SDA 2 no bass since birth

Ribmastert

1985-86 bought SD-2's, serial # 4520 and 4311. Two monitor 5's with a Carver MT-500t amp and a Carver C1, all new in box.

I have never have had any bass, or very very little in the SDA's. Used 10 years anyway (phase was right and tried out of phase also) Speaker position was 1 foot from rear wall, 6-7 feet apart, 2 feet from corners.

2007- Brought out of mothballs- and found some interesting things. I took them apart, and replaced 2 bad SL 2000 tweeters- (all tweeters were SL 2000) Of the 2 bad tweeters, 1 had a double sticker, underneath the top sticker, it said (written in ink pen) "stripped screw" another tweeter (a working one), also had a double sticker and had a SL 2000 sticker over an SL 1000 sticker.?? Both stickers on that tweeter said SDA2.

All bass-mid bass units are 6501's, with the exception of one. A 6500 was found in the left channel SDA array. It was a "not for resale, warranty only" (or close to that) sticker. The white wire was also wired to the + terminal which I believe is incorrect. (It's opposite on the other speaker)

Even after correcting that, they still are very weak in bass.
I love Polk, but after so many years , and then seeing this, I'm very disappointed.

These speakers have never left my possession. My monitors 5’s have always had more bass than the SD 2's.
Can any one help? - I do have Polks testing ohm chart and I'm half way thru, but have found no issues yet.

I also thought I saw someone post a wire color schematic for these speakers here, but I can't find it.

(All black / blue color wires are on + terminals currently)

Face

http://www.polkaudio.com/forums/showpost.php?p=677948&postcount=3

danger boy

Ribmastert, that is very unusual... as you say you bought them new. Someone at some point had to have gotten in there and messed them up. are they SDA 2, 2A or 2B's. can you post a picture of one of them without the grills on?

There are enough people on here who can help you get things wired right and with the correct mid bass drivers if needed. Are they sealed well around the tweeter and mid bass drivers? Any air leaks around the passive radiator?

Is there a jumper between any of the binding posts? if a jumper is missing. then of course they would sound weak in bass. Having bad tweeters would not cause you to have week bass.

Do you have the interconnect cable? What kind of amp are you using for them?

F1nut

Check for air leaks. Push the PR in and check that all the mid drivers move out. Continue watching the mid drivers, they should slowing move back. If you suspect an air leak start with the cabinet seams, then check that all the driver/tweeter/PR gaskets are in place. Also, check that the passive radiators are working properly. That is, check that the back section hasn't seperated from the main section. Replace the 6500 with a 6501.

Ribmastert

They are SDA 2's to the best of my knowledge, SDA II on the rear.
I posted a pic. I have no jumpers are between the binding posts on the outside of the speakers. (Do I understand you right? that would short my Amp?)

I can assure you; these were taken out of the box by me, and never left my possession. (I don't believe in magic either so they came this way from the factory- or a shady dealer that factory sealed the boxes??)
Seals are good and hold for a couple of sec's.
I understand tweeters have nothing to do with my bass.

My interconnect cable is the double spade type and my amp is a Carver M500T as stated.

Roy Munson

If you are using the Carver M500t amp with your SDA's it's a recipe for disaster because your amp is a non-common ground design..it could kill your amp or your speakers unless you are using a AI-1!

Edit: just saw your post above and SDA's with a blade/blade connector won't work with a AI-1 cable.

If you disconnect the interconnect cable between the speakers you can safely use your M500t but you will lose the SDA effect.

Be very careful!

Ribmastert

You all are great, thanks for such rapid feedback!

The seals are in great condition, no separation on passive radiator.

The 6500 is on the SDA array, would a 6501 have that much bass to add? The right speaker has all 6501's and has no more bass than the left.
Plus guy's the thing that gets me is that since day 1, bass has just not been there. I can also add, the 6501's will launch long before the passive even barely moves.

F1nut

Not to mention the common ground issue, but you don't have the jumpers in place?

Ribmastert

Hmm, cable or no cable, never have had bass, Called Carver last year- they said it was a common ground, now I wonder. I'll ohm it out myself- that might explain the lack of bass? even without the SDA interconnect cable?

Guess I'm lucky with the amp, been crankin for 23 years now

Ribmastert

F1 Nut,
Thanks,
Looking in the original manual, jumpers? I'm an EET and am feeling a little daft. I have the interconect cable between the speakers, but no jumper between the input terminals

Roy Munson

I had a M500t back in the day and I'm positive it's a non-common ground amp!!!!!!!!!

Ribmastert

Thanks Roy, that may be a big issue then, I might try to break out the old Kenwood reciever and try that

Ribmastert

Will the transformer cable mod let me use the Carver?

Roy Munson

You're welcome, your old Kenwood will be safer until you can track down the bass issue.

Roy Munson

Will the transformer cable mod let me use the Carver?

I don't think it will work with your model of SDA's.

F1nut

Ribmastert wrote: »

F1 Nut,
Thanks,
Looking in the original manual, jumpers? I'm an EET and am feeling a little daft. I have the interconect cable between the speakers, but no jumper between the input terminals

If you don't have the jumpers between the upper and lower binding posts on your speakers, that's going to be your problem. As for the common ground amp issue, that should not cause a lack of bass, but might cause the amp and/or speakers to malfunction as in real bad juju. However, not all situations involving non-common ground amps seem to cause a problem. I've heard of folks using non-common ground amps with SDA's and they have reported no issues. Things that make you go, Hmmmmmmm?

