possible to simulate IB with open baffle + DRC? - diyAudio
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Old 31st July 2006, 05:29 PM   #1
thadman is offline thadman  United States
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Default possible to simulate IB with open baffle + DRC?

would it be possible to simulate an infinite baffle subwoofer setup by placing several woofers on an open baffle (push pull to reduce vibration) and using a DRC to cancel the rear wave?
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Old 1st August 2006, 11:33 AM   #2
sreten is offline sreten  United Kingdom
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DRC ?

I don't quite understand the question. whatever is cancelling
the rear wave might as well be generating the front wave ?

Or are you thinking along the lines of the Celestion Sub ?

Click the image to open in full size.

http://stereophile.com/floorloudspeakers/892/

/sreten.
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Old 1st August 2006, 11:56 AM   #3
Did it Himself
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As the rear wave is always generated, it would not be possible unless by physically containing the wave e.g. a sealed box.
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Old 1st August 2006, 12:45 PM   #4
BenVos is offline BenVos  Netherlands
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It is possible to simulate a infinite baffle with two speakers.
The first speaker will have a first order high pass filter.
(With my speakers this is at 400 hz ESL unit)

If you use a first order high pass filter at the lowest frequency you want to use for the woofer the response will be flat up to the same frequency as the high unit wit a first order role off, creating a natural first order filter between both units.
(My speakers start at 50 Hz up to 400 Hz)

To do this you need quality units with high SPL and a big amp.
For more info about the diy kit I use see the kit supplier at http://www.metrum-acoustics.nl/

I also created a Sub for these speakers using a big 32 Clarion SRW 8000 unit.
The low frequency is tuned at 17 Hz and the acoustic role off at about 85hz.

For home theatre use my amp filters 24 Db at 80 hz.
For audio use a added a first order role off at 50 hz.

So a sub can be created with one big high SPL unit ore a big array of smaller units. The lower the frequency you use you the more units you need.

You can start with lets say 4 high spl 12 units.
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Old 1st August 2006, 04:49 PM   #5
thadman is offline thadman  United States
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I know you can destroy reflected waves with the use of a DRC, why couldnt (with a little programming) you cancel the rear wave?
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Old 1st August 2006, 06:06 PM   #6
Did it Himself
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I can't see how you can destroy reflected waves unless a mic feedback system is used and it's very fast.

Even so, this is completely different to cancelling an acoustic wave at source, which produces an in and out of phase wave simply because it's moving and both sides of the cone are exposed.

You could I suppose cancel the rear wave once it enters free space, but then the cone would be moving even more surely? Which is even more of a problem with OB where cone movement is high to start with. And you would be cancelling the whole point of having an OB.
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Old 1st August 2006, 07:29 PM   #7
sreten is offline sreten  United Kingdom
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Ahh...... DRC = digital room corrector.

Number of units on the baffle is not relevant, except nx2 for push-pull.

The problem with an open baffle is it is already (in the bass)
cancelling the rear wave, hence the baffle roll-off, and you
cannot stop it doing this because what signal you send to
the front gets reversed at the back and back to square one.

/sreten.
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Old 1st August 2006, 08:21 PM   #8
thadman is offline thadman  United States
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I wanted the rear wave to be cancelled before it could cause the baffle roll-off and have low-end extension
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Old 1st August 2006, 08:29 PM   #9
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Simply not possible. Think about how a speaker moves.
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Old 1st August 2006, 08:35 PM   #10
thadman is offline thadman  United States
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how could a DRC eliminate reflected waves and not be able to eliminate waves exiting the rear of the speaker?
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