Twin sub towers and layout Q

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Well I am definitely hooked now... thanks guys. I build one sub and I can't keep thinking about the next spkr build.... I have been reading up and trying to learn from all the gurus on here and have come up with some questions regarding my next project.

The idea is to build two sub towers. Towers because I don't want to lose a lot of floor real estate and each tower will need between 12 to 14 ft^3. Oh yeah and there is no wife to worry about gargantuan monstrosities in my living room :) I was going to go IB but my career path has led me to possibly moving in the next few months and subsequent moves after that (Retail management) so I want to be able to take my bass with me.

Each tower will consist of 2 15" subs in a ported enclosure, maybe utilizing a dual chamber reflex design. Initially the first tower will be setup with Quatro's as I already have one.

The questions I have arise in are there any things to look out for in designing a tall subwoofer enclosure? I am quite familiar with WinISD and several other programs for simulating enclosures.

Second question isn't necessarily sub related but is... Below are a couple of mockups in Solidworks of the floor plan of my house and living room with the sub towers and the future mains in place. As you can see my living room/ house wasn't set up with HT in mind :( I really run into some odd placement for rear speakers. Are the positions for the subs and mains ok or will I run into issues? The floor plan is accurate to approx 1/2" of the actual house. For reference wall heights are 10.25 ft by the TV.

The "mains" aren't necessarily accurate in the model as I haven't started designing them yet. They will come after the sub towers are complete and I just wanted a rough model to see how things placed out in the actual room.

Thanks in advance!!!


Click on pics for bigger versions

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An externally hosted image should be here but it was not working when we last tested it.
Hi Ethan,

I just loved the pictures. I did a drawing of my lounge room for my web site using Paint shop pro with the master pic having about 10 layers - it still didn't turn out as good as yours.

Did you use a package or was it all freehand?

On a more serious note, tall towers can run into problems with resonances. For example

A 1000mm tower has top to bottom res of 178hz.
A 2000mm ................................................ 97hz

yada yada yada.

With 2 drivers it would be best to divide the cabinet into 2 separate chambers with one driver in each. Even then, you probably need some absorbant foam on the top and bottom panels and some acoustic wool across the centre.

Post some pics when done - they should look awesome!

1. There are many things to consider with a sub design! Too many to mention. Perhaps you could be a bit more specific

2. The sub location looks pretty good actually. I consider subs placed near mains in stereo configuration is a good way to go. The main advantage is that any distortion products produced by the subs will be near the mains. These products are what stop subs being sonically "invisible."

I see no reason to be concerned about "resonances" in a subwoofer, even if it is that big. I have yet to see why this is actually a real problem in a subwoofer. Sure you may have a standing wave moving backwards and forwards inside the box, but the real issue is whether or not it will actually exit the box, either through a port, or the cone itself or the enclosure. This has nothing to do with the dimensions of the box IMO, not in any direct sense. But it is more related to the nature of the cone, the characteristics of the vent and the stiffness of the box.

A real problem I do see is a practical one. In order to make a box that big stiff, it will be very heavy. This is a construction challenge, as well as a moving challenge. I'm thinking of your back! ... from someone who went to the chiro after building much smaller speakers, and has had to do daily back stretches for years since :O

You can make your subs smaller by using drivers that don't need big boxes, also using higher excursion drivers and giving them a bit more power. Something to consider. 12" drivers use much smaller boxes as a general rule, although 15" drivers tend to offer more dispalcement per dollar I will admit.

You might even consider sonotube subs. Could make things a lot simpler. As a general rule I'd make one enclosure per driver. This means flexibility, especially if you want to experiment with different placement. This can help with room modes.

