4th order bandpass enclosure (fi Q 12")

[lyons238 0]

I have a 12" fi Q that is fully loaded, except there is no extra spider option, and no high qts option. I also have a Sundown SCV-2000d, big 3, XS Power d3400, and an XS Power XP950 in the trunk for power. I figure after all losses/drops I should be getting around 1700w rms of clean power to the sub. For mide I have 2x 6.5" Sundown Neo Pro V2's and some Image Dynamics CTX65SC's for components up front. Hopefully having some dedicated mid bass drivers will work well with a bandpass enclosure, so that I can tune that to hit the low notes and roll off right into where the Neo Pro's will take over. Lastly, It is being installed in a 2013 Subaru WRX.

After some deliberation I think I have landed on a 4th order bandpass enclosure that is vented into the car cabin through the rear deck to maximize SPL, while retaining some good SQ in my car. However I have some questions before I move forward.


1. Will a 4th order bandpass enclosure that is vented through through the rear deck provide more SPL than a simple ported enclosure with the rear seats blocking? Does a 4th order bandpass enclosure provide more SPL without factoring in the loss from the rear seats?

2. What ratio should I use for this sub? I was thinking 2:1. 1.15 net cuft sealed : 2.3 net cuft ported. This is within the manufacturers recommended sealed/ported volume. With a bandpass box, are the manufacturer's recommended volume specs the way to go?

3. What should I tune it to? Also, what is the roll off amount per octave with a 4th order bandpass? Does volume, port area, etc affect this? I would like for this setup to be somewhat SQ oriented but to also maximize SPL with my given gear. I like to get low 25-30hz but also want it to be able to hit the higher notes.

4. Will a 6" aero port be effective in this application? How much port area per cuft is recommended for a bandpass enclosure, is it the normal 12-16 sqin/cuft or is it more like 14-20 sq in/cuft? I believe a 6" aeroport has 28.26 sqin of port area per cuft. Is that enough port area? It comes out to only 12.3 sq in per cuft, but shouldn't that be enough considering its an aeroport, or should I find a way to make an 8" aeroport? Am I calculating that correctly? Is length not considered when determining port area?

5. How do I calculate the port displacement to get the proper net volume of the ported chamber? In order to vent through the rear deck the aero port will stick out of the box. In order to calculate tuning and net volume, how would I figure out the volume of just the port that is inside the box, including the flare? Also, wouldn't that be contradicting because in order to figure out port length and tuning I need to know the amount of volume for that chamber, but I won't know that until I figure out the port area that is inside the box?

6. Will the non qts fi Q be best fit for this enclosure or is the qts option better?

7. Should I mount the sub with the basket in the ported chamber to reduce heat/coil issues? Also, would I need to reverse the wiring when mounting like this or is that only needed when your running multiple subs mounted opposite ways in the same sealed enclosure?

8. Will 1700w rms be too much? Does a 4th order bandpass reduce power handling or will it be similar to a ported enclosure?


Any help is greatly appreciated as I want to make sure that I get this enclosure perfect for my application. Thanks!

Edited February 3, 2015 by lyons238

[95Honda 486]

I would study up on algebra a little for your area calculations.  I would also do some reading on a 4th order bandpass.  Your situation could be an appropriate situation for one, but you really need to do your homework and/or get someone who knows what they are doing (the "ratio" and the manufacturer suggested sealed and vented sizes have NOTHING at all to do with a bandpass) to help design/build your enclosure.

[///M5 2,833]

I figure after all losses/drops I should be getting around 1700w rms of clean power to the sub. For mide I have 2x 6.5" Sundown Neo Pro V2's and some Image Dynamics CTX65SC's for components up front. Hopefully having some dedicated mid bass drivers will work well with a bandpass enclosure, so that I can tune that to hit the low notes and roll off right into where the Neo Pro's will take over. Lastly, It is being installed in a 2013 Subaru WRX.

That sounds like a hot mess of crap to me. Nothing listed goes well together, not even close. Should start with your goals and space. Wherever else you've been reading has you very confused.

1. Will a 4th order bandpass enclosure that is vented through through the rear deck provide more SPL than a simple ported enclosure with the rear seats blocking? Does a 4th order bandpass enclosure provide more SPL without factoring in the loss from the rear seats?

That depends. It'll come with a cost though if it does.

2. What ratio should I use for this sub? I was thinking 2:1. 1.15 net cuft sealed : 2.3 net cuft ported. This is within the manufacturers recommended sealed/ported volume. With a bandpass box, are the manufacturer's recommended volume specs the way to go?

