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Stereo Integrity HT18 Vented - Newbie Build

post #1 of 21
Thread Starter 
I am about to undertake my first subwoofer build and would like some feedback on my box design before I begin.

I will be using a single Stereo Integrity HT18 in a large ported box with the goal of 115+ dB from about 80Hz down to below 20Hz.

Box Parameters:

External Size: 24" x 24" x 75"
Net Internal Volume: 18 cubic feet
Port: 18in x 6in x 45in
Port Velocity: 9.3 m/s @ 20Hz (lower as freq. increases)
Tuning: 17.56Hz

The speaker will mount in a down-firing configuration in a 24" x 24" x 2.25" baffle and the port will exit the opposite end (top).

Does this look like a good plan or am I missing something?

Thanks in advance for looking.
post #2 of 21
Huge box, might want to use 2 drivers with that.
post #3 of 21
2' x 2' x 6' long....wow how many hundreds of lbs is a box that size?

Would 2 smaller be better for flat multi seat response?
post #4 of 21
Thread Starter 
I may build a second one if needed. My main question is will this size box work well with the HT18 driver? It looks good to me in winISD but I don't have any real-world experience.
post #5 of 21
2 drivers forsure.
post #6 of 21
Dang, if you are going that big, you would save a WHOLE lot of coin and time by just doing exactly as you planned out, but use a sonotube instead of wood. I did a set of 24" outside diameter sono's 6 feet tall in less than 24 hours a while back. at 25cuft internal volume and my port length, they are tuned to 11hz and they absolutely POUND
post #7 of 21
Quote:
Originally Posted by swtfman View Post

I am about to undertake my first subwoofer build and would like some feedback on my box design before I begin.

I will be using a single Stereo Integrity HT18 in a large ported box with the goal of 115+ dB from about 80Hz down to below 20Hz.

Box Parameters:

External Size: 24" x 24" x 75"
Net Internal Volume: 18 cubic feet
Port: 18in x 6in x 45in
Port Velocity: 9.3 m/s @ 20Hz (lower as freq. increases)
Tuning: 17.56Hz

The speaker will mount in a down-firing configuration in a 24" x 24" x 2.25" baffle and the port will exit the opposite end (top).

Does this look like a good plan or am I missing something?

Thanks in advance for looking.

which version of the driver are you planning to use - D2 or D4? what power?

the port dims look suspicious. 18x6x45 is huge. 9 m/s air velocity is too conservative. you can safely double or even triple it. I am trying to stay under 30m/s. what kind of first resonant frequency numbers are you getting?

I have settled on 16cu.ft. with 15Hz tune using D4 driver. the port will approx be 8x3x22
post #8 of 21
Quote:
Originally Posted by zheka View Post

which version of the driver are you planning to use - D2 or D4? what power?

the port dims look suspicious. 18x6x45 is huge. 9 m/s air velocity is too conservative. you can safely double or even triple it. I am trying to stay under 30m/s. what kind of first resonant frequency numbers are you getting?

I have settled on 16cu.ft. with 15Hz tune using D4 driver. the port will approx be 8x3x22

That does not sound right for the port size, it puts tuning at 12.5hz. 10"x3"x20" is closer to 15hz and has a 340hz first resonance.
post #9 of 21
Thread Starter 
I'm using the D4 with about 600 Watts. What does the first resonant freq indicate? I'll have to get back to my computer at home to check. The sonotube may be a better way to go.
Edited by swtfman - 1/30/13 at 4:21pm
post #10 of 21
With that sized enclosure, after bracing and such, you are probably looking at 5-6 sheets of ply and a monster 500 lb plus enclosure. The sono style needs no bracing, or very minimal at most, and will drop your overall cabinet weight by a good 400 pounds, haha. my two "tubatron" monsters weight in at around 100lbs each and with the benefit of the round enclosure, there is virtually zero vibration in the cabinet. After capping the top and bottom with the speaker baffle and port baffle on top, you can literally jump up and down on it and it won't budge. Ahhhhh the benefits of sonotubes. They are SUPER easy to build. I can't imagine all that woodwork for a wood square box version of the same thing you are proposing, but it is your build, so don't go sono and then later regret it. I am one that like to build as fast as possible so I get to listen sooner smile.gif form factor is negligible in some cases for me for speakers, and in most cases for subwoofer duty biggrin.gif
post #11 of 21
Quote:
Originally Posted by mtg90 View Post

That does not sound right for the port size, it puts tuning at 12.5hz. 10"x3"x20" is closer to 15hz and has a 340hz first resonance.
my bad.
10"x3"x20" it is. you know this better than anybody wink.gif
post #12 of 21
Thread Starter 
Quote:
Originally Posted by beastaudio View Post

With that sized enclosure, after bracing and such, you are probably looking at 5-6 sheets of ply and a monster 500 lb plus enclosure. The sono style needs no bracing, or very minimal at most, and will drop your overall cabinet weight by a good 400 pounds, haha. my two "tubatron" monsters weight in at around 100lbs each and with the benefit of the round enclosure, there is virtually zero vibration in the cabinet. After capping the top and bottom with the speaker baffle and port baffle on top, you can literally jump up and down on it and it won't budge. Ahhhhh the benefits of sonotubes. They are SUPER easy to build. I can't imagine all that woodwork for a wood square box version of the same thing you are proposing, but it is your build, so don't go sono and then later regret it. I am one that like to build as fast as possible so I get to listen sooner smile.gif form factor is negligible in some cases for me for speakers, and in most cases for subwoofer duty biggrin.gif

