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

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.

Gardenstater · February 2023

Some of the more expensive driver manufacturers use phase plugs quite a bit, like SEAS. It eliminates a kind of lobing where higher frequency sound waves from one side of the cone meet the ones from the other side and can have constructive/destructive interference. I've posted this stuff before, probably in xschop phase plug thread:

heiney9 · February 2023

skipshot12 wrote: »

^ 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 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 question 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?

Today, I don't think it's a cost thing. I was at HQ in the late 2000's and they showed us the room they tested drivers in complete with a Klippel machine, etc. Very, very expensive to R&D your own drivers from scratch. In the early days cost was more of an issue.

No reason the Legend line couldn't use phase plugs if they are so fantastical at transforming a lowly driver with a dust cap into something much more elevated. I am not commenting about what phase plugs do for speaker companies that incorporate them in their drivers. I'm sure they make a contribution to the final sound signature. I am commenting about them making a night and day difference on a 30+ year old MW driver. Because if it's that much better, then I would think Polk would have jumped on the bandwagon.

I'm curious, not trying to bash anything. I am also very skeptical of the "huge" transformation.

H9

Gardenstater · February 2023

Didn't MP say (paraphrasing cause I don't remember exact quote) that it is easy to make a no holds barred money is no object state of the art loudspeaker but quite a challenge to make an affordable one that comes close in performance?

xschop · February 2023

Whiney's assumptions are vast. The TSi drivers biggest improvement came from some inexpensive foam inside their frames and butyl mat. The plugs were icing on the cake and make them great near-field imagers.

The new Legend drivers are stamped- steel. They would benefit from foam too. Polk more than likely learned their lesson about using crap cast alloys on their LSi drivers that often cracked and I bet that didn't sound too gratifying.

Gardenstater · February 2023

As far as "fantastical" or "huge" goes, I don't think any of us that have done it have used those adjectives or gushed to that extent. When you are used to hearing songs you love and now after phase plugs you are hearing a nuance to cymbals that makes them sound more natural (for example), is that a small thing? I don't think so but it is a matter of opinion.

F1nut · February 2023

slow_polk7 · February 2023

F1nut wrote: »

Too soon!

skipshot12 · February 2023

heiney9 wrote: »

skipshot12 wrote: »

^ 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 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 question 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?

Today, I don't think it's a cost thing. I was at HQ in the late 2000's and they showed us the room they tested drivers in complete with a Klippel machine, etc. Very, very expensive to R&D your own drivers from scratch. In the early days cost was more of an issue.

No reason the Legend line couldn't use phase plugs if they are so fantastical at transforming a lowly driver with a dust cap into something much more elevated. I am not commenting about what phase plugs do for speaker companies that incorporate them in their drivers. I'm sure they make a contribution to the final sound signature. I am commenting about them making a night and day difference on a 30+ year old MW driver. Because if it's that much better, then I would think Polk would have jumped on the bandwagon.

I'm curious, not trying to bash anything. I am also very skeptical of the "huge" transformation.

H9

Good point....

plastic_avatar · February 2023

Ah, hot-rodding

I think of it like the 67 Impala I had.

It had a 327/300 from a wrecked Corvette in it. And every upgrade had a particular change that it imparted to the car. The headers, the Holley, a cam... each one of those changed the car in a way that would seem minor, but each revealed a change that improved the overall character (and enjoyment) of the machine.

I could've had a car that was just fixed up to run stock, and it would've been just fine and enjoyable and serviceable and all that, but... I had something that was more than it was capable of being as originally assembled.

There might be a night and day difference in some aspect of the performance of the machine after a mod, but not a night and day difference in the totality.

Like, on the phase plugs, the comments about meaningful changes in aspects of the recordings is reasonable. And those changes made a very big difference in the overall enjoyment of the machine for the users who installed them.

It's late, and I know my analogy isn't the best. Cut me some slack, it's 02:48

I think the mids are focused in a pleasant way in my 1C. Of course, with my all-in mega-mod, I can't point to plugs or matting or foaming or rings as one greater than the other in this equation of positive sound enjoyment. So other users who did the mod separate from other can better tell their impressions (I know some have).

Chameleon

I listened to it once to just get my bearings and see if I could handle it. Good news! It's jazz that doesn't make me want to die! I can follow it just fine. [whew].

I marked on graph paper where the sounds came from, where they roughly were in relation to the front of the room, and where the sound... was pointed. Not sure how to phrase that. I'm sooooo tired.

I'll post more about that later.

But what a great track to test your system. Wow. Very clear and detailed, with distinct spatial info and placement of instruments.

Gardenstater · February 2023

Another phase plug usage in some pretty high end speakers with interesting construction. Hat tip to Jazzhead:

"The woofers (and midrange drivers) all sport a phase plug that, in addition to making phase behavior consistent throughout the cone’s diameter, also aides in efficient heat dissipation which, in turn, is responsible for the high power-handling capability of these relatively diminutive drivers."

https://www.theabsolutesound.com/articles/von-schweikert-audio-endeavor-e-5-loudspeaker/

Jazzhead · February 2023

@plastic_avatar if "Headhunters" grows on you, you might crank "Thrust", Hancock's next album in a similar vein. The soprano sax solo on Butterfly is a good glare test, as it should cut through, but not sound harsh at loud volumes. Like Headhunters, there are some great bass lines and percussion parts to listen for.

Gardenstater · February 2023

Von Schweikert's phase plug implementation on the midranges:

plastic_avatar · February 2023

@Jazzhead I'll mark that for next payday's CD purchase.

Diagrams that might mean little to anyone right now

I and my oldest daughter tracked distinct instruments/sounds across the front of the room. Song, Chameleon. These spatial perceptions were for the first 7+ minutes of the recording.

