building bandpass for 15, need some advice.

[///M5 2,833]

Mitch knows less than you think, otherwise you'd know more now. Stop defending your illogical behavior.

[pmureika 31]

Do the T/S parameters say this would be a good sub for a 4th order build?

[altoncustomtech 773]

 

 

I'm aware of the potential in sub woofers, and i do attain said potential.

Your posts say that you don't. VERY clearly.

dude, i may not have a technical knowledge such as yourself. as you seem to know alot about this. what I'm wanting to know now is, how do you know what won't work if you've never tried it? is it just because your learnings say different, or because an app says that it won't work? i enjoy learning more when I'm trying different things. i don't understand how let's say a 12 can be any better than what I've gotten out of them. i could almost flip a quarter on the roof of my vw fox with 1 12 in a bandpass in the trunk, I'd say that's pretty good and i don't see how it could be any harder except with more power as that one only had around 400watts goin to it. it was a 600rms sub if i remember correctly.

 

There are a number of fundamentals about speakers, acoustics, and their interaction with the environment they are playing in that tell a person who is well educated in the field whether or not a particular plan is even worth pursuing.  That is the reference that many of the members responding in your post are going by when they say something won't work.  Now, that being said, what sounds good and works satisfactorily for you may not sound good and work satisfactorily for anyone else.  That also doesn't mean that your reference (i.e. the other systems you've listened and compared yours to) were or were not on the level either.  All they're trying to say is that, due to how you've done your builds in the past, there's a VERY strong probability that a proper design for the driver(s) you used would have netted better results.

like I've said, the bottom line is that I've never had a sub box that didn't sound good or hit hard. and I'm not ignorant to the potential of subs, i know when a sub isn't reaching it's full potential. so how could they be better if they are hitting hard and sounding good? by making sure they utilize the exact air space? I'm sure they where though, or else they wouldn't have sounded good, right?

 

Again, sounding good and hitting hard to suit your personal preferences is not an exact measurement and the beat all end all answer, necessarily.  Through your experimenting you may have found the sweet spot for your goals however that sound may not please everyone or through testing with equipment more output could have been gained by building differently.  

granted, i do not know as much as you about the correct spec building method, but i know how to measure a box and say, well that's 4cubes it's too much and back it down. I'm not just blindly throwing pieces of wood in a pile, squirting glue all over it and callin it a box! i do add some screws too!

seriously though, if i make the port longer then it calls for, what's gonna happen exactly with the sound or feel of the bass? am i going to diminish the quality or the feel of it? i assumed it would sustain the notes longer. again this is me experimenting and just because you say it's not good isn't going to stop me from trying.

 

Making the port longer changes the tuning and overall response of the enclosure.  The exact effect it has on the sound can easily be calculated through the use of modeling software or good old hand calculations too.  Without knowing all the specs of the driver, the enclosure, etc. there's no way to guess and know if it will diminish the quality or help it, diminish the output or help it, or anything else blindly like that.  There's nothing wrong with experimenting and testing, but you can't generalize statements about past experiences applied to new builds and assume that everything you've done has been right and that everything to that has been said by the members of this forum to the contrary is wrong.

you can build boxes to spec all day long and assume that something different isn't going to be good. but until you try and see for yourself, it's always just an assumption.

 

That is precisely why modeling software exists.  By modeling the driver in the different enclosures the assumptions are removed from the equation.  However it does take some experience to understand exactly what the modeling tells you which is where doing the modeling coupled with the experimentation like you're doing/have done makes for a good education.

 

 

 

I don't think anyone is saying that EVERYTHING you've done in the past is COMPLETELY wrong.  The way you've done it may not have been the most efficient, and the way you've applied it over the years seems (from many of your responses) to have been misguided, but that doesn't mean anything moving forward from here.  I can speak from experience that when everything you've been taught by others and learned on your own is suddenly found to be either wrong or questionable is a really hard pill to swallow.  Sometimes the tact used by others to try to explain the things that are wrong isn't the best and it comes across aggressive or calloused but that doesn't make it any less correct.

