Monitor 7 new to me
Options
hobbyist49
Posts: 19
Hi,
After getting a lot of excellent help from you guys about recapping my Monitor 10 Series 2s, I ended up running across a set of Monitor 7s for $150 (hopefully a good price!). They appear to be from around 1986 and appear to have the maligned S2000 tweeters. And I think the magnets have started shifting on the drivers. On the plus side, they have real wood veneer. I wonder if someone could please tell me, from looking at the pics, are the drivers worth saving if I glue them? I haven't even played them yet for fear of them locking up or whatever. Thanks again!
Joel
After getting a lot of excellent help from you guys about recapping my Monitor 10 Series 2s, I ended up running across a set of Monitor 7s for $150 (hopefully a good price!). They appear to be from around 1986 and appear to have the maligned S2000 tweeters. And I think the magnets have started shifting on the drivers. On the plus side, they have real wood veneer. I wonder if someone could please tell me, from looking at the pics, are the drivers worth saving if I glue them? I haven't even played them yet for fear of them locking up or whatever. Thanks again!
Joel
Comments
-
Why do you think the magnets have started shifting? Have you done the test with your fingers evenly placed just around the dust cap and carefully pushed and listened/felt for voice coil rubbing? No way to tell by just looking. If they pass the test I'd definitely glue them up before using them very much. The SL2000s can always be replaced with the RDO-194s if you wish.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I forgot to mention, the cones move in and out freely without scratching noise.
-
Well then you are in luck and I'd say they have probably not started to shift
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I was (maybe incorrectly) assuming that because the magnets are off center. Thanks for the reassurance!
-
Although FAR from ideal, I believe the magnet can actually be about 1/8" off center before it will start to rub on the voice coil, due to the fairly large hole in magnet (approx. 1.3"?). Ideally everything should be concentric (base plate pole piece, voice coil, magnet, pole piece). I don't know how sloppy Polk was with centering the magnets.
How much off center does your magnet appear to be relative to ?:
1) Base plate pole piece
2) Pole pieceGeorge / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I think it's a bit more than 1/8". These pics aren't very good, but might be illustrative.
-
Yeah those magnets are pretty off center relative to the pole piece. Is that mirrored on the base plate pole piece and minimums and maximums are in same polar locations? Anyway, the offset from center = (max - min)/2. It's hard for me to tell from your pics and that ruler doesn't even begin at 0 lol.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I don't know if this means:
1) Your magnets have slipped
2) Polk was just sloppy at times with centering of the magnets
3) They did this deliberately to compensate for assymetrical magnetic flux density of a particular magnet.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Yea, sorry that pic is upside down :-). Yes, the off-center is mirrored on the top/front plate and back plate (not sure if I'm using the right terminology). I got some two-part loctite epoxy, so will glue them up today. Is it sufficient to glue at various points along the perimeter of where the top plate meets the magnet, or do I also need to hit the underside, where the magnet contacts the back plate? Again, thank you for all your advice.
-
I think if you are using epoxy you can just do various points, rather than the entire circumference. You do definitely have to do where the magnet contacts the base plate pole piece too, even though it is a bit harder to get to. If you don't the pole piece + magnet could still slip relative to the base plate pole piece and you've got a pinched voice coil.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
All the MW’s in my speakers look like that to varying degrees and they function just fine.2 channel: Anthem 225 Integrated amp; Parasound Ztuner; TechnicsTT SL1350; Vincent PHO-8 phono pre; Marantz CD6005 spinner; Polk SDA2BTL's; LAT International speaker cables, ZU Mission IC's and power cables all into a PS Audio Dectet Power center.
Other; M10 series II, M7C's, Hafler XL600 amp, RB-980BX, Parasound HCA-1500 amp , P5 preamp, all in storage. All vintage Polk have had crossover rebuilds and tweeter upgrades.
The best way to predict the future is to invent it.
It is imperative that we recognize that an opinion is not a fact.
Imagine making politics your entire personality. -
Thanks to you both!
-
Got them glued, used JB Weld Steel Stick...that stuff isn't as easy to work with as I thought it would be :-). Also ordered the RD0-194s. Polk still has them and still honors the Club Polk discount.
-
Gardenstater wrote: »I don't know if this means:
They did this deliberately to compensate for assymetrical magnetic flux density of a particular magnet.
Have you guys ever seen speaker drivers built ?
You do know while being built they are just ferrite cores non magnetic
They are not magnetized until after the drivers are glued up and dried.
So they wouldn't be compensating for any sort of magnetic flux
-
No I actually haven't. That would make it a lot easier to do the glue up. So now we're back to the question of why his magnets are so out of concentricity with his pole pieces if there has been no slippage, and how if there has been slippage, is he not experiencing voice coil scraping. Seems like it would require tremendous luck for that to have occurred.
The only thing that makes sense(?) is that Polk glued them up like that or someone else manually moved the pole piece after the magnet slipped and managed to get it right and maybe put some loctite or super glue or something on it.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Since the Steel Stick has a cure time of 60 mins, I went ahead and fired them up just now for the first time, and they sound fantastic. I guess if they don't move any more, I should be OK :-). Thanks again for the help. Next on the list will be caps, at some point.
-
Many magnet slips do not readily appear any different than they did before slipping.
-
Many magnet slips do not readily appear any different than they did before slipping.
So when a slipping magnet slips, how do you know it's slipping, or is that a slippery slipping question going down a slippery slope2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a -
2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a -
-
Would make a great avatar.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
