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Old 28th July 2012, 06:36 AM   #1
kctess5 is offline kctess5  United States
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Default Fostex horn help

I'm looking into putting a pair of Fostex FW168HR's into a horn, with a helper tweeter, which looking at the drivers specs should be pretty easy, but the design isn't going well.

I've been fighting with hornresp for quite a while now and I just can't seem to make anything better than the 15 liter recommended bass reflex enclosure which is just sad

I tried a few MLTL type enclosures to limited success, a bunch of variations of back loaded horns, some transmission lines, I even used the BIB spreadsheet and modeled the results.

Does anyone know of a geometry which might work well for this woofer? I'd love bass down to the 30-40 range so I could go without the sub

Thanks
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Old 28th July 2012, 06:59 AM   #2
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Hi , it's difficult to obtain good bass from a 6" ,
and having in mind the assumption of '35/40 Hz required' it
would be better to set some 'gain' points :
Only subwoofers with long excursion and thermal overload control
can assure ( if placed properly) a good output in that band .
A basic 6" will have its F10 point at that frequency
If well done , a B6 alignment with a line level tilt at Fc and HP below an octave or so - pardon if I may report the wrong - is said to be a good choice = compromise . But that includes the use of some electronic equalization for correction , same as in subwoofer applications .

For 'normal' applications , like home listening , a 6 " might be very good.
I would make the box proposed by Fostex , preferably with the port on the bottom . A +3dB reinforcement in the lower octaves reproduced ..
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Old 28th July 2012, 01:20 PM   #3
hm is offline hm  Europe
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Default kctess5

in combination with the Fostex no crossover no tweeter
http://www.tb-speaker.com/detail/1230_04/w6-1916.htm
in my POSAUNE horn, both with 25 mm extra baffle, and the Fostex as the back driver
not invers only parallel.
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File Type: jpg Posaune_70115_Totale.JPG (191.0 KB, 113 views)
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Old 28th July 2012, 06:04 PM   #4
kctess5 is offline kctess5  United States
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Quote:
Hi , it's difficult to obtain good bass from a 6" ,
and having in mind the assumption of '35/40 Hz required' it
would be better to set some 'gain' points :
Only subwoofers with long excursion and thermal overload control
can assure ( if placed properly) a good output in that band .
I have trouble believing that from personal experience. I have a 4" woofer in a folded TABAQ that gets to the mid fourties with ease (in an open garage! its my work system). It doesn't seem like a huge leap to expect to be able to get less than half an octave below that with a 6.5" woofer. Especially when considering that the Fs of the driver is 45Hz, so it seems that it should be able to get down to at least 45Hz without too much stress

Also I have a mid sized 12" sub I built a while back that doesn't have long excursion and thermal control and performs at normal room listening levels, i.e. able to have a normal conversation with the music playing, excellently down to 25Hz. Actually under normal listening levels the cone excursion is almost to small to see, but when I crank it becomes more visible and is wall shaking loud

For PA applications what you say is absolutely right, but in room I'm not so sure.

The reason I want to stretch the output is so that I don't need a 3 way design, which can be pretty expensive to get low distortion bass drivers. Although if I did go 3 way I could use sealed boxes all the way around and have less midrange coloration

Quote:
in my POSAUNE horn...
That looks like it would be pretty similar with the 168. Do you happen to have the Hornresp input for it?

Last edited by kctess5; 28th July 2012 at 06:08 PM.
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Old 28th July 2012, 06:33 PM   #5
hm is offline hm  Europe
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Hello,
look measurements and single simulations of the small Posaune the Cornet
kornettmess
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Old 28th July 2012, 07:51 PM   #6
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Quote:
Originally Posted by kctess5 View Post
For PA applications what you say is absolutely right, but in room I'm not so sure.

The reason I want to stretch the output is so that I don't need a 3 way design, which can be pretty expensive to get low distortion bass drivers. Although if I did go 3 way I could use sealed boxes all the way around and have less midrange coloration
Thx

Yes , I was referring to the particular case of me , as I'm searching
but can't find a good sub of 6-7" diameter . That said , I 'd love to try the little
TB 3" classified as sub
indeed , the double driver configuration as HM proposed is a viable solution
that I've been considering , but refused eventually for
the same sensitivity and SPL obtained by two drivers in series .
Also the low freq. cut adds issues with coils , with cost as much as the driver,so it's better not to mess with those things
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