What size are the screws in a 902-16

[argieX]

Hi.

I just traded some speakers for a pair of 902-16?s with some small square looking mantaray horns.
The horns are mounted to the driver with small screws.
I want to use these drivers with some other horns and need some longer screws.
Being located in Denmark I have a hard time finding the right screws.
Looking at the technical specs from Altec it should be 1/4 inch studs.
But this is to big.
Did Altec make any 902?s with 3/16 inch threads in the drivers ?

[bowtie427ss]

I mistyped #12 in my previous post and cannot edit, Please disregard anywhere i used #12 it should indeed be #10. If you have a way to estimate or measure, a number 10 screw maximum diameter is .189-.190 inches, and 3/16= .1875 inches.

If you're measuring the screws at 3/16 diameter, they're likely 10-24.

[Earl K]

- Both 3/16" & 10/24 machine bolts will screw into the threads that are tapped into the faceplate of the 902 .

- Just be aware that at the bottom of the tapped receptacle / is the magnet slug . Since the magnet is ferrite it's easily cracked.

- One doesn't want to over tighten and as a result, bear down too much on the magnet / otherwise you risk cracking it .
- So, when using over-length bolts one needs to have a good supply of washers to take up the slack.

- Emulating Altecs' approach is the safest way to avoid this issue / it means getting extra length bolts and cleanly cutting off the heads.

- Then the bolts can be handtightened into the driver first ( as was originally intended ) before adding the horn and fixing-tightening down the nut .

<> Earl K

[argieX]

Thank you guys.

The thread is definitely not metric, that is what we use here in Denmark, and both 5mm and 6mm don?t fit.

I?ll see if I can get some long 3/16 and cut the heads off.

/Kim

[bowtie427ss]

For SAE thread dimensions the next step smaller than the 1/4-20 studs/bolts commonly used would be 12-24 equating to a number 12 screw guage and thread pitch of 24 per inch.

It's a pretty significant jump from 1/4 down to #12, if the screws in question are only slightly smaller than 1/4, they could be metric, perhaps 6x1 or 6x1.5. 6mm is a little smaller than 1/4 inch.

[argieX]

I have taken a picture of the screws to make sure I get the right ones.

There is also a couple of pictures of the horns.





I?ve got a mail from the very friendly guy Reed G. Hinton, he offered to pick up some screws from this place: www.fastenal.com

But I?m still not sure which ones fit.

The hole depth on the driver is about 3/8, so the overall thread lenght of the screw should be about 1"-1?".

He suggested these:

http://www.fastenal.com/web/products...99944867&Nty=0

Will they do allright, they look very short ?

[bigjunglejim]

Hi there
I'm sure you can get what you need from Bill at Great Plains Audio. Here's a link; http://www.greatplainsaudio.com/

I have 20 Altec MR-902-16HF like yours. Here's a link to an Altec brochure page showing the tweeter; http://www.lansingheritage.org/image...pro/page05.jpg

I bought mine from Stan Miller of Stanal Sound. He used them above 7K.

I'll post a couple pictures showing 16 of mine in use.

[argieX]

Thank you for the link Jungle Jim, now I now why there is a 6uF cap. inside the driver.
I will remove that and use it with a proper crossover.

I received some 10-24 setscrews from Reed, but they are s bit smaller than the original screws.
It is no problem as they screw right in, and I can tighten the nuts to hold the horn firmly in place.
But what is the correct size ?

Here is a picture of the original screw and the new setscrew:


Thank you all for your help, especially Reed who where very kind and picked up some screws and sent to me.

[bigjunglejim]

If you still have trouble, let me know. I'll check one of mine and get a few screws for both of us.