Anyone build a custom down fire sub box

markboris

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By the way, I used to live in Layton and Millcreek. Have you had any issues with windshield pitting when trucks lay salt/sand in the winter?
I have Ceramic Pro's Windshield Protection Film on my cars. Unless a boulder hits the windshield, it won't crack and you never get any pitting. It is an extremely clear 6mil film. My Ceramic Pro detailer charges $300 for it and the windshield's glass always look brand new.
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I have a JL 12" Powerwedge+ and it is a very tight fit. Dimensions are 21"W x 13.5"D x 6.75H but with the grill which you would want to keep on, 7.75H. You could go 8"H but that's about it. I do have Dynamat and 1/4" Dynaliner foam over it on the cargo floor and then the OEM carpet on top of that so if you removed all of it, you could gain almost another 1". Mine is facing up.
Thanks Mark! I actually used the W and D from that JL enclosure as a reference. The Hertz needs .7-.8 cubic feet of airspace. So I set the W and D to that spec and then put in the required air space and it came back with 6.26" D for .7 and 6.99" D for .8. So, with the grill at 1.68" inch, I will probably go with the .7 airspace and 6.26" D as that should just squeeze under the floor.

I'll obviously take some more detailed measurements and do some more math just to be sure. TBH, I should probably just buy the one you have, but I like a project. LOL!
 

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@markboris , do you think 250 Watt RMS is enough or do you think I should go for 500?
 

markboris

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@markboris , do you think 250 Watt RMS is enough or do you think I should go for 500?
Hi Dan, that all depends on how loud you play your music, what type of music you listen to, how loud you like your bass and how efficient your subwoofer speaker is. Normally for bass I use a 400-500 minimum but you can certainly get by with a 250 if the price on what you are looking at is much less. For the B&O system which does not play very loud to begin with, I would think the 250 would be fine.
 

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Hi Dan, that all depends on how loud you play your music, what type of music you listen to, how loud you like your bass and how efficient your subwoofer speaker is. Normally for bass I use a 400-500 minimum but you can certainly get by with a 250 if the price on what you are looking at is much less. For the B&O system which does not play very loud to begin with, I would think the 250 would be fine.
Yeah, if I was doing a rebuild I would probably go with 500, but I'm thinking 250 would be good for the B&O. I'll start with the 250 and see how it goes and if I need more power I can return it for a 500. Thanks!
 


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Nice custom build! Do you know what the max width and length a box can be in that space?

These measurements were a draft, not quite perfect but should get you close enough. The first measurement is the floor in upper position, the left 2.5" is where the floor sits nearest the back seats. Second measurements of the bottom showing dip and raise with hash marks. Final measurements are a front view as if you chopped off the bumper. Unsure if this is significantly different for ER battery models.

Ford Mustang Mach-E Anyone build a custom down fire sub box 1737747311713-ci



WinISD is my go to for box modeling - . You can load in all the sub parameters and then figure out how changing parameters (IE box volume, sealed vs ported, etc) will play out. You'll get pretty significant cabin gain between 20-50hz by having the sub in the trunk under the floor. You can get WinISD to model this, but by default it's going to show you what the sub would do in an open field.

IE the predicted measurement for my setup-
Ford Mustang Mach-E Anyone build a custom down fire sub box 1737747657287-b


Vs the actual measurement-
Ford Mustang Mach-E Anyone build a custom down fire sub box 1737747715675-gd


@markboris , do you think 250 Watt RMS is enough or do you think I should go for 500?
It's so much easier to turn an amp down than replace a 250W and sell it as used! The price difference between 250 and 500 has to be tiny. Be absolutely sure you're amp is compatible with the ohms on the final wiring of whatever sub you choose and use a multimeter to set your gains right.

PS - I'm looking at the Stereo Integrity BM-11s for my next project. Might be a good contender for your box, and super easy to load all the drivers you are interested in to WinISD and see how they would perform.
 

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These measurements were a draft, not quite perfect but should get you close enough. The first measurement is the floor in upper position, the left 2.5" is where the floor sits nearest the back seats. Second measurements of the bottom showing dip and raise with hash marks. Final measurements are a front view as if you chopped off the bumper. Unsure if this is significantly different for ER battery models.

1737747311713-ci.jpg



WinISD is my go to for box modeling - . You can load in all the sub parameters and then figure out how changing parameters (IE box volume, sealed vs ported, etc) will play out. You'll get pretty significant cabin gain between 20-50hz by having the sub in the trunk under the floor. You can get WinISD to model this, but by default it's going to show you what the sub would do in an open field.

IE the predicted measurement for my setup-
1737747657287-bg.jpg


Vs the actual measurement-
1737747715675-gd.jpg




It's so much easier to turn an amp down than replace a 250W and sell it as used! The price difference between 250 and 500 has to be tiny. Be absolutely sure you're amp is compatible with the ohms on the final wiring of whatever sub you choose and use a multimeter to set your gains right.