 

Everyone here only wants to help.  If you're not ready to follow their suggestions or really learn about what they're saying that's fine but don't get defensive about it blasting back with information about how what you've done in the past worked and sounded so good to you.  As I mentioned, sounding and working good for your goals is great, but that doesn't mean it absolutely couldn't have sounded better or gotten louder.  Accepting that and opening your mind to really learning all the other possibilities will provide huge gains for your personal advancement in this hobby.

[Thumpper 266]

I have to go pee

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

be right back.......................................

[heftybone 4]

thank you alton. you've clarified the situation completely.

i am willing to learn, but it's hard to when everyone's just saying that was wrong, when it wasn't to me.

i love to experiment and if that means i have to build 10 enclosures before i get it right, then so be it. i don't feel modeling software will deliver what i want as i can't hear it first hand. it just tells me that it's wrong or what have you. i like to experience first hand, and am not afraid to work and rebuild no matter what. i realize that software would make that job easier, and i would only have to tweak the small things in order to achieve my goal. i have observed many designs I've found in posts and what not where people have used software, and others have made suggestions until it was "right". therefore, i feel comfortable in the design that I've settled on, and am now just experimenting with the port length.

i have read the specs for the sub that I'm getting, I've also conversed with someone from fi personally to attain the correct dimensions and specifications for this sub. i don't feel I'm going blindly as i have so much in the past.

pmuerika, I'm not doing a 4th order anymore. i stated that in my second post.

m5, i don't feel I'm defending illogical thinking as I've been happy with the outcome of everything I've built. illogical thinking would be if i did ignore everything that everyone was saying and plead that i am right and you are wrong. I've never said that any of you where wrong, i stated that I've been happy with what I've done, so that's not wrong to me. of course there's always more to learn, and i am taking everything into consideration but that's not gonna stop me from experimenting.

i have the correct port length built into this box @ 32hz, I'm adding another section to it to see how it sounds. so if it's not what i want or like, then I'll remove it and have a box that is exact to specs. the sub is located at the opposite side of the port, firing at a 45° angle. should sound good, i would think as like I've said i seen boxes like this that people where asking about and other more knowledgeable people have replied positively that it was good. and they deaigned theirs with software, and i have correct air space and everything.

so i have learned from this. and again i appreciate everyone's help. especially you aston, you are a very intelligent person, thank you.

[heftybone 4]

I have to go pee

be right back.......................................

aww man, you missed it!

[pmureika 31]

i tried to edit that post, but i couldn't.

but anyway, forget it i changed the design.

That doesn't say you went to ported it just says you changed the design. To what and that software would help a lot.

[heftybone 4]

well i seen many variations of boxes built from software and assessed by the knowledgeable peoples on various websites, so it's kinda like i did use software. sort of. i just took inspiration from their designs and built the volume to my subs specs.

I've used volume and port calculators to find the specs on my box. i will google some software and load my box in to see what i have though. i would like to see what that comes up with. I'm on a phone and my pc is down at the moment, I'm waiting on a new motherboard so i can put it back together. so i hope there's a mobile app.

[///M5 2,833]

i love to experiment and if that means i have to build 10 enclosures before i get it right, then so be it. i don't feel modeling software will deliver what i want as i can't hear it first hand. it just tells me that it's wrong or what have you. i like to experience first hand, and am not afraid to work and rebuild no matter what. i realize that software would make that job easier, and i would only have to tweak the small things in order to achieve my goal. i have observed many designs I've found in posts and what not where people have used software, and others have made suggestions until it was "right". therefore, i feel comfortable in the design that I've settled on, and am now just experimenting with the port length.

You'll learn A LOT more if you model first then build. Then remodel and rebuild. Eventually you won't need the iteration.

[95Honda 486]

I think you are missing where modeling will help you.  It WILL tell you exactly what you will hear.  This is what I mean:

 

Take the last enclosure you built and really liked the way it sounded.  Model it.  Make note of the response.  Now, when you model the next enclosure you target the response of the one you built that sounded so good to you and you will be way ahead of the game.  No constant rebuilding.  There are certain responses people like to hear, with modeling, you can objectively repeat the desired results with little wasted time, money and materials...

