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Old 19th October 2006, 09:38 AM   #1
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Default Downfiring sub, how much space underneath?

Hi everyone,

I'm going to rebuild my Rythmik sub into a downfiring enclosure, whats the minimum space under the box you'd suggest?

It's the 12" driver and will only be open on 2 sides as it's being placed in a corner, is 4" or so (steady ) sufficient?
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Old 19th October 2006, 10:16 AM   #2
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The height is important but also the width of the opening. If you have a good width opening 4 inch high should be fine.

Have you checked the sag you will get with moving to downfiring?
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Old 19th October 2006, 11:24 AM   #3
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Ric;
I'm considering the same change for my Rythmic setup, sealed box, 2cu ft., in corner. There are a number of downfiring projects on the Rythmic web site, don't think sag will be a problem. Have you started yours yet? Also, how do you plan to mount the Amp? -----I was thinking of seperate enclosure outside of main box.

Pete
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Old 19th October 2006, 11:48 AM   #4
djQUAN is offline djQUAN  Philippines
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slightly OT: I have a car setup that has the subs facing upwards. then I read about cone sag due to the weight of the cone. I'm wondering, how long will this take to occur? I'm using Kicker comp vr subs.
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Old 19th October 2006, 12:02 PM   #5
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Sag will 'occur' straightaway, it just gets worse over time.
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Old 19th October 2006, 12:41 PM   #6
Svante is offline Svante  Sweden
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Quote:
Originally posted by richie00boy
Sag will 'occur' straightaway, it just gets worse over time.
The immediate sag is easy to calculate:

xsag= 9.81 / (2*pi*fs)^2

However, over time the sag gets greater depending on the static load on the cone suspension. This sag is very hard to predict, since it depends so much on the materials in the suspension.
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Old 19th October 2006, 12:45 PM   #7
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ok, I forgot to clarify my question a bit..... how long will it take to be a significant problem?

I guess that would mean I would need to change my sub box again.
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Old 19th October 2006, 12:52 PM   #8
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We can't say how long. As Svante said it depends on the materials used.

It may not even be a problem, my sub driver has no noticeable cone movement when changing from vertical to horizontal.
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Old 19th October 2006, 01:17 PM   #9
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Thanks for the replies

Like richie00boy's driver my Rythmik driver doesn't move noticably when you point it downwards, I can mount it normally but it would look a lot neater downfiring where I'm building the new box (into the bottom of my wardrobe )
The two openings will be roughly 15" wide and whatever height we decide here, if I can keep the opening small it will look tidier but nothings set in concrete.

Peter, I've already go the sub up and running in a semi-temperory, front firing box just to play with room positioning ect. The box is 2cu ft sealed made of 36mm thick MDF, amp and driver are both routed flush into the box. Is yours built yet? If not get ready for some lovely fast, deep and clean bass
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Old 19th October 2006, 01:21 PM   #10
djQUAN is offline djQUAN  Philippines
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to go back on topic, I have built in the past a dual down firing box using two 10's and the sound comes out only on one side. the height is only 2 inches but the sound is just fine. the subs are in separate 0.75cu ft sealed chambers.
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