Tweeter replacement options for Monitor 10b

mtippin · November 19

Hello, long time Polk fan, first time poster. I’ve been lovingly tending to a pair of recently acquired Monitor 10B speakers. I’m having a hard time pinning down the exact generation, but will share some photos. I was able to epoxy stabilize the four driver magnets that survived the years in alignment, but one tweeter just slowly faded out on me. I checked continuity on the fuse, and it was not blown.

I’m selling the wisdom of the crowd here. Is there a chance that the crossover developed an issue? Should I just find proper modern replacements? I’m willing to consider any options.

Thank you for your help!

Gardenstater · November 19

Get a pair of Peerless tweeters on eBay, preferably the ones from a later Polk with the aperture tuning hole in the dome. Better sounding tweeter than the SL1000 any day, according to many reports.

F1nut · November 19

Yep, that's a dead tweeter. The suggestion to obtain original Peerless tweeters is your best course of action.

mtippin · November 19

That should read, “seeking” the wisdom of the crowd

F1nut · November 19

Remove the fuse on both speakers. Clean the metal ends on the fuses and clean the metal fuse clips on the binding post plate. Report back.

The caps on your crossovers are way past their lifespan and should be replaced. While in there replace the resistors as well. There are plenty of posts here on upgrading Monitor 10 crossovers.

xschop · November 19

mtippin wrote: »

Hello, long time Polk fan, first time poster. I’ve been lovingly tending to a pair of recently acquired Monitor 10B speakers. I’m having a hard time pinning down the exact generation, but will share some photos. I was able to epoxy stabilize the four driver magnets that survived the years in alignment, but one tweeter just slowly faded out on me. I checked continuity on the fuse, and it was not blown.

I’m selling the wisdom of the crowd here. Is there a chance that the crossover developed an issue? Should I just find proper modern replacements? I’m willing to consider any options.

Thank you for your help!

Could be the coil wire lead oxidized and broke near the RTV channel. Could be a shifted tweeter magnet. Pull the tweeter and check continuity between the terminal tabs.

Gardenstater · November 19

Check the resistance of the tweeter resistors as well as the tweeter. The SL1000 tweeter should have a DCR of 6.15 Ohms give or take a little. You could also try putting a small piece of tissue on the dome of the tweeter and briefly touch a AA or AAA battery to short wires connected to the terminals and you should see the dome move just a bit.

mtippin · November 19

Thank you for your quick replies.

@F1nut - removed, inspected, lightly sanded Thank you all for the quick replies.

@F1nut - I inspected fuses and clips and lightly sanded all clip contact points. Tried new 1A fuse as well after checking all for continuity. No change in tweeter response. (Advice taken on crossover updates, I will seek out those forum posts as you suggest.)

@xschop - removed tweeter, checked connections, visual ok. Checked continuity - fail. Removed working tweeter, checked continuity - 06.1 on 200 ohm scale. Placed working tweeter in cabinet with failed tweeter - working tweeter produced signal. Placed non-working tweeter in cabinet with working tweeter - no signal.

@Gardenstater - have not yet pulled passive bass resonator to get to crossover to check components, but did AAA batt test on both tweeters. Non-working - no signal, no movement. Working - signal (static) as expected.

Is my best strategy to attempt repair? Or do I look towards replacing tweeters? (I’m assuming it’s wise to do both?) If the original components can reasonably be fixed, I’m game, but I’m also aware that one QA/inspection date is from 1983, which might make them 42 years old, and likely to fail at some point again in spite of all best efforts.

Thank you all, again.

mtippin · November 19

I'm looking into replacements now, thank you all again for your guidance. Would it be advisable (or even possible) to retain the aluminum faceplates and swap out the driver with a modern OEM like a Polk Audio RD0194-1 Tweeter? (As seen here: https://reconingspeakers.com/product/polk-sl1000-sl2000-tweeter/ )

I see that the original version has surface mounted wire from the rear posts to the silk cone, but the modern replacement appears to have the mounting posts attached to the magnet/cone assembly that could be freed via the faceplate screws?

I'm thinking this might be a bad idea, especially as I'd have to wreck a working vintage tweeter to do this.

