SDA SRS v1 - should they really sound this bad???

kattz

Hello all,

New here.

I got these SRS SDA speakers from a "vintage audio dealer", claims that they were recapped, I need to pull the crossovers and verify that they didn't jack things around. He also claimed that they replaced "at least one SDA driver in each cabinet with a comparable one from Parts Express".

I am running these in mono-block config now, no SDA cable connected. But when my G-9000DB receiver was running these and using the SDA cable, no difference could be heard.

Sorry to F1Nut, he's already heard me ranting...

These speakers sound truly heinous. Light low end, crackling highs, weak mids. Sounds like someone tossed a bag of marbles in there.

The boxes are sealed. Tapping on a mid causes the passive radiator to flex in time with the finger tapping...

I plan on pulling the crossovers. Is there a step up? The SDA upgrade link page takes me to an Indian hacker website...

Cheers!

Kev

audioluvr

Post pics. Are you using the stock SL-2000's? Check to see if the edges have separated and use a paper towel roll (at low volume) to listen to each tweeter/ driver individually. Then pull the passive radiator and post pics of the crossovers so we can get a peek.

pitdogg2

There are no "comparable drivers" from parts express. using one is a bone headed move. I betting more than one magnet has moved enough to contact the voice coil. Do all drivers move freely with no scratching? If they do not move freely do not force it. You also cannot tap on a driver to check for air leaks.

Yes pictures of the crossover would be very helpful

kattz

I'll do it tonight. Tweeters are SL2000's. Need to go to something else.
Because I want to use the SDA circuit, thinking of biamping the speakers to low/mid on one amp and highs on other amp. In this configuration, each amp is common ground, which the tweeters don't care about. Amps have level control. This means 170 watts of power per channel per amp. Monoblocks put out 340 watts per channel. I don't think they can be bridged. Output levels are adjustable.

Full disclosure, the preamp and amps need a complete refurb. This might be part of the issue but these amps still have a pretty clean output.

Here is a pic of the units when I purchased them. Thanks!

kattz

pitdogg2 wrote: »

There are no "comparable drivers" from parts express. using one is a bone headed move. I betting more than one magnet has moved enough to contact the voice coil. Do all drivers move freely with no scratching? If they do not move freely do not force it. You also cannot tap on a driver to check for air leaks.

I agree about Parts Express.

Regarding the air leak check, it works... tap on one of the midwoofers and you can see the passive radiator move. I originally thought the cabinets were leaking air, hence the crappy bass response.

I will check the drivers for scratching noises as well. Thanks for the insight!

Kev

F1nut

That is not how to test for air leaks, this is.

Push the PR in and while holding it in watch the mid-drivers. They should pop out and slowly recede taking 3 to 5 seconds to rest.

I guarantee that your loose end caps are leaking air.

You need to completely go over the speakers/crossovers before thinking about how to drive them.

kattz

OK, so. Every driver is Polk. No Parts Warehouse. Confirmed.
One PR is dented, but only on the face. I think maybe melted by a soldering iron?
I pushed in each of the drivers. If pushed in with a finger on each side of the cone, no noise.
Pulled the PR on the left channel. What's with all of the hotmelt glue on the binding post cup?
F1nut, in answer to your PM, looking from the rear of the cabinet, the red binding post is on the right.
These are the infamous 2000-series tweeters. One has been changed
And on to the crossovers - yep, it's different! Pics attached.

Kev

pitdogg2

Dayton and Solen😖😖😖.
If you're going to do a recap why not change the old resistors out for better as well? I mean you're there and they're inexpensive.

It's important to have a very well sealed cabinet so Polk sealed the binding post cup to prevent leaks around the binding post.
A leaky cabinet will affect bass response(less) and can also allow excessive driver excursion.

kattz

The i***t who recapped them also burned some of the pads off of the crossover board.

The reference to Parts Express was the recap. The seller obviously didn't know anything about what he was selling. And I didn't know what I was trading a perfectly good Sansui 9090DB for either.

I feel stupid.

nooshinjohn

One thing a quick read of your thread did catch my eye... are you running one amp each to the speakers? The BA3000 is a beast of an amp, but your SDA version is not capable of being driven by monoblocks. They need to see a common ground amplifier, which means a rather robust stereo amp.

kattz

If anyone would like to volunteer information, I'm having two new crossover boards printed. I can design the boards based on the original schematic, but what's the right parts to use today? PM would be appreciated.

pitdogg2

kattz Posts: 5
6:22PM
The i***t who recapped them also burned some of the pads off of the crossover board.

Well then I've have to say that could be responsible for the problems you're experiencing.

kattz

nooshinjohn wrote: »

One thing a quick read of your thread did catch my eye... are you running one amp each to the speakers? The BA3000 is a beast of an amp, but your SDA version is not capable of being driven by monoblocks. They need to see a common ground amplifier, which means a rather robust stereo amp.

I was, without SDA. Not now. And with or without SDA, they are clipping something fierce.

