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Old 05-14-2019   #1
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Default Porting midbass

Next install is a Lotus Elise. The stock setup is 5 1/4" in the rear wall and 4" point source in the dash. The cars are known for terrible audio and having zero space for a sub (I've been looking and have never seen one with a ported box or with more than .6 cu. ft sealed).
My goal is midbass with serious impact. Here's what I'm planning:

Rear wall will be HAT L6SE on 150W/side
Dash will be Morel Virtus 402 on 75W/side (probably will keep passive xover)
Sub will be JL 10TW3 on 600W in ported enclosure (.6 cu. ft.)
Helix dsp

So I have a couple questions. First, the 6.5 in the rear wall are in very small sealed enclosures (body is fiberglass and speaker pods are molded in). This could be very good, since I can rework the enclosures however I want. Since I don't have to deal with leaky doors and can run these as dedicated midbass drivers, what is my best option? WinIDS shows significantly better response (3-4 dB) if I port and tune to 50-ish Hz. Any reason not to?
Second, any tips for tuning? Where should I start in crossover between sub and L6? How low can I safely play the Morels to keep as much of the stage in front of me as possible?
Thanks for the excellent advice I always get.

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Old 05-14-2019   #2
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Default Re: Porting midbass

The Morels Virtus MW4 are very stout mid-woofer drivers. I had them mounted in the stock dash locations also. They provided good clean output HP'd at 160hz in my application. Make sure the mounting surface/baffle is sealed off - This made a night and day difference IME. Mortite works great for this.

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Old 05-14-2019   #3
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Default Re: Porting midbass

Quote:
Originally Posted by E.Murray View Post
Next install is a Lotus Elise.
...
Thanks for the excellent advice I always get.
I hope it is not your's but a client's car.
Basically a "sports car" Harkens to motorsports.
If there is a worse car for noise, I do not know what it is.

IMO... They need an Evora or a celica to put a radio in.
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Old 05-15-2019   #4
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Default Re: Porting midbass

Anybody have any advice on this? (Besides "buy a different car," lol).

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Old 05-15-2019   #5
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Default Re: Porting midbass

You should be able to get good midbass output with sealed pods depending on drivers.

What kind of volume do you have?

Sure, you can port them. Not sure if it'll be worth the effort.
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Old 05-15-2019   #6
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Default Re: Porting midbass

I need to see pics, but what I have in my head is an extended baffle (that would look good, again need to see pics) beyond this "pod" back there, to increase volume and potentially speaker size. I had the pleasure of doing something similar in an Elise, way back before I was on a forum or taking pics or anything like we do today.

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Old 05-15-2019   #7
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Default Re: Porting midbass

I don't have it apart yet, but the volume in the stock pod isn't much. I was considering a similar idea (just extending/enlarging the stock pod). That's where the porting question came from. If I'm already fiberglassing a bigger pod, there's no reason I couldn't do an external port without much extra work. Heck, I guess I could just shove a tube onto the existing pod if the volume was about right. Doing the work would require pulling the rear clamshell off, but I'm going to end up doing that anyway so it's all a kind of "while I'm at it" thing... which never ceases to cost me money...

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Old 05-15-2019   #8
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Default Re: Porting midbass

Quote:
Originally Posted by E.Murray View Post
I don't have it apart yet, but the volume in the stock pod isn't much. I was considering a similar idea (just extending/enlarging the stock pod). That's where the porting question came from. If I'm already fiberglassing a bigger pod, there's no reason I couldn't do an external port without much extra work. Heck, I guess I could just shove a tube onto the existing pod if the volume was about right. Doing the work would require pulling the rear clamshell off, but I'm going to end up doing that anyway so it's all a kind of "while I'm at it" thing... which never ceases to cost me money...

Here's the thing though... sometimes porting loses to extra cone area for utility and use of space, and you could also consider tricks like Aperiodic membranes, or passive radiators.



Example, if you cut into the pod in the back end, and insert an AP membrane (and tune it), you could end up with HELLA bass from say an 8" (or stay 6.5") that works great in a tiny space. Or if the space could accept a larger plate up front, maybe a small passive radiator. The options open up potentially.


Any thoughts about using the passenger seat's legroom for the subwoofer? We see that a lot in roadsters.

