thoughts on my sa-10 enclosure?

[teoulennon 0]

I've decided to try a ported enclosure for my sa-10 just for kicks.

I'm thinking 1.0ft^3 tuned to around 33hz.

I'm not set on 33hz, it's somewhat of a guess as to what may sound good - I'm going for sq more than spl and listen to all genres so I need it to give me the accurate punch of rock as well as the lows in rap.

My box is limited to a size of 8"d x 13h x 33"w

The sub will pretty much be right up against the rear shelf of the car behind the passenger seats in a porsche 911 so I was thinking it would be better to go with a side firing aeroport over a rectangular port.

My box would measure roughly 8"d x 12.5"h x 31"w, making it 1.12ft^3 after sub displacement, this would be subject to change based on the displacement of the aeroport (which I don't know yet).

Using PSP's port calculator, with a 4" aeroport, I would need a port length of 25.8" to tune to 33hz. I'm afraid the sub would interfere with a port this long.

So, am I on the right track here or just way off base?

Can aeroports be configured to be that long?

[altoncustomtech 773]

I took all the info you posted and drew up a quick rendering of what it was you're trying to do. You're right, the port will interfere with the sub, as you should be able to see in the drawing. Now, I put two sub cutouts on it so you could see each end of the port and it's relationship to the cutout.

You should be able to put two 90 degree bends together and turn the port 180 back on itself inside the enclosure and fit the length you need to get your 33hz tune AND clear the sub. I'm drawing that up right now.

Here's a quick drawing of your current scenario.

[altoncustomtech 773]

Here's what it could look like with a the port with two 90's turning back inside the enclosure.

Keep in mind these are really quick and simple drawings. I don't readily have all the dimension info for the aeroports handy, nor do I know for certain the bend radius of any 4" elbows that will fit the aeroport tubes. The purpose is just to show that it may not completely impossible to achieve what you're wanting to do. You will have to do extra measurements and such to be certain.

[teoulennon 0]

Thanks Alton, what a huge help!

It looks like this may get more complicated than I would have liked

Do you have any other suggestions for ports besides using 90 degree bends?

Apparently I could protrude the port from the box a little but only about 3 inches max before getting too close to the side of the car.

Whether this would be enough to clear the woofer in the box I'm not sure.

[Quentin Jarrell 671]

I'd just go with the 90 or rather 180 degree bends. All you need are 2 90's. If you just go with a straight pipe the end of the port will be very close to the sub and cause unloading issues. You always want the end of the port as far away from the sub as possible

[teoulennon 0]

Thanks Quent,

It's good to know I can work with angles, although I would prefer not to.

It was also suggested that I use a 3" aeroport.

I was told that as long as I stayed around rated power for the sa-10 port noise likely wouldn't be a problem.

If I did so, the port would be more like around 14"

Thoughts?

[Quentin Jarrell 671]

even a 4 inch pipe is smaller than recommended per Small, one of the guys speaker parameters are named after. Even though you may not hear "noise" or chuffing from the port there will still be compression that will be hindering output.

[teoulennon 0]

I see. Looks like it's back to doing research calculating port bends.

Any thoughts on the best way/method to get the 180 degree bend?

I can't picture a precision port and pvc elbow getting along well together.

[Quentin Jarrell 671]

for each 90 degree bend you add half the width of the port to the length. since you have two bends you will add a total of 4 inches to your port length.

[teoulennon 0]

I'm not quite sure I understand your explanation. Are you saying to measure the outside length of the 90 degree bends then add 4 inches?

I came across this measurement formula: (outside + inside) / 2

Is this correct?

Any suggestions on what materials to use for the port?

Edited February 5, 2013 by teoulennon

[dbsupra 69]

I'd just go with the 90 or rather 180 degree bends. All you need are 2 90's. If you just go with a straight pipe the end of the port will be very close to the sub and cause unloading issues. You always want the end of the port as far away from the sub as possible

This. I tried doing exactly what you are trying to do. It worked ok at low power but at higher volume even with the port about 6" from the sub I had unloading issues and lost cone control.

I think a passive radiator might work for your application. Plus you can often tune it to different frequencies to find what you like best and displace minimal volume.

I redesigned and it sounded much better. Not everything is a win lol

[teoulennon 0]

Wow, what a box!

A passive radiator was also suggested to me by a buddy, I'll have to look into them.

I'm still not quite sure how or what I would use to make the port/elbows.

Ideas?

[altoncustomtech 773]

Duh, don't know why I didn't think of it sooner. I'm 100% on board with the passive radiator suggestion. Basically all the benefits of a ported enclosure with no port at all.

[teoulennon 0]

Sounds like I should try one.