PS - I'm looking at the Stereo Integrity BM-11s for my next project. Might be a good contender for your box, and super easy to load all the drivers you are interested in to WinISD and see how they would perform.
Thank you @iexiak for the response and sharing your details! Good point about just turning it down and with the price difference is like $30, it's kind of a no-brainer. I wasn't sure if I should worry about 50 amps vs 30 amps on the Mach-E, so that's why I thought about going lower power.

That's an interesting sub. I picked up a Hertz MPS 300 S2 (2 ohm) which is rated at 500W RMS so I'm looking at 2 ohm amps.
 

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Thank you @iexiak for the response and sharing your details! Good point about just turning it down and with the price difference is like $30, it's kind of a no-brainer. I wasn't sure if I should worry about 50 amps vs 30 amps on the Mach-E, so that's why I thought about going lower power.

That's an interesting sub. I picked up a Hertz MPS 300 S2 (2 ohm) which is rated at 500W RMS so I'm looking at 2 ohm amps.
You are welcome! I'm running close to 2000W RMS of equipment with no issues so far, though I kinda expect to need to replace the 12v sooner rather than later haha. Once it warms up I'm installing a voltage monitor just to be safe.

I based the 'safe' voltage off a handful of threads in this forum that indicate we should have at least 160 amps available, and then this manual on converting a Mach-e to a taxi on just how much overhead we actually have

https://www.macheforum.com/site/threads/12v-battery-faq.32744/

Ford Mustang Mach-E Anyone build a custom down fire sub box 1737753032373-6a


Ford Mustang Mach-E Anyone build a custom down fire sub box 1737753018179-r1
 

DanoiZ

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and then this manual on converting a Mach-e to a taxi on just how much overhead we actually have
You are welcome! I'm running close to 2000W RMS of equipment with no issues so far, though I kinda expect to need to replace the 12v sooner rather than later haha. Once it warms up I'm installing a voltage monitor just to be safe.

I based the 'safe' voltage off a handful of threads in this forum that indicate we should have at least 160 amps available, and then this manual on converting a Mach-e to a taxi on just how much overhead we actually have

https://www.macheforum.com/site/threads/12v-battery-faq.32744/

1737753032373-6a.jpg


1737753018179-r1.jpg
Most amps are rated at 14.4 volts. Does the Mach-E have any problem with that voltage?
 
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I’d be curious on the Mach e upfitted to police cars, they have to use more juice than a cab with lights, sirens, computers.
I’m still in the planning stage, we’ve had a cold and snowy Jan for VA and haven’t been wanting to do much in the garage when it’s 10 outside.

still hoping to do a down fire with my alpine swrt-10, I can go down to .25 cu ft, need 3.5” internal height for the sub. I may take out the foam and see if my old f150 under seat box I built will fit and allow the floor to go in the low position. If so I won’t bother rebuilding the box.

most likely going with a JL xd/xdm 700x5. It pushes 75 watts to door speakers and 250 to the sub. I’d like to go with the hd 900/5 but afraid 100 watts to the B/O speakers may be too much.
When changing out the front speakers I’m assuming that I’ll have to wire the tweeters separate?
 

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Most amps are rated at 14.4 volts. Does the Mach-E have any problem with that voltage?
Most amps are rated are 14.4v because it gives a larger number and the industry as a whole is kinda scummy that way...unfortunately. Most ICE cars will be 12.4-14.4 depending on charge state. My Mach-e has no problem hitting RMS numbers and above. I would not expect to hit Youtube *wow this amp exceeds it's wattage by 1.5x watts* sorta numbers.
 

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My buddy who is helping me build my box sent me this last night. I searched the forum but I see no mention of this product. I'm interested in the enclosure, but not the sub. Sub specs say it requires 1.2 cubic feet, so this should have plenty of space and volume for my Hertz sub. However, pretty spendy to use just as an enclosure.

https://nvx.com/products/2021-up-fo...-rms-loaded-subwoofer-enclosure-be-frd-mme-g1
 

markboris

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My buddy who is helping me build my box sent me this last night. I searched the forum but I see no mention of this product. I'm interested in the enclosure, but not the sub. Sub specs say it requires 1.2 cubic feet, so this should have plenty of space and volume for my Hertz sub. However, pretty spendy to use just as an enclosure.

https://nvx.com/products/2021-up-fo...-rms-loaded-subwoofer-enclosure-be-frd-mme-g1
I've not seen that enclosure/sub before and looks like a nice large box. However like you, I would not want the speaker as it's probably not as good as what you and I are using. I'm perfectly happy with my woofer that requires a very small box and I still have room for many of the items I want to store back there under the floor.
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