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Hopesndreams

6th order bandpass for single 12" XLm2 help!!!

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I know somebody out there has built a 6th order for one of these monsters by now. I've made a design on winISD and it looks to be a great response curve for my music but the biggest problem I'm having is knowing and understanding the port area of the 2 chambers. I've read the pinned file on the FB group for 6th orders saying to keep the rear chamber port size small like 5-8 per cu ft and the front at 28-35 per. But when i finally reach out for help everyone ignores me or 1 person says no i need more on the rear chamber and that's it. I want a wide bandwidth but i don't wanna send it straight to it's death in the first 5 minutes because of excursion problems. For the love of bass can someone please help me on this. I'm not a noob when building boxes but 4th and 6th orders I am because i haven't found the right person to help my brain understand them.

My design is front chamber 60hz (1 cu ft) and rear chamber 33hz (2.5 cu ft)

Edited by Hopesndreams

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I'll try to help you as much as I can.  

First off you need to decide if you want a series-tuned 6th order, or parallel-tuned 6th order.  Parallel-tuned boxes are easier to do IMHO, but series-tuned boxes push all the output out one port and that can be useful depending on your situation.  The two types are VERY different in how they are designed and WinISD ONLY models parallel-tuned boxes.  

As far as the port area per cube suggestions you have come across, those are referring to series-tuned boxes and if that is what you decide to build I would strongly encourage you to NOT make the rear chamber small.  In my experience making the rear chamber port small will get you a little more middle range output, but at the expense of just destroying your low frequency output.  I can show you my testing if you are interested in seeing it.  


"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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2 hours ago, Hopesndreams said:

Sorry i forgot to say I was doing a parallel tuned box and yeah I'll take any help I can get because some of this is a bit confusing

Sounds like you are off to a good start,  just let me know with any specific questions you have. 


"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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Well being parallel tuned what sq in of port should i be shooting for? My original design was a 4" aeroport in each chamber and the redone (to replicate 2 typical vented boxes) was a 4" aero in the front chamber and a 6" in the rear chamber. So the first one would give restriction on the rear chamber as i mentioned from that article and the revised one would undo that. Which of these in theory is what i should go with or should i shoot for different port size altogether?

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You said you have the box modeled in WinISD?  You should be able to see what your front and rear port velocities are in WinISD.  When it comes to port velocity, less is better, but larger ports come with their own design compromises.  30 m/sec is my hard limit, if I can get things closer to 22 m/sec that's a lot better. 


"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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Ok I'll try looking at that again. I noticed mine was on ft/ something and i couldn't get the units changed over to m/sec like the help page example shows. I got frustrated and shut it off, but I'll try again and see what happens. Maybe I just needed a break at that point lol

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Well this is exciting... In order to get that air velocity down around 22 i have to use an 8" aero and damn near 4 ft long! This is not working the way i had hoped at all, i think I'm going to give up on this idea for now because this is not going to work in my space. I'll just build a standard ported box like i did for this subwoofer years ago and try a 6th order later on when I have my SUV back on the road to build in. For layout, accessibility, and performance i just can't do it in my Charger like i had hoped

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Alright so i said screw it, i want this to work even if i have to sacrifice my trunk. I went back in just now and changed over to making slot ports instead of the aeroports and i was able to bring down both velocities front-27 (35sq in of port) and the rear-28 (16.8sq in of port). 

Now if i go to where you mentioned about 22 m/s that would put me 22.4 sq inches on rear chamber and 42 on the front chamber. Which will put my port lengths at 23.5" and 42" roughly. 

What do you think, go for it? I realize it'll be trial and error as many things factor in this but i got the velocity down and i just hope the port sizes are good, this is definitely not what I'm used too lol

 

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