Maelstrom 21" With 4 - 2100 Gram 18" Passive Radiators

57873 Views 180 Replies 23 Participants Last post by Mike Cason, Jun 1, 2010

Mike Cason

Discussion Starter · Nov 21, 2009

Here is my build thread for the Maelstrom 21. I'll try to provide enough quality pics during my build for you.

I'm using Kevin's Maelstrom 21"er with the passive radiator design. I normally don't like building a passive radiator sub with a Qts over .4, but it is so close, I won't have a problem.

Here's the deal....23" x 23" x 60"; 13 cubes and 15.5 hz box tuning. With the typical passive radiator design there is more of a roll off but at this already low box tuning, I'll have more than plenty of bass. I needed the height to match my main speaker's height and get the cabinet volume I need. Better WAF here.

I just picked up the pallet of materials from my mill. My construction material is 1.25" mdf. It looked like I had ten bags of concrete in my truck going down the road. In the roll of plastic, I've got two sheets of Pionite black slate laminate to match all of my other speakers.

Cabinet resonance with this thick material; I don't think so. Moving it? Now that's another challenge.

Just got back from Houston with the materials so here is the first build pic:

Read more: So where are the Maelstrom-X 21" Build Threads! - Home Theater Systems - Electronics and Forum - HomeTheaterShack http://www.hometheatershack.com/for...elstrom-x-21-build-threads.html#ixzz0XWvNWnLo

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41 - 60 of 181 Posts

Mike P.

· #41 · Nov 29, 2009

with room gain should make this a very acceptable build.

Now there's the understatement of the year!

Mike Cason

Discussion Starter · #42 · Nov 29, 2009

Drizt said:
WOW, you have done extremely well.

Those subs are going to have more head room than anyone would ever realistically use. And thats a great thing

I'm only building one, "but the song still remains the same"!

Lonely Raven

· #43 · Nov 30, 2009

Looks good! Looking forward to seeing this all come together!

Mike Cason

Discussion Starter · #44 · Nov 30, 2009

Kevin Haskins said:
It looks small in that picture.

Kevin Haskins
Exodus Audio

Kevin,

It looks much bigger now. That's a 22" monitor up against it and the desk is 3' deep. I can't wait to hear this XBL2 21"er.... :foottap:

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Mike Cason

Discussion Starter · #45 · Nov 30, 2009

Lonely Raven said:
Looks good! Looking forward to seeing this all come together!

Raven,

I read you were finishing yours up a few days ago. What did you build and do you got a pic?

jreaves1637

· #46 · Nov 30, 2009

that thing is huge. Can't wait to hear your listening impressions once you get it finished.

Lonely Raven

· #47 · Nov 30, 2009

Mike Cason said:
Raven,

I read you were finishing yours up a few days ago. What did you build and do you got a pic?

My Maelstrom-X 21" Build Thread

I don't have "final" pictures of it yet. Once it's in place in the livingroom/theater, you really can't see anything interesting. I'll have to pull it out into the middle of the room, take a few photos, and push it back into place.

I'll probably be "finishing" it in truck bed liner, once I figure out what the most economical option is. I'd love to have a local shop spray it, but I can't find any that will take me seriously, or give me a good quote on it. They are too narrow minded to be open to spraying something that *isn't* a truck bed.

Plus measurements...I'm not even sure where my mixing board and Behringer mic is.

Your build makes me want to build a second one of these....or maybe an 18" LLT to compare side by side...but my budget wouldn't allow it. On the plus side, my fiance doesn't care what I put in the livingroom/theater, because she knows I have my own skewed, but decent sense of aesthetics.

Mike Cason

Discussion Starter · #48 · Nov 30, 2009

Thanks for the link. You did a nice job. Did you get down to 15 hZ?

Yea you're right....I noticed a lot of "this is what you should have done" comments. PMs work well instead of that kind of posting.

Be happy and enjoy the fruits of your labor. You've got real bass now!

