Can someone explain this odd subwoofer design?

louibluey

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Yes there was an unused closed grommet as if it was intended for wiring at some point. I made a little x cut in the rubber and ran the 8 gauge wire through. Had to do the same thing on the inside as it was closed there too. There was a little circle on the inside which was opposite the grommet on the outside. Made a cut in there and the wire came the rest of the way through. I attached the fuse to the negative cable wire with a tie strap. Wanted to be able to access that fuse if needed to with only taking the one panel off so that is why I attached it there.

Not sure if I am the first person to add a sub to the Mach-E but maybe the first one posting it here. Like I said before this was not even on my list of projects for this car but I had all the panels removed under the front truck because of other projects I am working on so figured, why not run a wire to the back for future sub. I did not take any more photos than the ones I posted earlier but have had some requests for what it looks like behind the trim panel where the OEM sub is so might pull that apart again and take a photo. I will write something up when I am finished tomorrow after the sub (hopefully) comes in.
Is that positive connection some kind of very high current fuse linked for accidents? I guess there must be some kind of fused bar between the battery + terminal and that heavy cable supplying the fuse box? I worry a bit about crushed cable insulation making a short to chassis ground in an accident.

[Never mind. I see, the fuse IS in the blue + cable, you were just saying that you physically tied the fuse holder to the ground cable for easy access :) ]

Very nice runs! That grommet it great too.
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louibluey

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Mark, Awesome project instructions!

I remember that you Dynamat the entire car. Do you think there would be enough improvement to just do the area in the picture for someone following your sub woofer project?

Which Dynamat part number do you use? Any preferred suppliers?
 
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markboris

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Mark, Awesome project instructions!

I remember that you Dynamat the entire car. Do you think there would be enough improvement to just do the area in the picture for someone following your sub woofer project?

Which Dynamat part number do you use? Any preferred suppliers?
Joe, if you were to add just a sub, yes I would do the cargo area under the floor pad. When I pulled the pad, that entire metal floor would "ring" if I hit it with my knuckles. Not good if you are adding a sub there. You can use pretty much any rubber butyl sound deadener like Dynamat, Hushmat, SecondSkin Damplifier, Stinger Roadkill, etc. I added 1/8" Dynaliner foam on top of the Dynamat material but really didn't need to as the floor pad is heavy with a lot of jute backing on it to deaden the sound. You don't want to add too much height to the floor otherwise the floor pad won't fit properly. I buy my sound deadening supplies either from local auto stereo places and if they are out, Amazon.
 

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louibluey

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Well, the cargo area seems like as good a place as any to learn this sound dampening process. Just ordered a bunch of Dynamat, 1/8" liner, the roller tool, the JL sub with amp (from Mark's post, JLAudio ACS110LG-TW1), and a wiring kit! I'm pretty intrigued by this project. I've changed out a lot of tweeters and speakers over the years, but never got as far as Dynamat.
 
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Yep, that is what this is - an infinite baffle subwoofer. IB subwoofers are great because they are more power efficient and reduce distortion compared to sealed or ported enclosures.

Sealed enclosures are a lot less efficient because they have a powerful air spring behind the driver (the air in the box). This limits excursion (good to avoid killing your driver), and prevents distortion from group delay (signals arriving at different times), so is good for high accuracy applications where you have plenty of power and big drivers.

Ported enclosures attempt to improve efficiency by recovering some of the energy from the back of the driver by directing it through the port. The problem is that it only boosts energy at the ports tuning frequency, and the fact that you now have signals arriving from two places at two different times increases group delay distortion. It is easy to design a ported enclosure that is LOUD, but hard to design one that sounds GOOD. Big boomy blurry bass is typical for simple ported designs.

Infinite baffle tries to solve both problems - it is energy efficient because the driver doesn't fight an air spring - the outdoor air isn't being compressed, so the driver can move at full excursion easily. You avoid group delay because you still only have one source. You do need to carefully EQ so you don't over-extend the driver.

