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Large Ported Dayton HO18's - Page 8

post #211 of 999
Ahhhhh if you a
Have any voids just fill in with pl caulk or wood filler
post #212 of 999
Thanks, Worm.

I did notice a void that goes from the cutout to the outer edge, however, it will seal when I mount the front baffles with PL. I may seal the void at both ends to minimize the risk of a leak at the screw hole.

I got both front baffles cut out and the speaker baffle was recessed 7/16" which gives a nice flush finish for this monster woofer. I still need to rout the 2nd baffle, and I will measure that one again because I want the inner lip to extend just a bit beyond the lip of the front baffle. Even with 2 plywood baffles, I think I will still add a 3rd layer of ply just behind the screws only, for extra purchase. I'm thinking a #10 x 2" drywall type screw would work well. The #8 x 1" screws that I bought from PE for the Cheap Thrills are a little short and the pan head is barely larger than the 1/4" screw hole in the woofer flange.

Progress has slowed this week, but I should get close to closing out the enclosure this weekend. #fingerscrossed

Mike
post #213 of 999
This thread has me stoked to build a Marty !
post #214 of 999
^^ bravo!
post #215 of 999
I ordered the SI sub and will begin building the marty sub. Just a few questions ... I have built dozens of woodwork projects but never a sub box. I am going to use baltic birch ply with a watco danish oil finish mixed with urethane. I will add on to the marty box a skirting and top made of oak. Construction questions,

1) Due to high pressure sound waves I am not sure where to use brad nails vs screws. I teach woodwork in a school that has all the tools. Other then holding the sub in place do I need
to use screws anywhere else on the sub ?

2) What do I use to seal all the joints on the inside ? Caulking adhesive ?

3) Do I buy the speaker terminals from parts express and which ones ?

4) Do I get the gasket tape from HD and which brand ?

I also teach sketchup and today I am going to create a fully rendered version of my project and then post it here.. If you have sketchup questions I am the guy to ask. Once I start building I will take pics and post as well. Can't wait to hear feedback from other people who are building this beast in terms of SQ.smile.gif
smile.gifsmile.gifsmile.gif
post #216 of 999
should be one good looking marty sub!

"1) Due to high pressure sound waves I am not sure where to use brad nails vs screws. I teach woodwork in a school that has all the tools. Other then holding the sub in place do I need to use screws anywhere else on the sub ?"

if the joints are a good fit, wood glue the way to go. if the joints are not a very good fit, pl premium expanding adhesive. brads and screws can make assembly easier so not so many clamps will be required, but otherwise no screws or nails are required.

" 2) What do I use to seal all the joints on the inside ? Caulking adhesive ?"

same as above.

" 3) Do I buy the speaker terminals from parts express and which ones ?"

that depends how you wish to connect it to the amp. the pro amp will have speakon connectors, so that is one option which was shown: http://www.avsforum.com/t/1489541/large-ported-dayton-ho18s/210#post_23749615

here is a picture of how they connect to the wire. we'll have to check your amp to see which "pins" are the right ones, but just to give you an idea of how they work:
http://www.advancemcs.com/FAQs/speakon.html

for gasket, brand doesn't matter. this is generally what you are looking for:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-540
post #217 of 999
I finished my Marty sub sketchup . I will hold off starting construction until the port tuning frequency is flushed out. I am looking to hit 16-17hz. I left the grill cover open to see the sub. The orange blocks are the spacers.biggrin.gif:D









I updated to include latest port change .
Edited by chalugadp - 9/20/13 at 4:11pm
post #218 of 999
AWESOME!
post #219 of 999
oh yeah, how much we wanna stuff these suckers? a few inches just along the walls or something? or do we wanna stuff the crap out of them like a sealed box?
post #220 of 999
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).

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.

i will update threads and pictures to minimize confusion for first time builders/readers.
post #221 of 999
What about the 28 inch long long by 2.5 inch high slot we've been working with?
post #222 of 999
Quote:
Originally Posted by wormraper View Post

oh yeah, how much we wanna stuff these suckers? a few inches just along the walls or something? or do we wanna stuff the crap out of them like a sealed box?

