Monitor 10A Crossover Upgrade/Fix

hazyIPA

I've read that updating the crossovers makes a big impact on these speakers. Also, one of the two speakers' binding posts are gone with speaker wire soldered in place. This is how they were when I bought them. It works, but it's not ideal. (I've repaired the broken wire seen in the photo.)

I'm a dummy when it comes to understanding electronics, but I'm comfortable soldering when I know I have the right parts going in the right place. So, I'm looking for help identifying which parts to replace, what to replace them with, and what to do, if anything, about the binding posts.

JayCee

hazyIPA wrote: »

I'm a dummy when it comes to understanding electronics, but I'm comfortable soldering when I know I have the right parts going in the right place. So, I'm looking for help identifying which parts to replace, what to replace them with, and what to do, if anything, about the binding posts.

Welcome to Club Polk, @hazyIPA! I'll start by saying I love a good hazy IPA.

Sounds like you have the basic skills to redo the XO's. Never had your 10A's but have modded multiple sets of Polks. I'm not too original so just got my read on using CP and did the "monkey see, monkey do" blueprint of other Club Polk members.

Should be an easy upgrade and given the age of the speakers definitely in need of refresh, which will do wonders for the sound. Source the same value caps and resisitors. Sonicaps (http://www.soniccraft.com/index.php/sonicap-m-21) and Mills resistors are the preferred offerings but you'll also find lovers of other caps on CP.

Binding posts can be upgraded but are not an immediate necessity. I have spare OE posts in my parts stash you can have for free, if you want to stay stock. Once you get your post count up and are able to PM I'd be happy to drop them in the mail if you send me your address.

Also, consider upgrading the tweeters to replacement offerings from Polk depending on what you have. I'll let other's chime in with more experience w/the 10A's but in the meantime get your read on:

https://www.google.com/search?q=club+polk+monitor+10a+crossover+upgrade+site:forum.polkaudio.com&sa=X&ved=2ahUKEwjlg9Xb95fnAhXQCTQIHcRPB9EQrQIoBDAAegQIBBAP&biw=1089&bih=735

Again, welcome to the forum!

John

pitdogg2

10a should have the Peerless tweeter, nothing to upgrade there.

hazyIPA

JayCee wrote: »

Source the same value caps and resisitors.

So, looking at the photo below, should all six parts be replaced? Which ones are capacitors / resistors?



And, thanks for the warm welcome!

RandyCroissant

Welcome to the forum Hazy IPA the item number 4 is an inductor no need to replace. The other items are either capacitors tube shaped or resistors rectangle shaped, much better parts are available do a search and you will see what I mean.

JayCee

hazyIPA wrote: »

JayCee wrote: »

Source the same value caps and resisitors.

So, looking at the photo below, should all six parts be replaced? Which ones are capacitors / resistors?

• Caps-2, 5, 6
• Resistors-1, 3
• Inductor-4

As RandyCroissant stated, the inductor is not necessary to replace. There are better but are a bit tricky as you need exact values that are very critical to the voicing of the speaker. If inclined, replace at a later time with the expectation of lesser improvement. The caps and resistors result in the most immediate improvements.

Caps can be replaced with values that are within 10% of what's printed on the cap, perfectly fine to do and within tolerances of how Polk did it, too. If one of the values is large, cost prohibitive or not available, you can combine 2 caps of lesser values, wired in parallel, to equal the required value. Example, 52 μF can be created w/2 26 μF caps. Of note for caps, depending on the manufacturer you choose and physical size, a challenge may be being creative when mounting the new cap(s) to the XO board. Don't let this dissuade you...IMO, it's part of the fun working with these old boards.

tonyp063

This is a good thread to look through.

https://forum.polkaudio.com/discussion/174426/another-monitor-10a-thread

hazyIPA

tonyp063 wrote: »

This is a good thread to look through.

I will open mine up to confirm, but looking at tonyp063's helpful link, it looks like the values and my guess at replacements could be:

1. 2.5 ohm resister - link
2. 34 uF capacitor - link
3. 2.7 ohm resister – link
4. Inductor – Keep Original
5. 12 uF capacitor – link
6. 34 uF capacitor – same as #2

Do those replacement look right? And, what level of “Precision Matching” would you suggest?

