need some advice on my new box

I am gonna be buying to of the new 12" type r's dual 2 ohm. The ones with the logo at the bottom of the cone. I am running them off an alpine mrp-m1000 amp at 2 ohms. They will be in a 1995 ford ranger ext cab. I haqve 2 12" treo rsx subs now, and they are in a custom sealed box, downfired with the subs facing the floor. My question is would i be able to build the same type of box for my new r's? I wana port the r box, but yet still have them downfired. If i use 3/4" mdf, will the box face be strong enough to support the r's weight and motor force when they are beatin? And are the ports and subs facing the floor gna affect anything when I run it at db drags? I really want them to be dowfired, facing the floor on the botton of the box for security reasons (u can barely tell they are there), and also so i dont lose my storage space in the cab of the truck. Any help would be greatly appreciated.

Thanks in advance,

Romeo

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Disturbin' Tha Peace

I forgot to mention, There is about 4-6" of space between the front of the subs and the floor. They arent sitting very close to the floor.

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Disturbin' Tha Peace

any flat surface that's over around 2ft runs the risk of flexing under heavy stress from subwoofers. 3/4 mdf will support the weight just fine you just might have to worry about some flexing. there's nothing wrong with downfiring the subs and port. and im not sure exactly the dimentions you had in mind for your box but type R's kind of like bigger boxes so just be prepared.

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I am aware of the large boxes required by the type r's. i used to have a pair in my cavalier at one time. I was considering putting a second face on the sub side of the box. So it will be 1 1/2" thick where the subs screw in. So the ports being downfired arent gna hurt nothing? I am planning on running at db drags next year and I wana make sure the subs and ports sitting that close to any surface aint gonna affect spl or tuning or the like. Also, is 30 hz too low for a set of r's for the port freq?

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Disturbin' Tha Peace

IMO 30hz is too low for any true spl setup. a low tuning frequency like that is mainly for sound quality or ground pounding setups, they usually wont give you numbers on a meter unless you are running like 4 18's. double layering the baffle is always a good idea but for all that, you can just use 1" MDF on the whole box. its up to you.

and down firing shouldn't affect your tuning frequency. i would imagine that there are situations where it could change the frequency by turning the floor into part of the box and becoming some sort of bandpass box but that is pretty far out there.

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Okay. I was gna tune it low for the feel. I play mostly low bass, like bass i love you, and c murder and young jeezy, etc. A lot of the songs i play hit around 25-40 hz. I have 2 12" treo rsx subs right now, and that is why i am upgrading. they dont hit the lows like my old r's used to. That all being said, what fequency would yall recommend i tune the ports too? It's gna be a dual chamber box, one port per sub. I am gna be using the ports that are flared on both ends.

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Disturbin' Tha Peace

35hz is plenty for that type of music but its really up to you, if you want to go lower then be my guest. i love low tuned boxes, im box for my 18 is tuned just above 32hz and it gets down, im just saying dont expect huge numbers on the meter from it.

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i was reading that you arent supposed to play frequencies below your port frequency. Thats another reason i'd like to tune it low. any advice on this? Also, I am gna be buying flared ports to reduce port noise. Tyhey will be flared on both sides. How do you measure those for tuning frequency? From the end of the flange or from the inside somewhere? doesnt the flare on the port affect the diameter of the tube at the end of the port so thus affecting the length the tube needs to be? Or is this all figured into the calculator on this site?

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Disturbin' Tha Peace

You're right, tuning lower than you play is more for SQ than SPL.  The thing is, you don't get the benefit of the extra db's at the tuning freq, so you have to ask yourself why you ported it in the first place.

The thing to do with any subwoofer is, check the parameters to tell if it prefers to be vented or sealed.  FS divided by QES gives you the answer, and it is called EBP.  An EBP below 50 requires a sealed enclosure, above 60 is generally best as a vented type.

If your sub wants a vented box, it's your choice of where to fix the tuning freq.  That decision comes about when you are working out the model using WinISD or other software, and some of the considerations are:  1- size of enclosure , 2- concern of sound quality vs. sound pressure level,

If you tune to gain SPL, like most people would, set your subsonic filter to feather out frequencies below the tuning freq.  Target the next octave down, or close to it.  For instance, you don't have to filter out 34 Hz if your tuning freq is 38 Hz.  It just has to be gradual.  Always test your completed setup to find out if the subwoofer behaves erratically , uncontrolled in and out movement, at lower than Fb freqs.  If it behaves like that, increase the freq of the subsonic filter, or lengthen the tuning port to lower the Fb.  There's always some tradeoffs.

FYI:  the flared ports will be accompanied with instructions pertaining to length vs. target frequency.  If they aren't, ask the supplier of the flared ports for the information.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.