I could use a picture to show amount of stuffing needed.smile.gif
post #223 of 999
"What about the 28 inch long long by 2.5 inch high slot we've been working with?"

i changed it to 36" inches long and 3" tall. :-)

the larger port reduces enclosure volume by a hair which makes the port a little longer and going to a 3" port further increases the required length.

i think that it will work about the same as the 28" x 2.5" that we've been working with. it will just have slightly more air flow, that's all.

as for stuffing, that depends on how the tuning comes out. if it is a little high on the tuning, add more stuffing. if tuning is dead on nutz, go light.







.
Edited by LTD02 - 9/20/13 at 4:59pm
post #224 of 999
Quote:
Originally Posted by LTD02 View Post

What about the 28 inch long long by 2.5 inch high slot we've been working with?

i changed it to 36" inches long and 3" tall. :-)

the larger port reduces enclosure volume by a hair which makes the port a little longer.

as for stuffing, that depends on how the tuning comes out. if it is a little high on the tuning, add more stuffing. if tuning is dead on nutz, go light.

oh yeah, that I caught. I was just asking how much we'd be screwed in port velocity being that we went with a bit smaller of a port height and length...


gotcha.. quick question. HOW do we test for port tuning? I've never done something like that before.


and I always thought EVERY sub needed to be stuffed in order to reduce "boominess" for lack of a better word due to reflecting off of the bare walls
Edited by wormraper - 9/20/13 at 5:02pm
post #225 of 999
big update to the original plan: http://www.avsforum.com/t/1489541/large-ported-dayton-ho18s#post_23711347

appreciate your thoughts on how we might improve it! some pics may be familiar chalugadp (i just put a different top on). :-)

i tried to pull some of the information together so that other folks could hit one post and have some idea what the heck was going on. :-)

"oh yeah, that I caught. I was just asking how much we'd be screwed in port velocity being that we went with a bit smaller of a port height and length..."

i don't think screwed is the right way to put it. the 2.5" should be good. i'd say the 3" just provides a little more margin of error or performance at the very limits.

"quick question. HOW do we test for port tuning?"

the simplest is with test tones. get the driver moving with some power, reduce the frequency until the cone excursion is minimal. that is the tuning frequency. both above and below the tuning frequency excursion will go up.

another approach is to measure the impedance. the bottom of the saddle in between the two resonance peaks is the tuning.

a third approach is to measure the current as a function of frequency. for any given volume setting (i.e. constant voltage), current will be maximized when impedance is minimized. hook a meter to the terminals, run test tones, measure current. the frequency with the most current is the tuning frequency.
post #226 of 999
ok gotcah, just was slightly worried that our original design that we are building right now would screw us by accidental calculations (of course this comes up AFTER I've already glued in the slot ports biggrin.gif)....


ahhh, that's pretty easy. I'll get me a set of test tones to run through when I'm done.got a volt meter too so that should be easy enough with the current....I assume you mean DC voltage?
Edited by wormraper - 9/20/13 at 5:27pm
post #227 of 999
Went back and checked out the updated post 18 and damn its impressive .
post #228 of 999
thanks chaluga. i hope that it inspires many folks to build a marty sub!

i'm kind of thinking that a "cut list" that one could take to home depot might make a ton of sense. i don't know why we don't see that being done more frequently. at 50 cents a cut or whatever they charge these days, it would seem to make a lot of sense.
post #229 of 999
"I assume you mean DC voltage?"

for a given sound level, the amp outputs a constant voltage. the current is what will be varying and what you will be measuring.
post #230 of 999
Ahhh sorry I misunderstood. How exactly would u test the current (electricity was never my strong point)
post #231 of 999
post #232 of 999
Quote:
Originally Posted by chalugadp View Post

I finished my Marty sub sketchup ..

Wow, Chalugadp. I really like your sketchup model. I have a few thoughts about the bracing I thought I would share, partly because I felt a need to explain the pseudo-engineering concepts I was using for my bracing.

