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View Full Version : Need help designing 1st 4th order



kushy_dreams
09-03-2011, 12:27 AM
I'd like to try playing around with a 4th order, I have never built one before.

woofer tsp:

Fs: 25hz
Re: 4.06ohms
Qms: 7.04
Qes: .49
Qts: .46
Vas: 114 L
Mms: 143g
Sd: 520 sq/cm
Xmax: 10.5mm

I have played around with win isd and 1.5sealed/1.5 ported tuned to 48-50hz gives me a decent response curve (27/28hz - 77/78hz at -3db)

I want something that will get louder than the ported box I did in the past for this woofer. Ported was 2.07 cu/ft tuned to 35hz with 1 4in pvc pipe port.

I'm not sure if I'm looking for something that will play music or just get loud.

I'd like to use pvc for the ports, I have 17in of 3in pvc and about 5ft of 4inch. I'm not sure if I should use 2 3in or 4in ports.

It will most likely go in the trunk of Ford Contour and will be wired to an amp thats rated for 534wrms.

My car peaks around 42hz all sealed up and 57hz with the passenger door open.

Wanna give me some recommendations for music and/or spl?

I would also be open to doing a t line if one can be adapted to fit my speaker. I don't have enough confidence in my build skills to try a folded horn.

Jroo
09-03-2011, 05:34 PM
Your subs seem close to what I am going to use. I ended up with a 4th order very close to yours. I had a guy talk to me about a tline, but the box was huge. I think he was tuning to my Fs, which are close to yours.

kushy_dreams
09-03-2011, 08:43 PM
What kind of sub did you use? Size isnt an issue for me, so a t line could work but idk how to adapt a t line to this sub because from what I have read you need a sub with qts and qes both under .4. I'm not that far away from that but I just dont know what to do.

kushy_dreams
09-06-2011, 02:48 AM
bump

Flastrongman
09-06-2011, 04:54 AM
I'd try 1.25 sealed/ 2.5 ported@50hz, 3 4" ports if you want to go with pvc.

kushy_dreams
09-06-2011, 01:59 PM
What would the larger ported chamber do? I heard it was best to stick to a 1:1 ratio.

SicAudio
09-06-2011, 02:14 PM
1:1 who the hell said that? every sub is dif....their is no steadfast rule on it...most ratios are closer to 2:1...not to say 1:1 doesn't work...

last 1 we did just recently ( 3 people helping out plus input from several others including John Hone...)

was 6cf sealed ( fer teh LOWZ...) and 10 ported with 100^2 of port..tuned at 47hz for 2 15" OA subs...

all depends entirely if ya wanna crush the mic or pound the ground...


and tline tuning can be changed :fyi: ....

kushy_dreams
09-06-2011, 02:34 PM
Well I guess I'm looking for something that will put up the highest possible numbers. I did a 137 @57hz with a door open in the ported box so I'm hoping to do over a 140. The sub is just a little Boston G1, cost me 10 bucks, I figured it would be fun to play around with.

Is win isd at least correct in predicting the shape of the output curve. I know its off on a lot of other things. I put in 1.25 sealed/2.5 ported at 50 and it gave a peaky curve that was above 7db from 43-57hz and maxing out around 48-49hz. I guess that should work pretty well with my cabin gain.

SicAudio
09-06-2011, 02:58 PM
graphing is accurate yes... and that sounds like a perfect option that you listed....that 7db gain is HUGE...

kushy_dreams
09-06-2011, 03:16 PM
At the peak of the curve the gain is 7.94db

Vossy
09-06-2011, 03:43 PM
IDK 4th orders for crap, but 8db gain seems way too peaky

SicAudio
09-06-2011, 04:00 PM
to crush the mic that peak is ideal imo.. for daily hell no lolz

but he said he wants SPL...

Flastrongman
09-06-2011, 04:33 PM
It will still sound decent on music. By no means SQ but it should peak quite a bit lower in car than what the graph shows.

SicAudio
09-06-2011, 04:36 PM
true... tuning drops in cabin response by a few hz normally. that alone will help smooth it off to be musical.

05fronty
09-06-2011, 04:38 PM
dude pm ram. he designed me a sick 4th order for my sa's

SicAudio
09-06-2011, 04:44 PM
yes Ryan does great work. big fan of his.

I myself prefer doing my own... thats how I learned. ;)

05fronty
09-06-2011, 04:48 PM
yes Ryan does great work. big fan of his.

