SDA1 C UPGRADES

Billd123

Hello I'm a new member here.
I have had my SDA 1CS since 1988. I want to do the upgrades I have read about.
I will probably do them myself since I have a background in electronics.
I'm running 2 Adcom GFA 555s bridged with a GFA 565 Pre.
This has been the setup since 88
I my upgrade to a Mac tube Pre and keep the Adcom power amps.
I'm looking for any guidance tips you can give on purchase and build for the upgrades.
The V3 site info. is great, and I will probably purchase much of the components from them
after I'm clear on the approach.

First ? Do I need 1 or 2 circuit boards /speaker?

?2 Clarity Caps or Sonicaps?
I like the description of the Clarity Caps but see the boards are built for the Sonicaps.

?3 Inductor replacement. which to you recommend up grading?
I see I can reuse the origs.

I will eventually upgrade the interconnect trans also. So any advice on that subject will be helpful. In my reading it appears the trans my be hard to come by.

Thanks. I'm sure I'll have more ?.

Bill D

sfosselman

Having done all the upgrades on my 1C's I would contact westmassguy as he is a fountain of knowledge. From my experience I would start replacing the stock tweeters to Polks RDO-194-1. Contact Polk and tell them your a Polk Club member for a discount. I had Sonicap Gen I MP Caps for Hi and Lo-Pass and Mills MRA-12 Resistors installed. Loctite the drivers to avoid magnet shift ASAP, and Dynamat drivers and passive radiators. Also, replacing the weak binding posts and upgrading the interconnect to accept SpeakON Plugs is a must. There are many other mods to add but this is a good place to start.

michaeljhsda2

Add spikes. Welcome to CP.

DaveHo

You using the AI-1 interconnect? Just wondering how you are using bridged 555's to drive SDA's.

sfosselman

Good call DaveHo....I did't see that

westmassguy

DaveHo wrote: »

You using the AI-1 interconnect? Just wondering how you are using bridged 555's to drive SDA's.

It appears he's using the original AI-1 Transformer.

Billd123

Thanks all for the responses.
Yes, it is the original Interconnect w/ trans.
The loss of sound quality when using only one GFA 555 is huge.
I will probably do all the upgrades at once.
In considering doing the upgrades I was wondering are there replacements for
The drivers, other then the tweeters, in case of a failure?
Do most go with the Sonicaps? What about the inductors?
Making a list of upgrade components to purchase, so your knowledge on this
subject will be much appreciated.
I was considering starting from scratch after more the 25yrs with this rig, but
thought I would try reconditioning the components and upgrading the Preamp.
The sound quality is still great.

Thanks again
Bill D

george daniel

Sonicap and mills

F1nut

Trey (Vr3) is shutting down his business if he hasn't already.

Billd123

Thanks for the comments on the crossover components George.
Sorry to hear Vr3 may be going away.

Schurkey

Billd123 wrote: »

...with a GFA 565 Pre.

I used a GFP 565 for a few years. I liked it, but changed to an Aragon preamp/processor when the rig went multichannel/HT.

Billd123 wrote: »

First ? Do I need 1 or 2 circuit boards /speaker

You can re-use the OEM circuit boards, but buying one Gimpod circuit board per speaker makes the upgrade more thorough.

Some early 1Cs shipped with a pair of round circuit boards. Later 1Cs had the single, rectangular board. Either way, the Gimpod boards are a fine replacement.

Billd123 wrote: »

?2 Clarity Caps or Sonicaps?
I like the description of the Clarity Caps but see the boards are built for the Sonicaps.

ANY modern film caps are an upgrade to the ancient electrolytics and the single, prehistoric Mylar cap per speaker that are on the circuit boards now. I have Daytons on order for my speakers. I used them previously (along with some ERSEs) on my 1Bs with complete satisfaction. Others here are not so enthusiastic about the Daytons and ERSEs--but they suit me just fine.

Billd123 wrote: »

?3 Inductor replacement. which to you recommend up grading?
I see I can reuse the origs.

I can hardly wait to see the answer to this, as I'm contemplating the same thing on my SRS 2 pin/blade (1C in a larger cabinet with a larger passive radiator, and for reasons unknown, the same SDA inductor as the 1B--so I'll just transfer the ones from my 1Bs to the SRS 2) The FIRST inductor to upgrade will be the SDA inductor.

Billd123 wrote: »

I will eventually upgrade the interconnect trans also. So any advice on that subject will be helpful. In my reading it appears the trans my be hard to come by.

The special 1000 VA transformer has a minimum order and has been the subject of at least two "group buys" on this forum; but the 700 VA is readily available. Either one will be a considerable upgrade from the 0.13 VA OEM transformer.

