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A Recone Guide

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norty303 View Drop Down
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Post Options Post Options   Thanks (4) Thanks(4)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Topic: A Recone Guide
    Posted: 14 August 2009 at 1:06pm
As hinted at previously, one of our more knowledgable members has kindly put together a very comprehensive recone guide for your delectation and delight.  Not sure yet which forum this should live in, or if indeed it warrants an all forums announcement, but will ceertainly be added to the Technical Classics.
Anyway, enough of my waffle:
 
A Re-cone Guide

Read through the full instructions before starting to ensure you know what order you need to do things.

The re-coning thing isn't too hard the main requirement is care and cleanliness. General rules ; Handle the cone assembly with extreme care, it's very easy to damage.

Avoid getting any dirt or particles down inside the voice coil gap, turning  the speaker upside down and shake it whilst gently blowing often helps (keeping your eyes shut to avoid injury)

 

Some background info.

 
Types of loudspeaker

As far as re-cone kits are concerned there are a few possibilities

A: Single suspension, comes as a cone/coil/suspension assembly

B: Double suspension, comes as  a cone/coil/suspension assembly

C: Single suspension, comes as a coil suspension assembly and a separate cone

D: Double suspension, comes as a coil suspension assembly and a separate cone

E: Single suspension, comes as separate coil, suspension, cone

 
Contents

Step 1 Pre stripping out checks

Step 2 Stripping out the old software

Step 3 Stripping out the old software

Step 4 Cleaning out the hardware

Step 5 Doing a dry build

Step 6 Gluing and fitting the new software

Step 7 Gluing and fitting the new software

Step 8 Gluing and fitting the new software

Step 9 Fitting gaskets

Step 10 Fitting gaskets

Step 11 Electrical connections

Step 12 Dust-cap fitting

Step 13 Dust-cap fitting

Step 14 Dust-cap fitting

Step 15 Final electrical connections

Step 16 Testing

 

Appendix 1 Shims, what to do if they are too tight/loose or missing

Appendix 2 What to do if the coil and suspension don’t come glued together

Appendix 3 Stripping out double suspension speakers

Appendix 4 If the gasket supplied is of the strip type and not segments

Appendix 5 Separate cone and suspension assemblies

 

 

Step 1: Pre stripping out checks Before starting to strip out the old software there are a couple of things to take note of and possibly a picture or two. It is well worth cutting the old parts out carefully and as complete as possible, this will allow you to use this as a reference when re-coning later. It is well worth checking that the parts you have received look like the parts you are about to strip out and if not checking with the supplier.

            A: There are often flexible connections from the moving parts of the speaker (back of cone? to chassis connectors) these are very common on single suspension units and smaller coil double suspension units. Take careful note of the length of the loop, this will be critical later. Try moving the cone as far as it will go in each direction and note the effect on the tinsel loop. The wires must not pull tight at any time but should not be so long as to be able to touch each other

            B: Which way around is the dust-cap fitted, they are usually pointing out (convex) but sometimes concave.

            C: If the cone/coil/suspension are not glued together in the kit you have received then note which way up the suspension goes (first/outer roll up or down)

            D: Is the dust-cap fitted with a hard or soft glue, lead guitar speakers often use a soft glue whereas pro PA speakers most often use a hard glue.

 

Step 2; Stripping out the old software Remove all of the old cone assembly. First cut around the cone edge and the suspension (AKA spider, damper), cut the braids and lift the old cone assembly out. As soon as the coil is out, cover the gap with masking tape to prevent dirt entering into the magnet assembly. Next remove all traces of the surround and suspension from the chassis. The aim is to get a smooth / even surface on the rim of the housing and the platform for the suspension. Solvents such as acetone, MEK, Cellulose thinners or automotive type gasket remover can all help soften the old glues otherwise they can be scraped off with a sharp knife. For double suspension units see appendix 3.

 

Step 3: Stripping out the old software Remove the old lead-out wires (Tinsel/braid/Litz wire) form the connectors on the chassis, usually this connection is soldered. Take care with the solder tags as they can be fragile and new ones are often not supplied with a re-cone kit.

