Sundown SA12 Ported Box

[Triticum Agricolam]

If you just measure the width and height of the port, that's all I need to calculate port area.

If you want to determine the tuning of the box, probably the easiest way is using sine wave tones. You can get a sine wave tone generator app for your phone for free. You play tones at moderate volume while watching the cone move. Move your tone frequency up and down until you find the point where the cone moves the least and cone movement increases if you change the frequency up or down from there, that point is your tuning frequency.

So the gain control on your amp is not like a throttle pedal, just because you have it set at 3/4 doesn't really mean anything. At that setting you could be putting out 100 watts or you could be clipping or you could be anywhere in between. The function of the gain knob is to match the voltage level coming from your head unit so that when your head unit is putting out its max clean voltage you amp is providing its maximum clean signal at the same time. If you do a search there is lots of info on this site about how to properly set gains, but in short, the only correct way to do it is with something that detects distortion (like a DD-1) or an o-scope.

Nice looking alternator, BTW. You are building a good foundation for your car audio system.

[300blk]

I was afraid of my gains. I just don't have any equipment to properly set them. Doesn't the dd-1 only set the gain for 40hz? Is there a multimeter I could buy that could set them? I have no idea what I was running to it, but it was flexing my steering wheel and my wipers were bouncing hahaha.

[300blk]

before my 1100w alpine showed up i had it on 500w with gain all the way up. So know what 500 rms sounds like. So I know it should be louder than that!

So maybe I am back to square one, in that if I have it in a slightly smaller box, accidentally over powering it won't be too bad on the sub!

[Triticum Agricolam]

I wouldn't worry too much about box size in regard to how much power you are putting to the sub. The reason box size matters is it influences how much cone excursion you get. It takes a BIG change in box size to make much difference in cone excursion when it comes to ported boxes. A 10% or 15% change in box size just won't matter much as far as cone excursion goes. At 2.1 cubes net @ 35 Hz on 1100 watts you won't have any excursion issues as long your your subsonic filter is properly set.

Properly setting your gains is where I'd recommend you focus more of your attention. You are much more likely to fry your subs from sending them a clipped signal than you are hurting them from over excursion. The best thing would be for you to buy a DD-1 or an o-scope. The DD-1 only measures distortion at 40 Hz and 1000 Hz, but that really isn't any kind of limitation. If you don't want to buy anything, the next best thing to do would be to find someone who has one of those tools. Here is a link to the thread that may help you find someone: http://www.stevemeadedesigns.com/board/topic/193176-smd-tool-map-new-november-2014/

If you don't want to buy any tools and you can't find someone, the next best thing is probably to set your gains by ear. I really don't recommend doing it this way, but it is better than nothing, barely. Here is a video on how to do it:

[300blk]

Thanks dude. I will probably just pick up a DD-1 on payday, given their ease of use. Would be a good tool to have.

Seems as though they are out of stock everywhere though. I will definitely try doing it with a 40hz test tone.. atleast maybe get close.

[300blk]

My deck doesn't have a CD player. I can't be the only one with this problem.. haha

I am glad this box will work, in that it wasn't cheap and its very nice, and light as well given the birch. I am going to go measure the port in a little bit.

[bassfreak85]

Just something I threw together on RE Calc.. seems like too much port area.

There really is no such thing as too much port area.

Here are a couple more things to think about. If you are going to be upgrading to a larger amp and higher power handling sub down the road, you might as well build this box to handle your new equipment when you get it. Your SA-12 will be fine in a box intended for an X-12.

If you are currently running 850 watts, you will never hear the difference going up to 1100 watts.

