Monitor 10's only the tweeter works well!

1Surfrider

I got some 10's from a guy. I thought they sounded very thin, but they were cheap.

I took off the front of one of them, pushed on the bass speaker, hoping it would move the 6.5" speakers, nope. Checked both speakers, weight on the back is secure, I made sure they are wired in phase.

I pulled one of the 6.5's, played some Living Color and held the speaker, it was putting out sound, but still very thin, no bass at all.

Sooooo, I'm not real sure what to do. Anyone have a suggestion?

tonyp063

Frozen drivers most likely. Magnet shift.

You can get new drivers direct from Polk. They are about $50 each.
You can try & find some on the well-known auction site. They're not going to be much cheaper there & you risk magnet shift if the seller doesn't properly package them & anchor the magnets with powergrab ,etc.

And then you'll be looking at the cost to refresh the crossover.

Were it me, I'd cut my losses.

1Surfrider

I'm thinking you may be correct...would "any" 6.5 speaker work?

Nhpenn

You might check to see if the rubber surounds on any of the drives/passive radiator have split. I recently bought a pair of monitor 5s without realizing the surounds where dry rotted, if that is the case you should be able to buy a refoaming kit online, or possibly repair them yourself.

tonyp063

1Surfrider wrote: »

I'm thinking you may be correct...would "any" 6.5 speaker work?

No.
Impedance matching. Voicing. Speaker physical parameters. etc. all come into the equation.
Those particular M10s came with the MW-6500 mid-woofer. I believe the replacement is the MW-6502.
I will be corrected if I got the model numbers wrong.

If you stick just any 6.5" in there, chances are greater than not that it'll sound like dung.

1Surfrider

When I push on the woofer, the midrange speakers don't move, if that's a symptom.

Viking64

1Surfrider wrote: »

When I push on the woofer, the midrange speakers don't move, if that's a symptom.

Either the drivers are frozen or there is a major air leak in the cabinet. Most likely the former, I would think.

1Surfrider

That's what I was thinking. Not sure if it'd be worth it to put new speakers in.
I was hoping it was something easy and cheap.

westmassguy

1Surfrider wrote: »

When I push on the woofer, the midrange speakers don't move, if that's a symptom.

The 10 doesn't have a "woofer" and midranges. The 10" "woofer" is a passive radiator. The 6.5" midranges are the woofers. They're most likely frozen due to magnet shift. There is a member here who repairs them on an exchange basis, do a search. The MW6500s, if that's what's most likely in there, are 8 ohm wired in parallel. The MW6502 is 4 ohm, and not the correct replacement. I believe Polk carries the MW6503 as the replacement. FleaBay should have salvaged MW6500s and 6503s too. As mentioned, make sure the seller wraps them in plenty of bubble-wrap and padding, otherwise you'll end up with more paperweights.

codycatalist

Nhpenn wrote: »

You might check to see if the rubber surounds on any of the drives/passive radiator have split. I recently bought a pair of monitor 5s without realizing the surounds where dry rotted, if that is the case you should be able to buy a refoaming kit online, or possibly repair them yourself.

No kits for Polks.

FestYboy

westmassguy wrote: »

1Surfrider wrote: »

When I push on the woofer, the midrange speakers don't move, if that's a symptom.

The 10 doesn't have a "woofer" and midranges. The 10" "woofer" is a passive radiator. The 6.5" midranges are the woofers. They're most likely frozen due to magnet shift. There are 2 members here who repair them on an exchange basis, do a search. The MW6500s, if that's what's most likely in there, are 8 ohm wired in parallel. The MW6502 is 4 ohm, and not the correct replacement. I believe Polk carries the MW6503 as the replacement. FleaBay should have salvaged MW6500s and 6503s too. As mentioned, make sure the seller wraps them in plenty of bubble-wrap and padding, otherwise you'll end up with more paperweights.

Fixed

Nhpenn

codycatalist wrote: »

Nhpenn wrote: »

You might check to see if the rubber surounds on any of the drives/passive radiator have split. I recently bought a pair of monitor 5s without realizing the surounds where dry rotted, if that is the case you should be able to buy a refoaming kit online, or possibly repair them yourself.

No kits for Polks.

Good to know

tonyp063

I pulled one of the 6.5's, played some Living Color and held the speaker, it was putting out sound, but still very thin, no bass at all.

This is what makes me think frozen drivers & not an air leak

The MW6500s, if that's what's most likely in there, are 8 ohm wired in parallel. The MW6502 is 4 ohm, and not the correct replacement. I believe Polk carries the MW6503 as the replacement. FleaBay should have salvaged MW6500s and 6503s too.

Thanks David. I was not positive on the model numbers. Went from memory.
Bad choice there

codycatalist

Nhpenn wrote: »

codycatalist wrote: »

Nhpenn wrote: »

You might check to see if the rubber surounds on any of the drives/passive radiator have split. I recently bought a pair of monitor 5s without realizing the surounds where dry rotted, if that is the case you should be able to buy a refoaming kit online, or possibly repair them yourself.

No kits for Polks.

Good to know

I wish they did. I'm sure I and others agree it would have saved us time and money.

westmassguy

FestYboy wrote: »

westmassguy wrote: »

1Surfrider wrote: »

When I push on the woofer, the midrange speakers don't move, if that's a symptom.

The 10 doesn't have a "woofer" and midranges. The 10" "woofer" is a passive radiator. The 6.5" midranges are the woofers. They're most likely frozen due to magnet shift. There are 2 members here who repair them on an exchange basis, do a search. The MW6500s, if that's what's most likely in there, are 8 ohm wired in parallel. The MW6502 is 4 ohm, and not the correct replacement. I believe Polk carries the MW6503 as the replacement. FleaBay should have salvaged MW6500s and 6503s too. As mentioned, make sure the seller wraps them in plenty of bubble-wrap and padding, otherwise you'll end up with more paperweights.