 

Step 4; Cleaning out the hardware Blow all the loose dust from the surface, a hand/foot pump (car/pushbike type) can be useful here. Wipe over the housing with a cloth to ensure it is clean. Remove the tape from the magnet gap. Roll a piece of masking tape into a tube sticky side out, then flatten it and gently push it into the magnet assembly gap. Slide it round to collect any dirt or filings within the gap. Check visually (use a torch or bright lamp) that there are no particles visible in the narrow circular channel where the voice coil will sit. This is where great care is required the smallest piece of magnetic dirt left behind will cause a nasty coil rub, so the message keep on cleaning.

            It the speaker has some sort of mesh/gauze fitted in the centre pole then this may have become partially blocked and require cleaning with some sort of solvent. Failure to do this could cause the repaired speaker to burn out as hot air cannot vent properly. If the speaker has a foam type bung this may also have become partially blocked over tiem and should be cleaned

 

Step 5: Doing a dry build Do a dry build before thinking about glue, fit the centering shim/shims (if none were supplied see appendix 1)  evenly around the gap. Gently lower the re-cone kit over the shims, if it feels tight then stop and adjust the shims see appendix 1. Once in place observe that all of the shims feel even when gently moved, this will be essential in making sure the assembly is correctly centered when the glue is used. Note how the lead-out wires need to be evenly aligned relative to the chassis connectors, again this will be important when the glue is applied and will not be easily adjusted once the glue starts to go off. Note at this stage that with the re-cone assembly fitted and the surround resting on the chassis, the relationship between the inner and outer parts of the surround is the same all round the circumference. If you ‘slide’ the cone over to one side the inner part of the surround will be higher than the outer one side and lower at the other. This is a tilted cone and bad news, take note as when the glue is on the assembly needs to be even all around and once the glue grabs hold it will not be easy to move it. Note the inner and outer rolls do not necessarily need to be level with each other but it is important that they are level/higher/lower evenly all around. It is worth noting at this stage where the cone surround sits on the chassis and especially where the suspension sits (as there are often a number of lands and you really want to put the glue on the right one).

Note: Handle the cone assembly with extreme care ! The coil can be easily made oval by even gentle squeezing. This will render it useless.

            Remove the re-cone assembly and have one last check of the magnet gap, dirt in gap is the enemy of all speaker assembly.

 

Types of re-cone kit For Types C&D above it is best to fit the coil suspension assembly first, get that in nicely and with the shims feeling even all around the gap before fitting the cone. With double suspension assemblies especially bolted in types it is well worth running the unit at low power to check it is not rubbing. If it rubs try loosening the bolts and tightening them in a different order, or in extreme cases opening the holes in the double suspension assembly up a bit with a drill. Bolts should always be tightened working opposites never working around in a circle.

What type of gasket came with the re-cone kit you received? If you have segments then proceed as below, if you have a strip type gasket then refer to appendix 4 before proceeding with gluing.

           

Step 6; Gluing and fitting the new software Place the coil centering shims/shims upright in the magnet gap and evenly spaced (if there are more than 1) Make sure the shims are evenly spaced (they are used to keep the coil central as the glues dry)

 

Step 7; Gluing and fitting the new software Apply a suitable glue evenly around the suspension platform (or the suspension foot if it does not sit on a platform) and around the housing rim (For separate suspension and cone surround assemblies see appendix 5), taking care to put the glue on the right lands to match the re-cone kit (manufacturers do change designs so it is not always the land the old parts came from). This should come to the inside edge of the rim, but be a thin coat so it doesn't squeeze out under the surround.

 

Step 8: Gluing and fitting the new software Gently lower the re-cone assembly over the shims making sure they are all inside the coil (none are outside the coil), and gently ease the cone assembly into the glue beads, don’t push it in too far allowing it to be sunken, the suspension should be slightly dished in. At this stage, depending on the nature of the glue being used you don’t have much time.

Note: Handle the cone assembly with extreme care ! The coil can be easily made oval by even gentle squeezing. This will render it useless.

 

A: Check the lead out braids are facing the chassis connectors

B: Check that the surround is even all the way around (as detailed in step 5 doing a dry build)

B: Check the shims feel even all round and not tighter one side than the other, if they are gently try pushing the coil into the gap and letting it ‘bounce back or ease the assembly over to even the feel of the shims.

 

 

 

Step 9; Fitting gaskets Using the same glue, apply an even layer to the 4 front gasket segments, and stick them down to the housing rim on top of the cone edge. Ensure they clear the screw holes!