I've just spent some time looking for more info on them.

I get the basic idea but I can't find any info on how to actually build a box to needed specs or a calculator that can help.

Know of any sites that can help?

Edited February 6, 2013 by teoulennon

[Quentin Jarrell 671]

Sounds like I should try one.

I've just spent some time looking for more info on them.

I get the basic idea but I can't find any info on how to actually build a box to needed specs or a calculator that can help.

Know of any sites that can help?

Sundown offers them

[altoncustomtech 773]

I'm currently working on a PR setup myself. I'll be using a 10" XCON with a pair of matching 10" passive radiators. A few notes I've learned in the process of getting ready to do the setup. Passive radiators are tuned like a ported enclosure by adding or removing weights to the back of the cone. They offer the great low end extension of ported enclosure without the problems that can be associated like port noise or compression. One major drawback is that like a ported enclosure the driver will "unload" below the tuning frequency but will do so much faster with the PR so tuning your SSF (sub sonic filter) is even more important. The cone area of the passive radiator needs to be greater than that of the driver. You've got one 10" SA10 so you'll need at least either a 12" passive radiator or a pair of 10" PR's to get the full benefit of using a PR in the first place. It's not a good idea to mount the PR's facing upward. If your vehicle requires that arrangement then you should reconsider finding a way to port the enclosure. The initial tuning weight of the PR is calculated by taking the PR's Sd (cone area) as the port diameter and calculating the equivalent port length. Then calculate the volume of that port and figure the mass or weight of the air. Passive radiators are a little more complicated to figure for and are a little more expensive (compare the cost of a PR to a port tube) but are a great solution to utilizing a subwoofer in an application that won't allow for a proper ported enclosure or where the port's length is too much trouble to stuff into it.

If you can and decide to use a passive radiator setup, we're here to help. Same as we are with the standard ported enclosure.

[teoulennon 0]

Great, you guys have been a big help!

Seeing as how it's more expensive, slightly more complicated, and I'd also have to squeeze a 12" in the box, I'd really like to save pr as a last resort - porting is tricky enough for this newbie

Do you think it would be possible to make the box have a side-firing slot port like this?

RE audio box calculator - note that I would make the port exit the side, not the bottom as it looks in the pic..

If the port were to be 13" long that would be far enough away from the sub right?

Also, with the slot port being 2", it would avoid compression and make the port area 13 which would be adequate right?

What do you think?

Edited February 6, 2013 by teoulennon

[altoncustomtech 773]

The RE calculator is often times WAY off, and this is definitely one of them. There's no way to fit that port in your max 8x13x33 dimensions you posted in the first post of this thread, let alone 8x13.5x29. The calculator doesn't calculate many things right, nor does it account for the displacement of the sub. 13sqin of port area isn't a great amount of port area, it's about the same as a 4" aeroport but without the flares to help reduce port noise.

[teoulennon 0]

damn, I thought for sure I had solved all the world's problems with my brilliant design

I guess it's time to experiment with a 4" port.

If I can't get it to work I'll just have to go with a passive radiator.

Thanks for the help guys, I'll be back with results soon enough!

[altoncustomtech 773]

If you have 13" depth available like you first mentioned then you wouldn't have to squeeze the 12" PR in, it will fit easily enough. Parts Express has a 12" Dayton Audio PR available for $34 which isn't too shabby, though I'm not sure how good those are as I have absolutely no experience with those. Getting a little pricier Online Car Stereo has this Boston Acoustics 12" PR for $55 and I can imagine it would perform exactly like you need it to and it can be tuned from the front by removing the dust cap which makes it a fair bit handier than most. Fi doesn't post the prices on the website but they can build you a 12" PR for $90 which is much pricier than you're wanting to go I'm sure. Like was mentioned earlier Sundown makes PR's as well and theirs would match your SA10, but again the prices for those aren't readily available anywhere and you'll have to email Sundown for that.

Considering you can pick up a 4" Aeroport from PartsExpress for $14 the PR's are definitely more expensive however that brings about a common point that we stress here alot, car audio is all about compromise. The automobile is the most horrible, hard to compensate for, difficult to control environment a person can choose to put audio equipment in and even more so to put that equipment in and expect it to reproduce music faithfully and do it well. Even for something as simple as your sub enclosure you'll have to compromise between being stuck with a sealed enclosure and it's limited response and output, taking a chance on port noise and/or loading issues but most likely getting the response and output you're trying to find, or spend all the extra money on a more expensive PR setup that should yield the response you are wanting without the other issues of trying to stuff the port in the enclosure. We can give you all the information we can to help you make an educated decision but ultimately the decision on which compromises you can live with will be yours.