slightly modified 290s

**Phil-G** · March 14th, 2020, 08:06 PM

Has anyone seen a vented diaphragm?

PAIR (2) ALTEC-LANSING 290-8K HF COMPRESSION DRIVERS - TESTED | eBay

**Elitopus1** · March 14th, 2020, 11:21 PM

Wow. How did they even make the cuts in the diaphragms like that? Looks pretty clean. Lol.

**BillWojo** · March 16th, 2020, 07:08 PM

They look like they were manufactured that way, the cut outs are to precise to have been done by hand. I'm guessing that they are not intended for audio use but for exciting something under test conditions.
Looks like the seller got his money though. Wait till the buyer shows up on here complaining that his new 290's sound like crap.

Nope, looks like they ended with out a bid.

BillWojo

**Phil-G** · March 16th, 2020, 10:06 PM

Originally Posted by BillWojo

They look like they were manufactured that way, the cut outs are to precise to have been done by hand. I'm guessing that they are not intended for audio use but for exciting something under test conditions.
Looks like the seller got his money though. Wait till the buyer shows up on here complaining that his new 290's sound like crap.

Nope, looks like they ended with out a bid.

BillWojo

it simply says no longer available. maybe he sold them on cracklist.

**Old Guy** · March 18th, 2020, 12:57 PM

Originally Posted by BillWojo

They look like they were manufactured that way, the cut outs are to precise to have been done by hand. I'm guessing that they are not intended for audio use but for exciting something under test conditions.
Looks like the seller got his money though. Wait till the buyer shows up on here complaining that his new 290's sound like crap.

Nope, looks like they ended with out a bid.

BillWojo

CNC machines are cheap these days.

**Phil-G** · March 20th, 2020, 03:16 PM

Is there any benefit to adding slots to the diaphragms?

**Elitopus1** · March 21st, 2020, 04:22 PM

The Radian diaphragms for small format Altecs have holes in the surrounds. I?m not sure what the benefits are, or why they would make them that way.

**aditya** · March 22nd, 2020, 03:14 PM

Cutout slots in the surround area reduces the suspension tension, hence can lower (fine tune) the fs.

It also can be used to achieve selective front-to-back phase-cancellation in order to iron out severe non linearities, especially around the resonant peak area.