My first audition of Polk SDA-2

Oktyabr

Hi all!

First of all let me say that I have spent the better part of a day searching and reading these forums but I still have some questions I'm a bit foggy about and time is of the essence. I'm sure the answers are in here, somewhere, I just haven't found them yet! Promise when I have more time that I will keep reading :cool:

Here is the short and sweet: I'm going to audition a pair of speakers advertised as "SDA-2" in about another five hours (from the time of this posting) with a very serious intent of buying them. I've never actually seen a pair of SDA's so of course I've never heard them before either.

They are advertised as not having that special SDA cable but from what I've read here that shouldn't be too difficult to manufacture if it turns out these are keepers.

Questions:

1) I intend to power these with an Adcom GFA-555mkII. I always thought this was a "common ground" amp but thought I would check here first if others are powering SDAs successfully with this amp? If I buy these SDAs can I power them with this Adcom? Can I use that special SDA cable with my Adcom?

2) What is the "bass radiator test" and how do I perform it? Any other SDA specifics I need to know when looking at these?

3) Without the SDA cable what should I expect to hear from the drivers when auditioning these?

Many, many thanks in advance!

I will probably buy these unless there is something massively wrong with them that the seller hasn't revealed to me yet. Will post back here with the results!

concealer404

1) That amp is fine.
2) The bass radiator test: Push in on the passive radiator, and you'll see the midrange drivers come out a bit. If they return to their original position very quickly, then there's some air leaks. I dont know what the exact time should be for these speakers, but if it seems really fast, then it's leaking. I'd expect a good 5 seconds or so.
3) Without the SDA cable, you'll be lacking the SDA effect. Just make sure that all drivers are functioning properly, then buy them, and make the cable later.


Welcome! And good luck.

hearingimpared

concealer404 wrote: »

1) That amp is fine.
2) The bass radiator test: Push in on the passive radiator, and you'll see the midrange drivers come out a bit. If they return to their original position very quickly, then there's some air leaks. I dont know what the exact time should be for these speakers, but if it seems really fast, then it's leaking. I'd expect a good 5 seconds or so.
3) Without the SDA cable, you'll be lacking the SDA effect. Just make sure that all drivers are functioning properly, then buy them, and make the cable later.


Welcome! And good luck.

Two to three seconds.

concealer404

hearingimpared wrote: »

Two to three seconds.

Ah ok, cool. My Monitor 7s were quite a different animal i guess.

hearingimpared

Well that's what I've been advised concerning my 1.2 TLs. Could be different for a smaller enclosure.

concealer404

hearingimpared wrote: »

Well that's what I've been advised concerning my 1.2 TLs. Could be different for a smaller enclosure.

Oh... there's a lot more drivers in the 1.2TLs, too, so more potential for air leaks around the drivers.

JohnLocke88

Oktyabr wrote: »

1) I intend to power these with an Adcom GFA-555mkII. I always thought this was a "common ground" amp but thought I would check here first if others are powering SDAs successfully with this amp? If I buy these SDAs can I power them with this Adcom? Can I use that special SDA cable with my Adcom?

I believe so; But a) check with the consensus on this forum, or better yet, give Adcom a call. Either way, you can get another amp if necessary.

Oktyabr wrote: »

2) What is the "bass radiator test" and how do I perform it? Any other SDA specifics I need to know when looking at these?

This tests for air leakage, BUT ALSO FROZEN DRIVERS. Air leakage can be fixed relatively easily; a frozen driver WILL need to be replaced. If any of the drivers do not "extend" outward, then it is frozen and is faulty.

Oktyabr wrote: »

3) Without the SDA cable what should I expect to hear from the drivers when auditioning these?

They should still sound amazing. If something is "off" to your ears, then something is probably wrong. Using SDA's with the cable is great, but they sound good without it too.

In this regard, make sure you got functional tweeters. Bring something with high frequencies (above 6 kHz).

Good luck.

Also for reference,

SDA-2 (original) - 3 midwoofers per cabinet, 1 tweet, 1 Passive
SDA-2A - 2 woofers, 1 tweeter, 1 Passive This will be in a wood colored veneer with a "pedestal" on the bottom.

SDA-2B - 2 woofers, 1 tweeter, 1 Passive; This will be in a black wood veneer with a pedestal OR a cabinet with wood endcaps on the top and bottom with cloth sides.

Oktyabr

Thanks for all the help guys!

