Documenting: My SDA-1c upgrades from start to finish

nooshinjohn · February 2023

I, on behalf of the entire Polk Forum, want to personally thank plastic_avatar on the fine work and dedication he has put into this endeavor of his to restore his Polk SDA 1c's, and sharing in great detail those efforts with the rest of the forum. No doubt his journey has been long and filled with potholes along the way, but the path he has taken should serve as an inspiration of what NOT to do when restoring and upgrading vintage Polk speakers.

May this thread live on forever as a means to enlighten those that follow in the art of what a disaster overthinking a simple weekend project can become.

Gardenstater · February 2023

Is it true that you didn't even install Dynamat on the baskets of your 1.2tl's?

nooshinjohn · February 2023

Gardenstater wrote: »

Is it true that you didn't even install Dynamat on the baskets of your 1.2tl's?

Had the material, never had the time...

xschop · February 2023

nooshinjohn wrote: »

Gardenstater wrote: »

Is it true that you didn't even install Dynamat on the baskets of your 1.2tl's?

Had the material, never had the time...

So 1nut has you 1-up on mods lol.

plastic_avatar · February 2023

nooshinjohn wrote: »

Had the material, never had the time...

I think we can all agree that sometimes simple weekend projects might take longer than expected to finish.

Gardenstater · February 2023

nooshinjohn wrote: »

Gardenstater wrote: »

Is it true that you didn't even install Dynamat on the baskets of your 1.2tl's?

Had the material, never had the time...

Well those were big speakers. If a 1C can have every mod worthwhile done on it in a weekend, how long would it take with those?

You only had between Jan 2013 and Nov 2021 so I can see your point

DarqueKnight · February 2023

Jstas wrote: »

At what point do "mods" to a speaker become so extensive and numerous that the speakers is so far from original design and intent that it can't be considered a modification of the original and is now something entirely different?

The thing to realize and understand is that most commercial products that are priced so people can afford them are already far from original design and intent simply due to cost considerations and parts availability. The original design is the ideal. The manufactured realization is often watered down with cost cutting and parts availability compromises.

The first mods I did to my SDA 1Bs in 1990 were done under the guidance and advice of Polk's engineering department. I was told where Polk made (numerous) design compromises to cut costs and I was advised on what to do to mitigate those design compromises. I was further offered suggestions on premium crossover parts selections that were too costly or simply unavailable in manufacturing lot quantities at that time. In that regard, the (numerous) mods I have done to my SDAs have brought them much closer to Polk's original design intent and performance goals.

My crossover modifications used the original schematics. I just substituted higher quality parts made with better materials and better manufacturing techniques. My cabinet and driver basket modifications just added more vibration damping.

My modded SDAs are not entirely different. They are entirely better and higher performing with more clarity, more detail, more image stability, and more stereophonic performance.

I liken the difference to a bodybuilder who uses improved nutrition and exercise to increase health, strength, muscle definition, and muscle mass to transform their body into a healthier, improved version of itself. This contrasts with bodybuilders who abuse steroids to the point that they look remotely human and have a host of heart, circulatory, joint, and mental problems.

audioluvr · February 2023

As long as the OP is happy with his work and the final auditory results are pleasing to him I'm happy for him. And you have to admit he takes a punch really well! Unlike a lot of members both past and present.

skipshot12 · February 2023

pitdogg2 wrote: »

skipshot12 wrote: »

^ Could be said for any mod I reckon…
Once we do our first mod we’ve taken away from the original.
Comes down to individual tastes & perceptions at that point.

Incorrect.

Most if not all Speaker companies do not put excellent crossover components in their crossovers due to cost over thousands or 10's of thousands of units. You should take a look at some Legacy audio crossovers, for a speaker costing tens of thousands of dollars they too have some pretty generic XO components on board. When you're looking at saving 40-50+ dollars per XO that translates to tens if not hundreds of thousands of dollars in the end. If you tighten up the tolerences of caps and resistors from 10-15% to 3-5% and some are 1% tolerence you can definitely make a dramatic difference without changing the intent of said speaker. In the beginning it was Matt Polk himself who told us the best thing we could do was better tighter tolerence caps,resistors and inductors would give us a better presentation of his speakers. He basically said he had to make consessions to be able to bring his stuff to market and still be affordable to the masses.

I agree with this mostly.

