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| Date: |
August 14, 2003 at 11:31:30 |
| From: |
Richard Greene, [frasier.ford.com] |
| Subject: |
Re: Best Sealed Sub Driver |
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Before you ask for the "best" ... tell us how much money you're willing to spend !
I use a 15" Tempest driver in an 18" by 48" sealed tube with 8 lbs. polyester stuffing inside.
This is not an optimum design for high output at 20Hz. -- a ported design with a port tuning frequency around 20Hz. would work better in many rooms.
... but all listening rooms have room modes (standing waves) and cabin gain (bass boost) of about 12db/octave below the lowest frequency room mode. Both of these may boost output under 30Hz.
The room and the subwoofer work as a system -- what you measure one inch from the subwoofer driver dust cap and what you hear perhaps 9-12 feet away are so different it's sometimes hard to believe.
My listening room is large and has little cabin gain at 20Hz. (I've measured subwoofers outside on the driveway and inside the room.)
On the other hand, small rooms can have 9 to 12db of cabin gain at 20Hz..
Although I have almost no cabin gain to boost output at 20Hz. , my room does have a front to back wall room mode centered at about 20Hz. that boosts output at and near 20Hz. at my listening position. That specific room mode is quite strong in the front 1/3 and back 1/3 of rectangular listening rooms -- you'd have to sit near the middle of the room to avoid its bass boost effect.
As a result of that room mode, the last thing I need is a subwoofer with a 20Hz. tuned port that boosted output 5 to 7dB at 20Hz. (typical SPL increase at the port tuning frequency versus a sealed enclosure of the same size).
The combination of my sealed Tempest subwoofer and the 20Hz. room mode adds up to a frequency response at my listening position that is flat to about 18Hz.
Had I included a a port tuned to 20Hz., I would have had too much output at 20Hz. and would have had to reduce it with my Behringer Feedback Destroyer (parametric EQ).
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Posted with TalkShop version
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