Downfiring sub, how much space underneath?

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
 
richie00boy said:
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.
 
Thanks for the replies :cool:

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 :smash: )
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 :D
 
Ric;

I built the sub in a rather large "endtable" enclosure some time ago and it is truly amazing, however, changes in the configuration of the room force me to downsize the enclosure to a simple 17" cube and place it in a corner. Can't figure out how to send a picture to this blessed forum, but there are shots of it on the Rythmic website.

I had considered downfiring at the start but concerns about distortion from the floor altered my plan. Having listened to the unit for some time I do not believe that this will be an issue and if it is I'll cross that bridge when I get there. Should begin building in a month or so.

Pete
 
I'm currently working on some software for sonosubs.

The guidleine I'm intending to use for the gap between the bottom endcap and the floorplate is:

"The air leaving the front of the driver should not encounter a cross-sectional area smaller than the area of the cone itself"

The green area in the attached drawing should be equal or greater than Sd of the driver.

An approximation using nominal diameter is:

An 08 inch driver needs 1-9/16 inch gap
A 10 inch driver needs 1-15/16 inch gap
A 12 inch driver needs 2-3/8 inch gap
A 15 inch driver needs 3 inch gap
An 18 inch driver needs 3-9/16 gap gap

Comments??
 

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I was interested in mounting the driver in one of his kits downward.
He said it was perfectly ok. It's been over a year since that. I'm 99 percent certain that this is what he said and 75 percent certain that you and I are describing exactly the same driver, enclosure type, linkwitz transform or servo, etc. That's why I'd suggest you email him with your exact question. Only reason why I suggested it to you is to assure you that he responded to me promply and fully. Others on this board have had similar correspondence with him. I forgot his name, I think it was Brian.

Good luck.