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Help with spider / recone

RxDx

RxDx

Speaker collector
I'm reconing some HPM 900 woofers. The graphite cones were entirely gone.
I ordered recone kits from Speaker Exchange.

Cones look great, voice coil looks great, but the spider concerns me. It's much
stiffer than original, if it was the same size. But it's actually a smaller diameter,
and on top of that, the inside radius has to be trimmed to allow the cone surround
to seat on the frame. New trimmed spider is on the left below, OEM center, new
untrimmed spider on the right.

It looks like I'm losing some bass response with this spider.
spiders.jpg

spiders2.jpg
 
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Looks like they should have sent you flat spiders, also since you trimmed the center hole of the spider larger to allow the cone to sit deeper you have no way of attaching the spider to the voice coil.. I think I'd stop and get the proper spiders before proceeding .
 
mikeybc said:
Looks like they should have sent you flat spiders, also since you trimmed the center hole of the spider larger to allow the cone to sit deeper you have no way of attaching the spider to the voice coil..
Click to expand...
It's not a bug- it's a feature:
spider3.jpg
I think I'd stop and get the proper spiders before proceeding .
Click to expand...
That's what I'm thinking. Lots of options on the auction site.
 
Further measurements: the new cone sits 4 mm closer to the magnet than the
original. I'm thinking about adding a shim at the surround. Otherwise, I'd still have
to cut whatever spider I use.
 
You need to be-friend a speaker repair pro who has access to the nation's largest speaker parts supplier, MWA Speaker Parts. Speaker Exchange probably gets their parts from MWA.
The bad news is MWA deals only with repair and retail shops in the speaker trade which is the reason for my initial recommendation.
 
I don't quite understand this. If the cone is a proper and correct replacement for the HPM900 cone (just a different material), then the cone edge and cone apex/voice coil junction should be the same, and the voice coil position should be the same, that is, centered horizontally and vertically in the magnetic gap. If the cone is too tall (angle too steep, thus making the cone deeper) and the cone must be allowed to sit lower, unless the voice coil former is shorter, or the voice coil is fitted higher, the coil will be in the wrong place relative to the gap.

IMO, this cutting of the spider ID and then gluing it presumably to some circular spot above the voice coil former onto a higher position on the cone seems very kludgy to me. If it was me, I'd be looking for a better engineered recone option.
 
Some of the very earliest AR3 cast frame woofers had their spiders glued to the underside of the cone up away from where the VC is glued to the cone. However, at that time AR was still in the early stages of their speaker business had to use what was available.
 
I'd think cutting the inside of spider will also reduce the limit of cone travel and possibly make a drastic change to the free air resonance of the woofer. One would think there's a spider out there that would match up to the original. Doing that spider cutting method you'd be just as well off to put different woofers in and save yourself the trouble of gluing everything together...i doubt it would sound like an original woofer. Just my opinion...I'm not an engineer by any stretch of the imagination :)
 
spkrdtr said:
You need to be-friend a speaker repair pro who has access to the nation's largest speaker parts supplier, MWA Speaker Parts. Speaker Exchange probably gets their parts from MWA.
The bad news is MWA deals only with repair and retail shops in the speaker trade which is the reason for my initial recommendation.
Click to expand...

Would you be a speaker repair pro? :) Best I can tell, I need a spider with 6.75" outside diameter
and ~2.65" hole.

mech986 said:
I don't quite understand this. If the cone is a proper and correct replacement for the HPM900 cone (just a different material), then the cone edge and cone apex/voice coil junction should be the same, and the voice coil position should be the same, that is, centered horizontally and vertically in the magnetic gap. If the cone is too tall (angle too steep, thus making the cone deeper) and the cone must be allowed to sit lower, unless the voice coil former is shorter, or the voice coil is fitted higher, the coil will be in the wrong place relative to the gap.

IMO, this cutting of the spider ID and then gluing it presumably to some circular spot above the voice coil former onto a higher position on the cone seems very kludgy to me. If it was me, I'd be looking for a better engineered recone option.
Click to expand...

Apparently, it's not exactly the same. There are actually two different kits offered for this woofer, one of them
~2.75" deep, way taller than the kit I ended up buying (it's about 2.25"). I can get the voice coil to the right
place, and I can make their spider work. But it's considerably tighter than the original.

mikeybc said:
I'd think cutting the inside of spider will also reduce the limit of cone travel and possibly make a drastic change to the free air resonance of the woofer. One would think there's a spider out there that would match up to the original. Doing that spider cutting method you'd be just as well off to put different woofers in and save yourself the trouble of gluing everything together...i doubt it would sound like an original woofer. Just my opinion...I'm not an engineer by any stretch of the imagination :)
Click to expand...

I agree- I believe this kit will seriously raise free air resonance. Haven't found a match on the auction site
yet. I'm holding out for a flat, B or C-level stiffness spider before I put these together.
 
RxDx said:
Would you be a speaker repair pro? :) Best I can tell, I need a spider with 6.75" outside diameter
and ~2.65" hole.



Apparently, it's not exactly the same. There are actually two different kits offered for this woofer, one of them
~2.75" deep, way taller than the kit I ended up buying (it's about 2.25"). I can get the voice coil to the right
place, and I can make their spider work. But it's considerably tighter than the original.



I agree- I believe this kit will seriously raise free air resonance. Haven't found a match on the auction site
yet. I'm holding out for a flat, B or C-level stiffness spider before I put these together.
Click to expand...
MWA does not carry flat spiders with 2.65 inch ID. Is that the voice coil OD? 2.618 OD is fairly common I.D. which would put the OD about where what you are looking for.
 