1. Deeper braces are better than shallow braces for making panels stiffer. Bracing stiffness increases as a function of depth squared (^2), eg. doubling the brace depth from 1" to 2" results in a brace 4 times as stiff.

2. If the Slot Panel has lengthwise braces on one side, minimal stiffness is added by additional lengthwise braces on the opposite side. Cross braces on one side and lengthwise braces on the other side will behave the same as if the braces were both on the same side. That is why the top of my Slot Panel only has cross braces, because I felt additional lengthwise braces would be redundant. Granted, they are not as deep, and therefore not as stiff as the added lengthwise bracing, but I felt the added complexity could be avoided with minimal impact on structural stiffness, especially since the shorter slot braces are supported by a panel on BOTH sides.

3. Regular wood is stiffer than MDF, but is also more likely to resonate. I felt that the relatively short pieces of natural wood would offer superior strength to weight ratios vs. MDF and yet would still be sufficiently stiff as to not resonate within the operating range of the sub. I have no proof for this last assertion.

4. Large area lap joints are easy to construct and offer superior bond strength compared to but joints, even if biscuits are used. Furthermore, I built the lap joints with one piece intentionally short to minimize the number of precision cuts required and potential rework if the length was too short or too long. I really like the look of many of the window braces I see in the build threads, but I think many of them fall short in terms of either the lack of stiffness they add to the design or the added weight without substantially increased strength. Lastly, some of those window braces are very complex and look like they require a lot of time and precision for a good fit.

Given the above, I would suggest the following changes to your design:
1.Extend the Slot Braces all the way to the back panel. You can make them taller beyond the inner port opening if you wish.
2. Eliminate the redundant longitudinal Slot braces on top of the Slot Panel and add cross braces instead.
3. Add full cross braces to the rear panel. There is no need for the bracing here to resemble the front panel, because you don't have to worry about clearance around the driver.
4. I like the double bracing that you have drawn, and it may be necessary, I don't know, but it will definitely make the building that much more challenging and time consuming.

Please don't take these suggestions as being too critical. I really like your design, overall, but from my limited experience, the bracing looks like it will be a tough build. Now, if you figure a clever way to build the bracing on the bench and place the majority of it into the sub already assembled, you will really be on to something!!

Awesome skethchup model! You are definitely THE SKETCHUP MAN!

Best regards,
Mike
post #233 of 999
"Given the above, I would suggest the following changes to your design:
1.Extend the Slot Braces all the way to the back panel. You can make them taller beyond the inner port opening if you wish.
2. Eliminate the redundant longitudinal Slot braces on top of the Slot Panel and add cross braces instead.
3. Add full cross braces to the rear panel. There is no need for the bracing here to resemble the front panel, because you don't have to worry about clearance around the driver.
4. I like the double bracing that you have drawn, and it may be necessary, I don't know, but it will definitely make the building that much more challenging and time consuming."

all worth considering. running the slot bracing all the way to the rear panel was something that i had in the original plan, but then took out to try to keep the number of precision cuts to a minimum, but then put back in again because it make a lot of sense. revised and updated drawing in post #18.

the 10,000 foot picture is that subwoofer panels are weakest in their centers and strongest toward their edges, so if the point is to keep the panels from vibrating having bracing closer to the centers of the panels would be well advised.
post #234 of 999
Quote:
Originally Posted by mhutchins View Post

Wow, Chalugadp. I really like your sketchup model. I have a few thoughts about the bracing I thought I would share, partly because I felt a need to explain the pseudo-engineering concepts I was using for my bracing.

1. Deeper braces are better than shallow braces for making panels stiffer. Bracing stiffness increases as a function of depth squared (^2), eg. doubling the brace depth from 1" to 2" results in a brace 4 times as stiff.

