# Thoughts on my sa-10 box?



## teoulennon (Dec 5, 2012)

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?


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## minbari (Mar 3, 2011)

aero ports just use some kind of PVC pipe with the flared ends. if the kit you buy doesnt go long enough, just get some schedule 20 pipe from lowes. As long as you have calculated the volume of the port and subtracted it from the box volume.

also, with ANY ported box, make sure that you have enough clearance from BOTH internal and external mouths of the port. Good rule of thumb is 1 port diameter of distance from any obstruction.

as for the box sounding good or not, if you will post the speaker specs, I will model it for you and see what it does.


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## teoulennon (Dec 5, 2012)

Thanks for the response minbari.

I've learned that a 4" port will be too long and run into the subwoofer.

It's been suggested to me to use 2 90 degree bends to make it look like this:









I could go with a 3" port around 16" long but I was told that even though it may work and I may not hear "noise" or chuffing from a port that small, there will still be compression that will be hindering output.

Any other ideas for the port?

As for sounding good, here are the sub t/s parameters:

*Sundown SA-10*
*1.0ft^3 ported, tuned to 33hz*

Re: 4.29 ohms
Fs: 35.4 Hz
VAS: 10.13 L
Qes: 0.52
Qms: 5.41
Qts: 0.48
Le: 3.41 mH
BL: 20.40 NA
Mms: 230 g
Sens: 81.0
Xmax: 19mm
RMS: 600 Watts

Feel free to play around w/ tuning to see what would sound best with all genres of music - doing so is beyond my ability right now and I only have a mac so no winisd :blush:


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## minbari (Mar 3, 2011)

I agree on the 3" port. You don't want port compression. That will change tuning and eventually act like sealed box. Not good.

2 90° bends are fine. make sure you calculate your length on the center line.

Will model it in the morning and post results

Sent from my motorola electrify using digital farts


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## teoulennon (Dec 5, 2012)

Great, thanks for the help!

The guy that suggested the 3" port replied to the comment about it causing compression by saying that he had used a 3" aeroport for an sa-12 with no issues and that compression hindering output is nit picking - just stay around the rated power.

I'd really like to give the 3" a shot - it would surely make things easier for a novice like myself.
I figure that with a 3" aeroport only needing to be 17" long to tune to 33hz I may be able to get away with it without having unloading issues.


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## minbari (Mar 3, 2011)

port compression is not "knit picking" lol anybody who says something like that without modeling it, run away, lol.

you will hear chuffing and that distinctive pipe organ sound well before port compression, but it you have such high port velocities that is actually happens, it will sound awful and can damage the sub.

I am assuming 600watts for this sub model, if that is not the case, please let me know as it will affect the outcome.

output is pretty flat out to about 33hz where you about a 2db bump. not horible, but a little eq here will help.

cone excursion is well under control and maxes out at 25 hz. I would suggest using a 20hz sub-sonic to keep that under control

port velocity is not good.

3" round port:

16" long

even with the sub-sonic filter in place it is well over 200ft/s. port compression is a real danger here. without a sub-sonic it is over 225ft/s. either way, it will sound bad.

4" round port:

28.5" long

this is barely good enough. port velocity is about 115 ft/s. you want to keep it under 100ft/s, so this is close. its your call, it may sound fine, but at high volume near the tuning freq it may chuff.

4" x 4" square port:

33.5" long

much better! port velocity down to 90ft/s.


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## teoulennon (Dec 5, 2012)

Wow, thanks for the great info minbari!
You are correct with the 600watts.

Looks like 3" is out of the question and 4" is really cutting it close 

It's been suggested to me to use a passive radiator for this setup, what do you think about that?

Also, any suggestions for tuning to other hz?

Sundown recommends 35hz for this sub but I have a feeling that's more spl based tuning.
I'm looking for sq and what will sound best with all genres of music.


