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Dirtrider4eva
05-06-2012, 06:07 PM
I have 2 15" RE XXX '05 era.
i have 7.5 cu feet on tap to play with.
now for IDEAL specs, these each want 8 cu feet.
but many run this around 3-3.5 tuned to 30-34 hz.
would i be better off putting two in the enclosure, or 1?
im looking to maintain their SQ, while still getting loud for what they are.
will have them on 2k dailly.
itd be in a hatch, and this box will take up the whole trunk, so itd be subs up, port to cabin.
the seats will be folded down for the most part.
would aero ports be best used?
btw, resonant frequency of the car is 49hz
http://images.dealerrevs.com/gallery/photo.php?id=48855150

09civic
05-06-2012, 06:10 PM
I suggest having the port load off one of the sides of you trunk. Not straight into your cabin.

Dirtrider4eva
05-06-2012, 06:13 PM
there would be no room for air movement. box would run right along the grey supports for the top tray, (which would be taken out)

09civic
05-06-2012, 06:16 PM
there would be no room for air movement. box would run right along the grey supports for the top tray, (which would be taken out)


Even better...

Dirtrider4eva
05-06-2012, 07:45 PM
For ported? Not really. Ideally 5-6" would be best. Bump

keep_hope_alive
05-06-2012, 10:10 PM
I vote one, port close to cone for good coupling.

brynm
05-06-2012, 10:12 PM
Use one, sell me the other.

brynm
05-06-2012, 10:16 PM
Where did you come up with the 8 cube number? I thought these were more in the range of 3.5-4.

Dirtrider4eva
05-06-2012, 10:27 PM
I vote one, port close to cone for good coupling.

Explain this coupling please, I know you know your stuff very well.

Dirtrider4eva
05-06-2012, 10:28 PM
Where did you come up with the 8 cube number? I thought these were more in the range of 3.5-4.
If you put them in winisd or call re audio, they will tell you that. Also, I got a d4 and d1, d4 is original soft parts, d1 has new Fi recone.
Shoot me an offer if ya want on one.
Has to do with the xbl^2 motor structure. Almost every sub I know with tht motor type likes huge cubic boxes.

keep_hope_alive
05-07-2012, 12:44 AM
Explain this coupling please, I know you know your stuff very well.

A port works by combining the rear wave with the front wave, but after a period of time/distance so the two are in-phase. That is why you gain 3dB.

Waves combining in-phase is what I call "coupling". If the port and cone are separated by a distance, they will create separate waves with separate centers, the coupling will not be coherent at some frequencies.

Dirtrider4eva
05-07-2012, 10:42 AM
A port works by combining the rear wave with the front wave, but after a period of time/distance so the two are in-phase. That is why you gain 3dB.

Waves combining in-phase is what I call "coupling". If the port and cone are separated by a distance, they will create separate waves with separate centers, the coupling will not be coherent at some frequencies.

so ideally, the woofer should be right over/closest to the ports outlet or inlet?

keep_hope_alive
05-07-2012, 01:53 PM
so ideally, the woofer should be right over/closest to the ports outlet or inlet?

yep.

boxes with ports on different faces are missing the point entirely, IMO

kushy_dreams
05-07-2012, 02:36 PM
yep.

boxes with ports on different faces are missing the point entirely, IMO

By this you mean sub up port to the rear or sub back port to the side? Or do you mean a box with multiple ports that fire to both sides?

keep_hope_alive
05-07-2012, 03:01 PM
By this you mean sub up port to the rear or sub back port to the side? Or do you mean a box with multiple ports that fire to both sides?

Yes to all.

kushy_dreams
05-07-2012, 03:18 PM
Yes to all.