Quattro drivers are very good bang for buck it seems. But I believe they tend to need a big box. You could get a 12" driver with the same output in a much smaller box. Look at the Atlas 12" now going for $100 USD and you are looking at a MUCH better sub.
Collo, I used a program called Solidworks to model the house. It's a 3D modeling program, very nice stuff indeed. I modeled the house as a way to learn the program. I am also using it to model out the enclosure before I build it. It is very helpful in determing actual internal volume not to mention I will be able to make a detailed cut list when the design is complete which should make construction easier especially considering some of the funky angles that always seem to appear in my ideas :D

As far as weight goes, you guys are indeed correct. I may be changing out some ideas as the tower currently weighs close to 300 lbs in it's current form however that is with 1.5" thick walls all the way around. I could probably loose some weight with a thinner wall as I will be bracing it very very well.

I have looked at the sonotube designs and was thinking of going that route at first, but then I decided I wanted something unique, at least partially so.

As far as driver selection goes, I would love to have an Atlas or Avalance the only problem is I would like to have a driver that will still be available 6 months from now as well. I intend to build one of the towers now and another in about 6 months and want to have the same drivers for both.

What I want is a sub "section" that extends very very low and effortlessly so. The plan for 2 drivers per tower is actually to have the total output spl wise of 1 driver per side so as to not have to run each sub to it's very limits. The current design I have been toying around with for the 2 Quatro 15's is a total 14 ft^3 tuned to 19 hz.
Darnit PaulSpencer... I went and looked at those AVs.... bad bad thing. Now I want some. 2 to be more precise and not the 12s either. Those aluminum cones just look so good...

I modeled out the 12s and 15s in WinISD and I would rather have a montrosity of a box for the resultant output the 15s are capable of rather than a more reasonable box size with the 12s. I may just be satisfied with one of those dual AV15 setups...

Btw, I check out the dual AV15s on your site and that is a little more of what I was thinking about. But by the way the links for the diysubs are not working. I was able to see the projects after cutting down the extraneous "DIYsubs" folder in the link address.
Hi again Ethan,

thanks for the info on Solidworks (I should have read the original post a bit more carefully) - I looked it up on the net and it looks like a nice product!

As for resonances, I think they are more audible with a ported sub as the sound can get out. I built one that had a 6dB peak at 120hz as measured with an SPL meter. Using damping, I was able to tame it - its just one more thing to watch out for!

You might want to check out the Avalanche drivers from Ascendant Audio

I'm not sure if they are the same ones Paul used from Stryke.

Last time I looked (about a month ago), they were running out some of their XBL drivers at good prices. They also have a well supported discussion forum.

We don't have a lot to choose from here in Aussie, so the next build might involve some importing.

Thanks for the reminder and compliments. My site needs a lot of work actually!

I believe AA are changing the motor but using the same basic parts - cone, basket, etc. Hence they would look the same, but the price is so good I'd just buy 2 right away. $105 for a 15" driver of that quality really is a dream. And you guys in the US really are spoilt, we have to pay a lot of money for shipping! Drivers we buy that are available locally are often about the cost of getting them shipped from the US.

I know what you mean, sonosubs are common and not inspiring in their form. I'm all for funky designs, they are a lot more fun. What is challenging, is to make a big sub look sexy. I once was working on a curvy design, and it looked great for a 60L box, but for 140L it just looked plain old big n ugly, curves notwithstanding.

Rather than make a dual driver per enclosure sub, I'd instead stack them if you wish.
You have a very good point about size, weight and placement. Even though lifting one 200 lb "module" on top of another would require some effort.

Has anyone seen this reasearch on sub placement vs. room modes? I saw the link today and it is quite interesting. Comments?

If the research presented is true, I would be better off building 2 subs and later upgrading to 4 but all in different placements. With my current single sub setup, and the really odd shape of my room I have some serious room mode cancellations. I ended up with the sub on the wall to my left as it was less obvious there. Now if I go walk down the hallway towards the front door, right by the door the bass is amazing. Hmmm. Maybe I should move the sub to the front door and fire it down towards the living room. :devilr:
I'm familiar with the paper, but I would not follow their placement. There is more to sub placement than room modes. If all you want to do is reduce room modes, the very best placement is one sub either side of your seat! That in fact gets a smoother response than a dipole!

I would place subs to integrate best with the mains as I consider this the most important thing. This means stereo configuration ideally placed as close to the mains as possible.
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