Fostex FE207E with Eminence Alpha 15 open baffle

sharpi31 · 25th April 2007, 10:32 AM

I am about to try out open baffle speakers for the first time (other than my Maggies). I have both a pair of fostex fe207e and a pair of eminence alpha 15.

My plan is to use a baffle about 600mm x 1000mm, sloping backwards slightly with 200-300mm side cheeks.

I am keen to keep things very simple initially, with a single inductor on the bass driver and the fostex running full range. I've played around with The Edge software but would appreciate some advice.

What inductor value would you recommend for starters? I have read about similar systems using from 3.9mH to 7mH.

Does the baffle size seem appropriate?

I don't want to get bogged down with BSC filter etc. as my next purchase will probably be a DEQ2496.

Any advice would be appreciated.

ttan98 · 25th April 2007, 11:34 AM

Martin King has developed a Mathcad program which allows you to determine baffle width and high required and also the roll-off frequency for the bass end.

Contact him, he is most helpful.

sharpi31 · 26th April 2007, 03:20 PM

Many thanks ttan98 - I've ordered a mathcad model from Martin.

Ricky · 26th April 2007, 05:53 PM

Quote:

Originally posted by sharpi31
[B]I am about to try out open baffle speakers for the first time (other than my Maggies). I have both a pair of fostex fe207e and a pair of eminence alpha 15.

My plan is to use a baffle about 600mm x 1000mm, sloping backwards slightly with 200-300mm side cheeks.

Hi.

I've had a lot of experience with Eminence Alpha's in OB situ's.

I feel your choice is a good one. You may have to go to a 2nd order filter for the Emmy tho or else you might not be able to make it "shut up". A frequency of about 500Hz should do it. When you go to the DCX, using the same frequency, shut it off at 24dB/Octave or steeper and put a bottom limit on it of around 40Hz with a 2nd order roll.

You can also tame the top end of the Fozzie with a 6dB slope at around 8K.

Look forward to your results.

Ricky.

sreten · 26th April 2007, 07:19 PM

Hi,

The Fostex run full range does not sound like a good idea due to xmax.

I'd say you should use a series 1st order crossover at least.
1st order series should work better than the normal 1st order parallel.

4mH / 80uF are very ball park values.

/sreten.

felixx · 27th April 2007, 08:57 AM

What do you think about this?

System Pictures & Description

OzMikeH · 27th April 2007, 01:01 PM

I have found my Fostex Fe207E somewhat flat in the extreme high end.
I may be doing something wrong for that result though, they only have about 50 hours on them.

sharpi31 · 27th April 2007, 01:12 PM

Those are beautiful felixx.

How do you cross them over?

Did you use a BSC or equalization?

I think my first pair will look a bit less impressive than yours :-)

felixx · 27th April 2007, 01:24 PM

I use Alpha15A for woofers and works very well.
The cross is active only for Alpha's.
The cuttoff is 250hz with Burr Brown OPA2134.
I have an active filter "a la Linkwitz" 3db and could be modified easy.
The Supravox is free of any components and it goes superb(xmax. is 4mm).

Here is an impressive work with Fostex into open baffle:
http://www.bd-design.nl/
Quasar.

sreten · 27th April 2007, 01:39 PM

Hi,

Note that open baffles do not have BSC (baffle step)
as such, they have baffle roll-off at 6dB/octave.

You can use 2 bass units in a 0.5 way configuration to
compensate for 6dB of this roll-off, i.e. extend one octave.

/sreten.

Active EQ and bi-amping you can do anything with the lower unit.
You can reduce the Fostex amplifiers input capacitor to cut low bass.

25th April 2007, 10:32 AM	#1
sharpi31 diyAudio Member Join Date: Oct 2005	Fostex FE207E with Eminence Alpha 15 open baffle I am about to try out open baffle speakers for the first time (other than my Maggies). I have both a pair of fostex fe207e and a pair of eminence alpha 15. My plan is to use a baffle about 600mm x 1000mm, sloping backwards slightly with 200-300mm side cheeks. I am keen to keep things very simple initially, with a single inductor on the bass driver and the fostex running full range. I've played around with The Edge software but would appreciate some advice. What inductor value would you recommend for starters? I have read about similar systems using from 3.9mH to 7mH. Does the baffle size seem appropriate? I don't want to get bogged down with BSC filter etc. as my next purchase will probably be a DEQ2496. Any advice would be appreciated.

27th April 2007, 08:57 AM	#6
felixx diyAudio Member Join Date: Feb 2005 Location: in center	What do you think about this? System Pictures & Description __________________ "I'm glad I can build my own mistakes."

27th April 2007, 01:24 PM	#9
felixx diyAudio Member Join Date: Feb 2005 Location: in center	I use Alpha15A for woofers and works very well. The cross is active only for Alpha's. The cuttoff is 250hz with Burr Brown OPA2134. I have an active filter "a la Linkwitz" 3db and could be modified easy. The Supravox is free of any components and it goes superb(xmax. is 4mm). Here is an impressive work with Fostex into open baffle: http://www.bd-design.nl/ Quasar. __________________ "I'm glad I can build my own mistakes."

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25th April 2007, 11:34 AM	#2
ttan98 diyAudio Member Join Date: Apr 2006 Location: Melb	Martin King has developed a Mathcad program which allows you to determine baffle width and high required and also the roll-off frequency for the bass end. Contact him, he is most helpful.

26th April 2007, 03:20 PM	#3
sharpi31 diyAudio Member Join Date: Oct 2005	Many thanks ttan98 - I've ordered a mathcad model from Martin.

26th April 2007, 07:19 PM	#5
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, The Fostex run full range does not sound like a good idea due to xmax. I'd say you should use a series 1st order crossover at least. 1st order series should work better than the normal 1st order parallel. 4mH / 80uF are very ball park values. /sreten.

27th April 2007, 01:01 PM	#7
OzMikeH diyAudio Member Join Date: Mar 2007	I have found my Fostex Fe207E somewhat flat in the extreme high end. I may be doing something wrong for that result though, they only have about 50 hours on them.

27th April 2007, 01:12 PM	#8
sharpi31 diyAudio Member Join Date: Oct 2005	Those are beautiful felixx. How do you cross them over? Did you use a BSC or equalization? I think my first pair will look a bit less impressive than yours :-)

27th April 2007, 01:39 PM	#10
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Note that open baffles do not have BSC (baffle step) as such, they have baffle roll-off at 6dB/octave. You can use 2 bass units in a 0.5 way configuration to compensate for 6dB of this roll-off, i.e. extend one octave. /sreten. Active EQ and bi-amping you can do anything with the lower unit. You can reduce the Fostex amplifiers input capacitor to cut low bass.

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