Photos of the new OEM driver from ebay auction that claims to be a replacement for SL1000 (seller is Midwest Speaker Repair)

If I am able to determine that these dimensions are a simple drop-in replacement that does not require modifying the cabinet, I'd be glad to just get the M10B's back online.

Thank you for the support and guidance.

F1nut · November 19

https://forum.polkaudio.com/discussion/182943/the-tale-of-5-tweeters-sda-tweeter-replacement-guide

Gardenstater · November 19

The RD0194-1 requires a slightly larger cutout. There have been a couple people who have installed the SL1000 tweeter bezel on it and no cutout mods needed but it isn't simple and maybe the magnet hole pattern isn't exactly the same (I don't remember). The other option is you can trim the plastic bezel down a bit to make it fit but then the mounting holes do not match perfectly.

Personally, I'd go with the Peerless. No cutout mods needed. Polk sent the SL1000 as warranty replacements (5 year warranty) when people's Peerless failed, after Peerless ceased production of it and Polk had moved on to the SL1000. They don't seem to have any longevity issues.

I can personally vouch for the fact that they sound great.

pitdogg2 · November 19

The cut for the peerless/SL1000 is oval to allow space for the voice coil connection tabs. That oval cut will push the RD-0194/98 connection tabs into the magnet assembly. You'll need to at a minimum use a round file to take a bit off the tweeter hole where those touch. I personally thought it put way too much stress on those VC tabs, I never tried it hooked up with signal, heck it might just short out against the magnet unless you put some tape or heat shrink around the quick connect.
Well then you have the screw holes do not line up ...

xschop · November 20

Well you've got two options.

The Wuhan silk dome swap on the SL1000 faceplates.

Slightly slot the magnet holes of the SL1000 plates, and the RDO dome/mags bolt right up.

Gardenstater · November 20

If you are averse to destroying a functional SL1000 here is a pair of blown Peerless for sale that you could buy for their aluminum bezels and convert them to RD0194-1 if you bought a new pair of those. I don't see any intact Peerless with the Polk holes in the dome atm.. They come up fairly often but do get snatched up pretty quickly I wouldn't want to pay $35 for blown ones though. I don't think I'd pay more than $20. PS: this is assuming the magnet holes are close or the same. PPS: I measured one of my Peerless and spacing is about 1.544 in. (39.2 mm)

https://www.ebay.com/itm/297775974146

DeRod · November 20

The 1st two answers given are the best.

I replaced the SL1000s in my Monitor 7s with older Peerless tweeters and the bolt pattern on those lines up perfectly.

IMO the older Peerless are as good or better than any of those newer compatible Polk tweeters.

The SL1000 is super loud and bit strange sounding tweeter. The Peerless in the same speakers will sound less loud and much smoother. I think the combination of the Peerless tweeters with the MW6502s is pretty awesome. It's a worthwhile experiment that will cause no damage to your speakers. If you don't like the way it sounds you can away just switch back.

BTW - I never switched those SL1000s back into my Monitor 7s I still have the Peerless tweeters in those speakers.

mtippin · November 20

Thank you for the advice @Gardenstater and @F1nut. I purchased these two peerless tweeters from ebay just now. Fingers crossed that they are a fit, and they arrive is good condition. I'll follow up after they are installed.

From the auction listing:

Pair of original vintage Peerless 1" soft dome tweeters, made in Denmark. They had been retro-fitted into a pair of Dynaco A25 cabinets as replacements for the original Seas tweeters. They sounded excellent in place with the original woofers and crossovers, but the original owner had to modify the cabinets with custom built adapter plates in order to fit them.

I did not try to remove the labels, but there does seem to be a slight recess or dimple in the center of the magnet assemblies. The small white labels on the perimeter of the magnets are too faded to discern any information or part numbers.

They were purchased together as a pair decades ago, and had always been used together in the same cabinets. They are similar to OEM units found in some Polk, ADS, and other classic speaker brands.

F1nut · November 20

If you want you can make a small hole in the center of the dome using the hot tip of a pen style soldering iron, which is how Polk did it.

Gardenstater · November 20

Well done. They sure didn't leave you much wire. If you do try to desolder make sure you clamp a good tight fitting aluminum heat sink clamp onto the terminals and use flux and work quickly so that the terminals don't fall off and the VC wire doesn't desolder inadvertently.