F1nut

but the 700 VA is readily available

A slight correction so that no one gets confused down the road, it's an 800 VA.

westmassguy

I recommend pulling the passive radiator to see what crossover you have. Most 1Cs have the 4th generation single board, however I recently had to rebuild a transitional model that used 1B circuit boards. I used Tony's (AKA @gimpod) excellent replacement boards, and transferred all the salvageable components.

For Caps, the Daytons (Bennic) are entry level in my opinion. They're better than what you have now, but a better choice for a conservative upgrade would be Clarity PX Caps throughout. Sonicaps and Clarity ESAs are better, and affordable high-end Caps.

The existing inductors can be re-used. If you want to replace them, you'll need an accurate Digital Multi-Meter to read the DCR, and possibly an accurate LCR Meter for Inductance measurements and hand tuning. Jantzen makes excellent baked, air-core inductors. You can download the PDF here: http://www.jantzen-audio.com/air-cored-coil/ . When replacing the Inductors, I prefer to keep the Inductance and DCR values within 5% (1% for Inductance if possible) of the values listed on the schematics, or actual measured values. Rumor has it, the factory tolerance was 10%. It's also best practice to keep the values between the left and right crossovers within 1% of each other. There was a thread that had a list of Jantzen part numbers for most of the SDAs, but I can't seem to find it.

One of the best changes you can make, is replacing the large, high resistance 16mH Sub Bass Drive Inductors. Polk kept the resistance high, so amplifiers of the day could handle the speaker's impedance. Replacing them with lower resistance Inductors will improve the quality and quantity of deep bass. Solen makes custom, large gauge Air Core Inductors (expensive), or you can use the Erse SuperQ, Laminated Steel Core. Jantzen also makes the C-Coil Toroid Inductor, which has the lowest resistance. The big caveat, is the 1Cs will no longer be 6 ohm nominal, but closer to 4 ohm, and will drop well below that at certain frequencies. Your Bridged Adcoms may have difficulty driving a low impedance load. The manual I read only gave an 8 ohm rating for bridged mode. Best to check with Adcom.

The AI-1 Dreadnaught can be made using off the shelf components.
The 800 VA Toroid part# Y236906, can be ordered directly from Avel Lindberg.
Suitable stock enclosures are also available. You'll also need two Interconnects. Best practice, is to use the same type of cable you're using for the Amplifier to Speaker connections. You should also switch over to SpeakON connectors for the Interconnects, Dreadnaught, and at the binding Post Cups.

Your 1Cs use MW6511 woofers for the Stereo side, and MW6510s for the Dimensional side. Polk has new replacements for the 6511s, but they may supply 6503s in place of the 6510s. If you do order replacement drivers, be sure to tell them you're a Club Polk member for the discount, and free shipping in the US.

stogie

If you replace the existing board inductors with Jantzen inductors on the 1C's here's what you'll need. Can be sourced from Parts Express.

4 each of 000-1171 0.400mH 22awg
2 each of 000-1119 2.500mH 22awg
2 each of 000-0973 0.130mH 22awg*
2 each of 000-0974 1.250mH 22awg*

*0973 and 0974 are special order and take about 6 weeks to ship.

westmassguy

stogie wrote: »

If you replace the existing board inductors with Jantzen inductors on the 1C's here's what you'll need. Can be sourced from Parts Express.

4 each of 000-1171 0.400mH 22awg
2 each of 000-1119 2.500mH 22awg
2 each of 000-0973 0.130mH 22awg*
2 each of 000-0974 1.250mH 22awg*

*0973 and 0974 are special order and take about 6 weeks to ship.

They're all special order. Parts Express doesn't stock 22 gauge anymore.

Billd123

Once again thanks to all for your comments. Great information.
I'm going to try and get a chance to pull the passive radiator this week.
I will place an order for a pair of gimpod boards if all is in order.
I'm leaning towards reusing the inductors for now. especially as westmassguy
pointed out I may be lowering the impedance to danger levels If I stay with the bridged config.
By the way. I'm going to reconfigure for 1 555 in stereo and see if my recollection
of the performance was correct.
On the GFP 565. Yes it has been a great preamp. I'm going to see if I can upgrade to a GFP 750 when a good one comes up on Ebay.

I'll Let you know what I find when I open the SDAs up.

Bill D

westmassguy

Changing the large, 16mH spool Inductors will alter the overall impedance, not the smaller Inductors mounted to the circuit boards. The smaller Inductors will have a direct effect on the voicing of the speakers, while the 16mH Sub Bass Drive Inductors only affect frequencies below 150 Hz, and really kick-in around 50 Hz and below.

