port tuning

im going to build a box for a sound stream t4 10.  its going to be ported and the port going to be tuned to 40 hz, but i just want to some tips for tunning the port properly, maybe some ported box secrets or what ever.   if there eqazions or onlince calcs or something to seal the inside of the box with, anything will helpHurry get me a steel hanger, elec tape, zip ties, a monkey and a snorgle. trust me i've ran wires with less

Hmm. If I were building it, I'd port it lower. Maybe 30 - 33 hz would make it much louder throughout a range. Use PVC piping for your port, ya need sumthin rigid. Make sure your port entrance/exit is at least the distance = port diameter away from the woofer cone or the rear of the speaker box or anything at all really. Seal the box up with Fiberglass resin. It's like painting plastic onto stuff. Really fun to play with. Smells great. Any other specific questions?"I'm finished!" - Daniel Plainview

Just shooting from the hip here... like stevdart say no mock-up.... but I betcha tuning it that high with a smaller cone like that would make it ridicuously peaky ... I would fear to the point of being utterly unable to handle transients with anything approaching fidelity. I mean... SPL sub or no I'd still shoot for a flat curve... tuning for the Fs will give you the tinest little bandwidth of bass that is just mindblowing and everything else that's like "I can hear my car rattling, but no sound.." That's been my experience anyway. "I'm finished!" - Daniel Plainview

haha... look stevdart, we were both *right* on with our recommendations, just from different ends! The soundstream "spl" box is a 40hz-er @ 1.7cft while the "SQ" box is a 35hz-er @2.2 cft. Yikes Soundstream woofers are so weird. What's with the big dip after the Fs? I've never seen that in anything I've modeled before except the Soundstream Exact. Anywho, the Soundstream "SPL" Box, modeled in WinISD: ---- Driver            : Soundstream T4 - 10 Project by        : sedate Project for       : hoaxs -- Number of drivers : 1 Box type          : Vented Box size          : 1.700 ft^3 Tuning frequency : 40.00 Hz Vent              : 1 vent(s)                     9.39 in length for each                     4.02 in round                                                                                                                                        Relative                                        Freq        Gain        SPL                                [Hz]        [dB]        [dB]                             20.00        -26.19       -26.19                             25.00        -18.13       -18.13                             30.00        -10.56       -10.56                             35.00        -2.61        -2.61                             40.00        3.77        3.77                             45.00        2.38        2.38                             50.00        0.30        0.30                             55.00        -0.86        -0.86                             60.00        -1.49        -1.49                             65.00        -1.82        -1.82                             70.00        -1.98        -1.98                             75.00        -2.04        -2.04                             80.00        -2.05        -2.05             ----- And the "SQ" version Driver            : Soundstream T4 - 10 Project by        : sedate Project for       : hoaxs -- Number of drivers : 1 Box type          : Vented Box size          : 2.156 ft^3 Tuning frequency : 35.00 Hz Vent              : 1 vent(s)                     9.75 in length for each                     4.02 in round                                                                                                                                        Relative                                        Freq        Gain        SPL                                [Hz]        [dB]        [dB]                             20.00        -22.95       -22.95                             25.00        -14.03       -14.03                             30.00        -4.86        -4.86                             35.00        2.87        2.87                             40.00        0.87        0.87                             45.00        -1.24        -1.24                             50.00        -2.25        -2.25                             55.00        -2.72        -2.72                             60.00        -2.91        -2.91                             65.00        -2.95        -2.95                             70.00        -2.91        -2.91                             75.00        -2.82        -2.82                             80.00        -2.71        -2.71 Now, personnaly, I think this second curve here looks great. That 10dB drop from 40 - 30 hz on the "spl" box kinda scares me .. like I say "peaky" ... but the upper extention actually looks really good either way.             "I'm finished!" - Daniel Plainview

Oh yea... on sealing an enclosure.. use Liquid Nail on all the joints before you press them together, then seal the inside of all the joints with it, make it spread nice and even everywhere wood comes together. After it dries, apply fiberglass to the *entire* inside of the box, just paint it on nice and thick. It'll really help seal anything you missed w/ liquid nail AND add a tremendous amount of rigidity. On the other hand, if you're using 3/4" MDF, it really wouldn't be required. If you are gonna fiberglass though, lighten your load a bit and use 1/2". WAYYY easier to work w/, IMO. Also, use coarse thread deck screws to put your box together .... ALWAYS use deck screws to attach ur woofer as well. NEVER have to tigheten it up eh? No fine thread wood screws okay? They don't do nearly as well with all that shaking. "I'm finished!" - Daniel Plainview

thanks you guys for the help.  i usally do use ligued nails for sealing and 34 mdf and 2inch cousre thread screws.  but from what understand is that the spl box woould be good but to be carefull around other frqzys.   other than 40hz.  im a little confused on the part where sedates said "peaky"Hurry get me a steel hanger, elec tape, zip ties, a monkey and a snorgle. trust me i've ran wires with less

"peaky" ... like there are big jumps in the response of the speaker. Certain frequencies will play MUCH louder than others. Generally, unless tuning for a competetion or something where you know what frequency you need to play and for how long, you want the flattest curve possible. These are the curves for your speaker, the red line being the "SQ" box. I think the "sq" box is so big so that dip after the Fs will be minimized... Anyway, notice how the falloff on the green curve is drastic? Like it drops almost 11dB from 40 to 30 hz. From my experience, drops like that tend to produce really uneven bass-lines and, unless ur car is well damped, produce more trunk rattle than bass. The fall off on the red curve is there, but wayyyy down into the sub-30hz range, where you really can't hear a whole lot and where you aren't gonna get a 10" to play anyway. The red curve manages +-3dB from reference all the way to about 80hz which is about where you'd want to cross it. "I'm finished!" - Daniel Plainview