SDA speakers without the interconnect cable

Schurkey

I was in an experimental mood last night; and the thread on SDA effect vs. Headphone amplifier "blend" circuitry piqued my interest. http://www.polkaudio.com/forums/showthread.php?t=65802

I've had a pair of SDA 1B speakers since the mid-80's. They were my first pair of "real" speakers, replacing a homemade pair of corner horns on the order of Klipschorns--but even bigger and less sophisticated.

I played the speakers with and without the cable when I first got them; and I remember that there was considerable difference with and without the cable--but--now I think I understand why so many SDA speakers are sold without the cable. I'm starting to think there's something wrong with my crossovers; or the SDA drivers are wired out-of-phase. Or something. Damn, these speakers sound SO MUCH BETTER without the cable in place!"

There's a "phase-y-ness" that interferes with the sound clarity that disappears when the cable is disconnected. I remember from all those years ago that the sound was different--but I don't remember it being THIS DIFFERENT.

Is there a common problem that could account for this massive change with and without the interconnect cable? My crossovers and tweeters were replaced under warranty sometime around 1990; but as far as I know they used exact replacement parts--it was, of course, done by an authorized Polk dealer.

heiney9

If you have the model with 2 tweeters side by side this might explain it. Early generation SDA's used one of the tweeter (the one on the outside) for dimensional information. Later they discovered they could get a much better more realistic (if you will) effect by limiting the dimensional frequencies to a very narrow band which came from a mid driver only.

The early models with the dimensional tweeter sound how you describe your 1B's. They tend to be really phasey sounding and you can get some really extreme effects which come from way outside the speakers or behind you.

One fix some have done is to disconnect the dimensional tweeter and still run with the SDA cable.

If your model doesn't have the side by side tweeters then you have other issues because IMO disconnecting the cable makes the speakers sound flat, 2 dimensional and lifeless.

H9

dcmeigs

You might find this thread relavent to your plight. http://www.polkaudio.com/forums/showthread.php?t=65993

I am moding some 1As which have the side by side tweeters and I intend to eliminate the array tweeter for reasons stated above. Posts on that thread explain the rationale. Hope this will help.

I'd unplug the "outside" tweeters and then connect the interconnect cable and give it a listen. I wish I had tried this but it's to late now; the crossovers are on the bench. If you do I'd love to hear the result.

hoosier21

just checking, you are in the equal triangle when listening right?

F1nut

The 1B has two tweeters, mounted vertically, acting as an point source, so no SDA tweeter.

I think the first thing you should do is check for drivers wired out of phase.

Schurkey

F1nut wrote: »

The 1B has two tweeters, mounted vertically, acting as an point source, so no SDA tweeter.

Yup, that's my 1Bs, alright.

F1nut wrote: »

I think the first thing you should do is check for drivers wired out of phase.

Or an entire speaker out-of-phase. I need to dig into this, 'cause SOMETHING isn't right...

ben62670

If the entire speaker were out of phase you would have very big problems. Like a blown amp. 1B's have a blade blade.

F1nut

Another thing you should check is that you actually have the correct drivers installed. They should all be labeled MW6509.

Curious...why did you have to have all the tweeters and drivers replaced?

dorokusai

A loudspeaker out of phase won't blow up an amplifier, unless there are bigger issues.

ben62670

Blade blade SDA's are a different animal than any other speaker. Positive sent to positive is a very bad thing with the early SDA's.

Schurkey

ben62670 wrote: »

If the entire speaker were out of phase you would have very big problems. Like a blown amp. 1B's have a blade blade.

I wouldn't have expected amp problems from an out-of-phase speaker. The two speakers are ordinarily fed a signal that is different (although often related, especially in the bass) so having one out-of-phase shouldn't present an impossible electrical load--just an unusual one.

(right?)
[later edit--I deliberately swapped speaker cables on one speaker, and created no smoke. Any sense of localized imaging disappears, though. Stereophile Test CD (and Test CD 2) have in-phase and out-of-phase tracks; along with pink noise tracks that are correlated and un-correlated. Playing those produced no smoke, either--but out-of-phase is clearly audible as is uncorrelated noise.]

F1nut wrote: »

Another thing you should check is that you actually have the correct drivers installed. They should all be labeled MW6509.

Curious...why did you have to have all the tweeters and drivers replaced?

The midrange units have not been replaced; the one that I've checked is indeed an '09. (I was hoping to discover that my speakers were early-production 1C in the 1B box; but the '09 driver proved otherwise.)

One tweeter was replaced because it died; when the problem soon repeated with more dead tweeters, they were all replaced along with the crossovers. It is possible--but somewhat unlikely--that this was an amp (receiver) problem--I didn't play that loudly; and the receiver was rated at 160 watts into 4-ohms. Mostly the on-board wattmeters rarely went above 2 watts; and very seldom above 20 watts. Yes, I understand that wattmeters are not particularly accurate.

Eventually I did have problems with that receiver; it was replaced with an Aragon 4004; and not long ago an Aragon 8008BB. I'm now wondering if I crossed the speaker wires when I swapped amps around. I'll be looking into that today.

F1nut

Aragon 8008BB

There's the problem, it's dual mono and therefore non-common ground. You can't use non-common ground amps with your blade/blade 1B's unless you can tie the negative outputs together, which only the manufacturer can tell you. The pin/blade SDA's can use the AI-1 interconnect cable to resolve the non-common ground issue, but you can't use that cable with the 1B's.

I would stop using your set up until you resolve that issue as it can damage both the amp and the speakers.

ben62670

F1nut wrote: »

Aragon 8008BB

There's the problem, it's dual mono and therefore non-common ground. You can't use non-common ground amps with your blade/blade 1B's unless you can tie the negative outputs together, which only the manufacturer can tell you. The pin/blade SDA's can use the AI-1 interconnect cable to resolve the non-common ground issue, but you can't use that cable with the 1B's.

