Is this driver a MW6503? If not what is it?

MrGeology

Hello everyone, am new to this forum. Tried searching for ways to identify this driver but came up with nothing. It was in a Monitor M4.6 but DATS reads it as an 8 ohm driver, and it looks different than the other M4.6 driver I have.

Hoping it is a 6503 so I can re-surround it and use it in one of my Monitor 7B's.

Someone used super glue (or worse) to glue a ring to the outside of the speaker which caused the rubber to crack. They also marked it POLK AUDIO over the factory ink. I marked it 8 ohm and set it aside months ago but now need a 6503. Here are some pics I hope will help.

Thanks for the help.

xschop

If the voice coil rubs easily, it's a 6500. The 6500 is the only driver I've seen to date with the swaged pole-piece like that. May be a 6501, but haven't seen pole-piece pics here to distinguish.

MrGeology

Thanks to some good research by @Gardenstater it has been revealed that this driver was not made by Polk but by GEFCO Mfg. Co and is therefore not a MW6500.
More details can be found on this thread
https://forum.polkaudio.com/discussion/198339/6500-anomaly

pitdogg2

Good luck on that surround job afaik there are no proper surround replacements. If it measures 8 ohm it could be one of several of the older Polk drivers. It also could be about fried and the value has shifted.

1 Driver Type Q BL Compliance DC Resistance Fs

3 MW 6501 1.47 5.96 N 3.25 E - 3N/M 7.75 Ohms 31 Hertz

4 MW 6502 1.97 5.16 N 1.47 E - 3N/M 3.52 Ohms 44 Hertz

5 MW 6503 1.82 5.24 N 3.55 E - 3N/M 6.54 Ohms 29 Hertz

6 MW 6509 2.1 4.57 N 3.54 E - 3N/M 8.97 Ohms 30 Hertz

7 MW 6510 1.39 6.32 N 3.41 E - 3N/M 6.57 Ohms 31 Hertz

8 MW 6511 1.405 4.34 N 3.496 E - 3N/M 3.13 Ohms 29 Hertz

9 MW 6512 1.905 4.99 N 1.588 E - 3N/M 3.466 Ohms 40 Hertz

MW 6600 is also 8 ohm

Gardenstater

The 7B used MW6500. Close to the MW6503 but a bit different:

Driver: MW 6500 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 31.0000 Hz (Free air resonance)
Vas: 2.6486 ft^3 (Compliance volume)
Qts: 0.2190 Total Q
Qms: 1.3000 Mechanical Q
Qes: 0.2640 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 6.5000 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6501 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 31.0000 Hz (Free air resonance)
Vas: 2.7545 ft^3 (Compliance volume)
Qts: 0.2790 Total Q
Qms: 1.4700 Mechanical Q
Qes: 0.3440 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 7.7500 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6502 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 44.0000 Hz (Free air resonance)
Vas: 1.2360 ft^3 (Compliance volume)
Qts: 0.2790 Total Q
Qms: 1.9700 Mechanical Q
Qes: 0.3250 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 3.5200 ohms (DC resistance)
Znom: 4.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6503 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 29.8600 Hz (Free air resonance)
Vas: 3.0017 ft^3 (Compliance volume)
Qts: 0.3100 Total Q
Qms: 1.7680 Mechanical Q
Qes: 0.3760 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 6.5400 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power

Driver: MW 6517
BrandL Polk Audio
* Size / Type = 6.50" treater paper cone woofer
* SPL = 91 db @ 1w/1m
* Wattage = 125 Watts RMS / 250 Watts Peak
* Treated cone woofer, rubber surround
* Response = 40 Hz. to 10 kHz.
* Weight = Right a 4 pound ea.
* Magnet = UnShielded
* VC = 1" ( 25 mm)
* Ohms = 4 ohms
* f(s) - 55 Hz.
* Q(ms) - 7.261
* V(as) - 14.60 liters ( 0.516 cf. )
* n(0) - 5.02%
* M(ms) - 18.38 grams
* R(e) - 1.86 Ohms
* Q(es) - 0.048
* SPL - 92 dB @ 1W/1m
* C(ms) - 0.44 mm/N
* Z(max) - 281.50 Ohms
* Q(ts) - 0.048
* L(e) - 31.08 mH

westmassguy

MrGeology wrote: »

Hello everyone, am new to this forum. Tried searching for ways to identify this driver but came up with nothing. It was in a Monitor M4.6 but DATS reads it as an 8 ohm driver, and it looks different than the other M4.6 driver I have.

Hoping it is a 6503 so I can re-surround it and use it in one of my Monitor 7B's.

Someone used super glue (or worse) to glue a ring to the outside of the speaker which caused the rubber to crack. They also marked it POLK AUDIO over the factory ink. I marked it 8 ohm and set it aside months ago but now need a 6503. Here are some pics I hope will help.

Thanks for the help.

It has a treated felt dust cap. Possibly MW6501 or 6600X. The Monitor 4.6 should have a 4 ohm MW6502 woofer.

Gardenstater

My MW6500s say SR142/17 on the surround, so that doesn't match what you have on yours.

Toolfan66

That driver is what ever you want it to be, take some acetone, wipe off the marker that is on it, and label it what you want it to be, problem solved..

Gardenstater

You can weight the dust cap with some pink chewing gum to get the compliance in line with the 6500



No not really please do not try this

MrGeology

Thank you for all the helpful replies!

