Hi All
Let me preface this saying I am an absolute beginner when it comes to speakers and have never tinkered with them beyond plugging them in and listening to them so am after some advice.
I recently picked up a pair of Monitor Audio 703 PMC speakers for just £50. I didn't get to audition them properly as the seller was packing up ready to move and it was pretty late at night. Thought I would take the chance and go for them. They sound amazing, really nice mid-range. However one of them has an issue.
The dust cap (bullet-shaped) keeps slipping and touching the speaker cone causing a horrid distortion in one speaker. I very gently pushed it upwards away from the cone and the problem went away BUT unfortunately, it keeps happening and I have to adjust it quite often to get it central again. It feels gummy as if there is glue behind. I've tried turning the speaker upside down in the cabinet to see if it would solve it but it just sagged the other way.
I'm hoping its a real easy fix but want some advice before I go start fiddling with the speakers. What is the dust cap attached too? Can it be easily removed and/or re-glued? If so what type of glue should I use and what do I need to be careful of? We're in quite a remote rural area and I'm not aware of anyone locally that can repair speakers and I'm very reluctant to have it shipped off anywhere due to the size and weight and fear of further damage.
I've attached a couple of pics to highlight the problem. You can see very little clearance between the bottom of the dust cap and the cone which is causing the distortion. Any advice is gratefully received.
G
Let me preface this saying I am an absolute beginner when it comes to speakers and have never tinkered with them beyond plugging them in and listening to them so am after some advice.
I recently picked up a pair of Monitor Audio 703 PMC speakers for just £50. I didn't get to audition them properly as the seller was packing up ready to move and it was pretty late at night. Thought I would take the chance and go for them. They sound amazing, really nice mid-range. However one of them has an issue.
The dust cap (bullet-shaped) keeps slipping and touching the speaker cone causing a horrid distortion in one speaker. I very gently pushed it upwards away from the cone and the problem went away BUT unfortunately, it keeps happening and I have to adjust it quite often to get it central again. It feels gummy as if there is glue behind. I've tried turning the speaker upside down in the cabinet to see if it would solve it but it just sagged the other way.
I'm hoping its a real easy fix but want some advice before I go start fiddling with the speakers. What is the dust cap attached too? Can it be easily removed and/or re-glued? If so what type of glue should I use and what do I need to be careful of? We're in quite a remote rural area and I'm not aware of anyone locally that can repair speakers and I'm very reluctant to have it shipped off anywhere due to the size and weight and fear of further damage.
I've attached a couple of pics to highlight the problem. You can see very little clearance between the bottom of the dust cap and the cone which is causing the distortion. Any advice is gratefully received.
G
Hey,
I’m no expert but I think you can reglue it. I’m sure a more knowledgeable member will chime in.
Maybe more concerning are the cones distorted?
I’m no expert but I think you can reglue it. I’m sure a more knowledgeable member will chime in.
Maybe more concerning are the cones distorted?
It sounds like the dust cap may be loose enough that you could be able to remove it by gentle persuasion.
If it doesn't cooperate you may have to consider the minimal local application of a suitable solvent using a fine artist's brush.
I would use this product to fix the dust cap back in place: https://www.halfords.com/motoring/p...nville-black-silicone-sealant-40g-173867.html
If it doesn't cooperate you may have to consider the minimal local application of a suitable solvent using a fine artist's brush.
I would use this product to fix the dust cap back in place: https://www.halfords.com/motoring/p...nville-black-silicone-sealant-40g-173867.html
I’m surprised a silicone sealant would be used there. Makes for an easy repair though. Does the dust cap actually have any sonic effect?
The sealant is also an adhesive.
I presume it acts as a phase plug to extend high frequency response.
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I've looked further into woofer phase plugs which are commonly made of aluminium.
A phase plug may screw into the central pole piece, the fixed cylindrical metal part which is surrounded by the moveable voice coil former.
Alternatively, I've seen mention of the phase plugs being glued to the pole piece or even being attached with double sided adhesive tape.
Whatever the method of reassembly, the voice coil former must remain free to move.
Unless used for a heat radiator for the pole piece, or to stretch teh HF extention as far as possible, a felt plug is probably best.
dave
dave
Thanks for picking this up, Dave.
Have you anything to say about how garyjjg might go about removing his loose phase plug?
We're not sure how it is attached to the pole piece.
Have you anything to say about how garyjjg might go about removing his loose phase plug?
We're not sure how it is attached to the pole piece.
So I was feeling bold and managed to
very carefully work the plug loose. Attached is a pic of the speaker without it. Plays just fine with it missing. Going to pick up some of the adhesive @Galu recommended and have a go at re-attaching it. Any dos or don'ts? Any thing to be particularly careful about when re-gluing?
It's wonderful what a little brute force and ignorance can achieve! 😀
Clean all traces of the old adhesive off the phase plug 'spike' and out of its recess in the pole piece.
Apply the new adhesive only to the central 'spike' of the phase plug. It mustn't be able to spread across the surface of the pole piece and jam up the movement of the voice coil former.
The advantage of the sealant/adhesive I recommended is that it gives you time to properly position the plug before it cures - lay the speaker on its back during this process of course. The fact that the adhesive remains flexible once cured means you will be able to pull the plug back off for repositioning if necessary.
Let us know how it goes.
P.S. Be very careful that old adhesive does not fall down the gap between voice coil former and pole piece!
Clean all traces of the old adhesive off the phase plug 'spike' and out of its recess in the pole piece.
Apply the new adhesive only to the central 'spike' of the phase plug. It mustn't be able to spread across the surface of the pole piece and jam up the movement of the voice coil former.
The advantage of the sealant/adhesive I recommended is that it gives you time to properly position the plug before it cures - lay the speaker on its back during this process of course. The fact that the adhesive remains flexible once cured means you will be able to pull the plug back off for repositioning if necessary.
Let us know how it goes.
P.S. Be very careful that old adhesive does not fall down the gap between voice coil former and pole piece!
As i was reading Galu’s post i was contemplating what kind of attachment would go loose/wobbly and then Gary posted a picture of what i was imagining. Cheap plastic phase plug.
Now from what i am going to say, you might want to try to pull the other one off.
Clean up the broken bass of the phas plug. Fil th holes. Given how they will need to be reattached somethign that will glue (ie not ductal, plaster or epoxy or something. TYhen carefully epoxy it back into place. Be very careful you do not want any to squeeze out and glur the voice coil in place. Thiose cavities are BAD.
dave
Now from what i am going to say, you might want to try to pull the other one off.
Clean up the broken bass of the phas plug. Fil th holes. Given how they will need to be reattached somethign that will glue (ie not ductal, plaster or epoxy or something. TYhen carefully epoxy it back into place. Be very careful you do not want any to squeeze out and glur the voice coil in place. Thiose cavities are BAD.
dave
Thanks, Dave.
I was assuming that the 'spike' of the plug was not broken, but could be reglued into its location hole after a clean up.
However, if the 'spike' is broken then your suggestion of cutting it off etc. makes sense. Note, if it has broken, then its tip is still in the locating hole.
Just to be clear on what adhesive to use to fill the hole in the pole piece as well as reglueing the plug - are you suggesting a two part epoxy adhesive for both of these requirements?
Thanks for the input folks. Looks like everything is intact, nothing broken - just covered in the old glue which is hard and crumbling away. I think these speakers were from the early 90s so I'm guessing the glue has just aged poorly. Will have a go at re-affixing with some epoxy and let you know how I get on. I think just a little on the centre pole should hopefully do the trick and minimise the risk of it spreading.