Contour Enthusiasts Group Archives Forums Modifications Audio building box..need help modeling

I am building a small 4th order bandpass box for (2) IDQ12 D2 V.2. I found the box demensions and the predicted in car response curves on the ID tech webpage.

Image Dynamics IDQ12 D2 V.2 tech page

When I model the same set up with WinISD I get a totally different plot. Before I start building can someone verify that this will work (and sound good - high output, low transient responce)?

They are predicting in car response including cabin gain. It won't match what you see in WinISD which is simulating anechoic response.

WinISD recommends a box 5 times as big. When modeled the ID designed box looks terrible.

I just plugged the numbers into WinISD and it recommend a slightly smaller box tuned lower. When I plugged in the box specs from ID, it came out as I suspected. There is a big peak around 80 hz and below that it rolls off pretty quickly below that. With cabin gain normally starting somewhere below 80 hz and rising and rising at 12-18 dB per octave in car, you end up with a somewhat flat response that is shown on the IDQ site.

This woofer was not in WinISD list, so I had to punch in the parameters myself. Did you choose one of the woofers from the list?

I tried to plung them in my self as the ones listed were inaccurate. How do youn think this set up will sound. Right now I have the IDQ's in .88 cuft each.

I personally think that you will be happier just leaving them in a sealed enclosure. They are really designed for a sealed enclosure.

I just bought a 1992 325i - I have heard the trunks are incredibly sealed from the cabin and very well dampened. From what I have heard it is hard to get reasonable output unless you port into the cabin. I hoped to use a 4th order with a 5*5 port through the ski pass through into the cabin.

Ahh...i see. In that case, it might be worth a shot. I don't think it would sound bad, and would actually give you an extra 4 or 5 dB in output in the 50-80 hz range.

Whoa - big gain.

How do you think it will effect my power handling? I wanted to go to 600 watts per sub.

The power handling should be hurt by this alignment. If your subs can handle 600 watts, you should be fine.