While using tighter tolerances on caps and such one's not changing the sound of the speaker, provided the same type components and manufacturers are used. If the original crossover was voiced with a Panasonic electrolytic cap @ 10% tolerance going to a 5% or lower tolerance changes zip.
But go to a Mundorf, or any manufacturer of your choice, film cap we now have a change.

Take the same speaker and change components of differing construction (uprades) I would think the original designer would want to voice said speaker, with these higher grade parts, to align with the original sound he had in mind.

Once we start with film caps and different resistor designs we're changing the sound of the speaker.
And... we are changing the sound to our likes as to what we want more of and what we want less of based on preferences.
Good example of this is some folks prefer the sound of the speaker with Solen & Mills. Some prefer Clarity & your choice here, etc......

Understand the cost point to be able to sell a speaker at a given price.

I agree to disagree..... 😬

plastic_avatar · February 2023

Trying out Vr3's felt/wool pads.

Not sure yet of differences yet. Just some quick listens to things. There might be a little more focus on some of the higher-frequency sounds in Hotel California, especially in the soundstage outside the boundaries of the physical speakers. Will listen more critically tomorrow.

Gain

Before I velcro'd those on, I had to bump my gain up one notch on the right to center the image better. I have very different walls on the left and right. I thought things were slanted to the left a little. My youngest verified. The SDA reached further off to the left than the right, and voices that should be centered were between the left speaker and center.

Ohms for the poor

I've got my meter out. Going to see how these things read later.

skipshot12 · February 2023

^ Interesting.
I'm listening.....

xschop · February 2023

Those look like factory parts. Nice addition, and look forward to your impressions. I believe this will take out any phase plug interaction/diffraction with the tweets.

plastic_avatar · February 2023

My reversed 1C crossover holder

Hey nerds.

Not feeling hot, so not a lot of listening to compare felt/no felt. I'll get to it.

I had to sit in front of the computer just now, so I re-did the screw locations. I'll swap my old ones out when I get around to those new inductors this year. These will be a lot easier to manage, since you mount the board outside of the speaker and then mount the holder. Duh

If anyone wants a copy of the 3D file for it, the link is below. I'll put up the Wuhan plates and other stuff soon.

https://drive.google.com/file/d/1S11wet57oIYxj3XyZBPG5rIa6b1onHJl/view?usp=sharing

plastic_avatar · February 2023

Music on tap

My fun money this past 2 weeks went to buy the new Tove Lo and ye olde Herbie Hancock Headhunters CDs.

Tove is for fun. I also want to support artists who make an impact on how I feel (her song Grapefruit is meaningful to me).

Herbie is to see if I can establish my own baselines for placement, room, and tweaks. I honestly don't get jazz. I'm not a musician. I don't have math brain. A childhood friend, Jamal Milner (a stellar blues, jazz, and whatever-the-heck-you-throw-at-him professional guitarist), suggested some easy jazz for me to cut my teeth on years ago. I never graduated to be comfortable with the kind of jazz that makes me think life has no meaning and all is chaos...

I'm using Herbie as a ref because of DK's excellent write-up on his experience with the album in his space with his Olympian setup via https://forum.polkaudio.com/discussion/197520/crs-1989-driver-phase-plug-and-aluminum-tweeter-plate-modifications#latest (his write-up is towards the bottom of that page).

I don't expect that^ from my untreated, unfinished room and thrifty setup, but it gives me a reference for how good the song Chameleon can sound on an uber system. AND it lays out where and how the elements are placed in the sound field. It's a great reference write-up, and very useful, imo. I wish there was a catalog of entries that detailed in the SDA music thread. Different models, different songs, detailed write-ups to reference for other users.

Anyhow!

Odds and ends

Grease.

The soundtrack.

My youngest loves the movie. Like, L-O-V-E-S it. So, we've listened to the CD a couple of times this week. So clear, so fun, so... one-dimensional compared to say, American Breakfast. That's a totally stupid comparison, but going from that to Grease was odd to my ears. Once I acclimated, it was wonderful, clear, balanced, and fun. And it was, well, yes, wonderful. Loud, it didn't hurt like, say, my grating Rti10. There wasn't any fatigue. It was just a good time that made us feel good

But,

Adjusting between a great mix and a bad one is more jarring than on the M12. Even an average mix on 1 element is rough.