There are many upgrades that can be done to the cabinets, and other components, in addition to the crossover upgrades.

Replacing the Tweeters and upgrading the Crossovers will be the most noticeable improvements, the other upgrades are more or less cumulative.

RandyCroissant

I did most of the upgrades as mentioned, including the 16mh inductor upgrade as recommended by Dave. That inductor is really good bang for the buck so to speak as long as you have a good quality amp to drive them. Another thing that made a big difference to me was adding strips of sonic barrier behind the MWs. The effect was reduced bass but cleaner more detailed sounding mids. I also did the board level inductor upgrade with the Janzen air cores. I'm still on the fence on that upgrade, I mean they look great! very nice quality, but the stock ones sounded darn good as well.

Schurkey

What is the frequency-response difference between a 16mH SDA inductor as used in the 1C (and others) versus a 9.6mH inductor as used in the electrically-identical SRS 2 Pin/Blade?

Which inductor provides "better" or "deeper" bass??? First Guess: The larger inductor allows the SDA drivers to provide deeper "stereo" bass. Truthfully, I don't really understand the relationship of inductor size to low-pass frequency very well.

I have a guess as to why the SDA 1C and the extremely-similar SRS 2 P/B use different inductors...but I'd love to hear other's theories.

My guess is that the SRS 2 P/B was developed from the SRS 2 Blade/Blade, (which was a development of the SDA 1B) and the inductor carried over from 1B to SRS 2 B/B to SRS 2 P/B.. The SDA 1C was developed from the SRS 2 P/B, and some additional development time allowed the designers to revise the inductor value for better performance.

IF (big IF) this is true, the SRS 2 P/B could be updated with the larger inductor--the crossover is electrically near-identical to the 1C, the drivers are identical to the 1C, and the only real difference is the double binding posts along with larger cabinet and passive radiator on the SRS 2.

Malbec

stogie wrote: »

If you replace the existing board inductors with Jantzen inductors on the 1C's here's what you'll need. Can be sourced from Parts Express.

4 each of 000-1171 0.400mH 22awg
2 each of 000-1119 2.500mH 22awg
2 each of 000-0973 0.130mH 22awg*
2 each of 000-0974 1.250mH 22awg*

*0973 and 0974 are special order and take about 6 weeks to ship.

These do not quite match my numbers. I've had this project on the back burner for 2-3 years now.
I pulled the box of Jantzen inductors out of storage I bought from Trey and found the emails of our correspondence.

0.13mH inductor replaced with 0.15mH inductor, unwound to match
1.25mH inductor replaced with 1.40mH inductor, unwound to match
There are two inductors listed for the .4mH inductor, should be -1489 instead of -1171.
The 16mH has a match. -0873.

4 each 000-1489 0.40mH 22awg
2 each 000-1119 2.50mH 22awg
2 each 000-1129 0.15mH 22awg unwound to match 0.13mH 22awg inductor.
2 each 000-1461 1.40mH 22awg unwound to match 1.25mH 22awg inductor.
2 each 000-0873 16mH 18awg

I have a set of Tony's boards that I at least have soldered the caps and resistors on (Sonicap and Mills).
The boards are sweet.I highly recommend you grab these.

Jesse mentioned Trey closed shop. From my take, he's just too darn busy to build time consuming cross overs. Maybe not too busy to put in an order for you. A simple yes or no question might be worthwhile. That is if you're going to upgrade inductors.

Dave, in regards to the Jantzen part numbers, is this what you were referring to?

westmassguy

Schurkey wrote: »

What is the frequency-response difference between a 16mH SDA inductor as used in the 1C (and others) versus a 9.6mH inductor as used in the electrically-identical SRS 2 Pin/Blade?

Which inductor provides "better" or "deeper" bass??? First Guess: The larger inductor allows the SDA drivers to provide deeper "stereo" bass. Truthfully, I don't really understand the relationship of inductor size to low-pass frequency very well.

I have a guess as to why the SDA 1C and the extremely-similar SRS 2 P/B use different inductors...but I'd love to hear other's theories.

My guess is that the SRS 2 P/B was developed from the SRS 2 Blade/Blade, (which was a development of the SDA 1B) and the inductor carried over from 1B to SRS 2 B/B to SRS 2 P/B.. The SDA 1C was developed from the SRS 2 P/B, and some additional development time allowed the designers to revise the inductor value for better performance.

IF (big IF) this is true, the SRS 2 P/B could be updated with the larger inductor--the crossover is electrically near-identical to the 1C, the drivers are identical to the 1C, and the only real difference is the double binding posts along with larger cabinet and passive radiator on the SRS 2.