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## minbari (Mar 3, 2011)

tuning between 28-34 seems to be the optimal range. obviously the lower tuning will move your 2db bump lower. it doesnt affect much of anything else. lower tuning does require longer ports, you are gonna be going nuts trying to stuff a 4" port in there the way it is, I wouldnt try to lower it.

passive radiator could be a good option. tuning can be more tricky with a PR. it is certainly more expensive. for a 10" sub you will want to use at least a 12" PR. a good one will cost more than $100. the trick with PRs is that they have a notch in the passband and you have to tune them so that notch is outside your normal audible range.

ESS 689-12P 12" Cast Frame Passive Radiator 264-626

here is the one I modeled in the pic below. PR tuning is about 15hz. that is with 125grams of Pr weight


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## cubdenno (Nov 10, 2007)

The nice thing about passives is you can alter the tune by adding/subtracting weight. 

It's usually recommended to have 1.5 to 2 times the SD of the woofer. So for a ten inch sub, a 12 or 2 10's. I went with 2 15 inchers for my 15. the PR really lets you play with tuning to find YOUR sweet spot.

A 4" aero may cut down on the velocity. I am with Minbari though, go as big as you can or slot port it. Rememer the port can be external as well. Also remember that modeling is at full power which is good to know. Chances are though, your sub will not see that power level due to impedance rise, power compression etc. so you may be able to get away with the smaller round port (4"). Just remember if you ever increase the power with a biger amp, you will run into problems.


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## cubdenno (Nov 10, 2007)

Creative Sound - Product Details

here is the brand in your size I bought. It has enough XMAX to handle your sub.


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## boarder124 (Mar 16, 2006)

Try to find a boston gtr12 passive radiator. They are usually around $50-$75 and seem to be a good value. I wouldn't mess with a 4" port in that small of a box, but that's just me.


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## chad (Jun 30, 2005)

minbari said:


> I agree on the 3" port. You don't want port compression. That will change tuning and eventually act like sealed box. Not good.
> 
> 2 90° bends are fine. make sure you calculate your length on the center line.


I'm assuming you meant 4" if he wants to curl it up.

Sometimes getting an accurate volume on elbows sucks, especially due to (yes there are) variations in elbows.

so buy a length of PVC, 2 90's and 2 caps. Cut to the straight length you need and cap it, don't have to glue it, just get it on there. Fill it with water and measure the volume. (PVC is remarkably waterproof.)

Then build your curved port, make sure it holds the same amount of water as the straight one.... Done.

You will be shocked at how far of "guessing it" will be.


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## teoulennon (Dec 5, 2012)

Thanks guys, seeing as how it's more expensive, a little more complicated, and I'd have to squeeze a 12" in the box too, I'd rather save the passive radiator as a last resort.

Sounds like I'll be trying to make pvc work unless a side-firing port like this will work:









RE audio box calculator - note that I will make the port on the side and not bottom as shown 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?


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## chad (Jun 30, 2005)

Dunno if the RE calc compensates for the fact that the vent is against one wall but remember that the overall volume will be different than that of a "free standing" vent.


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## teoulennon (Dec 5, 2012)

Good point. I was also just told that re's port calculator is notoriously wrong and a rectangular port like the aforementioned is inefficient due to its large surface area to volume ratio.
I don't know if that's correct or not but between the 4" port and pr I should be able to figure something out so I'm not too worried about it.

Great advice on how to make sure the volume of the 90 degree pieces are correct btw, cheers!


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## BoostedOne (Nov 15, 2012)

The 4" port is probably kind of small even... i have a SA 8 tuned to 35hz and my port is just under what the calculators said it should be(3.75x4.25) and i still get port noise at the right note cranked up. But for me it is what it is, it was a feat getting it to fit in my tiny space and out pounds the alternative...

Sent from my MB865 using Tapatalk 2


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## chad (Jun 30, 2005)

did you try just putting a roundover on the vent face with a router? Works wonders sometimes.


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## BoostedOne (Nov 15, 2012)

I should have, but no i didnt. After playing with this stuff for more decades than i care to admit i finally broke down and got my first router and a roundover bit set few weeks ago. I can't wait to start playing with it. I will have to try that sometime. It would be easy to do with duct ports 

Sent from my MB865 using Tapatalk 2


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