Making a 416 out of a 421

[les winter]

I'm starting the hunt for parts to build an altec pair for my home theater. I mostly listen to the opera via blu-ray. My main setup is a pair of clone model 19's. GM suggested using similar components for my HT set. So I am on the hunt for parts. Ideally 416's 811b's.

Because I lucked into a pair of $100 Valencias during my Model 19 build, I figured I could build my HT pair for a few hundred. Maybe not. 416's go for $325 or so on the 'bay. New ones from GPA aren't that far behind.

So I started considering 421's. Reconing kits are around $65 and busted 421's go for $24-$50 or so.

I have two questions:

1. any reason I cannot do the recone myself?

2. can I make a fair approximation of a 416 with a 421 reconed with a 416 kit? I notice the magnet on a 421 weighs the same as a 416 but it is not alnico, it's "ceramic ferrimag" per the GPA vintage catalog sheets.

thanks for any advice.
Les

[GM]

Since you'll be using a sub system, you can use the 421 as is except swap out the 'chrome dome' for a 416's dustcap since you need neither the 416's low Fs nor extra Xmax.

GM

edit: you'll need to block off the rear vent also if it has one [can't remember if all models had one].

[Old Guy]

It works. I would use a hard paper dome instead of the chrome...just call bill at GPA he can do it. Or at least use parts he recommends.

I really would recommend getting 418 instead as it converts directly. Or 422, same core. Brother has a single for 25.

421 core is also same as 423.

418's actually work well if you have a sub...I cover the shiny dome with a felt one, bfish suggested vented paper instead....

[les winter]

Thanks guys.
The only thing about the 418 is that the magnet weight, per the catalog cut at GPA is 1/2 the weight of a 421 or 416.
OG I got email; thanks.

[les winter]

Just a little more info, please: If I substitute a 416 recone into a 421, do I get a reasonable replica of a 416? Any reason not to do this myself?
thanks again.

[magnarc]

They are different drivers, and AFAIK, different VC and magnet structures.

Don't always believe the spec sheets either, you may find that the 418 is the same mag as a 416A, or 8-Z, but not a B or C.

There is nothing wrong with a 421. It is prob not the best unit for a M19 clone though.

I think you'll find a 416 kit will not fit into a 421.
A 420 tho, the biflex, is the same as a 416, and maybe a better go for a recone.

If you are careful, yes reconing can be done, search round for the ALtec tech letter on reconing techniques.

[les winter]

Hi OG. what thickness and size do you recommend for the felt?
thanks
Les

[Old Guy]

what thickness and size do you recommend for the felt?

Not sure what felt?

You mean to convert 808's?

[les winter]

Hi GM. I'm in forward progress. I got my first 421 and a 416 recone kit in hand. I stripped the 421 and cleaned it. This unit has two screens. One on the magnet rear, and one under the dust cap. The one under the dust cap has what appears to be metal spatter; not so as to completely block it off, but there is some. It doesn't come off when I dab it with adhesive tape or shoot it with compressed air. Should I leave it in place? Do you have a recommendation for how to block off the back vent?

Thanks.
Les

[Old Guy]

Altec glued a metal disc over the hole...at the end some of those came loose, Altec's QC was deteriorating..

EV used a tapered foam plug to block back vents...I would be tempted to do something like that...and just put a permanent adhesive Mylar label inside and out...circular labels are a stock item...but I would also ask GM's opinion of that before I did it...