Heey everybody,
I'm new to this forum, and i'd like to ask you guys if you see any mistakes in my design!
I've read alot about 6th order bandpass subwoofers, and I like to think I know a lot about them. But i have no experience with this type of subwoofers! So that's why i'm here for a design check
So here it is:
The goal of this subwoofer mainly outside use, sometimes inside with party's, and occasionally in a car.
I'd like to know what you guys think about it!
I'm new to this forum, and i'd like to ask you guys if you see any mistakes in my design!
I've read alot about 6th order bandpass subwoofers, and I like to think I know a lot about them. But i have no experience with this type of subwoofers! So that's why i'm here for a design check
So here it is:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The goal of this subwoofer mainly outside use, sometimes inside with party's, and occasionally in a car.
I'd like to know what you guys think about it!
Last edited:
6th order BP boxes can be fun to build, but they can also be a pain in the **** to get right, and not just due to getting the resonant points correct (which will require trimming those shelf vents accordingly). For example, you need to consider how to get the driver into the box with the smallest removable panel possible, to cut down panel flex. And the other panels have to be properly braced for the same reason. And then will those dimensions allow you to actually get that box into your car? Don't laugh - I got tripped up once by not considering that, the end result being that we had to remove the rear seats of the car in question in order to squeeze the box in from the cabin.
Your design seems to have a bit of wasted space to the right as well. Are you planning to locate an amplifier there or something?
Your design seems to have a bit of wasted space to the right as well. Are you planning to locate an amplifier there or something?
What option did you choose in BassBoxPro?
That software (I never used it before) usually comes with very good acurate data for the enclosures, at least on this type of subs for car (or not) from other members that have been testing their designs in this forum.
The alignments for car (cabin-gain) or home are really different, that's why I'm asking. I think the software asks for that option isn't it?!
Thanks for your reactions
I figured that a slight mis-tuning didn't matter that much... I tried to predict the real length a bit, and both the port can only be tuned lower than this right? That wouldn't be much of a problem, there is some room for error..
Good point about that getting it in! Didn't check that before i designed it But i don't think that would be a problem.. The subwoofer will be going in a Mazda Demio (i know, ugly car) So shouldn't be a problem!
That space in the back is indeed for a amplifier.. A car amplifier actually, because outdoors will really be outdoors with no outlet's near.. So i'll be running it from battery's..
I've simulated this without any room-gain! This is because i'll mostly use it outside...
Bassbox indeed has those options..
I figured that a slight mis-tuning didn't matter that much... I tried to predict the real length a bit, and both the port can only be tuned lower than this right? That wouldn't be much of a problem, there is some room for error..
Good point about that getting it in! Didn't check that before i designed it
But i don't think that would be a problem.. The subwoofer will be going in a Mazda Demio (i know, ugly car) So shouldn't be a problem!That space in the back is indeed for a amplifier.. A car amplifier actually, because outdoors will really be outdoors with no outlet's near.. So i'll be running it from battery's..
I've simulated this without any room-gain! This is because i'll mostly use it outside...
Bassbox indeed has those options..
And you're right about the panel thing, i was thinking about having the entire back panel removable, but that's not a good idea i guess.. And i've got some spare room for bracing! For the small chamber I got about a 1 liter, For the large one i got about 7 Liters. For the large parts i was thinking about glueing 12mm MDF (1/2") to them, the box itself will be made out of 18mm underlayment (3/4").
An externally hosted image should be here but it was not working when we last tested it.
Well, i build it! And it sound good! Loud enough, very boomy tho..
Is there a way to check if the ports are tuned right? I don't have any good microphones or anything, so i can't test it that way...
Anyway, pretty good result for 150 euro's in total (including amp)
The quickest way would be to use a WT3 to generate an impedance curve, but that would require a WT3...
I'm more of an electronics guy than an audio guy really, so i could do that by hand in no time! The thing is tho, in the bass-box pro thing i couldn't really see any indications of the port frequency in the impedance plot.
I expected to see lowest impedance at the tuning frequencies, but it was off by 2Hz at the low frequecy, and 10Hz at the higher one.
Or should i just check if the measured plot peaks at the same frequency's as the simulated plot?
Or something with the phase of the impedance? Those are 0 quite close to FB too in the simulated plot, just not dead-on, and not very close to the lowest impedance points either... They are like, a few Hz of, to the other side of FB. Good thing tho, extremely easy to measure...
I might be talking nonsense now, but i'm just trying to figure out what these impedances mean...
Hi,
The impedance dips to mimima should coincide with
the local excursion minima seen in the excursion plot.
Sucb boxes are very fickle about tuning, you can
model changes around your tuning points. Also
note the modelling is only accurate if driver
TS parameters are accurate. By playing
around with variables in the model you
can do a crude sensitivity analysis, and you
will see that exact tuning will not be easy.
Sort out the front first, noting you won't get that smooth
rolloff in the sim, all sorts of midrange hash is possible
without careful damping of the small chamber and the
large port. An amplifier with a low pass is an idea.
rgds, sreten.
The impedance dips to mimima should coincide with
the local excursion minima seen in the excursion plot.
Sucb boxes are very fickle about tuning, you can
model changes around your tuning points. Also
note the modelling is only accurate if driver
TS parameters are accurate. By playing
around with variables in the model you
can do a crude sensitivity analysis, and you
will see that exact tuning will not be easy.
Sort out the front first, noting you won't get that smooth
rolloff in the sim, all sorts of midrange hash is possible
without careful damping of the small chamber and the
large port. An amplifier with a low pass is an idea.
rgds, sreten.
Hmm, nope, the minima in the excursion plots is exactly the same as the FB's, so not at the same location as the impedance minima's... Is there something wrong with BassBoxPro?
The amplifier has 4th order subsonic and lowpass filters, so that should be allright! do you think is should still dampen the chamber(s) with foam or anything?
Hi,
I guess the two ports could be intereacting throwing the minima off.
However some quick modelling in WinISDPro shows exactly 0 degrees
impedance phase at the two port tunings, and the two impedance
minima are near, the upper looks right and the lower one looks a
little lower than specified tuning. Accuracy of WinISDpro ? dunno ...
I'd still damp the smaller cavity carefully.
rgds, sreten.
Last edited:
The impedance minima occur at the resonance frequencies for the 6th order BP alignment. Being off by 2Hz at the lower resonance frequency isn't too bad (particularly if its lower than the target Fb). However, 10 Hz off at the higher resonance frequency can be pretty bad, particularly if it's LOWER than the target Fb. Is it lower or higher?
They are both lower. (in simulations) Should be 37 and 80, it is 35 and 70... What does it mean? Why is it bad? And how will it affect my sound?
Or do you mean it would be bad if the actual measured impedance plots are off? In that case, i don't know yet...
What should i do with that link? Seems pretty useless to me?
first I noticed about your box is a HUGE back chamber, and a very small front chamber making it look like the woofer is playing directly into a long port
then, I noticed your driver have very high 0.44 Qts ... and low 44liter Vas
Yeah, not that good, right? It's kind of what i had to work with... And i just kept changing the volume and Fb until the box did what i wanted...
It's not the most efficient 6th order, that's certainly true.. But hey, best i could get on my budget... (which was the goal)
I don't know a lot about TH's.. I've tried hornresp, a bit, but to get the same -3dB i need over a 1000Liters.. it says.. I have no idea how to change it... Can i trade efficiency for size? Because if i remember it right, it's very, very efficient...
But this would be a good woofer for a TH?
But this would be a good woofer for a TH?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.