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View Full Version : changing the diaphraghm on a 2445 or 3446J assembly using the D8R2450 diaphraghms NOS



lgvenable
03-28-2011, 08:57 PM
how hard is this, is there a tutorial, and do I need a titanium (or belyerium) screwdrivers to have it nonmagnetic, if so what size as those dudes are expensive; I've found a Ti set by the piece out at Ampco saftey products; with prices per non sparking non magnetic driver at 25 to 35$


I'm planin on installin D8R2450 dias NOS 8 ohm drivers into my 2446 and 2445J systems whic currently have 16 ohm drivers.

Anyone know a better source....same tools used to work on magnetic systems in MRI's...And id there anyone willing to write a walkthough porocedure? Finallu do i get the #3 pgillips etc; what size head and shape do I need in titanium so I don mark the ne dome from the poull of the magnetic on the steel in the tool??;)

1audiohack
03-28-2011, 09:14 PM
They are #2 Phillips head screws. I have never had non magnetic screw drivers and have never had a misshap. The pull is not very strong until you get very close to the gap, inside the black plastic ring close. If you have good dexterity and a driver that comfortably fits your hand with a fixed shaft (no interchangeable bits) just be carefull and you should be fine. When you have the diaphragm out, experiment with the magnetic pull versus proximity, just don't put a nick in the top of the gap.

more10
03-29-2011, 04:17 AM
The gap is a bit wider where the leads to the coil should go.

Eaulive
03-29-2011, 06:16 AM
a driver that comfortably fits your hand with a fixed shaft (no interchangeable bits)

I wanted to enhance that :D

lgvenable
03-29-2011, 09:19 AM
I wanted to enhance that :D

Well a piece of luck. At work we use beryllium-copper tools in our mixrooms (non-sparking non magnetic), and it turns out I can bum an S-1099 Ampco phillips head, which is the correct driver for the phillips #2 used in the diaphragms.

I wanted to err on the side of caustion and use a non magnetic screwdriver, having seen numerous dings on diaphrams from the use of a ferrous screwdriver. Given my luck, I'd ding a diaphragm; and since I'll only do this one time in my life; as I change the diapragms from 16 ohm to 8 ohm, I wanted to be sure not to dng them.

Stupidly these drivers cost like $50 each, so was I ever glad when one of our mechanics pulled the driver out of the bottom of a storage box to let me use for the task. A full set was even better at $186. I caould just have seen Carla's face when I said I needed a $50 screwdriver for about 30 minutes.

One thing you guys didnt mention, will I need to align the coil?, is is self aligning? Do I use poly shims? Or are there detents where it will only fit into the right orientation?

Thanks.

more10
03-29-2011, 09:48 AM
2445 Diaphargm Buss Help (http://www.audioheritage.org/vbulletin/showthread.php?30616-2445-Diaphragm-Buzz-Help&p=307652). Just a few threads below yours :-)

I have not done this properly myself, but it makes sense. Use a tone generator, sweeping the driver with horn mounted but not back of driver. Tighten the screws a little at a time. If it works without any buzz your are done.

more10
03-29-2011, 09:49 AM
At work we use beryllium-copper tools

I have been looking for non magnetic screwdrivers, but these are hard to find. You got a brand name for these?

maxwedge
03-29-2011, 07:58 PM
I have been looking for non magnetic screwdrivers, but these are hard to find. You got a brand name for these?
Titanium here>http://www.qualitysafetytools.com/index.php?app=ccp0&ns=catshow&ref=Titanium_Phillips_Screwdriver&sid=9g5g842csn4552l177k170yk7087wo74

I haven't invested in any yet but I just used a regular #2.

WDJ
03-29-2011, 08:02 PM
Snap-on sells non-magnetic blades for their screwdrivers.

http://buy1.snapon.com/catalog/item.asp?item_ID=74297&group_ID=19567

If you can wait, you sometimes find the old Craftsman stainless sets on ebay. I haven't seen a set in a store in years.

