First time poster/lurker with LOTS of Q&A

Your box will be fine, and if you want a little more low end bass, then port it. You can use a piece of 3-inch PVC for your port. It will need to be between 11 and 12-inches long. The port will also need to be on the baffle board (the same board the speaker is mounted to).

If you want to see the difference in performance then just graph the same box with a 3-inch port, tuned to around 38 Hz. You can have both graphs up at the same time, just click on "New" and then make the new box. You can change the color of the different graphs by going to plot (I think it was plot). But you will see a big difference in performance.

If you have a little more room, then a slightly larger box with a slot port might be the way to go.

 

The port needs to be on the baffle and yes, you can do a 90-degree turn.

If you have room for a slightly larger box you could try this



This box is 11.5-inches tall by 19.5-inches wide by 15.5inches deep. The port is 1.25-inches wide by 10-inches tall. Its 17.25-inches long.

Something to consider

 

The yellow line is the same graph as yours. The green line is your box ported and tuned to 36 Hz. The light blue line is my box tuned to 38Hz. Notice that the relative gain is slightly higher in my box and it plays just slightly lower all the way to the -3dB point.

The performance for both ported boxes is really close, let us know how it goes

 

The sealed box is smoother, but the reality is that we want a little more bass. So the ported box works better. The graph shows a flat response so a tuning of 36Hz is perfect for that box and woofer combo. If I were building that box for myself, I would tune slightly higher for a little more relative gain. For me 38Hz would be the way to go which means a port length of 10-inches.

I understand room is important for you, so your box is the minumum size (1.17 to 1.25 cu ft) I would recommend. If can get a little more room, do it. Size is the most important factor in a ported box. Stay with the 3-inch round port, it takes up very little space in the box.

Build it, have fun

 

now i am confused. these are the curves i'm getting.

 

well that didn't work. green is 24.96 hz, yellow is 29 hz and red is 37 hz. why do mine have so much gain and fall off so much sooner than yours at higher frequencies?

 

I'm not sure what your asking, so I'll give you some general info about what your looking at and what your looking for. But first lets get something out of the way. There is no reason to tune to 25Hz. Many people believe that tuning to 25Hz means that it can play 25Hz. These people have no clue and are typically backyard audio amatuers, that do not have a basic understanding of speakers and enclosures and how they interact.

Now lets look at my graph, its bigger and I can see it.



First, if we want perfect sound, we want to stay on the 0dB (red) line. But realistically, we want more bass, we want more gain but for now lets look at what we got.

The green line is a JBL woofer tuned to 25Hz. Notice that its starting to roll off before it even reaches 100Hz. Its at the -3dB point by 55Hz. And anything below that -3dB point we can forget about.

Again, for best response we hant to stay on the 0dB line or slightly above it for best sound

Now lets look at the same JBL tune to 40 Hz. Its performance is exceptional at 50Hz and up, in fact its much, much better than the same woofer tune to 25Hz. It doesnt hit the -3dB point until around 40Hz. So lets see, its tune 15Hz higher and it plays 15Hz lower.

This is true of almost all woofers, even though it may not be this extreme.

Remember, Again anything below the -3dB point doesnt matter.

 

sorry my screen capture didn't work out so well. i'll get my son to show me how before i try it again. i understand exactly what you're saying. i'm using winISD. a flat response is exactly what i'm looking for, we are on the same page. all of the tf you posted had that flat response. when i look at different tf on winISD with my subs, even with a tf of 29 hz it gains almost 3 db at 32 hz. with a tf of 37 hz it gains 6 db at 41 hz. my whole mission with winISD was to get that flat response and no or low gain but it's telling me to get that, i have to tune as low as 24.96. i'm not trying to be a pain in the a#& but i want to build this enclosure and i told myself i was going to get 1 program and stick with it. i picked winISD, lol. now i don't know

 

Because of the way we (people) hear things, we actually want a little gain. We don't hear low frequencies well, so we need a slight boost. Typically we want +3dB to +6dB. As long as we have a smooth curve the sound will be very good.

Again I cannot see your graph well, but I like the middle graph the best. Also, your low frequency response tells me that your using a large box. What speaker are you using?

WinISD is a very good program

 

yep, the middle one is tuned at 29 hz. The box that winISD came up with is 3.477 cu. ft. for 2 10 inch alpine swr 1043d. That does seem like a lot of cubes to me. i'm not sure if that's net or gross though

 

Ya, lets reduce the box size to 2.8 cu ft internal size, but no more than 3 cu ft and thats for 2 woofers. Alpine recommends a tuning of around 34 to 35 Hz, which should give us about 4 to 5dB of gain. Your f3, tuned to 35, should be around 27 to 28 Hz. Performance would be awesome. Your actual volume in the box, after taking into account port and speaker (estimating) displacement should be around 2.4 to 2.5 cu ft.

In WINISD if you press Ctrl and D you will get the speaker spec editor and you can input your own specs

This is what I would do, its very close to the Alpine Specs on their website

 

ok, here's what i came up with. vb=2.4, tf=35hz, gain=3.69db@42.26hz, roll off=28.96hz, with a very nice looking curve, it's not as sharp as the curves i was getting. that was a quick run through but now that i know how to use winISD better i think i can tweek it a little more to get an even better curve. thank you so much for your time ranger, me and winISD are friends again. freakin awesome!