First Refoam Problem

[pauvro]

Hello,

Awhile ago I got a good deal for a pair of Cerwin-Vega VS-100's. These were the best speakers I had ever owned and I enjoyed using them. It didn't take long before the original foam started to crack and come apart, causing the sound to get worse and worse until I just couldn't use them anymore.

Anyway I decided to get a refoaming kit. I watched a video addressing how to complete the refoam, read up on some information, then jumped on in. I'm not quite sure what went wrong but now I have one speaker that sounds good (can't hear any sort of rumbling or distortion anyway) and one that rumbles and rattles on low frequencies, it's quite annoying.

Initially when I recognized this sound I kept trying to locate it. Thinking it was the dust cap, I removed it and attached a different one, and put the speaker back in the cabinet. It seemed to work initially without any distortion, but the issue soon came back.

When I refoamed these, it was admittedly a little stressful. Scraping the original foam off was quite tedious, I did manage to get a decent amount removed to make it feel flat then I remember when gluing the inner edge of the surround the surround itself didn't seem centered on the frame but I heard that's to be expected. When I went to glue the outter edge I couldn't get some of it to actually adhere due to the fact that it wasn't fully fitting the frame. I did everything the way it was said to be done however I did rush it a little when I did the second one...when it came time to "center" the voice coil all I did was use the shims that came with the kit and places them at a 12, 4, and 8 o'clock position. That's the extent of what I did with centering it and I'm not quite sure I would know if that were the problem or not...like perhaps somehow it became uncentered...even though I used shims?

My question is given this information, what should I do to fix this problem? What information, if any, do you need from me to help figure out how to fix this problem.

Thank you for any help.

 

[grillebilly]

I can't see how you went wrong if you used shims. The dustcap does nothing more than shield the VC from the elements. The only thing I can think of is debris may have entered the VC area and is causing the distortion. If you gently push down on the cone, can you feel any rub? Double check your connections and switch the speakers to make sure the speaker is the problem.

 

[pauvro]

When I push upon the top of the cone, about halfway between the dustcap's end and the inner rim, it makes a noise as if it's rubbing against something.

 

[turboyam]

Voice coil centering... You should re-do the operation with a new surround and
take your time!.

 

[sb001]

When I push upon the top of the cone, about halfway between the dustcap's end and the inner rim, it makes a noise as if it's rubbing against something.

That sounds like you're pushing the cone at a bit of a downward angle, even if you're pushing straight in at that one location, which might cause a rub even if it doesn't in normal operation.
Do you get a rubbing sound if you push the cone straight inward, like putting your fingers evenly around the dustcap and pushing inward?

 

[pauvro]

I'm confused about what I did wrong though because the only step in my instructions concerning the voice voice was to place the shims in. I did that, so how am I to do the operation differently to ensure success? Are we even sure it's the voice coil? I'm actually getting more confused now because I just pressed upon the cone of my working speaker and it makes the same rubbing noise at the bottom of it...am I exaggerating that to happen or is there a real problem? And if it's a real problem, why does my one speaker sound fine and the other rattle so much. Like the working speaker I've played samples from this site http://goodhifi.com/Samples/Samples.htm and it sounds fine, where as the messed up speaker sounds very buzzy/rattling sounding.

Thanks for any help!

Do I really need to buy another set of surrounds? I used heat to loosen the glue bonds with the dustcap, could I do that with the foam surrounds? If not I don't know when I'll want to try refoaming again because I'm not trying to shell out another $40

 

[pauvro]

That sounds like you're pushing the cone at a bit of a downward angle, even if you're pushing straight in at that one location, which might cause a rub even if it doesn't in normal operation.
Do you get a rubbing sound if you push the cone straight inward, like putting your fingers evenly around the dustcap and pushing inward?

Thank you for your response. When I press how you describe there is no noise what so ever. So what would be your next course of action if it seems it isn't indeed the voice coil?

 

[Imme1956]

it is possible to stretch the foam on one edge when gluing it so that after you remove the shims, it pulls to that side. This is why I usually use a battery to check before allowing all the glue to dry..it helps keep the voice coil centered.

 

[pauvro]

it is possible to stretch the foam on one edge when gluing it so that after you remove the shims, it pulls to that side. This is why I usually use a battery to check before allowing all the glue to dry..it helps keep the voice coil centered.

I did stretch it a bit, and ended up attaching the rim down earlier that instructed because the glue wasn't setting the outter rim down to well because it seemed a tad small, however I am not getting a rubbing noise pressing upon the center of the speaker, inward...so what do we think moving forward?

Thank you

 

[Brian]

No way of telling. Try doing a battery test to see if the noise is present. Using your fingers to push the cone puts uneven pressure on the cone so you may be masking the problem by using that method. Also, agree you may have dried in some contaminants into the gap or if there is ferrofluid, it may have dried up somewhat and it is moving the vc. Another possibility, though unlikely, is whether the leads from the vc to terminals are in some way interfering.