Listening to Walking in Your Footsteps (The Police) is pleasant and airy, but Sting's voice is back too far in the plane between speakers.

Switching to Numb (Portishead) is like someone turned on the stage lights. The lead's voice is easily a foot or 2 in front of the center of the speaker plane. I was really surprised. I put that on for my wife. It sounded amazing.

I think my ideal setup might be to build some insane lazy-Susan platter where I can rotate the 1C out and swing in the M12 (w/ better caps, because I'm now fairly certain the Daytons did no favors to the upper midrange). Best of both worlds, for me.

C'mon lottery...

Ohms

Speakers read between 4.1 and 3.9 via the meter at the terminals, in case anyone cares to know.

Would the phase plugs lower overall impedance, potentially?

Have any of you other 1C guys measured the ohms at the terminals? If so, what is your reading?

Room treatment

Best I can do this Spring is look for $20 5x8 rugs at Aldi to put on my front and right walls.

The left image is definitely improved by all the stuff to snag reflections on the left.

And my stereo cab extends past the plane of the right speaker.

Gardenstater · February 2023

My local audio bud Steve has been building a bunch of these and we had 5 of them in my office listening room to great effect. They are self standing but are best with a stand underneath them to raise them up or you can stack two of them vertically.

American Breakfast =(?) Breakfast in America

https://www.youtube.com/watch?v=FqXOLOy4jnU

plastic_avatar · February 2023

Ha!

I was craving a German breakfast today. Like, bigly mucho craving.

Rona brain, love it =P

heiney9 · February 2023

Impedance varies with frequency, so simply putting a meter across the terminals won't give you the any sort of answer as to what the speaker impedance is.

the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.

H9

xschop · February 2023

It would give him a baseline to judge if someone else posts their 1C's DCR, would it not?

heiney9 · February 2023

Except it's a meaningless measurement. It tells nothing.

H9

xschop · February 2023

heiney9 wrote: »

Except it's a meaningless measurement. It tells nothing.

H9

Kinda like freq. response graphs that don't convey sound quality?

plastic_avatar · February 2023

How would a meaningful measurement be made?

Could you recommend a way to take some measurements that would be worth doing? Could they be done with a voltmeter and without specialized equipment?

I thought a reading at the terminals would be something, but it would be great to have someone who knows more help!

Got an outline of how we could do it?

Or if any measurements matter?

SeleniumFalcon · February 2023

Here's how to measure your speaker's impedance:

1). you'll need: an audio signal generator, an audio amplifier of moderate power, a volt/ohm meter and a 2.0K ohm resistor of at least .5 watts power.
2). using the volt/ohm meter measure the actual resistance of the resistor, for this example let's say it measures exactly 2.0K ohms.
3). use speaker wire to wire between the amplifier and the speaker with the resistor placed in series with the positive wire. Place the volt/ohm meter with a probe on either side of the resistor with the meter set to read AC voltage.
4). set the audio generator to 400Hz and adjust the volume until the meter shows 10 Volts. To calculate the current flowing through the resistor at this frequency divide 10 Volts by 2,000 Ohms (keep in mind your particular resistor might be higher or lower than this example and you would divide by that amount). For this example you would get 0.005 Ampere, moving the decimal to the right 3 places gives 5.0mA of current. Now this gives you a constant current source to drive the speaker.
5). place the meter's probe across the speakers positive and negative terminals and measure the AC voltage. For this example let's say it reads 0.5 Volts. You would take our current value (0.005 Ampere) and divide by 0.5 Volts which would give an impedance of 10 Ohms at 400Hz. You would take whatever voltage you read and divide it by the actual measured resistance of the resistor.
6). repeat this procedure for all of the frequencies you want to know the impedance. The frequencies that gives the highest voltage readings would be the resonant peaks. The frequencies that give the lowest voltage reading would be the low impedance frequency points.

heiney9 · February 2023

How about this review from ages ago? The tweeter is different in your 1C, but I would think the electrical properties would be the same or close. The electrical properties of the upgraded parts in the x-over should about the same assuming the values are close to the originals (IIRC you didn't change inductors). I don't think damping material will change the electrical properties that much. The review will give you all the technical info you seem to want.

As far as a "do-it-at-home" procedure you need access to right equipment and the knowledge to use it properly.

https://polksda.com/sda1creview.shtml

Top of page 3 (left column) gives sensitivity and impedance measurements.