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Old 05-15-2019   #9
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Default Re: Porting midbass

Do not attempt to use HAT L6se in small sealed enclosures. They are designed for infinite baffle (or at very minimum LARGE enclosures). You will not get the response you are looking for there. Either cut vents to allow them to breathe to outside, or choose a different driver for that application.


Another option to consider for sub is the Dayton HO10 or HO12. Both are quite good in (very small) ported enclosures.

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Old 05-15-2019   #10
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Default Re: Porting midbass

Quote:
Originally Posted by captainobvious View Post
Do not attempt to use HAT L6se in small sealed enclosures. They are designed for infinite baffle (or at very minimum LARGE enclosures). You will not get the response you are looking for there. Either cut vents to allow them to breathe to outside, or choose a different driver for that application.


Another option to consider for sub is the Dayton HO10 or HO12. Both are quite good in (very small) ported enclosures.
Dayton HO 10 or 12 6.5" driver? Haven't seen that one. I model half a dozen 6.5" drivers that would handle the power I have planned and the HAT looked ok (plus I already have them...). What makes them unacceptable? I'm open to alternate drivers. Sitting on a shelf, I also have Faital Pro (6FE100), Rainbox Profi Kickbass, JL C2, and PHD 6.1 Pro. I'd rather use something I have (obviously...), but if there's something that's head-and-shoulders better, I'm in.

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Old 05-15-2019   #11
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Default Re: Porting midbass

Quote:
Originally Posted by fourthmeal View Post
Here's the thing though... sometimes porting loses to extra cone area for utility and use of space, and you could also consider tricks like Aperiodic membranes, or passive radiators.



Example, if you cut into the pod in the back end, and insert an AP membrane (and tune it), you could end up with HELLA bass from say an 8" (or stay 6.5") that works great in a tiny space. Or if the space could accept a larger plate up front, maybe a small passive radiator. The options open up potentially.


Any thoughts about using the passenger seat's legroom for the subwoofer? We see that a lot in roadsters.
My plan was to use the 6.5 from about 70-ish to 200 Hz. I don't necessarily need super low response out of them. As far as the sub, the biggest volume I've seen anybody get is about .4 cu. ct. with zero room for a port. I'm going to mold a box for the shelf behind the seat that will give .6 plus the port volume. I'd prefer the footwell, honestly, but don't see how it would work.

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Old 05-15-2019   #12
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Default Re: Porting midbass

Quote:
Originally Posted by E.Murray View Post
Anybody have any advice on this? (Besides "buy a different car," lol).
Sometime the advice is not what one wants to hear?

There are 3 problems:
1) Noise (Is your 'year model' quiet?), most I have been in have been more sports oriented, and noisy.
2) room
3) electrical power.

If the noise level is pushing over 100dB, then it is hard to get much sound to overpower the noise. Does it have an after market exhaust?

Here is the advice:
Knowing how much SPL you want, and how much noise power, is where I would start.

Is there room in the side sills? What is in those long sections behind/underneath the speaker panel?


Quote:
Originally Posted by fourthmeal View Post
...
Any thoughts about using the passenger seat's legroom for the subwoofer? We see that a lot in roadsters.
^That^ is good advice.
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Old 05-15-2019   #13
 
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Default Re: Porting midbass

I don't see how you can fit a ported box in there. There is just no extra room in these things. I mean don't get me wrong, I love the hell out of a Lotus Elise, but I cannot imagine putting a ported 10 in one.

Sealed for the 10TW3 is 0.4, ported is 0.6 plus the port (which is large as are all low-tuned small boxes) adding up to the size of a .8 cube sealed box. Seriously JL recommends a 30"x"15"x5". That's not a small box.

I don't have any suggestions, but if you can prove me wrong, I'd love to see it. Could be an epic thrill-machine.
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Old 05-15-2019   #14
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Default Re: Porting midbass

Quote:
Originally Posted by JMikeK View Post
I don't see how you can fit a ported box in there. There is just no extra room in these things. I mean don't get me wrong, I love the hell out of a Lotus Elise, but I cannot imagine putting a ported 10 in one.

Sealed for the 10TW3 is 0.4, ported is 0.6 plus the port (which is large as are all low-tuned small boxes) adding up to the size of a .8 cube sealed box. Seriously JL recommends a 30"x"15"x5". That's not a small box.

