Atlas 12 plans?

[anonymouse]

I just bought an Atlas 12 on the FM to build a DIY HT sub. I have a NAD 2200PE amp (400WPC into 4 ohms bridged mono) to drive this. I have been looking around for good plans for this driver, but there is not too much by way of readymade plans for a first time. Any advice/wisdom on this topic from the seniors?

[gatemplin]

Try searching the forums at www.htguide.com and www.diyaudio.com for projects with the Atlas. Off the top of my head, I think I recall that the Atlas was so similar to the Adire Shiva that you could copy those plans.

[tryrrthg]

I ran a quick sim on WinISD and the EBS shiva plans will work. You'll just have to watch the volume, 400 watts will push the atlas 12 past it's excursion limits in the 30hz range.

I've attached the Shiva plans below.

[anonymouse]

Thanks guys. The shiva plans are pretty detailed. I am thinking on going with the largest 142L design. Will the tuning port dimensions be the same for the Atlas and the Shiva? Are there any differences at all or are these drivers pretty much identical.

[okiepolkie]

This might not apply here, but I was under the impression the XBL2 technology all but eliminated the excursion limit.

[tryrrthg]

Originally Posted by okiepolkie

This might not apply here, but I was under the impression the XBL2 technology all but eliminated the excursion limit.

The driver still has an excursion limit, but you can't BOTTOM the Atlas drivers but I would imagine that continually running them to excursion limits cannot be a good thing.

[tryrrthg]

Originally Posted by anonymouse

Thanks guys. The shiva plans are pretty detailed. I am thinking on going with the largest 142L design. Will the tuning port dimensions be the same for the Atlas and the Shiva? Are there any differences at all or are these drivers pretty much identical.

You should be fine with the same port length. You're tuning the box, not the woofer.

[okiepolkie]

Originally Posted by tryrrthg

The driver still has an excursion limit, but you can't BOTTOM the Atlas drivers but I would imagine that continually running them to excursion limits cannot be a good thing.

That makes sense. Would one of the different wiring configurations resolve this issue any. If I remember correctly, the two voice coils are different resistances. One is 4 ohm, but I can't remember what the other one is.

[tryrrthg]

Originally Posted by okiepolkie

That makes sense. Would one of the different wiring configurations resolve this issue any. If I remember correctly, the two voice coils are different resistances. One is 4 ohm, but I can't remember what the other one is.

I doubt it. The excursion of the driver depends on how much power you're feeding it and how loud you're playing it. The size of your enclosure and tuning point also play a BIG role.

[gatemplin]

Originally Posted by okiepolkie

This might not apply here, but I was under the impression the XBL2 technology all but eliminated the excursion limit.

The main purpose of XBL^2 tech is to make the BL curve flatter, reducing intermodulation distortion. The speakers in my sig use XBL^2 drivers. There are other benefits too.

[gatemplin]

Originally Posted by tryrrthg

The driver still has an excursion limit, but you can't BOTTOM the Atlas drivers but I would imagine that continually running them to excursion limits cannot be a good thing.

All the bottom-less design means is that the voice coil former cant hit the back plate of the motor. It means that Xmech is higher than Xsus. XBL^2 motors do have shorter voice coils, which is a big reason why the former can't hit the back plate. So the suspension will bottom out before the former hits the back plate. I've done both, and either is not good.

[gatemplin]

Originally Posted by okiepolkie

That makes sense. Would one of the different wiring configurations resolve this issue any. If I remember correctly, the two voice coils are different resistances. One is 4 ohm, but I can't remember what the other one is.

There is really only one main voice coil, it is not really a DVC driver. There is the one main coil and the second is used to vary the Qts (tendency to resonate at Fs) for different applications. The small one has a much lower power handling and cant be parralled with the main coil.

[anonymouse]

Thanks for the pointers guys. In the Shiva plans, there is a discussion about the Shiva driver being optimized for downfiring mode. Will the Atlas perform as well in this config, or is it better to have it forward firing? How much of a difference will gravity make?

[Chewie]

I built a ported 95L downfiring Atlas 12" earlier this year and it works great. Contact Chad at AscendantAudio and he will be happy to make recommendations.

You can see a pic here:
http://www.polkaudio.com/forums/show...p?userid=60636

[anonymouse]

Originally Posted by Chewie

I built a ported 95L downfiring Atlas 12" earlier this year and it works great. Contact Chad at AscendantAudio and he will be happy to make recommendations.

You can see a pic here:
http://www.polkaudio.com/forums/show...p?userid=60636

That is some excellent work. The finish looks beautiful in the picture. What did you use? Does it look as gorgeous up close?

Ok, so dholmes is selling a 1000W plate amp in the FM. I know it is way overkill, but will the headroom improve the performance by controlling the cone better?

Do I get in touch with Chad at info@ascendantaudio.com ?

[anonymouse]

Originally Posted by tryrrthg

I ran a quick sim on WinISD and the EBS shiva plans will work. You'll just have to watch the volume, 400 watts will push the atlas 12 past it's excursion limits in the 30hz range.

I've attached the Shiva plans below.

I plan to go with the EBS configuration. doro has some 3" SVS ports - 12Lx3W/D with 4 3/4 smooth flare ports, on each end. The output port has a trim,mounting ring attached.

