Questions on an unusual variant of the Martysub. - AVS Forum
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post #1 of 13 Old 02-16-2014, 05:26 PM - Thread Starter
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After being without a working home theater setup for over 2 years, my wife is begging me to set everything up again. biggrin.gif My original sub, a Velodyne 10, was destroyed by a mouse that thought the paper cone was fun to chew on. mad.gif I've been looking to build a sub for quite some time. Well, the Stereo Integrity closeout was too good to pass up, and I just had to order 2 18's. After stumbling upon the Martysub, I've already decided what I would like to do, but I am looking for help to, 1. see if you all think my idea will even work, and 2. see what my changes do to the design of the Martysub. So, here's what I'm thinking. I would like to build my box to be a tv stand. I know this may not be the optimum placement, but the way our living room, which is our main viewing room, is laid out and our furniture that's in there, I don't have many options for sub placement. Especially one large enough for 2 18's. I have a Panasonic 65", so I'm looking to build the box to be 24" high x 30" deep x 72" long. I can easily go up to around 80" long if that will make things work better. I thought about just building 2 enclosures like this variation, and using trim to hide the gap between the enclosures, but I would really like to have the subs dual opposed to cancel the vibrations. So, do you guys think this will work, and how will it affect things, like port length? I have used WinISD before, but get mired down in the minute details, since I'm a novice.
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post #2 of 13 Old 02-16-2014, 07:18 PM
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congrats.

placement will be a wild card, so i'd suggest 2 cabs instead of one, that way you can move them around, but otherwise...

YES! those two cabs, back to back, will perform the same whether the rear wall of each sub is actually there or not. no changes to port length or size of the subs would be required.

various finishing techniques could really spruce it up!


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post #3 of 13 Old 02-26-2014, 10:12 AM - Thread Starter
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I love the look of that sub. Hopefully I can end up with something similar to that. I ordered 2 of the SI HT 18 D 4's just a few days before they sold out. biggrin.gif I guess I'll lay out my design now that I have it pretty well planned out. I would love for someone with more experience to please double check all my figures.

Since you talked me into it LTD02, I suppose that I'll go with 2 separate enclosures. biggrin.gif The enclosures will both be 21" tall x 30" deep x 40" long. The port will go on the rear wall, from the floor to the top (like this I, not like this_). I will end up with three 3" x 6" x 58" ports (that is measuring the inside wall of the port). I plan to recess the double baffle 1.5" to give me room for whatever I decide to do for a grill. I'm figuring this will get me to about 9 cu. ft. before any bracing. In WinISD, I figured my box at 8.75 cu. ft. to allow for some bracing, which gives me a tune of 16-17 Hz. Hopefully my figuring is correct.

The plan after that is to build a table to go over the sub boxes that ends up at about 32" x 82". The legs on the front will be "L" pieces that go around the front corners like the guy did in the picture that LTD02 posted. Then on the back I will just use one board for the legs. I will also use one board in the middle on the front to hide the gap between the enclosures. Now I just have to figure out how to best finish everything off.
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post #4 of 13 Old 02-26-2014, 02:25 PM
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just a heads up...check your first port resonance in winisd. that can create a hiccup in the frequency response if too close to the passband.

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post #5 of 13 Old 02-26-2014, 09:54 PM - Thread Starter
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Well, WinISD says the 1st port resonance is 119.53 Hz. I'm still new to this, so I have no idea whether that is good, bad, or not a problem.
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post #6 of 13 Old 03-03-2014, 01:24 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

just a heads up...check your first port resonance in winisd. that can create a hiccup in the frequency response if too close to the passband.