Different generations. The 1B and b/b SRS-2s are third generation. 1Cs and p/b SRS-2s are 4th generation. Both generations share the same crossover and driver compliment.
The 3rd generation used four MW6509 woofers, which have very high DCR values compared to the other 8 ohm nominal woofers used back then, and the stereo and dimensional woofers are wired in parallel.
4th and 5th generations used 4 and 8 ohm nominal woofers, and the dimensional side was completely re-designed.
The 4th generation SRS-2s have bigger cabinets and much larger Passive Radiators than the 1Cs, and most likely the sub bass crossover point and tuning had to be modified to compensate.

westmassguy

Malbec wrote: »

Dave, in regards to the Jantzen part numbers, is this what you were referring to?

Yes, Don had already sent me a copy. For some reason, it wouldn't show up in my browser.

RandyCroissant

That is the same list I used to order my inductors for my 2bs. If you decide to buy them you will be impressed with the quality.

Schurkey

westmassguy wrote: »

Different generations. The 1B and b/b SRS-2s are third generation. 1Cs and p/b SRS-2s are 4th generation. Both generations share the same crossover and driver compliment.
The 3rd generation used four MW6509 woofers, which have very high DCR values compared to the other 8 ohm nominal woofers used back then, and the stereo and dimensional woofers are wired in parallel.
4th and 5th generations used 4 and 8 ohm nominal woofers, and the dimensional side was completely re-designed.
The 4th generation SRS-2s have bigger cabinets and much larger Passive Radiators than the 1Cs, and most likely the sub bass crossover point and tuning had to be modified to compensate.

One would think that if the inductor size was the result of tuning for cabinet/passive radiator sizing, the 1B and SRS 2 B/b would have had different-sized SDA inductors, just like the later 1C and SRS 2 p/b.

westmassguy

Anything is possible. Unfortunately, that information is not available to us. Locked in a vault in Baltimore, and covered by patents and non disclosure agreements.

stogie

[quote="Malbec;2188735There are two inductors listed for the .4mH inductor, should be -1489 instead of -1171.[/quote]

My bad. Yes that is the better replacement coil. The 1489 has a resistance of .640 and the 1171 has a resistance of .598. The above chart states that the stock DCR should be .687, so the 1489 is closer to that value.

gimpod

stogie wrote: »

If you replace the existing board inductors with Jantzen inductors on the 1C's here's what you'll need. Can be sourced from Parts Express.

4 each of 000-1489 0.400mH 22awg DCR 0.640 Ohms
2 each of 000-1119 2.500mH 22awg DCR 1.840 Ohms to low stock is 1.953 Oms
2 each of 000-0973 0.130mH 22awg DCR = ?/ should be 0.370 Ohms*
2 each of 000-0974 1.250mH 22awg DCR = ?/ should be 1.329 Ohms*

*0973 and 0974 are special order and take about 6 weeks to ship.

Unfortunately the SDA 1C's and Pin/Blade SRS SDA 2's are not really a candidate as no one makes them with the proper Gauge, DCR and Mh. The only inductor that would be acceptable in my book would be the "000-1489 0.400mH 22awg DCR = 0.640 Ohms" Just reuse the old ones (they don't wear out) unless you have a lot of money and time to experiment as unwinding inductors and can get real expensive real fast if you don't know what your doing.

Here's the link to the chart for the inductors, go to lat post Inductor DCR Insanity for SDAs

The difference between the 4th gen 9.6mH inductor in the SRS SDA 2 and the 16mH inductor in the SDA 1C has to do with tuning the SW-150 PR to the bigger cabinet.

westmassguy

You can also pad them with a resistor. It's acceptable for the Hi-Pass Shunts. It's definitely not recommended for Inductors in Series with the Woofer or Mid in a 2nd order crossover. You'd have to be creative placing the resistor in the circuit though.

boston1450

To think. Other forums say people on CP dont know nothing.

Billd123

I had a chance to pull the radiator. I will attach photos.
They where built 12/87.
I don't know who would say this site has nothing to offer.
The level of detailed info. and the fact everyone wants to help is great!!
I'm going to order 2 boards tomorrow. I noticed Mills does not offer a 12w 2.7 ohm res.
Order the 3ohm?
I think I will stay with the orig. inductors. Thanks for the input on the replacements.
I have too many project to finish. No need to complicate things at this point.
You will see in the pictures that the dampening material is all scrunched up
behind the stereo and dimensional arrays With nothing behind P.R..
Is that unusual?

Bill D

boston1450

No. Thats suppose to be that way.