JayCee wrote: »

a challenge may be being creative when mounting the new cap(s) to the XO board.

That definitely seems to be true looking at other crossover upgrades!

tonyp063

Don't buy components until you look at what's actually in yours.
L1 precision is fine. Don't forget that Polk used, at best, 10% back when.

Don't forget binding posts too.

Gardenstater

@hazyIPA be careful as I checked your links and the values are wrong. Check the decimal places. Gonna be quite a bit more expensive than those

Gardenstater

@tonyp063 I am also doing what the OP is doing, but on a pair of 7Bs. What binding posts would you recommend? Been checking prices and WOW !

tonyp063

heh. Yeah, The price diff between a 0.0033uF & a 33uF is *rather* significant.

Cardas are not cheap, no.
I used Solens when I did mine because I was getting my parts from Parts Connection

hazyIPA

Gardenstater wrote: »

@hazyIPA be careful as I checked your links and the values are wrong. Check the decimal places.

Doh! Good catch! How's this list looking now?

1. 2.5 ohm resister - 2.5 Ohm Vishay Mills 5 watt MRA-5
2. 34 uF capacitor - Gen I Sonicap 34 uF 200VDC
3. 2.7 ohm resister – 2.7 Ohm Vishay Mills 5 watt MRA-5
4. Inductor – Keep Original
5. 12 uF capacitor – Gen I Sonicap 12 uF 200VDC
6. 34 uF capacitor – same as #2

I'll be sure to check the values on my speakers before moving forward.

Gardenstater

@tonyp063 Thank you. Found 'em and the price is reasonable. Gold plated brass and they have a male faston tab, probably .205". I guess to get gold plated copper billet you have to spend much much more. Don't know if the difference is audible?

Oh could you tell me if they are for 1/4" ring terminals/spades or 5/16" ?

https://www.partsconnexion.com/SOLEN-51541_ss43741.html

F1nut

Copper billet with direct gold plating. Worth every penny.

http://www.soniccraft.com/product_info.php/cardas-ccgg-binding-post-p-1387

tonyp063

@hazyIPA

go for the 12W resistors rather than the 5W

hazyIPA

hazyIPA wrote: »

Doh! Good catch! How's this list looking now?

I noticed a couple things I had overlooked...

1. 2.5 ohm resister - 2.5 Ohm Vishay Mills 12 watt MRA-12
2. 34 uF capacitor - Gen I Sonicap 34 uF 200VDC
3. 2.7 ohm resister – 2.7 Ohm Vishay Mills 12 watt MRA-12
4. Inductor – Keep Original
5. 12 uF capacitor – Gen I Sonicap 12 uF 200VDC
6. 34 12 uF capacitor – same as #2 same as #5

Oof! If that list is right, that's >$250 in parts for the 2 speakers.

Gardenstater

Ha ha welcome to my nightmare as well lol! I love these speakers and get tremendous enjoyment from them though!

@F1nut Those cardas binding posts are beauties no doubt and I really do want to stick to copper base metal, whether plated or not. I found these obvious made in China deals on amazon. Whadya think? They are short and I like the set screw, in addition to being solderable and they are pure copper conductor. All of these mfg's are pretty vague on details, especially the high end ones which gets frustrating. I mean am I to *assume* because it's Cardas that it is something like 4N copper or better....they don't say. I could use my Silclear silver platelet grease on the copper ones and maintain them every so often with the De-oxit.

https://www.amazon.com/ZXHAO-Speaker-Amplifier-Terminal-Binding/dp/B07HYY1TQ1/ref=pd_sbs_23_2/140-6877126-1564253?_encoding=UTF8&pd_rd_i=B07HYY1TQ1&pd_rd_r=7c1bb6a6-b433-4955-9e9f-3ea09643f087&pd_rd_w=UB0Wn&pd_rd_wg=bLYX3&pf_rd_p=bdd201df-734f-454e-883c-73b0d8ccd4c3&pf_rd_r=07FJPX6SCBB7MZ357K34&psc=1&refRID=07FJPX6SCBB7MZ357K34

F1nut

Roll of the dice, I would say.

lmacmil

What's the rationale behind replacing the resistors? Is it because the original values may have drifted or is their some perceived sonic benefit with new or "better" resistors? I have 35 year old 7Bs that I need to re-cap (at least.) Not sure why I need to do resistors if they are still within the tolerance of their nominal values.