I would stop using your set up until you resolve that issue as it can damage both the amp and the speakers.

Serious +1 here.

Systems

Being dual mono doesn't necessarily mean it is not common ground.For instance Bryston make several dual mono designs that are common ground.

MillerLiteScott

I want to test my integrated to see if it is common ground even though it is dual mono. I am running an Avel torodial isolation tranformer because I am to chicken to find out the hard way.

ben62670

GV#27 wrote: »

Being dual mono doesn't necessarily mean it is not common ground.For instance Bryston make several dual mono designs that are common ground.

This is true, and I know I'm not telling you much, but even dual mono's should have there grounds tied together at the speaker terminals with some heavy Ga wire. H9 will probably chime in on this. I have done a fair amount of work on Adcom's, and know some guys that either worked for Adcom directly, or indirectly. They all say tie the grounds together at the speaker terminals.

ben62670

MillerLiteScott wrote: »

I want to test my integrated to see if it is common ground even though it is dual mono. I am running an Avel torodial isolation tranformer because I am to chicken to find out the hard way.

A simple test is to take a multi meter, and test for continuity(near zero ohms). If you have continuity you are safe to tie the speaker grounds together via a short piece of heavy speaker wire.

Systems

ben62670 wrote: »

This is true, and I know I'm not telling you much, but even dual mono's should have there grounds tied together at the speaker terminals with some heavy Ga wire.

It is the big amps using a balanced (bridged)configuration in their output stages that will not take kindly to being strapped together.:eek:

ben62670

GV#27 wrote: »

It is the big amps using a balanced (bridged)configuration in their output stages that will not take kindly to being strapped together.:eek:

Good point. Don't take 2 amps bridged mono, and tie the grounds together. A friend of mine did this, and it was a very bad thing.

Systems

ben62670 wrote: »

A friend of mine did this, and it was a very bad thing.

No sh#t.:D


Amps refered to as non common ground are essentially made up of two bridged amps in one chassis.

ben62670

No, it was more like Oh ____:eek::o
I don't remember how many drivers were lost that day, and the exact damage to the amp/amps, but it was not a nice thing.

F1nut

GV#27 wrote: »

Being dual mono doesn't necessarily mean it is not common ground.For instance Bryston make several dual mono designs that are common ground.

That is true and I stand corrected, although I don't really consider them to be true dual mono.

dorokusai

Almost every Parasound amplifier is a dual mono design, common ground as well. At least since the HCA-2200 MkII.

heiney9

GV#27 wrote: »

No sh#t.:D


Amps refered to as non common ground are essentially made up of two bridged amps in one chassis.

Or in the case of newer Adcoms have a primary and secondary (or multiple secondary) winding. They are not common ground. (except the smaller Adcoms)

Schurkey

The Aragon 4004, and the 8008ST and 8008BB are all common-ground amps as are the rest of the "Classic" Aragon amp line.

The Aragon Palladium series are factory-bridged monoblocks and not compatible with Polk SDA blade-blade speakers.

Systems

heiney9 wrote: »

Or in the case of newer Adcoms have a primary and secondary (or multiple secondary) winding. They are not common ground. (except the smaller Adcoms)

Are these bigger Adcoms using a balanced(bridged) output stage?I would be interested in learning more about what Adcom has done,but amplifiers can have multiple secondary windings and still be common ground.My Bryston 3B has multiple windings in the form of two completely separate toroids but the center taps are connected together at a star or common ground point.

Systems

Schurkey wrote: »

The Aragon 4004, and the 8008ST and 8008BB are all common-ground amps as are the rest of the "Classic" Aragon amp line.

If your 8008 was not so you would have found out very quickly when hooking up to those SDA's.

F1nut

GV#27 wrote: »

If your 8008 was not so you would have found out very quickly when hooking up to those SDA's.

Not necessarily. Some have reported no problems running their SDA's with non-common ground amps, although this is rare and it is definitely better not to try it. Hence, my comments not to do it.


Schurkey, sorry to add to the confusion. I read that the 8008BB was dual mono and thought that angle was worth persuing. Obviously, that's not your issue.

Systems

F1nut wrote: »

Some have reported no problems running their SDA's with non-common ground amps, although this is rare

Yeah I would be willing to bet box of cheap SDA mod approved 2.2uf caps, that most non common ground amps would not react favourably to this.

thus comments not to do it.

You were absolutely correct in warning him of this possibilty.

Joe08867

If you are getting a phasey sound maybe you have the speakers on the opposite side they should be on.

Easy to do with the 1B's as they look identical from the front. Check the back of the speaker to see if the right is on the right side and left well you get what I am saying.

If they are setup backward they would sound like crap. I did this with my SDA2's once and thought something went wrong with my speakers.

Schurkey

Correct left-to-right speaker boxes. Correct left and right channel wiring.

Correct relative phase as verified by Stereophile Test CD 2

Both tweeters working as verified by test tones on Test CD 2

Polarity of drivers verified by unscrewing 'em all and looking.

All 4 mid-drivers working as verified by feeling for vibration when re-connecting the wires to the drivers.

If the crossover is somehow screwed-up; well, I have no idea how to begin checking it. The crossovers don't LOOK fried; no caps are dripping goo and no wires are toasty brown. I didn't pull the boards out to check for broken solder traces--and re-soldering broken traces is about the limit of my electronics experience.

I don't know what's up--but--I absolutely prefer the sound of the speakers with the interconnect cable unplugged. Clearer in the midrange; vocals are more intelligible.

Maybe I'm just hungry for a change...