No. Forget everything you think you learned wherever you heard ratio. That is an absolute fail and will make the answer to #1 both quieter and shittier sounding.

3. What should I tune it to? Also, what is the roll off amount per octave with a 4th order bandpass? Does volume, port area, etc affect this? I would like for this setup to be somewhat SQ oriented but to also maximize SPL with my given gear. I like to get low 25-30hz but also want it to be able to hit the higher notes.

SQ and SPL are dire opposites. One is playing ONE note as loud as possible the other playing them all equal. You can't compromise. From your description a bandpass sounds like a terrible choice for you so far. This also makes the rest of your questions moot and somewhat off topic.

[lyons238 0]

 

I figure after all losses/drops I should be getting around 1700w rms of clean power to the sub. For mide I have 2x 6.5" Sundown Neo Pro V2's and some Image Dynamics CTX65SC's for components up front. Hopefully having some dedicated mid bass drivers will work well with a bandpass enclosure, so that I can tune that to hit the low notes and roll off right into where the Neo Pro's will take over. Lastly, It is being installed in a 2013 Subaru WRX.

That sounds like a hot mess of crap to me. Nothing listed goes well together, not even close. Should start with your goals and space. Wherever else you've been reading has you very confused.

1. Will a 4th order bandpass enclosure that is vented through through the rear deck provide more SPL than a simple ported enclosure with the rear seats blocking? Does a 4th order bandpass enclosure provide more SPL without factoring in the loss from the rear seats?

That depends. It'll come with a cost though if it does.

2. What ratio should I use for this sub? I was thinking 2:1. 1.15 net cuft sealed : 2.3 net cuft ported. This is within the manufacturers recommended sealed/ported volume. With a bandpass box, are the manufacturer's recommended volume specs the way to go?

No. Forget everything you think you learned wherever you heard ratio. That is an absolute fail and will make the answer to #1 both quieter and shittier sounding.

3. What should I tune it to? Also, what is the roll off amount per octave with a 4th order bandpass? Does volume, port area, etc affect this? I would like for this setup to be somewhat SQ oriented but to also maximize SPL with my given gear. I like to get low 25-30hz but also want it to be able to hit the higher notes.

SQ and SPL are dire opposites. One is playing ONE note as loud as possible the other playing them all equal. You can't compromise. From your description a bandpass sounds like a terrible choice for you so far. This also makes the rest of your questions moot and somewhat off topic.

 

 

I know they are opposites. i def dont want to be a one note wonder but im saying i would like to hit a band of notes 30-60hz as hard as possible. does a bandpass still sound like a bad idea? really i just wanted to get louder and figured a blow through bandpass would help me do that.

 

but if you think a simple ported enclosure will do pretty much as well in the SPL department than ill just do that. also im still thinking my sub is more suited for a ported enclosure with an ebp of 87 and a qts of .371, what do you think?

 

Also whats so bad about my gear? i realise the neo pros in the rear wont give me the most accurate staging but i figured they'd help me get some mid bass punch/warmth. but i thought the fi q and ID CTX's were a pretty good fit.

[///M5 2,833]

The ONLY benefit of a bandpass for your desires is that it is ported into the cabin. For everything else it will add nothing over a standard ported enclosure. In all likelihood the execution of the bandpass willactually cause it to be significantly worse. The whole ratio born BP on other sites is the biggest crock of shit in audio atm.

The Neo Pro's are not midbasses, they suck at that. They'll do nothing in the rear. Adding more drivers is not a real solution.

BTW, for your goals I'd recommend a different sub than the Q as well. SQ is FAR from one of your concerns.

[lyons238 0]

The ONLY benefit of a bandpass for your desires is that it is ported into the cabin. For everything else it will add nothing over a standard ported enclosure. In all likelihood the execution of the bandpass willactually cause it to be significantly worse. The whole ratio born BP on other sites is the biggest crock of shit in audio atm.

The Neo Pro's are not midbasses, they suck at that. They'll do nothing in the rear. Adding more drivers is not a real solution.

BTW, for your goals I'd recommend a different sub than the Q as well. SQ is FAR from one of your concerns.

That's weird because the neo Pro's are advertised as mid bass drivers obviously the 6.5s won't be anything crazy but it should help for some fill.

And why is SQ far from my concerns? I already have the Q so I will be rocking it. It seems your perspective is seriously negative. I'm trying to work best with what I have hear and most seem to think my gear will be okay. I'm just trying to get the install right now...

[///M5 2,833]

You like the term SQ but all of you requests are focused in a completely different direction.

