Is it true that the higher the BL of a subwoofer, the higher its lowest playable... - diyAudio
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Old 20th February 2004, 09:00 PM   #1
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Default Is it true that the higher the BL of a subwoofer, the higher its lowest playable...

frequency?
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Old 20th February 2004, 09:21 PM   #2
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I'm sure someone will correct me if I'm wrong (they'd better) but I don't see the relationship between the motor strength and the LF response as an independent parameter. LF has to do with air displacement which is a combination of surface area and excursion distance. I understand motor strength plays a part in this too. Oh, and let's not forget mass.
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Old 20th February 2004, 09:26 PM   #3
RobM is offline RobM  United States
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The higher the Bl, typically the lower the Qes, which does indeed tend to raise the 3dB point.

But that's nothing a little EQ can't fix. The real limit of woofer low frequency extension is the displacement, as mentioned above.
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Old 20th February 2004, 09:31 PM   #4
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I'll use these as an example (just 'cuz I can grab the numbers quick).

The Adire AV8 has a BL of 9 and the Tempest has a BL of 14. I'm pretty sure the Tempest will go lower than the AV8.
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Old 20th February 2004, 09:36 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Is it true that the higher the BL of a subwoofer, the higher its lowest playable frequerncy ?
no, it is not true.

sreten.
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Old 20th February 2004, 09:57 PM   #6
Svante is offline Svante  Sweden
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No. There is more to it than that.
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Old 20th February 2004, 10:11 PM   #7
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Actually Fs stays the same but Qe (which is dominant usually) gets lower. So if in a closed box, low cut off rises.

But this is when other T/S parameters stay the same. You can not compare different speakers on BL alone.

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Old 21st February 2004, 12:36 AM   #8
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Default HIGH Re GIVES HIGH BL WITH HI Qes

If you use a hig Re voice coil resistance, you can get high BL, and also high Qes.


With a 32 ohm Re you can achieve
Bl = 27
Qes=0.567
Fs=22 Hz
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Old 21st February 2004, 03:22 AM   #9
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That would mean thin voice coil wiring, which would lower power handling, or a longer voice coil (more layers usually, I think), which would also lower power handling.

Right?
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Old 21st February 2004, 02:59 PM   #10
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Actually, thin wire and/or a longer voice coil usually increases power handling (until you get so thin it can't handle the current).

For a given driver, if you raise the BL, you lose low end for a given box. Hoffman's Iron Law. Raising BL raises efficiency, meaning for a given box, you must lose low end extension.

EQ can make up for it, and ultimately - as RobM an Tim8ter point out - maximum SPL capability is displacement. But for small signal, non-boosted low end, you can have too much BL.

Dan Wiggins
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