I don't have any suggestions, but if you can prove me wrong, I'd love to see it. Could be an epic thrill-machine.
The passenger foot area is where tool boxes normally go, and a wedge in there is more comfortable.
A 6-1/2 in some ported engclosure would fit.


But at some point a noise measurement would tell the OP what they are up against.
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Old 05-15-2019   #15
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Default Re: Porting midbass

Quote:
Originally Posted by Holmz View Post
Sometime the advice is not what one wants to hear?

There are 3 problems:
1) Noise (Is your 'year model' quiet?), most I have been in have been more sports oriented, and noisy.
2) room
3) electrical power.

If the noise level is pushing over 100dB, then it is hard to get much sound to overpower the noise. Does it have an after market exhaust?

Here is the advice:
Knowing how much SPL you want, and how much noise power, is where I would start.

Is there room in the side sills? What is in those long sections behind/underneath the speaker panel?
Yes, I've considered all these things. Rather than cluttering up the post with the whole history, though, I was trying to focus on the current questions. I've found that explaining every option and my whole line of thinking in the top post usually nets no replies because it's simply too much to read. Generally, I think it's most useful to ask a clear question without extraneous info. If it's important to know, though, here's the rundown:

- The car is a 2005 Touring model with the stock exhaust (read - as quiet as can be expected).
- I have the "touring" soft top (also as quiet an option as exists).
- I will be using sensible sound deadening (cld on back wall and floor at 40% coverage, ccf and mlv in same locations at 100% coverage).

Yes, an Elise is a noisy car by nature. But they can be made liveable. I'm taking all the necessary steps to reduce noise as a part of the system design.
I've done several installs before and enjoy the fact that every car is different. With this one, the big challenge is space. There is almost no room for anything and I'm not willing to give up any useability. That means everything needs to be small and lightweight.

Maybe for the car after this I'll go to a Suburban or something where I can not have to care so much about every cubic inch.

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Old 05-15-2019   #16
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Default Re: Porting midbass

Quote:
Originally Posted by JMikeK View Post
I don't see how you can fit a ported box in there. There is just no extra room in these things. I mean don't get me wrong, I love the hell out of a Lotus Elise, but I cannot imagine putting a ported 10 in one.

Sealed for the 10TW3 is 0.4, ported is 0.6 plus the port (which is large as are all low-tuned small boxes) adding up to the size of a .8 cube sealed box. Seriously JL recommends a 30"x"15"x5". That's not a small box.

I don't have any suggestions, but if you can prove me wrong, I'd love to see it. Could be an epic thrill-machine.
Challenge accepted! If anybody is interested, I'll post up the box build (it's definitely going up at lotustalk.com). I have a popular carbon fiber box that goes on the shelf behind the seats with .6 cu ft internal volume. It doesn't extend behind the passenger's seat, though. It's easy to space the passenger's seat forward a couple inches. This gives me room for the amps. It also means I can pull a mold from the sealed box and extend it behind the passenger seat. That space will have the port. A 2.5" round port in a "u" shape will fit fine and keep me away from port noise with the sub/power I'm planning.
Or that's all the plan, anyway.

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Old 05-16-2019   #17
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Default Re: Porting midbass

Lets get some pics of the available spaces.

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Old 05-16-2019   #18
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Default Re: Porting midbass

If you are in fact still interested in running ported 6.5 drivers, the Stereo Integrity TM65 mk1 (first generation) was well suited for that appliaciotn.

Here are the specs--

SI TM65 mk1

• 2.3″ mounting depth
DUAL 4 Ohm voice coil
XBL^2 motor topology
• UV and water resistant paper/wool composite cone material
• Ideal for very small ported alignments

Ported enclosure recommendation is 0.3 ft^3 (8.5L) tuned to 56 Hz

120 watts RMS Power Handling
T/S Parameters
Re 6.8 ohms
Fs 44 Hz
Qes 0.33
Qms 2.12
Qts 0.28
Le 0.82 mH
Sd 14230 mm^2
Vas 17.7 L
Mms 21.3 g
Cms 615.4
Sensitivity (1w/1m) 89 db
Sensitivity (2.83v/1m)89.5 db
Xmax 9 mm
Xmec12 mm

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Old 05-16-2019   #19
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Default Re: Porting midbass

Here is what noted car audio equipment designer and enthusiast Andy Wehmeyer says about ported bass drivers--

"The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.

At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.


OK, so what does all of this mean?

1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.