Ok, well how do you explain people gaining spl or metering the highest with a sub up/port rear or sub forward/port to the side, like what suv's, hatches and non blow through pickup trucks use.

keep_hope_alive
05-07-2012, 06:57 PM
easy. they have a poorly designed system and no idea how it behaves. they experiment and see what happens. in all cases, they are not realizing the full potential of their system. If Nate Munson can break 170dB with a single 10" and people struggle to break 150dB with multiple large woofers - you see what i'm talking about. SPL competitions are exercises in who can apply physics to their advantage.

vehicles are dynamic systems. change placement and many things change. the pathlength between cone and listening position vs. port and listening position vs. both port and cone to reflecting planes to listening position, etc. in your example, the change in position/orientation resulted in constructive phase interference at some frequencies.

Rotate a box and you will get different results because you change reflections. In a closed environment such as a car reflections dominate response characteristics. it's like dropping a pebble in the bathtub. what starts as a circular wave quickly turns into chaos as reflected waves interact with each other.

the problem with the cabin and frequencies of interest is that constructive and destructive interference cause variations in response at measured locations. this is why you may peak with a certain frequency at the dash but a different frequency at the seat. why rotating a box changes response.

regardless, the goal of a ported box is to get constructive interference at the measurement location. but ports cause both constructive and destructive interference. it is why they have such a sharp roll-off. the "tuning frequency" is simply the length were constructive interference ends and destructive interference begins. the wavelength below that point is longer and you get the rear wave cancelling the front wave. but really, a tuning frequency is relative to the port vs cone position relative to the listening position and vehicle reflections.

it's a dynamic system.

Dirtrider4eva
05-07-2012, 09:56 PM
I see, so in your opinion, in my Celia hatchback, what port sub style would be best? Sub up port to cabin? For a 7 cube box I would be limited to that. A 5 cubic box I could do port and sub in any direction.

Why So Cereal?
05-07-2012, 10:00 PM
easy. they have a poorly designed system and no idea how it behaves. they experiment and see what happens. in all cases, they are not realizing the full potential of their system. If Nate Munson can break 170dB with a single 10" and people struggle to break 150dB with multiple large woofers - you see what i'm talking about. SPL competitions are exercises in who can apply physics to their advantage.

vehicles are dynamic systems. change placement and many things change. the pathlength between cone and listening position vs. port and listening position vs. both port and cone to reflecting planes to listening position, etc. in your example, the change in position/orientation resulted in constructive phase interference at some frequencies.

Rotate a box and you will get different results because you change reflections. In a closed environment such as a car reflections dominate response characteristics. it's like dropping a pebble in the bathtub. what starts as a circular wave quickly turns into chaos as reflected waves interact with each other.

the problem with the cabin and frequencies of interest is that constructive and destructive interference cause variations in response at measured locations. this is why you may peak with a certain frequency at the dash but a different frequency at the seat. why rotating a box changes response.

regardless, the goal of a ported box is to get constructive interference at the measurement location. but ports cause both constructive and destructive interference. it is why they have such a sharp roll-off. the "tuning frequency" is simply the length were constructive interference ends and destructive interference begins. the wavelength below that point is longer and you get the rear wave cancelling the front wave. but really, a tuning frequency is relative to the port vs cone position relative to the listening position and vehicle reflections.

it's a dynamic system.

I haven't seen one of these type posts from u in a while.....good read man once again. I wanna be like u when I grow up

keep_hope_alive
05-07-2012, 11:57 PM
I see, so in your opinion, in my Celia hatchback, what port sub style would be best? Sub up port to cabin? For a 7 cube box I would be limited to that. A 5 cubic box I could do port and sub in any direction.

Traditionally, hatchbacks benefited most from sub and port in the rear, for loading along the hatch. Same concept, you want the port and sub to combine coherently. I would have a slot port at the rear with the sub right in front of it. Will effectively lower tuning a bit.

kushy_dreams
05-08-2012, 01:19 AM
easy. they have a poorly designed system and no idea how it behaves. they experiment and see what happens. in all cases, they are not realizing the full potential of their system. If Nate Munson can break 170dB with a single 10" and people struggle to break 150dB with multiple large woofers - you see what i'm talking about. SPL competitions are exercises in who can apply physics to their advantage.

vehicles are dynamic systems. change placement and many things change. the pathlength between cone and listening position vs. port and listening position vs. both port and cone to reflecting planes to listening position, etc. in your example, the change in position/orientation resulted in constructive phase interference at some frequencies.

