low volume and see what happens.

I just tried this. It has the same effect as unplugging the interconnect cable: the dimensional speakers go silent.

Regards,
Jim

F1nut

Ok, it would seem that the phase is correct.

jimbo1421

That's good. I should have pictures of the crossovers Thursday night.

Thanks,
Jim

jimbo1421

F1nut wrote: »

I thought we covered this already. You've got a problem and you're going to have to do some testing of cap/resistor and possibly inductor values or you could simply upgrade the caps and resistors as they are old/inferior anyway.

Where's those pictures you took?

I will be getting them back today; I had to work late the last few days.

Jim

jimbo1421

F1nut wrote: »

Can you post detailed pics of both crossovers with the wiring connected?

Hi, F1nut. Here are the left channel crossover pics. Right channel to follow.

Jim

jimbo1421

F1nut wrote: »

Can you post detailed pics of both crossovers with the wiring connected?

Hi again, F1nut. Here are the right channel crossovers pics. What do you think of them?

It has been four days since I started this thread and in that time my SDA-1Bs have improved remarkably. The center image has emerged to equal the center when the interconnect is unplugged. It's as if the cones had been hibernating and needed to be played in order to loosen up. In fact, they were stored for an unknown number of years here in a dry desert climate. The rest of the imaging is also greatly improved.

I redid the DC resistance tests to see if, magically, they had also corrected themselves; nope, same values I reported above.

I am happy with them now; before, they were very confused sounding and nearly unlistenable for some music. They are good enough that I can now work on room placement issues; sometimes the left and right still seem excessive compared to the center.

What do you think the next refurbishing step should be? In no particular order, I want to upgrade the SL2000s to RDO-194s, Moretite and Dynamat the drivers, and refurbish or upgrade the crossovers.

I sure do appreciate your input on these problems.

Regards,

Jim

F1nut

Ok Jim, I will study the pics later, no time right now.

jimbo1421

OK good. Enjoy your weekend.

Jim

F1nut

Nice, clear shots.

The only possible issue that I can see is in the pic of the right top. The blue wire at the bottom appears to have a bad kink in it. You should check that the wire isn't broken.

I see that this might all be mute as you state the sound has improved.

Enjoy!

jimbo1421

F1nut wrote: »

Nice, clear shots.

The only possible issue that I can see is in the pic of the right top. The blue wire at the bottom appears to have a bad kink in it. You should check that the wire isn't broken.

I see that this might all be mute as you state the sound has improved.

Enjoy!

Thanks for looking at this, F1nut. The "bad kink" in the blue wire is due to the camera angle and is actually a gentle bend looked at endwise. I also checked the continuity while wiggling the wire as well; it's good.

I think I will continue to give them as much playing time as I can in the next week or so, and play with room arrangements. Then reevaluate their sound and decide what is next.

Thanks again for your time.

Jim

F1nut

I would still suggest that you change the caps (resistors too) as they have reached the end of their useful life by now and that may account for the readings you're getting.

george daniel

F1nut wrote: »

Nice, clear shots.

The only possible issue that I can see is in the pic of the right top. The blue wire at the bottom appears to have a bad kink in it. You should check that the wire isn't broken.

I see that this might all be mute as you state the sound has improved.

Enjoy!

Eh,, the President has just issued a statement,, please use the word moot, instead of mute,for this application only. As always,, thanks in advance for your compliance with this request.Mr. President finds that it is better to be pro-active in this media release. Thank you,, BTW that looks like it would be a fun project(cap & resistor) replacement. Good lucl.