Butterworth vs Bessel alignment for woofers - diyAudio
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Old 26th October 2009, 05:13 PM   #1
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Default Butterworth vs Bessel alignment for woofers

I am building a 3-way with dual woofers. The mid's, Accuton C173N's, where modelled for a bessel alignment. I have switched from dual Accuton woofers to dual SEAS W26FX-001 woofers. If I want to keep the Bessel alignment, my base box volumes are upwards of 127 liters. If I go with a Butterworth alignment, I am down to 70 liters.

Will a Butterworth alignment for the woofers be too slow for the 'tauter' mids?. I do not want boomy base.
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Old 26th October 2009, 05:38 PM   #2
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Can you be more specific (about the box)? Do you use simulation tools?
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Old 26th October 2009, 06:18 PM   #3
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The speed of transient response is not so important in the woofer box, what you will notice is the amplitude response if it is a bit peaky or droopy. So with there not being a huge difference in amplitude response between Bessel and Butterworth, and the Butterworth is not peaking, I think you will find the difference small and not a problem.
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Old 26th October 2009, 06:46 PM   #4
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With an F3 at 50/60Hz I think there will be a new problem besides the break in of the cone at ~2KHz (and 600Hz dip) that's always problematic in the design of the xover leaving small order xover solutions behind. That would be a better woofer for a 2-way, in my opinion, with short extension. In case you need a perfect fit for the driver use Wayne P. (alignment) simulator.
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Old 27th October 2009, 03:08 AM   #5
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Here's my take after chasing a few false audio goals (gods?) for a few decades: The bass you hear in your listening room will reflect the behavior of the woofer/enclosure system and also the acoustic behavior of your room. If you tend to listen with your ear 1" (or 2.54 cm) from your woofers then the nearfield behavior of the woofer/enclosure system is all that's important. However, if, like the rest of us, you're more likely to listen at more typical distances, then the boominess of what you hear may be dominated by the room's resonances rather than the details of the woofer/enclosure tuning.

With that in mind, you might be better off not sweating the alignment (Bessel vs. Butterworth) details of the woofer/enclosure system and instead striving to avoid peaky bass response in your listening room. Woofer positioning, the use of multiple subwoofers (each of which need not be super high performance), and considering the use of equalization to knock down peaks in the in-room bass response, are likely to make far more difference than tweaking the volume of your box by a few percent in order to make it follow a textbook Bessel or Butterworth alignment. You might check out some of Floyde Toole's writing; a brief introduction can be found at http://www.harmanaudio.com/all_about...rt_science.pdf. You could also look into Earl Geddes's writing on the subject.

If you want accurate bass reproduction at your listening seat you'll need to think of the woofer, enclosure, and room as part of a single system with multiple resonances. It probably seems less satisfying at first then focusing exclusively on the Q of the woofer in its enclosure, but if the goal is to reproduce music accurately rather than tell your friends your woofer/enclosure has a Q of 1/sqrt(2), you'll likely be more satisfied in the end.

Few

EDIT: Having just reread my own post I realize this may come off as preachy or condescending---definitely not my intent! I've just spent too much time aiming to satisfy relatively unimportant goals with multiple-decimal-place precision. If I can save anyone some of that frustration, I feel compelled to try. A little progress on very audible effects is probably more worthwhile than lots of progress on relatively unimportant ones.

Last edited by Few; 27th October 2009 at 03:14 AM.
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