View Full Version : A little problem with SDA-SRS 2.3's
02-05-2005, 07:42 PM
I've got a pair of 2.3's I bought new in 1990. They were store demos. I've never thought they had much bass and they went in storage at the end of that year. I hooked them up again about a month ago (it's a looong story!) and had weak sound from the left side, so I pulled all the drivers and checked them one by one. All ok, so I put them back in and voila, balanced sound. Must have been corroded terminals. I then bi-wired them for the first time and it sounds better, but still about as much bass as a good 4" HT tower. I pulled the x over cable and have continuity on the pin to pin, but nothing on the blade. All looks like brand new. I was driving them with an Adcom GFA 555. So then I hooked up a real cheap Pioneer HT unit and when I boost the bass 8 db at 50 hz (the only setting available) it starts to sound full range , although not very good with that component driving them. The SRS effect is strong with staging 3 feet outside each speaker. So what is wrong here? Is the cable supposed to have feed blade to blade and pin to pin? Have my capacitors died? I've got huge coffins that sound about as full range as a Bose cube. Any ideas?
02-05-2005, 09:05 PM
Your SDA cable seems ok as you should have continuity pin/pin but not blade/blade. I would think the Adcom-555 should do a decent job. My brother uses a pair of them running in mono on his 2.3TLs with excellent results but it seems one could do the job too. I haven't heard them pushed by only one so I can't say for sure. My 2.3s are driven by two Hafler 9505s running in mono and has prodigious bass. I have run them using only one of the Haflers in stereo and the sound was great and not bass weak at all. I have also powered them (years ago) with a Yamaha M-85 amp with satisfying results. No lack of bass there either. Room accustics I suppose could be a factor but how much? Hummmmm, not getting good bass with 2.3s and a 555??? Maybe you do have a deeper seated problem inside your cabinets. I'm sure others will answer who have experience with the Adcom amp.
02-05-2005, 09:40 PM
I forgot to mention I played a test disc with tones to check response. Now for some reason it jumps from 40 hz to 50hz and then to 70 hz, from then on in 10 hz increments. I set the level to 80 db at 70 and went up and down the scale. It was fairly linear to 4000hz or so, so that was good. But at 50hz it dropped to ambient in the room. audible, but not really measuring. At 40 hz I could not hear it at all, so I cranked the volume up to halfway and it was still silent. This waould be consistent with what I think I hear. It's just as though there is a huge filter in the system. I tried the amp on my neighbors speakers (paradigm) and the amp isn't the issue. Like I said, 8 db boost at 50 hz brings it back in line. Help!!!!
02-05-2005, 10:03 PM
I would start by checking for air leaks in the cabinet(s), damage to the rubber surrounds, a separated passive radiator or two and recheck that all the mid drivers are actually working. It seems from what you're saying about nothing below 50 Hz that the PR's are not getting fed.
What are you using for a pre amp and source?
FWIW, My 2.3TL's produce vast amounts of solid bass.
02-05-2005, 10:13 PM
One very quick and simple test to see if all your drivers are capable of proper movent and to see if your cabinet is tight or not is to push in the PR and hold it. Watch the reaction of your mid-drivers. They should move outwards and then slowly retract. If you pump the PR they should flex in and out. There shoud be silence when performing this test. Any scratching like noises will is an indication of a driver(s) bring missaligned. If a driver doesn't move, the suround may be shot. If none move, the cabinet is not tight.
02-05-2005, 11:31 PM
Tried all that. The speakers are in like new condition, maybe have 50 hours playing time on them. When I had the drivers all out as I mentioned earlier, I tested them each in an enclosed box fed power from one channel of the amp. With the SPL at three feet the volume at three frequencies was within 1 db on all of them, except for the SRS drivers. The left drivers were matched with each other, but 12db louder than the right side, which matched each other. So, I just crossed one of each to the other side. Not a perfect fix, but cheap. Since everything else tests and looks allright, can I have a problem in the crossovers? Both equally? The highs and mids are crystal clear, as always. I se movement in the surrounds, but not much. It doesn't look like a subwoofer extension. This is very strange.
02-06-2005, 08:33 AM
That certainly doesn't sound right. (I'm sure you meant betwwen the SDA drivers.) You shouldn't be seeing all that much movement in the mid-drivers when they're operating so that's normal. Maybe a call to Ken Swauger at Polk wouldn't hurt. Or a post to him in the "Troubleshooting " forum.
02-06-2005, 02:35 PM
Would involve too much coincidence to be cross-over or binding post related (if either speaker was good, drop off should only be 3 dB or so)...
My first thought was room interraction, i.e., cancelation, but should not be true throughout the room.
Then I thought phasing, but if all is good from 70 Hz on up...
Still might be worth repeating your LF test measuring SPL at 1 meter directly in front of each PR...
Agree with Bob about contacting Ken... I'd call him Monday, and while you are talking request he send you a copy of the SDA troubleshooting guide. It's a nice, step by step series of simple VOM checks. Has sections for each SDA series...
Edit: Just reread your opening post...
so I put them back in and voila, balanced sound. Must have been corroded terminals I'd go back in, this time with the intent of cleaning all the connections (x-over plugs, clips, etc.) and inspecting all the soldered connections (binding posts, etc.)
Please keep us posted... Enquiring minds want to know...
02-07-2005, 11:53 AM
A good test is to touch the power input jack on the speaker (amp disconnected) to a 9 volt battery. You should see the 4 inside speakers pop out and the 4 sda speakers be pulled slightly inward due to vacuum.
02-07-2005, 02:55 PM
... and the SDA MW's in the opposite speaker should suck in as well with the SDA IC in place...
Was just thinking the same thing Max... phasing of the MW's in a given cabinet...
