Double check sonosub info

[rhino2]

I hate to post a bunch of repeat info in another forum (I asked this somewhere else and only got one curt response) but you guys over here seem to be 100 percent more helpful than some of the other forums. I would love to be able to model and figure out some of this myself but a bunch of the freeware programs seem to use Excel and I only have Quattro Pro on my computer and can't seem to get the downloads to work. So I will have to rely on your guys' expertise..... if you will indulge me that is. I just don't want to make a mistake so I appreciate if someone could check my plan and help me out. Thanks in advance.

Okay I have most of the stuff lined up. Buttkicker amp,terminals from Madisound, driver gasket and port cover from PE, sono and end caps cut to size I am just waiting on the TC Sounds driver which is en route. And I just need to have someone double check my #'s before I complete the sonosub. I am using a TC Sounds 15 inch driver powered by a buttkicker amp. The tube is 24 inch by 48 inches tall which I think is about 300 L. I am not positive though about my volume calculations.

Question 1. I have looked at a bunch of different designs on this site and others and I am not sure exactly what length to cut my 6 inch port (it will be flared on both ends) I would like to get the tuning down to at least 15 hz. I know the typical range is between 25 to 33 inches but does a longer port lower the tuning or raise it? What length should mine be? Sorry I am a noob.

Question 2. lining the tube. I have seen people line it with insulation, poly-batting from Walmart, egg crate foam, accoustic foam, etc.... Would something like egg crate foam used for mattress pads work? I know I have seen them for about 10 bucks for a twin size.

Question 3. If I swap out the 15 inch driver for a different one down the road does that change the tuning of the sonotube? Or does it effectively remain the same? Let's say I switch from a 2000 to a 3000 or one of their 5400 lines? Or would I need to change the port length for the different driver?
Thanks in advance for all your help!!!
Chad.

[WillyD]

1) Are you using something like PVC or sonotube for your port, or the double-flared port from Thriller Audio?

You want about a 27-28" length, and for the port from ThrillerAudio (if thats what you have) just cut about 2" off one of the 12" tubes. If you're making the port yourself, just cut about a 27" long piece of 6" PVC or 6" Sonotube.

2) Not sure if that would well or not, I suppose it would be ok. Fiberglass is a popular choice and offers the best damping, and polybatting is a popular choice as well.

3) No, the tuning frequency is independent of the driver. The only reason you might want to change the tuning frequency later is if the new driver models slightly better with a lower or higher Fb. In many cases you might would want to just build a new tube for the new driver...

[rhino2]

I am using 6 inch pvc pipe. Now the 27-28 inches you recommend is that including the flares or 28 inches of straight length with a flare on each end? I know flares are supposed to actually increase the overall length but I don't remember by how much...

[WillyD]

straight 28, but the flares (assuming they aren't large) won't add much length....so I'd just use close to a 28" long port.

[Chrisbee]

I have a simple tip for cutting pipes dead square.

Wrap a piece of straight-edged paper around the pipe and align the overlap perfectly at the point where you want to cut the pipe. Now tighten the paper around the pipe and tape it firmly to stop it from sliding along the pipe.

You now have a perfectly square edge to cut to. You can just use the edge of the paper as a cutting line or draw a line along the edge of the paper then remove the paper first.

I have used this tip for pipes up to 24" diameter. For the bigger pipes I used scrap lengths of wallpaper because nothing else was long enough to wrap right round the pipe.

The paper has to be at least 3 x the pipe diameter long to reach right round the pipe and meet its other end. Ideally it wants to be a bit longer to give you an overlap so that you can align the edges perfectly then tape securely.

[johnson]

The end caps are 3 layers thick, making it 2.25". (replace with http)
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