You can not use the AI-1 with your speakers, period.

Ribmastert

I understand F1, these are not Bi amped inputs. The SDA II's I have only have 1 + and 1 - binding post, not 4 per speaker. They also have no external fuses.

F1nut

Ah, what do I know anyway.......obviously, that's not your problem then.

danger boy

thanks for posting the picture.. that helps us to identify exactly the model of SDA 2's you have. The bass comes from air pressure build up in the mid bass drivers.. and expands the passive radiator, as I understand it to create bass. this is very odd.. but your speakers do look to be in good condition. Have you used them or have they been in storage for a number of years recently?

Ribmastert

Danger Boy, thanks, awsome condition- no smoke- I do outside ;-) storage for 3 years, on and off use since 1985

F1 Nut, Thanks,
read your Carver posts too!- (like the rebuttal to the "What's up with Polk Speakers" dude.!! like the pic!! You da man

danger boy

i reposted your picture.. my neck was getting a creak in it looking sideways.

the left driver looks kind of fuzzy.. not as clean looking surround seal as the other two. this may be letting air leak out.

Ribmastert

Thanks DB,
artifacts on the pic- surrounds are as perfect as can be for a 1985- again, leaks are not my issue

danger boy

so you're getting no bass at all.. or just very weak? it could be your amp or a crossover problem then. I'm out of suggestions now.

Marty913

"All bass-mid bass units are 6501's, with the exception of one. A 6500 was found in the left channel SDA array. It was a "not for resale, warranty only" (or close to that) sticker. The white wire was also wired to the + terminal which I believe is incorrect. (It's opposite on the other speaker)"

Very surprising considering they were factory sealed. I'm wondering whether the switched wires were simply a mistake or an attempt to compensate for other "crossover" related issues during final factory testing. Can't imagine why or what they would be but then again nothing else seems to make sense.

If the move to the Kenwood doesn't help, would it be possible to remove the PR and give us a close-up picture of the cross-over(s) on one of the speakers? I have SDA2's similar to yours (March of 1986) and would be glad to send you pictures.

danger boy

what is odd, is that bass is lacking in both speakers... if it was only one.. then I'd think, just that the wiring was wrong.. but since it's both.. that makes is really seem strange.

Schurkey

I don't want anyone to think I'm an expert; or somehow more qualified than the other folks here...but...if those were my speakers, the FIRST thing I'd do is to pull each mid/bass driver out and check it with a 9-volt battery with + to + and - to -; the cone should move OUT not IN, and of course if the driver does NOTHING you need a new driver.

Since you've got goofy labels on some of the drivers; I'm wondering if the + and - could have been screwed up, too--or--you just flat out have a toasted driver or two.

I'm thinking that Carver sometimes (often???) internally reversed (inverted) one channel so on heavy bass notes each amp channel pulled off of opposite sides of the power supply--then the output terminals on the backwards channel were labeled backwards; this kept overall polarity correct. I don't know what that means in terms of common ground--I'd expect an inexpensive amp to be common ground. Can you put a ~1 foot jumper wire between the two negative speaker outputs? I did that on my Aragon amp until I verified that it was in fact a common-ground unit.

danger boy

be careful when placing a jumper wire between the negative posts.. this could cause big problems.. more so than just lacking bass.

heiney9

danger boy wrote: »

be careful when placing a jumper wire between the negative posts.. this could cause big problems.. more so than just lacking bass.

Agreed!! Some non-common ground designs can NOT have the neg terminals connected because the amp goes POOF!!!.

I believe there is a continuity test that can used to determine if the amp is common ground or not. Don't remember the specific details but I'm sure someone does (F1, Ben, GV27, etc.) chime in. That's the best way to check if the manufacturer can't be reached or doesn't understand the question.

To Repeat, just don't arbitrarily connect the neg speaker terminals unless you know for sure it can be done w/o damage.

H9

woofiepaws

Maybe the PRs were defective to begin with. Try removing them and post some pics.

strider

heiney9 wrote: »

Agreed!! Some non-common ground designs can NOT have the neg terminals connected because the amp goes POOF!!!.

I believe there is a continuity test that can used to determine if the amp is common ground or not. Don't remember the specific details but I'm sure someone does (F1, Ben, GV27, etc.) chime in. That's the best way to check if the manufacturer can't be reached or doesn't understand the question.

H9

Yeah, I'd have to agree with the "don't tie the negative terminals together" line of thinking.

I know that my M-500 is non-common ground so I'm assuming the M-500t is non-common ground as well. That being said, I did use mine with the interconnect cable (non AI-1) without anything blowing up. Now that I have the AI-1 cable I haven't noticed any issues with that would lead me to believe it caused a problem.

Far as the test to determine non-comon ground or not, IIRC get an ohmmeter and put a probe on each negative terminal. "0" reading means they're connected (common ground), and infinite reading is non-common ground.

nms

Lasareath wrote: »

What's up with the PR?, it look warped, the bottom section from 3 o'clock to around 6:30

It's just the foam covering peeling off a little - mine have the same thing and it's only a cosmetic issue.