I think they are gaining popularity in cars, but they've been used for a long time in home theater - the simple implementations put the driver up in the attic or down in the crawl space, and use a rectangular box to connect it to a hole in the ceiling with a heater vent over it. No big box, no big drivers visible, but lots of big omnidirectional bass that is easy to tune the room around.
If the space between interior and external panels is intended to be an infinite baffle/transmission line, it would be interesting to observe whether there is a noticeable difference in sound (inside the car, of course) from the stock speaker with the felt wheel well liner installed and then removed.
 
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I think that depends on the style of music that you want listen to.
 

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@markboris, is the subwoofer driver in this bracket/enclosure replaceable? In other words, if you remove those 4 torx screws, does the driver come out of the bracket? There are some aftermarket 6x9" subwoofer drivers available and I'm tempted to try one out in the quest for at least marginally better bass.
 

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@markboris, is the subwoofer driver in this bracket/enclosure replaceable? In other words, if you remove those 4 torx screws, does the driver come out of the bracket? There are some aftermarket 6x9" subwoofer drivers available and I'm tempted to try one out in the quest for at least marginally better bass.
The DSP on these systems is designed for the specific acoustical properties of the drivers used. Changing the speaker could have the consequence of actually making it sound worse due to creating peaks or notches in the frequency response, or differences in the phase response. The factory speaker has a specific resonant frequency that works with the cabin volume.

If you want more bass, you're probably better off making a separate subwoofer enclosure.
 
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@markboris, is the subwoofer driver in this bracket/enclosure replaceable? In other words, if you remove those 4 torx screws, does the driver come out of the bracket? There are some aftermarket 6x9" subwoofer drivers available and I'm tempted to try one out in the quest for at least marginally better bass.
You are a day too late. I just had that woofer out in my second Mach-E adding some sound deadening and wiring up for a sub and would have checked. I just got the cargo area all set up with CanvasBack coverings for my dog and not going to be pulling the panels off again to check. It looks like it may be replaceable but as Lee stated in the post above, the DSP/AMP in these type of systems are matched and tuned for their drivers. I think no matter what 6x9 you might replace it with, doubt it would sound better and most likely worse.
 

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@Mach-Lee and @markboris,

Thanks for responding. Yeah, I hear what you're saying that the signal is probably EQ'd/DSP'd to match the driver/enclosure/acoustics. I don't have the car yet and haven't really put the audio system through its paces on a test drive, but it sounds like bass is fairly lacking. That said, I don't need terribly deep/loud bass, so I might still be tempted to tinker with this without adding a real sub/enclosure. We'll see how bad it is and how motivated I get. Are there any level adjustments for the factory sub?

I removed the right trim panel in the cargo area in front of the OEM sub and disconnected the wires to the sub. Attached an 18 gauge speaker wire to the two wires that were going to the sub for my audio input to the JL amp. Green/Violet + and Gray -. Just above the OEM sub is the B&O amp and to the left of it is a ground to the metal wheel well. I also used this grounding point to attach my 8 gauge ground wire for the JL amp.
From your very helpful thread on your sub upgrade, it sounds like you didn't take any measures to correct for the B&O signal processing. Or did you and I missed that? There are devices like Kicker's KEYLOC that attempt to return a processed, high-level signal back to a flat, line-level signal.
 
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@Mach-Lee and @markboris,

Thanks for responding. Yeah, I hear what you're saying that the signal is probably EQ'd/DSP'd to match the driver/enclosure/acoustics. I don't have the car yet and haven't really put the audio system through its paces on a test drive, but it sounds like bass is fairly lacking. That said, I don't need terribly deep/loud bass, so I might still be tempted to tinker with this without adding a real sub/enclosure. We'll see how bad it is and how motivated I get. Are there any level adjustments for the factory sub?

From your very helpful thread on your sub upgrade, it sounds like you didn't take any measures to correct for the B&O signal processing. Or did you and I missed that? There are devices like Kicker's KEYLOC that attempt to return a processed, high-level signal back to a flat, line-level signal.
There are no level adjustments for the factory sub. The bass adjustment in the tone control section of settings brings up the bass in the entire system, not just the sub and it's more like a mid bass control.

