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Which way to fire my sub?
Which way to fire my sub?
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Old 29th August 2006, 09:52 AM   #1
Gorbee is offline Gorbee  United Kingdom
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Default Which way to fire my sub?

I am a DIY speaker amateur so sorry if its a simple question .

I am hoping to build a home cinema system with some low powered speakers that i picked up (it is in the bedroom of a terraced house so can't be too loud!) I am going to be using an old Goodmans 12" at 50w as it is the one I was given. It is going to be in a small as possible box (will be experiment the size at some point). Now, I have seen people fire their subs downwards, upwards, sideways, inside out. What difference does this actually make and what would be best? Also, would I need a vented or sealed box design? Thanks
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Old 29th August 2006, 12:13 PM   #2
badman is offline badman  United States
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The size of the box will be determined by the Thiele Small parameters, which we'd need to advise you. This driver likely doesn't have the Xmax to do a down or upfiring. Dan Wiggins of Adire Audio has some guideline for which subs can be used down or upfiring. Small boxes are not ideal for subs as a rule- build the biggest box you can live with and, if you vent it, vent it LOW even if it doesn't model flat.

There are many free programs to model driver response in various boxes. WinISD, Bassbox, others.

This is all very rudimentary- the specifics of the driver determine what it wants to have for an enclosure.
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Old 31st August 2006, 10:34 AM   #3
zenmasterbrian is offline zenmasterbrian  United States
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This best firing direction is also of interest to me. I think it a very practical question.
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Old 31st August 2006, 10:41 AM   #4
richie00boy is offline richie00boy  United Kingdom
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Which way to fire my sub?
Basically point your drive unit down and see how far the cone sags compared to vertical. If it's like 5% of total normal Xmax then maybe not a problem.

'Best' is dependent on where you put the sub and what you want from it. Downfiring will excite the floor more, but be hidden from view. Side firing could be better if you can't fit much space for the driver to 'breathe' in downfiring position.
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Old 3rd September 2006, 02:42 PM   #5
zenmasterbrian is offline zenmasterbrian  United States
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I agree. I think most store bought subs lack because they aren't designed for you situation. So they just take up space.

Imagine a subwoofer that is designed as a coffee table, part of a desk, the lower part of a book case, or a stool to sit on.

Think about that, then consider firing direction.

I think there is complexity in down firing, but it protects the driver more.
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Old 4th September 2006, 07:54 AM   #6
nunayafb is offline nunayafb  United States
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General rule of safety is to always fire your sub in a safe direction and beware of you back drop.
No, I dont know why I thought that was funny, maybe because with enough excess power it applies.

Seriously, at sub freqencies sound radiates omnidirectionally so you can face it any direction you want. As far as downward, with the duplex situation I would avoid it, your goal should be to decouple the sub from the floor and downfiring will send the shockwave there first.
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Old 4th September 2006, 08:53 AM   #7
noodle_snacks is offline noodle_snacks  Australia
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For subwoofers i don't believe it matters that much, however downfiring i think is a bad idea (having had a downfiring adire tempest before). Even with a very heavy cabinet the tempest was able to shake it around when down firing and make a noise on my wooden floors, and be a pain basically.
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Old 5th September 2006, 04:34 AM   #8
zenmasterbrian is offline zenmasterbrian  United States
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If you downfire, you can have a base plate.

But you have to be concerned about driver sag.

Also, I have never seen an analysis of how long the legs need to be on a down firing system. You need to be concerned about asymetrical driver loading.

AISI, down firing was more popular 15 years ago.

This is non-trivial. Loading of subwoofers with floor, walls, and corners does effect how they behave.

I would like to see a text where all the issues are analyzed.

Down firing is attractive because it can protect the sub better.

But it is less popular today, IMO. Driver sag? I don't know.
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Old 5th September 2006, 08:07 AM   #9
RobWells is offline RobWells  United Kingdom
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Quote:
Originally posted by zenmasterbrian


-snip-

AISI, down firing was more popular 15 years ago.

-snip-

But it is less popular today, IMO. Driver sag? I don't know.

Don't let SVS hear you saying that!

Rob.
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Old 5th September 2006, 10:49 AM   #10
zenmasterbrian is offline zenmasterbrian  United States
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Please elaborate, who is SVS?
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