2. If the Slot Panel has lengthwise braces on one side, minimal stiffness is added by additional lengthwise braces on the opposite side. Cross braces on one side and lengthwise braces on the other side will behave the same as if the braces were both on the same side. That is why the top of my Slot Panel only has cross braces, because I felt additional lengthwise braces would be redundant. Granted, they are not as deep, and therefore not as stiff as the added lengthwise bracing, but I felt the added complexity could be avoided with minimal impact on structural stiffness, especially since the shorter slot braces are supported by a panel on BOTH sides.

3. Regular wood is stiffer than MDF, but is also more likely to resonate. I felt that the relatively short pieces of natural wood would offer superior strength to weight ratios vs. MDF and yet would still be sufficiently stiff as to not resonate within the operating range of the sub. I have no proof for this last assertion.

4. Large area lap joints are easy to construct and offer superior bond strength compared to but joints, even if biscuits are used. Furthermore, I built the lap joints with one piece intentionally short to minimize the number of precision cuts required and potential rework if the length was too short or too long. I really like the look of many of the window braces I see in the build threads, but I think many of them fall short in terms of either the lack of stiffness they add to the design or the added weight without substantially increased strength. Lastly, some of those window braces are very complex and look like they require a lot of time and precision for a good fit.

Given the above, I would suggest the following changes to your design:
1.Extend the Slot Braces all the way to the back panel. You can make them taller beyond the inner port opening if you wish.
2. Eliminate the redundant longitudinal Slot braces on top of the Slot Panel and add cross braces instead.
3. Add full cross braces to the rear panel. There is no need for the bracing here to resemble the front panel, because you don't have to worry about clearance around the driver.
4. I like the double bracing that you have drawn, and it may be necessary, I don't know, but it will definitely make the building that much more challenging and time consuming.

Please don't take these suggestions as being too critical. I really like your design, overall, but from my limited experience, the bracing looks like it will be a tough build. Now, if you figure a clever way to build the bracing on the bench and place the majority of it into the sub already assembled, you will really be on to something!!

Awesome skethchup model! You are definitely THE SKETCHUP MAN!

Best regards,
Mike

No worries about constructive feedback . Will my bracing have a negative effect on sound due to resonance ? If so I will definitely change it. As for difficulty in build that's where jigs come into play. I made all the bracing similar so I could make a jig . I was going to screw the bracing together with cordless and inch and a half screws. Was going to attach bracing to box with angle brackets. If I do it this way I could assemble bracing and attach to box in a couple of hours . Been woodworking for 25 years and my shop has every tool you can think of so I am very fast . However if the screws inside the box will effect the sound then back to the drawing board for me.

If the screws don't effect the sound I will post a sketchup drawing of the jig I will make.

Thanks for the compliments on sketchup. If anyone needs help with that let me know. I have made 40 instructional videos and over a dozen handouts .
post #235 of 999
I don't believe screws will have any negative impact on panel resonance, nor do I think the added bracing will have any adverse effects on sound or panel resonance. To the contrary, it should be less resonant, because as LTD mentions, you have smaller unsupported panel areas with the extra bracing shown.

With regards to the angle bracket attachments, I would recommend a solid glued interface between all the bracing edges and the MDF panels so that everything is one solid unit. It sounds like you already know all this stuff, but I just wanted to make sure. wink.gif

Mike

ps, thanks for the sketchup tutorials!! I made it through just the 2nd one and I am already learning new methods. They rock!
post #236 of 999
I will make the jig in sketchup tomorrow if I can. In sketchup remember that the most important thing is to make objects groups and components. Second there is a tonne of great plugins that make it a lot easier . Get the plugin store and then download these : curviloft , rounding corners , fredo scale and fredo tools. I used twilight renderer to render it with lighting and materials .

My bracing would be tough if you didn't have tablesaw with biesmeyer fence (best fence for tablesaw ) 20 clamps with clamping table , bostich brad nailer with compressor , biscuit joiner , Bosch chopsaw and router. Your design makes a lot more sense with limited tools.

I just feel like an idiot for not getting into diy earlier .
Edited by chalugadp - 9/20/13 at 11:22pm
post #237 of 999
i made substantial updates to post 18 including a complete (well kind of) redesign that requires only cross cuts on handy panels!
post #238 of 999
First tuning report for MartySub Variant with port dimensions of" 2" x 7" x 36" x 3 ports

14-15 Hz with a bare box interior - 15.9 Hz predicted by WinISD.

