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post #31 of 292 Old 08-25-2014, 07:39 PM
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Quote:
Originally Posted by LTD02 View Post
not sure if the name would better be martysub 8.0


a 2.5" x 44" port and about 10% correction yields about 18.5hz tuning. first port resonance is about 140hz, which is pushing it, but should still work. air speed is good. cone excursion is good.


Dayton 18" with 1100 watts. si 18ht will pretty much be identical.


Is this Johnny Model 7 or 8 cuft ??

LTD could you please explain how you calculate Port Lengths ? I can't seem to figure out the Method used between this new model other Marty's ??

This model I calculated Equivelant round port (8.46") Diameter , 8cuft, 18.5hz, which come to 49"length ,.-10% = 44"length , Just like your calculation.

..But this method does'nt seem to work with the Cube's Port Length ?

Thanks .

Last edited by randyc1; 08-25-2014 at 09:20 PM.
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post #32 of 292 Old 08-25-2014, 08:23 PM - Thread Starter
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Its ~7 cuft. 2' by 25.5" by 32"
Exactly in between cube and minimarty . Cube is 5cuft and minimarty is 9 cuft.
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post #33 of 292 Old 08-26-2014, 01:45 AM
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"LTD could you please explain how you calculate Port Lengths ?"


roughly winisd exact length - 10-15% or so. that accounts for a number of things and gets you within +/- a hz of target. at this point, there are so many different designs that some may have used other methods. I didn't calculate the lengths for all of them...

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post #34 of 292 Old 08-26-2014, 10:00 AM
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re se 15 in this box. 600 watts. member request.


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post #35 of 292 Old 08-26-2014, 01:39 PM
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Quote:
Originally Posted by LTD02 View Post
"LTD could you please explain how you calculate Port Lengths ?"


roughly winisd exact length - 10-15% or so. that accounts for a number of things and gets you within +/- a hz of target. at this point, there are so many different designs that some may have used other methods. I didn't calculate the lengths for all of them...
Thank you LTD !
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post #36 of 292 Old 08-26-2014, 02:34 PM
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24"x25.5"x32" external nets about 7.0 c.f. internal btw.


edited to correct.

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Last edited by LTD02; 08-27-2014 at 03:27 PM.
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post #37 of 292 Old 08-27-2014, 10:28 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
24"x25.5"x32" external nets about 8.5 c.f. internal btw.
Ok thanks ,
Will make changes. Um18 will work then .
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post #38 of 292 Old 08-27-2014, 03:20 PM
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My bad. You were right.


I just measured again. Looks like about 7.5 cubic feet before driver and bracing, so it will net about 7.0 cubic feet +/- a little.


With a 2.5" tall slot port with two slot braces and 44" length, tuning will be around 19.5hz +/-.


form factor:





Performance of three drivers at 1100 watts.
black = stereo integrity 18HT aka SI 18HT
green = Dayton RSS460HO aka 18HO
red = Dayton UM18




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Last edited by LTD02; 08-27-2014 at 03:26 PM.
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post #39 of 292 Old 08-27-2014, 03:33 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
My bad. You were right.


I just measured again. Looks like about 7.5 cubic feet before driver and bracing, so it will net about 7.0 cubic feet +/- a little.


With a 2.5" tall slot port with two slot braces and 44" length, tuning will be around 19.5hz +/-.


form factor:





Performance of three drivers at 1100 watts.
black = stereo integrity 18HT aka SI 18HT
green = Dayton RSS460HO aka 18HO
red = Dayton UM18




That's impossible .... definitely the last time that happens.
I have safely run 1500 watts to dayton driver to reference many times. I like the look of Dayton way better. If they had the dayton with dvc I'd never buy si.
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post #40 of 292 Old 08-30-2014, 12:49 PM
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Now that i have talked my wife into a larger endtable "subwoofer" I am thinking about this design over the MartyCube. My exterior dimensions would need to be altered slightly though since i would like to make this down firing and my max allowable height is 24". So I was thinking my exterior dimensions excluding the 4" tall legs would be 20" high x 24" wide x 35" deep. This would give me a little bit less volume but I don't think it would be enough of a difference to affect performance. Can someone calculate what my volume would be for this box and possibly model it with the SI 18 and 1100w? Thanks.

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post #41 of 292 Old 08-30-2014, 11:04 PM
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@squiers007 that will work fine. it will be about 1/3 of a cubic foot smaller, which will raise the tuning by half a hz or so.

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post #42 of 292 Old 08-31-2014, 10:01 AM
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Quote:
Originally Posted by LTD02 View Post
@squiers007 that will work fine. it will be about 1/3 of a cubic foot smaller, which will raise the tuning by half a hz or so.
So about a 20hz tune then? That's with a 44 in port length?

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post #43 of 292 Old 08-31-2014, 10:04 AM - Thread Starter
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Quote:
Originally Posted by squiers007 View Post
So about a 20hz tune then? That's with a 44 in port length?

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Add two inches to port length and you will keep 18hz tuning .
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post #44 of 292 Old 08-31-2014, 10:24 AM
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Quote:
Originally Posted by chalugadp View Post
Add two inches to port length and you will keep 18hz tuning .
46" it is.

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post #45 of 292 Old 08-31-2014, 01:18 PM
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Quote:
Originally Posted by chalugadp View Post
Add two inches to port length and you will keep 18hz tuning .

two inches will lower it that much? in my subs every inch added only lowered the tune by 0.1hz according to John.
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post #46 of 292 Old 08-31-2014, 01:22 PM - Thread Starter
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Two inches will lower it about 1/2 a hz. From 18.5 to 18. I have found 4" equals about 1hz.
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post #47 of 292 Old 09-05-2014, 09:39 AM
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Quote:
Originally Posted by chalugadp View Post
Here is cutlist

Will add everything to post one. Once the first one is built and confirms that it sounds good I will then add this design to martysub FAQ .

I think I am going to use Dayton 18" ho driver. Ive been running the 15" ho driver with 1500 watts and no issues. The 18" with 1500 watts gives me another db.

Would like to put a uxl18 in there but too costly for me.
What's the size of the front?

Last edited by mR_Mo; 09-05-2014 at 09:43 AM.
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post #48 of 292 Old 09-05-2014, 10:02 AM - Thread Starter
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What's the size of the front?
Wow that's embarrassing . Ill fix it today.
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post #49 of 292 Old 09-05-2014, 02:28 PM - Thread Starter
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Front baffle is 27.25" high by 24" wide.
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post #50 of 292 Old 09-06-2014, 04:18 PM
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Quote:
Originally Posted by chalugadp View Post
My front corner of my living room could fit a bigger sub but not minimarty size. I wanted better spl in 18-30hz range in my large room. My two micro-cubes are great for nearfield on either side of my couch and serve as end tables.

Lately I saw a couple people who wanted a sub in between cube and mini sizes. Looking at size chart there was a perfect spot in the middle. Thus the "JohnnySub" was born in honoring ltd02 as well.



Is 7.5 ~ cuft at 18.5hz tuning. Here is spl with si18 and 1100 watts



and here is regular cube (red), Johnny (blue) , minimarty (black) with si18 and 1100 watts.


For some minimarty is just too big. I just can't fit minimarty in my corner of livng room without it screaming look at me. I know some are looking for nearfield sub but mini too big as well. Can lay Johnnysub on its side as well.

32" height allows it to fit on a sheet of mdf perfectly. Here is cutlist .


Did I miss something? How big is the front?
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post #51 of 292 Old 09-06-2014, 04:20 PM - Thread Starter
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Did I miss something? How big is the front?
Look up ^
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post #52 of 292 Old 09-06-2014, 04:33 PM
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Look up ^
Is it on the cut list?
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post #53 of 292 Old 09-06-2014, 04:48 PM - Thread Starter
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Is it on the cut list?
Have to update it.
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post #54 of 292 Old 09-07-2014, 01:50 AM
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somehow i missed it too. maybe it was the moon phase. :-)

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post #55 of 292 Old 09-07-2014, 04:09 AM
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Quote:
Originally Posted by chalugadp View Post
Front baffle is 27.25" high by 24" wide.
Thanks, I just realized that I'll have to go with the Marty cube volume size instead. Please have a look at my thread, I got LTD02 to help me but it would be great to have the master builder on board too.


Marty sub? Sealed? Help please
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post #56 of 292 Old 09-07-2014, 06:54 AM
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Originally Posted by chalugadp View Post
Look up ^
Sorry, totally missed that you just replied to that question.
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post #57 of 292 Old 09-11-2014, 02:38 PM
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Quote:
Originally Posted by chalugadp View Post
Add two inches to port length and you will keep 18hz tuning .
I've changed my mind again thanks to LTD02, so I'm going to do two Johnnysubs. But I'm a little confused though about the tuning, LTD02 got a 19.5hz tuning in his measure and you Chalugadp is still on 18hz? Or am I missing something here? I have no idea how much that difference would be but it would be good to know which one is correct.
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post #58 of 292 Old 09-11-2014, 03:45 PM
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the port shown in post #38 will give about 19.5hz tuning. i just double checked it. that is with about 10% 'correction factor'.


if you want a little lower tune, the port can be made a little longer, but i would not go longer than 44" because of the effect on first port resonance getting too low. some have actually used very long ports without an apparent problems, so it is a little bit of a mystery that may depend on how many bends and the location of the bends in the particular design. more than 44" though and I'd have to say you are in 'experimental' zone, though you may still get a good result.


the only other option is to make the port a little less than the 2.5", but that will cause other problems, such as more audible chuffing. a 44" long 2.0" tall port will get it down to about 18hz, but that would require other modifications to the cut plan.


there are tradeoffs in these things and the designs that are presented are fairly well optimized, so trying to change one thing for the better will likely make another thing worse.

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post #59 of 292 Old 09-11-2014, 03:49 PM
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and i forgot to mention that hearing the difference in 1hz of tuning is...unlikely. :-)

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post #60 of 292 Old 09-11-2014, 07:06 PM
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The two subs that I built have two different 2.5" port lengths, and I don't see a huge difference in the port tuning - the first one was done with the port running all the way up the back panel and the other is done as described in this thread. I checked tuning using sine waves and didn't see any appreciable difference - both were somewhere around 19.5Hz as LTD02 estimated.

I still have an open question about how to boost below 20Hz with the iNuke and if I'm somehow making a mistake - I modeled a variety of PEQ settings in WinISD (varying the gain and Q factor) and tested with REW sweeps. I ended up liking the 6dB, 20Hz, 1.5Q boost, and it seems to keep the excursion within the 34mm limit even at 2200W. I tested a variety of permutations (different gain and Q values) and this variant produced a relatively smooth dropoff between 10-20Hz. Is this setting overly risky?



And here are some corresponding sweeps after playing around with equalization settings. The right sub (red trace) has the longer port and is directly facing a 8'x6' door opening that connects an adjacent room.

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