SDA SRS 2 Crossover Parts list

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.

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 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.

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 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.