            Note if your gasket is of the strip type then see appendix 4

 

Step 10; Fitting gaskets Place a flat board on top of the speaker, ensuring the board will rest on the gasket segments and not touch the surround. Check that the gaskets are still right out to the edge, and haven't slipped inward. It will be too late when the glue has dried! Add some weight on it (e.g. a couple of phone directories), and leave overnight to dry.

 

Step 11: Electrical connections There will be electrical connections to be made next, these vary between manufacturer’s typically the tinsel/braid needs to be soldered to the chassis connectors and if your re-cone kit was of type C,D or E then there could be voice coil wires to be soldered to the tinsel/braid where it is fitted to the cone. At this stage it is best to only solder connections which will lie under the dust-cap. When soldering especially near the voice coil take care that nothing falls into coil. 

 

Step 12; Dust-cap fitting When the glue is dry, carefully remove the shims from the coil. Check the gap for and debris as this is your last chance, once the dust-cap is on it’s too late.

 

Step 13; Dust-cap fitting Fold a piece of masking tape into a 'T shape, and stick to the dust cap to form a handle to hold the cap by. Place the cap centrally on the cone, and use a very soft pencil to draw a faint line around it to act as a guide for gluing. NB DO not push the pencil onto the cone, it is less than 0.5mm thick, and made of paper !

 

Step 14; Dust-cap fitting If the dust-cap has a foot where it glues to the cone then the glue is best applied to the foot then fitted to the speaker. Apply an even bead of a glue to the dust-cap foot using a small paintbrush, stick or spatula, and place the cap on the cone using your pencil guide to get it central. Use just enough glue to squeeze 1-2mm out from the foot all round. Leave to dry until the glue has cured. A small weight may be used to ensure the dust-cap sits firmly onto the cone.

            It the dust-cap does not have a foot then it is best to put the dust-cap in place, hold it down with a small weight and then apply a bead of glue. Apply an even bead of a glue half on the dust-cap and half on the cone. The amount of glue required increases with coil diameter/power handling and reduces with increasing frequency range. So subs maybe 6mm wide bead, mid/highs 2mm wide. You can use the old software as a guide to the amount of glue required. Leave to dry until the glue has cured.

            Remove the masking tape once the glue has cured

 

Step 15: Final electrical connections If the tinsel/braid wires come from a moving part (typically single suspension units and some double suspension units the wires come off the back of the cone) then the ‘loop’ of tinsel is critical. It is best to put the tinsel/braid in place setting a loop such that the wires cannot touch each other and secure without soldering. Next try moving the cone back and forth (carefully so as not to damage anything) and observe if the wires pull tight at full excursion, if they do the loop is too short. Note this needs to be done with the glues cured. Once a suitable loop length has been set then the connections can be soldered.

 

Step 16: Testing

 

 

           

 

Appendix 1 Shims

If the shims are not supplied or seem too tight then use card or similar, these need to be the same thickness all round the gap, they may be made up of different thickness bits but each ‘set’ must be the same thickness otherwise the coil will be off center. The aim is to have as few gaps between the shims as possible however sometimes removing 1 set and re-spacing the rest is the only way to get a good fit. What you don’t want are big gaps between the shims as this will lead to an out of round coil. The coil needs to be a snug fit over the shims, too loose leads to off centre coils, too tight and you risk deforming the coil when fitting it.

 

Appendix 2 Setting the coil height

For type E above you will need to set the height of the coil in the gap, the aim here is for the coil to be positioned such that the amount of coil above the top/front plate is the same as below. This is not easy as you can’t see the bottom side, the way to proceed is a combination of matching the old parts you removed (IE distance from bottom of suspension to start of coil winds) and measuring the thickness of the top/front plate thickness (at the centre if the plate is not the same thickness all the way across) and setting the coil equally about this thickness. If you know the mathematical Xmax (coil wind length-front plate thickness)/2 then this is the amount of coil which needs to be set above the front plate. Note not all manufacturers use mathematical Xmax in their datasheets, often however they do state the front plate thickness and the wind length of the coil. Once you have worked out the position for the coil, fit it in the gap with the shims holding it in place and mark the coil on the inside with the correct height (line level with the top of the centre pole). Fit the suspension over the coil and lower it into the magnet gap, adjust the coil within the suspension to align the height (using the mark you made earlier to ensure correct setting) Glue the coil to suspension and allow to cure.

