Designing my first SonoSub. Questions. (1 Viewer)

[Chris_Kelly]

Hello fellow DIY'ers
My first posting here on the forums. The forum came highly recommended for matters dealing with sonosubs....hence, my arrival.
To matters at hand.
I'm looking at building my first sub and have decided to make a go at a SonoSub. I've been trying to find and read everything I can regarding this type design.
It seems to me that for this type of sub, the construction parameters should be pretty well nailed down by now. I've been doing a LOT of looking at the Shiva 12" driver (specifically the MKIII). I'm open to suggestions for other drivers tho.
So, I'll now try and tap into the wealth of knowledge contained here in these forums and try to finalize a design for my Sonosub.
What am I wanting?
*Hmm...90% Home Theatre use.
*I'm in a temp. house right now (student) so the sub will most likely be overkill for the room...that's ok though. I want to build the sub with the idea of what kind of room it WILL be in the very near future.
*I would like to have a pretty flat response down to 20Hz.
Accuracy and low distortion are important.
*Size and shape are open to consideration at this point. I just don't want a 6ft tall 24" diameter monster though
*I want to keep it down to just a single 12" driver.
*Ported/Unported - Dunno yet. Leaning towards ported for sizing reasons tho.
Does anyone have anything to say regarding just using the Adire WhitePaper specs for cabinet/port sizing when using the Shiva?
btw...the rather restrictive user name nomenclature is annoying...just had to mention that.
Peace

 

[Ron-P]

Welcome Chris,
I just finished my first Sonosub. Turned out excellent. I was talked into upgrading from the Shiva to the 15" Tempest. My HT room is only 10x12. Let me say, it is not over kill for the room. You might also want to consider going with the Tempest over the Shiva.
I built a 177L sealed sonsub. I used a 20" diameter by 36" long sonotube with .75 MDF innerend caps and .75 plywood endcaps. I ran a pair of 1/2 all-thread rods inside from endcap to endcap allowing for a nice tight seal. Here is a link to a pic of it just before I put the finish on.
http://home.earthlink.net/~peregrine...s/sonosub1.jpg
Peace Out~

 

[Chris_Kelly]

Ron,

Looks great! Without having run the figures thru the software, I'm kinda surprised that the calculations work out to 'only' 177L for a 15" driver. I was actually hoping that I could stick with a 20" diam. tube too.

I'd love to hear what exactly persuaded you to go with the Tempest over the Shiva. I can certainly forsee not having issues with having a truely flat to 20Hz response with a 15" driver tho! YeeHa.

BTW....my current HT room is 16' x 13' with 8.5' ceilings.

 

[Dustin B]

A Shiva is like a SVS PCi, a Tempest is like a SVS Ultra. For the $25 difference it's a no brainer. So then the only issue is size. You could build an Adire Allignment ported Tempest with 20" sonotube. Would be big but not stupid big.

Say 230L gross, tuned to 18hz with a 25" long 6" port. Using 20" sonotube the sub would be 51" tall including 1.5" thick endcaps and 4" legs. Add whatever for a bass plate or longer legs. Is 4-4.5 ft too big? Take some off if the tube ends up being a little larger than 20" which it more than likely will.

 

[Patrick Sun]

If you can handle the larger sized enclosure, a Tempest is the way to go because can take more abuse down low over a Shiva, for me, I think the Tempest is a more robust driver.

 

[Chris_Kelly]

Dustin and Patrick:
Thanks for that info. I created the Tempest driver in WinISD real quick and ran some very quick tests. It doesn't look like the Tempest actually gets me too much lower or flatter response at 20Hz....maybe I'm doing something wrong or is this indeed the case? (I've JUST started using WinISD so it's totally likely I'm doing something wrong here).
So if I understand you correctly Patrick, the 15" just gets me a driver that can handle the low freq. pounding better than the 12", right?
Dustin:
4.5' is starting to get past the limit of what I wanted to keep the height(trying to keep it under 36"). I guess I could just go with a 24" tube and get the height back down. The good thing about the 24" is that it will end up seconding as a ottoman for the couch Just slap some cushioning foam on top and a nice leather cover et voila!
Dustin:
The 230L is 8ft^3. Adire's Application sheet shows 7ft^3 tuned to 20Hz with a 4" ID port @ 16.5" in length.
So...I'm just curious how you were able to get those figures. Did you do your own modeling?
Anyone know if WinISD's vent entry section is ID or OD?
Patrick:
Hey! Your just over in Duluth. I'm in Woodstock. I haven't begun looking yet to see where I'll get the sonotube. HomeDepot or others carry the stuff?
That LifeSaver sonosub is a RIOT! My 4 year old would really get a kick out of that!
Man, this is the most help I've been able to find so far anywhere! Thanks guys! Keep it coming.

 

[Ron-P]

I'd love to hear what exactly persuaded you to go with the Tempest over the Shiva.

