4th order design

[nicholasmccabe]

Can anyone help me. I am trying to get a new setup for 2 sundown sa 15s d4. I wanna do a 4th order bandpass blowthrough my rear armrest in a 1997 cadillac seville. I have a nice size trunk but the box will have to be built in sections because the opening isnt that big.
Roughly 7 or 8 cubes to work with. PLEASE HELP!!!!!!

[nicholasmccabe]

Meaning, when the trunk lid is up, theres only so much space to slide a box in. I had a single 15 in a ported box, it was 3.5 cubic feet. It barely slid into the opening. which isa why the 4th order will have to be buld and installed in sections.

[wenn_du_weinst]

a 4th order for 2 15's isn't going to fit in 8ft.
you could try 4ft ported and 2ft sealed each but I doubt it will be very loud.

[nicholasmccabe]

if we maximize space i can do 10 or 11 cubes. I dont care to have any room left after this goes in. Just room for amps, i have no extra batteries and such

[Flastrongman]

I can design one for you for a small fee. And it can get very loud in that space

[Jroo]

The best 4th order I ever heard was in the trunk of a deville. He had 4 10" round solobarics. The box took a majority of his truck and ported directly through the ski hole. It pounded so hard but had zero trunk rattle at all. The car had a ton of deadning and when you opened the doors, bass literally rolled out from nowhere. Everyone that heard that car said ****, but the car played music just as well as it pounded.

[CAT MAN]

The best 4th order I ever heard was in the trunk of a deville. He had 4 10" round solobarics. The box took a majority of his truck and ported directly through the ski hole. It pounded so hard but had zero trunk rattle at all. The car had a ton of deadning and when you opened the doors, bass literally rolled out from nowhere. Everyone that heard that car said ****, but the car played music just as well as it pounded.
mm skihole 4th orders.

[nicholasmccabe]

Exactly what i was thinking!!! Why wouldnt it be the best way to go!! all output goes directly into the cabin!! I give 2 ***** about hjaving any room left in the trunk. Im just not being reassured that the a pair of SA 15s will be ok in a 3 or 3.5 sealed section , firing into a 6 or 6.5 ported section tuned to aroung 42 or 45 hz. I had a series tuned 6th order and i dont think it was pinpoint accurate, so i had it roughly a week before i blew my Rockford T2 15". It was fine when it was in a ported box, but as soon as it went into the 6th, it started sounding like ****. Not to mention the 6th sounded like **** on music. I need to know that if I do the 4th order, that it will play rap music and also kill the lows for some bass mechanic and some chopped and screwed music. I like alot of lil wayne:D

[nicholasmccabe]

Has anyone heard of this 80inches designing 4th orders?? Will 3 cf sealed and 6 ported not be enough for the 2 SA15s?? I have a 10x10 area for the port to button up to on the backseat.

[nicholasmccabe]

anyone?? Heres what i got so far. I will be doing 2-SA15s D4, wired to 1 ohm on a Rockford Fosgate PowerBD1500.1. The 4th order i have sketched out will be built in 2 sections.

Sealed Section:Gross
34" Wide
15.5 "Deep
17" Tall
Ported Section:Gross
34" Wide
28" Deep
17" Tall

I will have to put the ported section in first and then slide the sealed section, have some type of connecting pieces drilled onto the top of the boxes, and some seals to make the connection airtight.

I will be using a 1.75:1, ported to sealed. I will be porting through the rear armrest, Looking at around 50 inches of port area. Im thinkin it will be 15" Tall, about 6" wide, and 6 inches long?? HOw will that be!!!! Efffing bangin Son. Thats whats up!! Tune that beaaatch at around 42 , its going in my cadillac, Decaf FTMFW!!!!

[galacticmonkey]

Just do 2 cubes sealed per sub and then use whatever other space you have as ported. Even if it ends only being 4 cubes ported plus port, you would still be good.