I myself prefer doing my own... thats how I learned. ;)

most people are better than me at this. i'm ssssstttuuuuppidd when it comes to boxes lol

SicAudio
09-06-2011, 04:56 PM
well good thing for you that so many of us like ya then huh? lolz

Flastrongman
09-06-2011, 05:07 PM
Or just take my free advice and thank me later. It will get you where you want to be.:D

kushy_dreams
09-06-2011, 05:11 PM
yes Ryan does great work. big fan of his.

I myself prefer doing my own... thats how I learned. ;)

Though I do appreciate the designs he does, I kinda prefer to do it on my own so I can learn. Like the title says, its my first 4th order and I was just looking for some advice to nudge me in the right direction.

Someone mentioned that the t line can be tuned differently and not just to fs, I would love to learn more about t lines if anyone cares to share some knowledge.

Whats the best way to be able to remove the speaker in a 4th order? Should I just use some thin strips of wood to create a lip that a removeable panel can sit on?

Flastrongman
09-06-2011, 05:15 PM
yup, I've done that on many occasions. Now I usually just make an entire panel removable. On my current box the entire top is removable which basically make the entire box easy to modify.

05fronty
09-06-2011, 05:16 PM
well good thing for you that so many of us like ya then huh? lolz

fuuuuu lol

wenn_du_weinst
09-06-2011, 05:21 PM
are you sure a 4th order is best for your car?

kushy_dreams
09-06-2011, 05:26 PM
are you sure a 4th order is best for your car?

4th order will be fine for my car, Im looking to get the highest numbers possible.


Thanks for everyones help, I really appreciate all the feedback :suave:

SicAudio
09-06-2011, 05:31 PM
Though I do appreciate the designs he does, I kinda prefer to do it on my own so I can learn. Like the title says, its my first 4th order and I was just looking for some advice to nudge me in the right direction.

Someone mentioned that the t line can be tuned differently and not just to fs, I would love to learn more about t lines if anyone cares to share some knowledge.

Whats the best way to be able to remove the speaker in a 4th order? Should I just use some thin strips of wood to create a lip that a removeable panel can sit on?


since a tline is based on the sd and the speed of sound quartered ( for a 1/4 wave ) you adjust the length to adjust the tuning. typically length is based on the fs but to tune higher that length is shorter and lower is longer etc..

kushy_dreams
09-06-2011, 05:35 PM
Ok, so you would keep the cross sectional area the same and just shorten the length.... makes sense. Now if I was to use a t line for spl, would I still wanna tune fairly high, like 40-50hz? And would it be the same as a regular ported box, where a higher tune yeilds a more limitied bandwidth aka not good on music?

Moble Enclosurs
09-06-2011, 05:36 PM
I figured I can jump in on this. I noticed you are talking about Tlines as well. If you are looking for numbers, do not go with a tline. They can produce great numbers, by all means, but the response is geared mainly towards a broader response curve. Even a simple ported bass reflex design might do well for you, depending on certain parameters that need to be looked at. Im sure the 4th order will do great, even a 6th can be figured for a concentrated freqeuncy range about 3-5Hz band, which some prefer if they are unsure of their vehicles peak resonances.

But overall, if you want to do a 4th, then do it. As far as helping with the actual design, that is not something I can do in a post, lol. It will take a lot of work to get it right. You can get something great with general information, as we are talking about LF response in a small area, but fine figuring the design will do wonders for it. Just adding that in there for thought.

Oh, and Proper tlines do not inherit a tuning frequency, more so a low impedance dip depending on the phase of the enclosures mouth in relation to the driver position, but again I would not recommend a tline for that, so do not worry about that.

Moble Enclosurs
09-06-2011, 05:39 PM
Ok, so you would keep the cross sectional area the same and just shorten the length.... makes sense. Now if I was to use a t line for spl, would I still wanna tune fairly high, like 40-50hz? And would it be the same as a regular ported box, where a higher tune yeilds a more limitied bandwidth aka not good on music?

No, not at all. The higher tuning will actually help with sound quality in most cases, when you consider the transfer function of the vehicles resonances in the response. Though, this can be used for narrow-band response, it is less efficient in that type of design for most setups.

kushy_dreams
09-06-2011, 07:20 PM
Thanks for all the help, I cant give out anymore "thanks" wtf is up with that, you can only thank x amount per thread?

kushy_dreams
09-06-2011, 07:24 PM
but fine figuring the design will do wonders for it. Just adding that in there for thought.

