4th order bandpass ported chamber question

[DFW40 10+ year member]

What would be the response difference in two boxes one with a sealed chamber of 1 cube and the ported chamber 1 cube tuned to 55hz and the other box has the same size sealed chamber 1 cube and the ported chamber being .75 cubes and tuned to 55hz? In other words what would be the response difference on two chambers tuned to the same freq but on is larger than the other.

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[Kangaroux 5,000+ posts]

The smaller the ported chamber the less peaky it is thus the less efficient it is. As you get closer to a 1:1 ratio the response becomes less peaky (notice I say less peaky and NOT "flat").

IMO, a 4th isn't worth the time unless you do like a 1:1.5 ratio. You can play around with the tuning to get it so where your response starts to fall off the cabin gain of your vehicle picks it back up, so you can get it very peaky and efficient while still having a flat response because the vehicle's cabin gain evens it out. Also, 55hz is pretty high for a 4th...most people do 45-50. How do you know you want it at 55?

 

[DFW40 10+ year member]

Looking at the spec sheet for an IDQ v.3 and it had a 1:1 ratio on one example tuned to 61hz and it shows and in car response that is pretty close to the ported but not exactly the same. I have a trunk sub and there are too many rattles and the low end is not quite there like it was in my Camry plus it gets much louder with trunk open. I have done all the test with box position etc and even seats folded down helps but I was going to try a 4th order piping thru a 6x9 hole.

 

[pro-rabbit 5,000+ posts]

You will have lots of trial and error to get this build right, I don't see it being right the first time or any where close to be honest.

 

[DFW40 10+ year member]

Built the box .8 sealed and 1.1 ported with a 4 inch aero tuned to 50hz. I did not mess with going thru the 6x9 hole and just firing it back. It sounds very solid hits the lows and has massive punch on the upper end. I could not be happier. FYI I had the IDQ v.3 in a 1.3 cubed box before tuned to 32 hz and have to say in this trunk believe it or not the bandpass sounds better, goes lower and punches higher. I could be crazy but it seems like there is almost no cancellation and all I can attribute it to is the smaller radius of where the sounds is coming out has less cancellation than the sealed 15 I had which dispersed the sound waves wider earlier which maybe had to do with the cancelllation issues. Now when I open the trunk the sound goes down vs up as before. I am sure there will be some group delay issues but so far so good. This is all theory but this 10 is louder and more balanced than the sealed 15 ID v.3 so go figure. I might try a slightly higher tuning because it is easy to do for kicks and giggles. I tried a bandpass a couple of years ago and it did not work out and I could not get it right either way way to high and punchy rumblings around 50 hz but I think I got lucky on this one.

 

[DFW40 10+ year member]

Pro-Rabbit looks like you live in Okc I went to OU and go up to Okc for business often. You build boxes professionally what would you have done differently on the box just curious. Also do the ID specs on their site for bandpass just not work at all or sound terrible the graph shows a relatively even in car response compared with sealed and ported. I changed up the tuning and increased the sizes from the ID sight but it really worked out pretty well so far. I might check out your shop and work next trip up if that is cool. If you can build a box that sounds better I will buy it for sure I am always open to sounding better.