SDA2B not working correctly, where to start?

brekekex

New to forum, equally new to SDA.

Today I purchased a pair of SDA2Bs, black, pin/blade (home-made interconnect cable), 6503 and 6511 drivers,
haven't pulled the tweeters out, so unsure what model they are. All 4 drivers dated April 1990.
Safe to say they are 2Bs?

Powered by a Rotel RB-960BX.

So, set them up as per manual, tape measure and all.
Listened to them without the interconnect cable: impressed. I am fairly new to home audio, but they sound pleasant.

Listened to a few tracks that I am very familiar with (electronica and the like), then listened to the same music with
interconnect cable in place, and the soundstage became much, MUCH narrower... Just does not sound right.

Confirmed that speakers are connected correctly.

So, I played with the L-R balance:
when selecting L speaker only, the R outer driver still emits sound, I assume this is correct,
but
when selecting R speaker only, the L is totally silent.

Anyone have any suggestions where to start?

Thank you, SDA gurus and veterans.

-Thomas

F1nut

First, make sure your amp is common ground. If it is, then take the outer driver from the left speaker, swap it with the outer driver from the right speaker. Does the problem follow?

inspiredsports

RussMan had one. Does this help? http://www.polkaudio.com/forums/showthread.php?44428-FS-Rotel-Channel-Islands&

chandler9a

I have a similar problem with some sda 2.3's, currently in storage. F1 had a good suggestion to try. If thats not it, check your IC and make sure its secure on both ends.

I think my problem is at the xover but hopefully yours is a little easier.

Welcome to the Club

brekekex

Thanks all for prompt replies. I only now had a chance to bring my DMM home and with little time, I chose to check the supplied
(home-made) interconnect cable resistance and noticed it may not be correctly made.
Is the ic cable supposed to be wired pin-pin and blade-blade? Mine were reversed: pin-blade.

Thanks again.

-Thomas

F1nut

Pin to pin is correct. The blade to blade is not used on pin/blade models unless it's the AI-1.

brekekex

Gotcha... so, I rewired the IC cable, pin-pin and had a listen. Still uncertain of results.
What I did notice, and this is unnerving, is that the left side of the Rotel amp was significantly hotter than the right, this is after
about 20-30 minutes of moderate listening.I shut it down to cool off.

I measured the speakers resistance: both read 3.8ohm with IC not connected,
with the IC connected, each speakers resistance drops to 3.2ohm.
Strange part is, that the resistance changes only when both, the pin and blade wires of the IC are connected.
With only one or the other connected, the resistance of the speakers remains 3.8ohm.

Should I be leaving the blade-blade wire disconnected, and only use the pin-pin portion?

This is rather intriguing. =-)

Thanks again.

brekekex

And, just to be sure, I measured resistance between the negative speaker terminals on the amplifier: 0.2 ohms.
The leads contribute 0.2 ohms to that reading.

inspiredsports

Continuity between right and left channel grounds should be a 100%, a dead short, on a common ground amp unless there were resistors added to the ground circuit by the manufacturer. .2 ohms sounds OK if you are sure the leads are responsible.

F1nut

Should I be leaving the blade-blade wire disconnected, and only use the pin-pin portion?

Yes!!!

What I did notice, and this is unnerving, is that the left side of the Rotel amp was significantly hotter than the right, this is after about 20-30 minutes of moderate listening.

That issue should go away after you disconnect the blade/blade wire. If it remains, you have damaged the amp and it will need service.

brekekex

Excellent, thanks for the advice!
Think my amp got away unscathed.

SDA is definitely working, it is a bit one-sided however. So I played around with the balance, playing one speaker at a time and
found that when

selecting R channel only, the left outer effect speaker emits a range of frequencies, mid-bass to mid-range
whereas when
selecting L channel only, the right outer effect speaker emits only very low frequencies.

Crossover issues, I presume?

-Thomas

Gavin.Wright

Check out this link - scroll to the very last post and download the "sda quick troubleshooting guide"

http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array(SDA)


This goes through some specifics on troubleshooting the "dimensional" portion of your SDA speakers...

It helped me figure out that I had one driver out of phase. Good luck.

Tony M

I just had a lopsided experience with my Hartleys. I had put the Pos. on the Neg. on one speaker.

Also, my old SDA CRS's had that prob. too. It was because the RED speaker nut was reversed with the black by some idiot.

Check your polarity items.

brekekex

tony millard wrote: »

It was because the RED speaker nut was reversed with the black by some idiot.

Looks like the same idiot must have owned my speakers, as well.
I cannot thank you enough for mentioning the possibility of such shenanigans.... the left speaker speaker wire nuts were reversed.
They (my new-to-me SDA2Bs) are perfect. PERFECT!!

Thank you all for your input: I learned a lot from it, and the subsequent searching I have been doing since I purchased these
speakers. I questioned said purchase a few times since then... singing a different tune now.

-Thomas