Monitor 70 crossover help for noobs like me

turn8

hello everyone,

i want to upgrade some components on my monitor 70 towers,

what i hope to accomplish is a larger sound stage and brighter highs, also putting together this thread with pictures to help out others who may have questions like i do.

i have some decent soldering ability, but i dont know much about electronic components.

i took a couple pictures i found on the net, and combind them to get this:


5333813040_b72c95b2bf_b by turn8, on Flickr

i numbered all the components on the board, and need some help identifying them, and also what to replace them with if anything...

this is what i think they are...

1: bypass cap? i read some controversy about if this should this just be removed instead of upgraded
2: high freq cap. id like to replace this with a clarity cap
3:low pass coil. is there a need to replace this?
4:high pass coil. is there a need to replace this?
5:resistor in high pass. i am thinking this should be replaced but not sure with what
6:mid range resistor? same as above not sure what to replace this with
7: mid range cap. id like to replace this with something that is going to give me the biggest sound stage as possible, if thats a clarity cap so be it.
8:Mid range coil. same as all the other coils, does this need to be replaced?

also i read about shunting a driver with a capacitor for better sound, and i wasnt sure what that even means

thanks for any input or help with this project

Esreuter

hey turn,

welcome into the forum.

your going to have fun with this upgrade and the results you will get after will be worth your investment.

i have to sources you should read. if you have not already. if you did please ignore me.

http://www.polkaudio.com/forums/showthread.php?116146-Crossover-Mod-for-Monitor-40

http://www.polkaudio.com/forums/showthread.php?125139-Monitor-XO-build.

The bottom thread is my thread, and i have come a distance since then, i at least learned what a sine wave is and its relations to everything.

after this you should decide if your going to do a full rebuild or certain upgrades. resistors and caps only, or inductors only, ect.
to answer you with in my experience:

1: it is a bypass/safety cap, there is controversy. I just put its value into the cap it was bypassing and removed it. if i remember correctly it was a 8.0uf, i put in a 8.2uf and all is well. you can keep it or take out.

2: great choice! i used the PX line because it was my first mod and i wanted to not spend all to much. the $ is up to you.

3: that is correct, that decision is up to you. i replaced mine with an air core and noticed improvements in the low ends. Generally inductors can be hard to match and are pricey those 1.3s are 30 bucks each, if my memory serves me.

4: you know your parts, personally its already air core and there really isnt an advantage in sound to replace it. there are advantages in replacing it if your going to do a complete rebuild point to point. biggest advantage is if your doing a full rebuild on the XO you dont have to deal with that epoxy, it's a mother, even with heat and alcohol. second advantage in replacing it, its only $2 for a new one, personally not dealing with the epoxy is worth $2, to me. third, again if your going full rebuild, you will always have a complete XO as a back up in case of any thing wrong you wont have any down time.
if your not going full rebuild leave it.

5: in my opinion yes, replaces this with a better resistor type. I personally used the mundorf metal oxide film from madisound @2.50$ each. very good and very popular are the mills non inductive wire wounds at parts express or soniccraft for ~4.50 each.
generally when people upgrade an XO the mains parts changed are the caps and resistors. you will notice improvements.

6:yes, see above.

7: i cant suggest a cap, i used clarity cap PX across the board. very happy, then again i am a uniform type of guy, there are several other members who can suggest the best caps for mid range.

8:in my experience, yes. air coil, will really clean things up.

on shunting, your XO design has already taken care of that for you. i suggest you to read up on shunt in the electric engineering forums and on the net. All i can say is that it puts components in a short before the driver, what components and what they do goes beyond my knowledge.

if you get stuck or need anything that i can answer please give me a holler. I really enjoyed building my XO's and you will notice and enjoy the sound when you are finished. If you get nervous and feel its to much for ya, I would jump at the opportunity to do it all again for ya, though it would be smaller as with my lay out on the peg board i made it big so i could understand the flow of electricity and circuit design. Having an opportunity to do it again i would shrink and tidy things up greatly.
Make sure thats your last resort though, i dont want to rob you of the opportunity to do it yourself.

thanks for reading and I hope this helps you out.

ESR :loneranger:

turn8

thank you for the awesome reply, i did see your crossover rebuild and thought that might be going further than i wanted to go for now..

the big question i have now, is do i stand to benefit form upgrading my entire system, (monitor 70s up front, CS2 center and monitor 50 rears) or could i get away with just the front

also i was reading an article saying adding a small value bypass cap helps to clean up any cap, the recommended cap was a .1uf MKP1837

here is what i have in my cart so far


polk upgrade by turn8, on Flickr

Esreuter

Whooo hooo money bags!

The answer to the big question is up to you, dont you just love those "it depends answers."
In my thoughts since you have such big ones M50's in the rear i would say yes.

That is a big yes on upgrading the CS2, thats your work horse.

On the idea of bypassing, or at least as i have learned, if you bypass a lower grade cap with a high end cap and it really cleans up the sound.

