SDA 2B Upgrades/Amplifier Questions

Stew

I just found this forum while searching for Polk SDA. I've been a Polk fan since I bought a pair of mini-monitors in 1981. Bought my next pair of Polks (Monitor 7's) in 1988 and, after several upgrades, ended up with the SDA 2B's that I still own. I still love listening to my 2B's when I find time (4 kids) and I haven't found anything else that compares (except better SDA's).

I read several threads on upgrades including "SDA 2B Studio Crossover Upgrade" and I'm seriously thinking about the crossover upgrade and RD 0194-1 tweeters. As much as I love my 2B's, the highs sometimes sound a bit harsh and the bass could use a little more punch. Everything I've read here makes me think these upgrades will improve those issues.

My question is whether these upgrades, especially the crossover, will make a profound difference with a Yamaha AX-500U integrated amp (100w/ch with 170w/ch headroom @ 6 ohms). Plenty of volume for my taste and room size but I see a lot of people on this forum running much more expensive amps. A high end amp is not in the budget any time soon and I'm wondering if these upgrades will still make a big difference. If so, would a better amp make a big difference on top of the upgrades? Thanks in advance for the help.

Glad to find this forum. Good to know that SDA fans are still plentiful and that Polk still supports us!

Stewart

F1nut

Welcome to the fray.

IMO, the upgrades WILL make a difference that you will notice. Of course, a better amp will make things even better.

TroyD

What they grumpy guy said.

BDT

F1nut

Hey, I resemble that remark.

TroyD

In order:

Tweeters
Amp
Crossovers

That's how I'd attack it.

DDtTTS

BlueMDPicker

Hi Stew,

Welcome to the forum.

The tweeter upgrade will provide instantly noticable results. If you have a lot of hours in front of the speakers with the SL2000s, the first impression of the silk domes may be slight disappointment (for lack of a better term) until the new tweets break-in a bit and you become adjusted to the new sound as well.

Crossover upgrades for the 2Bs are relatively inexpensive and will provide you with a tighter, better defined bass (from my experience.)

If a new amp isn't in the cards at the moment, the upgrades to the speakers are still worthwhile IMO.

Enjoy!

Mike

ckpiv

Stew,

I have been running a pair of SDA IIB's since the late 80's until a couple of weeks ago when I finally upgraded to SRS 2.3's. In my experience with them, I too found the SL2000's rather harsh so I updated to the RD0194's. Wow - what an improvement! The high's are much more smooth and well defined. You should do this upgrade first. $48 a tweeter for club members will give you instant results.

As for the bass... I went from a Yamaha reciever to a Kyocera Integrated amp to a Parasound amp. with each step the bass improved. The SDA's like high current and will come alive the more you throw at them. You can pick up a nice amp at a reasonable price on ebay or on the flea market thread here. Also the placement of the SDA's are very important as well - I had mine 5.25" from the back wall which gave me a nice tight bass response. Any closer bass got muddy and farther out it would drop off so you need to experiment here. I also found the bass response was also effected by speaker cable selection so you may want to look here as well. The crossover upgrade would be my last resort IMO.

Good luck.

F1nut

ckpiv wrote:

The crossover upgrade would be my last resort IMO.

That's only because you haven't done it.

ckpiv

That is true. I was only giving my opinion in the steps I would take.

Stew

Thanks for all the advice. I think I'll go ahead with the tweeters and crossover upgrade. Crossover upgrade is fairly cheap and looks like a fun project. I looked up the parts at partsconnexion.com and current price is just over $50 to do both speakers. The 39 and 12 uF caps are available in either 400 or 630v and the 20 uF cap is only available in 400 v. Is there any advantage/disadvantage to the 400 vs. 630 v?

What about burn in for tweeters and crossover? Should this be done at normal/low/high volume? I've seen 50 hrs mentioned. Does it take that long?

If I decide to upgrade the amp down the road, what should I look for in a reasonably priced used amp? Mine is 100w/ch at 6 ohms with 2.1 db headroom. Volume is plenty in a 15 x 22 foot room but I gather sound quality and bass response would improve. Thanks for suggestions.

