HELP with SI 18 ht -4 sonotube build - AVS Forum
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post #1 of 17 Old 08-14-2013, 11:16 AM - Thread Starter
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After much research I'm deciding to build two separate SI 18 ht-4 ported sonotubes but I see that most everyone is building bigger volume tubes tuned below stereo integrity's spec's ( 20 htz tune ) but a big contributor in the DIY sub world has this in mind, 72 inch tall, 26 inch round sonotube with an 8 inch X 40 inch Port gets you 11 hz tuned.
Would this be too low ? as in loosing the parameters of this driver, I wouldn't mind being able to feel movies
For movies and music what would be the ideal size and tune for the stereo intergrity's 18 ht-4 for a ported sono ? My dedicated room is 23 x 36 x 12

Any help would be much appreciated
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post #2 of 17 Old 08-14-2013, 12:02 PM
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The lower you tune the more your output looks like a sealed system above tuning. You have to decide how much ULF you can live without. 10hz? 15? 20?

11hz is fine if that's what you want.
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post #3 of 17 Old 08-14-2013, 12:16 PM
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The lowest I would go for is 15hz, just because there is only a few movies that go below that.

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post #4 of 17 Old 08-14-2013, 12:18 PM
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"For movies and music what would be the ideal size and tune for the stereo intergrity's 18 ht-4 for a ported sono ? My dedicated room is 23 x 36 x 12"

that is a personal preference. there is no right answer. below is max spl of the proposed sub (thin green) and one that is 13 cubic feet tuned to 15hz (thick green). more extension means a little less headroom slightly higher up.



" a big contributor in the DIY sub world has this in mind, 72 inch tall, 26 inch round sonotube with an 8 inch X 40 inch Port gets you 11 hz tuned."

that is about 20 cubic feet net. 8x41 port gets you ~12hz tuning, so you are right on, if that is what you want.

you'll have to be careful with power, as only 500 watts or so will push the driver to near its xmax. much more than 1000 and you may start to get into the red zone.


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post #5 of 17 Old 08-14-2013, 12:46 PM - Thread Starter
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I'm thinking 4-5 more db with a 14 hz tune, it's a a big room I'm thinking i will need as much SPL as I can, am I wrong ?

18.jpg 143k .jpg file
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post #6 of 17 Old 08-14-2013, 01:12 PM
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I have almost exactly what you are planning on building. My 2 are in 24" sonotubes, 6' tall without stands tuned to 11Hz w/ 18 cubic feet net internal volume powered by an ep4000 in stereo mode wired for 2ohms per channel. This setup works very well for me as it sounds like a sealed system for most music and still has the extension for movies. Running sweeps down to 10Hz will make my entire house shake. One thing to keep in mind with such a low tune is port resonance near your intended listening freqs, my ports are made of 6" schedule 40 pvc about 31.8 inches long which gives a first resonance at 212Hz. The other issue is standing waves inside the tall enclosures, I used eggcrate foam on the inner walls and a few pillows in each enclosure to effectively eliminate them.

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post #7 of 17 Old 08-14-2013, 01:23 PM - Thread Starter
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Why would you need to put a ep4000 per driver ?
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post #8 of 17 Old 08-14-2013, 01:26 PM
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Quote:
Originally Posted by sparkky1 View Post

I'm thinking 4-5 more db with a 14 hz tune, it's a a big room I'm thinking i will need as much SPL as I can, am I wrong ?

18.jpg 143k .jpg file

 

Your room is huge, almost 10000 cu ft. Probably best to tune as high as possible to get the most spl. You'll probably want to use a highpass filter at it tuning freq (14hz) to protect the driver from bottoming out.

 

 

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Originally Posted by sparkky1 View Post

Why would you need to put a ep4000 per driver ?

 

The EP4000 can put out 800w at 2ohm stereo so its enough for two low tuned subs.

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post #9 of 17 Old 08-14-2013, 01:33 PM
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Quote:
Originally Posted by sparkky1 View Post

Why would you need to put a ep4000 per driver ?

I just have 1 ep4000 powering 2 subs, the wording I used is a little confusing.wink.gif

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post #10 of 17 Old 08-14-2013, 01:39 PM - Thread Starter
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would somebody mind sizing a 14hz tuned sono with the SI 18-4ohm with say 800 watts 2ohm , is that the only 2ohm amp that would do 800watts stereo, berry / peavey ?
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post #11 of 17 Old 08-14-2013, 02:28 PM
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Looks like 25 cubic feet tuned to 14Hz would give reasonably flat response. Using a single 6" sch. 40 PVC cut to 12 inches would work well for the port with a first resonance of about 560Hz. With 800W it models between 115-117 dB.

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post #12 of 17 Old 08-14-2013, 02:53 PM - Thread Starter
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What would the volume ( liters ) be, how long would the sono be ?
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post #13 of 17 Old 08-14-2013, 02:57 PM - Thread Starter
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707 liters ?
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post #14 of 17 Old 08-14-2013, 04:17 PM - Thread Starter
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How does this work for 14hz tune, 26in sonotube, end cap to end cap 72.09in with an 8in port 28.82in long ?
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post #15 of 17 Old 08-14-2013, 05:53 PM
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Quote:
Originally Posted by sparkky1 View Post

How does this work for 14hz tune, 26in sonotube, end cap to end cap 72.09in with an 8in port 28.82in long ?


That looks to be about 22 cubic feet which models ok (yellow) but you can get a little more if you increase the volume to 25 cubic feet (aqua).Created with GIMP

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post #16 of 17 Old 08-15-2013, 02:33 PM
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here is si18 with 800 watts in 16 cubic foot cab tuned to 14hz with one 8" diameter port that is 37" long. no filters on this one. a protective high pass would be recommended.

frequency response looks fine for a large room with little or no gain. cone excursion is fine at just a hair over xmax (which is actually around 22mm not 20mm in the picture).





watch your cone excursion as you make the cabinet larger and/or add more power. in an LLT it is more likely that the driver will be damaged *above* tuning.

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post #17 of 17 Old 08-15-2013, 03:38 PM
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Go for the lower tune and thank me later! I have had 25hz tuned, 20 hz tuned, 16 hz tuned, 13hz tuned, 12 hz tuned, and sealed into single digits and while the higher tuned subs gets most of everything the lower tuned subs gave the most accurate and satisfying results. There are things in movies you start to notice that you never felt before, etc..

Here is what I would build



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