Would this be with a legit box modeling software or building and testing and rebuilding and more testing or what?

wenn_du_weinst
09-06-2011, 07:27 PM
I'm with moble on the tline thing. They have gotten this rumor to them about being the loudest box you can get and that is far from true.
I'm swapping my horn to a tline and hoping to go down in spl and up in sq

Moble Enclosurs
09-06-2011, 07:27 PM
Would this be with a legit box modeling software or building and testing and rebuilding and more testing or what?

This would be with someone who has the knowledge of doing it correctly and not relying on a program to do everything for them. But, like you said, you want to do it yourself, so a program may be your way to go and nothing can beat trial and error as long as you log everything you do and learn from it.

wenn_du_weinst
09-06-2011, 07:30 PM
This would be with someone who has the knowledge of doing it correctly and not relying on a program to do everything for them. But, like you said, you want to do it yourself, so a program may be your way to go and nothing can beat trial and error as long as you log everything you do and learn from it.

programs tend to end up with bullshit results anyway. it's great if your car is the size of a corn field, not so great if you drive an actual car. There are ways to get ''cabin gain'' but it's just a guess. the best way will probably always be the good old test and tune method

Moble Enclosurs
09-06-2011, 07:36 PM
I'm with moble on the tline thing. They have gotten this rumor to them about being the loudest box you can get and that is far from true.
I'm swapping my horn to a tline and hoping to go down in spl and up in sq

it is likely that you will succeed in this goal as Tlines are made for SQ when designed properly, but give a great amount of output as well. Like the horn enclosure, this is mainly due to coupling. The difference is, the horn can be exponentially larger than a tline for that reason. The tline was nominally made for HT with stuffing to limit the ability for HF bands to pass through the line, but allow the LF band to go through it. This seperates the frequency range of the full range driver used to increase sound quality and accuracy of reproduction-simply put. Horns work a little different, but ironically can be calculated the same way for a different purpose, to couple the driver to the environment for high efficiency. The tline was not designed for efficiency, but to allow high efficient drivers to lower distortion in the LF range by seperation as a physical means of crossover effects. This is the basic ideas of each, though much more can be said about them and their other purposes.

Now, that we have been able to incorporate it into car audio, due to the fact that the perception of distortion is very acceptable in the car environment due to resonances that are acceptable, we can use it more efficiently as well in this application, but mainly for LF purposes. HF horns in a car would be crazy, but from multiple propagation paths of low frequencies, we can adjust better to that audibly-its less subjective.

RAM_Designs
09-06-2011, 07:37 PM
dude pm ram. he designed me a sick 4th order for my sa's

I was wondering how that turned out, never heard back from you. :( :crying:

05fronty
09-06-2011, 07:41 PM
I was wondering how that turned out, never heard back from you. :( :crying:

just haven't had time or have been too lazy lol. got the wood and stuff already. now selling my stuff for more powah for the 15's. i promise by christmas it will be done lol

Moble Enclosurs
09-06-2011, 08:04 PM
programs tend to end up with bullshit results anyway. it's great if your car is the size of a corn field, not so great if you drive an actual car. There are ways to get ''cabin gain'' but it's just a guess. the best way will probably always be the good old test and tune method

Programs, yes. Formulas, no. Because no program can account for the effects of cabin gain yet that I am aware of. What I do with my responses are done using individual formulas to make it as accurate as possible. Not perfect, obviously, but optimal. So, crap results from programs, i would agree to that on most of them, but cabin gain being a guess, it does not have to be. It just takes a LONG TIME to figure for it all, and calculating for up to 7 resonances of each path is all we need anyhow. After that, it becomes pretty blob-like with all of the gain responses together, then having to average them all afterward is a LOT easier. I can figure for hundreds of responses for a single vehicle in a matter of hours, but I do have a lot of the acoustical formulas set up in excel to help me speed up the process. And for those who are wondering, its not just getting the length of the modes that make the difference, as modal response is another thing. Like I always tell people that become interested, a LOT of work and time needs to be put into it, and it's not something I believe can be taught so quickly on a forum, but from what I have said so far in this post alone is enough for now :).

Moble Enclosurs
09-06-2011, 08:07 PM
just haven't had time or have been too lazy lol. got the wood and stuff already. now selling my stuff for more powah for the 15's. i promise by christmas it will be done lol

That would be nice to see, as RAM, you seem to do a great job with making the builds look pretty good. :)