Remember Polk Audio SDA speakers?

I do, especially looking over them in Stereo Review ads. They had numerous mid range drivers and tweeters mated to a passive radiator. Their big model SDA SRS (Signature Reference Series) had like 8 mids, 4 tweeters and a 12-15" passive radiator in a huge cabinet. I only got to hear the big model once, and a smaller model once, and I was young enough that any sonic impression has long faded away (except that they had a sub-harmonic synth on the big model, so the bass shook the showroom). Did anyone here ever own a pair, or remember if they stacked up well against other "traditional" audiophile speakers? Have you heard them recently? Was the SDA (Stereo Dimensional Array) hokum, or effective? Thanks.

 

Here's the model SDA SRS 1.2TL.

 

WTF?

 

Man, I was a huge Polk fan and have owned many models. Back in the day, they were audiophile quality and had some pretty interesting stuff.

I have used for some time, the Monitor 7, Monitor 10, Monitor 10b, and the Monitor 11 which I believe was quite rare. The 10 series are classics and delivered amazing bang for the buck. they were a fairly large, boxy speaker though and didn't fit well on the floor or on stands. I had them on a set of dressers in one house and on milk crates in another. That was about the best that you could get in terms of height and stability, short of building custom stands. I think that I had a pair of short Polk stands for one of the pairs too.

I have heard the SDA series twice. I had moved on to other brands by the time they came out. Once was at a guys house who had the small set, supposedly an upgrade to the 10B but it sounded and looked more gimicky to me in that model as it was really too small to benefit from it. The next time was about a year or two ago when I restored a set for a guy that came into my shop. He didn't know what they were all about but got a good deal on them froma fellow who was using them to DJ with! It was missing the special link cable and I had to custom make one from scratch. perhaps I could have ordered one from Polk but I guess I had some things here to do it with, I don't recall.

The SDS system was odd and it was designed to provide a deeper soundstage. They designed it kind of like the Bose idea of having some reflected sound but improved that concept by doing it directly and electrically. Since the Bose relies on the room to achieve any sort of effect, perfect placement and a lot of trial and error is required and their drivers never had the same resolution to offer realism for me as did the Polks anyway. The Polk SDS system used an array of drivers and x-over as was typical in any system in each cabinet. They also used a passive radiator, more drivers, and greater cabinet volume to allow their ubiquitous 6" driver to be used in all systems. In those regards, the SDS was the same as the standard series. What made them special was the addition of a 2nd complete x-over in each cabinet and a set of drivers connected to these. The 2nd x-over in the left cabinet actually controlled the 2nd set of drivers in the right cabinet via the umbilical cable that tied the two speakers together and they "talked" back and forth in this way. These x-overs were wired out of phase so that you had each speaker producing both in and out of phase sounds. That added a 3 dimensional effect to the sound with standard speaker placement. The set that I repaired used three mid drivers and a dome tweeter for each channel, plus a 2nd mid and tweeter for each, wired to the SDS circuit. Despite the funky idea and cumbersome size, they rocked. Never were they the last word in resolution or clarity but they were far beyond that of mass market products. Now, they are mass market products...
-Bill

 

I had the SDA speakers. The dang tweeters kept blowing. Poor build quality in those days.

 

That's odd. My tweeters were fused on my Monitor 10s. I can't remember about the SDA but the build was excellent by any standard. They would only hold a certain amount of power though, as would any speaker. I remember having my Monitor 10s painfully loud on occasion and I had a 200wpc amp connected to them. Those only used one tweeter as well. I don't think they were the most efficient speakers, so certainly creating very high levels could be more damaging to them.

The larger SDA speakers like those in the photo had multiple tweeters and I can't imagine blowing those ;-)! Cleaner power and more sensible levels almost always prevent speaker damage. Some amplifiers can just clip very nastily and so take out tweeters quite easily.
-Bill

 

I believe I read that Polk considered reintroducing the SDA line a few years ago.

I had the opportunity to listen to a couple of SDA speakers at a friend's. They were great for unfamiliar recordings but with music I know by heart, the extra dimensionality was distracting.

With an Art of Noise CD with a motorcycle going from side to side the effect was incredible. The sound started way way beyond the right (I believe) speaker and ended way way beyond the left one.

 

I remember hearing a smaller set of SDA models back in the 80s and was impressed by their imaging capability. Though I guess Polk thought they could still produce good stereo images with conventional designs because the SDA series didn't seem to last for long.

Based on what I read at the time, by using that second set of woofers/tweeters, what Polk was trying to do was prevent the sound from the left loudspeaker from reaching the right ear, and the sound from the right speaker from the left ear. As KT88 alluded to above, this was mostly accomplished by having one set of drivers wired out of phase from the "regular" drivers in the other speaker cabinet on the other side of the room. So any sound from, say, the left regular driver set that wasn't supposed to be reaching the right ear would (theoretically) be mostly eliminated. And in turn this would help to refine and stabilize the stereo image created by the regular set of tweeters/woofers.

 

I own a pair of SDA-2's (original build with SL-1000 tweeters). I keep them because after all these years there is still nothing quite like them (for better or worse). On some recordings, the soundstage is amazing. On others (as noted), it just sounds odd/distracting. Other companies tried different methods for the same result (Carver Sonic Hologram being the best example), but Polk did it best. Polk later released upgraded tweeters (silk dome) that did not have the resonant peak found in the stock units. Big improvement. Actually, with the new tweeters, and a rebuilt crossover, they hold up pretty well. Still can't keep up with the best of modern drivers in terms of resolution but they are fun to listen to, and don't screw anything up.

Lee, if you kept blowing tweeters, did you ever replace the polyswitches? If they were blown, and/or they were underpowered (the larger SDA's were almost as bad as electrostats when it came to nasty loads), that would explain what happened. Can't say I've had any problems myself, and its nice that I could always call up Polk and get someone on the line who knew what they were talking about. I'm hoping thats still the case now that they've been bought, but I haven't tried.

Oh yea, for more reading:

http://www.polksda.com/