For the Flex guys/gals - Subwoofer boxes in stealth locations

[Josephm]

What did you tune those sd's too?

They are sealed, so there's no tuning other than the box itself.  That said, we achieved a 1.16 cubic foot box, plus some polyfil compensation, so the Qtc of the box is below .7.  These are subs that love being in small boxes.  After a brief break-in, I decided to push my system on these and found the limit of my amp before the limit of the sub.  And that limit was well beyond what I have experienced in the Flex yet. 

Sorry i should of been more specific, What did you tune the box to? impressive how much power those SD's can take. 1.16 cu ft, damn

the box looks really good. Way beyond the detail i have ever done into with all those curves. I stick to squares

[Lanson]

What did you tune those sd's too?

They are sealed, so there's no tuning other than the box itself.  That said, we achieved a 1.16 cubic foot box, plus some polyfil compensation, so the Qtc of the box is below .7.  These are subs that love being in small boxes.  After a brief break-in, I decided to push my system on these and found the limit of my amp before the limit of the sub.  And that limit was well beyond what I have experienced in the Flex yet. 

Sorry i should of been more specific, What did you tune the box to? impressive how much power those SD's can take. 1.16 cu ft, damn

the box looks really good. Way beyond the detail i have ever done into with all those curves. I stick to squares

The really cool thing is, the shape was no harder than a regular square box, other than being more cuts.  I set the fence and the angle, and then repeated the cut again and again, and that made identical shapes that I was able to quickly glue and brad-nail into place.  The end result is a box with more space than a square, but not harder to make at all.  In fact, I was stunned at how well the box just "went together" on its own.  I would have zero issue replicating my results for other people, if need be.  The only problem I ran into was how to make it fit in the car itself.  I had to trim the top board a tiny bit because I ran into a wedge issue, where the 3rd row seats and the back panel of the Flex itself made it hard to wedge in this box.  A bit of jigsaw work and that was fixed, so all good.

Here's the finished product BTW.





Carpet looks a little wonky in the pictures, I just vacuumed it so it has some lines in it.

So the only thing I need to do is lock the top board down somehow.  I'll work on that this weekend while the owner of this box is with me to install the rest of his system.  Got some ideas for that.

[BiGMaC]

Lanson... Excellent Work..... I can hardley wait to see you do some for the SHO!  I am very impressed!

[Lanson]

Lanson... Excellent Work..... I can hardley wait to see you do some for the SHO!  I am very impressed!

What would you guys like to see done?  I need either a test vehicle for a while, or some really good pics and really good measurements.  Then I can create a basic model in 3D, and have someone build a cardboard test example to prove it works.  Then it is just a matter of making sawdust.

[BiGMaC]

Lanson... Excellent Work..... I can hardley wait to see you do some for the SHO!  I am very impressed!

What would you guys like to see done?  I need either a test vehicle for a while, or some really good pics and really good measurements.  Then I can create a basic model in 3D, and have someone build a cardboard test example to prove it works.  Then it is just a matter of making sawdust.

I'll get you some pics and measurements... Thinking in the trunk..across the area behind the back seat...(I may need my spare!) .. forward firing subs and port forward if ported...fits up on the "shelf" behind the seats with ability to mount amp and/or DSP on the rear of the box for tuning... I don't need to be able to see the subs, but i do need to be able to access the electronics.

Other info you need?... let me know.... and TIA, You're the man!

[LowFrequencies]

What did you tune those sd's too?

They are sealed, so there's no tuning other than the box itself.  That said, we achieved a 1.16 cubic foot box, plus some polyfil compensation, so the Qtc of the box is below .7.  These are subs that love being in small boxes.  After a brief break-in, I decided to push my system on these and found the limit of my amp before the limit of the sub.  And that limit was well beyond what I have experienced in the Flex yet.

I ran the SD2 10s in my F150 EB as I intended on having a down-firing enclosure, but eventually got a ported forward facing for it.  They were amazing, and I threw well over 1000 watts at them (Rockford Fosgate T1000-1bdCP @ 1 ohm).. they loved it.  Very stout for taking the power they did so efficiently.  Now I run the SA-10s in a similar enclosure, and boy do I love them.  Great choice going with Sundown, and those enclosures look AMAZING!

[Lanson]

Lanson... Excellent Work..... I can hardley wait to see you do some for the SHO!  I am very impressed!

What would you guys like to see done?  I need either a test vehicle for a while, or some really good pics and really good measurements.  Then I can create a basic model in 3D, and have someone build a cardboard test example to prove it works.  Then it is just a matter of making sawdust.

I'll get you some pics and measurements... Thinking in the trunk..across the area behind the back seat...(I may need my spare!) .. forward firing subs and port forward if ported...fits up on the "shelf" behind the seats with ability to mount amp and/or DSP on the rear of the box for tuning... I don't need to be able to see the subs, but i do need to be able to access the electronics.

Other info you need?... let me know.... and TIA, You're the man!

Sounds great, but definitely REAR-fire.  Acoustically, we also want to keep the output of the port and the output of the sub together.  That's the main purpose of a ported box, to tune with the sub itself.  To use the port only would be the responsibility of a BANDPASS box.  Which, btw, we could engineer to perfection as an option. 