No I did not correct for the B&O signal processing and did not see a need to. There is no lack of low end bass information going to the OEM sub, it just doesn't play it. However sending the OEM signal to the JL Audio sub amp produces plenty of low end bass. Had it not, I would have used a device like the KEYLOC but saw no need to. In my Escape I used an Audison Bit One processor and in the Focus RS, used a JL Audio Fix 86 processor to take the digital input to the OEM amp/DSP and reprocess it to flat for all the channels and then ran my own amps. I won't be going to that extreme here in the Mach-E.
 

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I read through the entire article and still do not understand why it is ported outside. Am I missing something here?


That rectangular hole I show in one of the above photos goes OUTSIDE. If I were to take off the fiber wheel well liner behind the right rear tire, you will see that whole and can look straight up into the woofer enclosure through the port. If you want, I can take a photo of that too from the outside behind the fiber liner.
I know I am very very late to this thread, but it looks like the system used in the Mach-E is an "infinite baffle". It is used in some very high-end systems (as well as some low-end systems). I am pretty sure it is used in the Mach-E because of it's lower power requirements. Here is a link for some information on these systems
 

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I know I am very very late to this thread, but it looks like the system used in the Mach-E is an "infinite baffle". It is used in some very high-end systems (as well as some low-end systems). I am pretty sure it is used in the Mach-E because of it's lower power requirements. Here is a link for some information on these systems
Correct the reason is the 'sub' should be in a box, but because they didn't have room for the box that sub requires it is running essentiality as infinite baffle. This works and I've done it many a time using the trunk as the 'box'. What they did is send the 180 degree phase sounds out of the car. Reason is if you take a sub, without a box and play it, it's pretty much nothing. Unless you build a wall to separating the front and back of the sub.

When a woofer moves forward it creates 'sound pressure and waves' going forward, but it also has to do the same going backwards. What happens is the sound frequencies (waves) going forward will get canceled out by the waves going backwards as they are 180 degrees out of phase. As sound is omnidirectional the front and back of the woofer will cancel each other out. This is most prominent on sub 100htz (kick bass and below sounds). Mids and tweets sound waves move fast enough they don't really get a chance to cancel each other out before they reach your ear. Subwoofer waves move slowly and they're 'fat'. Very large slow waves. If you could play a 30htz tone you could almost see the woofer moving 30 times in a second. Really you'd see somewhere between 10 to 15 cycles.
Ford Mustang Mach-E Can someone explain this odd subwoofer design? 1679519902846

Think of the red wave as the front. The black as the back. The dotted line is what you actually hear. Mostly nothing as the front and back cancel each other out. You'll feel more than your hear at woofer frequencies. Same tech used for noise canceling headphones, they just 'play' an equal wave 180 degrees out of phase to cancel it out. That's why airpods etc will pressurize your ear trying to cancel out low freq noise.

Back to the wall example (also what this silly enclosure is doing) if you wall off the woofer you only hear the red or black wave. Punch a smallish hole through the wall and you will lose sound volume as some of the sound waves could get through that hole. The bigger the hole in the wall the more out of phase waves get through the less loud your woofer sounds.

Lets take this a step further and explain why a ported enclosure doesn't do this. The port (usually some form of pipe) that 'vents' the inside of the box to the front/back/side/whatever is venting air, and thus sound waves to the front of the woofer is tuned (if properly built. i.e. not most off the shelf amazon truck boxes) to match a frequency. Usually ported boxes match to something around 60htz as 45 to 90htz sound pressure is very noticable. The basis of it is the port is delaying the 180 out of phase waves long enough to match or at least not cancel out the front of the woofer. Properly ported enclosures take a lot of specs into account along with a q ratio. Technical babble but it's part of the math involved in syncing the front and back of the woofer via it's enclosure.

Or take the easy way out and put the back waves out of the car.

Oh, and if you had the B&O woofer in and played music then had someone cover the hole you'd notice that you lose a lot of the sound from that speaker. This is due to the enclosure not being big enough to let the woofer move forward or backward anymore. It wouldn't be massively obvious with this little speaker but do it to a 10 inch ported box that small and it's much more obvious. Ford couldn't run this like a speaker in the door because of all the vents built into those back panels for the amps and computers.
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