Has anyone tried the Fostex F120a driver on an open baffle setup?

Dracule1 · « **on:** 22 Jun 2010, 08:39 am »

Actually, is this driver even designed for this?

JohnR · « **Reply #1 on:** 22 Jun 2010, 09:32 am »

Looks like Martin King did:

http://www.quarter-wave.com/Project08/Project08.html

(Link at bottom)

JCS · « **Reply #2 on:** 22 Jun 2010, 10:21 pm »

One caveat about the F120a: MJK and I have both concluded that the F120a doesn't do well on SS amps. We tried several SS amps, but didn't find one that would make the F120a sound good. This driver seems to only do well with tubes. However, we didn't have anything like Nelson Pass's First Watt.

Cheers, Jim

Dracule1 · « **Reply #3 on:** 23 Jun 2010, 02:32 am »

Why do you suppose Fostex uses foam surround than rubber? I always thought foam is a bad material for this application. It degrades much faster than rubber.

Bemopti123 · « **Reply #4 on:** 23 Jun 2010, 03:51 am »

Quote from: JCS on 22 Jun 2010, 10:21 pm

One caveat about the F120a: MJK and I have both concluded that the F120a doesn't do well on SS amps. We tried several SS amps, but didn't find one that would make the F120a sound good. This driver seems to only do well with tubes. However, we didn't have anything like Nelson Pass's First Watt.

Cheers, Jim

In my experience, perhaps it might apply to the F120A as well, I have a pair of F200As in the FTA-2000 cabinet form and they are to be paired with op chip based amps for the most absolute, robust and rhythmic sound I have yet to experience from a pair of dynamic coned speakers. Moreover, it is very possible that simple mosfet based amplification might hold the key for great sound. 40 watts per channel should be the minimum when it comes to op chip amps.

Russell Dawkins · « **Reply #5 on:** 23 Jun 2010, 08:12 am »

Quote from: Dracule1 on 23 Jun 2010, 02:32 am

Why do you suppose Fostex uses foam surround than rubber? I always thought foam is a bad material for this application. It degrades much faster than rubber.

I imagine it is possible to formulate foam rubber so it doesn't degrade so fast, but it is my understanding that foam tends to terminate the cones more optimally than solid rubber in that the absorption of the vibrations traveling over the surface of the cone is more complete. I guess the more abrupt change in density at the edge of a cone terminated with a rubber surround causes a stronger reflection back toward the center.
The bottom line seems to be that foam sounds better than rubber - at least where the cone is relatively light weight and midrange frequencies are of interest, as opposed to bass-only duties.

Much of this is conjecture based on various reading - perhaps a speaker designer could confirm?

JohnR · « **Reply #6 on:** 23 Jun 2010, 08:21 am »

Foam has a bad rep but I understand that it is no longer deserved. The Lambda/AEspeakers dipole woofers use a foam surround, for instance.

planet10 · « **Reply #7 on:** 23 Jun 2010, 08:59 pm »

Manufacturers tell us they have sorted the issues with foam degradation -- we'll need to see some of those age to see how they do in the long run... i know that i have 1st gen Adire Shivas in the field that are still fine.

Rubber is a lot heavier for the same support as foam. Rubber ages as well. I've seen many a rubber surround driver where the rubber has become VERY stiff. The dopant in some cloth surrounds can suffer the same fate.

Personally i don't worry about it.

dave