Mike

Lonely Raven said:
My Maelstrom-X 21" Build Thread

I don't have "final" pictures of it yet. Once it's in place in the livingroom/theater, you really can't see anything interesting. I'll have to pull it out into the middle of the room, take a few photos, and push it back into place.

I'll probably be "finishing" it in truck bed liner, once I figure out what the most economical option is. I'd love to have a local shop spray it, but I can't find any that will take me seriously, or give me a good quote on it. They are too narrow minded to be open to spraying something that *isn't* a truck bed.

Plus measurements...I'm not even sure where my mixing board and Behringer mic is.

Your build makes me want to build a second one of these....or maybe an 18" LLT to compare side by side...but my budget wouldn't allow it. On the plus side, my fiance doesn't care what I put in the livingroom/theater, because she knows I have my own skewed, but decent sense of aesthetics.

Mike Cason

Discussion Starter · #49 · Nov 30, 2009

4

Hanging or gluing polyfill to the top and upper sides of a tall subwoofer cabinet would not ensure that it wouldn't be down in one of your drivers shortly after cranking it up. With my design, there's not much room to attach any raw poly to much surface area.

I decided to take my audio grill cloth and make a very tight and porous "basket" and fill it with the polyfil and seal it up so none could fall out.

I also installed some Sonic Barrier I had in stock and put in on the top and bottom of the cabinet to absorb any potential resonance and standing waves. I may just add some more loose polyfil when I'm done in the bottom just before I install the bottom two passive radiators, or I may leave it as it is and run my Linkwitz frequency CD on it and see where I'm at on my tuning frequency. I may have enough fill already with the "basket fill", plus the Sonic Barrier. It's easy to remove a passive radiator and add some if I think I will need more.

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Lonely Raven

· #50 · Dec 1, 2009

Crafty way of installing that poly fill! I just threw pillows and a line of acoustic blanket in mine! LOL

As for getting down to 15Hz...well, I'm not sure if my measurements are correct, but I just updated my post. I've got some repositioning to do, but it looks pretty solid down to 5Hz. :bigsmile:

Mike Cason

Discussion Starter · #51 · Dec 1, 2009

5 Hz? Whoooooo... I wonder what else I am going to break in my home? There has been a lot of stuff that has been destroyed in the past. You had mentioned wanting to get them coated in a "bedliner" material. I looked into a product called Hurculiner to treat my electrical truck I purchased and restored a couple of years ago, but I went with a commercial company to do the work. You can get a quart to try. If you like it, then a gallon some rollers should do the trick. Use a sample board. Most auto stores around here have it on the shelf. I didn't like it because it wouldn't hold it's shine in the weather. Well congrats on your project Raven!

Lonely Raven said:
Crafty way of installing that poly fill! I just threw pillows and a line of acoustic blanket in mine! LOL

As for getting down to 15Hz...well, I'm not sure if my measurements are correct, but I just updated my post. I've got some repositioning to do, but it looks pretty solid down to 5Hz. :bigsmile:

Lonely Raven

· #52 · Dec 1, 2009

I'm only a half-step ahead of you, and yours is much cooler! I'm looking forward to seeing how yours plays out.

Mike Cason

Discussion Starter · #53 · Dec 1, 2009

Lonely Raven said:
I'm only a half-step ahead of you, and yours is much cooler! I'm looking forward to seeing how yours plays out.

I've got many more steps to go with all of the laminate work and grills. I may ask the Shack's group to all come to my house to help carry it in when it's done!

I am preparing some Bang and Olufsen drivers and passives to be shipped out and I have a bunch of rectangular covered wool packs that they install in their Redline series speakers. I'll probably figure out a way to nicely install a few of them as wool is an excellent fill material and really enhances the speaker's musical quality. A lot of folks don't know that. I purchase pure Romney wool and install it in my Audience A3 builds.

