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Discussion Starter #1 (Edited)
First I would Like to thank Kevin H for All his help and advice with this build and also Stuart of Audio Market place.au for helping making this DIY SUB Build possible....

I Decided to build 2 x Maelstrom-x + 2x PR18 Subs in 8.6cf/244lt Box's For my home Theatre...

I chose to build the boxes out of 32mm MDF with Double Baffels for the Active driver's mainly because
I love working with MDF second because being 32mm thick I could get away with less bracing...

After talking to Kevin for his advice, My plans were to go with 1800g mass on each passive (max recommended weight) 124 oz of polyfill and Drive the Subs with the largest power amp Peavey make, Peavey CS 4080 power amp rated at 2040W RMS @4ohms Per channel or 4080W RMS Bridged @4ohms.... Running off A Dedicated 240Vac line...

That way I could feed each sub over 2040W RMS @4ohm off each Channel of my Peavey 4080 Amp.
For the EQ and Highpass filter (subsonic) to protect the Mael-X's I went with the feature Rich Behringer UltraDrive Pro DCX 2496,3 inputs & 6 outputs, the benefit of this is that I can feed the power amp A balanced input signal thus get more gain, second I have the flexability later on to run my 2x 12" NHT sw3 seald subs as mid bass IE: 2x 12"subs 100hz-60hz, 2x 18"subs 60hz down...


.................THE BUILDING PROCESS............

After I cut out all the pieces of MDF and marked out all the screw holes, I dry fited the 4 sides clamped and then PRE drilled the holes for the screws
then used A counter sink bit and screwed all the screws in but did'nt do them up tight at this stage...then I disasembeled the sides glued both sufaces liberaly and fited clamped then screwed the screws up tight... Repeating the process for all 4 sides....

One of The resons you need to Dry fit and pre drill the screw holes is because if you were to glue then drill the holes the glue and saw dust caused from the drilling process sticks to the drill bit and reams, makes the hole larger id thus A loose fitting screw.....
I screwed and glued (MDF glue) the boxes, building the 4 sides first giving them 2 days to dry then added the top bottom and outer baffels last...
When constructing the box I made sure that I allowed my measurements to be A little bigger than was required so I could then use my 2300w 1/2 Makita router (scary tool) with A Carb.I.Tool 1/2" 50mm cut, double bearing flush trim bit to flush trim the subs for A perfict finnish....

For A good result you "Must use High Quality Router Bits if you are After A perfict finnish", Sorry But The "ROUTER BITS" you get with "CHEAP ROUTERS DO NOT CUT THE MUSTARD" The main problem is the uneven cuting action of the cheap router bits aspecialy when cutting out the Baffel Holes for the Drivers... And they can put more strain on the routers armature in turn dramaticly shortening its life...

For cutting the inner and outer baffels I made up my own jig from 7mm ply that I then fitted to the bottom of my little 1/4" lamanate trimmer (small router) and fitted the other end of the jig to the exact center of the hole using A little nail.... it took me roughly 6 times around (x2 so the cut out is 20mm wide) to route through the 32mm MDF "BUT" the trick is not to route out all the circle keeping at least 2 opposed sides 5-7mm thick left and around 3" long... Next I flip the Baffel over and used A CarB.I.Tool 30mm cut 1/4" flush trim router bit to finnish cutting out the circle....

When it Came to the mounting holes in the baffels I sat the Drivers in place then after carefully marking out all the driver & passives holes I used my bench drill so as to get perfictly stright holes for the top and bottom holes I used A 6mm drill bit and for the others I used A 5.5mm...

To mount the active Driver I used high tensile Hex head bolts 5mm od x 2" long/ T nuts 6mm id 10mm od and 2x 10mm od flat washers per bolt that were inserted under the top gaskit....For the passives I used high tensile hex head bolts 5mm od x 40mm long with the same T nuts as above and same 2x flat washers under each bolt...

The T nuts were Apoxyed in place and I then checked the bolts would go in easely and tighten up by hand so as to avoid issues latter on..
Befor the Apoxy on the T nuts had A chance to Dry I sat the Driver & passivse in place and put the bolts through to make sure the T nuts were in straight and could adjust if needed by using the bolt... I pulled out the Drivers and allowed the Apoxy two dry for 2 days...

