4th order design

[05trailblazer]

i would get a designs from one of the enclosure designers mobile enclosures is pretty good at his job ram and pro-rabbit are also good

[nicholasmccabe]

You would need to know the size of the ported chamber and amount of port area to find the tuning.

Sir, the ported section will be 6 or 7 cf. If it is 6cf how do i do the port
If it is 7 cdf how do i do the port. I can go 15 inches tall(thats how tall the armrest hole is, and i can do 6" wide. Thats how wide the hole is. How long do i need to make the port. What do u suggest on the tuning for that car. Its got a decent amount of cabin space, although im not 100% sure of the cars resonant freq. Shall i do a 45 tuning, or 40hz tuning

[nicholasmccabe]

OK guys. Got the shell finished tonight.... Gotta cut the baffles tomorrow, and cut some connecting strtips to connect the 2 boxes together once i get them in the trunnk. A little bracing and we will be ready for a test fit and resin.

How do i post my build pics on here??

[nicholasmccabe]

anyont?? how do i post pics on here?? Also i am doing a square port. It will be 8"x8"... Is that enough port area or do i need to get closer to 100 sq inches of port?? I can do maybe a 10x10, or 9x9 square port

---------- Post added at 07:33 PM ---------- Previous post was at 07:32 PM ----------

anyont?? how do i post pics on here?? Also i am doing a square port. It will be 8"x8"... Is that enough port area or do i need to get closer to 100 sq inches of port?? I can do maybe a 10x10, or 9x9 square port

What are you guys thinking?? Port size gonna be ok for hairtricks? Its gonna blowthrough the rear armrest

[nicholasmccabe]

HOwdo i post pics on here?? I wanna show the build

[nicholasmccabe]

OK guys. I got the sealed chamber built. and i have the ported chamber built. I have to make the port now and i havent gotten any feedback from you guys about how big to make it. 2 fifteens . How much port do i need?? will an 8x8 por be enuff?? or do i need 100sq inches of port?? WHat will happen if i dont have exactly 100 inches of port. Wil 64 inches of port be enuff?? I mean if i dont have 100 will it reduce output?? I want hairticks from a trunk car and i want them NOW!!!!!!!!!!!!

[Moble Enclosurs]

Sorry for not chiming in earlier to help. To be able to post pictures, you have to have them hosted on a website such as imageshack, or photobucket,etc. Then use the "forum" html code from the hosted picture site to paste into your comment.how is the design coming?

[hispls]

Is 50" of port enough for a pair of 15's in 4th order? I use that for a single 12 ported. Sadly it's the best way to get output from a lot of cars, but some subs just aren't suited for that application and it's easy to **** up. Haven't played with 4th order since the 90's so I can't really comment beyond that.

[nicholasmccabe]

@Moble,

Its coming along really well. Waiting to get the subs in from Jacob over at sundown.The sealed cham,ber and ported chamber are complete. I m just gonna resin the corners and do some 45s in the corners. I need some help on the port though. gmonkey told me that 1 need 100-120 sq inches of port, but without alot of cutting i cant fit 1 10x10 square port.

[nicholasmccabe]

I can do some cutting on the rear firewall and be able to get a 10x10 square port to fire through the rear armrest. but the easiest to do will be an 8x8 as the firewall has a hole in it already that will fit an 8x8.

8x8 square port will be 64 square inches of port , corrrect?? using the port calculator onlinr at carstereo, for a 42 hz tuning it will need to be 9 inches long, if i do a 10x10 square port it will have to be 17.92 inches long for a 42 hertz tuning.

