Effects of using a cabinet smaller than SBB4 alignment recommends? - AVS Forum
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Old 09-18-2012, 06:43 PM - Thread Starter
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I'm designing a cost effective subwoofer for a great home theater experience and a good music experience as well. To that end, I've decided on A single 12" driver and a ported cabinet utilizing the SBB4 alignment to keep the bass response as tight as possible while still taking advantage of the extension provided by a ported cabinet.

I've been modeling different drivers and boxes in WinISD for days and I think I may have finally found a good combination. I've modeled the Tang Wang WQ-1858 driver in WinISD using the SBB4 alignment (grey line in screenshot) and the modeled frequency response looks pretty good. My only concern with this design is the box size. At 3.75 cu-ft before accounting got port, driver amp, hpf, etc, this thing is gonna be BIG. I don't have a ton of room in my home theater. So, I'm wondering what the effect of shrinking the box size will be. So I modeled a box size of 3.2 cu-ft (yellow line in the screenshot) and the frequency response still seems pretty good.

My question is: What else am I "giving up" by ignoring the SBB4 recommended box size? I understand I'm lowing some low end extension. But am I giving up anything else? I chose SBB4 to try and minimize the damage to transient response, so will this size constriction affect transient response in a negative way compared to the 3.75 cu-ft cabinet? confused.gif

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Old 09-18-2012, 08:26 PM
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Ignore the alignment, all that matters is the result. Alignments are a relic of the slide rule era, when calcs were so difficult to perform that a few 'alignments' were arrived at to simplify the design process. With software you can arrive at literally thousands of different alignments, which makes choosing from a mere half dozen rather moot. WinISD defaults to whichever of the traditional alignments give the flattest response, but that's only a starting point to tweak from.
On the topic of WinISD, ditch the Beta, it's far too simplistic and only gives a rudimentary result. Alpha Pro is the only way to go. As for transient response, that's only a concern in the midrange, it's of no consequence with a sub. And there's no such thing as tight bass response either, that's a midbass/lower midrange issue, though a poor sub design can result in excess midbass.

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