Wiha (www.wihatools.com (http://www.wihatools.com)) has non-magnetic tools too.

lgvenable
03-31-2011, 06:52 PM
Go to Ampco. Forget Ti its too soft for long term (for me). Use the industry standard: Ampco Safety tools
http://ampcosafetytools.thomasnet.com/category/screwdrivers?plpver=10

These are non magnetic, and are used in MRI installations;). We use them at Alcoa in our H2 rooms, where we rollcoat solvent borne can coatings. You cant generate any sparks as you'd quite literally make an ash out of yourself.

I took the driver home, laid a standard ferrous scrwdriver on my 2446 top....stuck like glue. Placed the Ampco BeCu screwdriver on the magnet structure...it fell away. Completely non-magnetic. For the the 2446 diaphragm use the S-1099 its a Phillips #2.

More10 thanks for that, I think I saw that but duh, it went right by me. Thanks for the pointed advice! Here's hoping my diaphragm for sub-woofer swap with another member goes down, as I'll be stoked to get three new 2445/2446 8 ohm diaphragms. Maybe Truextent one day, not today though....

Harvey Gerst
03-31-2011, 07:16 PM
Cup your hand around the black phenolic ring (open cup) near the screw you're working on, so that the screwdriver fits against your hand; your hand prevents the screwdriver from slipping onto the dome.

That's how we did it at JBL in the 60's.

lgvenable
03-31-2011, 10:34 PM
On non magnetic drivers:
With the Ampco driver it has no magnetic attraction at ALL it should be easier to use them to attach the 8 ohm diaphragm w/ gouging .The S1099 is the same size needed for the adjustment using #2 phillips screws. I'll pull out my tone sweep and call 1audiohack to get these diaphragms ino 8 ohm installed correctly.

So I get to say hello to 3 sets of 8 ohm dr2450 8 ohm kits into my three 2445/2446J @ 16 ohm converting them to 8 ohm varants (hooray!!)

SO I'm hoping I watch JBL4EVER disappear with my double box-in- a -box made-walnut vennered box weighing 238 lb It was designed to match L100T styled 2245H sub-woofer and porttuned 24.79 Hz.zoh and 600 to 750 wpc 8 ohm continuous!!

Hey the repair of my 2446 horns at 8ohm will create brand new NOS driving the mids 2446-2360's at 8 ohms>>I'm stoked, delivering perfect performance in my theater JBL Pro drivers
Right after receiving the AB Systems 713A's back from service in California at Precison Electronics, the home company of AB Systems.

as the amps three AB Systems 713 monotriamps deliver:
500 wpc 8 ohm :eek: to LF 2206H bass drivers,
250 wpc 8 ohm :eek: to Mid Frq 2446J (now H) w2360 horns Too Cool!:D
250 WPC 8 ohm :eek: to HF drivers 2404H all at 8 ohm

These same amps drive the Smithsonian National Air and Space theater with seven mono-tri-amps running at 8 ohm impedance.The rebuild of mine will rid of the potenially poor mismatch performance with mixed loads at 8 and 16 ohm ampplifier sections,as well as replacement of every capacitor needed to return brand new bass performance!

AB Systems 713A amp links??
http://www.abamps.com/productarchive.html#713a

The Smithsonian National Air and Space Museum Theater uses 7 x 713A. I use three now and perhaps 2 more after negotiation with a friend.

John
03-31-2011, 11:10 PM
Cup your hand around the black phenolic ring (open cup) near the screw you're working on, so that the screwdriver fits against your hand; your hand prevents the screwdriver from slipping onto the dome.

That's how we did it at JBL in the 60's.

Sounds like a good tip Harvey.:bouncy:

I would like to add, I once made a stupid mistake, never lost control of a screwdriver but once dropped a screw from a height that was able to put a nice sharp ding in a otherwise mint diaphragm.:crying:

Harvey Gerst
04-01-2011, 10:50 AM
Well, we never lost a diaphragm in the 8 years I was there.