The 5 blocks on the diagram are, from left to right: subwoofer/guitar amp, left speaker, tv/stand, right speaker, stereo cabinet.

I have a hard time telling if something is a guitar that's heavily filtered, or keyboards, or... For, example, Stevie Wonder's Superstition still confuses my brain after all these decades. So I use numbers to places where I hear things, rather than naming them. Daughter has a similar brain.

The numbers represent distinct sound sources and the order they appear, sequentially.

1) Me, noting approximate location of distinct instruments, what direction they might appear to migrate to or face, and their general positions front to back across the sound stage. Eyes open. I'm more reserved and restrictive in my notation than she is:

2) Kira, same directives, but she had her eyes closed and noted more distinct sounds, their positions, and how they moved and where she felt the sound went- irrespective of the perceived instruments making them:

Initial takeaway w/o DK'ing a thorough write-up

- We both dislike the high-pitched frenetic keyboard action. Not enjoyable to our ears, but the rest is. Muchly so.

- Our placement of major elements is similar. She was taken aback by how much went beyond the walls.

- The stage was crescent shaped, with some sounds coming forward in intensity and placement. The core 4 sounds/elements/patterns of the song (keyboard, bass, drums, guitars) stayed close to their original positions, with embellishments and additions coming from (and sometimes moving to and from) additional locations. Horns were more a wall of force in our minds.

- She noticed the same left channel room bias my youngest did. Gotta treat the right wall!

That was a fun preliminary listen to get our sea legs. We'll try more things in the coming weeks.

Get bent

Song: No one dies from love, by Tove Lo.

The best endorsement I could get for how this project turned out (to date) is my 17-year old, overwhelmed after listening to a song, crying.

She was surprised how clear the mix was, how emotional it made her, and how detailed the music was.

'Why don't more songs make us feel this way?' she asked. 'Why don't they sound as clear and... big?'

I told her that when a mix is done right, it sounds very different if you have a way to hear it other than through the dreaded earbud.

She said 'I wish everyone could hear music this way, but it's not practical, is it?'

No, sweetie. It's not.

It was an awesome listening session.

heiney9 · February 2023

Too bad you never did this comparison on the 1C's before you molested them. Then you could have compared them at each step up to the final product.

Now, your observations mean nothing as to how the changes improve or detract from the original, which is really what's important when making all the changes.

Rock on

H9

xschop · February 2023

Maybe you can offer him a listening session of your 1C's?

A very thorough write-up @plastic_avatar

skipshot12 · February 2023

Hey p_a…
Dang interesting way to evaluate what you’s are hearing.
Question, what do the increase in the numbers mean?
As in that left channel the number is higher towards the listening position?

Gardenstater · February 2023

heiney9 wrote: »

skipshot12 wrote: »

^ 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 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 question 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?

Today, I don't think it's a cost thing. I was at HQ in the late 2000's and they showed us the room they tested drivers in complete with a Klippel machine, etc. Very, very expensive to R&D your own drivers from scratch. In the early days cost was more of an issue.

No reason the Legend line couldn't use phase plugs if they are so fantastical at transforming a lowly driver with a dust cap into something much more elevated. I am not commenting about what phase plugs do for speaker companies that incorporate them in their drivers. I'm sure they make a contribution to the final sound signature. I am commenting about them making a night and day difference on a 30+ year old MW driver. Because if it's that much better, then I would think Polk would have jumped on the bandwagon.

I'm curious, not trying to bash anything. I am also very skeptical of the "huge" transformation.

H9

What does the age of the driver matter so much when basic moving coil/permanent magnet loudspeaker design hasn't changed in that time period (more like 44 years in the case of my speakers). Why didn't Polk put constrained layer damping material on their stamped steel baskets? Why didn't they put a square of open cell foam behind the midwoofers?

I'm sorry but you are like someone reviewing a movie they haven't seen and not accurately quoting those who have.

It takes some sophisticated equipment like laser interferometers to make an inexpensive to produce speaker that outperforms speakers costing much more, so that doesn't really have a lot of bearing on them not incorporating phase plugs, shorting rings, cast aluminum baskets, etc., that do add appreciable cost to manufacture.

xschop · February 2023

Polk used sub-par caps and crap cast resistors to cut costs. They also went backwards by using plastic tweeter bezels vs earlier metal plates to cut costs, not for a SQ improvement.
The particle board enclosures were questionable too IMO. I do like that they went to strong MDF in the RTi series and used them as donors for a build.

invalid · February 2023

Just because phase plugs work in one speaker design doesn't necessarily mean it will work in the 1C's, there are tradeoffs with phase plugs.

Gardenstater · February 2023

invalid wrote: »

Just because phase plugs work in one speaker design doesn't necessarily mean it will work in the 1C's, there are tradeoffs with phase plugs.

Please elaborate.

That was not my point. From what I've gathered in my research, great drivers can be made with phase plugs and great drivers can be made with dust caps. It is all in the R&D and execution.

The positives to be had with phase plug implementation make it a very worthwhile experiment.

invalid · February 2023

Cone Speakers designed properly with phase plugs attach the phase plugs to the pole piece and not the cone, Some efficiency is lost with this design. Some speakers have the phase plugs attached to the cone, which has little if any effect.

Gardenstater · February 2023

Efficiency at higher power levels is actually improved, by cooling the voice coil and reducing power compression.

The small loss of cone area is probably more than offset by not having to compress the enclosed air space underneath the dust cap which can also be a source of resonance and coloration.

I haven't noticed any dB drop on the freq. response curves I have made and compared to pre phase plug.

Anything attached to the cone is just a pointy shaped dust cap and would lose most of the benefits of a phase plug attached to the pole piece.

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

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