There is such a thing as too much port area just as too little. just like your box has a QTC(damping) so does the port. sometimes there is a fine line between having enough and too much. if you want me to explain i'll get into more detail but i don't wanna start a big mess..

there is no "ideal" figure. it depends on the box(size and tuning frequency) sub(cms qe fs)cabin, power and displacement capabilities in a specific alignment . in your case about 16-20in^2 is enough to not get any noise.

i often recommend more than the minimum typically as much as i can and i like to leave the box as small as i can without killing efficiency and getting the proper F3. a port works like another sub with its own compliance(air mass for a given volume= compliance) and it too resonates, how it resonates depends on its size acoustical resistance etc..

if i had to recommend a box for the SD id do 1.8 tuned to 33 with 25in^2 of port area for a daily install that is flat sounds good and gets loud. if you wanted something more bottom heavy and didn't care about top end,2 tuned to 28 with 25in^2.. the popping you are hearing could be several things. it might be some nasty in the output signal,poorly damped signal or bottoming out. chances are its from clipping and just a bad recording..

[bassfreak85]

I realize how many times this has probably been asked, but I can't find any concrete answers and the only box calc I can get to work is from RE, provided I have a Mac. It is an SA12 Rev 3 rated 750 rms.

I am looking for 1.9 to 2 cubic feet before sub displacement tuned to 32ish hz.

I currently have the sub in 2.25 cubic feet before sub displacement, so 2.11 after sub tuned to 35 hz. It sounds good on about 850 rms, but I am thinking I should go a bit smaller since I am over powering the sub. It is currently wired to 2 ohms on an Alpine mrx-m110.

It is going in the back hatch of my jeep, so I am not limited on dimensions by any means.

If anyone could help me design a box I'd really appreciate it. I even have paypal I wouldn't mind paying a bit for a good design. I cannot do anything extremely complicated as I am limited to skil saw and jig saws.

Thanks in advance! If I can get a design together today I will be building it tonight!

you positive that its actually that size and tune?

[Triticum Agricolam]

There is such a thing as too much port area just as too little. just like your box has a QTC(damping) so does the port. sometimes there is a fine line between having enough and too much. if you want me to explain i'll get into more detail but i don't wanna start a big mess..

there is no "ideal" figure. it depends on the box(size and tuning frequency) sub(cms qe fs)cabin, power and displacement capabilities in a specific alignment . in your case about 16-20in^2 is enough to not get any noise.

Could you please expand on what negative consequences there are of "too much port". The only drawbacks I'm currently aware of are pipe resonance issues with ports that are too long.

[bassfreak85]

There is such a thing as too much port area just as too little. just like your box has a QTC(damping) so does the port. sometimes there is a fine line between having enough and too much. if you want me to explain i'll get into more detail but i don't wanna start a big mess..

there is no "ideal" figure. it depends on the box(size and tuning frequency) sub(cms qe fs)cabin, power and displacement capabilities in a specific alignment . in your case about 16-20in^2 is enough to not get any noise.

Could you please expand on what negative consequences there are of "too much port". The only drawbacks I'm currently aware of are pipe resonance issues with ports that are too long.

The more port area you have the faster it unloads above and below tuning. similar to having too large of a box. when you increase the port area you increase the air volume within that port.

no programs really show this. the only thing they show is the "gain" from the port. increasing port area much like box size will give you and increase in efficiency at tuning but a narrower bandwidth as well.. I'm not going to say 33 is to much for the 12 but its pushing the limits and its just not needed that sub will never displace enough air to create any noise.

think of it like this. when you have 30 in^2 of port area vs 60in^2 of port area say both tuned to 30 hz your effectively DOUBLE the air mass within the port but lowered resistance and damping because it become easier to create a high and low pressure with the same amount of force. the actual volume has changed but the density hasn't.

another example. you have a tire. you fill it wit air until maximum expansion say 20 liters. and for that 20 liters you have 8 PSI for maximum expansion to occur. now you need 32 PSI. the additional pressure is simply compressing the air molecules making them tight and tighter getting closer and closer so it becomes harder and harder to put more in. same with the port. the smaller ports offer more resistance to compression and it naturally controls the cone more. the result is a narrower bandwidth and less output at its resonance..