4th order design

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Originally Posted by Moble Enclosurs

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

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

Quote:

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Originally Posted by Moble Enclosurs

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

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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

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Originally Posted by nicholasmccabe

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

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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!

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Originally Posted by Moble Enclosurs

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!

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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??

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Originally Posted by nicholasmccabe

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??

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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

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Originally Posted by Moble Enclosurs

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.

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Quote:

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Originally Posted by 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

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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

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Originally Posted by nicholasmccabe

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

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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!

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!

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Originally Posted by 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!

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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!