Once the mounting holes in the Baffels were finished and the box was assembeled and dry I then fitted the outer baffel by screws and gluing liberaly both sufaces of the inner and outer baffels then clamped and left for 2 days drying...
When it came to finnishing the sub after flush trimming I used my 750w 1/4" Elu router with A round over bit to round over the top and bottom sides of the sub, for the rest of the edges I used A very small roundover bit just to take A small amount of the edges off all the corners.....
I whent with this Idea because I love the look of the JL audio Fathom Subs....




The Finnish on the Subs Are going to be A High gloss Piano Black Once I finnish my other Sub Box...

Cheers.....
Mael-X +2PR18 MDF Layout plan.jpg

2 Mael-X +2PR18 MDF Layout Plan.jpg

1 My 18in sub outside.jpg

2 My 18in Sub build Clamp.jpg

3My 18in Sub build Baffel.jpg

4My 18in Sub build flush finnish.jpg

5My 18in Sub build PR 18.jpg

6Finnished Maelstrom-x Dual PR18 Passives.JPG

PR Response Maelsrom-X 2.gif









'
 

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Discussion Starter #2 (Edited)
A few more pictures, one Of the Circle Jig I made up set to cut out the 18 &1/2" outer baffel.. 1 of the 55mm & 45mm Hex head bolts, 10mm od flat washers and the 6mm T nuts... The MDF Glue, Flush Trim Router Bits, and A couple others I threw in...

Soon I will be building the matching Maelstrom-X + 2x PR18" passives sub so I will be sure to take pictures for A step by step construction process....

Cheers.....

1Mael-X & 2x PR18s.JPG

Trimmer & CIRCLE JIG.JPG

FLUSH TRIM ROUTER BITS.JPG

Makita 2300w..JPG

Hex Head 55mm & 45mm.JPG

MDF HIGH STRENGTH GLUE.JPG
 

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Discussion Starter #3
Thought I would post A picture of the Mael-x +2 PR18" twins...
Let me Know what you think :innocent:...

I know they are cramed in and look silly but I dont wanto put them in the corners for obvious reasons and I have 2x NHT 12" sw3 subs next to each surround speaker at the rear of the theatre ..

All I can say is thank God I have Good bass traps, The Twins put out some serious low Bass :yikes: I had to turn down the DCX 2496 and the PRE processor's sub output 6db in total but still need to run Audyssey XT again...

Cheers....
 

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Discussion Starter #5
There is no shortage of bass thats for sure but, When I built the First Sub (Right side) and set it up using Audyssy XT it sounded Awesome, But with the second sub in the mix it was to loud and very boomy so I turned the Gain down 6db which helped a lot but need to re run Audyssy XT and finnish my room treatment to help tame room modes..

That is one thing I noticed with the Other Sub now in the mix, is the Lower frequency room modes stand out A lot more...

Cheers.....
 

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Discussion Starter #7
Hi Mike,
The box is tuned to around 15hz with 1500g mass added to each passive and 300g for MMP so 1800g total mass.... Kevin specs the total mass load limit for the PR18's at 1884g, so I am pretty much at the limit... I put in 1.8kg of Polyfill per box but Kevin recommended 3.2KG or 128oz from memory....

I am running the Behringer DCX2496 for Highpass and EQ as well as Audyssey XT....

Cheers....
 

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Those look great! Love the close up pictures of all your tools and materials. You have a 2300w router? Does that run on 240V? If not, how does it run??
 

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Discussion Starter #9
Hi Aaron Thankyou for the complement The boxes took me 5 days per box to construct :whew:,
Yes that router runs off 240vac as does all my Gear, but I only use that 1/2" monster for flush trimming the 32mm MDF to scary one mistake and spinning @ 23,000 RPM :yikes: Id hate to think..FWIW It is the Router out of my Router Bench...

For Cutting the holes in the Baffles I use my little 1/3" trimmer router and do 6 or so passes, and for most the other routing like corner round over I use my favourite 750w 1/3" ELU router....

Cheers....
 

