SDA SRS 2 Crossover Parts list

Tony M

I just read this thread through and since I need some more 194's for a few sets of Polk classics, why not do the 198 TL w/cap upgrade in the future on my SRS2s. Thanks alot for doing the research and all who put their advice into this also.

Now this is for the 4 ohm version(I'm thinking it was) or no?
Nevermind, I just read the answer in a newer thread tonight all about the 475.00 pr.

What a deal. The blade blade is.....TL able.

inspiredsports

tony millard wrote: »

I just read this thread through and since I need some more 194's for a few sets of Polk classics, why not do the 198 TL w/cap upgrade in the future on my SRS2s. Thanks alot for doing the research and all who put their advice into this also.

Now this is for the 4 ohm version(I'm thinking it was) or no?
Nevermind, I just read the answer in a newer thread tonight all about the 475.00 pr.

What a deal. The blade blade is.....TL able.

The only real downside to the 4 ohm blade/blade design is that it uses some very big caps in the low pass circuit that cost a bit more.

helipilotdoug

OK, I guess I'm kind of confused here. So what else is new! I'm not a electronics person, and hardly know the difference between a resistor and a capacitor! Trying to figure out what needs to be done to get this upgrade done. Ben told me the blade/blade SRS 2's can not be tl'd. All I want is to get similar improvements to the SRS's as I did with the 2B's when I upgraded them. What do I need to do, and who can do this for me. Somebody please help.

Schurkey

helipilotdoug wrote: »

Trying to figure out what needs to be done to get this upgrade done. Ben told me the blade/blade SRS 2's can not be tl'd.

Old information. When replacing the capacitors, instead of installing a 4.4uf capacitor in the high-frequency section, install a 5.8uf capacitor. Then buy and install 4 RDO-198 tweeters in place of the 2000/194 units. Done.

I'm thinking the jury is still out in terms of TL-ing the PIN-blade SRS2 along with the companion SDA-1C.

helipilotdoug wrote: »

All I want is to get similar improvements to the SRS's as I did with the 2B's when I upgraded them. What do I need to do, and who can do this for me. Somebody please help.

This thread, and others here at Club Polk have all the details.


Short story:
Lift the fiber fill packing back into place if gravity has pulled it too far downward over time.
Fresh capacitors of the same effective values as is already installed EXCEPT the one-per-speaker 5.8uf instead of the 4.4 described above; AND you can simply eliminate the 750pF unit.
Fresh resistors of the same values as is already on the board.
Eliminate the polyswitches (some folks recommend adding additional resistance equal to the resistance offered by the polyswitch. I chose to NOT add resistance to make up for the polyswitches; and I feel the HF is STILL not loud enough on my 1Bs; your mileage may vary.
Replace the SL2000 tweeters with RDO-198
Damping material on the mid-woofers and passive radiators
Assure the drivers are mounted "air tight" to the cabinets by applying rope caulk (and perhaps using the stainless steel mounting rings supplied by another member here)

Put it all back together while assuring that you connect the wires to the correct places. The new tweeters will require a minor modification to the wire harness to connect one of the blades on each tweeter.

You can do this all yourself. I did, and I'm no rocket scientist. Nice weekend project.

helipilotdoug

OK, I've pulled the trigger on this upgrade on the SRS 2 to SRS 2.1tl's. Ben is ordering all the necessary upgrade parts while Sonicraft has the sale on, and I'll be sending him crossovers tomorrow from 1b's for the upgrade. That way I'll still be able to listen to the SRS 2's while they are being rebuilt. Inspiredsports, thanks for all your outstanding, well documented progress on this. Without your experimentation and documentation of it, I'd not be doing it.

inspiredsports

I wanted to revisit this thread and post an important update.

It took me a long time to get this done, but I purchased pairs of Mill resistors in 1/2 ohm increments from 3.5 down to .5 as I was never entirely pleased with the volume of treble coming out of my modified SDA STS 2's. The TONE was always fine, but the relative OUTPUT from the top end of the crossover seemed several db's too laid back.

It always perplexed me that the initial resistor from the black speaker wire terminal was a 3.5 ohm. NOTE the identically set up (but smaller cabinet and 12" passive) 1986 SDA-1B has a 2.0 ohm resistor in the first spot. That was always counter intuitive to me as it seemed the smaller cabinet would put out LESS bass and require proportionatley less treble.

When completed, I always seemed to want another 5 or 6 db of treble, as borne out when I had my NAD 1700 pre hooked up with parametric tone controls that allowed me to boost 12K and up by a max of 6db. Perfect!

At any rate, I finally got around to removing the 3.5 ohm resistor and soldering in 2 pins in the sockets. It was then easy to remove the passive radiator and quickly clip different value resistors between these 2 pins, button the cabinet back up and take measurments and listen.

Those who followed my re-entry to this hobby back in 2008 might recall I loved (still do) my TL'd 2B's and wanted that same sound quality from the much larger and more authoritative SDA SRS 2 cabinets.

I've tried .5, 1.0, 1.5, 2.0, 2.5, 2.7 and 3.5 ohm resistors. My measurements show about a 1.4db treble boost per .5 ohm decrease.

The .5 ohm and 1.0 ohm test sounded a little too bright. The 2.5's and 3.0's still a bit too laid back.