Ok, I bought them! Question is... what exactly did I buy?!?! The tag on the back says "SDA II" (yes, this is the pair from the Seattle CL, in case anyone was wondering). The IC plug looks like two slots, the top one smaller than the bottom. It's a vinyl wrap, not veneer and yes, these have the "pedestal" on the bottom.

I apologize in advance for the poor quality of the following shots... only had my iphone on me at the time (click thumbnail for larger version):






The finish and the grills are 9/10, near perfect. The surrounds seem to be rubber, all the drivers look very good with the only exception that one of the surface wires going to one of the tweets is loose for the last 1/8" or so but still makes a solid connection. These passed the "bass radiator test" with flying colors and none seem frozen.

They sound very good, very different from what I'm used to listening too, but good just the same. If anything sounds weak it might be that the "R" speaker seems to be weak in the mids. I'm going to clean and double check my connections again (already cleaned and rotated the fuses) and will eventually pop out the suspected mid and check the connections there too.

While I'm at it what should I be considering in the way of fabricating a replacement IC wire for these and again, any more opinions on whether or not these will work with my Adcom 555mkII amp with the IC in place?

Oktyabr

Ooops! "SDA II" = "SDA 2" http://www.polksda.com/sda2.shtml

JohnLocke88

Those are the very first version of the SDA 2's. They have SL1000 tweeters, and MW6600X's for the midwoofers.

To make the cable, you can use these:

http://www.alliedelec.com/search/productdetail.aspx?SKU=7503200

(you might try looking around elsewhere for a better price, ebay perhaps)

and some form of 2 conductor wire (speaker wire or RCA cable.) Speaker wire may be a bit easier to work with and will be higher gauge (14-16 AWG works well).

Good luck.

jimbo1421

Nice score, OKtyabr. Here is a thread about common ground amps; more than you really wanted to know: http://www.polkaudio.com/forums/showthread.php?t=80063&highlight=common+ground+test

If you do a search for "interconnect" you will find some very good ways of upgrading your IC. But if you just want the connectors for the existing sockets, these will fit the bill: http://www.alliedelec.com/search/productdetail.aspx?SKU=7503200

Paden501

Congrats on the purchase! I'm sure that you will like them. As mentioned above, those look like the original SDA 2s.

kcoc321

Oktyabr wrote: »

Thanks for all the help guys!

Ok, I bought them! Question is... what exactly did I buy?!?! The tag on the back says "SDA II" (yes, this is the pair from the Seattle CL, in case anyone was wondering).

Dang, are those the ones that were two bills in Bellevue....
Sa-weet deal.....:D

ben62670

The GFA-555 will drive them fine.

Oktyabr

Thanks gang!

Ok, so if I just improvise a speaker wire (I have LOTS of it in several different gauges and grades) to test this SDA effect... can I just jam some speaker wire in both slots? It sounds like the top slot must go to the bottom slot on the opposite speaker and vice versa?

I'm eager to see what this effect does in my room... and it's probably not a bad thing to try it before I go out buying and manufacturing a cable.

hoosier21

Oktyabr wrote: »

can I just jam some speaker wire in both slots?

yes you can

Oktyabr

kcoc321 wrote: »

Dang, are those the ones that were two bills in Bellevue....
Sa-weet deal.....:D

Thanks! And better yet he brought them to ME to demo! Happened to be going to my neck of the woods (I'm in the Tacoma/Puyallup area) anyway and had told me in an email when I inquired about the sonic integrity of these, "There is nothing like demoing them on your own system."

Super nice guy too.

Oktyabr

hoosier21 wrote: »

yes you can

Thanks!

And am I correct in needing to reverse the slots between the speakers? So top slot goes to bottom slot, etc?

Paden501

Oktyabr wrote: »

Thanks! And better yet he brought them to ME to demo! Happened to be going to my neck of the woods (I'm in the Tacoma/Puyallup area) anyway and had told me in an email when I inquired about the sonic integrity of these, "There is nothing like demoing them on your own system."

Super nice guy too.

WOW that's pretty unheard of.

Sorry can't help you w/ your IC question.

inspiredsports

Oktyabr wrote: »

Thanks!

And am I correct in needing to reverse the slots between the speakers? So top slot goes to bottom slot, etc?

Welcome to Club Polk.

http://www.polkaudio.com/forums/showthread.php?t=55888

First Schematic in Post #3 (Adobe .pdf format) shows crossover with proper interconnect pinouts.

They call the type of connection on your speakers "Blade/Blade" (as opposed to an alternate "Pin/Blade" design used in more modern models.