[nicholasmccabe]

ok. Gmonkey, will you help me with the port?? Like I said , the hole i have trimmed out behind the rear armrest is about 12" tall and 6 1\2 wide. How long shall i make the port for a tuning of 42 or 44 hz?? I wanna do music and have decent numbers for next season < and dont forgtet i wanna do hairttricks from the trunk.. With out all the bull shat taking out the back seats, cutting the rear deck out, all that rubbish. I wanna clean install, and be able to do black girl hair tricks. As my wife is black

[nicholasmccabe]

anyone

[JeepGuy]

There is a calculator for port length in the12volt.com and a few other sites but I'm on my phone right now otherwise I would tell you the exact length.

[galacticmonkey]

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

[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. :D

[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. :D

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 :D

[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.

[FlexnInLa]

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 :D

Just did my 18 box, next one is gonna be a 4th order. Well worth the small amount of money to get a design.

[nicholasmccabe]

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 :D

yes, its a 4th order bp with 4ealed, 7..5 ported. Looks like sealed resonance is around 47-48, ALTHOUGH, my port is tuned to 52-53, does it need to be at the sealed resonance for maximum effeciency

[Moble Enclosurs]

yes, its a 4th order bp with 4ealed, 7..5 ported. Looks like sealed resonance is around 47-48, ALTHOUGH, my port is tuned to 52-53, does it need to be at the sealed resonance for maximum effeciency

Not really. It will not be at sealed resonance. It can be a harmonic of it, but this would require the sealed portion to even be much larger than the ported area. You may have a quarter-wave resonance of 47-48, but not a full wave resonance. Resonance and tuning are two different factors also, but they do hold some relationship when it comes to response control. So, you answer your question fully, it can be better for you so have one of the sealed enclosure quarter-wave resonances on an axial plane to match that of the tuning from the ported side, and this can be done by changing not just the volume but more so the corss-sectional plane of the baffle area to change the dimensional sides of a certain volume. Being that the sealed side does not connect with the wave of the ported side, the main focus of it is for low end extension from mechanical control of the sub. The sealed area controls more of that in a 4th order, but for a quasi 6th or 8th order design, it can be more usable for resonance matching with the ported side.....especially when it comes to doing hair tricks ;D.

So, if you have a sealed area of 4 cubes, then the changes of that will happen more when you change not the volume, but the depth. Changing the depth, changes the resonances that occur on each plane of the enclosure. Again, this is more when the sealed area works with the ported area for coupling and resonance matching, but not so much in 4th orders. In 4th orders, the volume is more of a concern than the shape in that excursion limitations can be vastly improved by volume decreases, but even that has to be figured in with how much power you are putting into it, and what the actual driver limits are. When you can match the power rating at full tilt with the mechanical limits not to go over, but by about 2mm difference from the xmax range of the driver from the lowest cutoff of the design, then you have a proper sealed area to work with. Then ported side can be modeled much like a conventional bass-reflex design for efficiency. This will be figured based on the requested range you want to use, but keep in mind that going away from the recommended tuning from the driver specs will also affect efficiency over a broad range of frequencies. 4th orders do not have to be one note wonders. In fact, they can make wonderful musical boxes. Tuning too low can hurt that possibility. Tuning too high can as well, but this is why the sealed area exists, to control low frequency efficiency for getting a lower response output without hurting the sub or amp or anything in the circuit. A box is in essence a circuit as well. This has to be considered when designing also and in a 4th order, this can be very sensitive to the electrical load when powered. This is why bandpasses (derived from an electrical term for that reason) can be so tough to design.

