sub box question for audio experts
05-26-2003, 01:34 PM
#1
Contributing Member
Thread Starter
Join Date: Apr 2003
Location: denver-home missoula,mt-school
Posts: 753
Likes: 0
Received 0 Likes
on
0 Posts
sub box question for audio experts
i have an rt dual12 sub box and was wondering if i cut out the seperating wall between the 2 subs if it would hit better or cut the back half. It seems like it would. thanks
dexter
dexter
05-26-2003, 01:48 PM
#3
Registered User
Join Date: Jan 2003
Location: Columbia, SC
Posts: 545
Likes: 0
Received 0 Likes
on
0 Posts
Taking out the dividing wall won't do anything, unless you are gonna flip one of the subs around and fire it inward with the other one firing outward. Then it needs to be taken out. Go ported to make the bass hit harder.
Zach
Zach
05-26-2003, 02:31 PM
#4
Away
Join Date: Oct 2002
Location: Beaverton, OR
Posts: 1,588
Likes: 0
Received 0 Likes
on
0 Posts
Ported enclosures have a "Theoretical" advantage over Sealed enclosures when it comes to output capability. But, either type of box will "hit" just as hard if properly designed for the speaker that will be installed in either type of box. Sealed boxes tend to be more musically accurate than ported boxes.
If "boom" is the most important aspect of the box for you, then ported is prolly the way to go, since it is easier to make a ported box boomy than it is to make one accurate. They are subject to more design errors than sealed enclosures and aren't as forgiving if you make a mistake. Just make sure the speaker you use is designed for ported enslosures, as the construction of the speaker's suspension plays an important role in the suitability of the speaker for that particular task.
Removing a divider in a dual woofer enclosure is not recommended because not all drivers are exactly alike and when housed in a common space, they can cancel each other out a bit since they do not behave identically. Also, when housed in their own space, speakers will handle their rated amount of input power more effectively and safely.
If the box isn't loud or deep enough for your taste, make sure the enclosure is the right size and type for the speakers that are installed inside it. Also, make sure you are providing at least the minimum recommended power input. A little EQ can go long way towards correcting a speaker's sonic defficiencies. Similarly, too much EQ can ruin a great sounding box.
Hope this helps.
Dr. Z
If "boom" is the most important aspect of the box for you, then ported is prolly the way to go, since it is easier to make a ported box boomy than it is to make one accurate. They are subject to more design errors than sealed enclosures and aren't as forgiving if you make a mistake. Just make sure the speaker you use is designed for ported enslosures, as the construction of the speaker's suspension plays an important role in the suitability of the speaker for that particular task.
Removing a divider in a dual woofer enclosure is not recommended because not all drivers are exactly alike and when housed in a common space, they can cancel each other out a bit since they do not behave identically. Also, when housed in their own space, speakers will handle their rated amount of input power more effectively and safely.
If the box isn't loud or deep enough for your taste, make sure the enclosure is the right size and type for the speakers that are installed inside it. Also, make sure you are providing at least the minimum recommended power input. A little EQ can go long way towards correcting a speaker's sonic defficiencies. Similarly, too much EQ can ruin a great sounding box.
Hope this helps.
Dr. Z
05-26-2003, 07:45 PM
#5
Registered User
Originally posted by White SR5
Taking out the dividing wall won't do anything, unless you are gonna flip one of the subs around and fire it inward with the other one firing outward. Then it needs to be taken out. Go ported to make the bass hit harder.
Zach
Taking out the dividing wall won't do anything, unless you are gonna flip one of the subs around and fire it inward with the other one firing outward. Then it needs to be taken out. Go ported to make the bass hit harder.
Zach
05-26-2003, 08:13 PM
#7
Registered User
Removing the divider will do only one - increase the box volume very slightly. It will also cause the box to loose some structural rigidity. And considering how every prefab box I've ever seen is a TOTAL POS, I would NOT do that....lol So get a new box or build one yourself using MDF.
Everyone pretty much nailed it saying the same thing I just did, but there are some clarifications. If not haveing your subs divided kills them, your subs are weak POS or are nearing the end of their utilizible lives.
