Monitor 5 troubleshooting

The Baumer

Greetings All,
I just picked up a pair of M5's. One speaker works well. The other produces a faint "tinny" sounding reproduction of the music. I've eliminated source components, interconnects and cables as the issue.

The speaker in question has a series of 3 small holes arranged in a horizontal row above the binding posts on the crossover plate. Am I missing a fuse and bracket and could this be the problem? Are these pieces available at Radio Shack? Oh, and the functioning speaker does NOT have the holes on the crossover plate. Is this unusual? Perhaps not a matched pair of speakers or crossovers?

Thanks in advance for your help!
Marcus

george daniel

If they are the early version of the Monitor 5's,,it sounds like you may be missing the fuse/bracket,,what does the other speaker look like/have. Do the tweeters appear to have a "dimple" or pin hole in the center? Good luck.Let us know how it turns out.

The Baumer

Thanks George,
I just checked the tweeters and both speakers have the SL2000 version. So, should my next step be to obtain and install a fuse/bracket on the questionable speaker?

comfortablycurt

It sounds like you have a mismatched pair.

One speaker has the 3 small holes over the binding posts...some of the Monitor series had this. It's from the mounting spot where the fuses would have went, except they switched over to polyswitches for the tweeter protection. I'm guessing they just had an excess stock of the terminal cups, and used them up before switching over to the new ones.

The other speaker doesn't have the holes? Does it have a fuse on the back? I'm guessing it doesn't...

Are the cabinets air tight? Push in on the passive radiator and hold it down, the midwoofer should pop out, and stay extended for a few seconds, then start moving back in real slowly.

If the cabinets aren't air tight, it could possibly be contributing to the tinny sound.

By tinny, do you mean lack of bass output?

By the way, welcome to Club Polk.:)

george daniel

I'm assuming the other speaker is fused? If so,, yep, that may be what you need,, you may want to swap drivers from the suspect one to the good one,just to rule them out(tweeter and mid)

Polkersince85

Sounds like you are only hearing the tweeter. Check the wire connections to the mid range driver. Remove the driver from the front.

The Baumer

Thanks folks!
Comfortablycurt- No, the other (functional) speaker doesn't have the holes or external fuse. The suspect speaker does not pass the air tight test. The speaker cabinet is in good condition and the rubber surrounds for the drivers are supple/no cracks. Yes, by "tinny" I mean lack of bass output. Thanks for the welcome.

George & Polkersince85 - I'll pull the drivers to check the connections and swap to test.

comfortablycurt

The Baumer wrote: »

Thanks folks!
Comfortablycurt- No, the other (functional) speaker doesn't have the holes or external fuse. The suspect speaker does not pass the air tight test. The speaker cabinet is in good condition and the rubber surrounds for the drivers are supple/no cracks. Yes, by "tinny" I mean lack of bass output. Thanks for the welcome.

George & Polkersince85 - I'll pull the drivers to check the connections and swap to test.

I suspected it could be something like that. You did hold the PR in correct? Push it in and hold it. If the MW's move back in quickly...you have air leakage.

That would definitely be contributing to the lack of bass output. Because of the design of the speakers, the cabinets need to be air tight. Check all of the screws on the drivers and the crossover. Make sure they're tight, but don't overtighten them, or you could strip out the screw holes in the baffle.

Are you getting any sound at all out of the mid-woofer in the suspect speaker?

What are the serial numbers? The mismatched terminal cups are a pretty good indicator that you may have a mismatched pair. This might not be to critical though, as long as they're the same drivers/crossovers.

The Baumer

I held the PR in correctly and there was no movement of the MW at all. I pulled the MW and tested it in the functioning speaker. It doesn't work at all. So, it seems the MW is bad. Is it possible to fix or do I need to look for a replacement?

There are a couple of 6502 drivers for a M7c on ebay now. Would these fit? Oh, the serial #s are 78363 & 74841 so this confirms the mismatched pair?

comfortablycurt

Sounds like the MW's seized up. You'd need to replace it. Not positive on the part number of the driver...does it say 6502 on the back of the mid-woofer you pulled? I think that's the correct one, but check the back of the MW just in case. If you're replacing the one, you may want to go ahead and replace both of them. The drivers and surrounds wear out over time, so a new one and an old one together might not sound properly balanced.

Don't quote me on it, but the serial numbers being that far apart, plus the different terminal cups, leads me to believe they're a mismatched pair. Check the crossovers and see if they're the same. As long as they're the same, it shouldn't really affect the sound. Polk is infamous for having several "in-between" models during the introduction of new models.

The Baumer

The MW's are labeled 6502 so I'm going to try for the replacements listed on ebay. Does Polk still manufacture and sell new MW6502 drivers? If so, how much and who do I talk to?

The crossovers are not the same.

comfortablycurt

I believe Polk still has the 6502's in stock. Call the customer service number at the top of this page and tell them what you need. Mention that you're a Club Polk member for a discount.;)

Any chance of some pictures of the crossovers?

The Baumer

Thanks! It's good to know about the discount. I won the 6502's on ebay so will try those first. I realize that these drivers have a limited lifespan but I'm willing to chance it with the used MWs as mine is a budget system.

Photos of the crossovers attached.

The Baumer

Jpg's

comfortablycurt

Anyone correct me if I'm wrong on any of this.

The first one there looks like one of the newer generation 5B crossovers, due to the polyswitch in the tweeter protection circuit.

The second one almost looks like a Monitor 5 Series II crossover. The vertically mounted caps/resistor leads me to believe that. That does look significantly different than the Series II xo though. Perhaps someone else will be able to identify it.

The tweeters are the same though correct? Are there any differences in the cabinets, aside from the different terminal cups?

ben62670

Never saw a monitor XO like the second pic

comfortablycurt

This is a Monitor 5 Series II crossover as far as I know.

http://www.polkaudio.com/forums/showpost.php?p=625564&postcount=100

Like I said...it's significantly different.

Is it possible that the second one was from a transitional period between models? Polk does have a reputation for that.

Is it possible that it's an early Series II crossover, that utilized some leftover components from the 5B crossovers?

The Baumer

Yes, the tweeters are the same (SL2000) and the speaker cabinets are identical save for the crossover plates.