# 2x2xSDX10 Plan



## hgoed

I'm hoping to document my build of a pair of 2xSDX 10 subs. I've nothing to share yet, but I find that I'm much less likely to complete a project if I don't announce my plans and open myself up to public ridicule if I don't follow through.

The plan is for sealed. I'm aiming for about 4ft3 internal. I tend toward OCD, so I thought if I made a sealed sub I wouldn't feel compelled to over-calculate everything.

I'd like to face the drivers back-to-back on each side of the box and placing them as stands for the mains. I've heard varying opinions about this setup, but not much data to support anyone's opinion. Symmetrical placement would simplify EQ (looking at antimode 8033 vs. custom/REW--but see OCD comment above). 

I'm wondering, 'though, about the drivers that would face toward the equipment/TV in the center. Is this a bad idea, or is there a recommended setup so as not to create any peaks from reflection?

Thanks for any input, encouragement or even flames.


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## Mike P.

Is this for home theater, music, or both?


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## hgoed

If you consider the system by time of use, I'd say it's 70% HT, 30% Music.
By motivation for building a sub, it's probably 100% for HT, because I probably wouldn't build one if I only listened to music.
By factors that influenced the design choice its about 70% music.

Simple enough answer?

I want something that can reach to about 30-35Hz in room and sound as nice as possible. I don't need to shake the house, and I've been pretty turned off by many of the subs I've heard in the past as sounding a bit like a whoopie cushion.

Size wise I'm flexible and had considered a single 15" per side. The idea is to cross it at 80HZ, but I might experiment with as high as 120HZ.


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## Mike P.

"Nice as possible" for music usually means a Q of .7, 4 cu.ft will have a Q of .56. The smaller box provides the required Q for music and better power handling. They pretty much have the same output from 30 hz down.


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## hgoed

Hmmm. I just used an online calculator for .577 and .6 and just chose a round number somewhere inbetween to come up with that 4ft3 number, because I figured stuffing would basically equal the driver and brace volume. Your graphs show that I would basically just be wasting wood by making the larger enclosure.

So, the 1.7ft3 you show would be just over a 14" cube. Wow!! This is why the smartest thing someone can do is ask for help.

Would there be any problem caused by the two drivers being placed back to back so close together--it looks like each driver is about 6 3/4" deep so that's only 1/2" plus 2x the thickness of the wood (unless sub drivers are recessed into the baffle) between the driver backs.


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## Mike P.

This sub has a pole vent for cooling in the middle of the magnet, I think 2" of space will be OK but contact CSS to make sure. What will you be powering the subs with?


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## hgoed

That's kind of up in the air, and part of the reason I chose to stick with 10"

It's not right now, but I plan on installing solar onto my house in the next couple of years. That means I have a strong incentive to keep things as low power as possible. I've been looking at what's available in digital or class D amps. I'd like to see the power draw of the Behringer iNuke amps once they're available, 'cause one of them per side (one channel per driver for four channels total) seems like it would work quite well with this driver.

I'll have to look up what a pole vent is. Rest assured, I will definitely call ?Bob? before purchasing to discuss the project. From what I've been able to gather, he seems like a decent fellow, and that's one of the reasons I was looking at this driver. Hopefully, if I'm successful, I can document things for others as well.

I also looked at the upcoming SDX-15, but it looks like I'd have to burn too much coal to enjoy that driver.


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## Mike P.

You're building 2 cabinets with 2 subs in each, correct?


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## hgoed

That's the idea. Back-to-back SDX-10 so there is little vibration as I'd at least like to attempt to put the mains on top. Worried about the inward facing drivers, but I haven't really sat down to draw/simulate yet. I'm still in the brainstorm (i.e. many bad ideas, but ideally one good idea) stage.


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## Mike P.

All 4 subs wired for a 4 ohm load, the iNuke 1000 bridged would power all of them.

How close to the drivers will the equipment/TV be?