[heftybone 4]

i tried to find a mobile modeler, but i don't think they have one. and what's close on the google play store, I'm unsure of so I'm not wastin $1 to find out. i got a woofer box calculator that seemed as though it was pretty concise, as it allowed me to factor cabin space, box/port volume, speaker specs and wattage. but when i started figuring everything my setup was to yield 137db but if i changed my box to their recommended size (which was 1.6cubes), i was to see 120db. so i don't know of the accuracy of that app.

does anyone know of a mobile modeler that will calculate everything? and give me what i need to know.

[///M5 2,833]

If you can't see cone excursion and port velocity it is useless.

[puscifer2 27]

One thing I noticed and haven't seen a response to is, making the port longer will lower tuning. However, you have to compensate for port displacement. Otherwise you defeat the purpose and start choking the sub. So go ahead and change port length, but make sure the enclosure becomes larger to make up for the longer port.

[heftybone 4]

One thing I noticed and haven't seen a response to is, making the port longer will lower tuning. However, you have to compensate for port displacement. Otherwise you defeat the purpose and start choking the sub. So go ahead and change port length, but make sure the enclosure becomes larger to make up for the longer port.

what if i made the outlet of the port smaller? would that help compensate for the increased length and the choking you speak of? the gross volume now is 4.8cubic feet, the port length is 41" right now and i think that's all I'm goin with it (over the 34" that the calculator i used suggested for 32hz). the opening is 4.5"x16.5".

i still can't find a mobile box modeler, so i have to wait on my motherboard for my pc to get a proper one like winisd, but I'll probably have all of this installed by then, because that project is on the back-burner for this one! i will still get it and model it just to see the outcome, because I'm curious.

[puscifer2 27]

If you do reduce it like that it could still be a problem, now you have created chuffing. Again modeling would be perfect for this. As Sean said, you have to account for air speed. Restricting the port still chokes the sub.

[heftybone 4]

If you do reduce it like that it could still be a problem, now you have created chuffing. Again modeling would be perfect for this. As Sean said, you have to account for air speed. Restricting the port still chokes the sub.

yeah, I'm worried about screwin this up now since I've been doin it, not necessarily wrong all these years, just not as right as i could/should be.

like i said before though, if it doesn't produce the sound or hit that i expect a sub of this magnitude should have then i can easily remove the extension and have the right size port. as the calculator on the12volt.com said anyway.

it seems like it's a good calculator, especially compared to others that I've tried, so i feel comfortable with it. i would rather model it before hand, but if it turns out to be completely wrong when i do model it, I'll just build a whole new box. which i may do anyway after i get that software. unfortunately my space is limited to 40lx18wx18h, so I'm somewhat confined there as far as allowing for more cubes. but i can attain around 5cubes, which i have now (4.8).

i figured the little bit of extra length that I've added wouldn't hurt anything, but I'm not certain of course.

oh, i just had an idea, i might know where to get a laptop to borrow, I'll update when i know more. thanks alot though, man. i really appreciate all of this. even if some of my posts seem to be hardheaded, I'm still learning from you guys.

[cobra93 47]

I've been watching this thread for while.

You seem to be starting to listen to suggestions.

 

I will give you an option that may help you that I hasn't been mentioned.

 

You said you don't care if you have to rebuild the enclosure, so build your enclosure, but leave enough room around it to do an external port.

This way you can change the port length without things getting to complicated.

Your net volume will stay the same while your tuning can be changed until you find what you like.

 

If you build the enclosure to the largest net volume you plan to try, you will still be able to reduce the net volume by placing bricks/books in the enclosure until you find the net volume/port length that works for you.

 

Keep in mind the smaller the net volume, with the same port length will raise the tuning freq. of the system.

 

Use some t-nuts and weather stripping where the port bolts to the box so you get a good seal time after time.

 

You can then model each change and you will see what the responce graph looks like and you can shoot for this "curve" if you change the driver to something else in the future.

 

Good luck.

[Jay-C76 333]

I'v built lots of bandpass

a Band Pass box = blown woofer

I have seen more woofers get SMOKED in bandpass enclosures ...... by the time you get that

hot smell or a floating haze in the car it's too late..... she's done.....

