Port diamerter questions

[mrbobian 0]

Well it's time to move my set up from the S10 to the 325ix and have been crunching numbers to draw up a box. Right now I'm running my Q10 sealed at about 0.4ft^3 on a SAE-1000D at 2ohms. I will have considerable more space in the trunk of my car so Im wanting ported tuned to 27~28hz. I planned everything out so at net box volume of 1ft^3 I can use 3'' PVC at 22'' length to get 28hz. Now i'm no expert at enclosure design but I feel one 3'' port not flared will be too small? Pi*1.5^2= 7.06in^2 of port area. Id like some opinions on the matter. What do you guys think? Thanks,

Mike B.

[KU40 173]

I would agree that one 3" port would likely be too small. A single 4" flared port should be fine though, or maybe 15-20 sq. inches in a slot port.

[///M5 2,833]

27hz is pretty low and 3" is pretty small. Could be fine in the trunk though, depends on your listening preferences and goals which you didn't share

[mrbobian 0]

I would love to try a 4'' flared port but fear it would be too long especially if I want it tuned so low.

As for my goals, I trying to essentially build a solid daily setup that sounds clean. I wish I could say SQ but I don't have the time or money to build a decent front stage while in college. I like my basslines LOW and smooth. I listen to everything from house to rock to hip-hop. The Q performed fine sealed in my truck but am looking for something a little smoother and a bit louder for the new setup. I have no idea really how things will change going from and ext cab truck (that hardly had any low response with the windows up) to a 2 door car with a sub in the trunk.

[KU40 173]

Your 4" port would need to be 43" long to tune it to 27 hz. That's about .3 cube worth of displacement. So the overall box with sub displacement would need to be about 1.5 cubes gross.

The 3" port would displace about .1 cube. Would that extra .2 cube really be noticeable? But more of a problem would probably be getting the port to fit inside the box since it would have to bend so many times. That's where a slot port can help a bit, because it may be easier to bend a 1.25" wide slot port back and forth along the same side of the enclosure than a 4" round port. But I suppose with the round port you could run it from the front to the back wall, turn 90* and follow the back wall, then use a "U" shaped connector and run the port along the back wall again, just above the first port section.

[///M5 2,833]

I think you could raise your tuning a bunch as well.

[mrbobian 0]

Why do you suggest I raise my tuning?

[hispls 23]

Why do you suggest I raise my tuning?

I suspect because you would notice little to no difference between 28 and 33hz and considering your space restrictions, it might make things more realistic.

[mrbobian 0]

Okay, so after finding some info on an E30 specific forum, it sounds like I could reevaluate things. One guy (with quite a lot of experience) says in the E30 cabin there is a big bump at around 40hz, no output from 60-80hz then a peak at 100hz again (I won't have my sub handle that tho.) Anyway, it was suggested I start at 35hz for tuning and then make adjustments since I plan on using PVC as a port. My only question with that is, if i'm tuned that high and have set my HPF correctly won't I have significant loss of any response below that? And that would kill the whole point of having a sub. I need to hear the low note in "Put On'' or the whole dirty wobble bassline in dubstep. Or am I thinking completely wrong?

[KU40 173]

My box is tuned to 30 hz and I hear every note in "Put On" just fine. However I'm not sure I'd like to play that note with a tune much higher. The subsonic filter would have to be raised in that case, perhaps above the note in the song. I'm not sure what frequency it's at though.

[JayR04 0]

27hz (the lowest bass note) if im using audacity correctly.

[mrbobian 0]

27hz (the lowest bass note) if im using audacity correctly.

Thanks for looking that up, damn that is low. But exactly why I would hate to kill it with a crossover. I figured out a way of getting 28hz with a single 4'' port in ~0.9cuft box. I don't really see any problems with tuning low other then losing output, but I'm not really interested in being crazy loud. I doubt my 5-1/4'' will be able to keep up with the Q anyway.

I'll post up box plans shortly. Just working out all the details.

Mike B.

[mrbobian 0]

Spent a few hours drawing some stuff up in NX5 (this is what happens when you go to an engineering school) I plan on sealing it up to the rear firewall firing into the cabin of my E30.

I figured that I can get roughly 27.5hz using 4in PVC. Just a few fitment issues to work out but this is the general idea. Tell me what you think.