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## hgoed

I thought it would be better to wire each driver to one output individually (2xiNuke 1000). Would I really need to bridge the amp in a 14x18 room? I'll have to admit that my listening experience has a real gap between makeshift and over-the-top.

The mains will be about 8' apart C-C. (here's a .pdf of the room, the mains will be right next to the windows which are 9.25' c-c and 2' wide:

View attachment Doc1.pdf


So if the sub boxes are 14" wide and the equipment stand is about 24" wide. That leaves about 2' from the driver edge to the equipment stand. I should figure out if I should have the bottom rung of the equipment stand as acoustically transparent, or I could make it absorptive with foam/cotton or whatever.

Can you tell me what you're thinking, 'cause most of my ideas are based on the idea of starting off with good enough, and fixing any problems later. I'm open to anything as long as I can eventually make things presentable/palatable when the boss gets home.

I'd also considered some kind of triangle arrangement with 3 drivers, but the rear driver would have to be pretty close to the back wall in order not to move the seating position too far back.


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## Mike P.

My idea is don't spend money unless you have to. One amp bridged powering all 4 subs will provide 112 db at 30 hz. If you find that you do drive them that hard and the amp starts clipping because its maxed out then get the second amp. Be aware that the second amp won't produce any noticeable improvement in SPL, it will only provide a power reserve. At 1500 watts the subs are running out of power handling and cone excursion, the difference between 1000 watts and 1500 watts is 1 db in output.

I don't see the sub being 24" from the stand as a problem.


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## hgoed

I guess, since the plan is to have the two subs placed symmetrically, I don't have to worry about EQ/time correction ect...to each signal individually. I think that was the original reason I had wanted two amps. Sometimes ideas just get stuck in the head long after their source is forgotten.


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## GranteedEV

> "Nice as possible" for music usually means a Q of .7, 4 cu.ft will have a Q of .56. The smaller box provides the required Q for music and better power handling. They pretty much have the same output from 30 hz down.


4 cu ft will be much more tight and dry with the lower Q. Part of it depends on personal preference but strictly speaking, the closer-to-.5 Q will have a more lifelike transient sound. .7 will however have a more "punchy" and "present" bass sound. I would steer clear of anything with a higher Q than .7 either way.


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## hgoed

Unfortunately I don't know what my personal preference is. Although I've been interested in this for quite a long time, I hadn't before had any money of my own to experiment with, or much time to listen to anyone else's designs. Nice thing about DIY is I can try one design and if I don't like it I've really only lost some wood and glue (chalking up the time spent to skill-building). Maybe I'll build both anyway so I can compare. 

I have 1-1/2 weeks 'till I can use my garage again, so I guess I'll let myself fret until that point and then I just have to jump.


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## hgoed

Well...I've had my four drivers sitting out on a desk for a little while, and they whisper to me at night...I think it's time to give them something else to do. 

I decided to build a box with internal dimensions of 14x16x18" mostly because those numbers were convenient for placement and I'm unlikely to mess anything up when cutting. 

The response looks OK with winISD, especially with a HP at 20Hz and a little EQ at 30Hz. I got a couple of IcePower 1000asp modules and will likely get a MiniDSP for the EQ. I went with dual amps, because it allows me to move the amps with the sub boxes independently. I decided not to use the iNuke amps mostly because I couldn't figure out how to integrate the aesthetics in my living room. 

I delayed the build a bit, because I had been considering using some kind of leather wrap for the finish, and I wasn't sure how that would work once the panels were glued. I decided only to learn one skill at a time, so I'll figure out the finish when I've got the box built.

Anyway I have a couple of questions for anyone who's read this far--
For a sub, is there any benefit to flush mounting the drivers? This would necessitate my doubling up on the baffles, so I only want to do it if there's something to be gained.

Also, my understanding about wiring the drivers is that 4ohms allows more total power, but provides a more difficult load to the amp. 8ohms is easier with less max power available. Given that I have more power than the drivers can handle anyway, are there any other considerations? Otherwise, I'm just going to wire for 8ohms. 