I'll stick to my twisted bass reflex designs , at least you can hear when the woofer is being stressed

I would have to agree whole heartedly on this.

Bandpass enclosures put a ton of stress on the cone and if not done correctly will

result in an epic failure.

You see a lot of 4th orders being done nowadays but the science and physics behind them are rarely executed properly.

If you need help modeling enclosures on software all you should've done is ask for that.

There's a few of us on here that have the means and abilities to do so.

But assuming a bandpass would outperform any other design is why you are getting your chain yanked so hard on here.

[heftybone 4]

that's a good idea on the port, wish i would've thought about it before i got this far along in the build. i may not even go with that same sub now, as funds may not permit. so I've halted for now until i know for certain which sub I'm goin with.

also, i wasn't sure if the bandpass was the best idea for that sub, i just figured I'd try it out and see what happened. even if the software is perfect, it's never gonna replicate the sound of the actual box/sub in front of you. so i always want to hear that for myself. and i didn't think anyone would be willing to help me with a modeling software because nobody seemed too willing, and I'm new so i didn't want to be too intrusive.

thanks for the advice though, fellas. i appreciate all the help i can get.

Edited February 3, 2015 by heftybone

[95Honda 486]

I have built a lot of 4th order bandpass enclosures, and a few 6th order bandpass alignments, also...  I used this design successfully in the late 80's early 90's with the drivers available at the time that had low Xmax, big Vas and mid Qts...  They worked well because the bandpass efficiency really helped the low displacement drivers on the bottom end and their large Vas made enclosure design easy due to large volumes that lent to easy vent construction.  I built a lot more of these for home audio than car audio.   Nowadays, drivers have much more linear excursion and efficiency than comparable drivers 20 years ago, so I haven't really seen the advantage.  

 

The last one I built was a pro-audio sub with a pair of Eminence 12" drivers that were perfectly suited for the alignment.  But again, I had specific criteria to do this...  I also had a carefully designed passive crossover that really helped it work right...

 

[95Honda 486]

I was designed to slide right under a stage and fire out towards the crowd...

 

[heftybone 4]

good god man! that's a hell of a rig dude. nice lookin box too. and yeah, i had alot of subs back in the day, but I've not had too many from the future! (which is now, for all you young guys ). they've never really been too high-powered either, 6-700watts is probably the highest I've ever had, and when i consider the electrical systems that where never upgraded, i doubt they ever seen anywhere near that wattage. so of course they would benefit from a bandpass as opposed to the 1000-3000watt rms subs of today. and i ran an electronic crossover with all of my setups. gotta love that bass-boost!

somethin that occured to me today as well, you guys take this car audio thing way seriously, where i never took it so serious. it was always more of a good time, fun type hobby cuz i love bass. and sound quality, but bass more! i never realized that there was so much science and math involved. i love science too. math, not so much. I'm good at it, but i just don't like it. well at least i didn't in school, i can use a calculator now! anyway, cool digs man, and thanks for posting that.

[///M5 2,833]

Too seriously? You are the one posting questions on a forum. Pot, kettle?

As for the "math and shit" it is a very simple science. Really doesn't take much to understand it. If you like the hobby enough to come on a forum perhaps you should read up a bit.

[SpeakerBoy 64]

Too seriously? You are the one posting questions on a forum. Pot, kettle?

As for the "math and shit" it is a very simple science. Really doesn't take much to understand it. If you like the hobby enough to come on a forum perhaps you should read up a bit.

Hearing some of your explanations, along with the other heavyweights on the site can be a bit daunting

It's commonplace to you, while we're left to decipher an answer lol

[heftybone 4]

Too seriously? You are the one posting questions on a forum. Pot, kettle?

As for the "math and shit" it is a very simple science. Really doesn't take much to understand it. If you like the hobby enough to come on a forum perhaps you should read up a bit.

i didn't say you took it too serious. i said you took it way serious. not meaning way TOO serious, just meaning that you took it very serious where i did not. please don't take that the wrong way.