I just watched the cone excursion as it abruptly decreased from 10 Hz, seemed to hit a definite minima at either 14 or 15 Hz and then began to gradually increase again.

Using WinISD 0.7, I modeled box volumes 11 Ft^3 and 12 Ft^3 with the same port dimensions as above +/- .04" on the length and got Tuning Frequencies of 16.2 and 15.5 Hz, respectively. Using my calculated volume, WinISD predicts a 15.9 Hz tune. I have a 2" PVC section mounted to the interior end of the slot port serving as a flare. For now, the exterior ends of the port are blunt, without round-overs or flares. Edit - No noticeable difference in tune with exterior round-overs on port exits.

That's enough fun for now, back to work to get this bad boy finished!

Mike biggrin.gif
Edited by mhutchins - 9/21/13 at 5:13pm
post #239 of 999
Ok I made a little sketchup mockup of how I would do the bracing. This would only be fast if you had access to a tablesaw, brad nailer, and jigsaw/bandsaw. I will put my estimated time in brackets, however, there always seems to be one stage where you get slowed down.

1) First rip several pieces of pine or other softwood that accepts screws easily to 3". Then chopsaw pieces to desired length. (15 min)

2) Need to make three square frames for the inside. Since I already have a jig in my shop to cut perfect 45 degree angles I will use it to cut pieces in picture frame manner ( 10mins)



3) Next lay four pieces together and pull tight with band clamp to hold in place. Nail as shown below and take clamp off. Glue is inside. (15 min)



4) Next make jig to cover corners (brown piece in sketchup) , give strength to joint and its a guide as to where to put vertical pieces. I would cut these 1/4" pieces out of plywood stacked on top of each other . Nail down with glue (20 min)



5) Pin nail vertical pieces in place just to get in right spot before screwing down. (10 min)



6) Screw vertical pieces in place with cordless drill. (20min)



My time estimates were for all three. Somewhere from 1.5 to 2 hours in time. Would assemble marty box bottom, sides, top and port , then slide in these braces, glue, connect speaker connections( before I put top on), and then finish. Put in subwoofer after and Bob's your uncle. TIme for whole thing 3-4 hours plus finishing. Normally when I do a project that requires assembly of large panels I invite a buddy to help, provide some brewskies, and it speeds things up if you have the right guy. I am aware there are many ways you could do this. I have made many cabinets before (worked in Kitchen Cabinet shop for two years before starting teaching) and am aware that things are much easier when you have the right tools. Using Ltd's method would be easier for those who don't have access to many tools. My enclosure I would feel confident standing on top of ( I think I will in my build and take a pic) before I add on the oak tabletop. Now off to watch some Football wink.gifwink.gifwink.gif
post #240 of 999
Quote:
Originally Posted by mhutchins View Post

First tuning report for MartySub Variant with port dimensions of" 2" x 7" x 36" x 3 ports

14-15 Hz with a bare box interior - 15.9 Hz pedicted by WinISD.

I just watched the cone excursion as it abruptly decreased from 10 Hz, seemed to hit a definite minima at either 14 or 15 Hz and then began to gradually increase again.

Using WinISD 0.7, I modeled box volumes 11 Ft^3 and 12 Ft^3 with the same port dimensions as above +/- .04" on the length and got Tuning Frequencies of 16.2 and 15.5 Hz, respectively. Using my calculated volume, WinISD predicts a 15.9 Hz tune. I have a 2" PVC section mounted to the interior end of the slot port serving as a flare. For now, the exterior ends of the port are blunt, without roundovers or flares.

That's enough fun for now, back to work to get this bad boy finished!

Mike biggrin.gif

Take some pics of finished box. 16hz pounding out at plus 100db would be awesome. Going to get my lumber next week. Please give listening impressions with movies rumbling your foundation ! biggrin.gif
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