Sex speaker build

[JamieMcC]

Well this is kind of a continuation from the "Suitable full range driver options for SEX" thread which popped up a little while back as I started investigate some of the different options available to try this type of speaker with my newly ordered Sex amp (I am predominantly a headphone listener) and which culminated in the purchase of some pre owned Fostex FX120's

Moving on to the present and after trying out the Sex paired with some old Mordant Short bookshelf speakers set up in a near field configuration with much better results than I had ever anticipated (In fact it is probably the best I've ever heard them sound). Building some cabinets to house the FX120 has finally made it to the top of the to do list.

So for anyone interested I will post a pic or two of building progresses, which will be slow as it is only the odd evening I can spare at the moment.

After losing way to many hours on the different forums and lots of changing my mind I've settled on the dFonkinfx enclosure for several reasons which included.

1 consistently favourable results reported for this cabinet type
2 said to work better with Sets amps and low watts
3 They have a similar footprint to my current bookshelf speakers

So pics of progress so far plans and timber.

Normally birch ply is recommended but I had a offcut of 18mm mahogany marine ply left over from a job so as it cost me nothing I'm using that instead, its way better quality than the Birch ply but don't have a clue how or if that is relevant or not to the end results.

(https://www.head-fi.org/image/id/6738487/width/900/height/900/flags/LL)

(https://www.head-fi.org/image/id/6738486/width/900/height/900/flags/LL)

Link to plans

http://p10hifi.net/FAL/downloads/dFonkenFX-0v8-map-020709.pdf

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fp10hifi.net%2Ftlinespeakers%2FFAL%2Fbox-plans%2FFonken-3D-B.gif&hash=f1fdd3b7b3d6d7912496807401221e9ec4240b20)

A completed cabinet of how it should look

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi973.photobucket.com%2Falbums%2Fae217%2Fbm1972%2FFonken%2520Prime%2FSAM_0468.jpg&hash=6c51714044cb67929799abd8af8d223711aac48d)

[wullymc]

Good luck with your build Jamie.

I completed Woden Valiant for use with my Paramounts.  Very happy with those.

The Fonkens look beautiful.  Looking forward to your build pictures!


Take care...Dave

[corndog71]

It would be better to have 2 or 3 horizontal braces and a top brace but otherwise they look sharp.

Something like this...

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fgr-research.com%2Fpics%2Fbox5.jpg&hash=3cc7fb4047bc9d4663f7b385fe085938876d2e40)

[JamieMcC]

It would be better to have 2 or 3 horizontal braces and a top brace but otherwise they look sharp.

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I see where you are going. I think the effect of the sandwiching of the baffles between the two vertical sides is fulfilling that particular role by creating a row of I beams which is going to make it pretty strong and resistant to flexing

The ply I have is 18mm and the distance between the cabinets internal sides and the middle offset baffle is only 70mm'ish so its going  to be pretty ridged.  I suspect it would probable a take fair old weight on the top 250kg for sure!

What is interesting in your example and what I have been wondering about is the radius to the holes in the centre baffle Some builds have them some builds do not? So a little more digging on which way might suit is still in order.

Cheers

 

[corndog71]

What is interesting in your example and what I have been wondering about is the radius to the holes in the centre baffle Some builds have them some builds do not? So a little more digging on which way might suit is still in order.

I believe the radius on the internal holes helps reduce turbulance within the cabinet, against the back side of the driver, as well reducing vibration within the brace/cabinet.

Another good idea is to radius the inside of the driver hole.  This does reduce reflections back onto the rear of the driver.

[JamieMcC]

Thanks, chamfering the back of the driver hole I have seen mentioned in some of the Fonken build threads and had planned on doing the same.

[Zimmer64]

Hi there,

I tried the FX120 with the SEX amp and found that it needs more power than 2 watts. I felt quickly limited. It works fine with 10 watt SET.

Kind  regards

Michael

[Grainger49]

Of course what you find satisfying varies with personal taste (listening volume), room size, distance from the speakers, room hardness/softness, power and sensitivity.

But it is good to collect data.  You need all the data.

[JamieMcC]

Hi there,

I tried the FX120 with the SEX amp and found that it needs more power than 2 watts. I felt quickly limited. It works fine with 10 watt SET.

Kind  regards

Michael

Thanks Michael currently I have the Sex set in a near field configuration with the speakers about 3 meters apart that have a 88dB sensitivity at a Nominal impedance of 8ohms and are recommended for use with amps rated at 15 to 60 watt RMS. The Fostex are 89db (1db is not a lot unless I am wrong, I can simulate either way a little with the 1db steps on my attenuator) the current set up actually plays to loud in the room at max volume, but is just the right volume at max to listen while having a bath across the hallway. I am using the Sex's 8ohm tap.

By the way which type of enclosure did you have your FX120's in?

This also kind of raises another question about the switchable impedance settings on the Sex what happens if I run speakers like the Fostex which have a Nominal impedance of 8ohms off of a different tap could I damage the speakers? 

[Zimmer64]

hi,

i currently run them in a double bass reflex enclosure http://zimmer64.files.wordpress.com/2012/10/20121010-180254.jpg

you dont damage them on the other impedance taps.

michael

[Paul Birkeland]

This also kind of raises another question about the switchable impedance settings on the Sex what happens if I run speakers like the Fostex which have a Nominal impedance of 8ohms off of a different tap could I damage the speakers?

This is reasonably unlikely.

The 8 Ohm tap provides a nice balance between power and damping for an 8 Ohm speaker (and distortion for that matter).  If you go to the 4 Ohm tap, you will lose some power but gain more damping.  Noise and distortion will also drop a bit.  If you go to 16 Ohms, you'll lose damping and increase distortion. 

[JamieMcC]

Thanks for the feed back guys its all very helpful.

[jwrossie]

I really like this design. I want to build a pair of these for my Stereomour, but there is a problem.
The driver Fostex FE127en are discontinued, so no longer available.

Do you have the Fostex FE127en already?

During my search they say the FF125wk is a good follow up on the FE127en.
But this driver in the Fonken is a mismatch, so you will need a different design.

[JamieMcC]

I really like this design. I want to build a pair of these for my Stereomour, but there is a problem.
The driver Fostex FE127en are discontinued, so no longer available.

Do you have the Fostex FE127en already?

During my search they say the FF125wk is a good follow up on the FE127en.
But this driver in the Fonken is a mismatch, so you will need a different design.

Hi not 100% sure if I am reading your post correctly but I am using the Fostex FX120 the dFonkenFX enclosure is designed/tuned for that driver.

I haven't actually got much further with the build at the moment other than gluing up the baffle sections, next time I am in the shop I will try and remember take a some of pics of progress (or lack of) I have been contracting full time for a different yard so spend hardly any time at the work shop just a few minuets here and there at best of late so home projects in my workshop are on hold for a while.

[jwrossie]

Hi not 100% sure if I am reading your post correctly but I am using the Fostex FX120 the dFonkenFX enclosure is designed/tuned for that driver.

I haven't actually got much further with the build at the moment other than gluing up the baffle sections, next time I am in the shop I will try and remember take a some of pics of progress (or lack of) I have been contracting full time for a different yard so spend hardly any time at the work shop just a few minuets here and there at best of late so home projects in my workshop are on hold for a while.

My bad! I thougt you wanted to build a Fostex Fonken, but it's a dFonkenFX