Rotate a box and you will get different results because you change reflections. In a closed environment such as a car reflections dominate response characteristics. it's like dropping a pebble in the bathtub. what starts as a circular wave quickly turns into chaos as reflected waves interact with each other.

the problem with the cabin and frequencies of interest is that constructive and destructive interference cause variations in response at measured locations. this is why you may peak with a certain frequency at the dash but a different frequency at the seat. why rotating a box changes response.

regardless, the goal of a ported box is to get constructive interference at the measurement location. but ports cause both constructive and destructive interference. it is why they have such a sharp roll-off. the "tuning frequency" is simply the length were constructive interference ends and destructive interference begins. the wavelength below that point is longer and you get the rear wave cancelling the front wave. but really, a tuning frequency is relative to the port vs cone position relative to the listening position and vehicle reflections.

it's a dynamic system.


Thank you so much! I love when you post this kind of stuff. I swear between you and audioholic I have learned more from just a handful of your guy's posts, than I have spending countless hours reading the thousands of posts from others over the years.

hispls
05-08-2012, 01:27 AM
A port works by combining the rear wave with the front wave, but after a period of time/distance so the two are in-phase. That is why you gain 3dB.

Waves combining in-phase is what I call "coupling". If the port and cone are separated by a distance, they will create separate waves with separate centers, the coupling will not be coherent at some frequencies.

Funny how you almost never see a top tier SPL box with port and sub on the same side....


OP, if soft parts are not matching you must only run 1. Use the one with the aftermarket recone if you want half a chance at holding 2K for any period of time.

TaylorFade
05-08-2012, 02:01 AM
yep.

boxes with ports on different faces are missing the point entirely, IMO

I'm not sure I can agree with you there.


Funny how you almost never see a top tier SPL box with port and sub on the same side....




Exactly.

Seems to me that your coupling theory would indicate that you wouldn't want the sub and port very close to one another. One is 180* from the other. Unless there is some harmonics or some such that I'm ignorant of.

Most SPL competitors spend a crap ton of time trying to accomplish the coupling of which you speak. To get the front and rear wave to arrive at the mic or listening position at the same time. It's incredibly beneficial. And about 99% of the time not accomplished by sub and port in close proximity unless it's a wall. And that's only because it's a wall.

I've actually seen some interference graphs. Fascinating. They weren't focused on sub and port locations. IIRC, it was comparing monopole and dipole pressurization, but it was clear to see the interference pattern of the dipole (vented alignment).

keep_hope_alive
05-08-2012, 07:53 AM
all good points, guys. my opinions are just that. there is a combination of fact and opinion in everything i say. :)

lots of people have ports on opposite faces. usually it stems from physical space. then people see others doing it and copy the design without ever understanding why. some do it on purpose and have a very good reason (though they are the minority). ports on opposite faces can/will affect the realized tuning frequency depending on the orientation in the vehicle. that may be a good thing, but it likely wasn't modeled. as far as i know, we don't have commerically available software that will not only model box performance, but also allow you to import a 3D model of the vehicle to calculate interference. you are welcome to perform the calculations yourself - but very few ever will. to me, that is the difference between understanding and experimentation.

just recognize what the port is actually trying to do (combine rear with front), and everything should make more sense. then you can decide what orientation you want based on the physics that govern the results.

yes, interference patterns are very cool! i saw some computer modeling at an ASA conference that was very neat.

i am certainly simplifying this whole process and focusing on one key aspect of vented enclosure implemetation. there are other benefits such as reduced back-pressure which helps increase available excursion, the impedance mis-match between port and space, etc.

keep_hope_alive
05-08-2012, 08:02 AM
Seems to me that your coupling theory would indicate that you wouldn't want the sub and port very close to one another. One is 180* from the other. Unless there is some harmonics or some such that I'm ignorant of.


in general, you do want the port and cone close, you do want the rear wave to combine with the front to create one new wave - not two separate waves that have to combine later. the port length is what allows the rear wave to travel a further distance and be in-phase with the front wave.