If it's phasing, doesn't seem that application of EQ to the signal, e.g., the bass boosting, would help... but WTH... easy test...
Personally I'd use a 1.5 V, and would only apply the battery to the LF speaker posts (especially with a 9 V).
02-07-2005, 06:03 PM
Originally posted by Tour2ma
... Personally I'd use a 1.5 V, and would only apply the battery to the LF speaker posts (especially with a 9 V).
You are such a wussy...
02-08-2005, 09:30 AM
Just to back up a bit on this thread - is that correct that you should get continuity on the IC cable between pin-pin but *not* blade-blade? That doesn't seem right.
02-08-2005, 12:15 PM
That is correct.
02-08-2005, 12:28 PM
So how does it work? Is there a transformer in the path??
There is no transformer in the path on the 2.3. The crossovers take care of the SDA effect somehow. This model used a cable with continuity only on the pin pin connection to protect against ruining an amp without common ground.
02-08-2005, 12:41 PM
Thanks! So although the IC termination (connectors) has two terminals (pin & blade), only one has continuity to the other end? On purpose? Strange indeed, but thanks for the info.
02-08-2005, 12:44 PM
The blade helps support the pin.
To confuse you even more, the AI-1 cable does use a transformer.
02-08-2005, 02:29 PM
Ahhh, that makes sense now (using the pin for support).
Having no DC coupling with the AI-1 makes sense too.
02-10-2005, 01:13 AM
Well, this gets more interesting day by day. I pulled the input terminals and the crossover connections and cleaned them(sort of) by just putting them on and off a few times. Then I started pulling off the speaker wires one at a time while I fed a source. The units are bi-wired. I noticed that while putting on and off the leads for the mids there was a little difference in sound, but not much. After a lot of frustration, I remembered reading somewhere that some drivers need a lot of time to break in. As I said in the prior post, I've only got about 50 hours on the units, and they have been in storage since 1996. I rarely listen above 70 db or so. Maybe the drivers are stiff like I am when I wake up, I thought. So I put on a bass heavy piece, cranked up the volume and went to town for a couple of hours. This caused the cats to head for the far corners of the basement. When I got back, I was behind the units fiddling with the leads and I noticed the bass seemed stronger behind than in front. Yup, walk to the front, no bass. At that point I dug out the manual and noticed that Polk says the closer the speakers are placed to the wall the better the bass. I've had the units out 2 feet for better imaging. So I decided to move them back and see what happened. Got in front, and no bass again. Backed up so I could kick in the drivers and end it all, and noticed I passed through a wall of low sound. Hmmm. Going back and forth there was a peak, then cancellation about every 18 inches. Really weird room acoustics. Anyway, I shoved the things flat against the wall, and what? Fat midrange. Put on Bob Marley, pulled the wires to the tweeter and juiced the volume for another hour. I just put on Ray Charles' Genius Loves Company and cut 5, Fever ,had enough bass I had to turn off the sub. It would seem I have fixed the problem. Bad connections, inactivity, not enough loud break-in , and bad placement. What a combination. Never would have thought my "old" speakers might have been too new.
I want to thank all the wonderful people who responded with suggestions. In a time of crisis, it's good to know there are fine individuals out there.
02-10-2005, 01:39 AM
So, things are looking up....great!
FYI, I have mine 5.5" from the back wall and attached with the Bass Brace. Are yours on carpet or hardwood?
02-10-2005, 09:44 AM
Good Job CHM. Goes to show when you stay at it and not be afraid to try an improve things you can get some good benefits.
Glad you are enjoying those old (new) speakers!!
02-10-2005, 12:40 PM
My units are about 2" from the wall, no brace, and sitting on the little metal feet they came with. The floor is uncarpeted for the moment, currently OSB.
02-10-2005, 12:46 PM
Ok, if you can rig up a Bass Brace or install spikes you will notice better bass performance.
02-10-2005, 02:49 PM
Originally posted by chipperman
I rarely listen above 70 db or so. I think they were asleep... or bored... ;)
Glad to read they are coming alive... but you either have them in the least friendly room in the history of music or there is still a phasing issue...
You've been talking bass - bass - bass... How are they imaging?
02-11-2005, 12:09 PM
Well , I didn't mention imaging because that, in a nutshell, still exceeds anything I've ever heard. On some recordings, the sound is three feet outside of the speaker on either side. But, I do have a problem, and I need some feedback from you that have heard a lot of speakers. Let me preface this by noting that it might be my equipment that causes the problem. I have a 15 year old Yamaha 910u CD player, an Adcom 555, and a VTL model 2 preamp. Here's the problem. The top end sounds a little congested. When playing acoustical piano, it sounds like a speaker. I've demoed the same disc lately with a variety of small towers from PSB, Focal, Paradigm, etc, and all of them are so clear that I can hear the felt on the hammers hitting the strings. It's like the piano is in the room. I noticed the same clarity on the top end with Vandersteen 3's. If I upgrade the tweeters and redo the crossover, will I get the clarity I seek, or is is time to move on? To be fair, all the speakers I've listened to are being driven with components that cost more than my first house. I've got a pair of Sennheiser 650 headphones coming, so I thought I could at least see if the problem is the CD player, as it has an outlet for that. And, I'm pretty sure the preamp is about as clean as it gets.
Here's the killer. Nothing, and I mean nothing, I have listened to is any better in midrange with male voice and drums. I use Sheffield's drum test disc, and on cut 5 the kick is something a lot of others have trouble with. On the Vandersteens, I could not tell what the instrument was. Garbage can or cardboard box, but not drum.
I know a lot of you out there must have heard other things, too. Any feedback?
P.S. For the past couple of days, I've run the speakers full time, and while the highs are the same, everything seems to be loosening up a lot in the mids and bass. They're right, if you don't use it, you lose it.
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