A general rule of thumb is that if you utilize a monoblock amp or a completely bridged output, you dont have to divide the chambers. If you use two channels separately on two different subs you NEED a divider.
The basic reason a ported box is louder across the bandwidth (except for about half an octave under port tuning) over a sealed is because of the air in the port. You see, in a conventional sealed box the back wave emminating off of the backstroke of the cone is absorbed inside of the box. In a ported box this backwave is released into the environment after the port rotates the phase of the backwave about 180*. The larger the port area, the more efficiently the air inside the port will transfer the backwave's energy into the cabin. As a side note, the air inside of the port doesn't ever leave the port, but merely vibrates in time with the woofer so in effect the port acts as another transducer (sub.) This is why you will see an spl gain as you increase the port's area up to about 150% of the transducer's SD (sub's cone surface area.) The problem with increasing port area to 150% of the sub's sd, and keeping the tuning and box volume the same is that the port has to become longer. Generally speaking you dont want a port much longer than about 25" otherwise the port starts to have some really wierd resonances of its own....
Another general rule of thumb is that ported is 3db over the comparable sealed because of the backwave's utilization. Results can vary depending on install however. You may see as much as a 12db gain if you had a wall of subs sealed and suddenly ported them....
Also, your reactive impeadance swings are much less in a ported box (provided you stay above port tuning...lol) The larger the port and the larger the box the less the impeadance spike will be for any given frequency played. This is why aperiodic membranes in sealed boxes help output slightly - they lessen the impeadance jump at any given frequency.
I can explain why there is an impeadance curve that is well above your sub's DCR or Z when playing but will digress unless you or anyone would like to hear it....
Everyone pretty much nailed it saying the same thing I just did, but there are some clarifications. If not haveing your subs divided kills them, your subs are weak POS or are nearing the end of their utilizible lives.
A general rule of thumb is that if you utilize a monoblock amp or a completely bridged output, you dont have to divide the chambers. If you use two channels separately on two different subs you NEED a divider.
The basic reason a ported box is louder across the bandwidth (except for about half an octave under port tuning) over a sealed is because of the air in the port. You see, in a conventional sealed box the back wave emminating off of the backstroke of the cone is absorbed inside of the box. In a ported box this backwave is released into the environment after the port rotates the phase of the backwave about 180*. The larger the port area, the more efficiently the air inside the port will transfer the backwave's energy into the cabin. As a side note, the air inside of the port doesn't ever leave the port, but merely vibrates in time with the woofer so in effect the port acts as another transducer (sub.) This is why you will see an spl gain as you increase the port's area up to about 150% of the transducer's SD (sub's cone surface area.) The problem with increasing port area to 150% of the sub's sd, and keeping the tuning and box volume the same is that the port has to become longer. Generally speaking you dont want a port much longer than about 25" otherwise the port starts to have some really wierd resonances of its own....
Another general rule of thumb is that ported is 3db over the comparable sealed because of the backwave's utilization. Results can vary depending on install however. You may see as much as a 12db gain if you had a wall of subs sealed and suddenly ported them....
Also, your reactive impeadance swings are much less in a ported box (provided you stay above port tuning...lol) The larger the port and the larger the box the less the impeadance spike will be for any given frequency played. This is why aperiodic membranes in sealed boxes help output slightly - they lessen the impeadance jump at any given frequency.
I can explain why there is an impeadance curve that is well above your sub's DCR or Z when playing but will digress unless you or anyone would like to hear it....
Trending Topics
05-26-2003, 09:18 PM
#8
Registered User
Join Date: Feb 2003
Location: Brooklyn NY
Posts: 495
Likes: 0
Received 0 Likes
on
0 Posts
there you go he typed everything i didnt feel like typing hehe.
Bumpin' Yota i understand do you think most of the people that reading this will. sorry not calling anyone stupid or anythign just most people arent into that kinda stuff. my girlfriend makes fun of me for it. cause i can spend 8 hours building a fiberglass box for a speaker she thinks is stupid to begin with. everyone can have there opinion.
Chris
Bumpin' Yota i understand do you think most of the people that reading this will. sorry not calling anyone stupid or anythign just most people arent into that kinda stuff. my girlfriend makes fun of me for it. cause i can spend 8 hours building a fiberglass box for a speaker she thinks is stupid to begin with. everyone can have there opinion.