It appears after carefully studying the diagram that A & B poles are crossed INTERNALLY and are different in the left and right cabinets.

I'm positive the 2 stock Blade/Blade Interconnect cables I personally have owned were straight through small to small / large to large. One of my cables came with SDA-2B's I purchased brand new in 1987, and the second was purchased directly from Polk in 2008. Based upon the 21 year span in cables, I think the cables are always straight through and any "crossing" is done in the cabinet.

cnh

See post below, looks like I made a booboo\

cnh

Oktyabr

inspiredsports wrote: »

Welcome to Club Polk.

Connect 1 wire small slot to small slot, another wire large slot to large slot.

Whew! I was *just* about to wire it small to large, large to small based on what I read in the schematics found here: http://www.polkaudio.com/forums/showthread.php?t=55888

Where it says:

Right Channel:
A = pin #1
B = pin #2

Left Channel:
A= pin #2
B= pin #1

But now I see looking at the little diagram near the bottom that the right and left speakers are wired opposite to each other internally so yes, you are right, large to large, small to small!

nadams

They are very early SDA2's, indeed. My SDA 2's have the same driver arrangement (2 tweeters, 3 woofers), but utilize the later SL2000's. Yours should sound better

Paden501

Good catch.

Hey how do you have your speakers arranged? and in what size room? I want to make sure that you get the speaker placement right. Have you read the manual? The SDA1B manual is available here:

http://www.polkaudio.com/homeaudio/products/recent/sda1b/

Obviously you don't have 1Bs, but the speaker set-up diagram still applies.

inspiredsports

edited

cnh

inspiredsports wrote: »

CNH - - - This is WRONG - PLEASE EDIT IT if you see my post in time to correct your post.

I got it...Thanks...the problem is that my SDAs are rewired by the previous owner because I have two LEFTS...and I forgot about that...so one of them is rewired as a right! So are you saying that the wiring is INSIDE the Speaker...because it does have to be out of phase for the SDA effect for one side of the mid-woofers? No? You have to have wave cancellation--if they are in phase that can't happen.

cnh

inspiredsports

cnh wrote: »

I got it...Thanks...the problem is that my SDAs are rewired by the previous owner because I have two LEFTS...and I forgot about that...so one of them is rewired as a right! So are you saying that the wiring is INSIDE the Speaker...because it does have to be out of phase for the SDA effect for one side of the mid-woofers?

cnh

You will need to sort that out then internally with a VOM.

I would personally recommend you always wire the crossovers properly according to the official Polk schematic or you are setting yourself (and possible future owners) up for a problem as the Interconnect Cable (IC) should always be set up with continuity small blade to small blade / large blade to large blade.

We've had threads here going hundreds of posts deep to get to the bottom of this kind of simple, yet unexpected twist when a new buyer gets his/her speakers home.

cnh

That is in fact how they are wired so I don't think we have a problem there...previous owneer was a Polkie who checked the specs and wired them in accordance...it's fine but a bit funky! They sound great in any case....EFFECT is there!

cnh

inspiredsports

cnh wrote: »

That is in fact how they are wired so I don't think we have a problem there...previous owneer was a Polkie who checked the specs and wired them in accordance...it's fine but a bit funky! They sound great in any case....EFFECT is there!

cnh

I don't know this for a fact, but I am not certain all models are crossed like the 1984 SDA 2's Oktyabr just purchased.

What I do know is that I trust the schematics the Guru's have posted as cited in my post above, and again, at http://www.polkaudio.com/forums/showthread.php?t=55888

I also believe that all factory Polk SDA Interconnect Cables have continuity from same size to same size blades for the blade/blade versions.

Oktyabr

LOL! Thanks again guys!

I've owned a LOT of speakers (@inspired: catch some of my old posts at sound-thinking.org) but this is the first time hooking up a pair felt more like defusing a BOMB!

I guess I've read enough and looked at enough diagrams that I think most speakers designed as a mirrored pair *still have the same internal wiring* and thus in the case of this SDA interconnect it would seem more error-proof, at least reasonable in my mind, that during assembly to wire them identically and do the opposite polarity simply by putting a half twist in the wire, so to speak, before putting the plugs on the ends... sort of like a a CAT5 "crossover" cable is cross-pinned but still uses the same terminations (yeah, I'm a bit of a computer geek too).

Son just tossed down the PS3 controller in disgust and shut off the living room system so maybe I can get a little music in before bed... and try out my improvised IC!

Paden501

Write back with your thoughts. I'm really looking forward to hearing your observations.