HELP My Polks Are Seized/Frozen

[Schurkey 139]

Could not use the UMBILICAL CORD as Bob Carver would not allow it but I think its not necessary the m500 is mellow and the polks sound just right

You're correct, in that the M500 is not compatible with SDA speakers unless the speakers are new enough to use the AI-1-style isolation transformer.

 

In your case, those speakers ARE NOT compatible with the AI-1, so until you upgrade to a common-ground amplifier, you can't use the interconnect.

 

You are not correct about the Polks sounding "just right"; until you hear them with the interconnect cable, they're just another wonderful-sounding speaker pair.  WITH the interconnect, they image like no other speaker series.

[AndrewJohn 10,836]

[...] Personally I have done hundreds with great success. I've helped out members with theirs, too. These old Polks are susceptible to magnet movement. The bond breaks when jarred and the motor shifts, jamming the v.c. Since they were free previously, I think that's what we have here. I've fixed them before. 

 

Hey Kevin, Any pointers that you might have regarding realigning magnets?  I have four drivers out of a pair of EPI 202's (yes, I like Burhoe designs).  The magnets have slipped and are pinching the voicecoils - and I'm debating replacements vs trying to realign the magnets.

 

Any suggestions on approach to realigning and reglueing the magnets?? 

[fill35U 1,848]

 

 

Hey Kevin, Any pointers that you might have regarding realigning magnets?  I have four drivers out of a pair of EPI 202's (yes, I like Burhoe designs).  The magnets have slipped and are pinching the voicecoils - and I'm debating replacements vs trying to realign the magnets.

 

Any suggestions on approach to realigning and reglueing the magnets?? 

 

Andrew, did you see THIS THREAD about repairing loose/misaligned magnets?

[CT-Seven 764]

 

[CT-Seven 764]

 

 

[CT-Seven 764]

 

 

so until you upgrade to a common-ground amplifier, you can't use the interconnect.

You are not correct about the Polks sounding "just right"; until you hear them with the interconnect cable, they're just another wonderful-sounding speaker pair. WITH the interconnect, they image like no other speaker series.

 

Leave my m500t mkII? Tough what could be better?

 

[AndrewJohn 10,836]

Andrew, did you see THIS THREAD about repairing loose/misaligned magnets? 

 

Thanks Phil. I sometimes fail to find things with Search.   But this time, I did see that. 

 

I'm dreading building the jig, if I can avoid it..., but it's looking to be inevitable.  

 

Burhoe's magnets (two, square, stacked) are pretty simple.  I've got to figure out how the back-plate is attached - it's not clear to me.

 

More studying to do on this...  Replacements from humanspeakers.com are more than I want to put out, at the moment.  

 

(I don't mean to hijack the thread - just saw the "alignment" concept discussion... back to regular discussion ;-) 

[kve777 6,897]

 

 

 

[...] Personally I have done hundreds with great success. I've helped out members with theirs, too. These old Polks are susceptible to magnet movement. The bond breaks when jarred and the motor shifts, jamming the v.c. Since they were free previously, I think that's what we have here. I've fixed them before. 

 

Hey Kevin, Any pointers that you might have regarding realigning magnets?  I have four drivers out of a pair of EPI 202's (yes, I like Burhoe designs).  The magnets have slipped and are pinching the voicecoils - and I'm debating replacements vs trying to realign the magnets.

 

Any suggestions on approach to realigning and reglueing the magnets?? 

1. Index the position/orientation of the magnet to the basket.

2. You need to screw the speaker to a board with a hole in it, like it's in the speaker box, but no sides. You have to get to both the front and the back. I'm going to use one of the Monitor 5 front panels. That will stabilize the basket. 

3. Make some kind of a brace to hold the magnet, attached to the board with the frame, like a piece of PVC a little bigger than the magnet. You can use threaded holes and bolts to adjust or door jamb shims.

4. Pull the magnet off the basket carefully, straight up, so as to not damage the voice coil. Clean off the old glue, etc.