Front-firing a sealed box creates create response in the mid-bass / bass region, but the sub bass gets lost.  Example:
This is a build I did for my brother in-law's Sentra

False wall rear

A full amp and processor rack on a shelf (to allow the spare tire room to get out as needed)


This system was incredibly loud, but could not dig super deep.  Testing with a basic RTA and mic found that the front-firing subs were actually cancelling out via the wave that was being created in the trunk and reflecting back to the cabin.  Bass waves pass right through most materials, so even though we blocked the trunk off with wood and carpet (and foam seal), it was transparent to bass.  The result, a damn loud but not very low-playing system, despite some gorgeous Alumapro subs.

This system (which was made in haste and for temporary use only, so forgive the not-professional amp mount up top) was in my Acura TL, and would play down to the lowest frequencies you could dare a 10" to go.  Granted, these are special subs (Acoustic Elegance AV-H10), but point is they were rear-firing, and the bass wave was not cancelling out like we experienced with the Sentra.

Instead the ski pass-through showed off the massive (and expensive) Human Reign Unleashed amp for the front stage. 


Another example of the power of going rear-fire, the awesome Chrysler 200S build I did for one of my friends.  Rear-firing 15" Image Dynamics sub (sealed).  This system was probably the most amazingly low-playing setup I've ever done.  The lessons learned from other builds showed me that, despite the fact the seats fold down and there's a shelf to port through, our best bass performance came from a rear-fire trunk setup.  Best by a long shot.

[Lanson]

I was also going to add, if the car is present, we could attempt an IB setup.  This would involve a structural reinforcement of the shelf, and an under-mount of VERY large subwoofers with relatively high X-max, relatively low RMS max wattage abilities, and massive cone area.  This would only work in a trunk that is well-sealed off from the cabin, except for the shelf itself which would be where the sub's output meets the cabin, and makes the trunk the enclosure itself. 

IB is serious, but there is no box and that can be an incredibly wonderful thing with the right subs, and right equipment.  You must seal off the cabin from the trunk entirely however.


Another approach is to use a high-tune bandpass design, whereas the port is run directly to the cabin.  High-tune 4th order (bandpass) boxes act like a more efficient sealed box on the low end, and it doesn't "unload" like a 2nd order (ported) box does after tuning frequency.  This does not require a heavy sealing job from the cabin to the trunk, but does require a very well designed enclosure (with some anticipated trial and error because T/S specs on the sub may be off a fair amount in reality), and a very well made port that leads into a smooth connection and transition to the shelf.  This may not work for a lot of vehicles.

[BiGMaC]

I think I see your points... thanks.  I still need some useable trunk, apparently not a problem. I would definitely want subsonic response... in the old days the OZ Superman sub impedence spike was at 5 HZ on the DVC so it produced about 15HZ below sub sonic before any Db loss and the 3Db down was almost 2Hz... It rocked the world without getting loud at 300W with a 2 1/2" excursion.................. In any event true sub-bass is what I'm looking for.  I am not a big bandpass fan myself. I have liked ports in the past to allow more electrical excursion (move more air)... and acknowledge that port tuning is an art form. I understand that response may be tighter in a closed system, but it has never seems as deep as ported enclosure to me.  I have done IB with pickups (opening the front of the box and the rear of the cab and installing a flexible connection plus a top rigid cover to make the cargo bed the box... used Aura Prosound 36" subs... but as you say this is serious (and for SPL contests) as well as potentially dangerous... IB is a bit more than I need.

Given the above thoughts,  what would your suggestions be as far as configuration?... I would think 2  good 12" subs would be enough.

[Lanson]

I think I see your points... thanks.  I still need some useable trunk, apparently not a problem. I would definitely want subsonic response... in the old days the OZ Superman sub impedence spike was at 5 HZ on the DVC so it produced about 15HZ below sub sonic before any Db loss and the 3Db down was almost 2Hz... It rocked the world without getting loud at 300W with a 2 1/2" excursion.................. In any event true sub-bass is what I'm looking for.  I am not a big bandpass fan myself. I have liked ports in the past to allow more electrical excursion (move more air)... and acknowledge that port tuning is an art form. I understand that response may be tighter in a closed system, but it has never seems as deep as ported enclosure to me

Given the above,  what would your suggestions be as far as configuration?... I would think 2  good 12" subs would be enough.

Given the parameters and desires, I think we need to carefully measure that space and see if a pair of 15" subs would work.  Specifically, low inductance, high excursion, and small-ish box compatible.  I'm sure that would perform very well based on your needs.  Alternates would be a low-tuned ported box, either single 15 or single 12, or a similar config using passive radiator(s) instead of ports.  Those are fun BTW. 

A 15" is doable if the height of the shelf bottom to the top is more than 15" itself.  Another thing you could do is slightly overlap the shelf (like a step-down) and reach into the trunk a bit more with, say, a an inch or two extra.  12" would probably fit on the shelf as-is.

Brands I'm thinking about, off the top of my head for this:  Sundowns (naturally!... Probably the SA series or similar), Fi Audio (local to me), Creative Sound Solutions SDX sub, Dayton subs, Image Dynamics lower end options, TC Sounds stuff, etc.

[BiGMaC]

Thanks!... sounds good.... and few options! Measurements and pics tonight...