Cat Scratch Fever

[Wade Spradley]

Hello to the forum. I been off and on over the last few years mainly reading posts and researching Polk Monitor Speaker component upgrades to the crossover. I have recently (this weekend) acquired a set of Polk Monitor 10B’s from goodwill for the whopping sum of just less than $32.00. The condition of the speakers on the outside exhibit a scratched up top on each of them on the wood grain vinyl covering ( I recently read a post where someone veneered their Monitor 10’s speaker with real wood. Good for him, I need to make notes on that for the future of these speakers). Also at one point four ½ inch screws were not very politely embedded into the bottom of each of the speakers (currently removed), which is where I believe the scratches on their tops came from. The grills came with each of the speakers but I believe who previously owned the speakers had a cat that used them for a scratching post, one side of one grill has been shredded to the wood, a cleanup and recovering of the grills is in order. On inspecting one of the speakers there was no 1 Amp fuse in its receptacle, it had a piece of wire wound onto it. Definitely shorted together there. The other speaker had a unknown rated fuse in it. I powered the speakers up even with the shorted fuse holder and they sounded great, but the tweeter on the shorted speaker was scratchy. So the next day a visit to Radio Shack and I picked the correctly rated fuses, and it cleared up the scratchy tweeter so I thought. I’ve been testing the speakers with a variety of music and once in awhile the tweeters get scratchy, is it possibility that the crossovers need to be rebuilt or is the tweeter (s) shot? I have a pair of Monitor 7 Series 2 as well, which have their own unique problem, which I will save for another discussion. I like to say thank you to the person that uploaded the Monitor Series crossover schematics, it solved my fuse question, I would have asked at one point.

Any recommendations or thoughts would be appreciated. The speakers definitely sound great, I am currently playing some Mozart Quartets to give the tweeters a bit of a workout, and at times the scratchiness manifests itself, mainly on one tweeter but I am not sure about the other. Also, is there suppose to be some fluid enclosed by the plastic dome cover over the tweeter? I could be wrong?


Stereo Components:
Marantz 2325 Stereo Reciever
NAD CD Player 521i
JVC SEA-80 10 Band Graphic Equalizer
Polk Monitor 5Jr
Polk Monitor 7 Series 2
Polk Monitor 10B

[Rev. Hayes]

I would try cleaning the fuse holder contacts. I had a similar crackle coming from my 10's when I first got them. (and judging from your description they where clearly better cared for than your set) A quick scrub with some deoxit or something similar may very well clear up the tweeter trouble.

[Wade Spradley]

Thanks for the reply, I'll have to scrub the fuse holders again with the weak spray deoxit I have, I might not have cleaned it too good the first time. I also read somewhere about the tweeter can be knock out of alignment and realigned by moving its magnet around.

Thanks for the post.

[cristo]

Often the connection between the fuse holder and the fuse is oxidized, but also spray
the rivet that holds the fuse connector to the speaker back and give it a good wiggle.
That's what was noisy on mine.

[Wade Spradley]

I sprayed the rivets down on the one speaker, and wriggled the fuse clips on the rivets. Definitely not too easy to move around. I hope I got some de-oxit in there. I still need to give them a little better work out with some music. Thanks for the suggestions. More updates to come.

[Wade Spradley]

Just another question, this time about the rubber surrounds? What is the proper way to clean them? They seem dusty but I believe the rubber on one of them has oxidized/discolored look to it.

On the tweeter scratchiness, I believe the deoxit did help on the fuse terminals, but I believe I may have to repeat it again. I may need to get some of the stronger concentrated deoxit solution. The spray deoxit I have works pretty well. But the rivets on the fuse holder is a tighter fit, so more wriggling to do.

[Wade Spradley]

Well, I did a little more testing with some Mozart on the speakers with his Requiem Mass, and it was fine until a tweeter on one side dropped out preluded by scratchiness and then the other side did it too. Basically one side dropped out came back on repeated by the other, lasting only a second or three. Of course I have had problems previously of one channel dropping out on my stereo at times, which I know needs another good cleaning with deoxit. Funny thing is most of the time I can work out the intermittent sound with rotating the volume knob with the speakers cutoff on the stereo. This time it caught itself. What fun troubleshooting is. Excuse the rambling.

[Wade Spradley]

Well, after reading through many posts on upgrading the tweeters, I took the plunge and purchased the RDO-194-1's that have been referenced here on the forum. I am pretty sure these 10b's I have will appreciate the new look/sound. The SL1000's (I think that is what is in them do not sound as bright as they should be or detailed, but that could be a problem with the crossover too). Once I get some new crossover parts I will refresh them too. But I started with the tweeters. Once I get ready to get the crossover parts I'll consult the forum, to make sure I do it correctly. I'll rebuild the crossovers and install the tweeter at the same time. After I have collected everything. Polk customer service was very nice to deal with, and answered my stuttering questions with no problems. Thanks Polk.