5. Apply high strength epoxy to the surfaces, but make ABSOLUTELY sure none will squeeze into the voice coil area.

6. Put the magnet back carefully, using your alignment marks, use the screws or shims to center the magnet, push the cone in and out to check for rubbing. It's centered when it doesn't rub pushing straight in, and when pushing at an angle it rubs slightly the same in all directions. This is the tricky bit. Knowing that it's centered. I have a good 'feel' for this. some people don't and get it wrong or just get frustrated. Once centered, let it sit for 24 hours. Recheck for rubbing. If it's OK, you are done. If not, crack it open and start again.

 

Yes, there are other ways. You are supposed to pull the cone out. This way works for me. Your mileage may vary. If you can't afford to destroy a driver, don't do it without practice. The most fatal mistake is getting epoxy in the voice coil groove. That will require re-coning. Good Luck!

[Schurkey 139]

 

 

 

so until you upgrade to a common-ground amplifier, you can't use the interconnect.

 

You are not correct about the Polks sounding "just right"; until you hear them with the interconnect cable, they're just another wonderful-sounding speaker pair.  WITH the interconnect, they image like no other speaker series.

 

Leave my m500t mkII? Tough what could be better?

This is a Carver forum, so how about an M1.0 non-inverting version, with appropriate mods?

 

I'm thinking a TFM 42, TFM 45, or TFM 55 would also work.

 

The M1.0 inverting style, and the M500 invert one channel, so they're not compatible.  Any "bridged" or "Balanced" amplifier is also not compatible.

 

I'm using an Aragon 8008BB, but with a 12-guage jumper wire between the negative terminals to provide "true" common-grounding.  The 8008 on it's own has 20 ohms of resistance between the negative terminals, and it makes the 1Bs sound TERRIBLE.

[fill35U 1,848]

@Schurkey- 

 

That Aragon 8008 is a nice amp!  Any idea why they had the resistance between the negative terminals? Are both negative terminals therefore floating with respect to ground?

[Schurkey 139]

Any idea why they had the resistance between the negative terminals? Are both negative terminals therefore floating with respect to ground?

There are a pair of ten-ohm resistors between the negative terminals and chassis ground.  From one terminal, through both resistors, to the other terminal is 20 ohms.  This is not a floating-ground system, it's more like a "semi-common-ground" arrangement.

 

Other manufacturers do the same thing, perhaps with different-value resistors.  Adcom has an amp that has 100 ohm resistor pairs, 200 ohms from one post to the other.  I seem to remember something about Parasound having similar resistors.

 

This is--apparently--some kind of "safety" deal.  I don't claim to understand it.  I just know that my Aragon/Polk system was UN-LISTENABLE before I slapped the jumper wire in place.

[kve777 6,897]

 

 

 

Any idea why they had the resistance between the negative terminals? Are both negative terminals therefore floating with respect to ground?

There are a pair of ten-ohm resistors between the negative terminals and chassis ground.  From one terminal, through both resistors, to the other terminal is 20 ohms.  This is not a floating-ground system, it's more like a "semi-common-ground" arrangement.

 

Other manufacturers do the same thing, perhaps with different-value resistors.  Adcom has an amp that has 100 ohm resistor pairs, 200 ohms from one post to the other.  I seem to remember something about Parasound having similar resistors.

 

This is--apparently--some kind of "safety" deal.  I don't claim to understand it.  I just know that my Aragon/Polk system was UN-LISTENABLE before I slapped the jumper wire in place.

There is an old adage "If you don't know what a part is for, it's probably for noise reduction" that may work here. The resistors could be for improving noise floor by isolating output from chassis and channel separation by putting resistance between otherwise common grounds. Is there any noise floor difference with the jumper? Any cross-channel interference? Just a thought.

[fill35U 1,848]

I did recall reading that the 8008 is DC-coupled all the way through. Perhaps the resistors are there to mitigate current in case of a DC offset and fault to the chassis or ground? 