Thanks for any advice. Hopefully I'll have some pictures soon.


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## hgoed

I was re-reading this thread just to make sure I understood everything, and Mike, if you read this, I have a question for you...post #12 you said that at 1500W the subs are running out of power and excursion. The graphs I've made show peak excursion reached at right around 500W. I'm pretty sure were using the same the 18.4mm XMax. What haven't I considered?


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## Mike P.

Upload your project file so I can have a look.


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## hgoed

This is what I was playing with on WinISDalpha...First graph at 1500W, next 2 at 500W.


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## Mike P.

I modeled 4 subs, two 1.7 cu.ft. cabinets with 2 subs in each, no HPF. You are modeling a larger cabinet with a HPF and 3 db of boost at 30 hz, that changes everything.


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## hgoed

Maybe I'm doing something wrong, that first graph was with no HPF or EQ. I'll try to model your exact parameters when I get home. Maybe it'll seem obvious when I'm back in the program, but for clarity--when you say you modeled 4 subs (2 pair), how did you do that for two cabs?

BTW--sorry for the big pics. I'll try to edit them down later as well.


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## Mike P.

Either model 4 drivers in 3.4 cu.ft. or model 2 drivers in 1.7 cu.ft., figure out the power handling x 2.


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## hgoed

Thanks. I tried that and see what you were saying. Sorry for being a little dense.


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## Mike P.

You can add boost if you want but you'll have to lower the input power to control excursion.


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## hgoed

I'm reviving this thread to update on my progress and a fall plan. 
I built one (single driver) SDX10 sealed sub with just arbitrary volume and put together in a rush as a project with a child. Now it's time for the real designs.

I just ordered 4 more drivers.
I'm going to build both of the sealed 2-driver subs we talked about above, as well as a dual driver tapped horn discussed on another thread. 

I'm also going to try two single driver ported versions. Those, if they are any good, will be part of a wedding gift for my brother, so I'm not trying to indicate that I'll have 8 10" drivers running in the same room in 3 different designs. The reason I mention this here is that, as soon as I learn how to do the measurements, I plan to post comparative responses with a number of configurations run in the same room. I still need a decent mic and mic-amp, 'cause the experimental stuff I've been doing isn't really publishable work.


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## Oklahoma Wolf

hgoed said:


> as well as a dual driver tapped horn discussed on another thread.


Can't wait to see what you think of it


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## ironglen

Direct enclosure comparo's: hard to come by, and will be appreciated by many, especially your impressions as we can look at models all day long :whistling: (I'd like to see/hear from another regarding that dual SDX10 TH build!)


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## hgoed

I'll do my best to provide some useful information...I feel I owe that to those countless others who have shared their experiments and projects. 

I’ll try to give some gut impressions, but I should warn that started my interest in audio about 22 years ago when I was in grad school for neuroscience (that’s not what I do now), so I don’t think I will be able to resist taking lots of measurements, even if I have no real idea what to do with them. I’ve had lots of thoughts in that time, but it took until just recently that I had the space, time, or money (at least enough for DIY) to play around. 

Also, I don’t think there is much objective data out there describing different designs, just descriptive terms like “boomy” “dry” “musical” etc... Maybe I can elaborate on those impressions without being particularly attached to a single type of box. I can honestly tell you that nothing I build will have been designed by me (that was on purpose), so I’m just going to listen…adjust…listen...adjust, then take a few days off work so I can relax and try to see which setup I personally think is most enjoyable. 

After all that, I have to figure out how to make it work aesthetically before my wife gets home. [19 months and counting--see why I’m really into movies right now?]


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## Oklahoma Wolf

hgoed said:


> I don’t think I will be able to resist taking lots of measurements, even if I have no real idea what to do with them.


I'd love to see some measurements of the TH - heaven knows I don't have the gear to do a proper job myself yet.


