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Old 3rd June 2012, 11:39 AM   #1
dondiba is offline dondiba  France
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Default baffle step compensation, zobel, notch filter

hi,
i dunno exactly what are the differences between these concepts (so you know how ignorant i am)
my fe103e single driver speakers are fatiguing because of exaggerated mids/hight frequencies
so i suppose i must digg there
enclosures are 25 liters , vented
what circuitry should be recommended?
thank you
dondiba
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Old 3rd June 2012, 12:01 PM   #2
sreten is offline sreten  United Kingdom
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http://www.humblehomemadehifi.com/do...o-103_copy.pdf

http://www.fostexinternational.com/d...fe103erev2.pdf

Hi,

First link contains a filter. 25L is a lot for a 6.9L Vas driver, and impossible
to tune without some form of bass peak, and the overall bass loss will be
added to by baffle step, no wonder it sounds thin.

rgds, sreten.
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Old 3rd June 2012, 12:26 PM   #3
dondiba is offline dondiba  France
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hi,
the enclosure design was found here :
La Petite Audiophile

I'll try the filter values , maybe will have to tweak as the enclosure is different
regards
dondiba
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Old 3rd June 2012, 02:03 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

That box calculates to nearer 30L and a vent tuning around 45Hz.
I'd convert it to a FAST (full range assisted).

rgds, sreten.

Response shown is without taking baffle step into account.
Try http://sound.westhost.com/bafflestep.htm
with limited power, increase its range if needed.
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Last edited by sreten; 3rd June 2012 at 02:11 PM.
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Old 3rd June 2012, 02:27 PM   #5
sreten is offline sreten  United Kingdom
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Click the image to open in full size.

Hi,

Above is the simulated ripple of a little over 8" wide baffle, with a 5" driver
and rounded edges. In your case ripple will be more due to the straight
edges and the use of a smaller driver (that increases ripple).

You might be looking at about 12dB gain, 100Hz to 1KHz, taking
into account some room gain, nearer 15dB anechoic probably.

rgds, sreten.
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Old 3rd June 2012, 04:00 PM   #6
bjorno is offline bjorno  Sweden
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FYI,

b
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Old 3rd June 2012, 05:09 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by bjorno View Post
FYI,

b
Hi,

The MJK sim is more accurate than my simplistic box modelling,
indicating somewhat more bass output and more peaking.

It may sound like a wacky idea but adding a higher Q lower Fs,
higher Xmax driver in parallel as a 0.5 way driver might work well.
(You could of course just use another Fostex, but thats boring ...)

(The former something even Bjorno might be challenged to model .....)

This is cheap : Madisound Speaker Store (and great value).
Interestingly it has the same completely linear Xmax as the Fostex,
but due to the long coil and gap, will overload more gracefully I
assume. I reckon it will add ~ 10dB to maximum bass output.

But the inductor isn't : Madisound Speaker Store

Line the port with porous foam to detune and damp it somewhat.
1/4" foam would be a good place to start IMO.

You should also stuff the area behind the Fostex, to damp its
midrange and suppress the vertical resonant mode of the cabinet.

Whatever, you should end up with a a lot more bass and bass end
capability. The added driver should reduce the bass end peaking.

If done well the extra driver will suppress the fostex's limited excursion,
and the whole far exceed the starting point, for not much, fingers crossed.

rgds, sreten.
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Last edited by sreten; 3rd June 2012 at 05:26 PM.
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Old 3rd June 2012, 06:18 PM   #8
bjorno is offline bjorno  Sweden
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Agree with sreten.. First try to put some damping material into the port, reduce the port length too.

Hints on how much in the submitted picture:

b
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Old 3rd June 2012, 06:52 PM   #9
dondiba is offline dondiba  France
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hi, why not ,
make a 2nd hole above the fostex' and closest as possible for a 2nd driver,
otherwise the precision of imaging would be impaired;
the 103fe and the aura are 8 ohms ,so in parallel the 'impedance' will be half, 4 ohms, i suppose, still drivable by a SS amp
could be fun but the enclosure is glued + screwed + braced very strongly...
so, i'll try to reduce the port first, it's easier ;-)
regards,
dondiba
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Old 3rd June 2012, 07:24 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

Lining the port reduces the tuning frequency, reducing its length
increases the tuning frequency and is generally a very bad idea.

There is little point mounting a 0.5 way driver above the main
driver. If the look appeals cut a hole above the Fostex for the
Fostex, stuff behind it. Enlarge the original hole for the Aura.

Chamfer the Fostex hole, the Aura hole is not so critical.

The drivers don't have to be particularly close at all for a 0.5 way.
The 0.5 way driver could be mounted pretty much anywhere below
the Fostex and the port, but if you like the visuals above go for it.

rgds, sreten.

Yes it will be 4 ohms in the bass, and 8 ohms in the mid/treble,
not a problem for most amplifiers other than naff IC amplifiers.
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Last edited by sreten; 3rd June 2012 at 07:39 PM.
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