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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: high end wide range bass drivers posted by rick57 on September 24, 2002 at 00:57:08:
If I understand correctly, the target is "95 dB efficient, flat to 18 Hz, in a 3-4 cubic foot box".I don't think that's possible.
A 95-dB efficient woofer with parameters that would will give you -6 dB at 18 Hz (which, assuming a bit of room gain would be essentially "flat" to 18 Hz) would require a box of about 30 cubic feet internal volume.
If you go with a 90 dB efficient woofer, you can hit the same low bass cut-off in a 10 cubic foot box.
If you relax the bass extension requirement by an octave to 36 Hz in-room, with a 95-dB woofer you can get away with a 4 cubic foot box. If you go with a 90 dB efficient woofer, you can get about 24 Hz in the same size box.
If you really want -6 dB at 18 Hz in a 4 cubic foot box, you can get it with an 86 dB efficient woofer. But, you'd need a vent 6" in diameter and 54" long.
Note that these figures may shift around a bit with different modeling programs - but the basic trends are valid.
Now, you're probably inclined to trade off efficiency for bandwidth and go with the lower efficiency woofer. In my experience, that would be a mistake. You see, an 86 db or even a 90 dB efficient woofer will compress significantly more than a 95 dB efficient woofer. Even if you bi-amplify to match the relative loudness levels, you will still have two major problems: First, the bass will not be as dynamic-sounding as the rest of the system. Second, you can only voice the system to sound exactly right at one volume level. Any louder and the midrange and tweeter will be too loud; any softer and they will be to quiet. Incidentally, this efficiency non-linearity problem plagues many loudspeaker systems.
If you want lifelike dynamics (which, based on your midrange and tweeter choices, it sounds like you do), then you're going to have to either relax your deep bass extension requirments, or relax your box size requirements.
In my opinion, good dynamics is worth trading off extension for. Building a speaker that can shake your room is no great feat; it can be done rather easily with a low-efficiency woofer and lots of amplifier power, and maybe a little EQ. But buildng a system that is coherent and dynamic down to an honest, tight, solid 40 Hz or so - ah, that is rare and delicious.
By the way, if someone knows how to get an honest (no EQ) -6 dB point at 18 Hz (before room gain) in a 4 cubic foot box at 95 dB efficiency, I'd love to be proven wrong!!
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Follow Ups
- Something's gotta give... - Duke 09/24/0203:26:21 09/24/02 (3)
- Re: Something's gotta give... - rick57 22:11:27 09/24/02 (1)
- parameters that establish woofer efficiency - Duke 12:48:06 09/25/02 (0)
- Re:"In my opinion, good dynamics is worth trading off extension for" - mvwine 06:44:18 09/24/02 (0)
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