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Old 26th March 2014, 03:16 PM   #1
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Default Attenuating rear radiation on open baffle

I have been experimenting with a small open baffle for midrange and treble duties. I tried putting several layers of absorbent (dusters, felt, whatever) at the back of the driver. What I found was that the measured response was flatter, and the sound to my ears was more focused and cleaner. Also the stereo imaging was better. Has anyone else tried this. Apologies if this is a repeat thread.
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Old 26th March 2014, 03:23 PM   #2
Octavia is offline Octavia  United States
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Tried it, use it, and glad to keep it that way!
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Old 26th March 2014, 03:45 PM   #3
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Sounds to me like you might have the speaker too close to the rear wall. I've played with spacing all over the place and that's the only way I could ever think of the rear wave being a negative.

Too me it's the opposite...I think it adds a lot to recreate a live sounding reproduction of recorded event. Realism.

Another possibility could be how live the room is. Maybe your needing some softer properties.

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Old 26th March 2014, 03:47 PM   #4
Octavia is offline Octavia  United States
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The point is to "attenuate" the back wave, not to "eliminate" it.
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Old 26th March 2014, 05:02 PM   #5
GM is offline GM  United States
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This is one of those 'tweaks' that 'if you don't learn from history you're doomed to repeat it'.

The earliest 'closed' box speakers were large open baffles that had been folded into horns with an open back box [filter chamber] ~filled with insulation to try and mimic the large baffle's tonal 'signature' except with more gain over a narrow BW.

Shortly thereafter, just the damped filter chamber was used to make compact systems, which in turn was pretty quickly developed into the bass reflex, allowing minimal damping and an extra half octave of ~ flat LF extension.

Through it all, conventional wisdom has dictated that OBs and even large IBs be damped in this manner for best overall performance, but statistically, none bother anymore, so thanks for the reminder!

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Old 26th March 2014, 05:33 PM   #6
Octavia is offline Octavia  United States
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Done right, which means a lot of tweaking to get the speaker and the room voiced together some attenuation combined with speaker and listener placement can really make OB, Dipole, Bipole, systems vividly real. This can include both some absorbing directly behind the driver and various absorption and reflection treatment on the room walls. It can certainly help if you have a few select recordings where you know the live sound signature. Get it right and you will have that special satisfaction of seeing your friends jaw drop open when they hear what's possible. And NO you don't have to spend a fortune to get there.
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Old 27th March 2014, 04:56 AM   #7
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I have the front and back of my baffle covered in carpet. thin gray stuff from Menards with a rubber back on it. Sounded good to me but I just did it today so It'll take a few days of listening to decide If I'm happy with it.
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Old 27th March 2014, 05:19 AM   #8
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That "gray stuff with rubber" I suppose is the same thing that I've found inside
AC fans, to reduce noise.
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Old 27th March 2014, 03:56 PM   #9
Bigun is offline Bigun  Canada
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A Big'un - the Audio Nirvana Super 15

I have been down this path too and have found that an open box design with some absorbing material behind the driver is the optimal to my ears. Without absorbing material it doesn't sound right and with the box closed it also doesn't sound right (although it was originally designed as a closed box).
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Old 28th March 2014, 05:32 PM   #10
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Bigun, have just waded through your Audio Nirvana Super 15 speaker design thread. Quite a journey!.
I remember trying a small open box with a midrange driver, and some stuffing in the box, and a felt back panel. Don't know why I did not pursue the design; it sounded surprisingly good. I lack your staying power.
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