Gardenstater

You can read here: https://www.hificollective.co.uk/components/mills.html

"Mills Series Non-Inductive wirewound power resistors are very popular in audio, infinitely better than the ceramic "grey" type. An Aryton-Perry design with tinned copper leads, silver plated end caps. The core material is an alumina ceramic, providing significantly broader heat dissipation compared to that of normal steatite ceramic core. There are no magnetic materials used in these resistors. Applications include cathode resistors on valve output stages, power supplies, valve anode resistors and in speaker crossover networks. We stock MRA12, 12W range and the MRA05, 5W range. Please note it is sonically better to use a higher power resistor due to increased surface area. Tolerance is 5%."

and here:

"Non-magnetic, non-inductive, all welded construction
greatly enhances frequency response. Combined with
Aryton-Perry winding inductive reactance and signal
loss are almost totally eliminated.
Meets or exceeds the specifications in MIL-PRF-26
for wirewound resistors.
Meets the applicable specifications of MIL-STD-202,
method 208
Core: Alumina ceramic. This material
provides significantly broader heat
dissipation compared to that of
normal steatite ceramic core.
Element: Nickel-chromium or nickel-copper
alloys used.
Leads: Tinned Copper with Silver-plated
endcaps."

https://hfc-fs.s3-eu-west-1.amazonaws.com/s3fs-public/mills_data_0.pdf

Viking64

RESIST NOT THE RESISTORS!!!!

Faustin

In regards to replacing the resistors.............for the price of them, why wouldn't you? If you are going to replace the old, past their life caps, do the resistors as well. At the very least you know that everything is up to spec.

lmacmil

Faustin wrote: »

In regards to replacing the resistors.............for the price of them, why wouldn't you? If you are going to replace the old, past their life caps, do the resistors as well. At the very least you know that everything is up to spec.

And that's the best reason I've heard!

Navy_Goat

You could save a little coin by using some cheaper alternative caps in the lower frequency side of the crossover. You would need a schematic or someone to point ou the cap (caps?) which are in that side of the circuit. This hobby is like most others, the sky is the limit with most projects, but you can find cheaper alternatives which will not disappoint. Some research should lead you to more options. The members here are super knowledgeable and most are willing to help us newbs along. Good Luck with the project. Regardless of what you choose you will not be disappointed once everything is back together.

tonyp063

If you go with Clarity CSA you will save about $30/crossover. They are the other well considered cap for vintage Polks.

I have used them and I like them.

Gardenstater

I wasn't going to post this but here goes......this guy actually tested and reviewed tons of different capacitors and gave them relative ratings on a chart with the highest coming in at around 15 on a 0 to 20 scale, as well as gave his preferred ones! Must've cost him a fortune!

http://www.humblehomemadehifi.com/Cap.html

Sonic Craft Sonicap GEN-I MKP 220VDC - 5% tolerance

Sound: Compared to a standard Mundorf M-Cap they are more transparent and clearer with lots more depth. Putting a 0,01uF Vishay MKP1837 parallel to them (a good tweak for nearly any capacitor) can create even more detail and separation! They reveal micro-information in a way that reminds me of a Hovland Musicap but without the Hovland loudness effect. I didn't find them to mix well with other caps - a 50/50 mix with a standard Mundorf M-Cap gave me the funny sensation of listening to two different cap's at the same time. I can advise them if you are looking for a high-end cap but are on a relatively tight budget. Quite nice :-)