Chris
Last edited by impulsebrklyn; 05-26-2003 at 09:20 PM.
05-26-2003, 09:36 PM
#9
Registered User
Join Date: Jan 2003
Location: Columbia, SC
Posts: 545
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Bumpin' Yota
This is why aperiodic membranes in sealed boxes help output slightly - they lessen the impeadance jump at any given frequency.
This is why aperiodic membranes in sealed boxes help output slightly - they lessen the impeadance jump at any given frequency.
Zach
05-26-2003, 11:32 PM
#10
Registered User
An aperiodic membrane is a restrictive damping material in a port hole. The membrane BY is referring to is made by cutting a specific size hole cut in the sealed box with restrictive material over the hole. Multichambered boxes would have one aperiodic membrane per chamber. I've seen these membranes made from fiberglass or lambs wool sandwiched between grille or screen material. It lets the sub utilize space outside of the box without the downsides of having both the front and rear of the speaker firing into the same volume (ie cancelling waves = sounding like crap), It's been a while for me, but that's my recollection of how they work.
05-27-2003, 07:54 AM
#11
Registered User
Join Date: Jul 2002
Location: High Point, NC (Buckeye transplant)
Posts: 372
Likes: 0
Received 0 Likes
on
0 Posts
Bumpin' Yota... so would a 1.5" x 13" x 30"-40" slotted port be bad? I'm running a ed12kd2 with a jbl bp300.1 in a 2 cube mdf box. Using winisd i came up with the above port dims. What is your take? What have you found to work well in larger cabin spaces such as the 4Runner?
05-27-2003, 06:05 PM
#12
Contributing Member
Thread Starter
Join Date: Apr 2003
Location: denver-home missoula,mt-school
Posts: 753
Likes: 0
Received 0 Likes
on
0 Posts
well decided i will just sell my old box soon and grab up a new custom built box (with 6x9 on top i dont like all the attachmnet points i have already)
thanks all
thanks all
05-27-2003, 07:44 PM
#13
The basic reason a ported box is louder across the bandwidth (except for about half an octave under port tuning) over a sealed is because of the air in the port. You see, in a conventional sealed box the back wave emminating off of the backstroke of the cone is absorbed inside of the box. In a ported box this backwave is released into the environment after the port rotates the phase of the backwave about 180*. The larger the port area, the more efficiently the air inside the port will transfer the backwave's energy into the cabin. As a side note, the air inside of the port doesn't ever leave the port, but merely vibrates in time with the woofer so in effect the port acts as another transducer (sub.) This is why you will see an spl gain as you increase the port's area up to about 150% of the transducer's SD (sub's cone surface area.) The problem with increasing port area to 150% of the sub's sd, and keeping the tuning and box volume the same is that the port has to become longer. Generally speaking you dont want a port much longer than about 25" otherwise the port starts to have some really wierd resonances of its own....
************************************************** **
interesting way of looking at things happening inside of a speaker BY, but i must disagree about a few things-- ( the larger the port area, the more efficient the system )--- hmm, sounds strange to me. When engineering pro-audio subs, I typically have to use a port calculator to determine the theoretical effective cross sectional displacement as well as reducing the skin effect around the edges of the port. This reduces the mach number to eliminate excessive turbulence outside the port. If just any wierd shaped port would work in any volume, i wouldnt be faced with the problem of eliminating chuffing and driver unloading below Fs. A more simple way to look at porting is to view the system the same way that headers work. The outgoing air from the port has velocity, it is this velocity which reduces the input requirements from the sub, making the needed power for a given xmax decrease. Thus, the 3db gain you are talking about--however, some types of boxes that are ported are often misaligned, resulting in the boominess from guessing about particular port length and diameter.
ok enuf of that crap-- i feel like im at work again, arrrggggg!
what this guy really needs is real power---power fixes everything, if you build the box too small, just add more power ah hah ahahahahahahaha!!! if your woofers die, get woofers that handle more power and then youll really be bangin-- i dont like seeing little 200watt rms amps being used for subs, my motto is, if you can still see-- it aint loud enuf! when i was younger, i had a 90 yota standard cab with 4 excelon DB+ woofers in a cut through and 4 1200watt jbl amps-- i hit 155.5 at 45Hz in that little tiny cab, oh what fun.