Read thru the posts above. Everyone around here talked me into it, glad they did.
Pat and Dustin among others were a great help to me. Heed their advice, they know there tubes
Peace Out~

 

[Patrick Sun]

Chris, you should download Adire's version of LspCAD if you want a better tool for modelling subs using their drivers.
http://www.Adireaudio.com/Files/Adire.zip
For the really heavy bassy DVDs, in my experience, the Tempest will play through them with minimal effort in a calibrated HT environment (it's alway possible to drive subs hard enough to make them cry uncle, of course).
I had to buy a 12 foot section of 24" wide sonotube from "Construction Materials, Inc" (near Jimmy Carter Blvd in between I-85 and Buford Hwy). They are in the phone book. I think it cost me around $100 for the whole thing. But I made 3 Sunosubs out of it.
FYI: The "BassMaker" cover was just made out of construction paper and a bit of time and effort (and add in a few ounces of boredom). I still have it in one of my closets.

 

[Chris_Kelly]

Ron:
I'm definately listening
Newbie question: What does the 'tuned' frequency of the box actually mean? Is higher or lower better in the case of subs? This parameter is one of several I haven't quite understood yet.

 

[Chris_Kelly]

Patrick:
Actually, I have Adire's Lsp running as I type. I just can't figure out how to create new drivers in it tho! It looks very cool but it's useless w/o me being able to enter the driver I want to model.
$100 doh! You happen to be needing any more tube We can split a tube....I was really hoping to not have to spend quite that much on tube (budget constraints).
EDIT:
Ahh...never mind on the driver template. Lsp already has the Tempest.

 

[Dustin B]

Well the actual Adire allignment is 214L tuned to 15.4hz with a pair of flared 3" ports. I'm of the opinion that the larger the port the better. I also try to stick to the rule of thumb which says keep the port length less than 5 times it's diameter. So I assumed the port will displace a little over 10L and a Tempest will be a little under 5L. So take that off 230L and you get 215L.
I switch to a 6" straight port, and to keep the port length reasonable upped the tuning to 18hz. At 16hz it would need to be over 33" long. At 18hz it is 25.5" long.
So it's not really an Adire allignment, but it's closer to that then any of the other allignments.
A 3' tall ottoman You must have really tall furniture :p)

 

[Dustin B]

Adire's version of LspCAD only allows you to model their drivers and they are all pre entered (driver unit -> view parameters -> drop down menu lets you select drivers). To understand what the tuning frequency does just play with LspCAD. Once you figure out how to great a bass reflex box, watch the excursion, port air speed and spl graphs as you vary the tuning frequency. Watch what happens and all will become clear.

 

[Patrick Sun]

Just to add more confusion to the mix:

A sealed sub's response will roll off "gently" as it approaches 20Hz and below.

A tuned box (usually people vary the tuning frequency - Fb - anywhere from 30Hz down to 15Hz) will extend the frequency response of the driver in the box down to the Fb of the box at a good output level, and then under Fb, its output drops like a rock. This is called the EBS (Extended Bass Shelf) design.

The box's port tuning "protects" the driver by providing pressure on the driver down to the Fb which keeps the driver under control, but under Fb, the box doesn't provide the pressure on the driver to a significant degree, and thus, its output drops. The port acts like a resonator to achieve the pressure on the driver inside the box.

Model both a sealed sub and and ported sub, and look at the SPL output to see what I mean in LspCAD.

 

[Chris_Kelly]

Dustin:

I'll be watching.

I entered 230L, with a 25" long 6" port. Graph looks to have an f3 of 20-21Hz but the information section says an f3 of 22.43Hz. Sound right?

Also, either setting the port length or the Res. Freq. changes the other. So, if I set the port tube to 25", it sets the Res. Freq. for me and vice-versa.

I noticed that if I bump the Res. Freq. up to about 19Hz, I get a flatter response down to 20Hz. Interesting.

Also, I can input a min. diamter for the port but not the OD. Does the program automatically enter some value for the thickness of the port tube?

 

[Patrick Sun]

The program is modelling the slug of air in the port, so it only cares about the inner diameter of the port.

 

[Dustin B]

The program does not do any volume displacement accounting for you. You have to enter the net volume. So you should change from 230 to 215 for the design I suggested. But really there is no specific number that is best. Only I'd stay above 160L and I wouldn't go higher than 340L. The min port diameter is the inner diameter and it should be set to 15.2 for a 6" port

The Vb (box volume), Fb, port diameter and port length are all related. Change one and the others will change. The program however assumes you want to keep port diameter and Vb fixed so it will only vary Fb or port length on you.

Also remember a perfectly flat anechoic response to 20hz isn't really desirable as room interaction will increase the output down low. So a slight roll off around 20hz can be a good thing when coupled with a listening room.

 

[Chris_Kelly]

Ok....now how does the 25% polyfill affect my 215L Vb?
...I'm quickly closing in on a design here. Just need to nail down the volume.
Patrick: You look like you're pretty handy with a router ....and I'm not. How bout I bring over a case of your favorite brew and we'll cut some holes for my caps

 

[Dustin B]

I'd just leave the fill and Qa stuff at their default values. With an enclosure that size all you really need to do is line the walls with some polyfill batting and that isn't even really necessary. If you do line it might drop the Fb down a few tenths of a hz that's it.