Making a 416 out of a 421

[les winter]

Well the excitement never ceases. I reconed the 421, left the screens in, taped up the back vent, and measured it using WT3 with the speaker laying on its back.

Ugh.

QTS measured 0.75. I let it run in for a while with low frequency signals. Got worse. I called Speaker Exchange where I got the recone kit: they never measure driver Q so they don't know if it is normal or not.

Inspiration. I propped up the speaker vertically. Bingo (kind of). QTS measures around 0.4. Seems like the new suspension is very limber and maybe, the coil was out of the gap in the when the speaker was lying on its back. Does this make sense? VAS was around 30, but that was measured in a box with the speaker facing down.

Any wisdom out there?

[Earl K]

- What Fs did you measure ?

FYI :

- A cone kit that's not broken in yet will have a stiffer suspension leading to a higher than normal Fs, as well as a higher than spec., Qts ( Vas will be smaller ) .


- A really well used woofer may have a suspension that's half in the bag .
- One consequence of a loose suspension will be a lower than normal Fs, as well as a lower than normal Qts ( Vas will be larger than normal ) .

- I just measured ( with WT2 ) one of my 416-8Cs that has a Fs of @ 22 hz & a Qts of @ 0.18 ....



cheers <> Earl


BTW ; You ought to be measuring a woofer hanging in the air ( suspended from a strong pipe with strong sash cord, etc ) / hanging off the ground by a few feet ( & away from flat reflective surfaces ) .
- Doesn't WT3 provide instructions for all of this ?

[Panomaniac]

Right-O! You can not get a proper reading with the woofer on its back. I clamp mine into a bench vise. Suspending them would be even better. Or holding it straight up at arm's length, if you're man enough.

I just measured ( with WT2 ) one of my 416-8Cs that has a Fs of @ 22 hz & a Qts of @ 0.18 ....

Arrrgggg...... I hate you! I can not get a 416 with a Q below 0.4 no matter what I do. The flabby 416 curse is upon me.

[Altec Best]

I can not get a 416 with a Q below 0.4 no matter what I do.

Or you can get a pair from a friend that has a good pair ! Curse defeated !

[les winter]

Hi Earl. The Fs was 19. I should check the WT3 instructions again.

[les winter]

OK, so after much fooling around, I've determined that the qts is 0.45, the vas is 40 ft^3 and the fs is 18.5 . This is driving me towards a very large sealed box to get the system Q down below 1. Any suggestions on altering the vas? I'm figuring if I really stuff a 5 cubic foot box, the stuffing will drop the system Q. I would really like to get this into a 3 ft^3 box but I don't see how. Maybe applying some kind of goop to the spider?

[GM]

I would really like to get this into a 3 ft^3 box........

Go open back and adjust stuffing to get response down to ~80 Hz to XO to the sub system. Use tightly stretched double knit for a rear cover.

What makes vintage drivers such as the 416 special is its high Vas which allows better tracking of the signal at low input than modern day low Vas drivers [all else equal], so don't recommend altering the driver except through acoustic mass loading [stuffing]. Anyway, seems there's other ways: Modyfying the parameters of a 15" woofer - diyAudio

BTW, what are the rest of its specs?

edit: How come the embedded link isn't highlighted in some way?

GM

[les winter]

This started out as an inquiry about Model 15's over at the Audio Asylum. GM suggested that I consider building something like a small Model 19. So I got a pair of trashed 421's (one from Old Guy's Brother; thanks Old Guy) and a pair of 416 recone kits and off I went.

The lower cabinets are around 7 cubic feet and the upper ones around 3. Still to go: Mrs. Darst's foam (I hope) laminate the lower cabinets and cut the holes to connect the upper volume with the lower one. The crossover is a Model 19 clone. The horn is a 811B and the driver is a GPA 902.

Sounds pretty fair, even with an old Sony HT receiver.

Thanks for all the help I received.
Les

[gearfreak]

Sweet, looking good!