New member and new sonotube!

[xLoSx]

Well after reading straight for about a week I have decided on the type of sub I want to go with... and it is a sonotube sub..

I will either be using a 15" tempest from adire or a soundsplinter rl-p15 from tc

I had a few hard size limits and those were 60" tall and 20" wide! (Already purchased)

That gives me about 252L after you take out the port volume the sub volume and the ends.

(8" sonotube x 48" already purchased as well)
I want to go with an 8" port for the slow air speed but thats where my problem comes in... A 17Hz tune requires 49.5" port I figured 48" + .75 cap thats flared is fairly close to that length.

Now with my 48" tube I have 12" left for the sub which is 9 - 10" in height! So im assuming that my port is way too close to my sub... (2" gap) Should I rework it and get a 6" port instead? Which would be 24 1/2" long?

Also air velocity with the 8" port is 23 vs the 6" port which is 46"

Im afriad the 6" port will cause some chuffing or other port noises... however the 6" port would be far enough from the sub and I could increase the tune to 15Hz requiring 33" of tube but still gives me a good gap between the sub and port...

So after all that is it ok to have the rear port only 3" or so away from the sub or should I rework it and use a 6" port and suffer the possible noises that get introduced?!

[ThomasW]

The audibility of mach numbers is a subject much debated.

Another issue is that ports over ~30" or so long start having issues with resonances.....

So....

I suggest the 6" and realize that the mach differences probably aren't going to be audible at any sane SPL.

If you want to improve you chances go with 6" flared posts. You can make your own here's a link or you can buy them.

http://2loud4you.ca/shop/index.php?main_page=product_info&products_id=3&zenid=b915fc78891bb55ba2461d9f56376034

[xLoSx]

What do you consider as 'sane' SPL?

[ThomasW]

A comparitive term.... So you understand, below is my AS-15 sub with the 6" flare kit. Using an Aragon 8008 for power, I can shake my 2500 sq ft brick house and not hear 'chuffing'

I didn't bother to measure the SPL, but it was certainly LOUD....:wink:



Similar situation for the tube sub I designed and built for my friend Pete

[xLoSx]

That tube sub is actually (and the thread associtaed with it) one of the pages I have bookmarked for reference!

Ok I decided to just bit the bullet and go for a 6" flare which increase my volume significantly!!!

282L with a 29" Flared 6" Tube Port Speed Max of 44m/s but its only > 25 m/s between 17Hz and 10Hz.

When I add in a highpass filter at 12Hz to keep cone excursion under control my port speed maxes around 27m/s at 14Hz.... actually turns out to be just about as nice as a 8" port....

So hopefully thats all the changes I need and im set

[ThomasW]

The box model will change just a bit. The pipe supplied with the flare kit is to short, so you'll have to find green sewer pipe to make a longer one. It's ID is 5- 7/8 if I recall correctly....