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Discussion Starter #11 (Edited)
Yes in Australia the standard residential power for single phase is 240vac, and 3 phase is 415vac... 240vac is A big Plus for High performance power amps such as my Peavey CS4080 no voltage sag issues....

Cheers....
 

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Discussion Starter #12
I am looking for your oppinions on decoupling the subs from the floor but without adding much hight no more than 1/2" (even Spikes would be to high) :dunno: because the Twins are already higher than I would like and may have to move the screen up A couple of inches ...

Any suggestions would be Appreciated ?? :praying: ....

Cheers....
 

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When constructing the box I made sure that I allowed my measurements to be A little bigger than was required so I could then use my 2300w 1/2 Makita router (scary tool) with A Carb.I.Tool 1/2" 50mm cut, double bearing flush trim bit to flush trim the subs for A perfict finnish....
Very nice work! Great pics.. I like your idea of extending your cuts a little, it sure makes things easier. Say I see you like routers, have you ever used one with dust collection? I was planning on the DW621, supposedly it does very well in this regard?

Would it be a bad thing if you did move your screen up a inch or two regarding the decoupling issue? The way I'm reading it, is that you don't want to raise the subs any higher than what you have to.. "because the Twins are already higher than I would like" Looking at what you've done there, I wonder if you might come up with your own spikes and see if it's advantages or not before you commit?
 

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Discussion Starter #16
Hi Steve Thankyou for your compliment and suggestions :T,

As for love of Routers I think its called having the Right router (tools) for the right job no :bigsmile:...
I have A router Bench fitted with the large Makita router and that has A dust extractor fitted to it.. If Routing MDF especially I would recommend dust extraction if posable, routers are very messy :thumbsdown:....

I think you are right that I should move the screen up A 2"-5" But the biggest hassle is I have A HighEnd large & heavy CRT Projector that I would need to raise and then recalibrate as well :crying:.....

I think Spikes are going to be the easiest most affective way to get the Twins off the floor, my NHT SW3 subs have spikes fitted and improved the sound alot....

Cheers...
 

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If Routing MDF especially I would recommend dust extraction if posable, routers are very messy ....
LOL.. I hear you man. I have vowed to go dust extraction in the future. No more DIY until I do. I have a couple routers to save time in changing bits, but all that gets chewed up and then some, (by a long shot) vacuuming up all the dust!
But the biggest hassle is I have A HighEnd large & heavy CRT Projector that I would need to raise and then recalibrate as well .....
Oh I see.. one thing leads to another:yes:
 

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Discussion Starter #18 (Edited)
1/2 inch isn't much. The only option would be post 10 of this thread.

http://www.hometheatershack.com/forums/home-audio-acoustics/11572-isolation-platform-subwoofer.html

As stated, it's a possible solution that needs to be tested.
I ended up making some Isolation Platforms for my Front Main Speakers and Center channel But would work well for Subwoofers as well.....

I looked at what 2" thick Foam was being used with the Great Gramma Isolation Platforms and used the same foam...
I constructed them from some 32mm MDF I had laying around and 2" thick "High Density Urethane Foam",
I cut the 2"thick Urethane foam into 4" wide strips the same width as used with the Great Grammer Isolation platform x 450mm long for the main speakers, and used thick foam Glue "Selleys ALL FIX" looks A bit like mastic or no more gaps...
used A small round over, router bit and painted them matt black..

You could also use some non slip rubber on the top platform or carpet like the Great Gramma Isolation platforms, I would like to use polished Granite as the platform to add more mass and looks... For now I just sat the Isolation platform on my Granite speaker platforms.....My full range Main speakers way over 100lbs each and the High Density Urethane foam in the isolation platforms did'nt compress at all and are solid :T...

Cheers...
 

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Discussion Starter #19
Just an update on my Maelstrom-X +2 xPR" twins...
I have since purchased Acoustisofts RplusD Room Analysis software plus the consultation package with Doug Plumb of Acoustisoft currently, to help with room Acoustics and EQing the Sub Twins with the DCX2496....

I will post some in room Response graphs of the Subs performance before and after Eq...
Soon I will get the new SVS AS-EQ1 once landed in Australia and do A comparison between the Audyssey AS-EQ1 and the DCX2496 PEQ performance and post the results.....

Cheers...
 
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