[Wade Spradley]

Well I finally took a few pictures. My M7s2's are sitting on top of the M10b's for now as a space saving reason, but I like the look. The stands are a set of Wally World specials (mini stools, ported for bass dynamics--just kidding--the holes were already there). You should see the well used M10's waiting for a new set of RDO-194's and eventual crossover upgrade, seems the sonicaps and mills resisters are the way to go. Eventually I will get there. The clear dome faced tweeter is from the M10b, and the black face is the M7s2 tweeter. The M7s2 tweeter dome does not look right, these speakers were bought used in 2003, and one M7 has not sounded as full as the other. May be the crossover and this tweeter. The dome has a ripple on the right inner top edge not sure if it is blown? Any thoughts would be appreciated?

Stereo Components:
Marantz 2325 Stereo Receiver
NAD CD Player 521i
JVC SEA-80 10 Band Graphic Equalizer
Polk Monitor 5Jr (stored)
Polk Monitor 7 Series 2
Polk Monitor 10B
Monster Speaker Cable

[Wade Spradley]

Sorry, took me longer than expected to upload pictures correctly. But here they are for reviewing and comments.

[F1nut]

Just another question, this time about the rubber surrounds? What is the proper way to clean them? They seem dusty but I believe the rubber on one of them has oxidized/discolored look to it.

Windex sprayed onto a soft, lint free cotton cloth. Wipe in a circular motion.

[F1nut]

The SL2500 (black tweeter) looks funky around the edge like it overheated.

[Wade Spradley]

{The SL2500 (black tweeter) looks funky around the edge like it overheated.}

That may be why the speaker itself sounds off, not as much energy. The other tweeter looks normal, and the (2nd) speaker sounds more energetic --like it should--. It looks like another set of tweeters to order unless I can find another SL2500 to replace it. I believe the RDO-198-1's would be the replacements for these from what I have been reading? Definitely a crossover upgrade in the works for them too after I get the M10b's done.

[Wade Spradley]

Well, after reading up on how to identify air leaks on the forum post. I decided to leak test my M10b's and M7s2's. M10b's passed. M7s2's failed. The M7s2's deflated in less than 2 sec's. From what I can tell. I definitely have an air leak around one tweeter face, and I believe the other with the ripple effect on its edge (see picture) is leaking too from around the face of it as well. H'mmm more things to think about?

[Wade Spradley]

Picked up some none ammonia Windex to clean the surrounds. Definitely look better now since they have been cleaned. Also they seem to be sound better the more I use them. They must have been stored somewhere for awhile. Thanks for the Windex tip.

[Wade Spradley]

Well, having received the RDO-198's for the Monitor 7 Series 2, I went ahead an installed them. First I installed one into the bad tweeter cabinet so I could hear the difference between the new and old SL2500 tweeter in the other cabinet. What I found out was they are a direct fit without any modification in the cabinet. They also have the large and small leads on the tweeter just like on the SL2500 they are replacing. So you will not need to worry about accidentally swapping the spade lugs by accident. Also they sound great (smoother) and are not as sharpe/edgy like the SL2500's they have replaced. Of course one of mine was blown, which why they were upgraded. Now to work on breaking them in and eventually upgrading the caps. I hope the upgrade to the crossover improves them even more. This is the first time since I purchased them that they sound more dimensional and correct due to the previous tweeter problem. Now the wait for the RDO-194's for the M10's and M5jr's.

[inspiredsports]

Well, having received the RDO-198's for the Monitor 7 Series 2, I went ahead an installed them. First I installed one into the bad tweeter cabinet so I could hear the difference between the new and old SL2500 tweeter in the other cabinet. What I found out was they are a direct fit without any modification in the cabinet. They also have the large and small leads on the tweeter just like on the SL2500 they are replacing. So you will not need to worry about accidentally swapping the spade lugs by accident. Also they sound great (smoother) and are not as sharpe/edgy like the SL2500's they have replaced. Of course one of mine was blown, which why they were upgraded. Now to work on breaking them in and eventually upgrading the caps. I hope the upgrade to the crossover improves them even more. This is the first time since I purchased them that they sound more dimensional and correct due to the previous tweeter problem. Now the wait for the RDO-194's for the M10's and M5jr's.

Hi Wade,

I know it's a tough question as you never had 2 good SL2500's to listen to, but do you think you would have upgraded to the RDO198-1's if both originals had been good?

[Wade Spradley]

Good question, I probably would have not, the one that was working properly did sound pretty good. I was wondering if the SL2500's were silk domed tweeters, from what I have read in another post, someone stated they were silk domed. Now with the RDO-198's installed, the sound in both of the M7s2's is fuller and balanced. Not as one sided as was previously listened too with the blown SL2500.

