Monitor 12's crossover mod - can anyone make sense of this?

Zosimo

About ten years I blew one of my tweeters and Polk kindly sent me a new pair. While I was at it, I dropped my speakers off to be cosmetically repaired and rewired internally.

When I picked them up, the guy at the shop told me that he also modded and improved the crossovers as he found them to be rather poor and low quality. My question is: can anyone from these pics make any sense of what he did? And whether these components are effectively correct and better than the originals?

thanks

SeleniumFalcon

Probably the only way to unravel what was done would be to begin with the positive speaker terminal and see where this connection leads. Then start to draw a schematic diagram with each part labeled. In all likelihood (hopefully) the person just substituted one type of capacitor for another rather than trying to make a "better" crossover. You'll have to slightly moved the black wire tie to see the brand name and value of the capacitors.
In the world of amateur radio that kind of construction technique is called "dead bug", meaning parts stuck like insects on fly paper with twisted wires.

F1nut

It's impossible to tell from the pics what the component values are. Looks like they used basic film caps, which while better than stock aren't worth writing home about. I believe I see a basic block resistor, which should have been upgraded and never buried like they did. The coil looks like it was upgraded, hope they got the correct value.

You'll find the schematic in here, https://forum.polkaudio.com/discussion/38755/polk-audio-speaker-wiring-schematics-amp-more-all-models-except-sda

I'm not a fan of that slap it together work. Even though it may work it looks like someone doesn't care.

The wire is starting to oxidize at the ends, which is typical of that clear jacketed stuff and not good. I'd replace all of it with better chassis wire.

Gardenstater

I'm guessing you gave him the speakers and just said fix whatever needs fixing and give me the bill? He obviously eliminated the PCB and went sloppy point to point. Those Axiomedia capacitors are unknown to me and I don't know if they make them themselves or have someone else make them and put their name on them. All I can find out on their website is that the MKT are Polyester +/-5% and the MKP are Polypropylene +/- 3%.

We need more angles for photos to have any chance of ID'ing the components and what Selenium said regarding tracing vs the schematic F1 gave ya. I'd be concerned about the coil replacement. If it has a lower DCR, which is highly likely, it could throw the whole voicing off. Hard to tell by photo but that sure doesn't look like 22AWG to me. It will be interesting to compare the values of the resistors vs schematic. Wow lol.

pitdogg2

Another thing if I remember correctly. The polyswitch when it opens to save the tweeter actually sends the signal to one of the electrolytic caps. I remember having this conversation years back with Dave @westmassguy. He would be the only to have fix it if it needs it.

Unless yours was an early model that never had a polyswitch.

Zosimo

Right...hmm not good then. Can off-the-shelf crossovers be purchased for M12's?

Zosimo

Does anyone on the forum produce and sell the modified ones? I'm not ready yet for DIY stuff.

JayCee

Two forum members do XO work. @westmassguy and @VR3 both have stellar reputations and provide excellent work. They won't have anything off-the-shelf but worth reaching out to for a possible way forward.