Tim
************************************************** **
interesting way of looking at things happening inside of a speaker BY, but i must disagree about a few things-- ( the larger the port area, the more efficient the system )--- hmm, sounds strange to me. When engineering pro-audio subs, I typically have to use a port calculator to determine the theoretical effective cross sectional displacement as well as reducing the skin effect around the edges of the port. This reduces the mach number to eliminate excessive turbulence outside the port. If just any wierd shaped port would work in any volume, i wouldnt be faced with the problem of eliminating chuffing and driver unloading below Fs. A more simple way to look at porting is to view the system the same way that headers work. The outgoing air from the port has velocity, it is this velocity which reduces the input requirements from the sub, making the needed power for a given xmax decrease. Thus, the 3db gain you are talking about--however, some types of boxes that are ported are often misaligned, resulting in the boominess from guessing about particular port length and diameter.
ok enuf of that crap-- i feel like im at work again, arrrggggg!
what this guy really needs is real power---power fixes everything, if you build the box too small, just add more power ah hah ahahahahahahaha!!! if your woofers die, get woofers that handle more power and then youll really be bangin-- i dont like seeing little 200watt rms amps being used for subs, my motto is, if you can still see-- it aint loud enuf! when i was younger, i had a 90 yota standard cab with 4 excelon DB+ woofers in a cut through and 4 1200watt jbl amps-- i hit 155.5 at 45Hz in that little tiny cab, oh what fun.
Tim
05-27-2003, 08:34 PM
#14
Registered User
please forgive the dissection of your post as i think we actually agree on most everything here...
I LOVE power! 3kw and climbing here.
But basically I think we are agreeing on almost all points however your design goal is sound quality with accurate reproduction being paramount with spl only being only a secondary goal.
My design goal is spl being paramount. I do not use round ports nor will I ever - they simply do not provide enough port area. In Db Drag Racing, we only care about how loud you can get a system and thus far it's been a proven fact that more port area up to 150% of the total cone area will be louder than say 50% of the cone area, all other variables being equal. Slot ported enclosures can also be made to sound good but it takes a bit of work to restore the SQ. But I still wouldnt compare a slot ported sub to any true pro audio setup's SQ.
btw - where do you work? I have some interesting experimental box designs I'd like your opinion on.
Steve
Originally posted by Duffdog
interesting way of looking at things happening inside of a speaker BY, but i must disagree about a few things-- ( the larger the port area, the more efficient the system )--- hmm, sounds strange to me. When engineering pro-audio subs, I typically have to use a port calculator to determine the theoretical effective cross sectional displacement...
well yes I believe that you are referring to what the port displaces out of the box which reduces the box's volume slightly and accordingly raises the Vb if you dont account for it. I do the same thing manually when I am tackling ABC boxes or sq oriented vented boxes.
...as well as reducing the skin effect around the edges of the port. This reduces the mach number to eliminate excessive turbulence outside the port. If just any wierd shaped port would work in any volume, i wouldnt be faced with the problem of eliminating chuffing and driver unloading below Fs.
Agreed, the less surface area there is for the moving air inside of the port to contact, the less turbulence there will be. Turbulence equates to odd breathing sounds most of the time. Again in a totally sq oriented application, all turbulence MUST be eliminated. This isnt the case in spl oriented setups - my design goal. Just about any wierd shape will work in any given volume to achieve a tuning but SQ is sacraficed and SPL can be gained. Case in point - my old wall with 488sq in of port that was 15" deep in a 27cubic foot box for 2 DD9515s and 4kw. Truck sealed up tighter than a drum yeiled the score below in my sig off of the dash. Now I didnt really have any port turbulence to speak of and my vent mach was REALLY low, but this was NOT an sq enclosure either....lol
A more simple way to look at porting is to view the system the same way that headers work. The outgoing air from the port has velocity, it is this velocity which reduces the input requirements from the sub, making the needed power for a given xmax decrease. Thus, the 3db gain you are talking about--however, some types of boxes that are ported are often misaligned, resulting in the boominess from guessing about particular port length and diameter.