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## nc535

We should compare notes. I just finished a 65L=2.3 cu.ft. sealed sdx10 and am 1/2 thru the 2nd. The predicted response, including room gain and boundary reinforcement from being tight to the wall is shown in the attached. Note also that the driver is 12" above a tile floor. This, the wall, and the corner raise the level about 9 db from anechoic at 20 Hz. 

When I REWed it in house, I used 5 db boost at 20 Hz instead of the predicted 3db. I had too many room modes and boundary reflections to make sense of the data. I'm waiting to finish the 2nd unit to deal with them and equalize flat at my listening position using DSP built into my amp.

Four SDX10's would be a lot based upon the levels I'm getting out of one. Certainly true if you place them close to the wall and floor or a corner. Others say close to the wall in front is worst case for exciting room modes. I'm trying close to the wall first because I have limited front to back space. I might have to add a 3rd or even 4th sub to smooth out the room modes.


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## nc535

I forgot to mention. I noticed some differences between your WinISD model for the SDX10 and mine - the VAS parameter, Le and Z. Its tricky to create these models, as you may have found. You have to enter parameters in the correct order and let it calculate some of them from the others that you have entered. Here is my model file in case it helps.


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## hgoed

What's your room like? I'm guessing that may affect the need for more air movement. Mine is not so big by some peoples standards, but it's open to the rest of the house. I'd split up the drivers into four separate subs if I could figure out what to do with all of the wires. I figured I'd deal with the room modes after I get things set up initially first. Some of that could be as simple as nudging a box. 

I wanted sealed subs on the front wall so that I could play with custom setups for music vs. HT. I'd been thinking of cutting the low-pass higher than usual for music, but that would mean the sub driver would have to be pretty close to the front speakers.

Regarding the speaker parameters--I think I just took a file from someone else. I have to purposely try to distance myself from the design work due to my debilitating OCD--if I find a minor/insignificant error I'm likely to scrap everything and start over. I'm pretty sure most of these drivers have significant electrical variance anyway, but with a sealed box it shouldn't matter at all.


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## nc535

I'd say the same about mine. One leg of an L. the other leg is a 2 story dining+living room; kitchen at the corner. cathedral ceiling with balcony looking down into both family and living rooms. Your thinking mimics mine as well about sealed and multi-subs, which I can see are in my future, and tuning sound with digital crossover equalizer. I don't know if I'm obsessive but I want an accurate simulation and then verify the box works like simulated so I don't have to do so many iterations to get it right.

Hide wires? not that hard. Pull off the baseboard and route a channel behind it in the sheetrock.


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## hgoed

@NC535: 

I know a lot about a few things, but nothing about a lot of things. Since the last line of your last post, I've been picking at my baseboard trying to figure out how to pull it off and get it back on without looking messy. It's kind of funny to me, but somehow fishing wire through complex routing seems more palatable. I've basically sullied my entire house with audio experiments, but I'm afraid to touch the trim, because I had someone else put it on and paint it. It's like I'm playing with the Cat in the Hat...I can do whatever I want, as long as it's cleaned up before the wife gets home.


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## nc535

one of those things that is easy to say but hard to do - unless you know the trick. you need the right tool to slip behind the BB and pry it out over the heads of the finish nails without marring the paint on the wall behind it. Long ago a carpet installer left this combined scraper, knife tool at my house and I found its great for that purpose. It has a dull knife edgethat finds behind but it tapers to a 1/8" thick body that is strong enough for the prying job. If I can find a picture or find my tool, I will post it. PS. enjoyed your post.


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## informel

Mike P. said:


> "Nice as possible" for music usually means a Q of .7, 4 cu.ft will have a Q of .56. The smaller box provides the required Q for music and better power handling. They pretty much have the same output from 30 hz down.


the smaller box will be more musical, does that mean an IB sub is not really good for musing.
I am not trying to be a smart ... here, just wondering if that does not apply to IB


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## nc535

I forgive you for the intended pun. Perhaps save you from spending a lot of time thinking about this. In IB with no box its the driver Q, not the box Q, that determines the dynamics of the sound.


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