help on building a subwoofer box for t215d2

[Mario]

the box in total will be bigger then the 2.75 cuft but after the port sub and any bracing you want to add is in it needs to be right around 2.75 cuft and if you are gonna be overpowering the sub slightly smaller then the 2.75 would be better. keep the port area on the lower end of the recomended (9-12" per cuft for round ports if im not mistaken) and you should have a great sounding box.

measurements of my current box are:

height: 35cm

width: 85cm

depth: 50cm

we get about 4,2cu.ft, from which must be subtracted from the volume occupied by the subwoofer and the volume occupied by the round tube, then, assuming that the sub occupies about 5 liters (0,17cu.ft) and the tube occupies about 6.5 liters (0,22cu.ft), the final volume of the box will be approximately 107liters (3,8cu.ft).

so if I have to build a new box for my subwoofer, I'll make it for 2.75 cu.ft to which must be added about 0,38cu.ft more space?

or do I adjust the volume on my new box, based on the power that I shall apply?

In this case, I inform you that I will use one of two amps that I listed at the beginning, ie, lanzar opti2000d or EMPHASER ea1800d, which make up almost the same watts rms.

[Joe X]

Ok Mario I would suggest to making some simple tests on the box you have before getting to build anything, modify anything or exchange amps.

Your box calculations came out very similar to your own calculations, so no issues there. Do you have any braces or a double baffle?

The first test is very simple, just stuff the port in a way that no air passes through it at all, i'ts like creating a sealed box, it will loose output but it will take away the excessive deep bass, see if that sounds the way you expect it or not.

[Mario]

Ok, tests done! But does not satisfy me at all, I would say that is worse. The box I will definitely over, so let me know if I should do it 2.5cu.ft or slightly larger.

I would also like to know. Do you think is better a lanzar opti 2000d or a EMPHASER ea1800d? We'll use it to 1ohm.

[Joe X]

Ok, the Lanzar will deliver maximum power to a 0.5 ohm load managing 1100 W RMS @ 2 ohm while the EMPHASER will deliver 1600W @ 2 ohm BUT they don't tell if that power is RMS power, so I recommend testing them both, a nice fearure of the EMPHASER is the phase control knob.

On the box you say the sealed test sound worse but you don't say why or how (you should have lost low end among the changes), anyways the next test I'd suggest is "loading" the box with anything solid and heavy of known volume (wraped somehow to avoid rattling), this will have the effect of reducing the net volume of the box which in turn change it's performance, tuning will go up also as a consequence, try different amounts of volume to see if you find a sweet spot.

[Mario]

Ok, the Lanzar will deliver maximum power to a 0.5 ohm load managing 1100 W RMS @ 2 ohm while the EMPHASER will deliver 1600W @ 2 ohm BUT they don't tell if that power is RMS power, so I recommend testing them both, a nice fearure of the EMPHASER is the phase control knob.

On the box you say the sealed test sound worse but you don't say why or how (you should have lost low end among the changes), anyways the next test I'd suggest is "loading" the box with anything solid and heavy of known volume (wraped somehow to avoid rattling), this will have the effect of reducing the net volume of the box which in turn change it's performance, tuning will go up also as a consequence, try different amounts of volume to see if you find a sweet spot.

I apologize for the absence.

I have a bit of trouble to do these types of tests (add solids of various sizes inside the box).

Unfortunately my box is constructed so that it can not be changed, also do not know what to use to simulate a solid.

I'd rather redo the box directly.

If anyone can help me understand how to be this box, I would be very grateful.

My needs: Now listen good notes only ultra low ... (although some friends tell me I could do more)

I wish I could listen well, a bit of everything ... and I especially like that the bass is expanded outside of the car.

thx at all

[Joe X]

Well you can put a brick (or some mdf) inside for example, that reduces the net volume and increases your tuning, it helps you understand how a new smaller box will sound. Or you can just take your chances and build a 2.5-2.7 cubes net box.

[Mario]

Well you can put a brick (or some mdf) inside for example, that reduces the net volume and increases your tuning, it helps you understand how a new smaller box will sound. Or you can just take your chances and build a 2.5-2.7 cubes net box.

can i simply simulate the box with a special software?

perhaps, with "BASS BOX" or "PC BASS" or "WIN ISD" I can get an idea of how it will behave the new box.

here comes a problem.

if I decide to use one of the software listed above, I do not know how to interpret the graph of the frequency response.

Can you give me a tip on what to look for in the graph?

I repeat: I want to play a little bit of everything, good, strong, possibly with a lot of pressure.

I apologize if I'm stupid or if I'm bothering you, but I could never without your help.

[Joe X]

Modeling software can help you gain some insight IF they account for cabin effects but you are very unlikely to be able to predict accurately response in a given setup.

The other thing is that even if you get an accurate plot, you still don't know if you will like the outcome, for example sealed enclosures are supposed to give a nearly flat frequency response inside a car, excellent transient response also, so ask around how many people will prefer sealed over other box types and you will find that there are few.

Not to say don't try it, do try it but the best way to go is by tests when you already have an install.

[Mario]

Modeling software can help you gain some insight IF they account for cabin effects but you are very unlikely to be able to predict accurately response in a given setup.

The other thing is that even if you get an accurate plot, you still don't know if you will like the outcome, for example sealed enclosures are supposed to give a nearly flat frequency response inside a car, excellent transient response also, so ask around how many people will prefer sealed over other box types and you will find that there are few.

Not to say don't try it, do try it but the best way to go is by tests when you already have an install.

I understand!

I would like to know one thing.

do you think the tuning frequency is raised or lowered, reducing the volume?

then, to get what I'm looking for, theoretically, I should first reduce the volume automatically, even without changing the tube, the tuning frequency will change. right?

but how can I determine how many liters, and at what frequency should I set agreement, without the above test?

want to tell me that everything is to my personal taste?

[Joe X]

So let's see, if you have external dimensions of 35,85,50 18mm wood and a port 15.4 x 40 then you have an enclosure 3.72 cubes net tuned to 32.1 Hz so say you want to reduce the net volume to 2.7 cubes, 3.72 - 2.7 = 1.02 cubes or 28.9 liters is what you could start loading in case you did the test, so without changing the port you will be getting an enclosure 2.7 cubes net tuned to 37.7Hz that's a drastic change that should be noticeable, if that's too much you could reduce the load and/or change your tuning.