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Discussion Starter · #1 ·
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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Discussion Starter · #4 ·
re: Maelstrom 21" With 4 - 2100 Gram 18" Passive Radiators

Mike, it's nice to be the first with a successful build. I usually don't copy others because I don't feel that it was my build and that takes away a little from the fun of it all. :D

As far as being heavy, it's going to be like building a tilt wall concrete building and then moving it! With a subwoofer driver like the Maelstrom 21 and all of the passives working together, I want a solid cabinet which will be resonant free. It is going to be tough to work with during the build. My two stacked subs in my avatar weight 235 lbs. ea.
 

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

This is about what you can expect with that enclosure Mike. I stuck a 13Hz subsonic filter on this, figured 20% fill and used 2000W with this simulation. I used my PR-15"s because I was too lazy to load the exact parameters for John's PRs but they should be roughly the same.

Even with 2000W (EP-2500 type amp) you have plenty of safety margin. The PRs are < 40mm P-P so they should be alright using six of them. I wouldn't worry about the main driver excursion @ 10Hz, simply because there isn't much down there and the rest of your system probably has DC blocking filters cascaded, which attenuate down there anyway. Depending on your room, I'd say you have very respectable output @ 15Hz and above. :T



Kevin Haskins
Exodus Audio
 

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

125dbSPL @ 20Hz? :unbelievable:
 

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

Look forward to the build. When ever someone breaks out a pair dial calipers to measure MDF must have some precision in mind:demon:
 

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Discussion Starter · #8 ·
Thanks for the very nice graph and modeling work Kevin! I've only got the QSC 1450 amps I've been using for my current subs, so it looks like I'll be upgrading the amp as well. I don't like the term clipping, and with the 1500 watt rating of the Maelstrom, my 1450s briged will only put out 1400 watts; 4 ohms at 1khz. Bring the sub output level down to the high teens or low twenties, and the amp's output will probably be down around 900 to 1000 watts maxed out and will probably clip.

John's 18" flat mdf passives I think have an fs of 3.9 at 2100 grams. 3" P-P on cone travel.

I appreciate your excellent communications, the phone call, and your service beyond what is expected out of a dealer.

VBR
Mike

This is about what you can expect with that enclosure Mike. I stuck a 13Hz subsonic filter on this, figured 20% fill and used 2000W with this simulation. I used my PR-15"s because I was too lazy to load the exact parameters for John's PRs but they should be roughly the same.

Even with 2000W (EP-2500 type amp) you have plenty of safety margin. The PRs are < 40mm P-P so they should be alright using six of them. I wouldn't worry about the main driver excursion @ 10Hz, simply because there isn't much down there and the rest of your system probably has DC blocking filters cascaded, which attenuate down there anyway. Depending on your room, I'd say you have very respectable output @ 15Hz and above. :T



Kevin Haskins
Exodus Audio
 

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

Thanks for the very nice graph and modeling work Kevin! I've only got the QSC 1450 amps I've been using for my current subs, so it looks like I'll be upgrading the amp as well. I don't like the term clipping, and with the 1500 rating of the Maelstrom, my 1450s briged will only put out 1400 watts; 4 ohms at 1khz. Bring the sub output level down to the high teens or low twenties, and the amp's output will probably be down around 900 to 1000 watts maxed out and will probably clip.

I appreciate your excellent communications, the phone call, and your service beyond what is expected out of a dealer.

VBR
Mike
Hey... no problem. I love getting people pointed in the right direction. You can use as much power as you can afford on this driver. I have several people using 3000-5000W worth of amplifier (ratings) and there is not an issue with using "too much" power. They eat it up.... and what you get out of the wall usually limits what you put into the driver anyway.

Kevin Haskins
Exodus Audio
 

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Discussion Starter · #10 ·
Re: Maelstrom 21" Beginning build pics....

My wife got home and thought I was building a coffin to save money. I had to remind her that mdf wouldn't last very long buried.....

Well, here are the first pics.....many more to come. :blink:

I'm really not sure how I am going to be able to work with this heavy of a cabinet during construction, but that's never stopped me before. This material is so thick I used 2.5" decking screws and filled up the holes. They will be sanded and I will laminate the entire cabinet. This is just too heavy for a glue up construction project and there will be a lot of internal pressure. I did use generous amounts of glue too. :nerd:
 

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Discussion Starter · #15 ·
re: Maelstrom 21" With 4 - 2100 Gram 18" Passive Radiators

Mike, you are so keen I had to go out and measure. We're spot on 23" square! I'll pick up my HD binding post and the Maelstrom-21 which are in today just waiting for my anxious hands to pick up.

Thanks guys! It is very solid and heavy, and I haven't even put in the braces. I'll turn it over today to work on them.

It looks higher than it is wide. Did you change the original 23" x 23" x 60"?
 

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Discussion Starter · #17 ·
Yea, that's the ticket....

It looks like after the internal bracing and driver displacement, I'll still have 13 cu. ft.

This cabinet is going be better, and the 2100 gram 18" passives are going to sweeten the numbers.

Off to the doc's office and then I'll pick up the beast. :sn:

Thanks... :innocent:

It must be the resolution on my monitor that's making it look taller.
 

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Discussion Starter · #18 ·
Re:The Monstor Maelstrom 21" has arrived!

I wanted to keep the cabinet as small as possible at 23" squared. It's going to be a bit of a challenge to build a nice grill for this gigantic beast. I was also trying to save on the lamanite. At 23", I only need two sheets. At 24" or more squared, I would need four sheets.

Look at the size of this thing! It really should be illegal! Yep, I'm going to need a much bigger amp for sure. The build quality is incredible with what I can see.

I got some huge terminals that will accept #4 wire or bananna plugs.

More paper work to do and then back in the shop again.
 

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