Which 30Hz tone to use?

[Tonkatoys]

often,when I read thru threads on refoaming/reedging speakers, the authors will reccomend using a 30Hz test tone to square the voice coil. Question:
Should I use a 30Hz sine 1 frequency or 30Hz square 1 frequency? Both are available on the free download "NCH tone generator". Thanks for the help.
John

 

[ferninando]

sinewave.

 

[tuttle]

I was wondering this very thing. I have used batteries in the past,is the tone generator better/safer ?

Thanks

 

[BmWr75]

I was wondering this very thing. I have used batteries in the past,is the tone generator better/safer ?

Thanks

6 of one, 1/2 dozen of the other. A "AA" battery holds the cone still, which might be an advantage.

 

[tmad40blue]

Use a 30 Hz sine wave tone. Safer than a battery.

 

[BmWr75]

Use a 30 Hz sine wave tone. Safer than a battery.

What is unsafe about using a 1.5 V AA battery? Not being a smart ass, just curious. I've use this technique to refoam probably 10+ sets of woofers and they all turned out great.

 

[Gtyler]

Really you don't need to have either. Just use your hand to press down the cone slowly. As long as you don't push it to one side you will be able to feel if there is any contact. You can also press the cone down and then release it and listen. This is the way that I always do it and I have never had any trouble. It's also quicker. I find that if you take the time to connect your speaker and play a tone though it, the glue has already started to dry slightly and is more difficult to move.

If you do decide to use a tone, use the sign wave and have it all connected and ready so you will be able to play the tone as soon as you have your glue in place, and do any necessary repositioning.

Good luck!

 

[Nat]

Gtyler - your glue must dry faster than mine -- I always have plenty of time, too much in fact most of the time. But maybe I need to wait longer for the glue to get really tacky before sticking together. Nice avatar by the way.
As to sine or square wave, and AC or DC -- square waves have lots of other frequency content -- that's how they are square -- so its hard to guess what effect that might have on the amp or the speaker. And there is no reason to use them, so sine waves are the obvious choice. The problem with using a battery -- DC -- is that you have the heating that comes from current flow without the cooling that comes from the voice coil moving back and forth. So there is some chance of overheating the voice coil, if its a really wimpy speaker, or a big battery. But I agree that with a 1.5 volt battery (particularly the partially dead ones I find around the house) there isn't any real danger. I don't think.

 

[Horn Head]

Forgive my ignorance, but aren't VC shims a bit more simple to use for good results?

Always wondered why folks used the tone method. May try it some day to see what all the hubbub is about.

 

[BmWr75]

Forgive my ignorance, but aren't VC shims a bit more simple to use for good results?

Always wondered why folks used the tone method. May try it some day to see what all the hubbub is about.

You don't have to remove the dust cap if you use a tone or AA battery. I'm always leery of taking an exacto knife to a dust cap for fear of cutting the cone.

 

[Nat]

And if you are sloppy, its possible to cut the voice coil wires where they pass under the dust cap seam. To say nothing of the possibility, again, if you are sloppy, of something getting in the voice coil gap.

 

[riker1384]

How reliable is this 30 Hz tone method? I have some JBL woofers I'm thinking of refoaming with a kit that uses it. I'd prefer not to have to cut the dustcap for cosmetic reasons, but I don't want to mess things up.

 

[Gtyler]

How reliable is this 30 Hz tone method? I have some JBL woofers I'm thinking of refoaming with a kit that uses it. I'd prefer not to have to cut the dustcap for cosmetic reasons, but I don't want to mess things up.

It's really not as hard as you may think. Just be careful and make small adjustments. As I mentioned before, I personally think it is even easier to just use touch. Just place your fingertips on the cone and press it down slightly. if you hear any rubbing move the cone up and down while applying a bit of lateral, and change the direction of that lateral pressure until the rubbing stops. When the rubbing stops, then you know that is the direction that you need to move the surround. Move the surround slightly in that direction and then repeat the process. It is very simple and I have never had a problem.

Another little tip that I have found very useful is to go and get 10-20 very small neodymium magnets. Once you have your surround in place, position the magnets all around the surround so that it holds it firmly to the basket. This makes it easier to make small adjustments, and holds the surround in place while drying to make sure that nothing happens. I have had very good success with this trick.

Gtyler - your glue must dry faster than mine -- I always have plenty of time, too much in fact most of the time. But maybe I need to wait longer for the glue to get really tacky before sticking together. Nice avatar by the way.

Thanks, that KD-550 is such a good table that I have had a really hard time finding something that will outdo it. In fact such a hard time that it is still my main TT. It really is designed well.

As for the glue, It is possible that I live in a dryer climate of something, but I think what it may be is I try very hard to apply the thinest coat of glue possible without it drying too fast. This makes for a very clean connection, which I think is better. It is especially important when gluing the cone to the surround because you don't want to add any extra mass there IMO.

 

[westend]

How reliable is this 30 Hz tone method? I have some JBL woofers I'm thinking of refoaming with a kit that uses it. I'd prefer not to have to cut the dustcap for cosmetic reasons, but I don't want to mess things up.

Very reliable. I have used it many times and all surround repairs were successful. Thanks to Bo Putnam and LHF, there is a pictured tutorial with step by step instructions. Follow Bo's advice and source your surrounds through Rick Cobb. His surround kit will have printed instructions and the 30 hz tone on CD. He will have the exact surrounds for your JBL's.

Edit: Reread your post and I see you have a kit, already. You're good to go! Another thing in this thread is the stated problem of using a tone. I haven't encountered the problem and maybe it's because of the procedure I use: glue new surround to cone, let dry, wire up driver and start tone, place adhesive on flange of surround ( I use a small paint brush), and press down lightly on the surround to mate it well with the driver frame. If you use this procedure, the voice coil aligns itself and there is little chance for error.

 

[Nat]

Easier to find than neodymium magnets are clothespins (the ones with two wood parts and a spring, not the single wood piece). You have to be careful as you clamp not to pull the surround outward, but you get twenty or thirty clothespins on the surround, and its not going anywhere.

 

[Horn Head]

I usually use a properly sized tupperware bowl with a five pound weight.....to keep pressure on the foam to the frame.

Been lucky since my wife has lots of tupperware.

 

[Gtyler]

I usually use a properly sized tupperware bowl with a five pound weight.....to keep pressure on the foam to the frame.

Been lucky since my wife has lots of tupperware.

I tryed to do this many times, but I can't never find the exact right size! Always too big or too small. I guess I should start buying my wife more Tupperware.

 

[Doug G.]

The only thing I have used the 30Hz tone for is, after refoaming all the woofers in my stacked Advent quad system using the "touch" method, witnessing the drywall in my living room being vibrated against the studs.

It is actually quite unnerving. I hope I didn't damage the building. \:^)

Doug