10 cu.ft. @ 33hz (2 HDC3 18's)

[SSS 18734 5,000+ posts]

Here is a slot port if you decide to go that route. 132 sq.in. of port. You could make it bigger, but then you would have to bend it inside the box, which isn't worth doing for an extra 10-20 sq. in. of port.

Specs are approximately 9.5 cubic feet tuned to 35hz. Feel free to cut holes in the brace as necessary. Also, I didn't change the external dimensions, so the double baffle will be exactly the same.

 

[mlstrass 5,000+ posts]

I am doing 35hz no higher

Have you heard a lot of HDC's tuned to 38Hz and thought the lows were missing? I've done a bunch of HDC boxes all tuned to 38Hz and they kill on the lows and have good output.

I've also done them at 35Hz and you'll get exaggerated lows and lose some output, which may be what you want //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

 

[groundpound4200 5,000+ posts]

I have one HDC315 in 3.5 cubes tuned to 32HZ right now and I dont like it very much. Very peaky and only plays the lows. Its what I had laying around and its too cold in MN to finish up my other box.

 

[team3d 10+ year member]

[
Have you heard a lot of HDC's tuned to 38Hz and thought the lows were missing? I've done a bunch of HDC boxes all tuned to 38Hz and they kill on the lows and have good output.

I've also done them at 35Hz and you'll get exaggerated lows and lose some output, which may be what you want /QUOTE]

So how low will they drop at 38hz? How much shorter do I need to make the port in the drawing to get 38 hz?

 

[SSS 18734 5,000+ posts]

Make it 15" long for a 38hz tune.

A better idea is to increase the port to 28 inches wide and make it 20 inches long to get 168 sq.in. of port.

 

[team3d 10+ year member]

Did you mean to say that like that. Cause the 28 inches longx6 inches high equals 168 sq. inches of port. If I do it that way are you saying make it 20 inches long? for what htz?

 

[SSS 18734 5,000+ posts]

Never Mind

 

[team3d 10+ year member]

How did that look on the isd?

 

[SSS 18734 5,000+ posts]

It still looks good on WinISD. A little loss on the lows, but it doesn't roll off until 30hz. Keep in mind the actual curve will look nothing like this when its actually in your car.

ha, that port is actually taking up quite a bit more space than I thought it would. Let me re-do the box real quick so its in between 8 and 9 cubic feet.

 

[team3d 10+ year member]

Well the reason I asked is cause I want the lows but not to worried about the ones below 30htz. Just in the general area so ill go with it at 38. I just ordered the subs so I will get a build log started like thursday or friday

 

[SSS 18734 5,000+ posts]

8.93 cubic feet @ 38.15hz with 156 sq.in. of port

External box dimensions are unchanged from the first box, so use those in conjunction with this one to get all of your cuts.

The predicted WinISD curve, 30hz is still only -5db, but will be much flatter in-car.

 

[team3d 10+ year member]

What do you mean by that?