There is only so much that can go wrong as the speaker is a relatively simple,easy device.

 

[sb001]

I did stretch it a bit, and ended up attaching the rim down earlier that instructed because the glue wasn't setting the outter rim down to well because it seemed a tad small, however I am not getting a rubbing noise pressing upon the center of the speaker, inward...so what do we think moving forward?

Thank you

I don't suppose it's simply loosely mounted in the baffle is it?

 

[TPettenati]

Before doing your surround again, try this. Unscrew the speaker and rotate it 180 degrees and re-install it. In other words if the connectors were at the top before they will now be facing the bottom. The suspension tends to sag with age toward wherever bottom was. Sometimes this will give you just enough clearance to fix the rattle. May work, worth a try.

There are a few different ways to center the coil when refoaming. Without removing the dustcap you could try the 1.5V battery method or the 30 Hz tone method. I've done both with success. Search AK for details.

Good luck and don't give up.

 

[-reverb-]

Sounds like you did everything correctly. Sometimes you just have a problem speaker. Oddly enough, my first refoam problem was with a CV woofer as well - which is odd because they are one of the more forgiving ones to refoam.

It turned out that I did nothing wrong and the popping noise I was hearing at volume was because the glue holding the front baffle in place was not doing it's job and was allowing the baffle to move slightly when the volume was high. The result was a popping sound.

By process of elimination you can swap the woofers and see if the problem stays in the cabinet or goes with the woofer. Likely it will travel with the woofer but you never know.

If you used white glue like Aileens, you may can roll up a paper towel and get it slightly damp. Lay it around the edge of the woofer where the foam glues to the basket (may take 2 towels depending on how big the woofer is). Let it sit for a while and the glue will loosen-up. GENTLY! Lift the foam away from the basket being careful not to stretch or tear it. If you can get it removed from the basket, you can reuse the foam and save yourself a few nickles. Personally, I use a tone instead of shimming. Not saying that's wrong or right, it's just how I have always done my refoams.

Main thing is don't get discouraged. It's not a hard process but sometimes little snags happen.

Good luck!

 

[GoRNR]

I'm not familiar with the C-V drivers, but is it possible the spider is weak and the cone has become too loose at the spider support, and the VC is rubbing from a weakened spider?? Rotating the driver for mounting may help determine if the spider is weak.

Nonetheless, good advise from previous posts regarding attempting to carefully loosen the surround and attempting to re-center the voice coil.

Try to stay with it using patience and some care. You can fix the driver. :yes:

 

[vinylisfinal]

i scrape the frames with an xacto flat scrape blade. i also do not use shims. i use either a low hertz test disc or audio with a lot of bass at low volume. using a sound source has given me 0 failures. i have refoamed over 500 woofers and haven't looked back

 

[loose ends]

Well, if it didn't rub before than chances are it's something you did. That's a good thing in this case because all you have to do is refoam and this time do it right. First buy good surrounds. Personally I use Rick Cobb. Usually I don't need glue and the cd so I get a little break. I use the 30Hz tone. I use 91% alchohol to remove the surround from almost all cones easily. I cut the hairs on an acid brush to about 1/4" long so they will flow the alchohol and also allow me to scrub the old surround area. Keep it wet (about 2 times around without stopping. You can then take a dull single edged blade and carefully scrape what's left. On the frame you just have to scrape. You will have an area on the cone that makes it easy to see where to apply the glue. Attach the surround to the cone again using this darker area this time to align the surround on the cone. Let it dry. Then play the tone through the speaker and glue the outside to the frame. You will have to attend to both gluings until the glue sets.

After you shimmed your voice coils you must clean the gap. Business card strips with tape. All it takes is one little piece of dirt. That's why I never remove the dust cap. Also if you do pull the surround in one direction to get it to properly attach to the frame when you remove the shims you will have voice coil rub. You can download a tone on the internet.

I think you'll get it right.

 

[moebuster]

i've found that when working with older drivers that the spiders tend to sag over time
and the method that works for me is to glue the surround to the cone and after it is set-up/ dry them apply the glue to the basket and lift the cone/ surround and let it find
its center, regardless of whether the surrounds outside edges appear centered around the circumference of the basket.
then with a "centered" hand or hands press the cone through the voice coils stroke to check for scrapping.
make slight adjustments to the cone/surround, recheck.
check again in 5 minutes. this method is when using Aleenes

 

[mech986]

 

[sax6]

Please try the '' rotate the woofer 180 degrees '' first.

I'm pretty shure it'll work!

 

[mars_volta]

I would advise AGAINST using a battery if you are new to this.

Did you take any pictures of the process? Sounds like something went wrong with the shims.