Advice: Diagnose & Repair Monitor 10Bs
Panfish
Posts: 7
I was recently given an old mint pair of Polk Monitor 10Bs. When I hooked them up I heard distortion and my surge protector popped. I have been reading about the light glue used and how the cones can come apart, how the crossovers can go bad etc...and clearly they are older.
I would like to diagnose and repair them if possible but have not repaired speakers before (aside from simply swapping out components). Can anyone recommend some good sites that outlines step by step how to diagnose the issue? Or would you suggest I take them somewhere? From a learning/hobby perspective I would rather do it myself.
I am new to this forum so thanks in advance for your thoughts.
Charles
I would like to diagnose and repair them if possible but have not repaired speakers before (aside from simply swapping out components). Can anyone recommend some good sites that outlines step by step how to diagnose the issue? Or would you suggest I take them somewhere? From a learning/hobby perspective I would rather do it myself.
I am new to this forum so thanks in advance for your thoughts.
Charles
Best Answer
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According to my files, the MW6503 should have a DC resistance of 6.54 ohms.
![[Deleted User]](https://w8.vanillicon.com/83b82048d67877ca27bbc25d5d38f9d3_100.png)
Answers
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Hi Charles,
Welcome to Polk's forum. To have such a relatively violent reaction to trying to play the speakers I would imagine they are presenting a dead short. Do you happen to have access to a volt/ohm meter?
Regards, Ken -
Thank you for the response. Yes I do have access to a volt/ohm meter.
Charles -
Ah, good. First thing to do is set the meter to the lowest resistance setting it has and then place one probe in the negative terminal and the other probe in the positive terminals of the speaker. Then note the resistance reading and then do the other speaker.
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Ok. Sorry it took so long for me to get back to you. When I set the meter on 200Ω the right speaker reads 4.5 and the left speaker reads 4.4
What next?
Thanks
Charles -
Hi Charles,
It doesn't seem that the speakers are shorting out the amplifier as your first post indicated. Each speaker has four active components, the tweeter, the two mid range drivers and the crossover. One approach is with just one speaker connected remove the grille cover and use a pillow to cover up the two drivers, isolating the tweeter and at a moderate volume see if the tweeter is working or distorted. Use this same technique to isolate each of the remaining two drivers, letting you hear if they are working.
Unless the speakers have been heavily abused the crossovers are usually not damaged, but their condition can be determined by looking at them. If tweeters or drivers need to be replaced contact Polk CS at 1-800-377-7655 select option 2.
I hope this is helpful.
Ken -
OK thanks - I will do that. Also I have the impedance from my amp at 8Ω vs.4Ω. I'm not sure this would make a huge difference with 6Ω rated speakers but wanted to ask.
Thanks -
In general terms, keep it in the 8 ohm setting.
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Ken,
I started listening to each speaker as you suggested. One of the tweeters is definitely bad so thanks for the CS number. Question on the replacement of the tweeters....Would you recommend the exact replacement for the original tweeters or is there an upgrade I can consider? I've been reading a lot of posts where people have upgraded (although that means something different to everyone) - especially to Peerless. What are your thoughts?
Thanks
Charles -
Hi Charles,
When you call Polk for the tweeter mention your CP membership they give a reduced price and free shipping, I believe. I too, have to go on other member's opinion since I don't have the Monitor series to give first hand experience. Probably, the best approach is to get two new tweeters from Polk (if it fits your budget) and replace both of them. This gives the speakers the most sound improvement for the money spent. Then once you have listened for a while to their qualities you could consider re-working the two crossovers, substituting designer parts for the originals.This would give another significant level of improvement, but also relatively expensive.
At that point you would have a speaker system of remarkable sound quality and the pleasure of owning a recognized classic audio speaker.
Cheers, Ken -
Thanks Ken! I ordered the tweeters as you suggested. And I'm measuring the OHMs of the drivers which are MW6503 but cannot find online what a decent reading is. Can you help me with that? I am getting between 4 & 4.5.
Thanks
Charles -
Let me check my old files.
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Huh. As a general rule I always heard that the resistance should be about 2/3 or the speaker impedance. Since these are 6 ohm I figured I was good with my reading but based on what you found it would suggest that they are probably bad. Is that your take too? Thanks
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It might be more related to the meter doing the measuring in this case. If available "zero out" the meter, meaning touch the two probes together and get the indicator to read zero. If your meter is battery operated make sure the battery is fresh.