 

Appendix 3 Stripping out double suspension units

Some speakers are dual or double suspension, in this case there will be some sort of spacer ring holding the suspensions apart, this will be part of your re-cone kit and so the old spacer needs to be removed from the chassis. Often these spacer rings are glued to the chassis, a wood chisel may be put at the joint with the chassis and tapped gently with a hammer to separate them. If it is bolted in then you have been lucky, simply un-bolt it. If you damage the chassis land when removing the spacer it will need to be filled and filed flat so that the new coil suspension assembly sits in place flat.     

 

 

Appendix 4 If the gasket supplied is of the strip type

If the front gasket is of the strip type then don’t fit it at the same time as the cone surround is glued in. instead use a soft, blunt ended (piece of wood shaped like a scraper) to rub the surround into the glue. This should be done every few minutes and with gradually increasing pressure until the glue has grabbed the surround. At the same time the suspension should be rubbed into it’s glue, you will probably find your fingers best for this. Make sure when rubbing down:

            A: You don’t sink or tilt the assembly

            B: You don’t rub through or otherwise damage the surround

 

Appendix 5 Separate cone and suspension assemblies

For re-cone kit types types C,D and E as detailed above the coil/suspension assembly should be fitted first and so only apply the suspension to chassis glue (no glue if it is a bolted in assembly)

            A: Check the lead out braids are facing the chassis connectors.

B: Check the shims feel even all round and not tighter one side than the other, if they are gently try pushing the coil into the gap and letting it ‘bounce back, making sure it ends up only slightly ‘dished’ not excessively sunk or ease the assembly over to even the feel of the shims.

Allow the glue to grab,

With double suspension assemblies especially bolted in types it is well worth running the unit at low power to check it is not rubbing. If it rubs try loosening the bolts and tightening them in a different order, or in extreme cases opening the holes in the double suspension assembly up a bit with a drill. Bolts should always be tightened working opposites never working around in a circle.

            Apply a suitable glue evenly around the surround land. This should come to the inside edge of the rim, but be a thin coat so it doesn't squeeze out under the surround. Note which way the cone has to align for the tinsel/braid wires to align with the chassis connectors.

 Lower the cone surround over the coil, ensuring that if there are coil wires sticking up to be soldered to the tinsel wires in the cone that they are on the inside of the cone neck not out of site underneath. It is important to lower the cone as level as possible, if it is tilted then glue may pick up on the rear of the moving part of the surround, this will cause at best edge ticks and at worst reduce the life of the speaker

            A: Check the cone tinsel/braid wires align evenly with the chassis connectors

                                    Now return to step 9

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jonny4288 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonny4288 Quote  Post ReplyReply Direct Link To This Post Posted: 15 August 2009 at 2:41pm
I would suggest technical classics?
 
Great guide
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nomis Quote  Post ReplyReply Direct Link To This Post Posted: 15 August 2009 at 3:32pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ryan94 Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2009 at 9:04pm
thanks for this it will help alot of people.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote loonie Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2009 at 9:48am
And possibly put a few out of a job LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote colinmono Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2009 at 1:51pm
Great work, thanks to the author.

Can I be cheeky and ask for some info on recommended glues too?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote H... Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2009 at 4:54am
Well done!
 
Don't worry F$cked up bigger gigs than this one...........
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2009 at 1:44pm
spider / surround to base / basket = rubberised lino flooring adhesive (i use dunlop) or contact adhesive

voice coil to cone =  loctite 382 (tack pack) (which is a flexible cyanoacrylate)

dust dome to cone =loctite 4105 (black tack) (which is a flexible cyanoacrylate)


there are other glues like tretobond but i havn't used them, maybe others could add to a list..




Subs + Barges = :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ryan94 Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2009 at 1:49pm
voice coile to cone i used two part epoxy.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2009 at 2:05pm
the vc to cone has to be a high temperature glue, as i know someone here who used 2 part epoxies that failed, and i think it was because they were cheap / unsuitable.
Subs + Barges = :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ryan94 Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2009 at 2:08pm
well mines been working fine. but there proberly is better glue out there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2009 at 5:19pm
Evostick impact adhesive for the surround/spider.  It appears to be what beyma supply with their kits
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