Hey if your's sounds great....who's to say mine is cooler....we are let's just say equals in satisfaction! :sn:

Mike

Lonely Raven

· #54 · Dec 1, 2009

Mike Cason said:
Hey if your's sounds great....who's to say mine is cooler....we are let's just say equals in satisfaction! :sn:

Mike

My thoughts exactly...but with passives, I find your build technically cooler. The only two cool factors I have are #1, I'm the first 21" build, and #2, I built everything on prime numbers...even my bracing are spaced in primes. :nerd:

Pikefish

· #55 · Dec 2, 2009

Heh, primes. I build everything spaced to the Golden Ratio, and multiples thereof!

Very nice build, I'll be back every day now to see how it finishes.

Mike Cason

Discussion Starter · #56 · Dec 2, 2009

Well I'm ready to seal the coffin. I've decided I've got enough polyfil and the small amount of Sonic Barrier should handle any standing waves or distortion, so I'm sealing it up. Every hole is pre-drilled and ready for the glue and silicone.

I had a driver delivery I had to get to UPS and needed a puter battery to keep my system running, so here is where it's at tonight. After wire transferring funds to China for driver freight tomorrow, I'll get back on it and try to make some progress.

Hey fellows I've got the new F1200TS today and I've got some excellent reports for you and I haven't even used it yet. It is a masterpiece of it's own kind. I've got a lot of input from folks in the pro use and I'll post that info when I get some more time.

I appreciate the support! :T

Thanks
Mike

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Lonely Raven

· #57 · Dec 2, 2009 (Edited)

Pikefish said:
Heh, primes. I build everything spaced to the Golden Ratio, and multiples thereof!

Very nice build, I'll be back every day now to see how it finishes.

I couldn't figure out exactly how to implement the Golden Ratio in my box, though the primes bring it close. I was even going to go as far as doing the "seashell spiral" as my bracing, just for grins...but seeing as how I was on a time limit (built over vacation) and sick, I sorta tossed all the fancy stuff out the window and just went with primes.

Mike, quit teasing with wimpy photos, lets see some nice big build progress!! :wave:

Mike Cason

Discussion Starter · #58 · Dec 2, 2009

Lonely Raven said:
Mike, quit teasing with wimpy photos, lets see some nice big build progress!! :wave:

I've got two jobs and by my standards, am coming along fairly fast. I just picked up the raw materials 10 days ago and sold all of my other speakers and amplifiers and shipped them along with some driver orders. All the equipment is here, the back is now on and secured, and when I get back from the bank, I'll start on the bottom and the feet. I get my 18" 2100 gram passives tomorrow. Laminate should start to go on tomorrow if I don't have any service calls.

Lonely Raven

· #59 · Dec 3, 2009

I know! I'm just funnin' ya!

I should talk, I've been too tired and busy to get real measurements from my system, and still haven't hauled it out to the middle of the living room for more photos.

But I did veg in front of the big screen and finally watched Rambo IV on Blu-Ray. I actually clipped my EP2500 on the mortar fire scene! The impact was impressive! Hell, even TV with the 21" has more impact.

Mike Cason

Discussion Starter · #60 · Dec 3, 2009

Lonely Raven said:
I know! I'm just funnin' ya!

I should talk, I've been too tired and busy to get real measurements from my system, and still haven't hauled it out to the middle of the living room for more photos.

But I did veg in front of the big screen and finally watched Rambo IV on Blu-Ray. I actually clipped my EP2500 on the mortar fire scene! The impact was impressive! Hell, even TV with the 21" has more impact.

You should get more lows through your TV than a music concert if you have a good receiver putting out a good LFE signal to your sub because the movie directors add the THX and high impact scenes with extra lows and punch, like a war tank sitting next to you, or U571 with the depth charges. Watching a clip from the Haunting, you would think the sheetrock would come off the ceiling with my other two stacked subs it was so earth shaking!! :hsd: I can't even imagine what the Texas monster is going to do?

Off to get the passives at UPS and the laminate will be started today. There's lots of sanding and tweaking to get to this point. The additional birch bottom is installed too.

Did you really mean 5 hz? How did you measure that low of a frequency? Typo?

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