Once I get this mess straightened out (and at this point I might just put them on Craigslist, I'm so angry), I will probably drive them bi-amped.

kattz

pitdogg2 wrote: »

kattz Posts: 5
6:22PM
The i***t who recapped them also burned some of the pads off of the crossover board.

Well then I've have to say that could be responsible for the problems you're experiencing.

You should see this board up close. Components missing, and what's there doesn't seem close.

F1nut

Dayton/Bennic and Solen are likely the two worst choices for replacement caps.

kattz

I would not have chosen them.

kattz

I gotta ask a really stupid question: What keeps me from putting 1.2TL crossovers in these? I know that the drivers are different. Difference? Magic smoke runs out? "Not only no but..." I already have to scrap the crossover boards.

audioluvr

I can't see the damage to the pcb but you could careful scrape off the coating on the trace and extend a lead to it or use a short piece of speaker wire as a jumper. Also if you redo the crossovers don't put a cap right next to a resistor. They are sensitive to heat and the resistor makes heat.

kattz

I was looking at the caps. What is the recommended voltage on replacement caps?

pitdogg2

kattz wrote: »

I was looking at the caps. What is the recommended voltage on replacement caps?

200v is what most will use. Some brands only come in higher voltages.
100v IIRC is stock voltage

1.2 cabinets are different wood and made differently.
Too costly to change IMHO

F1nut

kattz wrote: »

I gotta ask a really stupid question: What keeps me from putting 1.2TL crossovers in these? I know that the drivers are different. Difference? Magic smoke runs out? "Not only no but..." I already have to scrap the crossover boards.

In addition to what Ivan said about the cabinets....the only things the 2 models have in common are 4 mid-drivers and the PR. Even the position of the binding posts are different. Fix what you have.

Hansvelton

These speakers sound truly heinous. Light low end, crackling highs, weak mids. Sounds like someone tossed a bag of marbles in there.


Qualities, this bad, can only come from something really damaged or leads or component failures on the crossover board.

My bet, you will need to check each driver, and every trace on the crossover board.

Dayton and Solen caps "alone" may alter the sound of the treble some for sure, but not make it crackle and all the stuff you mentioned.

I also see quite a bit of Rust on some of the SL2000 screws. Not a good thing, as it means they may have been subject to high humidity or dampness for some time.

These should sound quite good, not like a bag of marbles...lol

Good luck, a huge project ahead. Wish I could help you, it is easy work, but just tedious and very time consuming.

invalid

It would probably be easier to start over, and build new crossovers with new PCB's or point to point wiring.

kattz

invalid wrote: »

It would probably be easier to start over, and build new crossovers with new PCB's or point to point wiring.

That's the plan...
I notice that many are installing 400V and 600V caps in their systems. However, Humble Homemade Hifi did an extensive study of cap makers and their various offerings. Almost every cap that received the highest review are 100V caps. Perhaps using higher voltage caps is not the best idea? Would be interested in other's thoughts on this.
Also wanted to add that, using Ohm's Law, using my BA-3000 amps in monoblock (yes, I know it won't work, speaking as an example only), the BA-3000 amp outputs a maximum of 340W into 8Ω.
That equals a maximum forward voltage of 52.1536192V. Formula = voltage V in volts (V) is equal to the square root of the power P in watts (W) times the resistance R in ohms (Ω). Even at 1000W, I can't push the voltage more than 64-65V using either 4Ω or 8Ω.
So why the huge caps? Not saying anyone is wrong, but the math just doesn't work IMO. Maybe I'm missing something?

pitdogg2

kattz wrote: »

invalid wrote: »

It would probably be easier to start over, and build new crossovers with new PCB's or point to point wiring.

That's the plan...

I notice that many are installing 400V and 600V caps in their systems. However, Humble Homemade Hifi did an extensive study of cap makers and their various offerings. Almost every cap that received the highest review are 100V caps. Perhaps using higher voltage caps is not the best idea? Would be interested in other's thoughts on this.

Higher voltage caps are HUUUUGE and a pain to fit sometimes. If you can most aftermarket caps we use are 200v and more than enough voltage room. Clarity and Sonicaps are two of the most tried and true used. The one thing about Sonicaps is they have the exact values needed for Polk speakers.

Some of us here are very familiar with the Humble HiFi page. Lots of good info.

kattz

Also, there should be nine caps on the board according to the schematic. I only have six. There are some jumpers installed and some open holes.

F1nut

You can eliminate the two 750pF bypass caps when upgrading to film caps as was done, so there should be 7 caps total. Most eliminate the polyswitch and replace with either a jumper or better yet a .5 ohm resistor to make up the resistance value of the polyswitch.

F1nut

Looking at your pics, I believe you are missing one 130uF cap.

kattz

The polyswitch is gone.

Hansvelton

F1nut wrote: »

Looking at your pics, I believe you are missing one 130uF cap.

Just going from memory, but is that the 130uf cap that allows bass to the dimensional array under 150Hz or so?

F1nut

The two 130uF caps are in parallel.