But you choose ESA line, personally there is no need to bypass those, and i dont know much about the vishay line

hang on, torando sirens are blowing

Esreuter

ok sorry,

That was fun, funnel must have been closer to town and not by my house entirely.

anywho.

as i was saying, i dont know much about the vishay line and their quality. Maybe they are uber good then if you want to bypass the ESA its up to you, but bypassing allows the cap to add its characteristics to the sound. I could of stood to gain greatly by putting ESA bypass on my PX line, but at that time i did not have this knowledge.

again, if you want to bypass, the ball is in your court, I say the ESA line is good enough. Then again 2.25 in this hobby is not a big deal.

since your going big, make sure to check out some Mills resistors, many people swear by them. Or, try out the wire wound Mundorfs on madisound they are 12$ bucks each, if you do make sure you write a report, i am curious about those and how they sound.

Caps and resistors will be a great upgrade that you will notice. make sure you get a heat gun and a hot knife, that epoxy will be fun, and polk spared no expense, its just dumped on there.

ESR:loneranger::loneranger::loneranger:

pitdogg2

No need to use bypass cap. like what was said used on inferior caps in this case electrolytic. It was also used in cases of wider tolerances using a better 3% tolerance caps negates that need.

turn8

good to know... thanks for risking life and limb to post

i will probably go with the mills i wasn't planning on changing the resistors but they are cheap insurance. what spec mills should i get? they have MRA-5 and MRA-12 (guessing the MRA-12)

the other thing i need to upgrade is my receiver, its an old denon that doesnt have any hdmi, and i think is only rated at 85 watts pr chan.

pitdogg2

turn8 wrote: »

good to know... thanks for risking life and limb to post

i will probably go with the mills i wasn't planning on changing the resistors but they are cheap insurance. what spec mills should i get? they have MRA-5 and MRA-12 (guessing the MRA-12)

the other thing i need to upgrade is my receiver, its an old denon that doesnt have any hdmi, and i think is only rated at 85 watts pr chan.

mills 12 watt cheap insurance although you can use both. I went with the 12's when i did my XO's

pdxfj

When I upgraded the XO's on my RTi-A7's and CSi-A6 I went with Trey's recommendation and used the PX line for everything and bypassed with ESA caps. I also used Mills resistors.

Couldn't be happier with the results. Using the PX line will save some cash, if you're wanting to.

The ESA caps are quite a bit larger than the PX line, so space could be a concern. Especially in the CS2.

As others have said, let us know how things turn out.. that is after breaking them in for 200 or so hours. )

turn8

i need Three 5.7 ohm mills resistors for the m70s and CS2 and unfortunately parts connexion only have a 5.6 listed, is .1 ohm small enough a change to overlook?

turn8

pdxfj wrote: »

When I upgraded the XO's on my RTi-A7's and CSi-A6 I went with Trey's recommendation and used the PX line for everything and bypassed with ESA caps. I also used Mills resistors.

Couldn't be happier with the results. Using the PX line will save some cash, if you're wanting to.

The ESA caps are quite a bit larger than the PX line, so space could be a concern. Especially in the CS2.

As others have said, let us know how things turn out.. that is after breaking them in for 200 or so hours. )

yes, i had the CS2 apart last night and there is a lot of fiber fill in there, i think there should be enough room, if not i can come up with some kind of creative solution.

the ESA 250v line is a cost savings vs the 630v line so if the ESAs are better i am ok paying for the 250v version.
i was originally looking at sonic caps for the low range and clarity for highs as stated in bens cap shootout, but they cost about the same as the 250v clarity ESA, so my thinking was why not keep them all the same..

Esreuter

the general guide line is stay with in 10% of original spec.
5% of original even better.

in short yes, 5.7 replaced by 5.6 is fine.

esr:loneranger:

Esreuter

Watch it on that CS2, i forgot for a second, if you put even the smaller 250v caps on your circuit board you wont fit thru the back hole again.

unlike your 70's and 50's that circuit board is not mounted to the terminal cup. in the 70 and 50's you can simple un screw it and access thru a driver port.

with the cs2, the board is simply put into grooves on the terminal cup and held in place by tons of epoxy. stock it slides in and out and the hole for mounting the terminal cup wont offer enough room for placing a stacked XO thru it.
i would hate to see you do all that work only to have to heat it all up or take it apart again.:cheesygrin:

it's not a bad fix, you'll just have to heat and remove the PCB from the terminal cup mod, then return thru the driver port. though it may not slide back into the original grooves because of all the new jazz on the board. Also if it does fit you'll have to anchor it so you wont hear it shaking around in the cabinet, easy solution? EPOXY yaayyyy!:cheesygrin::cheesygrin:

that will be interesting how you deal with that, please take photos of the whole process. i had it easy, just mount to peg board and then i screwed into the back wall.

esr:loneranger::loneranger::loneranger:

turn8

can the cap be remote mounted? that could be the easiest solution

Esreuter

of course, you can run wires from the cap leads to the pads on the PCB.

the general idea is the shortest path for the signal is the best, but there are cases where you do what you have to do.

ESR:loneranger:

turn8

if this doesnt work ill have to buy cm9s

turn8

looks like this upgrade is going to have to wait a bit, i just got an onkyo 809 and wow what a difference in sound, it is night and day from my old denon. i do think there is still some room to clean up the high end with the caps, they are a bit scratchy.

Esreuter

there is always room for improvement.

thats the scary thing

esr:loneranger: