The Marty Sub Attacks!what folks are say'n"This sub is now playing loud & low! I am so impressed! ...I think that I will be ordering two more of these HO18's for use in 2 more Marty Subs, for a total of 4!"
-Martycool007"Yah, I,m lovin' having a capable sub in my system! I was shaking all sorts of things in my theater/office/storage room."
-mhutchins"...the 2 I have in my room are simply destructive beyond belief in the midbass..."
-wormraper"...now that i have had my marty sub broken in for a few days I can give my review. Lets start with WOW! ...bass is incredible. Chest thumping, pant ruffling, couch vibrating. Measured a couple of scenes and hit 115 db. Marty really puts my hsu vtf 15 to shame. It crushes it and is so effortless."
-chalugagp"First listening impression... be careful with the gain knob. Made my eyes cross with some EDM..."
-atredeis"I just finished installing the driver and, of course, I had to give it a quick listen (just a couple of familiar songs). One point: this thing is freakin scary!! ...when I run my Marty variant by itself, it is a pure monster- - plain and simple. It has a lot more output than my dual PSAs combined and that’s easy to measure, hear and feel."
-atabeawhat it is
originally conceived as a simple subwoofer that could be built using 2'x4' "handy panels" from home depot or some other store and would have huge performance using either the 18" dayton 460ho driver or the stereo integrity 18ht subwoofer.
the purpose of using "handy panels" is that they come in approximately 2x4 foot length, so the top, bottom, left and right side would require no cuts and many of the other panels would only require one or two cuts. handy panels also tend to be pretty well square, which will help keep the whole project squared up.
tuning is targeted at around 16-17hz. net enclosure size is about 11 cubic feet internal. external dimensions are approximately 2x2x4...feet
. :-)drivers that work
there are a surprisingly large number of drivers that work well in the marty sub, but the exact cutout dimension for the driver are slightly different for each driver. just a heads up.
- dayton rss460ho 18" (shown below)
- stereo integrity 18" ht (shown below)
- fi q 18": http://www.avsforum.com/t/1449579/4-18-fi-q-hts-project-spring-13#post_23753360
- ist/mach 5 audio uxl 18": http://www.avsforum.com/t/1489801/bought-four-sealed-18-cabinets-on-a-wild-hare-direct-me-to-a-driver-setup-at-least-competitive-or-superior-to-jtr-captivators/90#post_23756830
- ist/mach 5 18.2.2. 18": http://www.avsforum.com/t/1489541/large-ported-dayton-ho18s/600#post_23881394
- tc sounds lms ultra 18": http://www.avsforum.com/t/1489801/bought-four-sealed-18-cabinets-on-a-wild-hare-direct-me-to-a-driver-setup-at-least-competitive-or-superior-to-jtr-captivators/90#post_23756764
...will add more over time.
happy member chaluga with his driver for scaledrawings and architectural plan
member chalugadp put together a 3d drawing (nice work chalugadp!):
side view (with chalugadp's bracing strategy, other strategies are good too):
my drawings are no where near as slick :-)
inside (side view) (bracing not shown) (flush mount grill):
a couple of bracing concept designs:
mhutchin's bracing strategy as viewed from back and front (note the braces are cut just a hair short, this ensures that they will fit without having to perform exact measurements/cuts and simplifies the build).
front view with baffle added (and grill panel dry fit):
front view with top added:
for the grill, small blocks of wood could be placed in each corner and the grill would mount to them with magnets or something.
that way the driver would have plenty of room to move and would not have to be flush mounted or anything fancy.
in wood finish:
bare naked :-) (unfinished mdf):winsid model
here is the winisd model for 11 cubic feet, 17 hz tuning. green lines are the stereo integrity and dayton drivers. they have essentially the same performance. the blue line is for 3.5 cubic foot sealed subwoofer. all are at 1100 watts of power.
so why build a big ported sub? as can be seen, with the same driver and the same power, the larger ported cab produces around 10db more spl than its little brother in the lowest notes. doubling up a small sealed and doubling power into it will provide +6db, so it still won't quite be as powerful as the ported around the tuning frequency.
...since it needs a name...it shall be known as The Marty Sub!
forum member mhutchins provided an excellent detailed write-up of how he constructed his Marty Sub!
thanks mike!additional tips
gluing panels and securing with braces while glue dries is ideal.
without braces, gluing and securing with brad nails or spax screws (which are designed to not split wood) is an alternative method. predrilling holes for screws will further reduce any risk of panel buldgeout and/or splitting.
wood glue is fine if the panels mate with no gaps. if there are gaps between the panels, pl premium can be used an an alternative adhesive. it expands as it dries to fill in gaps, but is more of a mess to work with.
this is a spax screw that was used with success by member wormraper. this is NOT for securing the driver. this is for joining the panels.
video instruction on how to wire a speakon connection if going that route:
if you need an "extra hand" while gluing the boards together, corner cleats can really help keep things lined up. just pre-drill and don't use overly large screws or you could blow out the wood.
mhutchins did a nice write up with pictures on his grills:
chaluga did a nice job finishing in cedar plank with black piping:
atredeis' helper offered encouragement during his build:
hopefully a couple folks will double check those dimensions. it assumes 3/4" wood is used, which might be right for MDF, but plywood may require slight measurement modifications depending on how many sixteenths they cheat. :-)
this sub is approximately 12 cubic feet prior to bracing and driver or roughly 11 cubic feet net.
the port will appear too short if modeled in winisd using k=0.732 for end correction. this is discussed in detail on the third page of this thread.
home depot and several other home stores have a saw like this and will make cuts for $0.50 or sometimes just do it for free. that makes things easy for a project like this! is it "kit simple"? no. but getting close. :-)edit:
this page is revised based on new information from this thread with the primary changes being a modified port and note that mdf handy panels are not exactly 24" x 48" since they may be cut from 49" x 97" mdf.edit: more
when i originally threw together the martysub v0.1, we didn't know how significant a difference there is between actual tuning and theoretical tuning using winisd's calculator for port length. i designed the port height to be such that the port length would be in the ballyard of 3 feet long in order to keep the first port resonance out of the pass band.
it was pointed out by member nograveconcern that there is a calculator that considers this difference: http://www.carstereo.com/help/Articles.cfm?id=31
there is also a study of various ports and tuning frequencies for stuffed and unstuffed enclosures, here: http://www.troelsgravesen.dk/vent_tuning.htm
now, in light of the new information, i'd suggest changing the port height to 3.0" and going with a length of 36.0" for a "best guess" tuning of 17hz.
that is based on a multiplier "in my head" that i can't explain based on intuition from looking at all this information. it also happens to be consistent with the "best guess" in the calculator linked to at carstereo.com
the increase in port height will reduce port velocity by a hair and will not take much volume out of the sub overall.so the new plan for the slot port, subject as always to revisions and updates, is 21.0" wide X 3.0" tall X 36.0" long.
that targets a tuning of 17hz in a cabinet with a net volume of 11 cubic feet (a martysub).
member chaluga measured his marty which has a 2.75" tall slot port, 21" wide (effective) and 36" long, with light stuffing in the enclosure and gets 16hz, so this confirms 21.0" wide X 3.0" tall X 36.0" long will give about 17hz and 21.0" wide X 3.0" tall X 32
.0" long will give about 18hz.
this works out to about a 25% reduction in slot port length vs. what winisd suggests. in other words, using the winisd length results in a port that is tuned too low. the port must be made shorter than what is shown in winisd to hit the target tune.
the addition of lots of bracing may bring the net enclosure volume down a bit, which pushes tuning back up a little high. that is no problem because the addition of stuffing can be used to bring the tuning frequency back down some.edit: even more
ok, thanks to worm, we really went deep into understanding why winisd miscalculates actual vs. theoretical enclosure tuning.
several people have observed this error between theory and actual results and one great post is here:
ports behave differently depending on how they are mated to the air at the end of the port. this is called "end correction" and is quantified by a mysterious variable called "k".
for ports that dump cleanly into free space, end correction is low, something like k=0.732 on a baffle and even a little lower if the port has no baffle.
for slot ports that are on the ground, the boundary in front of the port and behind the port have the effect of synthetically extending the length of the port.
as a result, these kinds of ports provide a lower tuning frequency than winisd estimates using k=0.732
this picture shows how end correction should increase as one moves more toward a slot type port:
i do not speak german (if that is even the language used here), but i interpret it to be indicating whether there is 1, 2, or 3 boundaries reinforcing the port either in front of or behind the port.
there is also some averaging that occurs, so if it is k=1.5 to the front of the port and k=1.0 to the rear of the port, the average would be k=1.25.
here is the link to the calculator:
for k=0.732, the calculator gives the same results as winisd. however, the version of winisd that i have for windows 7 does not allow changing of the end correction to other value, hence the use of the calculator.edit: even more
the original design intention was to make this as simple as possible, but as things go, it got more complicated. i decided to go back and redo it again from the ground up with the intention of a person being able to go to a home depot or other home store, grab some handy panels, have them trimmed down and come home with all the wood required for a marty sub.
the primary challenge is that the handy panels come in a nominal 24" x 48" size, which for plywood is about right, but since a full sheet of mdf is typically one inch larger to allow for the ends to get beat up, the handy panels that are called 24" x 48" are really a little larger. that is fine. so with that in mind, here goes...Introducing...The Marty Sub "One Cut" Version!
this version has all the performance of the original marty sub (same frequency response, same tuning frequency ~17hz, etc.), but with the added advantage that it requires **only** cross cuts to handy panels. by examining the cut sheet, the advantage of this approach will quickly be seen.
this version sits a little lower and is therefore a little "fatter" than the original marty sub, but this is so that all the internals can be the same panel width as the top and the bottom, even all the braces. since the width of the handy panels can be confirmed at the store before purchase, this makes this version virtually foolproof (at least with respect to cutting the panels).
front view in duratex:
front view grill off:
at first it appears complicated, but it was designed to be easy to construct and doesn't require any further cutting of any of the braces.
a total of 8 handy panels 24" x 48" nominal OR two full sheets of mdf or plywood.
four handy panels that are not cut down.
four handy panels that are cut down thusly:
the cutout for the driver will vary depending on the driver selected.
it is 16.7" diameter for the dayton driver for example.
if all that makes your head want to explode...
it's not that bad. really, it's not. :-)
.Edited by LTD02 - 12/22/13 at 2:27pm