Moble,
what sho;ud i tune to for good daily 42 , 44, 46, or 48?? Keep in mind the cadillac has a lot of cabin space so im not real sure what that will affect as far as low end response in car? Please help me out a little on this part

[Moble Enclosurs]

It depends on the vehicles response as well. For instance, the vehicle does in fact, as others have always thought, have a "resonance" that is somewhat peaked, but what happens above and below this frequency may be surprising as well. SO, this vehicle response can affect the anechoic response of the box once it is installed. THIS has to be calculated BEFORE a design can be determined. In some cases, a blow-through is not the answer, regardless of its high efficient coupling abilities.
There is no general response I can give as to what tuning will be good for daily without that information being figured. But, a lot of people in the business will tell you, and this can become true in qutie a few cases, that alower tuning will "flatten" a response because the resonances within the vehicle are higher than the required tuning. So, essentially, a BR design can give you a peak at tuning and at vehicle resonance, and it is about how far apart these peaks are, along with many other factors that determine the final response curve. So, this is the EXACT reason why 33-35Hz tuning has become so popular in car audio. It is based on musicality, but those who do not understand WHY it works, may not see that in some cases, it will not work no matter what you do with tuning. The reason is, tuning does not control the response or passband of a loaded enclosure. Only in a few types of designs is this calculated to affect the response in a audible manner, rather than electrical, which is another concentration of the response.

Here is the thing: and this applies to those who utilize hornresp so much, as I have seen a LOT of people revert to this because they believe of its accuracy but have no idea how to fully achieve it. You can get a flat response on HR, or another program either more (LEAP) compatible, or less(WINISD) compatible with a full acoustic/electric response of an enclosure. BUT getting that response is not all there is to it, neither is tuning. You can have a flat response for a driver from say, 30-75Hz(+/-3dB) anechoically, but that does not mean the output in dB will be consistent. For instance, phase, which has a HUGE effect ont he response, may act as an acoustical filter, and if it is not controlled, though a response may look good, the box will lose output where phase is non-linear.

So, saying that a specific tuning will give you a good daily response is not accurate at all. BUT, saying that most can get a decent response from tuning low, though this is still a gamble, may be acceptable as a response to most of the audio world. Our ears tend to accept sounds more than we recognize, and over time, a terrible response may start to sound ok for some. So, you cannot say a tuning will give a good musical response on its own. BUT, once other factors are known, and controlled, then you will be able to tell what you can do with it: the driver, the box, and the design idea all together.

Regarding port area, this is another factor that is dependant on others, such as noise control, phase, coupling, and compression, so that 8x8 or 10x10 may only be usable for a few frequencies at high power, or all together great, depending on what drivers and enclosure is used with the port. So, on that note, I cannot answer that either, but I can bet that due to the square area for the drivers surface area you are using, that it may not be an acceptable area at high power levels.....but again, no one can verify that without real world application, or calculated mach ratings, etc. The design as a whole has to be done not one step at a time, but all together. This is what separates the good designers from the great ones. If you just concentrate on tuning, then try to make the rest work around it, you will chase your tail in a lot of cases. The same goes with the physics of the design as well. You may find that the optimum compression area may be larger than what you can use, and without knowing the limitation, you cannot further optimize it within the constraints of the space. Things like that. So, I know this is a lot of info, but you cannot talk about tuning effects alone without knowing the effect of other factors in the design. I cannot or will not take a limited space, and fit what I can into it(i.e. those who use walls and clamshells who think they are loud because of some great design work, not knowing that when volume is reduced, compression is increased) without figuring all other variables and knowing not only that it will sound great and loud, but knowing it is all that can be done.

Those who run walls.....that is another story. If you find anyone who run a wall, and cannot perform a hair trick, help them. The concept of decreasing cabin area, and increasing power, excursion, and surface area is very simple in such large applications, that anyone can do it. Really. But take a couple of 8s, or 10s, and get them to give you a 140dB musical output for 1.5 octaves without overpowering them to mechanical distortion levels(below 1-10%), and that takes some work. And Im not talking about a 140dB peak at a specific frequency. Im talking 140 across 1.5 octaves AVERAGE. Not easy. And I say 140 because anything above that become pressure related in the ear, and not intensity based much higher than that.

I hope all of this information helps you a little in knowing what to look for in a design, or what your limitations may be. Sorry it was so long.

