Need a box Design. I pay you $$.

[528hz 10+ year member]

Let's tune to 28hz. No I'm not going to do 32hz. I want it to respond like a sealed box and have an almost flat reponse.

 

[SPY 5,000+ posts]

I can do it how ever you want, if you want to keep it at 26 that's fine with me, just posting up your options.

 

[maldecido33 10+ year member]

Let's tune to 28hz. No I'm not going to do 32hz. I want it to respond like a sealed box and have an almost flat reponse.

Then why not seal it?

There are many more factors in getting a flat response than just low tuning.

Just get a properly designed sealed box (by proper I mean a box with a Qtc of .707; perfectly flat response). Also, treat the sealed box with some sort various acoustic treatments.

 

[528hz 10+ year member]

The box I have them in now is sealed and is optimal. It responds great, but I want more output. When I had my XXX 12" in a 2.5 cu. tuned @ 32hz it was nice and loud, but there was still some slight group delay that would be hard for most to hear. I could hear it though especially with some D n B.

Spy: let's do the 28hz and may do one aero on each side of the box.

 

[SPY 5,000+ posts]

Well here you go.

If you tune to 28hz you can have the ports on the front, if you go any lower with the tuning you will have to move them to the sides.

Let me now if this is what you want and I will PM you with the details.

 

[528hz 10+ year member]

O.k. Looks good.

PM me the details.

 

[kovemaster559 5,000+ posts]

Not bad

 

[SPY 5,000+ posts]

Not bad

it's a simple design, but I believe that's what he was looking for.

 

[BrianChia 10+ year member]

The box I have them in now is sealed and is optimal. It responds great, but I want more output. When I had my XXX 12" in a 2.5 cu. tuned @ 32hz it was nice and loud, but there was still some slight group delay that would be hard for most to hear. I could hear it though especially with some D n B.

Spy: let's do the 28hz and may do one aero on each side of the box.

I don't think you accounted for in vehicle gain when modeling your flat response. I modeled 3 boxes with 3 RE SE10s approximating for cabin-gain. Yellow is 3.75cf @ 28hz ported, red is 2.0cf sealed, and orange is a 4th order bandpass design.

 

[528hz 10+ year member]

My car peaks at 45 hz.....what does that tell me/you?

 

[BrianChia 10+ year member]

It will still exhibit a gain of approximately 12db/octave beginning from about 50-80hz down, depending on the size of your vehicle. The larger the vehicle the lower the frequency when the transfer function begins to take effect. That means that a ported box that models perfectly flat in an anechoic environment will actually produce a peak at the tuning frequency (as shown above) when used in a car.

A .707 Q sealed box will typically produce a flat response in vehicle a because it tapers off at 12db/octave, matching and compensating for the 12/db boost produced by the transfer function.

 

[528hz 10+ year member]

Well Brain, what do you think? I've been nevous about building a bandpass and I don't even think I would have the room:

36x16x16.5??

 

[BrianChia 10+ year member]

The orange line shows a bandpass box with 2cf in the rear chamber, 1.5 in the front chamber, tuned to 55hz. It should fit in your dimensions. If possible you can increase the rear chamber to 2.5cf and gain a little more bottom end. You won't gain as much output as the ported box but if your goal is a flat response then 4th order will probably get you the closest.