So, to take from this, the sealed part is less sensitive to tuning and passband as the ported is and is more for controlling the rolloff and mechanical control with respect to thermal limitations, but can be matched with resonances of the tuning side with positive effects (need to be modeled for each scenario and may not be a good thing each time-something to really look into). The ported side can be designed without the initial concentration of being a 4th order as long as you have the room to play with the dimensions, which if you are doing a 4th, you should anyhow. 4th orders rely more on pressure and limits of the sub than acoustical efficiency. The efficiency that needs to be concentrated on more is how much you can get out of the sub without blowing its mechanics, or burning the coils. If you can reach the near limits of the specs, a 4th order can give you great output in the bandpass region it is tuned in regardless of any other factor. The larger the design (along with driver cone area and power), the more efficient it is also and the broader the response (in a vehicle or constant volume chamber). So, go big!!!! just control the excursion, power and keep the tuning high enough to get the output you want. I can tell you what the best tuning is using an optimal volume if requested. Email me on that, but in general your tuning you are using now should be in the near range of optimum anyhow.
Hope that helps!

[nicholasmccabe]

Not really. It will not be at sealed resonance. It can be a harmonic of it, but this would require the sealed portion to even be much larger than the ported area. You may have a quarter-wave resonance of 47-48, but not a full wave resonance. Resonance and tuning are two different factors also, but they do hold some relationship when it comes to response control. So, you answer your question fully, it can be better for you so have one of the sealed enclosure quarter-wave resonances on an axial plane to match that of the tuning from the ported side, and this can be done by changing not just the volume but more so the corss-sectional plane of the baffle area to change the dimensional sides of a certain volume. Being that the sealed side does not connect with the wave of the ported side, the main focus of it is for low end extension from mechanical control of the sub. The sealed area controls more of that in a 4th order, but for a quasi 6th or 8th order design, it can be more usable for resonance matching with the ported side.....especially when it comes to doing hair tricks ;D.

So, if you have a sealed area of 4 cubes, then the changes of that will happen more when you change not the volume, but the depth. Changing the depth, changes the resonances that occur on each plane of the enclosure. Again, this is more when the sealed area works with the ported area for coupling and resonance matching, but not so much in 4th orders. In 4th orders, the volume is more of a concern than the shape in that excursion limitations can be vastly improved by volume decreases, but even that has to be figured in with how much power you are putting into it, and what the actual driver limits are. When you can match the power rating at full tilt with the mechanical limits not to go over, but by about 2mm difference from the xmax range of the driver from the lowest cutoff of the design, then you have a proper sealed area to work with. Then ported side can be modeled much like a conventional bass-reflex design for efficiency. This will be figured based on the requested range you want to use, but keep in mind that going away from the recommended tuning from the driver specs will also affect efficiency over a broad range of frequencies. 4th orders do not have to be one note wonders. In fact, they can make wonderful musical boxes. Tuning too low can hurt that possibility. Tuning too high can as well, but this is why the sealed area exists, to control low frequency efficiency for getting a lower response output without hurting the sub or amp or anything in the circuit. A box is in essence a circuit as well. This has to be considered when designing also and in a 4th order, this can be very sensitive to the electrical load when powered. This is why bandpasses (derived from an electrical term for that reason) can be so tough to design.

So, to take from this, the sealed part is less sensitive to tuning and passband as the ported is and is more for controlling the rolloff and mechanical control with respect to thermal limitations, but can be matched with resonances of the tuning side with positive effects (need to be modeled for each scenario and may not be a good thing each time-something to really look into). The ported side can be designed without the initial concentration of being a 4th order as long as you have the room to play with the dimensions, which if you are doing a 4th, you should anyhow. 4th orders rely more on pressure and limits of the sub than acoustical efficiency. The efficiency that needs to be concentrated on more is how much you can get out of the sub without blowing its mechanics, or burning the coils. If you can reach the near limits of the specs, a 4th order can give you great output in the bandpass region it is tuned in regardless of any other factor. The larger the design (along with driver cone area and power), the more efficient it is also and the broader the response (in a vehicle or constant volume chamber). So, go big!!!! just control the excursion, power and keep the tuning high enough to get the output you want. I can tell you what the best tuning is using an optimal volume if requested. Email me on that, but in general your tuning you are using now should be in the near range of optimum anyhow.
Hope that helps!

Just shot you an email.