2. If you're going to use a vented box, a woofer with a shorter coil will be fine.

3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.

4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".

So, what's the conclusion?
Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.

When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ. "

Last edited by Andy Wehmeyer; 09-16-2011 at 11:17 AM..

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Old 05-16-2019   #20
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Default Re: Porting midbass

I know more about the noise and issue with this car than most others.
If ear plugs or headphone are legal that is the best option I could find.

If you have the SPL versus speed, then that will highlight what sort of power you will need to equal, or exceed, the noise.

Then With the ear plugs you at least get ~20 dB of noise suppression, which is a huge bonus.

You really only need a strip of dynamat under each seat, and the rear. Literally an 1" wide "X" will do most of the job.

I take it you use it for touring more than sports?
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Default Re: Porting midbass

Quote:
Originally Posted by seafish View Post
Here is what noted car audio equipment designer and enthusiast Andy Wehmeyer says about ported bass drivers--

"The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.

At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.


OK, so what does all of this mean?

1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.

2. If you're going to use a vented box, a woofer with a shorter coil will be fine.

3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.

4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".

So, what's the conclusion?
Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.

When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ. "

Last edited by Andy Wehmeyer; 09-16-2011 at 11:17 AM..
Excellent repost, thanks to you and Andy for that kind of info.

One thing to look at, just because a speaker is optimum for a ported box doesn't make it truly ideal for a midbass. Most speakers will be tuned way to low for a midbass, but that can be a plus if the midbass is up front and sub in rear.

With the mids in the rear, there is absolutely no reason to tune low or crossover from the sub low. The stage will pull to the rear either way.

You can shift the port tuning point up or down, but need to make sure you are paying attention to the Qts to know what the results are going to be before you do it. Otherwise you are likely going to spend lots of time trying drivers.

I would suspect there are lots of 5 1/4" and even 4" drivers that would keep up if tuned and crossed higher than the 6.5"
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Default Re: Porting midbass

This is 11 years old, but it may be relevant .
https://www.lotustalk.com/forums/f3/...ise-spl-60235/

A small speaker in the passenger footwell with a passive radiator would be a decent aproach.it may need two of the PRs??
https://www.parts-express.com/dayton...iator--295-498
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Default Re: Porting midbass

so I have done quite some ported doorpanels in the past. Majority of them were in range of 10-12 litres and diameter of port from 25-40 mm - lenght is determined by enclosure volume, target tunning and port diameter. I got best results when port opening faced to kick-panel area or to the cars floor. I recomend some kind of aeroport ending or at least small roundover at port mouth to suppress port noise. Put appropriate damping materials into the ported panel - foam. Also consider to put a few damping plates on the inner enclosure walls to prevent enclosure ringing and resonating.

Here is the link to one of my installs with ported midbass enclosures
https://www.diymobileaudio.com/forum...-se-crown.html

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Default Re: Porting midbass

Quote:
Originally Posted by LBaudio View Post
so I have done quite some ported doorpanels in the past. Majority of them were in range of 10-12 litres and diameter of port from 25-40 mm - lenght is determined by enclosure volume, target tunning and port diameter. I got best results when port opening faced to kick-panel area or to the cars floor. I recomend some kind of aeroport ending or at least small roundover at port mouth to suppress port noise. Put appropriate damping materials into the ported panel - foam. Also consider to put a few damping plates on the inner enclosure walls to prevent enclosure ringing and resonating.

Here is the link to one of my installs with ported midbass enclosures
https://www.diymobileaudio.com/forum...-se-crown.html




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Default Re: Porting midbass

Lots and lots of great stuff in here. Based on Focused4door's post, maybe I am overthinking it with ported midbass behind me. If they're all behind me, I might as well focus on just doing whatever is safe for the 6.5" drivers and trying to cross the dash drivers as low as possible.
As another idea, what if it was possible to take the volume and put a couple of 8" drivers in place of both the sub and the 6.5" midbass? Purely for the theory of it. I modeled some of the usual suspects (MW172, L8V2) and it looks like I'd be giving up significant low end. But is there a solution using just a pair of 8's?

07 RX8 - JLXD700/5: Rainbow Profi Kickbass, CDT ES-02 (pair per side). Cheapo Boss amp: Rainbow CL25 tweets. JL XD600/1: Sundown SA-12 with PSI high excursion passive radiator. Helix DSP. Stock head unit.
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