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Old 1st October 2012, 07:39 PM   #1
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Default Fostex FX120 Double Bass Reflex

Hi,

In case anyone is interested. I have just finished a double bass reflex box using a Fostex FX120 driver. The building plan and a picture is attached. There is a bit of damping in the smaller chamber and none in the larger. I did not use any correction network. So there is just plain wire between the amp and the driver. I used 16mm birch plywood for the box.

I broke them in using a 16Hz test tone for about a day. After that the sound was balanced. I have placed them fairly close to the wall. About 15cm.

Sound: Very subjective of course, but I think very clean, extremely detailed and very live like direct sound. Astonishing bass performance, but below 50Hz is missing. Voices sound just fantastic. Jazz music with them is awesome and very realistic. Miles sounds like he is performing in my living room. Classical music I did not try, but pop, rock etc. sound also great. They also can go loud.

Best

Michael
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File Type: pdf DBR120_encl.pdf (47.9 KB, 194 views)

Last edited by zimmer64; 1st October 2012 at 07:43 PM.
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Old 1st October 2012, 10:55 PM   #2
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Beautiful! And you chose a great driver as well.
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Old 1st October 2012, 11:10 PM   #3
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nice art.

How much bass are you expecting from 66.5cm2" ?????????????

But, congrats, it looks really nice.

How's the phase wrap in the male voice ?
Do you hear it ?
What are the 2 frequencies that it is tuned to ?

The double tuning seems to be a great tool to reduce excursion (always a plus!).

Maybe someday I'll try some fx120's, but not this year.

Norman
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Old 2nd October 2012, 06:02 AM   #4
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Quote:
Originally Posted by norman bates View Post
nice art.

How much bass are you expecting from 66.5cm2" ?????????????

But, congrats, it looks really nice.

How's the phase wrap in the male voice ?
Do you hear it ?
What are the 2 frequencies that it is tuned to ?

The double tuning seems to be a great tool to reduce excursion (always a plus!).

Maybe someday I'll try some fx120's, but not this year.

Norman
I do not hear any phase wrap in male voices. Louis Armstrong sounds natural and so does Buble, or Eagles, Tom Petty etc.

As for the tuning, the smaller chamber is tuned to 100Hz, the second and larger one to 60 Hz. (Also see the enclosure plan).

By the way, I was not complaining about lack of base. On the contrary. Bass is well defined, not boomy, dry and with enough umpf. you can pysically feel it. When sitting at the listening position everything is fine. What I meant was, they dont make the house shake :-)

Michael
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Old 2nd October 2012, 09:01 AM   #5
ODougbo is offline ODougbo  United States
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Certainly a robust sounding speaker, probably #1 in the bass department for that size driver.

I tried to make Double - DBR boxes, Ha! sounds like me, but it didn't work as well as hoped, the sound was just confusing

(the bottom half makes a good stand, removed the drivers)

Nice wood work! You should try that driver in a Onken, you'll be surprised:

(1) you won't lose much bass

(2) they will image a whole lot better
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Old 2nd October 2012, 10:43 AM   #6
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Hi,

these are the recomended enclosures, that came with the driver, aren't they?
If so, tried them, but for me bass just was not right...

Now mine run in a QB5 enclosure and a sub below 80Hz, much better to me.

But I could never position them close to the backwall, maybe this makes a big difference?

Michael
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Old 2nd October 2012, 10:48 AM   #7
ODougbo is offline ODougbo  United States
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They should have a whole lot of bass in the DBR. If not, could be something else wrong.
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Old 2nd October 2012, 01:29 PM   #8
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The cabinet design is the one that comes with the drivers. Free standing the bass is too lean. Placed fairly close, about 10-15cm, off the back wall the bass works well. Placement makes a huge difference.

Placeing them close to the wall also improves the WAF :-)

Michael
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Old 3rd October 2012, 12:21 AM   #9
murat is offline murat  United States
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Hope this doesn't go much off-topic: I am wondering if anyone had a chance to compare FX120 and FE103-En at higher ovtaves? Say above 5 kHz. One particular point in mind is that the moving mass of 103 is half of mms of 120. Being very happy with 103 above 500 Hz, crossed with first order active filter, I am thinking baybe I should give a try to 120 and reduce my xo point?? My 103 run on OB btw...
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Old 3rd October 2012, 01:30 AM   #10
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I've neither, but I'd imagine the 103 would work better in that application of 500hz 6db.

I think with a 6db, you could try for a lower X-over point with a larger (but heavier) driver. And without a whizzer, I'd imagine the highs and ultra highs would be worse, and less dispersion up high.

Norman
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