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Old 12th December 2001, 08:58 PM   #1
Won is offline Won
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I plan on putting together a sealed subwoofer using the 15" adire tempest driver, probably in either Bessel or Butterworth alignments (does anyone have a preference?).

I noticed that all of the reference designs mount the driver vertically; they are all downward-firing subs. Is there a particular reason/advantage to this? Why not a standard forward-firing sub?

Also, some tower mains designs feature side-firing woofers. At what frequency is it "acceptable" to mount woofers this way? When/how does bass become non-directional?

Thanks, Won

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Old 12th December 2001, 09:18 PM   #2
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Hi All,

Mainly, any higer frequency components in the sound (distortion harmonics, rattles in the driver etc.) is attenuated by being fired into the carpet, and only the low bass reaches your ears. The other reason is you can make the sub look like a nice coffee table (Or other piece of furniture), very important for the oh so important 'significant other acceptance factor'

Be careful, apparently the suspension on some subs (although I can't give examples) will 'droop' after a long period of being mounted vertically, causing distortion and reducing maximum output. Maybe others will know of offending units.

It's generally said that bass sounds become directional around 100Hz, although I beleive it's lower than that. Cross over your subs in the 60 to 80Hz region and you will be fine.

Cheers, Adrian
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Old 12th December 2001, 09:24 PM   #3
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Won,

In some cases the orientation of the woofer may simply have to do with the woofers mechanical construction. Classic case would be the NHT-1259. The 1259 has a very soft suspension that will allow the voicecoil to move partially out of the magnetic gap should the driver be mounted vertical. This off-set then limits the one way X-max for that driver.


Kent
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Old 12th December 2001, 11:08 PM   #4
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I think a "coffee table" with a Tempest in it would do a good job of shaking whatever books/flatware/baked goods you put on it. Maybe with something to drape over it?

Being so close to the bass is probably a plus, too. And I need to get back at my lower-neighbors for their loud parties anyway!

Any opinions on side-firing woofers?

Thanks, Won

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Old 13th December 2001, 07:28 PM   #5
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Personally I don't have a preference for downfiring or side firing subwoofers, but I've found that downfiring subwoofers response suffers when placed on an area with thick carpeting.
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Old 13th December 2001, 10:56 PM   #6
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When designing a cabinet using a downward firing woofer, allowance should be made for the loading that the floor presents to the driver. The frequency response & impedance can change considerably.

Grey
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Old 13th December 2001, 11:35 PM   #7
Won is offline Won
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So, am I being told to just build a forward-firing sub? That's quite alright with me.

Does anyone have any further information about side-firing woofers?

Thanks, Won
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Old 14th December 2001, 01:31 AM   #8
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I agree with something Adrian said above: That bass directionality is more easily perceived than most people believe.
If you use a side-firing woofer and cross it over at too high a frequency, you're going to lose imaging capability, etc. The only reason I can see why people use side woofers is to keep the frontal width of the cabinet down. This is good as far as it goes, but you're into a set of tradeoffs that I prefer not to mess with.
That's just my take on things. Cabinet configuration is subject to more compromises than the usual audio discussion, and can lead to people getting emotional about their pet views.

Grey
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Old 14th December 2001, 05:28 AM   #9
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Default Sub woofs

I like down firing for music, as I am looking to add just a touch to what I already have. The forward firing subs seem to be much more for HT as you can feel the punch better. Not very sublte that.
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Old 14th December 2001, 06:34 AM   #10
Won is offline Won
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Well, being an engineer by training, I'm a bit distrustful of unjutsified statements -- not to say that there isn't one, in this case.

So downward firing woofers are better for music because they are less "punchy?" This is a term (like "wooly") that I often hear/read describing bass. What exactly characterizes "punchy" bass, and how would I "correct" for it assuming that I don't build a downward firing woofer? Is it something hard to deal with, like high pressure levels leading to nonlinearities in the response of air? What if I just chose to point the woofer to a wall? I suppose these all depend on many other conditions.

I'm sorry but I'm just a sucker for precision and unambiguity. I guess I might have picked the wrong hobby, then...

Thanks, Won
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