[nicholasmccabe]

Is 50" of port enough for a pair of 15's in 4th order? I use that for a single 12 ported. Sadly it's the best way to get output from a lot of cars, but some subs just aren't suited for that application and it's easy to **** up. Haven't played with 4th order since the 90's so I can't really comment beyond that.

What would you estimate for a good port area?? I have newly built box that has 4cf sealed w/4lbs of polyfill, subs inverted, ported section is 8.22 before displacements. -.34 for subs, my port is 136sqinches. like 16.5 tall X 8.5 wide. Its lenght is around 7 inches. WHich brings it to around 52-53 hertz tuning. Now obviously with that high a tuning, its not gonna annialiate the lows, and considering 2 sa 15s in a sealed box that is 3 cf has a FS of around 51-52, so with mine being in a bigger seale enclosure, my resonance should be a little lower than that right?? I need to tune the ported xchamber to the resonant freq of the sealed side to get maximum effeciency and output correct?? Im loving the real world results and how just changing a little thing like an insert that brings theh port area down to 100sqin can drop the overall output down.

Let me know what you thuink

---------- Post added at 03:01 PM ---------- Previous post was at 03:00 PM ----------

It depends on the vehicles response as well. For instance, the vehicle does in fact, as others have always thought, have a "resonance" that is somewhat peaked, but what happens above and below this frequency may be surprising as well. SO, this vehicle response can affect the anechoic response of the box once it is installed. THIS has to be calculated BEFORE a design can be determined. In some cases, a blow-through is not the answer, regardless of its high efficient coupling abilities.
There is no general response I can give as to what tuning will be good for daily without that information being figured. But, a lot of people in the business will tell you, and this can become true in qutie a few cases, that alower tuning will "flatten" a response because the resonances within the vehicle are higher than the required tuning. So, essentially, a BR design can give you a peak at tuning and at vehicle resonance, and it is about how far apart these peaks are, along with many other factors that determine the final response curve. So, this is the EXACT reason why 33-35Hz tuning has become so popular in car audio. It is based on musicality, but those who do not understand WHY it works, may not see that in some cases, it will not work no matter what you do with tuning. The reason is, tuning does not control the response or passband of a loaded enclosure. Only in a few types of designs is this calculated to affect the response in a audible manner, rather than electrical, which is another concentration of the response.

Here is the thing: and this applies to those who utilize hornresp so much, as I have seen a LOT of people revert to this because they believe of its accuracy but have no idea how to fully achieve it. You can get a flat response on HR, or another program either more (LEAP) compatible, or less(WINISD) compatible with a full acoustic/electric response of an enclosure. BUT getting that response is not all there is to it, neither is tuning. You can have a flat response for a driver from say, 30-75Hz(+/-3dB) anechoically, but that does not mean the output in dB will be consistent. For instance, phase, which has a HUGE effect ont he response, may act as an acoustical filter, and if it is not controlled, though a response may look good, the box will lose output where phase is non-linear.

So, saying that a specific tuning will give you a good daily response is not accurate at all. BUT, saying that most can get a decent response from tuning low, though this is still a gamble, may be acceptable as a response to most of the audio world. Our ears tend to accept sounds more than we recognize, and over time, a terrible response may start to sound ok for some. So, you cannot say a tuning will give a good musical response on its own. BUT, once other factors are known, and controlled, then you will be able to tell what you can do with it: the driver, the box, and the design idea all together.

Regarding port area, this is another factor that is dependant on others, such as noise control, phase, coupling, and compression, so that 8x8 or 10x10 may only be usable for a few frequencies at high power, or all together great, depending on what drivers and enclosure is used with the port. So, on that note, I cannot answer that either, but I can bet that due to the square area for the drivers surface area you are using, that it may not be an acceptable area at high power levels.....but again, no one can verify that without real world application, or calculated mach ratings, etc. The design as a whole has to be done not one step at a time, but all together. This is what separates the good designers from the great ones. If you just concentrate on tuning, then try to make the rest work around it, you will chase your tail in a lot of cases. The same goes with the physics of the design as well. You may find that the optimum compression area may be larger than what you can use, and without knowing the limitation, you cannot further optimize it within the constraints of the space. Things like that. So, I know this is a lot of info, but you cannot talk about tuning effects alone without knowing the effect of other factors in the design. I cannot or will not take a limited space, and fit what I can into it(i.e. those who use walls and clamshells who think they are loud because of some great design work, not knowing that when volume is reduced, compression is increased) without figuring all other variables and knowing not only that it will sound great and loud, but knowing it is all that can be done.

