Sonotube Sub Design

[Stoopalini]

Hello! It's been a while since I've posted, but I was hoping I could get some feedback on the Sonosub design I have come up with.

I have a single 12" Shiva and will be pushing it with an Adcom GFA-545 amp. My room is 16' x 24' with a vault along one long wall and one short wall.

The room is not setup idealy, as my entertainment system is against the long wall with the vault. The rear of the room is pretty wide open with a hallway, kitchen, and dining area.

I don't remember how I came up with these dimensions, but here is what I have:

18" diameter sonotube with the internal height being 40.5" and a single 15.35" long 4" flared port. This yields a volume of 160 liters, or 5.65 ft^3.

Will this work? I'm picking up the sonotube tomorrow and will start putting it all together; but would like some verification that my plans are sound. If not, what adjustments should I make?

Thanks to all,

Thomas.

[Andrew Pratt]

well 160 liters should get you some decent bass but IMO a single 4" port even flared is your weak link. I'd rather see you with dual 4"s or a larger single port even if it means putting the port on top.

[Stoopalini]

Really? Thanks Andrew

What's the reasoning behind a bigger port (or wider one)?
I assume it has something to do with the volume and speed of air that can be moved in and out of the encloseure? ....... Am I close?

So if I were to go with 2 - 4" ports, what would their lengths have to be? What other size would be good to go with? would a 5" port be better?

I designed these plans a while ago and used a program to figure it all out; but I don't have that program anymore. (WinISD I think it was called?)

Thanks again,

Thomas.

[Patrick Sun]

Is you went with two 4" ports, you'd need them to be 15.5" for a tune of 23Hz. You can't really use flared ports for an 18" tube because the flare is around 7" wide, and the driver is 12" wide, and that's 19". Two normal 4" ports is the max for an 18" wide sonotube.

If you drive with more than 200W (4 ohm load) you may run into max excursion limits around 30Hz. The group delay will be greater than 15ms under 30Hz. The port airspeed will be over 15m/s under 25hz. 105dB is about the max you could get at 1m with 200W into the sub.




PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

[Stoopalini]

Alright, thanks Pat.

The only sizes of Sonotube I can get are 18" and 24". So I guess I will go with the 24" then.

Does this design look a little better?

24" diameter sonotube with the internal height being 23" and two 15.5" long 4" ports. This will still yield a volume of 160 liters.

Does this look better than my last design?
How can I keep the Max Excursion limit from being reached?

The Adcom amp will push 100w per channel into an 8 Ohm load, and about 150w per channel into a 4 Ohm load.
The Shiva is dual voice coil with 8 Ohm coils, right? So I should get 100w per voice coil when it is all hooked up.

I already have a 4" Flared port that I purchased from Parts Express. If I measure the port tube, it is 12" long. When I put the flares on both ends, it measures 16" long.
So how long is this port? Do you count the flares when you measure it?

Thanks again for your help guys, I appreciate it.

Thomas.

[ThomasW]

Thomas

Definitely go with the 24" tube if possible. In this case "bigger is better"

Also grab a copy of the LspCAD "demo" program off the Adire Audio site. It's preloaded with all their woofers, and it's a far more accurate program than WinISD. Also it allows for modeling flared ports

http://www.adireaudio.com/software.htm

Yes you measure from the outside of the front to the outside of the rear flare to get the total length.

Since your Adcom 545 can't be strapped into mono, just run one voice coil to each channel. You'll have plenty of power. And don't worry you're not going to reach max excursion with that amp.




theAudioWorx
Klone-Audio

[Stoopalini]

Alright, 24" Sonotube it is 8)

I downloaded that program and started playing with it. I dunno if I did this right or not, but with a 160l enclosure, here is what my graph looked like after I was done messing with the port



So I have a single 16" long 4" flared port then. I could always scrap the flared port and get some PVC when I go get the MDF if I need to.

What do you think? Stick with the single 4" flared? or should I change it to something else like 2 - 4" ports, or maybe 1 - 8" port?

I don't know how to interpret all those other charts and graphs that were in the program. Is there something else besides Freq Response and SPL I should be worried about?

Thanks,

Thomas.

[ThomasW]

Hi

You have more than enough port area for a single 12" driver with the 4" flared ports.

In the "bassreflex" box change the "fill" to 20 or 30%. Also put a check mark in the box titled "Sim port nonlinearity"

Next go in the "Driver unit">"Configuration", and put check marks in all three boxes in the "Additional analyis" area

If you want to see what happens with room gain, go to the "Room & Cabinet area, enter the size of your room and the placement of the speaker, etc.

The plot you posted is all you need for designing the box, and getting a pretty good idea as to how it will perform. You can of course use the program to experiment with larger tubes and lower "tunings" for comparison.

Also your room is HUGE, so you may want to consider doing a 24" dia tube containing 2 Shiva's. Then you'll instantly get atleast +3 to 6db more output and you'll be able to put 4 ohm loads on each channel of the amp. This would require a taller tube, but of course it won't occupy any additional floor space.




theAudioWorx
Klone-Audio

[Stoopalini]

I updated the graph with the settings you suggested, and it should be posted.

As far as the port, I have the program configured for a single 4" flared port, not 2.
Earlier in this post, it was recommended that I use either 2 - 4" ports, or one larger port. But the graph shows one port to work ok.
This makes me think there is something I'm not taking into consideration here.

2 Shiva's, huh? Now that would be nice but I don't think I want to spend any additional $$ on this project right now. I know my room is pretty large, but I think I'll stick with the single for now.

For the future, I plan to get a mono amp for the sub (wired for 4 Ohms) and use the Adcom for my mains.
This is my long term plan for eventually going to seperates.

Thanks again guys,

Thomas.

[ThomasW]

Your plot looks fine.

A single 4" port with dual flares will flow plenty of air.

Remember that Adire almost always has "scratch and dent" Shiva's for $90ea. Warranty is "as new"




theAudioWorx
Klone-Audio