Is it true that the higher the BL of a subwoofer, the higher its lowest playable...

454Casull · 20th February 2004, 09:00 PM

frequency?

Timn8ter · 20th February 2004, 09:21 PM

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.

RobM · 20th February 2004, 09:26 PM

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.

Timn8ter · 20th February 2004, 09:31 PM

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.

sreten · 20th February 2004, 09:36 PM

Quote:

Is it true that the higher the BL of a subwoofer, the higher its lowest playable frequerncy ?

no, it is not true.

sreten.

Svante · 20th February 2004, 09:57 PM

No. There is more to it than that.

Pjotr · 20th February 2004, 10:11 PM

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.

LineSource · 21st February 2004, 12:36 AM

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

454Casull · 21st February 2004, 03:22 AM

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?

DanWiggins · 21st February 2004, 02:59 PM

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
Adire Audio

20th February 2004, 09:00 PM	#1
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	Is it true that the higher the BL of a subwoofer, the higher its lowest playable... frequency?

21st February 2004, 12:36 AM	#8
LineSource diyAudio Member Join Date: Sep 2003 Location: SiliconValley	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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20th February 2004, 09:21 PM	#2
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	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.

20th February 2004, 09:26 PM	#3
RobM diyAudio Member Join Date: May 2003 Location: West Orange, NJ, USA	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.

20th February 2004, 09:31 PM	#4
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	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.

20th February 2004, 09:57 PM	#6
Svante diyAudio Member Join Date: Feb 2004 Location: Stockholm	No. There is more to it than that.

20th February 2004, 10:11 PM	#7
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	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.

21st February 2004, 03:22 AM	#9
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	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?

21st February 2004, 02:59 PM	#10
DanWiggins diyAudio Member Join Date: Aug 2002 Location: Seattle or Shanghai	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 Adire Audio

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