The 1.5 and 2.0 ohm tests sounded just right, at approximately 6 and 7 db gains respectively.

At any rate, the 1.5's are in place right now as I listen to my new MoFi Cars Candy-O Gold CD. I'm 50/50 1.5 versus 2.0 right now, so I guess I'm going to order a pair of 1.8's from Sonic Craft and audition before I declare this mod complete.

To those who have performed this mod with a 3.5 resistor as originally specified (or a 4.0 if your removed the polyswitch), please stay tuned.

Greg

Schurkey

I've always believed that my 1Bs were shy on treble. When I removed the SL2000 from the upper positions and installed a pair of 198s and re-capped the crossover, I deleted the polyswitches and did not add a compensating resistor. Added a small aftermarket "ribbon" (actually planar) tweeter crossed in at 10 or 11K. It never occurred to me to lower the value of the resistor from the stock 2 ohm value. May be my ears, may be my room, or may be my taste...but I'm happy now. SOMEDAY, maybe, I'll get the second pair of 198s for the lower positions. I suppose I should follow your lead (again) and change resistors while disabling the ribbons.

Not surprised you wanted more treble output, especially since you should have additional bass/midrange compared to my smaller 1Bs.

inspiredsports

Schurkey wrote: »

I've always believed that my 1Bs were shy on treble.

Not surprised you wanted more treble output, especially since you should have additional bass/midrange compared to my smaller 1Bs.

That wasn't exactly my point. I was making the assumption the stock 1B was probably properly voiced with a 2.0 ohm resistor.

What didn't make sense to me was the SDA SRS 2 should have theoretically had a similar or LOWER value resistor to BOOST its treble because theoretically the larger cabinet and 15" versus 12" passives would put out more bass per unit of input power.

I know it's not that simple when all of the elements in the circuit are considered, but in my opinion the 3.5 ohm resistor really attenuated the amount of treble reaching ears.

Schurkey

inspiredsports wrote: »

I was making the assumption the stock 1B was probably properly voiced with a 2.0 ohm resistor.

In my opinion...in my room...yada yada...the 1Bs (at least MY 1Bs) are NOT voiced properly. But of course you've figured that out from my prior post.

inspiredsports wrote: »

What didn't make sense to me was the SDA SRS 2 should have theoretically had a similar or LOWER value resistor to BOOST its treble because theoretically the larger cabinet and 15" versus 12" passives would put out more bass per unit of input power.

Yes, I understood. Perhaps I didn't express it well.

I wonder how using the 1.5 ohm resistor (compared to the 2-ohm units in the 1B) compares to my adding a "supertweeter". Your solution is clearly more elegant.

inspiredsports

We are clearly playing in uncharted (and unapproved mod) territory here, but the first resistor connected to the black speaker wire connection controls how much energy makes it to the tweeters.

Less resistance (a lower ohm value) allows more energy (volume) to reach the tweeter(s).

In my situation, after adding the 5.8 uf cap and switching the SL2000/RDO194 tweeters to RDO198's, the treble was clearly on the lean side so I systematically set out to conquer the problem and have finally figured it out.

helipilotdoug

I have done the upgrade now to SRS 2.1tl, and am so happy with what I'm hearing. When Ben rebuilt my crossovers, he put 2.7 ohm resistors where the 3.5's were, and so far the balance seems perfect. I'm at close to 100 hours now, and everything seems wonderful. A Big THANK YOU for your exploration and this thread. Without your hard work and documentation, I'd never have done this.
Doug

inspiredsports

helipilotdoug wrote: »

I have done the upgrade now to SRS 2.1tl, and am so happy with what I'm hearing. When Ben rebuilt my crossovers, he put 2.7 ohm resistors where the 3.5's were, and so far the balance seems perfect. I'm at close to 100 hours now, and everything seems wonderful. A Big THANK YOU for your exploration and this thread. Without your hard work and documentation, I'd never have done this.
Doug

I was going to hold off posting until all of my testing is done but didn't want to not respond.

I've been subbing in resistors, letting them burn in a bit and then taking FR measurements. I'm on the 2.5 ohm Mills right now with 2.7 and 3.0 still in the queue. I'll post graphs when I'm all done, but the bottom line is, based upon my measurements of the 2.5's, I think 2.7's will prove to yield the absolute flattest response curve. I think you've got it just right.

inspiredsports

Reviving this thread as I finally got Larry's Rings and new foam gaskets installed today.

While inside I removed the 2.5 Mills 12 watt that was in place when I got sidetracked from my Polk adventures.

I've been listening to a 2.0 Mills 12 watt for a few hours and it seems to be the closest match to the sound of my TL'd 2B's so far. I have 2.0 Mundorfs on-deck for next Saturday.

Schurkey

1. Good to hear from you again.

2. Pleased to see you're still interested in optimizing the speakers. I sure like my 1Bs. and tagging-along with your efforts has been very rewarding. Thank you.

3. I'm surprised you stopped at 2-ohm resistors. I had a hunch you'd go for 1.8- or 1.5-ohm units. I get that my ears are tired, but from Day One in '86 or '87 when I bought them, I though the treble was weak.

VSAT88

This is awesome.