Thank oyu for rdponding, i am having z hard time figuring out how to get my port walls correct. If i keep the 16x8 port, the walls have to be in excess of 10inches deep to get a good tuning. So the magnet of teh inverted subs are only a few inches away from the end of the port. IS this ideal??

[Moble Enclosurs]

Just shot you an email.

Thank oyu for rdponding, i am having z hard time figuring out how to get my port walls correct. If i keep the 16x8 port, the walls have to be in excess of 10inches deep to get a good tuning. So the magnet of teh inverted subs are only a few inches away from the end of the port. IS this ideal??

I emailed you back, but to give a quick answer (though I am known to not do this, lol)....it is not ideal to have the sub near the port opening vs loaded in a corner area, for two reasons.....1. distortion levels. In subs, distortion is inevitable. The amount can make or break the design and be more audible in that position---less filtering. 2. response output- This is involving the volume and how it is used for resonance control. If the sub is loaded more efficiently INTO the box, the low output will be better because of the distance from the port opening to the subs radiative position. Though, furthest is not always best, is it ''ideal'' if and when you can. It creates smoother output and better low end in a lot of cases. That may be your only quarrel at this point, IDK. I emailed you for some details. Be back on tomorrow! Later bro.

[Moble Enclosurs]

Best to get ahold of me via email. I am barely on here anymore. been busy with designs for a while now. :D

[nicholasmccabe]

I emailed you back, but to give a quick answer (though I am known to not do this, lol)....it is not ideal to have the sub near the port opening vs loaded in a corner area, for two reasons.....1. distortion levels. In subs, distortion is inevitable. The amount can make or break the design and be more audible in that position---less filtering. 2. response output- This is involving the volume and how it is used for resonance control. If the sub is loaded more efficiently INTO the box, the low output will be better because of the distance from the port opening to the subs radiative position. Though, furthest is not always best, is it ''ideal'' if and when you can. It creates smoother output and better low end in a lot of cases. That may be your only quarrel at this point, IDK. I emailed you for some details. Be back on tomorrow! Later bro.


Best to get ahold of me via email. I am barely on here anymore. been busy with designs for a while now. :D

Ok cool man. Thanks alot, and this brings me to my next question that i think was inevitable from the beginning,
1. To helll with the center port, why dont i just cut a new loading wall and make slot port on drivers side?? That way i can keep the l;enght down and it shouldnt need ton be but 3-5 inches long. JHows that sound

[Moble Enclosurs]

Ok cool man. Thanks alot, and this brings me to my next question that i think was inevitable from the beginning,
1. To helll with the center port, why dont i just cut a new loading wall and make slot port on drivers side?? That way i can keep the l;enght down and it shouldnt need ton be but 3-5 inches long. JHows that sound

Well, you then start to run into phase differences from the driver and port at different locations for the listening position. Luckily, for the polar response of a low frequency wave in vehicles being broad and less directive, loading in the opposite corner of the vehicle can prove to be quite exponential for low output regardless of the phase differences at a certain point. With a 4th, this should not be a problem especially with high power situations. I would rather be safe than sorry, but again for not doing any figures on it, loading to the passenger side will/should give better results than you are likely seeing now. The center port can cause issues in a 4th in some cases of limited volume (in comparison to optimum), but it does allow for balanced pressure changes in the enclosure for smoother output (all depending on the limitations again). Shoot me some more emails when you get the chance or PM me on FB. Best way to contact me now days :D. Hope that helps!

[Ronny]

I really enjoy your informative posts Mobile.
You must be getting uber busy nowadays though buddy, it's been awhile since one of these! Hehe, sending you an email btw sir :-)

Thanks!

[Moble Enclosurs]

I really enjoy your informative posts Mobile.
You must be getting uber busy nowadays though buddy, it's been awhile since one of these! Hehe, sending you an email btw sir :-)

Thanks!

Thanks bro. Yea, getting very busy lol. That is why I am hardly on here anymore. :( But it is what it is. Glad I have had the time in the past week to post a few times. Hope to hear from you soon!