Tell me about my SDA's

Thewiz666

I have a set of old Sda's that I'm not sure as to how they rate in the audiophile hierarchy. They say that they are SDA-SRS-2 in the serial number line, but I don't remember much about those older speakers from the late 80's. Could someone tell me more about them and their capabilities? After reading some postings on here, I have doubts as to how good people think that particular model is. When I first found them, I thought they were 1C's but I guess that they look identical from what I remember.

madmax

All the SDA's are great. If you have the interconnect in place and the speaker placement is good then you already know. If not, set them up correctly (3' from side walls, both speakers in line -not angled- and sit at least 7' away in the center) and be happy you own a pair!
madmax

Thewiz666

Yes, they are definately wonderful. When I first found them at a consignment store, they had been set up backwards so when I asked to hear them before the SDA cable was in place it was kick ****... but when the cable was used they sounded all echo-ey and funny. That's how I learned why they are labeled R & L. I appreciate the placement recommendation, I hadn't really done much with them except for the parallel allignment in regards to my position. I guess I'm just wondering how this model I have stands up to other SDA's in the family and if there's any updated/different drivers or something I can add to it to improve what's already awesome with them.

rskarvan

Well, since you asked... here is a reprint I once found:

The following is a brief outline of the physical and design changes that mark the evolution of the Polk SDA series speakers.

The original SDA 1 utilized two tweeters, four mid-bass drivers and the flat surfaced passive radiator in a floor standing cabinet.
The SDA 2 was essentially the same as the SDA 1, but minus one SDA array driver for a total of three vs. four in the 1.
The SDA-CRS was a bookshelf type speaker using two tweeters, two mid-bass drivers and put the passive radiator on the back.

The changes relevant to these models involved the discovery by Polk engineers that the SDA feature did not need to involve the high frequencies so they took one tweeter away from the CRS and went to a vertical arrangement on the 1’s thus the CRS+ and the 1A’s. The 2 saw the removal of a stereo mid-bass driver and a tweeter, thus the 2A was born.

Among the larger models, the SRS’s, the largest one was designated as the SRS, utilizing eight mid-bass drivers, four vertically arranged tweeters down the center and a large, flat passive radiator. The SRS-2 was fairly large cabinet housing drivers in a manner that resembled the large 1C, but with the tweeters in the center of the mid-bass drivers ala SRA.

Changes to the SRS to become the 1.2 and later 1.2TL were little more than crossover upgrades and the use of the Polk “Tri-laminate” tweeter (TL). However, changes to the SRS-2 were a little more involved. They included the addition of a tweeter and the addition of two extra stereo mid-bass drivers, for a total of six mid-bass cones and three tweeters. Subsequent changes also involved crossover updates and the inclusion of the “TL” tweeter, and one other twist. Apparently some owners of early models complained of a lack in bass response, so Polk designers added “doughnut” weights to the upper and lower-most mid-bass drivers to increase driver mass for improved bass response.

The matter of the SRS 3.1 TL is a story all its own. Period. It was introduced in 1990 and had very little in common with the other models. It used a cone shaped radiator as opposed to the flat ones in the other models. It only incorporated one SDA driver in opposition to the stereo array instead of mainly an equal number of them. It also had one other feature not found on any other model, a shield placed between the tweeter and the mid-bass driver directly above it. This was supposed to aid in the tweeter’s dispersion pattern in relationship to the line-source array of the other drivers. The larger models used multiple tweeters in a line source array of their own to do this.

The original models are not as versatile as the updated later ones. They were only capable of being driven by a common ground chassis amplifier. Later models could make use of a non-common ground amp interface cable that replaced the original interconnect cable for use with a bridged mono type amps. Therefore, older models have had high introductory retail costs, but are less useful today so are worth much less in comparison with the used market value of later models.

There is much to the SDA speaker than meets the eye. There are those who say that the operating nature of these units is unnatural and not how music is supposed to be reproduced. Those who are familiar with the results of Polk’s SDA technology know and love the sound they produce, as it is a passive manipulation of the audio signal not an active one. Polk’s SDA “process” does not introduce any outside influences to the audio signal to achieve its goal. It merely re-directs what’s already there in a manner that uses the existing signal to cancel itself, in a nutshell.

juice21

rskarvan - that is some great info on the SDA's, where did you find that at?

TroyD

...great reading material.

Troy

wangotango68

is that shield the story is talkinf about on the outside? my rta 15's have a shield just above the tweeter that is at a 45 degree angle.


scott:cool:

rskarvan

Scott,

The tweeter shield is identical to the one on my 3.1TL's.
Its kind of a hokey look; but, hey, if it helps.

I suspect that your 15TL's probably sound A HECK-OF-A-LOT like my 3.1TL's. My 3.1TL's have four vertical drivers and one offset SDA driver. Your 15TL's have two passive radiators (front and back) vs. my one larger pr on the front.

Anyway, mine sound good as I presume yours do also.

I had this on my hard-drive. I think I got it off Mike's yahoo site. I ran it thru an OCR (character recognition software) and did a little post-editing to clean up the conversion. I have no idea who originally authored this document - and, I can't confirm the accuracy of it either - other than to say the 3.1 paragraph is pretty much right on the money. The 3.1 was a 1-year product only. Reasonably rare.

wangotango68

ron how tall are your 3.1's?

scott:cool:

Thewiz666

After reading this, I'm not sure what model I have now. If you say the SDA-2 only has 3 midrange per cabinet, mine has 4. 2 for stereo and the other 2 for the SDA. The tweeters are vertically alligned above the 4 mids and they are centered down the middle of the cab. Maybe I misinterpreted what I was reading though.

rskarvan

Scott,

The 3.1TL's are 48.5" tall.

Ron

stubby

If your tweeters are above the midbass then you probably have some 1C's. If the tweets are between the midbass, then I would say you have the SRS 2's. Measure your cabinet width if still in doubt. If its about 21" wide you have SRS 2's. The 1C's aren't that wide. I also presume your rear labels are like gone or illegible.

Stubby

Thewiz666

They measure to be 15 7/8" wide, 10 7/8" deep (w/o grille), and about 42" tall plus the approximate 2" base section they sit on. The labels appear to be in great shape, each telling of the R or L channel at the top, then giving a wiring, SDA cable plug, and alignment diagram as to how they should be arranged for optimal performance. I hope this info helps more with my inquiry. Thanks in advance for more info.

Oh, BTW, the tweeters are above the mids, but they are centered down the middle so that they would be on a line bisecting the cabinets looking at them from the front side.

stubby

My best guess would be some early model 1C's. You could also check your serial numbers. My 1.2's have the model number with the SN.
BTW, I just noticed your location. I'm about 35 miles south of you on the Kansas side.

Stubby