Thank you very much for this question, because due to the lack of response to my answer I posted to LTD02's question, I was forced to go digging for an answer. From my research, I realized that a first port resonance of 119.53 Hz is too close to the passband, since I plan to cross over to my subs at 80 Hz. And it definitely would be a problem if I decided that I needed to cross over at 120 Hz for some reason. So, this sent me doing more research and re-reading of posts that I initially just kind of skimmed over. rolleyes.gif Upon doing this, I realized that my numbers were off quite a bit. redface.gif Starting with the original MartySub design here, I noticed that LTD02 was figuring his port with the braces as just one port, not 3 separate like I was. It didn't change my numbers much, but it did change them some. Then I noticed how short his port design was compared to what I was thinking. I realized that I was shooting for too low of a tuning point, and that I don't necessarily have to keep the port velocity below WinISD's recommended 17 m/s. Not to say that this speaker won't handle the lower tune, but as several more experienced have posted, due to end correction, WinISD is figuring the tuning too high compared to real world results. I'm not looking for high SPL single digit output, but I'd like for some good output in the teens, and 16-18 will be fine. For goodness sake, like I stated earlier, my last sub was a single 10" Velodyne that I last used over 2 years ago, and now I'm starting over with these beasts. TWO 18" SUBS!!!! I must be nuts. biggrin.gif I'm sure I'll enjoy them at that tune just fine. I also found this thread where jfreeman420 is building subs that are very similar dimensions to mine. The dimensions are only off just a little, and driver and port placement will be different, but I was able to glean some good info from there as well. So, anyway, on to the numbers.

Sub design 2.0 tongue.gif. I decided I will adjust the exterior dimensions just a smidge to 21" tall x 28" deep x 40" long. For anyone checking my numbers, I am figuring everything with .75" thick wood. With a double baffle, and a 1.5" recess of the baffle for a grill that puts me at 10.8 cu. ft. before the port, driver or any bracing. The port will have 2 supports in it, so I will end up with a 2.5" x 18" x 33.75" port (these are the internal dimensions of the port, actual port length will be 36.75"). I'm figuring the port will eat up 1.2 cu. ft., so with the port, driver, and bracing, I'm figuring that puts me at about 9 cu. ft. WinISD figures that to be tuned to 17.8 Hz with a first port resonance of 184 Hz, and that puts the port velocity at 18.7 m/s with a 600W signal. Hopefully these numbers will look much better. If someone sees that I'm off, please tell me. I'd rather know now, than after I've got wood cut. biggrin.gif
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post #7 of 13 Old 03-03-2014, 06:00 PM
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sub design 2.0. :-)

nice work. everything looks right from over here.

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post #8 of 13 Old 03-03-2014, 06:41 PM
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Quote:
Originally Posted by knobturner75 View Post

was destroyed by a mouse that thought the paper cone was fun to chew on. mad.gif

eek.gif

A mouse ate my homework.
I mean, a mouse the size of a rat...
I mean, a rat the size of a small dog...
I mean, my dog ate my subwoofer... nevermind teacher, I'll just work harder on the next assignment, ok? LOL biggrin.gif

Dude that's one strong mouse, you should set up a bear claw to catch it!!! wink.gif

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post #9 of 13 Old 03-03-2014, 08:06 PM - Thread Starter
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Originally Posted by LTD02 View Post

sub design 2.0. :-)

nice work. everything looks right from over here.

Thanks for double checking for me. I feel better now that someone more knowledgeable than me has set me straight. biggrin.gif
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post #10 of 13 Old 03-03-2014, 08:31 PM - Thread Starter
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eek.gif

....Dude that's one strong mouse, you should set up a bear claw to catch it!!! wink.gif

Well, the little sh@t crawled in the slot port and set up his home there. I used the sub daily, and could not believe that it lived in there. The mouse chewed on the back of the paper cone when the sub was not being used, basically shaving the paper off in a large area. I heard the scratching a few times, but thought it was chewing on a cardboard box that was nearby. Then one day, I cranked up the volume and my sub had this bad cracking noise when it hit hard. mad.gif Gotta love the little pests. biggrin.gif
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post #11 of 13 Old 03-03-2014, 10:14 PM
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Get a Ferret. Sabretooth Mouse Killer. smile.gif
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post #12 of 13 Old 03-03-2014, 10:18 PM - Thread Starter
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Get a Ferret. Sabretooth Mouse Killer. smile.gif

Hadn't thought about a ferret. The wife wants a cat, but my 2 kids and myself are allergic. Living near some big fields has it's downsides.
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post #13 of 13 Old 03-03-2014, 11:01 PM
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Sounds like you need a Fox then. Ferrets are hilarious pets but equally damaging if you give them free roam of the house. We developed a smell after awhile and caught the Ferret at night going thru the trash and storing leftover chicken and baked potato parts in the lining under the couch! Little basterk had torn a hole in the middle and stored food on one side and slept on the other like a Feret Hammock.
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