McLoki

Stew wrote:

Thanks for all the advice. I think I'll go ahead with the tweeters and crossover upgrade. Crossover upgrade is fairly cheap and looks like a fun project. I looked up the parts at partsconnexion.com and current price is just over $50 to do both speakers. The 39 and 12 uF caps are available in either 400 or 630v and the 20 uF cap is only available in 400 v. Is there any advantage/disadvantage to the 400 vs. 630 v?

Can you send me a link or PM showing what the crossover upgrade is and what it does for you? I also have a pair of SDA 1b's that I purchased new back in about 1987 and am thinking of putting back into service. I definately need the new tweets, but after about 18 years, I am sure the crossovers could use some going over as well.

Thanks,

Michael

Stew

Try searching the Vintage Speaker forum for "sda crossover upgrade". More parts/expense to do the 1b's compared to my 2b's. This is all new to me; others on this forum have first hand experience.

F1nut

I'm quessing you're going with the Solen caps, right? Just get them all the same, 400V. I prefer Sonicaps, but they are a lot more money. Don't forget to replace the resistor, get the Mills wire-wound 5 watt and replace the silver mica with a 750pF 500V.

Stew

Correct, planning on Solen caps. Do I need to replace the silver mica? The "SDA 2B Studio Crossover Upgrade" indicated that this is a high quality component and doesn't need replacing. By the way, www.solen.ca has some of the caps cheaper. Has anyone tried ordering through them?

F1nut

Solen caps are cheap enough already! Just get them from PE.

The silver mica caps that Polk used are crap, rated at 1000pF, tolerance of +/- 50%!!! Get the replacements, 750pF, 500V, tolerance of 5% or less.

Stew

F1nut wrote:

Solen caps are cheap enough already! Just get them from PE.

The silver mica caps that Polk used are crap, rated at 1000pF, tolerance of +/- 50%!!! Get the replacements, 750pF, 500V, tolerance of 5% or less.

OK, I'm going to ask what may be a dumb question. Why change a 1000 pF cap to a 750 pF?

SCompRacer

Stew wrote:

OK, I'm going to ask what may be a dumb question. Why change a 1000 pF cap to a 750 pF?

Have you got a schematic for your speakers? Polk will send you one if you ask for it. 750pf is the spec value.

SCompRacer

In reagrds to amps, folks will have their brand preference. I've got SRS 2's in a large open room with 14' ceilings. 200 - 250 WPC @ 8 Ohms (300-350 @ 4) did nicely for me. It will depend on what you can spend too.

Stew

SCompRacer wrote:

Have you got a schematic for your speakers? Polk will send you one if you ask for it. 750pf is the spec value.

Wow, Polk used a cap with a value somewhere between 500 and 1500 pF when the spec value is 750! Don't have a schematic but sounds like I need one. I'll add the 750 pF to the list. Thanks to you and F1nut for the info.

F1nut

Hey, I'm not going to steer you wrong.

Stew

Parts Connexion carries a 300v +/- 5% miconics silver mica (SMICA- 54432) for a whopping sum of $1.50 ea. Will this do the trick?

F1nut

The original was rated at 100V, so that'll be fine.

Stew

Just out of curiosity, what's the point of that 750 pF capacitor? 12 uF + 0.00075 uF is still essentially 12 uF. Does it serve some function other than very slightly increasing the capacitance?

Thanks again for all the advice. It's amazing to find this kind of interest and support for 15 year old speakers! It may be a while before I have time to do the upgrades but I'll post how it turned out when I'm done.

F1nut

It's a by-pass cap which operates at a different frequency.

Stew

F1nut wrote:

It's a by-pass cap which operates at a different frequency.

I did a quick search on bypass capacitors and found the following statement on Auricap's website (http://www.audience-av.com/auricap_application_notes.htm):

"Do not use bypass capacitors in the signal path. A single capacitor for DC blocking/AC coupling creates a simple path with one time constant. The signal quality will be compromised if a bypass or multiple bypass capacitors are added to a signal path capacitor. Bypass capacitors were used in the past to bypass low quality film capacitors or electrolytic capacitors. The bypass was the lesser of two evils. With the advent of better quality film capacitors the need for a bypass capacitor was eliminated. Bypass capacitors create multiple signal paths with multiple time constants. These time constants are very short but they can still be heard as a smear or overall loss of focus."