If I understood that correctly, you have to be playing below the Vb of the enclosure or 1 octave or so above the Vb (tuning.) If you have a box tuned to 37hz, and you are playing 37hz, the cone(s) barely move even at full power, but once you go below the tuning, the port unloads, the sub goes free air, and mechanical power handling drops big time. The same occurs at what is it, 3 octaves above tuning?
ok enuf of that crap-- i feel like im at work again, arrrggggg!
I LOVE this stuff!
what this guy really needs is real power---power fixes everything, if you build the box too small, just add more power ah hah ahahahahahahaha!!! if your woofers die, get woofers that handle more power and then youll really be bangin-- i dont like seeing little 200watt rms amps being used for subs, my motto is, if you can still see-- it aint loud enuf! when i was younger, i had a 90 yota standard cab with 4 excelon DB+ woofers in a cut through and 4 1200watt jbl amps-- i hit 155.5 at 45Hz in that little tiny cab, oh what fun.
Tim
interesting way of looking at things happening inside of a speaker BY, but i must disagree about a few things-- ( the larger the port area, the more efficient the system )--- hmm, sounds strange to me. When engineering pro-audio subs, I typically have to use a port calculator to determine the theoretical effective cross sectional displacement...
well yes I believe that you are referring to what the port displaces out of the box which reduces the box's volume slightly and accordingly raises the Vb if you dont account for it. I do the same thing manually when I am tackling ABC boxes or sq oriented vented boxes.
...as well as reducing the skin effect around the edges of the port. This reduces the mach number to eliminate excessive turbulence outside the port. If just any wierd shaped port would work in any volume, i wouldnt be faced with the problem of eliminating chuffing and driver unloading below Fs.
Agreed, the less surface area there is for the moving air inside of the port to contact, the less turbulence there will be. Turbulence equates to odd breathing sounds most of the time. Again in a totally sq oriented application, all turbulence MUST be eliminated. This isnt the case in spl oriented setups - my design goal. Just about any wierd shape will work in any given volume to achieve a tuning but SQ is sacraficed and SPL can be gained. Case in point - my old wall with 488sq in of port that was 15" deep in a 27cubic foot box for 2 DD9515s and 4kw. Truck sealed up tighter than a drum yeiled the score below in my sig off of the dash. Now I didnt really have any port turbulence to speak of and my vent mach was REALLY low, but this was NOT an sq enclosure either....lol
A more simple way to look at porting is to view the system the same way that headers work. The outgoing air from the port has velocity, it is this velocity which reduces the input requirements from the sub, making the needed power for a given xmax decrease. Thus, the 3db gain you are talking about--however, some types of boxes that are ported are often misaligned, resulting in the boominess from guessing about particular port length and diameter.
If I understood that correctly, you have to be playing below the Vb of the enclosure or 1 octave or so above the Vb (tuning.) If you have a box tuned to 37hz, and you are playing 37hz, the cone(s) barely move even at full power, but once you go below the tuning, the port unloads, the sub goes free air, and mechanical power handling drops big time. The same occurs at what is it, 3 octaves above tuning?
ok enuf of that crap-- i feel like im at work again, arrrggggg!
I LOVE this stuff!
what this guy really needs is real power---power fixes everything, if you build the box too small, just add more power ah hah ahahahahahahaha!!! if your woofers die, get woofers that handle more power and then youll really be bangin-- i dont like seeing little 200watt rms amps being used for subs, my motto is, if you can still see-- it aint loud enuf! when i was younger, i had a 90 yota standard cab with 4 excelon DB+ woofers in a cut through and 4 1200watt jbl amps-- i hit 155.5 at 45Hz in that little tiny cab, oh what fun.
Tim
But basically I think we are agreeing on almost all points however your design goal is sound quality with accurate reproduction being paramount with spl only being only a secondary goal.
