15” dual opposed second sub selection - Home Theater Forum and Systems - HomeTheaterShack.com

Thread Tools
post #1 of 7 Old 05-25-12, 05:53 PM Thread Starter
Join Date: Jan 2010
Location: Cape Town
Posts: 20
15” dual opposed second sub selection

Hello Everyone,

First some Background

It all started with DIY dual opposed thread from Kramskoi here on HTS.
Which lead me to spend the next few days reading countless threads such as
All 54 pages of Bid Daddy upgrades over at Blu-ray forums and all 27 pages of PBC’s DIY journey on AVS.
The final nail in the coffin was the dual opposed video from ‘The Prof’.

So I’ve decided to try and build a 15” dual opposed second sub to work alongside my Paradigm Sub15.

Current Sound Setup
KEF Q towers front and back.
Sub – Paradigm Sub 15
AMP Yamaha and Rotel

Usage will be primarily HT - 90% at least.

Room – 6m x 5m x 2.60 high (+ 220mm false ceiling with 150mm eco-friendly polyester)
Room – 19 x 16 x 8.5 feet
All walls are 280mm thick - brick and plaster.

We recently renovated and I have already a dedicated 20Amp (220v) plug point and 25mm PVC pipes in the walls and floor to the respective points.
Therefore I am limited in terms of placement.
With the DIY Sub being so close to the second couch, I did not want it vibrating up against the couch.
I plan to have the woofers facing the front and back walls thereby leaving ample room instead of having the woofers face the couch and wall.

Driver Options:
Dayton Titanic MK3 - $234 each
Is the TC LMS-R really worth the extra $400 ???

Amp Options:
Behringer EPX4000 - $400 (RMS power rating 2x 870 W into 4 Ohm)

From what I understand, the Amp would be able to give each channel about 800W RMS.
Was thinking about wiring it such that the Amp is presented with a 4-Ohm load per channel per driver.
Would also replace the fans with low noise variants from Digikey (P14751-ND)

My maximum box size limitations are as follows:
Height – 700 mm / 27.5 inches
Width – 1000 mm / 39 inches
Depth – 570 mm / 22.5 inches (Where drivers/baffle would be)

I’ve used WinISD, Boxnotes and Unibox but still not sure what size box I should use. (Box must be sealed)

WinISD claims I need a 300 litre box for a Q of 0.700 and a 400L for a Q of 6.5
Boxnotes does not like any box wider than 900mm (issues with resonant frequencies) – possible bad idea anyway for dual opposed design.
Unibox calculates
Dayton Titanic - 235L for Q of 0.7 and a 280L for a Q of 0.675
TC LMS-R – 159L for Q of 0.7 and 186L for a Q of 0.675

Additional questions around ideal box volume

I’ve read that a Q of 0.7 gives you the flattest response but you get room gain so if possible to aim for a Q factor that’s lower than 0.7.
Should the volume calculated take into account the volume lost to the drivers/bracing or will the polyfill ‘perceived increase’ make up the difference?
Comments or suggestions on that?

I plan on using 25mm / 1 inch MDF as I can source that locally without too much hassle.
Air temp is generally around 25 Celsius and humidity around 60%.
Internally the box would have panels with acoustic foam and be stuffed with polyfill.
I have most of the tools and access to those I’m missing. Never build a sub box before but have built other items. Only concern is the cutting of perfect circles for the baffle. Might have to outsource that locally.

I really require assistance in the box size calculation and look forward to comments and suggestions around the driver and amp selection.

With the Dayton Titantic MK3 was thinking about a 240L polyfill stuffed box. Hoping for a 10% increase in perceived volume giving me 264L.
650 x 850 x 550 (HxLxD) Outside dimensions
25.6 x 33.5 x 21.65

Thank you all for your time and help.

The pictures in my public Dropbox illustrate it better but will have to wait for 5 posts to share.
Nceitil is offline  
Sponsored Links
post #2 of 7 Old 05-25-12, 08:29 PM
Join Date: Dec 2011
Posts: 24
Re: 15” dual opposed second sub selection

you can pad your 5 posts here.
paskal is offline  
post #3 of 7 Old 05-25-12, 11:31 PM
Senior Shackster
Join Date: Nov 2010
Location: Austin, TX
Posts: 298
Re: 15” dual opposed second sub selection

I couldn't be happier with my dual MkIII's. I modeled a lot of drivers. I came to the conclusion that each extra $100 got me another 1dB of max output and not as flat of a response. Not nearly worth it. Perhaps the Daytons aren't as low distortion as the mega-bucks drivers? I don't know, can't say. Does anyone have a way to measure such a thing? Anyway, I love my setup (check my build link below). You can catch the MkIII's on sale at PE sometimes. I got one of my two on sale for $150. You can also read the MkIII kit reviews. I think you'll see people are quite happy with it even in that not so great sealed kit box (sorry PE). I had the kit originally and decided to replace the cabinet with my LLT and Behringer - whoa baby, what a difference 14Hz will make!

