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Fostex FE206En in dual chamber box (double bass reflex)
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Author:  Gio [ 13 Sep 2012, 22:40 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

Hi Mark, I sent you a baffle step compensation circuit and also a zobel circuit to try out. With the BSC, I agree with you, it tends to rob the detail and dynamics that make these sensitive drivers.

Iso - try a speaker toe-in of about 30 degrees off axis as a starting point and adjust them to your taste.

Cheers

Author:  mwhouston [ 14 Sep 2012, 02:50 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

@Gio: I thinlinking about the BSC for a -3db drop in mids. Let you know what I think if I do. The other night tried 1M then about 2M. Love what it does.

Author:  Gio [ 18 Sep 2012, 00:13 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

Here is the project page for Mark`s speakers with more information.
http://diyaudioprojects.com/Speakers/Fo ... -Speakers/
Cheers

Author:  mwhouston [ 18 Sep 2012, 08:30 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

I was originally struggling to get a good central image from these new speakers when placed around my 46" TV. Applying the toe-in, like Gio suggested, worked and for the first time I'm getting a great center channel with moves. I have the speakers meet about 1 to 1.5m in front of me. Also the left channel was once louder than the left because the left is against a wall and the right has no wall reinforcement. Toeing them in turns the left hand speaker away from the wall giving perfect balance between the two channels. Win-Win!

Author:  BruceRies [ 21 Oct 2012, 19:39 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

That was a very beautiful project. You could really save a lot because it is much costly if you are going to buy it a new one.

Author:  mwhouston [ 26 Oct 2012, 06:45 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

I am about to build another pair of speakers but this time from a totally different driver set. The drivers are from the local electronics store where I work (sometimes). 5" woofer\mid and a 1" soft dome, ferrous coled\filled tweeter. I was thinking about the finish I got on my retro-F206's. That is the heavy paint stippled finish. It looks good but I think it goes further than that.

Being extremely stippled it, the paint work, is probably an excellent non-reflective (acoustically) surface. So the whole box, front, sides and back, is possibly quite acoustically non-reflective. Now think of all the speakers you have and have seen or read about that have a lovely Piano Black, shiny or wood veneered surface. How bad is that for the acoustic reflection\dispersion and neutrality.

The surface goes a bit further in my situation and has already been stated, my 46" LED TV sits between the retro-F206's speakers. With the dull stippled surface the reflection from the screen is low. Again imagine a a piano black box up close to the screen. I think on at least a couple of levels (the surface doesn't show hand marks, dust or anything) this very good looking and shockingly simple finish is a winner. My next boxes will be treated the same. All this for just a $5 roller and a few tins of paint.

Author:  mwhouston [ 27 Oct 2012, 20:38 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

While listening to an Blue Ray Opera recently with the Fostex speakers and 2.5W Paris tube amp I felt the mid-range a bit bright and a little "shouty" on some parts. I have bought the choke and resistor for a BSC network to tone the mid-range down by -2 to -3 db. But on the night I remembered I did not remove the grills. They are fine metal will affect the sound in some way. Being only held by small magnets they easily pop on and off.

I will install the BSC but should remember during the next serious listening session to try grills on and off. I may not need the BSC.

Author:  mwhouston [ 27 Oct 2012, 22:36 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

I made up the BSC with 2.2ohm 5W R and 0.82mh air choke. I tied the speakers with and without the BSC, with and without the grills and all combinations possible. The test music was a CD of heavy solo piano with massive dynamics and a thundering sound (analogue recorded): http://musique.fnac.com/a2275526/Vladimir-Ashkenazy-Steinway-legends-digipack-CD-album.

End result BSC in and grills off. Though I felt as long as the BSC was in; grills on or off didn't seem as critical. Possibly the brighter mid-range was working against the grills here with BSC out. I felt also the BSC only effect the upper-mids and not lowers. This could be easily detected in the piano pieces as scales were worked from low to high. At this point BSC stays in and grills on.

This Ashkenazy\Steinway CD sounds its very best on the Oppo DBP-93\Paris\Fostex setup. On my main system with BDP-95\Silver Dragon 300BSE and large 3 way Osborns the dynamics are no where near as "startling" nor the sound as rich and natural (even raw).

On another note I jigged the Oppo BDP-93 to provide sub-woofer info during audio CD playback. It is always on with DVD play back as an LFE feed. But listening to the stereophile LF warble tones the speakers and set-up go down to 31hz before the bass really rolls-off. 40hz has a boost due to the port and has plenty of volume. The sub-woofer is not needed with this set-up and I re-jigged the Oppo not output bass to the sub-wooker during audio CD play back. In fact the Fostex boxes went lower than the sub-woofer with 12" bass driver in an 80L ported box!! After 31hz things go very quiet though.

Author:  mwhouston [ 29 Oct 2012, 01:43 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

An interesting observation with the Fostex boxes there appears to be a volume related sweet-spot. Play them too soft and they can sound quite plain and flat, too loud and they start to compress and bass lacks detail and the mid-range sounds shoutty. But find just the right volume, which is at good to impressive level and they really sing.

Also if you build these try experimenting with a single layer of dampening at the very bottom on the box. In the 50 to 40hz range, where there is plenty of bass, the bass starts to get a bit muddy and boomy. I'm yet to try it but I think it may help with the over-all bass performance particularly down low where there is a lift in bass. Or try blocking the port..

Author:  Gio [ 29 Oct 2012, 10:07 ]
Post subject:  Re: Fostex FE206En in dual chamber box (double bass reflex)

mwhouston wrote:
An interesting observation with the Fostex boxes there appears to be a volume related sweet-spot. Play them too soft and they can sound quite plain and flat, too loud and they start to compress and bass lacks detail and the mid-range sounds shoutty. But find just the right volume, which is at good to impressive level and they really sing.

Very true. Unfortunately for my rear loaded horns I find that at the level they sound best the volume is a little too high for my listening room (4 m wide).

Cheers

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