I ran the driver through DATS again late last night.

The Re in DATS (DC resistance) is 6.48 ohm, Crossover Pro calculated nominal impedance at 7.68.

Fs came in at 112Hz which I suspect is due to the brittle edge around the rubber where the super glue was applied making it difficult to move at low frequencies.

Vas measured .217 (liters) but again with damaged surround probably inaccurate so not much help there either.

This is all from memory, when I get back to my DATS workstation will look at the Q numbers.

Meantime will be searching for a 6500 replacement as replacing the butyl surround does not look fun or promising.

MrGeology

Cheers to xschop, the driver is in fact an MW6500.
Someone had apparently replaced the surround with one that was much too thick and not pliable enough. They even put a felt dust cover on top of the original.
I purchased some new surrounds from midwest. They have the same heft, thickness and pliability as the originals. Installed a new surround on it last night and the DATS numbers came out matching an MW6500 +/- 5% (once I got a good run on it, see below).
Unfortunately when I put it on the tone generator to do the surround I noticed a slight buzzing sound that isn't normally there with other drivers.
Hoping it would cure itself with a surround to stabilize it I went ahead and glued/centered it (what a PITA, these things have almost no room for error!).
Just got done testing it in the cabinet and it definitely has a some voice coil damage. Occasionally it sounds good for about a minute or so, but then sounds almost like static in the signal. It clears up real nice once it gets about 80 watts to it, but at normal listening levels it sounds pretty bad.
Looks like the hunt continues for a good 6500.

MrGeology

Cheers to xschop, the driver is in fact an MW6500.
Someone had apparently replaced the surround with one that was too thick and not pliable enough. They even glued a felt dust cover over the original.
Purchased a set of surrounds from midwest. They have the same heft, thickness and pliability as the originals.
Installed a new surround on it last night and the DATS numbers this morning came out matching an MW6500 +/- 5% (once I got a good run on it, see below).
Unfortunately when I hooked it up to the tone generator to do the surround I noticed a weird buzzing noise that isn't normally there with other drivers.
Hoping it would cure itself with a surround to stabilize it I went ahead and glued/centered it (what a PITA, these things have almost no room for error!).
Just got done testing it in the cabinet. Occasionally it sounds good for about a minute or so at normal listening levels, but then sounds almost like static coming through the mid driver. It clears up real nice once it gets about 80 watts, but at normal listening levels it sounds pretty bad. Guessing the voice coil was damaged before I got it.
Looks like the hunt is still on for a good 6500.

xschop

The VC is probably not damaged, just suspension is off/saggy. If you haven't glued the magnet and pole piece, you can break them apart and get to the base plate to clearance it. You'd carefully stuff a rag between the frame and back side of cone, bringing coil as far forward as possible, then use a dremel drum sander to clearance the base plate ID by extra .008" IIRC that's the value I clearanced one at by lathe. Thinking back, I'd use a Dremel drum as it would be alot simpler.

Check pics here about mid-page...

https://forum.polkaudio.com/discussion/195928/forum-member-mw-magnet-repair-tool-set/p5

MrGeology

When I first got the driver I didn't hear any coil rub so it got Loctite Power Grabbed to the frame. Didn't do anything to the pole piece. Could probably cut the power grab enough to make the magnet removable.
The question is, how would I go about putting the magnet back on after the mod is done? Didn't think it would be possible without removing the VC.

Easy Runnin

Try rotating the driver in the cabinet at 90 degree increments. You might get lucky.

Gardenstater

Both my original equipment MW6500s have cocked voice coils that just barely rub on the framepiece. I haven't fixed it yet and I have other replacements that are working beautifully.

MrGeology

xschop wrote: »

The VC is probably not damaged, just suspension is off/saggy. If you haven't glued the magnet and pole piece, you can break them apart and get to the base plate to clearance it. You'd carefully stuff a rag between the frame and back side of cone, bringing coil as far forward as possible, then use a dremel drum sander to clearance the base plate ID by extra .008" IIRC that's the value I clearanced one at by lathe. Thinking back, I'd use a Dremel drum as it would be alot simpler.

Check pics here about mid-page...

https://forum.polkaudio.com/discussion/195928/forum-member-mw-magnet-repair-tool-set/p5

After looking through your posted pics and description I realize the mistake in asking how to put the magnet back on.
Now that I have a vague understanding of the drivers build it seems that I only glued the base plate to the driver frame.
Upon inspection the magnet on my driver is not centered on the base plate, and the pole piece plate is off center to both the magnet and base plate (or so it appears). Guessing this has led to the problems it is having.
From your pics and description it looks like I will need to have my machinist friend fab some pieces to do the disassembly and re-assembly of the driver. Given his current workload this may be several months in the future.
He has offered to bore the frame on his lathe after viewing your posted pics, says it will be easy, but again will be several months out. If I am mistaken about the fab work needed please let me know.
Thanks again for your valued input.

MrGeology

Easy Runnin wrote: »

Try rotating the driver in the cabinet at 90 degree increments. You might get lucky.

Tried this, no joy. Thanks.

xschop

If you just need the centering jig, chime into the thread and put your name on the list. I personally would cut the dust cap off the 6500 to physically see the centering of pole piece to VC gap because the 6500 has so little clearance even when dead centered.