DeRod · November 20

I think it would cool to leave those exactly like they are.

Later on maybe compare those to the USA made peerless for Polk with aperture tuning hole… I wonder how much of a difference it really made. The hole I mean .. would be an interesting comparison in my opinion..

Gardenstater · November 21

The story goes that Polk burned the hole with a soldering iron. They certainly did it pretty darn precisely considering the method, if so. It would be awesome to test those Denmark made ones for sure. Both Dats VIII testing and listening tests. I have some Peerless that Ohm out at less than 7 Ohms. The visual variances in these tweeters is off the charts, especially the back plates. I haven't tried to count how many different ones there are but it is a lot. These Danish made silk domes look to have a different doping, possibly, compared to all the ones I have which are most likely all USA made.

DeRod · November 21

I highly recommend not burning anything into those nice-looking Danish tweeters 🤣 I looked closely at couple pair of my USA ones with the aperture holes and I'm not sure about the urban legend of the soldier iron. 1st - the hole does not look burnt at all. A soldering iron would have left some melted edges, I would think, and that isn't apparent on any of mine. 2nd - the hole is dead center on all my tweeters. That would be impossible by hand and eyeball alone.

Back to what I was originally wondering does that tiny hole actually make an audible difference?

Gardenstater · November 21

Polk certainly claimed (suggested?) that it did in the early brochure: "The dome is vented (aperture tuned) in much the same way that woofer systems are tuned to further smooth out its response curve and improve transient response and power handling"

Looks too perfect to me too. I wouldn't be surprised if there was some truth to it in the respect that in early experimentation that may be how they did it. Then maybe (?) they may have had it done by Peerless just prior to assembly after the doping had cured, using a punch and die in a jig. At least that is probably the way I would've done it. That would mean that Peerless would've done it for them and only them.

DeRod · November 21

100% agree that hole was most likely punched by Peerless for the Polk tweeters.

I understand the size of the vent/port effects the bass but there isn't any pressure being generated under that little dome and how would that effect the treble? The dome is just basically a piece of cloth covering the tweeter

F1nut · November 21

Nope, it's a fact that Polk did it.

DeRod · November 21

@F1nut I agree but like George pointed out the soldering iron hole was most likely like in the R&D phase. For production the hole was die punched. Sorry about the dirty and fuzzy tweeter but notice no burn of the fabric.

Again, just wondering if there is any audible difference or was this just a marketing ploy… did you read that add? Fluid Coupling … 🤪

Gardenstater · November 21

DeRod wrote: »

100% agree that hole was most likely punched by Peerless for the Polk tweeters.

I understand the size of the vent/port effects the bass but there isn't any pressure being generated under that little dome and how would that effect the treble? The dome is just basically a piece of cloth covering the tweeter

There actually is. There are many tweeters that have vented pole pieces, either to the interior of the speaker enclosure or to an enlarged chamber with damping materials added. This lowers the resonant frequency of the tweeter and allows it to play lower, more cleanly. Polk chose to vent to the front. There is a white disk of pretty dense felt under the dome stuck on top of the pole piece to help dampen out resonance in the Peerless. Rob has experimented with adding bored out pole piece and back chambers with lambswool, not to the Peerless, but to other tweeters with good results.

There are pretty early multi page informational advertisements in the magazines where Polk mentions that they precision aligned the voice coils in the tweeters through an alignment jig of some sort. So, it is very possible that they removed the dome/bezel/voice coil as an assembly in order to punch the hole and then reassembled and precision aligned the voice coil in the gap. Wouldn't surprise me, put it that way.

xschop · November 21

Until I see a copper plated/clad MW pole piece from vintage Polk, then any marketing ploy (pin-hole or not) from yesteryears is highly plausible IMO.

DeRod · November 21

@xschop That ad was a 1970s word salad 🤣🤣

Viking64 · November 21

ad, not: add

Jiminy effin' Christmas!

DeRod · November 21

@Viking64 Tank you

DeRod · November 28

F1nut wrote: »

Nope, it's a fact that Polk did it.

You ever burnt a hole in your tweeter? don't start making up stuff show us picture of you burning a hole in a tweeter 🤣🤣 Why don't you try it first before recommending someone else does it? Terrible!!

Tweeter replacement options for Monitor 10b

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