My design goal is spl being paramount. I do not use round ports nor will I ever - they simply do not provide enough port area. In Db Drag Racing, we only care about how loud you can get a system and thus far it's been a proven fact that more port area up to 150% of the total cone area will be louder than say 50% of the cone area, all other variables being equal. Slot ported enclosures can also be made to sound good but it takes a bit of work to restore the SQ. But I still wouldnt compare a slot ported sub to any true pro audio setup's SQ.
btw - where do you work? I have some interesting experimental box designs I'd like your opinion on.
Steve
05-27-2003, 09:14 PM
#15
Registered User
Join Date: Nov 2002
Location: Redondo Beach, CA
Posts: 441
Likes: 0
Received 0 Likes
on
0 Posts
I LOVE power! 3kw and climbing here
05-27-2003, 09:17 PM
#16
Registered User
Join Date: Feb 2003
Location: b
Posts: 1,031
Likes: 0
Received 0 Likes
on
0 Posts
1600 watt sonys? To put 1600 watts into sonys you'd need like 10 lol. Save your money and get some Alpine Type-Rs or something
I'm at 2200 watts and hopefully going to 3.6k this summer
I'm at 2200 watts and hopefully going to 3.6k this summer
05-27-2003, 09:30 PM
#17
Registered User
Join Date: Nov 2002
Location: Redondo Beach, CA
Posts: 441
Likes: 0
Received 0 Likes
on
0 Posts
Actually I get all my stuff through my uncle, who used to work for Sony. Right now, I've got two comp 12's (which I've never seen in stores, BTW, only on their website, and they were only there for about a month) which can handle 1200 each, and I'm only running about 300 into each at max. Also, I'm not looking for competitions or anything, just something to make people say 
05-27-2003, 10:42 PM
#18
i work at pacific audio in sacramento, CA. We dont do many spl cars at my work, were mostly alarm and video specialists. Additionally, i own a pro sound company and do sound for concerts and raves and the like. Thats where most of my sound experience comes from. An interesting box that i have only seen once was a dual-folded horn for 2 10" speakers--the two horns came together in an x shaped formation and exited in a common mouth. supposedly it was loud and wonderful and stuff like that .
Im interested in neat designs for car enclosures--although ive about had it with 6th order series tuned bandpass anus blasting super boxes that are supposed to make 1 10" speaker sound like 30 15's.
tim
( you should check out the subs i use for my concert rig---- www.servodrive.com ) i use the basstech7's
.Im interested in neat designs for car enclosures--although ive about had it with 6th order series tuned bandpass anus blasting super boxes that are supposed to make 1 10" speaker sound like 30 15's.
tim
( you should check out the subs i use for my concert rig---- www.servodrive.com ) i use the basstech7's
05-27-2003, 10:56 PM
#19
Registered User
Join Date: May 2003
Location: Lakewood, CO.
Posts: 80
Likes: 0
Received 0 Likes
on
0 Posts
I prefer the coupled method (multiple woofers in one box), I've had better luck with making "anus blasting super boxes" but everybody has there own methods and it does definitly depend on what your trying to accomplish. Build your own new box and ditch the presswooded RT thing your trying to modify
05-28-2003, 06:04 PM
#20
Contributing Member
Thread Starter
Join Date: Apr 2003
Location: denver-home missoula,mt-school
Posts: 753
Likes: 0
Received 0 Likes
on
0 Posts
heres the deal. im gonna pick up one of the new fosgate 600 watts rms sub amps. and also run my old alpine hooked up to it also. then once i have the money (need a new deck first and dont have a job) im gonna get a new custom made dual chamber box that according to my hook up at the car audio store (really smart good guy, i bring him ALOT of buisness from kids at my high school) should be able to really ****in bump out. over 800 watts rms will be the most i know of here in denver and i have meet quit a few ppl (mostly escaldes, navigators, and my friends 4runner which ****in slams at only 300 rms to 2 mtx thunder 8000)
Thread
Thread Starter
Forum
Replies
Last Post
delmert
84-85 Trucks & 4Runners
11
09-30-2015 04:34 PM
Esibnitsud
86-95 Trucks & 4Runners
0
07-30-2015 08:19 PM
rushw
General Electrical & Lighting Related Topics
4
07-18-2015 01:46 PM
crashburnoveride
86-95 Trucks & 4Runners
1
07-10-2015 06:39 AM