Verdict: 8,5

Clarity Cap CSA MKP 250VDC and 630VDC - 5% tolerance

Sound: The tonal character of the Clarity Cap CSA has in common with all Clarity Cap capacitors that is well balanced and never fatiguing. The CSA shows a pleasent intimacy combining the clarity (pun intended) of the ESA with the smoothness of the larger MR. Relatively speaking, I actually found the step up in sound quality from the ESA to the CSA to be greater than from an MR to a CMR. Both the CSA and CMR use Clarity Cap's Copper Connect Technology but it seems to have a greater effect on the SA range than of the MR range. Maybe it's easier to improve lower down the scale than further up it, I don't know, but that is how it cames across to me. Anyway, in direct comparison to the CSA the ESA sounds a little rougher, the CSA seems to produce a more civilized image that is at the same time more neutral. "S" and "T" sounds that were first maybe a little bit rough around the edges with the ESA (I am being very nit-picky here) become free from grain with the CSA. I also found the CSA to mix extremely well with the Jantzen Audio Alumen Z-Cap. A mix of a minimum of 20% Alumen Z-Cap with the rest Clarity Cap CSA enhanced realism of space and lushness of tone. They blend together seamlessly. All in all the Clarity Cap CSA is a well balanced, neutral capacitor that is a welcome addition to capacitors in the lower price range.

Verdict: 9

PS: you could save about $70 by going all ClarityCap CSA vs Sonicap Gen1, but I can only find a 33uF for ClarityCap vs 34uF desired. Having said that, I have already ordered Sonicap Gen1's for my crossovers so I hope they are better

Gardenstater

These ones are very high end apparently, and I see that a 12uF costs around $54 vs $28 for Sonicap Gen 1 and $18 for ClarityCap CSA. So we are going the wrong direction clearly with this choice.

Jantzen Audio Superior Z-Cap 800VDC - 2% tolerance

Technical specifications (according to manufacturer): "Double foil super PP capacitor featuring extremely high quality German made foil, metalized with aluminum and zinc particles. Featuring terminal leads made from PCOCC copper (oxygen free). Nitrogen filled instead of dielectric fluid, offering more foil per capacitor and eliminating risk of evaporation. Voltage rating 0,10uF - 0,33uF: 1200VDC or 600VAC, Voltage rating 0,47uF - 22uF: 800VDC or 425VAC, Non inductive construction, Terminal leads are made from Pure Copper Ohno Continuous Cast Wire (oxygen free), Capacitance tolerance : +/- 2%, Voltage rating: 800 - 1200VDC, Loss factor: 1K 0.00002 10K 0.00001, Non-polarized capacitor".

Sound: Very neutral and coherent balance, they don't seem to high-light anything and I mean that in a positive way! They are a little flatter in presentation than their more expensive brother, the Silver Z-Cap but still better than the Clarity Cap ESA in depth and spatial information. In direct comparison with a Clarity Cap ESA they are less up-front in the lower treble and have a better texturing of acoustic instruments like a violin for example. In the upper treble they are slightly clearer than a Mundorf Supreme Silver/Gold which probably explains the good spatial information and separation. Compared to the Jantzen Audio Silver Z-Cap I find them the more musical of the two. The Jantzen Audio Superior Z-Cap is a no-brainer if you are looking for a capacitor that performs well in all area's and is very well balanced. One of my personal allround favourites :-)

Verdict: 10+

mhardy6647

Gardenstater wrote: »

F1nut wrote: »

Roll of the dice, I would say.

One tends to get what one pays for.

Gardenstater

@mhardy6647 Aargh I know I know, but they say it is pure copper conductor and it's just a binding post with threaded components right? It's awful tempting to pay $18 for these vs $94 for the Cardas, which doesn't even have the set screw.

I'm looking at the Chinese ones and it sure does look like it's gold plated (or worst case brass lol), I mean does that look like copper? Sent them a question asking same.

I think it's pretty hard to verify whether something is made out of copper or brass unless you can weigh the under water and above water maybe to calc. the density. Could be lots of fake copper binding posts out there. Another way would be with a hardness tester because I think most certainly copper is softer than brass. Decisions decisions

PS: Perhaps I will get the Chinese ones from Amazon and if I can scratch a pre 1984 copper penny with the sharp end of the binding post, I will assume it's brass and demand money back from Amazon (sounds like a plan lol)

F1nut

George, most of us here are very familiar with Tony Gee's capacitor site.

As you noted with the Clarity caps, most of the choices out there do not have the exact values required for Polk crossovers. Jeff, the owner of Sonic Craft/Sonicap made sure to offer caps in the exact values we need, which is fortunate because Sonicaps work extremely well with vintage Polk speakers.