box help for mixed audio/ht,

[sphynx_000]

This will be my first HT subwoofer project, so I am just looking for some opinions on a box design.

I often prefer sealed over ported boxes in car audio, and I will be using this system greater than half the time for music. I figured I should stick with a sealed box for my home system also.

I will be have 2 shivas, I haven decided on amplification yet, but it will be at least 300 watts per woofer.

Adire recomends a 45 liter sealed box for mixed audio/HT, qtc .707. This is what I am leaning towards. I listen to large variety of music, and enjoy some heavy/impactful bass from time to time . I would like the system to be able to handle some the of the subsonic lows in action dvd's.

click here for adire's box desins

[ThomasW]

If you have the space I'd use the Qtc 0.577 design.

Why?

It's no big deal to raise the 'Q' of a system, it's fundamentally impossible to lower the 'Q'.

Use of EQ (something IMO all subs need) raises the 'Q', so why not start off with a lower 'Q' to begin with?

[sphynx_000]

I certainly have room for a larger box,

Adire has plans for a .6 design that still has a very reasonable box size. There dosent appear to be much difference between .6 and .557 q unless I am not understanding something?

I am only suggesting .6 q because adire has plans for it. Designing and buliding a larger box with a different alignment would not be a prolem

[sphynx_000]

about how much more output would I have under 25hz if I went ported?

I another reason I wanted to go sealed was to help protect the woofers from ultra low notes during movies... Would I have to be that careful the shivas for ultra-low notes?

[J-Dub]

Wow I havn't seen ashiva in about 2 years!
Can you still get your hands on them?

about how much more output would I have under 25hz if I went ported?

a lot more depending on your design unless you use EQ.

I another reason I wanted to go sealed was to help protect the woofers from ultra low notes during movies... Would I have to be that careful the shivas for ultra-low notes?

Rumble filter.
I made a sub for a friend using the Peerless XXLS a long time ago and I believe the specs are very similar. Dont quote me on that, like I said havnt seen a shiva in a while. Point is, he had a very large living area and liked the bass really loud! Bye Bye peerless! Replaced with a Dayton 12 and It did much better, However, my recommendation for really loud bass would be a Sound splinter Rlp-12 or Rlp15. Good stuff!

Sealed subs are fine and are a great first sub as there is a LOT of forgiveness with them but you can get better responses out of vented designs.

And as for ThomasW I would listen very carefully!
scratch that.. Very, VERY Carefully!
He knows his subs, probably more than anyone in this forum.

[ThomasW]

about how much more output would I have under 25hz if I went ported?

I another reason I wanted to go sealed was to help protect the woofers from ultra low notes during movies... Would I have to be that careful the shivas for ultra-low notes?

Porting provides more output at Fb (how much more is usually room gain dependent) overall porting provides 3dB more efficiency compared to sealed.

Running sealed protects the driver below the Fb. If you go ported you'll need a filter to protect the drivers from things like the single Hz notes in WotW or LotR, or whatever..

[sphynx_000]

If I run pro amps,

-am am leaning towards an ep2500, then I would have no ss filter... That is the one of the reasons why I wanted to go sealed. Is there anyway I could run a ss through my computer?

J-Dub-
-I am going to buy a couple of shivas from ThomasW. He made me a pretty good deal for a pair of them. On my budget, probably the best drivers I could get. The SS drivers look nice, but they are more money than I have to spend at the moment.

-what dayton 12's are you talking about?

[J-Dub]

Sphynx,

The shivas that Thomas is giving you are excellent low distortion drivers. They used to be used in a lot of reference grade applications. A real gem of a find if you ask me. If you are getting two of them there are many options to optimize how much you can get out of them. A sealed version seems the way to go for what you are looking for. I'm sure there are ways to get your computer to do a lot of things but you will need to have an excellent sound card and be assured that whatever software/hardware you are using doesn't distort or color the sound. Most likely any analog media you run through the computer will be converted to digital at somepoint before the amp. There are threads in a different forum on htguide that referr to designated ht computers. You may want to look those up before deciding to go that route. May want to ask Thomas if the feedback destroyer will do what you need. I know it is able to eliminate certain frequencies but I am not sure if it will give you the boost on the lower end for your sealed subs.
I'm posting from my phone so I can't look up the prices of the ep2500 compared to the ep1500 but if there is any significant savings I would get the ep1500 and the feedback destroyer. The 1500 will have more than enough power to drive both shivas past excursion. Don't get me wrong though, with 2 of them you will be very satisfied with their output!
I know there can be complications with 2 seperate subs cancelling eachother out but there are ways of optimizing them as well. You may want to ask Thomas more about that unless you are intending to do some sort of push-push, push-pull, dual driver application, etc. I think the push push will lower a lot of box movement.
Good luck with your project and congrats on scoring some shivas!

[sphynx_000]

The price difference is only about 10-20 dollars. I would just as soon have the extra, extra headroom. (ya never know what the future hold)

I am really have no idea what I want to do for a box. I guess I should have a ss filter for whatever design I choose though. I am still leaning towards sealed, but I have the feeling I would really like the extra output of a ported box. I am definitely open to suggestions.

Does anyone know if the feedback destroyer will function as a SS filter? It has a parametric eq, so could I just choose a frequency and turn the level down as far as it will go?

[ThomasW]

The BFD won't work as a filter at any realistic frequency needed for a sub.

Here's a thought, build one of the Adire ported box designs . It's a piece of cake to close off the port and instantly have a sealed box.

[sphynx_000]

I suppose I can always just build a passive SS filter if I decide I need one. Then I would have the ultimate adjustability.

Is there any advantage or disadvantage to having two boxes, instead of one?

[ThomasW]

I'd go with two, lighter weight, the ability to move and place them independently is IMO an advantage.

[sphynx_000]

ya, that is what I was hoping to hear.

I think its more visual appealing also.

[sphynx_000]

any more opinions on the type of box I should build?



I plan to get it started this weekend, but I still cant decide on a design.

[ThomasW]

If you have a space for a pair build 2 of the Adire 142.5L ported boxes. You can stuff the ports if you want sealed box performance

http://www.acoustic-visions.com/~acoustic/products/subwoofer_drivers/shiva_classic/ventedshiva.pdf

[sphynx_000]

The large ported box really does look the best. I guess the size is holding me back a little bit. Its not that I dont have the room, but I would rather not have such large boxes. Plus the plans look fairly intense with all the bracing, and I would have to buy a subsonic filter and figure something out for the port. (also the plans are for downfiring the woofer, I thought I read the shiva could NOT be downfired?)

So that, and the fact I will be listening to mostly music pushes towards sealed boxes. If I corner-loaded two sealed boxes, is there any chance I would get decent in-room response before an eq? How much room gain could I expect? My room is 12x20ft, but is loosely sealed off from the rest of the basement (large openings, no doors)

[ThomasW]

Adire probably wouldn't show the Shiva down-firing in all their plans were that orientation an issue.

Build one of the two smaller ported versions if size is a problem

[sphynx_000]

so you would defiantly recommend a ported box for my application?

[ThomasW]

I'm not sure how many more ways I can say this....

Build a ported box, you can always seal off the port (many just stuff the port with a nerf football or section of closed cell foam) and presto, an instant sealed box sub.