H9

plastic_avatar · February 2023

SeleniumFalcon wrote: »

Here's how to measure your speaker's impedance:
...

Fantastic! Exactly what I need to know. And something to shoot for. Thank you!

heiney9 wrote: »

The tweeter is different in your 1C, but I would think the electrical properties would be the same or close.

I hope so. Wondered if any if my changes affected the moving mass in a way that would affect the values (this is new thinking to me, so plenty to get wrong, right?).

The plugs (that's a lot of beautiful metal) are my biggest question mark for the total effect.[

The review will give you all the technical info you seem to want.

https://polksda.com/sda1creview.shtml

H9

Excellent! Much appreciated.

Instructions and learning to do. This helps a lot guys.

stangman67 · February 2023

FWIW, I appreciated seeing your modifications. I personally will never know if they hurt or help, but I’m sure you’ve had a good time. Haven’t seen so much negativity in one singular post in a long while time. I can certainly see why others may want to put up a disclaimer so people not in the know that may want to modify their SDAs don’t go down this path but other than that what’s the harm?

Gardenstater · February 2023

Not an officially Polk tested modification covers the disclaimer issue and anyone who does it will be going on anecdotal experimenter reviews, therefore eyes wide open.

skipshot12 · February 2023

Not sure there would be any effect on the sound of the phase plugs weight affecting the movement of the driver. If at all possible a way to measure the before vs after of each driver would be interesting.
Why I doubt the plugs will change any mechanical properties is, If I understand the mod correctly, you have to remove the dust cap to do the plug. You end up with whatever the difference in weight is which must be minute.

What you gain in any weight difference you now offset with less drag on the aero properties of the plug. Who knows…. Maybe the driver is now faster 😬

Waaaay more things to worry about than added mass when trying to figure out if it has affected the sound, or not.

Been enjoying reading your journey p_a……

Skip

heiney9 · February 2023

One thing that I can't reconcile is if phase plugs are so great and necessary as "choppy" seems to think they are, then why hasn't Polk incorporated them into their designs?

I mean reading "choppys" reviews you'd think that omission was a huge sin. I know other manufacturer's use them (or they use other manufacturer's drivers that use them), but Polk doesn't and their speakers have sounded damn fine for a long time.

I can see maybe not in the era the SDA comes from, but certainly as they continued to test and develop new drivers if this was something so necessary for good sound (as FP's are), they would have incorporated it a long time ago.

It's an honest question, may be someone can answer.

In the TSi 200 mod thread, "choppy" said he added phase plugs and now his TSi 100's sound fantastic. They are Tsi series, they are entry level adding phase plug shouldn't take them from mediocre at best to fantastic.

H9

P.s. I am not against trying mods.......I'm against over selling them and making them sound like they transform something beyond what it really is.

skipshot12 · February 2023

^ I can venture a guess….
The first would be cost? If Polk’s bean counters wanted parts in crossovers at the lowest price points to meet the minimum requirements of the original design for profit, rather than higher grade components for better sound & longevity.

Whomever put their fist down on the table and said NO to the less costly driver surrounds to stay with butyl…. Thank you.

I have more but it’s all speculative.

Pretty sure if Matthew Polk had his way we would have seen film caps, better resistors, better boards, different cab material and so on.

I’ll pose a couple questions to your statement of why they originally didn’t use Phase Plugs… did they even think of it? Did they actually try and found them to be inferior?

msg · February 2023

nooshinjohn wrote: »

I, on behalf of the entire Polk Forum, want to personally thank plastic_avatar on the fine work and dedication he has put into this endeavor of his to restore his Polk SDA 1c's, and sharing in great detail those efforts with the rest of the forum. No doubt his journey has been long and filled with potholes along the way, but the path he has taken should serve as an inspiration of what NOT to do when restoring and upgrading vintage Polk speakers.

May this thread live on forever as a means to enlighten those that follow in the art of what a disaster overthinking a simple weekend project can become.

Jfc, John, do you have any friends? lol

I'm actually interested in the info share, and insight into the analysis/"over-thinking", and process. I can appreciate this for the fulfillment of deeper involvement, and PA's obviously enjoying himself. Plus, lots of pics.

Documenting: My SDA-1c upgrades from start to finish

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