think of it in terms of path length. visualize or calculate the wave (peaks and valleys). wavelength is 1125ft/sec divided by frequency. when a rear wave travels 1/2 of a wavelength (at a particular frequency) it is now in-phase with the front wave.

putting the port at the rear increases the distance travelled by the rear wave (before it combines with teh front wave) and thus can lower tuning frequency.

the concept of "loading" is just taking advantage of reflections as soon as possible so they too are in-phase with the original. it's why putting a sub in the corner of a room excites all room modes.

and room modes... that's another subject entirely.


just think that if all of this goes into the placement of one sub and one port - how much more complex the system becomes when you have multiple subs and multiple ports?!? when you have different path lengths from each sub to the port - they are effectively tuned differently and they will interact before they even have a chance to leave the port. it becomes very complicated very quickly. i believe simplicity is king, install is 90% of the success, and the vehicle is the weakest link.

some of this is stuff i have read in textbooks, but most is just my thought process in how i'm trying to understand these very dynamic, non-linear systems. i could be wrong. but i did stay at a holiday in express...

itsblown
05-08-2012, 08:15 AM
in general, you do want the port and cone close, you do want the rear wave to combine with the front to create one new wave - not two separate waves that have to combine later. the port length is what allows the rear wave to travel a further distance and be in-phase with the front wave.

think of it in terms of path length. visualize or calculate the wave (peaks and valleys). wavelength is 1125ft/sec divided by frequency. when a rear wave travels 1/2 of a wavelength (at a particular frequency) it is now in-phase with the front wave.

putting the port at the rear increases the distance travelled by the rear wave (before it combines with teh front wave) and thus can lower tuning frequency.

the concept of "loading" is just taking advantage of reflections as soon as possible so they too are in-phase with the original. it's why putting a sub in the corner of a room excites all room modes.

and room modes... that's another subject entirely.


just think that if all of this goes into the placement of one sub and one port - how much more complex the system becomes when you have multiple subs and multiple ports?!? when you have different path lengths from each sub to the port - they are effectively tuned differently and they will interact before they even have a chance to leave the port. it becomes very complicated very quickly. i believe simplicity is king, install is 90% of the success, and the vehicle is the weakest link.

some of this is stuff i have read in textbooks, but most is just my thought process in how i'm trying to understand these very dynamic, non-linear systems. i could be wrong. but i did stay at a holiday in express...
I always enjoy reading your post. I see you're an acoustical engineer and Im actually considering majoring in it but its all kind of iffy any advice? Also questions about vented enclosures and enclosures in general. How far should the opening of the port and sub woofer be from the wall its unloading on. In my case the back of hatchback with subs and port facing the hatch I know it probably changes but what happens if its too close too far away?

hispls
05-08-2012, 11:56 AM
Unfortunately the port and woofer are only 100% in phase with eachother at one point anyway. Also pathlengths of frequencies in the sub 60hz range make phase issues minimal over such small differences. It's not like mids and tweets where the crossover point has a half wave of a couple inches.... we're talking about half waves of 8 feet or more to have complete destructive interference.

OP, Port should be at least a port width away from walls when installed. Even a port width away generally will act as an extension of the port, too close and the port won't load properly at all and the box may begin to act like a leaky sealed box.

Dirtrider4eva
05-08-2012, 12:05 PM
Traditionally, hatchbacks benefited most from sub and port in the rear, for loading along the hatch. Same concept, you want the port and sub to combine coherently. I would have a slot port at the rear with the sub right in front of it. Will effectively lower tuning a bit.
i see. so having a box firing directly into the front of the car wouldn't allow propping loading? correct?
and having a single sub and port facing the hatch rear is my best current use?


Funny how you almost never see a top tier SPL box with port and sub on the same side....


OP, if soft parts are not matching you must only run 1. Use the one with the aftermarket recone if you want half a chance at holding 2K for any period of time.
this is what confuses me, how just about every thing i see is subs up, port front or back.
also i was planning for recone man. just got it at a steal.