I don't fully understand this and wondered what some of you think.

F1nut

I believe they are talking about power supplies, not crossovers.

The following is taken from an article on the quality of different caps.

"ERO MKP1830 0,01mF MKP 100VDC – 1% tolerance – 5,5x7x7,5mm (a.k.a. Vishay Roederstein MKP1837)
Another part of the crossover of the “Progress” speaker (it’s that very small blue block on the bottom right of the photo).

Technical Specifications: Metallised polypropylene, radial capacitor, designed for LC/RC filter circuits, coupling and decoupling at high frequencies. Very low priced cap.

Sound: I was tipped by Klaus Witte of Germany to try this capacitor as a bypass cap for the Mundorf M-CAP SUPREME. I tried them as a bypass for the tweeter series caps in my Progress speaker and I must say I am very impressed! To get straight to the point they don't change a Supreme into a Supreme Silver-Oil but they really do clear things up. I must admit I was sceptical at first as the value is only 10nF (0,01uF) - and the caps in the Progress are 12,6uF. The difference is most noticeable with classical music but also good quality recordings of jazz and fusion benefit: No change in soundstage width or depth but there is more "concert hall acoustics" that let you get into the recording more. Not as liquid as silver/oil but they take away the "grainy" edge from the Supreme's. A gain in clarity and transparency making instruments better separable from each other, the violins in an orchestra are a group of individual violins instead of one mass. Jazz drum brushes sound more like a brush than a "shush".

Stew

F1nut wrote:

I believe they are talking about power supplies, not crossovers.

So that's what they mean by "signal path capacitor." See your point; if bypass caps help Mundorf M-CAP SUPREMEs, they should certainly help Solen Fast Caps. Thanks for the enlightenment and for putting up with all my questions! I'm looking forward to upgrading and hearing my "new" speakers.

schwarcw

I have been doing some research on the Forum on this topic since I have a pair of SDA-2s and have been consideing the crossover upgrades. I have upgraded the tweeters with the new silks and I found a nice improvement. I highly recommend doing this with your SDA-2Bs.

My crossover has a 750pF bypass around a 0.5 mF in the tweeter circut of the crossover. I talked with Ken Swauger via email about the by-pass. He mentioned that there is a school of thought that mixing the capacitor types may deter the performance.

I contacted both SonicCraft and Percy Audio. I gave them a schematic of my crossover and the parts I needed and asked for a recommendation. Both Jeff at SonicCraft and Michael Percy said that mixing the silver mica with the film capacitor should be avoided. Ken Swauger suggested that I use aligator clips to install the silver mica bypass and see how it affected the sound.

In Percy's catalog I was looking at the DynamiCaps and Wondercaps and these are metalized polypropylene and film. I was considering using these caps for the 0.5 mF and 750 pF portions on my crossover. The writeup on these caps states that "You may find by-passing is not required with these very transparent capacitors". It also states that "if by-passing DynamiCaps use no more that 1/100 the value of the main capacitor".

I was hoping for some feedback from the Forum. Has anyone used these caps? Do you thing the 0.5 mF and the 750 pF Wondercap is a good match?

F1nut

Carl,

The 0.5 is a uF, not mF.

You bring up an interesting question and one that I've been thinking about as well. But, alas I haven't had the time to investigate.

What other caps are you considering to mix with the Wondercaps?

Stew

Hmmmm ... What do you think of using a 750 pF metalized polypropylene cap instead of the silver mica to bypass a Solen in the 2B's? The Percy Audio catalog that schwarcw referred to shows a 750pF Wondercap for $5.95. Other than a few extra bucks, would there be any downside to using these or some other 750 pF metalized polypropylene caps?

F1nut

Only one way to know for sure, try it with both, then decide which one sounds better.