Advertised as mid-bass and being a mid-bass are extremely different things. I see no place for them in car audio period, but even worse from a mid-bass perspective.

The difficulty you have is that you've been misled a ton throughout your purchase decisions, then you pop on here asking about installing what you have only to find out what you've bought isn't geared towards your needs. Hard pill to swallow I understand, but I'm just the messenger. The only way to get the install "right" will be to sell some of it and buy something else.

As for the negative aspect. Search for Bandpass enclosure advice on this board and read the threads. Gets a bit sickening to always see all of these misled people chasing something that is counter to what they should be doing. Most of the time they don't deal with the criticism as well as you have though as they get defensive and stupidly carry on doing what they had planned. Much healthier to sit back and learn by asking instead of assuming in particular when you've been misled elsewhere.

[lyons238 0]

You like the term SQ but all of you requests are focused in a completely different direction.

Advertised as mid-bass and being a mid-bass are extremely different things. I see no place for them in car audio period, but even worse from a mid-bass perspective.

The difficulty you have is that you've been misled a ton throughout your purchase decisions, then you pop on here asking about installing what you have only to find out what you've bought isn't geared towards your needs. Hard pill to swallow I understand, but I'm just the messenger. The only way to get the install "right" will be to sell some of it and buy something else.

As for the negative aspect. Search for Bandpass enclosure advice on this board and read the threads. Gets a bit sickening to always see all of these misled people chasing something that is counter to what they should be doing. Most of the time they don't deal with the criticism as well as you have though as they get defensive and stupidly carry on doing what they had planned. Much healthier to sit back and learn by asking instead of assuming in particular when you've been misled elsewhere.

Yeah I hear you man I'm just saying I don't think my gear is all that bad like your making it sound. Iv heard people sound pretty good with worse. The reason I chose a more sq oriented sub is because I usually build boxes that maximize the spl with that particular sub so I like to build a bit on the big and low side but while still getting fairly loud and sounding good while doing it. I know you can't have everything but my buddy has a Q and I really liked it which is what made me get one. I'm just trying to maximize it with a 4th order blow through. If I didn't have a sedan is build a ported enclosure and call it a day. But I'm thinking a blow through 4th order if built properly should do the trick better than a ported enclosure sealed off from the back seats.

What do you think? Any help as far as my questions go or actual advise for nailing a nice 4th order wih the non high qts Q? As far as volume, power handling, ratio, and tuning?

[puscifer2 27]

I think you would be much better off with a typical ported enclosure. External port blown through the rear deck or wherever you were planning. Simple solution without all the headache of planning a band pass.

[///M5 2,833]

What do you think? Any help as far as my questions go or actual advise for nailing a nice 4th order wih the non high qts Q? As far as volume, power handling, ratio, and tuning?

First off a standard ported box is a 4th order. Nomenclature wise you will confuse people by calling a BP a 4th order...

And more importantly, you will end up with less output or a very narrow range with a 4th order BP compared to a standard ported enclosure. Whatever confused you into thinking there were benefits is a confused noob that sheep are following. Don't be a sheep.

As for the Neo Pro's, sorry they are crap as midbasses. Model them IB and compare them to nearly any other sort of driver. From 40hz - 200/300Hz where midbasses play is NOT their strong suit. REALLY far from it. There are tons of better pro audio or even better subwoofer solutions to be used as midbass. On top of that, having midbasses in the rear is plain idiotic and pointless. Just have your sub cover that range instead if that is your goal....which of course again means no BP.

[lyons238 0]

I think you would be much better off with a typical ported enclosure. External port blown through the rear deck or wherever you were planning. Simple solution without all the headache of planning a band pass.

 

its hard to take your opinion seriously because you can't just blow a ported enclosure into the cabin with the sub in the trunk. that would totally kill output because the two sources would now be working separately. i think I'm going to stick with a bandpass 4th order blow through but just make sure i get the design right first. 

 

any help on that is appreciated. 

[///M5 2,833]

its hard to take your opinion seriously because you can't just blow a ported enclosure into the cabin with the sub in the trunk.

Sure you can. It will be better than a BP in your installation as well.

that would totally kill output because the two sources would now be working separately.

Rudimentary acoustics is obviously eluding you. Not how a ported box works in particular at the wavelengths in question

i think I'm going to stick with a bandpass 4th order blow through but just make sure i get the design right first. 

 

any help on that is appreciated.

Going to be a major fail. Don't do it. Why are you so stuck on doing something that makes no sense? Where did you collect your misinformation from?