Those who run walls.....that is another story. If you find anyone who run a wall, and cannot perform a hair trick, help them. The concept of decreasing cabin area, and increasing power, excursion, and surface area is very simple in such large applications, that anyone can do it. Really. But take a couple of 8s, or 10s, and get them to give you a 140dB musical output for 1.5 octaves without overpowering them to mechanical distortion levels(below 1-10%), and that takes some work. And Im not talking about a 140dB peak at a specific frequency. Im talking 140 across 1.5 octaves AVERAGE. Not easy. And I say 140 because anything above that become pressure related in the ear, and not intensity based much higher than that.

I hope all of this information helps you a little in knowing what to look for in a design, or what your limitations may be. Sorry it was so long.

Off the top of your head, in the most general of terms, what would you guesstimate a good port area for 4 sealed-7.75 ported?? 4th order bandopass

[Moble Enclosurs]

What would you estimate for a good port area?? I have newly built box that has 4cf sealed w/4lbs of polyfill, subs inverted, ported section is 8.22 before displacements. -.34 for subs, my port is 136sqinches. like 16.5 tall X 8.5 wide. Its lenght is around 7 inches. WHich brings it to around 52-53 hertz tuning. Now obviously with that high a tuning, its not gonna annialiate the lows, and considering 2 sa 15s in a sealed box that is 3 cf has a FS of around 51-52, so with mine being in a bigger seale enclosure, my resonance should be a little lower than that right?? I need to tune the ported xchamber to the resonant freq of the sealed side to get maximum effeciency and output correct?? Im loving the real world results and how just changing a little thing like an insert that brings theh port area down to 100sqin can drop the overall output down.

Let me know what you thuink

---------- Post added at 03:01 PM ---------- Previous post was at 03:00 PM ----------



Off the top of your head, in the most general of terms, what would you guesstimate a good port area for 4 sealed-7.75 ported?? 4th order bandopass

For my reply, unfortunately I will not give a guesstimate for anything, especially if it were a 6th or 8th order. But I can give you a good idea of what may work for the subs without regard to space or volume. What subs were they again, and what is your resonance tuning goal (though this is only for calculation at the moment)? I can give you a good tuning for a 4th also for this if interested.
But I cannot go further than that without a design being produced

[DakotaSPL]

you can upload photos from facebook as well, go to pictures, click on picture to make it larger, then right click image and click copy image URL, make sure to not put in a double http

HOwdo i post pics on here?? I wanna show the build

[hispls]

What would you estimate for a good port area?? I have newly built box that has 4cf sealed w/4lbs of polyfill, subs inverted, ported section is 8.22 before displacements. -.34 for subs, my port is 136sqinches. like 16.5 tall X 8.5 wide. Its lenght is around 7 inches. WHich brings it to around 52-53 hertz tuning. Now obviously with that high a tuning, its not gonna annialiate the lows, and considering 2 sa 15s in a sealed box that is 3 cf has a FS of around 51-52, so with mine being in a bigger seale enclosure, my resonance should be a little lower than that right?? I need to tune the ported xchamber to the resonant freq of the sealed side to get maximum effeciency and output correct?? Im loving the real world results and how just changing a little thing like an insert that brings theh port area down to 100sqin can drop the overall output down.

Let me know what you thuink

---------- Post added at 03:01 PM ---------- Previous post was at 03:00 PM ----------



Off the top of your head, in the most general of terms, what would you guesstimate a good port area for 4 sealed-7.75 ported?? 4th order bandopass

Not touching this with a 10 foot pole. Really you should just pony up a few bux to have someone who does a lot of 4th's do up a design for you.