OP, Port should be at least a port width away from walls when installed. Even a port width away generally will act as an extension of the port, too close and the port won't load properly at all and the box may begin to act like a leaky sealed box.[/QUOTE]

hispls
05-08-2012, 02:05 PM
Subs up and port back (or to side/corner) seems most popular in hatchbacks. Considering some of us aren't scared to build dozens of boxes and try them in any conceivable position to figure out what's optimal, don't re-invent the wheel. I can say from personal experimenting subs ad port forward is a colossal failure in my Jeep. Subs and port up is decent, but sub up and port towards a corner has been best for me.

Really I see loads of top end home theater towers that port out the rear or have passive radiators firing out a side. I think B&W and the like probably have good reasons for doing these designs, but this illustrates the point that good sound isn't conditional on ports and drivers on any particular plane with eachother.

Make sure both subs have matching softparts if you plan to use the pair.

Dirtrider4eva
05-08-2012, 04:28 PM
Subs up and port back (or to side/corner) seems most popular in hatchbacks. Considering some of us aren't scared to build dozens of boxes and try them in any conceivable position to figure out what's optimal, don't re-invent the wheel. I can say from personal experimenting subs ad port forward is a colossal failure in my Jeep. Subs and port up is decent, but sub up and port towards a corner has been best for me.

Really I see loads of top end home theater towers that port out the rear or have passive radiators firing out a side. I think B&W and the like probably have good reasons for doing these designs, but this illustrates the point that good sound isn't conditional on ports and drivers on any particular plane with eachother.

Make sure both subs have matching softparts if you plan to use the pair.
Ok,
And yeah they would. Well if I have them firing into a corner(s)
My trunk is widest near the hatch wall due to wheel wells,
So would ports go to both corners or one? I would love to build a dozen boxes, but I don't own a tl, nor have the time to build so much. :crap:

winkychevelle
05-08-2012, 05:06 PM
personally ive had good luck with subs and port up in the eclipses ive done in he past. last one had 4 t1 tens with a dual 4 inch ports on 800 per sub and it metered a decent 153 which i found was good for fosgate. the same box in a ford 500 trunk on the other hand with 4 p3 tens on 1200w total was burping 151s.

looking at your car i would try sub up port to the back if you can squeeze 6-8 inches of free space along he back of the hatch

Dirtrider4eva
05-08-2012, 05:19 PM
Both up towards hatch? That'd be interesting. Picture my trunk as rectangle box with a triangular plane on top. Towards the hatch it gets shorter, so I could do subs and ports to hatch, but can only go so deep before it'd have little room.
However im still taking in ideas up

wickedwitt
05-08-2012, 05:24 PM
yep.

boxes with ports on different faces are missing the point entirely, IMO


By this you mean sub up port to the rear or sub back port to the side? Or do you mean a box with multiple ports that fire to both sides?


Yes to all.

That's odd, I was told by someone who knows his stuff the exact opposite (that you never have the cone and port opening on the same plane and you most certainly don't have the two in close proximity to one another)

Dirtrider4eva
05-08-2012, 05:33 PM
That's odd, I was told by someone who knows his stuff the exact opposite (that you never have the cone and port opening on the same plane and you most certainly don't have the two in close proximity to one another)
I've heard that too, where putting them farthest apart can build up best unloading.. Gahh

---------- Post added at 04:33 PM ---------- Previous post was at 04:32 PM ----------


personally ive had good luck with subs and port up in the eclipses ive done in he past. last one had 4 t1 tens with a dual 4 inch ports on 800 per sub and it metered a decent 153 which i found was good for fosgate. the same box in a ford 500 trunk on the other hand with 4 p3 tens on 1200w total was burping 151s.

looking at your car i would try sub up port to the back if you can squeeze 6-8 inches of free space along he back of the hatch

What the heIl did u do to your cruze! I remember u just got tht

n8skow
05-08-2012, 05:40 PM
A little tid-bit on the 7th gen Celica's - the peak frequency is actually in the 58-61hz range in these cars... (not good for music), though there is also a smaller peak in the 47-50 hz range, which you seem to have found...