[puscifer2 27]

I think you would be much better off with a typical ported enclosure. External port blown through the rear deck or wherever you were planning. Simple solution without all the headache of planning a band pass.

its hard to take your opinion seriously because you can't just blow a ported enclosure into the cabin with the sub in the trunk. that would totally kill output because the two sources would now be working separately. i think I'm going to stick with a bandpass 4th order blow through but just make sure i get the design right first.

any help on that is appreciated.

Just because it's behind the seat does not make it some soundproof booth. You will not lose nearly as much output as you assume you will.

[lyons238 0]

 

 

I think you would be much better off with a typical ported enclosure. External port blown through the rear deck or wherever you were planning. Simple solution without all the headache of planning a band pass.

its hard to take your opinion seriously because you can't just blow a ported enclosure into the cabin with the sub in the trunk. that would totally kill output because the two sources would now be working separately. i think I'm going to stick with a bandpass 4th order blow through but just make sure i get the design right first.

any help on that is appreciated.

Just because it's behind the seat does not make it some soundproof booth. You will not lose nearly as much output as you assume you will.

 

 

it doesn't matter. if the sub is in the trunk and the port is blowing through there will be phasing issues and a lot of output will be taken. your statement is somewhat correct if you fire both the port and the sub in the trunk you don't lose that much output, but once you separate the two waves its a shit show. the only way you want to port a normal ported enclosure into the cabin is if you fire the sub into the cabin as well.

 

hopefully someone else with some more experience can help me out with my more specific bandpass questions.

[puscifer2 27]

Ok don't listen to me, but one of the most knowledgable people on this site(m5) has basically told you the same thing. Best of luck to you on your build.

[95Honda 486]

The best advice is to model your chosen driver in your chosen alignment.  If you want to do a bandpass, model it.  And by modeling, that means modeling, not picking a "ratio" arbitrarily or random tunings.  Look at the response plots, driver excursion, port velocity and impedance plots.  This will be the #1 source of information to make your decision.  There are a lot of down sides to a bandpass which become apparent when you start modeling, and the vent arrangement is a huge one (note how I said you must look at vent velocity)...  Just be prepared to NOT make design compromises purely for the sake of sticking with a bandpass, that will ultimately kill your results...

[lyons238 0]

Ok don't listen to me, but one of the most knowledgable people on this site(m5) has basically told you the same thing. Best of luck to you on your build.

M5 did not tell me to run a normal ported enclosure through the cabin with the sub facing the trunk. If he did I would laugh and not take any of his advice seriously. Just like I'm doing with yours. Ask anyone yourself if what you told me is a good idea. It's just not and that's why I won't be needing your advice so carry on now I'll take it from those who have some more knowledge/experience than both you and I. Thanks

[lyons238 0]

The best advice is to model your chosen driver in your chosen alignment. If you want to do a bandpass, model it. And by modeling, that means modeling, not picking a "ratio" arbitrarily or random tunings. Look at the response plots, driver excursion, port velocity and impedance plots. This will be the #1 source of information to make your decision. There are a lot of down sides to a bandpass which become apparent when you start modeling, and the vent arrangement is a huge one (note how I said you must look at vent velocity)... Just be prepared to NOT make design compromises purely for the sake of sticking with a bandpass, that will ultimately kill your results...

Ok what software do you recommend I use? Will winisd pro tell me everything I need to know or should I get bass box pro?

I tried to use winisd pro but when I enter in my subs parameters it says "error consistency check failed" and won't let me continue. Any ideas on how to get past that?

Also I have been told an equation for finding the resonant frequency of the sealed portion and then have been told to tune the ported chamber to that, is that true? I have then been told that it's a good idea to build the sealed side of the box first and then actually test the resonant frequency? However it is unlikely that I will be able to test just the sealed portion due to the fact I don't have the proper gear for that and who knows if I have someone build the box for me or I build it myself if they will be willing to test.

If I have someone else build for me because it's winter I need to find someone that has a lot of experience with bandpass boxes in RI.

Any comment on whether or not I can just use modeling/equations to figure out the resonant frequency to tune to or so I have to test?

[///M5 2,833]

You are getting rounding errors in winisd. Ty entering only sd, bl, re, rms, xmax, and pe - then peak at the other parameters to make sure they were calculated ok, you'll see the rounding errors and they'll be really close if you did it right.

And yes, a ported enclosure will sound better and be louder for what you described your needs. The BP won't buy you anything but a headache and probably 2-3 failed enclosures before the execution is what you want.