My question is - can I use two 3" ports, instead of a single 4"? The cross sectional surface area of the ports is not that different - 56.556 sq inches for the sum of two 3" ports vs. 50.272 sq inches for a single 4" port. The cost of a port is negligible in comparison to the overall sub, so I do not want to do this if there is going to be any degradation of sound. Anybody have an opinion on this?

[tryrrthg]

Originally Posted by anonymouse

I plan to go with the EBS configuration. doro has some 3" SVS ports - 12Lx3W/D with 4 3/4 smooth flare ports, on each end. The output port has a trim,mounting ring attached.

My question is - can I use two 3" ports, instead of a single 4"? The cross sectional surface area of the ports is not that different - 56.556 sq inches for the sum of two 3" ports vs. 50.272 sq inches for a single 4" port. The cost of a port is negligible in comparison to the overall sub, so I do not want to do this if there is going to be any degradation of sound. Anybody have an opinion on this?

That would probably be fine, however, it will change the internal volume of your enclosure and raise the tune a bit. You also want to make sure that your ports are far enough away from the interior walls (the rule of thumb is usually one port diameter away). which could make things difficult if you plan on following the Shiva plans. If it were me, I would just get the 4" port to make it easier on myself, but either would probalby work ok.

[anonymouse]

Originally Posted by tryrrthg

That would probably be fine, however, it will change the internal volume of your enclosure and raise the tune a bit. You also want to make sure that your ports are far enough away from the interior walls (the rule of thumb is usually one port diameter away). which could make things difficult if you plan on following the Shiva plans. If it were me, I would just get the 4" port to make it easier on myself, but either would probalby work ok.

Will this port work? http://www.partsexpress.com/pe/showd...number=268-352

Should I cut the center tube to 12" as suggested in the Shiva plans for the FP-4 vent kit?

[gatemplin]

Originally Posted by anonymouse

Will this port work? http://www.partsexpress.com/pe/showd...number=268-352

Should I cut the center tube to 12" as suggested in the Shiva plans for the FP-4 vent kit?

That is an excellent flared port. I use two with my Tempest. You can use clear silicone to fit the parts together.

You can cut the center tube to 12", that is the same as the FP-4 port.

[tryrrthg]

That's the port I used on my sonosub. The center tube should be 12" when you get it. no need to cut anything.

[anonymouse]

So Lowe's sells a huge sheet of MDF. There is no way I could fit that in my truck (mini SUV). Anybody know if they will make a few cuts to my specs so I can take it home? Has anybody tried the 7 ply cedar that they sell? Some other forum posts say that cedar ply is better than MDF. The stuff is a lot more expensive - is it worth it?

[gatemplin]

I've never heard cedar ply is better (maybe it is), but 13 ply baltic birch is. Lowe's will probably cut MDF for you, but if they dont, use ply.

[tryrrthg]

I've had lowes cut things quite a few times. I don't think they'll make precise cuts for you but they will rip it down so you can fit it in your car. If you don't have a way of making the cuts at home you might have to find a specialty woodworking shop that could make the precise cuts for you.

Oh, just thought of something. Home Depot carries "project panels" they have 2'x2' and 2'x4' sheets of MDF, so you might want to try there for something smaller.

I was told by ThomasW over at the HT Forum that just any plywood is not good to use for an enclosure. It should be void free baltic birch ply, not even cabinet grade plywood is supposed to be used.

[Chewie]

I used 1" MDF for my cabinet. Had to order it from a lumber yard.

[anonymouse]

In the course of reading up on plans, I came across Sonosubs which seem to be far easier to build. Has anybody here constructed a sonosub around an Atlas 12 or Shiva 12?

[tryrrthg]

I created a sonosub for the old SVS ISD driver. The specs for that driver were pretty much identical to the Shiva. I had size constraints so I built mine slightly smaller than I would have liked to. Here is a link to some build pics from my sonosub.

http://www.angelfire.com/alt/tryrrth...b/sonosub.html

I also helped gmorris design his sonosub for his Atlas 15

http://www.polkaudio.com/forums/show...hlight=sonosub

Building a sonosub for the atlas 12 wouldn't be any different than following the box plan. you just have to figure out the internal volume of the tube, easy as that. After going through the process of building a box for my Atlas 15, I would definitely say that building a sonosub is easier. I think next time I try a box sub it will be easier.

[tryrrthg]

Found it, here is a handy little tool to figure out how tall the tube needs to be for a given internal volume.

http://www.quux.net/roo/diy/sonosub/sonocalc.html

[anonymouse]

Originally Posted by tryrrthg

Found it, here is a handy little tool to figure out how tall the tube needs to be for a given internal volume.

http://www.quux.net/roo/diy/sonosub/sonocalc.html

Thanks, that really helps a lot. The only thing I am unclear about is what correction factor to apply for the port. The port will be one of the PE 4" ports, which has tapered ends, so I am sure the volume it is calculating does not take this into account. Also, how do I calculate port length? Will the port length be the same as the rectangular box? i.e. 12" center tube?

[tryrrthg]

Originally Posted by anonymouse

Thanks, that really helps a lot. The only thing I am unclear about is what correction factor to apply for the port. The port will be one of the PE 4" ports, which has tapered ends, so I am sure the volume it is calculating does not take this into account. Also, how do I calculate port length? Will the port length be the same as the rectangular box? i.e. 12" center tube?

Yeah, everything stays the same as the box plan as long as you keep the internal volume the same (142 liters).

I believe with a 12" center tube the whole flared port assembly is 18" long, so just use 18-19" for port length and that should be close enough to compensate for the flares.