Believe it or not I scored another set of M7's this weekend at GoodWill for $27.00. One was missing its MW, and the other was complete. Other than the boxes having some wear and tear to them they look good, not as nice as the M7s2's I have. All the other parts were there, including the SL2000 silver domed tweeters. I pulled the other MW out so I could identify and order the correct MW replacement from Polk, it was dated 1986. I ordered a replacement pair of MW's Monday. Now to cleaned them and prepare them to have the crossovers redone. These I will probably redo the veneer on them later as well. Getting them functional is the first part. I believe these would be the M7C version since they have the polyswitch on the crossover.

Otherwise, I am having fun, I am just surprised to have found the M10's earlier and now these M7C's.

Thanks for the question.

[Wade Spradley]

A new update, I ran across these Polk M7C’s at the same Goodwill I found the M10b’s I have now. These M7C’s look nice but they do have a few cosmetic issues. Seems someone tapped/wrapped a flat head screwdriver or a relative such as a ice pick against the left third of one side of the speakers with small pricks/chips in spots, and of course the bottoms of both are pretty scratched up. Only one speaker was complete. The other was missing the MW6502. Last Monday I ordered a new set of MW from Polk, letting them know I had the MW6502 in these M7’s. I was surprised to get the new MW6502’s (Saturday), I was kinda expecting the MW6503, but I guess they are for the Monitor 7 Series2, rated at 8 ohms. MW6502’s are for the 6 ohm rated speakers (I hope my thinking cap is on right?).

I removed the original MW6502 so I could get an idea of the correct MW, and see the differences between it and the new MW6502’s. The biggest difference is the steel basket frame which has a different stamped pattern. Otherwise they look and feel about the same weight, etc. Also, the gasket on the original MW is flatter than a skunk on the interstate, as you can see the gasket on the new MW which is not compressed (yet). Once I update the crossover and put them back together, I will compare them with the SL2000 tweeter verses the RDO-198’s in the M7S2’s. Before I consider any more mods to them. To give my wallet time to resuscitate.

I also have a question about the correct screws to be used to mount in the Polk Monitors? I found these stainless screws that are almost the same size and shape as the original screws. But I am not sure what I can paint the top of the heads with which would not flake off after awhile. Or can someone recommend other replacements?

I bought a red paint pen so I could mark the hot lead (black) on the new MW, as shown on the original, next to its connector. This way I can keep the original reference when I need to take them apart again.

The progress on the M10b’s are coming along, I am looking to recover the grill frame(s) see picture with the heavier type of speaker grill cloth that Parts Express has, unless there is another grill cloth just as heavy that is available for a more reasonable price? The cheaper stuff which I already have, is too thin, even compared to the original grill cloth.

Well, consistent progress keeps things is perspective. Now to ponder the caps for the crossover?

[Wade Spradley]

Here's another picture of both the new MW6502's.

[Tony M]

Trim that rubber around the screw mounting holes on your new mid-woofers.;)

[helipilotdoug]

Trim that rubber around the screw mounting holes on your new mid-woofers.;)

+1 on that!! I ruined the surround on a new MW a couple of years back because the rubber caught under the screw. 2 years later the rubber surround had a tear in it, so lesson learned!

[Wade Spradley]

Thanks for the input. I have carefully used an exacto knife and tweezers to extract the rubber overhang in the screw holes. The rubber was a little tough to carve out but it is done. It may not be exactly neat cuts but it is removed.

[Wade Spradley]

This is for my rebuild for the goodwill M7c’s I picked up. I already have the replacement midwoofers waiting.

Well, I hope I have not fallen off of the deep end doing this, but after doing some reading and thinking here is the plan.

1. Remove the polyswitches and put a jumper wire in their place.
2. Use two 17uF Sonicaps in parallel in place of the 34uF cap.
3. Use a 12uF Sonicap to replace the 12uF Cap.
4. Use a 2.7ohm mills mra12f resister to replace the 2 ohm resister and
polyswitch resistance. I also noticed on the M7 schematics and even
the M10 schematics that a 2.7 ohm resistor value was used before the
polyswitch was introduced.
5. Use my radio shack silver solder (I did not see the cardas solder on the
sonicap website until after I purchased the caps and received them).
On the next order I will order some.
6. Adequately fit everything on the crossover board.

I figured I would post the game plan and get some thoughts before I proceed. This is my first almost total rebuild on anything electronic. Tweeter replacements will be later.

[Wade Spradley]

I've completed the crossover rebuild. I managed to fit all components onto the old crossover board. See photo's. Other than relocating one of the 34uF caps lead holes, and enlarging them to fit two cap leads per hole, with a dremel, was the only mod I performed to it. Everything else fit in their respective locations.

Now, with the midwoofer, I had to carefully trim the rubber surround a little further around the screw hole so it would not be grabbed by the screws. Something I noticed after installing the first MW. Even though i trimmed the rubber material out of the hole initially it was not enough.

They are currently reassembled, and have been operationally checked. They definitely sound pretty good with the sonic caps installed. Everything seems to have opened up with more detail. Of course I am waiting to hear how well they sound after everything burns in.

I know this is not the prettiest crossover redo, but everything is working as it should.

Right now they are operating with my makeshift home theatre system.