Do you just use the cardboard sonotube as-is and glue the baffles on? If so I think I will go this route. Thanks
post #13 of 21
Quote:
Originally Posted by beastaudio View Post

With that sized enclosure, after bracing and such, you are probably looking at 5-6 sheets of ply and a monster 500 lb plus enclosure. The sono style needs no bracing, or very minimal at most, and will drop your overall cabinet weight by a good 400 pounds, haha. my two "tubatron" monsters weight in at around 100lbs each and with the benefit of the round enclosure, there is virtually zero vibration in the cabinet. After capping the top and bottom with the speaker baffle and port baffle on top, you can literally jump up and down on it and it won't budge. Ahhhhh the benefits of sonotubes. They are SUPER easy to build. I can't imagine all that woodwork for a wood square box version of the same thing you are proposing, but it is your build, so don't go sono and then later regret it. I am one that like to build as fast as possible so I get to listen sooner smile.gif form factor is negligible in some cases for me for speakers, and in most cases for subwoofer duty biggrin.gif

do you have a link to a good sonotube build thread?
post #14 of 21
beastaudio, I built a sonosub years ago and was thinking about doing pretty much what you did with a pair of the SI18s. I know sonosubs have kind of gone out of style over the years, but it sure made for an easy build. Did you do a build thread?

swtfman, if you go with beast's plan you could take the savings on MDF and buy another driver. Now that would be nice. biggrin.gif
post #15 of 21
Quote:
Originally Posted by swtfman View Post

Do you just use the cardboard sonotube as-is and glue the baffles on? If so I think I will go this route. Thanks

Yep! I used two sheets of auruco and double baffled the bottom and top caps, used PL to seal and screws around the perimeter into the sonotube to secure. see below smile.gif

Quote:
Originally Posted by WagBoss View Post

do you have a link to a good sonotube build thread?

Quote:
Originally Posted by trancemitr View Post

beastaudio, I built a sonosub years ago and was thinking about doing pretty much what you did with a pair of the SI18s. I know sonosubs have kind of gone out of style over the years, but it sure made for an easy build. Did you do a build thread?

swtfman, if you go with beast's plan you could take the savings on MDF and buy another driver. Now that would be nice. biggrin.gif

I sure do guys! My old build thread, which even though it was built out for some Tempest x-2's, the SI 18 is almost a drop in replacement, and I plan on popping two in at this point to try it out smile.gif Just for fun. The 8 sealed 18's is the end-game for me, and I still have four not in boxes right now, so I will just route out the baffle and take two and pop em in to see what I get biggrin.gif Check it:

http://www.avsforum.com/t/1388343/how-easy-to-source-parts-and-build-a-quick-llt

24 hours basically and these two monsters were rockin and rollin smile.gif It took longer for the pl premium to dry than I spent cutting and building it out smile.gif
post #16 of 21
Quote:
Originally Posted by swtfman View Post

I'm using the D4 with about 600 Watts. What does the first resonant freq indicate? I'll have to get back to my computer at home to check. The sonotube may be a better way to go.

I agree with beast, your tall and narrow profile is a natural candidate for the sonotube.

first port resonance is the frequency at which the port turns into a tuned pipe. think flute or organ . you want it to be as far from the subwoofer passband as possible, some say at least 1.5-2 octaves above it. The longer the port the lower the frequency is. Hence the need of the compromise between port air velocity and first port resonance.

Do not use specs from SI website in your model, they are for the D2 version. You will get more accurate results with mtg90 measurements.
post #17 of 21
Thread Starter 
Sonotube it is. Just ordered a second driver too!biggrin.gif
post #18 of 21
Thread Starter 
Quote:
Originally Posted by zheka View Post

I agree with beast, your tall and narrow profile is a natural candidate for the sonotube.

first port resonance is the frequency at which the port turns into a tuned pipe. think flute or organ . you want it to be as far from the subwoofer passband as possible, some say at least 1.5-2 octaves above it. The longer the port the lower the frequency is. Hence the need of the compromise between port air velocity and first port resonance.

Do not use specs from SI website in your model, they are for the D2 version. You will get more accurate results with mtg90 measurements.

Thanks for the explanation and link! It's all beginning to make a little more sense.
post #19 of 21
Quote:
Originally Posted by swtfman View Post

Sonotube it is. Just ordered a second driver too!biggrin.gif
I'm glad to hear you ordered a second. I need to see about placing an order myself.
post #20 of 21
Quote:
Originally Posted by trancemitr View Post

I'm glad to hear you ordered a second. I need to see about placing an order myself.

If you are willing to wait a bit for the d2's the pre-order price is back at $162 as opposed to the regular $190 tag, but June is the best guess for the next shipment to come in for parts :/
post #21 of 21
You could try tuning even lower. I'm planning on a 12Hz tune, possibly lower, for my build.

Here's an excellent article explaining LLT subwoofers:

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/1820-llt-explained.html

And here's my planning thread. I hope to start my build by the end of this month.

http://www.avsforum.com/t/1319223/2-18-llt-sonotubes-preliminary-planning/

There are threads out there for completed LLT sonotube builds. Read as many as you can. It's unfortunate there isn't some master article somewhere that has all the tips and tricks in one spot.
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