[lyons238 0]

You are getting rounding errors in winisd. Ty entering only sd, bl, re, rms, xmax, and pe - then peak at the other parameters to make sure they were calculated ok, you'll see the rounding errors and they'll be really close if you did it right.

And yes, a ported enclosure will sound better and be louder for what you described your needs. The BP won't buy you anything but a headache and probably 2-3 failed enclosures before the execution is what you want.

You don't think if I get the design right I will reap the benefits of blowing all the output into the cabin? I really only need 25-65hz to lay decent with a slight roll off on either side of that spectrum.

I'm getting mixed opinions. Some are telling me (including Scott from Fi himself) that a 4th would be the best option as long as I design it well. He said that a 4th order won't be too bad for this sub and the Q is a good option for it despite the numbers leaning toward a ported or 6th order in the real world they can to either way quite nicely. Would you agree with that?

He said that a 4tb order is very doable but a 6th would take many trials and be hard to pull off well as well as put he woofer at risk due to the bad power handling characteristics of a 6th order. He said 4th orders are somewhat forgiving. Would you agree with these two paragraphs I said?

I have been advised to try around the 2.5:1 ratio in order to create the output im looking for while having a pretty wide band of output.

Thanks for all the help. Would anyone be willing to help me with the design process. I'm willing to send some money via PayPal.

[jcarter1885 995]

Do your seats fold down at all or is there a ski-pass section/pull out arm rest for the back seats that leads into the trunk from the cabin? Yes a 4th order bandpass can be an option in a trunk car but i would usually only do one on high powered setups with multiple subs or box taking up the whole trunk not allowing adequate air flow. Another possible reason for a bandpass would be if your cars' gas tank was behind the seats.

With you having a single q I would just recommend building a ported box to manufacturers specs and see how it treats you. If you build the box shouldn't cost more than 50 bucks. Would be the cheapest option. If really wanting to gain output from the trunk, remove rear speakers from back and leave open. You could also try firing the port and sub forward, sealing the trunk from the cabin.

If a 4th order bandpass is your only solution right now then do like 95honda said and do your homework. Dont pick just random ratios, try to understand what you are doing. Just my .02 and good luck

Edited February 5, 2015 by jay-cee

[pmureika 31]

All this band pass stuff sucks. Just my personal opinion.

[lyons238 0]

Do your seats fold down at all or is there a ski-pass section/pull out arm rest for the back seats that leads into the trunk from the cabin? Yes a 4th order bandpass can be an option in a trunk car but i would usually only do one on high powered setups with multiple subs or box taking up the whole trunk not allowing adequate air flow. Another possible reason for a bandpass would be if your cars' gas tank was behind the seats.

With you having a single q I would just recommend building a ported box to manufacturers specs and see how it treats you. If you build the box shouldn't cost more than 50 bucks. Would be the cheapest option. If really wanting to gain output from the trunk, remove rear speakers from back and leave open. You could also try firing the port and sub forward, sealing the trunk from the cabin.

If a 4th order bandpass is your only solution right now then do like 95honda said and do your homework. Dont pick just random ratios, try to understand what you are doing. Just my .02 and good luck

The gas tank is behind the seats and there's a big jump I have to work around. Why does this make a difference for bandpass?

Also my seats fold down but I need to use them and don't want to keep them folded down. Also I will be slightly powering the Q I'll be using my 2000w sundown sno which is rated just over 2000w, so I figure after losses the sub will see 1700w. So wouldn't a bandpass enclosure be a good option for me as long as I design it properly?

Does anyone know a good designer that can help me or a shop/builder in the Rhode Island/Massachusetts area that can help me?

[///M5 2,833]

I'm getting mixed opinions. Some are telling me (including Scott from Fi himself) that a 4th would be the best option as long as I design it well. He said that a 4th order won't be too bad for this sub

That is all in the information you are sharing with different people. Btw, saying something is "not bad" is not a glowing review.

Based on the rest of your posts a 4th order BP won't do anything beneficial for you over a standard box. What we don't understand is why you think it is going to be so beneficial.

[SpeakerBoy 64]

Look, if you want a bandpass, build a bandpass. If you want to know what the experienced members think will work, then the forum is here to help you.

Sounds like you're caught on novelty, so maybe you just need to see for yourself. It's happened to me before, so I get it lol. Bandpasses seemed like the shit for the longest time. But think of it like this, when you intentionally restrict airflow with the sealed side how could you be louder than an equivalent ported box with less math, effort, and practice?

Edited February 5, 2015 by SpeakerBoy