Fixed

Good to know

westmassguy

tonyp063 wrote: »

I pulled one of the 6.5's, played some Living Color and held the speaker, it was putting out sound, but still very thin, no bass at all.

This is what makes me think frozen drivers & not an air leak

The MW6500s, if that's what's most likely in there, are 8 ohm wired in parallel. The MW6502 is 4 ohm, and not the correct replacement. I believe Polk carries the MW6503 as the replacement. FleaBay should have salvaged MW6500s and 6503s too.

Thanks David. I was not positive on the model numbers. Went from memory.
Bad choice there

No worries.

delkal

It is hard to believe that all 4 drivers on two separate speakers are frozen. Do the speaker bodies have large dents and major damage like they were dropped?

Push each driver (not the passive) gently trying to keep the pressure centered. They should easily move in and out and not be frozen or give a crunching noise.

Also, if you were just holding a driver in your hand while playing music it should sound thin. You need an enclosure to get the bass.

1Surfrider

I'll check the other speaker to see if the mid are frozen. I played music for a while, I thought maybe that would loosen them up.

delkal

1Surfrider wrote: »

I'll check the other speaker to see if the mid are frozen. I played music for a while, I thought maybe that would loosen them up.

If you are hearing music your drivers are not locked up. And if the music doesn't sound all scratchy and distorted from the coils rubbing your magnets are fine.

Push in on the passive quickly and hold it. Do the drivers move even a small amount then immediately go back in? Sounds more like an air leak. Do you have thin gaskets on all of the speakers and the crossover?

jdjohn

I have a couple pair of Monitor 10, and when I bought the second pair, all four mid drivers were seized. Luckily I got them cheap, but probably not cheap enough They would produce sound, but I did not turn the volume up at all due to the seizing. As mentioned, if you gently press on the mid cones, and they don't move, well...they are seized. Sometimes only the pole plate has moved, sometimes the magnet, sometimes both. Those cones should move in-and-out freely.

I fixed all four of them on the pair I got (actually did an MW-6503 last week). A jig is required to hold the pole plate in place after gluing, but it's not too difficult to make. If you want to tackle it yourself, I'll bet we can get you through it. Working with strong magnets and steel can be a little unnerving while pulling apart and putting back together with the sudden movements, but it does get your adrenaline pumping

TennMan

Do a battery test on them and see if the drivers are moving as they should. AA 1.5 volt battery momentarily connected across the terminals on the back of the speaker should move both drivers forward.

1Surfrider

They're putting out sound but they're not moving a lot of air. The woofer "speaker" doesn't move at all, although it seems loose enough. When you press on the woofer the two mid speakers don't move a lick.

Faustin

If you gently push on the 6.5" drivers (see picture) they should freely move in and back out. If they do not move in and out they are "frozen". The magnets have shifted. If they do move freely and you push on the passive radiator (not a woofer) and hold it in and they do not move out and stay for 5 - 10 seconds, then you have a air leak somewhere. Those speakers are designed to be pretty much air tight. There are gaskets on the drivers to make a nice air tight seal as well as the binding post cup. It is possible some of the gaskets are missing or screws are loose or stripped. Another possible air leak problem could be the cabinet itself. Most people will re-seal the inside of the cabinet with a water based Power Grab caulk.

jdjohn

The mids are seized/frozen because the magnets and/or back poleplates have shifted, and now the voice coil is pinched - can't move. This happens due to the problematic glue that Polk used to hold those pieces together. The glue is a known weakness with these drivers, and after enough hard knocks, the glue gives way, and the magnet or steel pieces shift; the tube of the voicecoil is situated between the pole and the magnet, so when the shift occurs, the voice coil gets pinched/stuck.

Here is a pic with the dustcap removed, and you can see how the pole piece has shifted inside the tube of the voicecoil, attracted by the inside ring of the magnet.
The voicecoil is now stuck/seized/frozen in place.

Sure, the other spots/gaps around the pole can vibrate a *little* - maybe enough to create just a wee bit of sound - but clearly the driver cannot operate as it should. The cone should move in-and-out freely, with clearance all the way around the pole, but in this case it can't due to the voice coil being pinched.

Here are back layers of the driver taken apart.

These layers were held together by glue. The magnet is glued to the plate on the rear of the basket/frame, and the poleplate is glued to the back of the magnet, with the pole itself slipping inside the voicecoil tube, which you can see sticking out of the back of the basket/frame plate. Maybe this will help you visualize what has happened - the poleplate gives way, slides just a few millimeters as it is attracted to the inside of the magnet ring, pinching the voicecoil tube, and essentially rendering the driver inoperable.

To fix it, the magnet and poleplate have to be glued back together with better glue, but a homemade jig has to be used to hold the poleplate precisely in place while the glue cures. The jig allows you to set proper clearance around the pole inside the voicecoil tube.

1Surfrider

Thanks for this, I know what I have to do, I think...

FestYboy

If you have any questions, don't hesitate, I'm on here all the time.

ZVH

Thanks jdjohn, very helpful. I am restoring a pair of SDA CRS and would like a bit more information on the jig you mentioned as well as a better glue please.

FestYboy

Red Loctite is your go to glue. There are other options, but the red is the most widely used. Search my username, I posted a few pics and a part number of the bits that I cobbled together to make a jig.

ZVH

Thanks for the assist @FestYboy. I built a jig with the assistance of another electrical engineer, retired Altec Lansing guy. We replaced the magnets and glued with Locktite 271 red.