Anyway, I don't see how you can beat the performancerice ration of the MkIII. Almost all the xmax of the big boys without all the loans.
Wooderson is offline  
post #4 of 7 Old 05-26-12, 03:51 AM Thread Starter
Join Date: Jan 2010
Location: Cape Town
Posts: 20
Re: 15” dual opposed second sub selection

Thanks to some padding.. Here is the additional info if anyone is interested.

Room Layout - https://dl.dropbox.com/u/26125279/Vi...ROOM%20v10.pdf
Tool Screenshots - https://dl.dropbox.com/u/26125279/Screenshots.rar
Driver Specs - https://dl.dropbox.com/u/26125279/Dayton%20vs%20TC.xlsx

I see you landed up using the EP4000. I assume you running each Dayton 4-ohms into each channel on the EP4k. Any issues or things you might do different in hindsight?
From what I've read there is not too much difference between the EP4k and the EPX4k.
I'm need to use the EPX primarily due to the weight. Weight Saving = Shipping Cost Savings.

I need to prepare myself for significant amount of time and effort to cutting perfect circles and getting the bracing 'just right'. 8 months of weekends and week nights - a minor cost to pay for the pursuit of bass happiness..

Good to hear the Dayton can output low and clean. I'm really interested in the 10 to 90Hz.
My towers have pretty decent mid-bass.
Nceitil is offline  
post #5 of 7 Old 05-26-12, 09:17 AM
Senior Shackster
Join Date: Nov 2010
Location: Austin, TX
Posts: 298
Re: 15” dual opposed second sub selection

I guess you're space limited? I would strongly consider a ported design. I came from sealed to ported and I'm never going back. Even my little 8" music sub sounds incredible (loud/clean) due to the almost-free output from the backwave. Yep 4ohm/ch to the EP4k. That's enough to get me to > 120dB @ 20Hz. I bought it used from the forums here and it was already fan-modded (nice!).

Don't worry about circle cutting. You just need a plunge router. It will take about an hour to build the jig you see in my thread. Make sure you use my hole-in-your-cutting-table w/ nail through both method. You can't have what will be the cut-away being your only anchor for obvious reasons.

Things I would do different:
* Seriously consider a sonotube design. My square cabinets took some serious hours to build. And I'm not a big fan of woodworking. I do it only to get to the bass.
* I would slot port instead of round port.
* Straight to the MiniDSP. But I'm using the FBDP on my little 8" so it didn't go to waste.
* Probably a little more bracing. I like the way my 8" turned out. Nothing but thud no matter where I knuckle rap.
* I would've painted with just oil-based black and no clear coats. But I'm not that much on looks as you can see. Repeat: I'm no word working genius. I just want the bass baby.

REW is mandatory to finish off your effort. It's amazing how many of these builders don't finish the job with a touch of DRC. And for my ported design, the soft HPF at 13Hz made a (War of the) World(s) of difference. I was hitting Xmech in the deepest, loudest passages (The Pacific, Iron Man, etc).

Good luck!
Wooderson is offline  
post #6 of 7 Old 05-28-12, 04:06 PM Thread Starter
Join Date: Jan 2010
Location: Cape Town
Posts: 20
Re: 15” dual opposed second sub selection

Can anyone comment on what (if any) is the best practice in terms of distance between the drivers in a dual opposed setup?

When striving for a Q of 0.7 - would both these statements be true

A - Build a box (no stuffing) with sufficient internal volume that takes into account bracing and drivers
B - Build a box smaller than calculated, take into account bracing and drivers and add 30% increase in perceived volume for a heavy stuff box (1lb per cu ft)

Nceitil is offline  
post #7 of 7 Old 05-29-12, 11:19 AM
Join Date: Jul 2010
Location: Moore, OK
Posts: 77
Re: 15” dual opposed second sub selection

A major benefit is connecting the drivers together via bracing of somesort internally, but you want to make sure you leave a gap for air to dissipate if the poles are vented. If you are able to secure the drivers together then your enclosure should be virtually vibration free.

I've been looking at the Polk MM line lately, they model well sealed (smallish boxes) - model numbers are 12s: MM1240/MM1240DVC and 15s: MM1540/MM1540DVC
Photochop is offline  


15” , dual , opposed , selection

Quick Reply

Register Now



Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address



Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.


See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


For the best viewing experience please update your browser to Google Chrome