subwoofer cabinet ideas

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subwoofer cabinet ideas

Postby Fiberglass Guy » Sun Mar 21, 2010 7:40 am

I am wondering if anybody has had much luck with a sub cabinet for a home stereo with a design in which the woofer actually faces the floor. I recently built a ported enclosure with an 10 inch sub that the woofer and port faces the floor. Getting tired of hearing the distortion coming from my bass cabinet i took the woofer out and placed it in my new custom cabinet. The bass seems to fill the entire room rather than before which was still good but seemed to be a little directional. Not even close to the performance it produces now. My distortion hasn't come back at high volumes. Now a friend wants me to build a bass cabinet for his bass guitar. I was wondering if anyone has constructed enclosures this way and how did they like them. I have been in the car stereo industry for a while now and have lots of experience building all kinds of enclosures. But its a totally different ballgame trying to fill an entire room with bass than just a car or truck so any input or advice would be great. Thanks
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Re: subwoofer cabinet ideas

Postby llung » Sun Mar 21, 2010 4:26 pm

I've built two down-firing subs. One had a 10 inch driver and port in a sonotube and the other has a down firing driver and front firing PR. You can read about their merits and problems here:
http://lungster.com/l/speakers/sonosub/sonosub.shtml
http://lungster.com/l/speakers/shiva/ShivaPR.shtml

As for distortion - not all sub drivers can be mounted downwards. The mass of the cone and the stiffness of the suspension will determine how much the cone will sag at rest. The amount of sag will decrease the actual Xmax on the driver. At high volumes, the driver can reach its excursion limit outward (downward) and distort. The original Shiva white paper calculates a deflection of 0.545mm so that's not bad at all for that driver. But other drivers may not work that well.

Other factors can influence distortion too. Are the two subs similarly constructed in terms of quality, bracing, damping, etc? Is the placement of the subs the same in your listening reviews? Do you have adequate spacing under the down firing woofer to avoid impeding air flow? What is your low pass corner frequency? What is under the down-firing sub (carpet, hard wood, tile?)

As for the bass guitar cab, I would build it the usual way - front firing; unless you know for certain your driver can handle that mounting position. Also the bass cab is not a subwoofer and will be at frequencies well above that of a sub.

just my $0.02.
-lou
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Re: subwoofer cabinet ideas

Postby Fiberglass Guy » Sun Mar 21, 2010 10:48 pm

In my case I had a single 10 inch woofer that came withe the system i bought. Having been around many high end subwoofers in the automotive industry I have installed many in a down firing setup mostly in extended cab trucks this setup always works great for me. Having said this most of the subs i work with are large some weighing more than 50 ponds a piece and that is just a single driver. I have mounted subs this large in a down firing enclosure and never had any problems so i never considered a smaller speaker having any problems with the xmax changing but this does make sense to me cause many speakers have mass to the woofer suspension and some are considerably stiffer than others so thanks for opening up another point in which i have never thought about and as for my flooring and placement I have carpet and the cab has never changed positions.
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Re: subwoofer cabinet ideas

Postby DVDdoug » Mon Mar 22, 2010 11:32 pm

I agree with Lou about the bass guitar speaker. You need to "project" the higher-frequency harmonics. (I've seen bass amps/cabinets with a horn midrange speaker.) Low frequencies are naturally non-directional, but if you start dispersing the harmonics in all directions, the speaker is going to sound weak. Also, higher frequencies are going to disperse evenly and "nicely" unless you make some sort of reflector.

And since a bass cabinet is likely to be moved/transported frequently, I think you're more likely to damage the woofer if it's on the bottom of the cabinet!
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Re: subwoofer cabinet ideas

Postby Dave P » Wed Aug 18, 2010 8:17 pm

I've had an idea for some time to build a sub using a matrix type of structure. I was amazed how much difference just a couple of small braces made to my sub so I've decided to take it a stage further. I also think it's a good idea to construct with dual cabinet walls and fill the gaps with sand to take care of any surplus resonance.
The HIFI site
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