LE85 Gap Width

[Zilch]

Is the gap in LE85 narrower than 2420?

Some early ones, maybe?

I'm having one DEVIL of a time gettin' a D8R2421 to play nice in this one....

[edgewound]

Gap width in both should be .031" Closely inspect for roundness and high voice coil wires. Sometimes you need to ream out the locating pin holes to give enough play so you can adjust in the gap while applying signal with your sweep generator at 2.83 volts 500-1200hz. Also make sure gap is true all around...but you already knew that

[Rolf]

Is the gap in LE85 narrower than 2420?

Some early ones, maybe?

I'm having one DEVIL of a time gettin' a D8R2421 to play nice in this one....

I ones got a DR16R2421 witch had a little "top" on the copper windings due to bad soldering in production. This made it impossible to enter the 2420. Maybe yours have the same, just a little smaller??

Rolf

[Zilch]

Well, I reamed (thanks, Edge,) honed, cleaned, and swore considerably.

There was a tiny goober of glue on the inside of the VC. (Thanks, Rolf for making me look more closely.)

Even with that carefully removed, the stock alignment was still wrong, tho.

Finally got it close enough to break them in for a week or so before a final "tweak" with RTA. New SS hardware with washers then, probably, to hold it securely.

I'll set up the Mini-Everests with them tomorrow. Johnaec is coming by, maybe. We'll log some hours.

Down a couple of dB around 8 kHz. Low end is good, so they're riding free now, I presume.

Thank you for the suggestions. You gave me the will to persevere. I was about to ship these off to Northridge....

http://audioheritage.org/vbulletin/s...2145#post92145

[edgewound]

Well, I reamed (thanks, Edge,) honed, cleaned, and swore considerably.

There was a tiny goober of glue on the inside of the VC. (Thanks, Rolf for making me look more closely.)

Even with that carefully removed, the stock alignment was still wrong, tho.

Thank you for the suggestions. You gave me the will to persevere. I was about to ship these off to Northridge....

http://audioheritage.org/vbulletin/s...2145#post92145

You're welcome, Zilch. Now you know how frustrating it can be to find that expensive diaphragm replacement operation go sour with less than perfect parts, and the time consumed to make it work to spec. We're trained at the factory for that. But sometimes you gotta improvise to find the solution.

[Steve Schell]

One point that needs to be stressed is that the gap needs to be cleaned really well before fitting or "buzzing in" a new diaphragm. The tiniest sliver of metallic crud that remains will foul up any attempt to attain a clean sweep; it will stand on edge due to the direction of the gap flux and contact the voice coil or former. Every speaker fixit guy has his favorite technique- here's mine:

Start with Scotch double stick clear transparent tape. Wrap a piece around the edge of a business card. Cut the assembly free from the card, creating a "cowcatcher" angled scoop on one side in the process. Run the sticky card, scoop forward, around the gap repeatedly- the scoop will tend to work small pieces of crap up and out. Capture the chunks with the tape as they appear. Make an effort to press the tape toward both the inside and outside edges of the gap. Usually the card becomes darkened on both sides from all the pollution. Repeat with a new assembly, and keep it up until the tape remains clean. On used prosound drivers like 2440s, this process might take 20 minutes. When finished you will have a pile of dirty tape and card pieces, and a very clean gap.

Take a very careful look at the gap all around with a flashlight before fitting the diaphragm. If you see any twinkling metal flakes, go get 'em!

[Zilch]

Thanks, Steve. I made a little "Chip catcher" from a credit card strip. The thickness is full gap width, and it drives the crud to the top.

Also have some aluminum tape that's stiff enough to manipulate in there to snag stuff.

Hard to see in the gap. Thinkin' an optical fiber illuminator might actually get down in the gap to light it up. Gonna check some catalogs for future use. If I find anything, I'll let everybody know.

[johnaec]

I made a little "Chip catcher" from a credit card strip.

Doesn't the magnet screw up the data on the credit card?

John

[subwoof]

Solution: use the wife's card.

In the shop I keep a collection of plastic covers from snacks ( IE: pringles ) for gap cleaning. It has more stiffness than the doubled-up buisness card and some of them allow an electrical tape to be folded over for that deep-down clean feeling.

The locating pin holes rarely allow drop in and I have to also shave the rough outside of the 1 and 2" diaphrams when installing into the 25,45,46. For some reasong the gap geometry or tolerances are better on the 46,50,51, models and it's rarely required.

And then you WILL have the occasional "fighter" that will NOT go into a given motor but will blissfully drop into another....grrrr.....

That is why they are supposed to be installed by a factory trained tech who can use another diaphram in case the first is "off"

Of course when we open and test all the drivers before an install, a full 1/3 of them are NOT aligned correctly.

Makes you wonder sometimes...

sub

[Zilch]

Solution: use the wife's card.

Of course when we open and test all the drivers before an install, a full 1/3 of them are NOT aligned correctly.

Makes you wonder sometimes...

Well, it certainly matters. I've tested enough 1" drivers now to recognize that there is considerable variability.

I'm not suggesting that everyone should go in and tweak diaphragms, but it's certainly worthwhile to perform simple response measurements and try to "match" drivers used in system pairs.

I've occasionally found some "duds" looking at them, too....

[edgewound]

Hard to see in the gap. Thinkin' an optical fiber illuminator might actually get down in the gap to light it up. Gonna check some catalogs for future use. If I find anything, I'll let everybody know.

Get yerself an illuminated bench magnifier. It lights up the whole topplate area and allows you to see debris in the gap. I use 1" masking tape sticky side out folded under a stiff piece shim stock from a Yamaha recone kit.

Don't forget to do a final gap cleaning with acetone, and pick out any little blobs of tape adhesive. Cone style coffee filter paper works great soaked in acetone for the final residue clean up.

[jimd]

Once in a while one finds a iron chip that just won't come out. I use a piece of stripped #22 copper telephone wire bent into a hook and reach down into the gap and pull it toward the top. Once there, I pick it up with the sticky side of a piece of tape. Sometimes I have even had to use duct tape on subborn ones. Lots of good information here. JIM