 

Edit: Since the 8008BB is a dual monoblock, they might have wanted to limit a fault in one side from harming the other?

[Daddyjt 9,846]

 

 

 

 

so until you upgrade to a common-ground amplifier, you can't use the interconnect.

You are not correct about the Polks sounding "just right"; until you hear them with the interconnect cable, they're just another wonderful-sounding speaker pair. WITH the interconnect, they image like no other speaker series.

 

Leave my m500t mkII? Tough what could be better?

This is a Carver forum, so how about an M1.0 non-inverting version, with appropriate mods?

I'm thinking a TFM 42, TFM 45, or TFM 55 would also work.

The M1.0 inverting style, and the M500 invert one channel, so they're not compatible. Any "bridged" or "Balanced" amplifier is also not compatible.

I'm using an Aragon 8008BB, but with a 12-guage jumper wire between the negative terminals to provide "true" common-grounding. The 8008 on it's own has 20 ohms of resistance between the negative terminals, and it makes the 1Bs sound TERRIBLE.

 

While I hardly think of it as an "upgrade", I have a freshly recapped 55x that's just collecting dust - if you want to switch it out, I'll trade you straight across for the 500t mkII, Bryan...

 

You decide - no pressure;-)

 

 

 

[CT-Seven 764]

While I hardly think of it as an "upgrade", I have a freshly recapped 55x that's just collecting dust - if you want to switch it out, I'll trade you straight across for the 500t mkII, Bryan...

You decide - no pressure;-)

 

Decisions,

Decisions,

Decisions....

In the meantime here is Alexis

 

I am taunting the Idea of the TFM-55X but I am an asthetics kind of guy and I don't seem to like the look of the TFM series (don't get me wrong they are great amps I just don't like the looks of em)

 

I will stay put and enjoy my music even thou I don't have the "SDA MAGIC"

 

 

Watched HOMEFRONT on BD last night and I think everything sounded ok

 

Yet I still have a feeling that I want to try the SDA Magic... might have to borrow an AMP locally (insert local friends name here) 

[CT-Seven 764]

So far so good, tested with the M500t and I do get sound from everybody. All 8 drivers and 4 tweeters.

 

Called Yamaha and they said the RX-V2700 is not common ground so that test is out the door.

 

Both the M500t and the SRS2 have the wife seal of aproval

So for now this will stay put

 

ON A SIDE NOTE:

my adcom ACE-515 slides back when I flip the power switch

I know is a light unit what can I do to fix him that way he does not slide?

[zumbini 6,153]

....my adcom ACE-515 slides back when I flip the power switch

I know is a light unit what can I do to fix him that way he does not slide?

 

• put something heavy on top of it
• bolt it to the rack
• install plastic L-brackets behind the unit as stops
• add double-sided tape or velcro to the feet 

 

[CT-Seven 764]

The footprint is too small to stack anything, its sitting on top of the sony DVP-S7000 lets see if I can do the brackets

[fill35U 1,848]

ON A SIDE NOTE:

my adcom ACE-515 slides back when I flip the power switch

I know is a light unit what can I do to fix him that way he does not slide?

 

• Replace the power switch
• Plug her into a switched outlet/sequencer 

[Schurkey 139]

Called Yamaha and they said the RX-V2700 is not common ground so that test is out the door.

Depends on WHY it's not common-ground.

 

If one channel is inverted, or if it's a "bridged" or "balanced" design, there's nothing you can do.   If it's not common-ground because of a couple of resistors used to isolate the chassis ground from the negative terminals (very common design practice) all you need is a foot of speaker wire to tie the negative terminals together.

 

Can you get a schematic?  Have you measured the resistance between the negative terminals?

[kve777 6,897]

 

ON A SIDE NOTE:

my adcom ACE-515 slides back when I flip the power switch

I know is a light unit what can I do to fix him that way he does not slide?

 

I like double sided 'camper' tape thick foam, sticky on both sides.