fostex new speaker; & treatment of a coral flat 8

[BTW]

Hi, Haven't read this thread for a while... Something's not right.. The Flat 8 has very decent bass.. and BR works well enough.. Can you double check your phase ie the plus and minus teminals again.. is one of them reversed.. also try reversing the phase the spks might be wired out of phase at the moment..

 

[then_dude]

i don't think it is the phase, cause i have heard them one by one

it might be something very obvious,

the front panel isn't glued, it fits very tight in the speaker, but probably air is leaking out there, so i guess is should glue it first. if that doesn't work i gonna build the smacks, but first things first:glue the speaker and seal it completly of.

it does makes sense, doesn't it ?

i have also looked at the specs at eastmarine drive
the speaker with an f0 of 50hz is

80*55*40

while mine is only

80*30*30

probably it is a bit to small. (it's f0 will be around 65hz or so,still i should hear it better).
anyway, the enclosure is abit to small. that's the feeling i got when i listened to it.

 

[then_dude]

hello it's me again


i was looking at my speakers, and was wondering why i don't hear any bass ou t of the corals.

i pushed the cone of the corals a bit back, and noticed that it is quite hard to push the cone back, it feels like the suspension is quite stiff ;if i compare it with the fostex, it is a difference of day and night. so i'm gonna run 50hz tone through it and see if it gets looser. I think the suspension is gotten stiff over the years. can anybody tell me if this story could be true ?

thanks

 

[BTW]

Yes, it's possible that the cloth suspension has harden over time.. good idea to run the 50 Hz tone.. Try this first and see if it gets better..

 

[planet10]

it's possible that the cloth suspension has harden over time...

Stiff Suspension Syndrome. I've not yet found a way to reliably reverse it yet.

dave

 

[then_dude]

thanks guys, i really think this is the issue with my speakers.

so there is nothing to do about ? put a new suspension on ?

may i ask what you have already tried planet10 ?


thanks

 

[planet10]

Finding inverted cloth surrounds could be hard.

I've tried all sorts of solvents. The one suggestion i haven't tried is a solvent + oil. The oil to suck up the gunk after the solvent has loosened it,

dave

 

[Cal Weldon]

Is the problem with a stiff suspension likely to be the surround or perhaps the spider as well? If so, could you use an emulsified oil like Dave is suggesting whereby the solvent is a catalyst to speed the penetration and the residual oil to soften the flexibility long term?

 

[then_dude]

well that's sounds very profi.

i need to apply a solvent on it,
and then apply some oil on it, to suck up the gunk ?
what gunk would that be ?

what is things go wrong ? would it be better to put in a new cloth suspension, although i understand that is is quite difficult to do so.

thanks dave

oh somebody posted a message while i was typing.
so the oil and solvent must be mixed, but what kind of oil and solvent are we talking about,
i wanna try it. otherwise the corals are good for mids, in a 3 way

 

[Cal Weldon]

All spiders and surrounds are treated with something. This something can collect gunk over time and sometimes this will stiffen it. They will also undergo a gas-off meaning whatever solvents were originally in the treatment will be less, creating a stiffer cone movement well. I don't know if you have to remove anything, planet10 is more an expert than I, but you will have to create freer movement, hence the use of an emulsified or thinned oil. Just like most anything mechanical, it requires lubrication, in this case it's the lubricating of the fibers in the surround and spider.

 

[Cal Weldon]

What about penetrating oil and mineral oil mixed?

 

[then_dude]

thank cal, that is some very logic explanation you gave me.

not only the the suspension but also the cone itself is quite hard. i know a cone should be hard, but compared to my relative new fostex fe167e (5 years or so): the fostex has this sticky oily feeling, the coral feels like perchament.

i do think my suspension has collected some dirt, you can see it, the back of the speaker is nice white, the outside is yellow (same for the cone)

 

[then_dude]

i have let it play 12h at 20-50hz

but the suspension didn't loosen up, the suspension is really hard, so i'm in for a little oil treatment.

Dave can you help me out on this ?

and is there a forum where they try to fix old paper cones and drivers ?

thanks

 

[planet10]

Anything you do is new territory. The most effective solvent i used was acetone (make sure you use in a well ventilated room (or better yet outside)). I was going to start with a synthetic motor oil of some sort.

dave

 

[then_dude]

thanks dave,

i just wanna get a little bit understanding what i'm doing.

is there an article or a post about this ?

acetone is typicly a degreaser, so i should mix oil with acetone ? is it to disolve the oil a bit, that it becomes more liquid ?

and how much do you have to apply on it ? what if it touches the glue between the suspension and the paper cone ? will the paper cone not be disintegrated ?

thanks a lot
greetz

 

[planet10]

As i understand it, the oil is to act as a holder for the stuff you are trying to remove from the surround (my thinking is that the old stuff comes out and you re-treat if necessary -- cal's idea of revitalizing it is new & interesting slant on things)

dave

 

[then_dude]

i have been looking around at vintage speaker fora, but didn't found what i'm looking for. i'm a bit reluctant because the acetone looses up the glue and i don't know what glue has been used on the corals.

but you should wipe off the oil afterwards ?

i have to mix the oil and acetone ? how much of each ?

thanks dave, and thanks to anyone who knows something about it

greetz

 

[planet10]

As i said, i don't know, we are on ground i have never covered, I do thou have at least a dozen cheap sacrificial corals with the same problem, when i get around to it (maybe when the weather starts getting warmer) i don't have to worry about destroying important drivers to find out.

dave

 

[Cal Weldon]

Personally I would be concerned about acetone. It may be "too much" of a good thing. Mineral oil is rather harmless as is penetrating fluid because it flashes off so quickly. I would apply it with a cotton swab or small paint brush while the driver is in a vertical position for the spider at least. This will prevent bleed through and coil contamination should you apply too liberally.

 

[then_dude]

thanks guys,

i don't have the impression that the spider is stiff, (i must check this)
but the suspension is rock hard compared to the fostex.

i was planning to use a cotton swap and horizontal postion of the driver (i mean put the magnet on the table. and then add some oil.

i thought first to swap a bit with acetone, a bit (with a cotton swap) it vaporates fast, so that is a good thing. afterwards i would apply a bit of oil to grease it a bit.

i have registered to a vintage speaker forum, i'm gonna ask the same question there, maybe they know some tricks;
i'll post them here.

thanks again