For music, I'd go woofer either up or to the back - with port to the driver side (leave 5-6" space on port side of box for clearance).

keep_hope_alive
05-08-2012, 08:09 PM
That's odd, I was told by someone who knows his stuff the exact opposite (that you never have the cone and port opening on the same plane and you most certainly don't have the two in close proximity to one another)

using the work "never" instantly negates the statement and credibility. :) in general, avoid absolutes. :P

you want the port output to combine in-phase with the woofer cone. you want the two to add constructively anything else and they do not fully add. who wants that? if you didn't want them to combine, then you would just port it outside.

how you achieve this addition is vehicle/install/orientation/distance dependent.

my point is that it's the easiest to achieve accurate tuning with them on the same plane, and it's the easiest to work with. the wavelengths are long enough that they will act as one source.

one reason for having them on different planes is to get more distance to lower the effective tuning frequency. may not be a bad thing.

OP - you'll get a dozen different recommendations from a dozen people. that's what forums are good for - variety. you won't get a consensus.

build and test then build again... or build and run with it.

keep_hope_alive
05-08-2012, 08:25 PM
the theory behind home audio port placement is different then pro audio port placement which is different than car audio port placement. one commonality is that all three are environment dependent.

it's hard to draw a line between all platforms and make a general statement. my opinions above were for car audio only.

the cool thing about home and pro audio is all of the R&D. hundreds of hours per speaker system. and still, there is every variation possible.

one truth is that anything properly implemented can be successful.

Dirtrider4eva
05-08-2012, 08:29 PM
I guess I'm stuck with playing around. Maay do a 6 cubes sealed box and do tht. Really going for what the woofer is designed around, SQL,
I'm not disregarding anyone's opinions, but I'll see if I can fit a port to driver side, can also try both facing hatch, and simply rotate the box up to see if it changes.

keep_hope_alive
05-08-2012, 09:48 PM
Experimentation is easier and more fun than computation. :)

Dirtrider4eva
05-08-2012, 09:55 PM
Experimentation is easier and more fun than computation. :)

Appreciate the input,
You're one of the few who knows a great deal with this.
May be pm'in you about other things if I need help!

hispls
05-08-2012, 10:17 PM
Ok,
And yeah they would. Well if I have them firing into a corner(s)
My trunk is widest near the hatch wall due to wheel wells,
So would ports go to both corners or one? I would love to build a dozen boxes, but I don't own a tl, nor have the time to build so much. :crap:

By "into corner" that's mainly an SPL trick where a box is actually sitting at an angle firing into the corner, though in a lot of applications firing the port out the side works nicely.

Dirtrider4eva
05-08-2012, 10:21 PM
I see. I'll keep that in mind. I guess I shouldnt of got 2 15s, no chance in fitting em really

keep_hope_alive
05-08-2012, 10:49 PM
By "into corner" that's mainly an SPL trick where a box is actually sitting at an angle firing into the corner, though in a lot of applications firing the port out the side works nicely.

in a corner you increase the overall source amplitude by 6dB compared to sitting on a flat plane with no reflecting surfaces. each reflecting plane gives you 3dB (since the reflection adds perfectly to the source). but the distance you need to be to the corner to achieve this gain is based on wavelength. note that if your reflecting plane is a quarter-wavelength away, then it results in cancellation.

kramer_212
05-08-2012, 10:50 PM
didn't you know that adding another woofer makes it 8 times as loud.

Dirtrider4eva
05-09-2012, 07:39 AM
in a corner you increase the overall source amplitude by 6dB compared to sitting on a flat plane with no reflecting surfaces. each reflecting plane gives you 3dB (since the reflection adds perfectly to the source). but the distance you need to be to the corner to achieve this gain is based on wavelength. note that if your reflecting plane is a quarter-wavelength away, then it results in cancellation.
I see. So 5-6" wont be that beneficial? I know a quarter wave length of 40hz is roughly 4feet, so any waves within 20 hz I should be fine..