Paper Cone Strengthening

[AndrewT]

Hi Paul,
it looks like about 30% to 40% of total Cone area.
This would reduce Sd by the full 30% to 40%.

 

[paulspencer]

Andrew, I don't think it would. I'm assuming that the cone extends below the spider and that the spider would in fact act like a grille absorbing a small amount of high frequencies.

 

[AndrewT]

Hi Paul,
you have make a valid observation.

Maybe the answer (effective Sd) is somewhere in between.

What kind of shape will the spider adopt if it is being pushed/pulled by air pressure from behind, dragged by the cone at it's periphery and held still by the pole at it's centre?

I guessing but would the volume behind the front spider be vented to the back through the voicecoil/magnetic poles gap?

 

[tinitus]

When the driver goes back and forth the spider "drags" sidewards in cone - if you could weaken spider it might help a lot

 

[paulspencer]

Andrew, I don't think the change in volume enclosed by the cone and front spider is going to change much with excursion, partly because this is not a very high excursion driver. Further, air can pass through the spider itself. If large excursions were involved and the spider was airtight, this would be different.

I'm currently modifying my Vifa P17 6.5" midbass drivers. When I pulled off the dust cap, I was surprised to find holes cut in the VC former. They are needed to vent the air behind the dust cap, but with my new phase plug modification, they aren't quite so desirable. If they were in a sealed box and not TL, then it might be more of a pest!

 

[montreal]

could the pin hole in the rib be for a method of holding the rib in a jig while the glue sets?

That makes more sense to me than my original idea that it had something to do with equalizing the air presure of the cavity created by the rib.

Undoubtedly the four ribs were glued on before the cone was mounted in the frame and it would have been hard to position the ribs by eye only.

 

[ttvonau]

I ended up having to connect my test FU15-4 to a wall plug before I could get the cone to fail. It ripped along the surround meets cone area as most suspected.

I used fiber tape and an automotive grade clear coat to attach a series of strips from inner spider to surround.

Cone is now more linear and can not tear. I have entered three events since modding cones and have only lost 1db from 146.2 to 145.2.
Although the 145.2 was accieved with a much smaller amp.

Thanks for your input and I will post pics if theres any requests.

I am looking for new crazy ideas for next years enclosure please check it out, use your imagination and post.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1013633#post1013633

 

[moray james]

Foam plugs?

have you considered a closed cell foam plug that fits into the cone glued into place with a stiff skin on the face. Numerous craft foams are available that are very low mass. Regards Moray James.