There is a cup spider available from MAT Electronics, that's big enough to be cut down (cut off the "cup" sides, leaving as much flat diameter as possible) to a flat spider, and fit onto that spider land on the HPM frame. You also have to cut out the inner diameter, as it comes with about a 1.5" ID originally.

https://www.matelectronics.com/audio/speaker-replacement-parts/speaker-spider-180mm/

It's a little stiffer than the original- but not enough to cause audible harm to the bass response. I'd say it's on the stiffer end of the "C" stiffness range, comparing it to the spiders from MWA.

IIRC, the 12" foam-edge ribbed-paper cone from MAT is a little shallower than the shallowest 12" foam-edge cone from MWA. Might be worth ordering a pair of those, to see how they fit, once the voice coil opening is cut out.

https://www.matelectronics.com/audio/speaker-replacement-parts/12-paper-cone-with-foam-edge/

Regards,
Gordon.
 
Last edited:
spkrdtr said:
MWA does not carry flat spiders with 2.65 inch ID. Is that the voice coil OD? 2.618 OD is fairly common I.D. which would put the OD about where what you are looking for.
Click to expand...

Yes, coil OD. It's about 2.575" OD on the former, about 2.640" OD on the wire. I'd be willing to tinker
with the ones you mention.
 
GordonW said:
There is a cup spider available from MAT Electronics, that's big enough to be cut down (cut off the "cup" sides, leaving as much flat diameter as possible) to a flat spider, and fit onto that spider land on the HPM frame. You also have to cut out the inner diameter, as it comes with about a 1.5" ID originally.

https://www.matelectronics.com/audio/speaker-replacement-parts/speaker-spider-180mm/

It's a little stiffer than the original- but not enough to cause audible harm to the bass response. I'd say it's on the stiffer end of the "C" stiffness range, comparing it to the spiders from MWA.

IIRC, the 12" foam-edge ribbed-paper cone from MAT is a little shallower than the shallowest 12" foam-edge cone from MWA. Might be worth ordering a pair of those, to see how they fit, once the voice coil opening is cut out.

https://www.matelectronics.com/audio/speaker-replacement-parts/12-paper-cone-with-foam-edge/

Regards,
Gordon.
Click to expand...
Seriously good prices... I will keep those in mind if the cones I have won't work. It looks like they
will. They're rubber surrounds, and I've already trimmed them a bit to fit the frames. I'll come here
first before I order stuff next time.
 
RxDx said:
Further measurements: the new cone sits 4 mm closer to the magnet than the
original. I'm thinking about adding a shim at the surround. Otherwise, I'd still have
to cut whatever spider I use.
Click to expand...

There may be a way to make this work better.

If you use the MAT spider cut to flat, as I mention above- you can trim out the cone opening a little larger than the voice coil, within reason. Cut the opening larger, ONLY to the point where the cone opening lays flat on the top of the flat spider, without pushing down on the spider. You want uniform contact all the way around the cone opening, but not downward pressure on the spider. Cut the spider to fit tightly onto the coil- install the coil and spider into the frame and glue them together- then place the cone on top of this, and use glue (epoxy or superglue with accelerator spray) to fill in the gap between the cone opening and the voice coil (so that the glue ties the cone, the spider and the coil together). As long as you don't have to make the cone opening more than 1/8" radius bigger than the voice coil diameter (i.e, there's less than 1/8" of gap to be filled by glue, between the cone opening and the voice coil), it should work just fine.

You need to use THICK glue for this. If not- if the glue is thin and watery, the glue can seep through the spider, and run down the outside of the voice coil! If this run-down happens, it pretty much TRASHES the whole assembly- you have to pull it back apart, clean out the glue run-down, and start over with a new kit (i.e, you have to buy all the parts again). Epoxy works well for this, as it's pretty viscous.

I KNOW this approach works, as I've done it MANY times. Also- there are many factory recone kits (kits for vintage EV speakers, such as the 12L and 15B come to mind) that have the cones cut larger than would be, for a snug fit on the voice coil- they lay down on the spider, and you fill in the space between them and the voice coil. If it works for EV and the like...

Regards,
Gordon.
 
RxDx said:
Seriously good prices... I will keep those in mind if the cones I have won't work. It looks like they
will. They're rubber surrounds, and I've already trimmed them a bit to fit the frames. Voice coils look
identical to original.
Click to expand...

I'm not sure about how well rubber surrounds will work in a HPM900. The heavier weight and greater acoustic damping of rubber, may limit the upper frequency response of the woofer. Especially if the cone is heavy itself, and/or has a shiny coating (more weight) on it too.

A foam surround and lighter cone will allow for more high-end extension. For an HPM900- where the woofer was allowed to go as high as it can (no LP on the woofer, in the crossover- they didn't want to take away from the HF response of the woofer), you don't want to cause a response "hole" by causing the woofer to prematurely roll-off in the upper end of its range...

IIRC, that MAT cone is very close in weight and damping to the original HPM cone...

Regards,
Gordon.
 
Now- it's extra work- but it should be possible to peel off the rubber surrounds from those cones, and replace them with foam, before installing the cones...

As long as the cone itself isn't stupidly heavy, that should work.

Regards,
Gordon.
 
Excellent! Keep 'em comin'. The crossover is done- we're just waiting on the woofer
to get its act together for the next high noon shootout. These are sitting on KLH Model
Ones ATM.

Still holding out for the surround spacer so I don't have to widen the cone at the VC :-)
 
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