Rep Power: 250

i was looking at memphis enclosure recommendations for the M3154d sub and it says for a 1 sub optimal that it needs 3.5 cubic feet tuned to 36 hz and a port of 15.5X1.75X17. well when i figured my box dimensions and got the box volume and plugged it in that came to a Fs (tuning frequency) of 31 hz not 36. i then used winisd and put in all the t/s parameters and same box volume. that program said that i only need a port length of 11.60 not 17 for a Fs of 36 hz.

Also when building a port can you use the wall as a side of your port if you take in effect the error correction factor. or should you go off of the wall. only reason i ask is because my enclosure is built to fit my civic and if i change the size it messes up the box volume. the way it works best for me is if i use the side of the enclosure as part of the port.

any suggestions would be awesome. im so confused by all of this and what memphis recommends. what should i do guys?

 
Rep Power: 256

ive used the side wall as one side of a port before. built a dual slotport and used the center piece between the 2 chambers for one side of each port.

 
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^^^^^^ do you know anything about tuning frequency though. I hope i mad since above. should i use the port length of 17" or of 11". the only difference is lower frequencys.

 
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what are the rest of your box dimensions?

 
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the height is 17 the width is 24 and the depth is 19 i believe those are the final measurements i come up with

 
Rep Power: 263

Why not try both and listen for a difference? T/S parameters are like most other sciences, true in theory but the real world is a little different. Room/vehicle acoustics play such a role in bass sound I would just try both lengths and then you can decide which is better.

 
Rep Power: 250

how would i try both lengths without having to build two seperate boxes? Also im going to use the side as one of the port walls so is that measurement of 11.60 in winISD figuring in the error correction factor or not? its usually .732 for one flanged side and one open side.

 
Rep Power: 263

You could use actual ports instead of a slot. Don't even have to worry about correction factors. Just pull one out and put the other in. Just a thought, that's what I just did for my home sub.

 
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yeah, i want to go with the slot port though.do you think i should go with the 11.60" or the 17". the 17" would give me i believe a frequency of 31.33hz and the 17" would give me a frequency of 36hz. do you know of anyone on here that has experience in building box's?

 
Rep Power: 263

Well, how low do you want to go? The most recent box I built was a 15" home sub with 8 cubic feet of airspace, dual 4" diameter ports of 11" depth and it is tuned to about 35 Hz. That tuning was measured in an anechoic chamber and the expected was about 36 Hz from our software. I couldn't be more pleased with how low it plays. Remember, every additional inch of port space takes air space away from the sub. 31 is very low but not much lower than 36 Hz.

 
Rep Power: 250

yeah i have it figured out. im going to use the memphis enclosure specs. now when they give you the size of the port to use, is their length figuring that your using a side of your enclosure as a port wall or not. meaning are the following the rules as being the width away from any walls and speakers or did they assume you would build it along the wall?

so if i use the wall as a side of the port and i use the 17" length does that include the error correction factor or not? will i have to angle my port into the box to get the 36hz frequency im looking for? im going to use a slot port not a rounded one, just so you guys are aware. thanks for all the help.