shoehorn a 15" woofer / design help

shoehorn a 15" woofer / design help

lookin' for the wise to guide my way. thanks in advance!

I have 2 of these: http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=290-155 - the Pioneer 290-155 clear poly cone 15 inch woofers. I also have 2 ready cabinets with an internal volume of approx 2.5 cu. ft. unstuffed. My box program skills are nil. Can someone tell me the "best" possible subwoofer configuration(s) for these drivers in the boxes I have? I'm looking to get the lowest notes possible at the expense of high SPL. Yes, I know they are not actual sub drivers. I can stuff the boxes and I can add standard tube ports or aperiodic vents, but no further woodwork skills have I. I will be driving them with a standard plate amp with crossover / phase adjustments natch. Should I throw a coil inline to help absorb high frequencies? Thanks for any help! p.s. I may get another pair of 15 to try in these cabinets; what other low cost driver from PE or MCM would get low in these boxes? p.p.s. I realize the boxes are small for 15's, but that's what I have.
 

MJL21193

Disabled Account
2007-03-10 1:20 am
Re: shoehorn a 15" woofer / design help

mercury_marine said:

I have 2 of these: http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=290-155 - the Pioneer 290-155 clear poly cone 15 inch woofers. I also have 2 ready cabinets with an internal volume of approx 2.5 cu. ft. unstuffed.


Hi,
Not only are these boxes small, they are really small. To get the most from these drivers you need a big, ported box (about 250 litres - 9 cubic feet!).
Due to the small Xmax (2.5mm), input power would need to be kept below 15 watts - that would give about 105db down to 28hz. Shown below is how that would look.

For the box you have, making it sealed, F3 would be ~60hz at 103db with the input power limited to 15 watts due to the low Xmax. Needless to say, these are not impressive numbers for a 15" woofer
 

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shoehorning

the cabs are Fisher xp9c - built VERY solid, but certainly very small for the 15"ers installed. My budget will not allow any new cab/wood purchases - I gotta work with these. How about joining the 2 cabs back to back and using the 2 Pioneer drivers push pull? Or join the cabs back to back, seal 1 cab face and use only 1 driver? Would I be better off then with a different driver? Again, going for low freq. extension, not thump. Low power, small room. Any recommendations in that arena? Design constraints inspire creativity!:bawling:
 
Assuming this is strictly a 'sub' XO'd below 100 Hz, then using both drivers in an isobaric 'clamshell' layout with the cab tuned to ~Fs and backed into a corner should work OK in a small room. This should get you usable output to ~20 Hz. Not knowing the cab's net Vb or how much volume the driver displaces, all I can recommend is that a 4" dia. x 23" long vent will get you 'in the ballpark' and if the there's any audible 'whistling'/'chuffing' from air moving through the exposed driver's basket, then wrap the motor and frame 'legs' with felt.

GM
 

MJL21193

Disabled Account
2007-03-10 1:20 am
GM said:
Assuming this is strictly a 'sub' XO'd below 100 Hz, then using both drivers in an isobaric 'clamshell' layout with the cab tuned to ~Fs and backed into a corner should work OK in a small room.

Yes! I didn't think of that.

By joining both boxes together, a total volume of ~134 litres is available (I subtracted some for the driver volume and the vent plus any bracing that might need to be installed). The compound loading in this volume shows an F3 of 28hz and flat response down to it.
Drivers could be parallel, with a max 30 watts in.
 

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if the shoe don't fit...

Thanks all. I think I'll save those Pioneers another decade for another project...another time. These boxes were meant for something else. Thanks to everyone for their comments. I'll play with that WinISD program as well - seems pretty easy to ballpark stuff with it. I really do appreciate the help. I have a much easier idea in the works as well; I'll come here again to pick brains. Lots of good reading to be found on these forums too. Ciao.
 
hmmmmm.....

So...we're talking both cabs back to back or face to face? 1 driver out of phase? Or 1 cone firing into the back of the other cab (opened) into the rear of the other driver (both in phase)?

MJL21193 said:


Yes! I didn't think of that.

By joining both boxes together, a total volume of ~134 litres is available (I subtracted some for the driver volume and the vent plus any bracing that might need to be installed). The compound loading in this volume shows an F3 of 28hz and flat response down to it.
Drivers could be parallel, with a max 30 watts in.
 
You would join the boxes so that there's one big box volume (Vb) and only one driver cutout, then mount one driver in the box normally and the other attached to it, face-to-face, wiring one driver in-phase and the other in reverse phase.

Since you need as much Vb as practical, I recommend running the vent outside the box.

GM