Final decision, opinion on 3 designs (box specs & photos included), thank you

[strreamix]

First off, thank you very much for your time. I am in the final stages of deciding which box to build for my car. I am trying to figure out which box would best suit my musical preferences (will discuss below). I do understand that box building and finding a "specific sound" is often trial and error, but for me the reality of the situation is once the box is in, it most likely will be staying in. Therefore, I'd like to get as close as possible to what I want the first time and I know the members here have much more experience than myself. Hopefully you guys can provide me with some direction. Thank you.

Subwoofer is a 13.5" JL W7 powered by JL Slash v1 1000.1

The first design (2.49ft3 @ 30.24hz) was designed by a forum member on another forum. (very nice gentleman named Blazer)

The second design (2.78ft3 @ 31hz) was designed by JL audio customer support. 

The third design (2.375ft3 @ 34.6hz) is JL's "to specification" ported box.

The car is a BMW M4 coupe. The trunk/doors are second skinned already. My musical preference focuses "thunderous" and "explosive" low bass, typically within the range of 28-40hz. Most of my favorite songs have their peaks around 30-34hz. I feel like the "JL to specification" box did achieve nice combination of thunder and explosiveness in my old car many years ago. I suppose what I am seeking to find out is, is there better than that? Continuing with the musical preferences, I run a 24db slope on my 1000.1 @ 50hz because the "buzzy" bass gives me a headache. My M4 also has the HK sound system which does a good enough job for me at doing the 80-200hz range. SPL is not a concern of mine, I rarely ever listen to my system over 75% volume. SQ is definitely a priority. (but I do not want a sealed box).

For some musical comparison, my previous car was a G35 and in this car I have a ported box that is 12 3/4" height by 24" depth by 19" width. I believe it is tuned around 39hz. This was all the trunk had room for. This box is MUCH more tame and less enjoyable than when I had the JL "to specification" ported box in my first car. It was MUCH less explosive and somewhat less thunderous. Perhaps that comparison can further aid in what I am looking for.

Additionally, if anyone wanted to throw a design into the mix that they feel would be superior to these 3, here are the max dimensions that can get through the opening of the trunk. The subwoofer box can be no taller than 15", no wider than 31" and no deeper than 27".

Thank you all very much for your time and I'd love to hear thoughts on what would be best for me.

[Triticum Agricolam]

Hello strreamix!  Unfortunately, no one can tell you what you are going to like the best, there are just too many variables and how people like their music to sound is very subjective.  What I can do for you is give you some more information so you can make a more informed decision.  

So you have three designs you are considering,  I call them design A (2.49 cu ft @ 30 Hz), B (2.78 cu ft @ 31 Hz) & C (2.375 cu ft @ 34.6 Hz).  The first thing you need to realize is there isn't going to be much difference in performance between the three.  Design A and B are so close that they will be completely indistinguishable from each other.  Design C has a little higher tuning, so you will get a bit more output around 40 - 50 Hz and a bit less below 40 hz, but we are only talking about 2 dB of output difference, which is only barely going to be noticeable, if its noticeable at all.  Here is a graph of the raw output of these three boxes so you can see what I'm talking about:

Design A is the green line, design B is the yellow line, and design C is the orange line.  I included your 50 hz 24 db low pass filter in the graphs.  Please note that cabin gain is going to boost the low frequency output of all of these enclosures significantly when they are in your vehicle so the actually frequency response you are going to get is going to be significantly different than what's shown here.  Cabin gain is somewhat unpredictable so its difficult to simulate it in software, however the graphs should accurately show the relative differences (or lack there of) in output between the different designs.  As you can see there aren't a lot of difference in the graphs.  Since you want good output down to below 30 Hz, I don't think design C is going to be what you want.  Between design A and design B, its not going to matter which one you pick.  

I looked at the port velocities you would be getting with the different designs.  Design A has the larger port and thus the lowest port velocities, so that would be the design I'd lean towards, but it won't make a huge difference either way.  

If you want to have more control over how your system sounds, I would highly recommend adding a DSP to you system.  A DSP can't make your system any louder, but it can give you quite a bit of control over the frequency response you will get.  Since you don't play your system at max volume a DSP should work quite well for you.  

[shredder2]

Design A gets my vote for the same reasons as stated above.

A smaller volume will lose a touch of output (less peaky) but I'm sure that was considered since you wanted a "SQish" response, and still some great lows.

 

Here's another I did, the guy wanted to cover the box face with a fabricated removable grille,  it's targeted for a little less power, a slightly flatter response with greater extension but really should be  pretty much the same once in-car.

Once again "A" gets MY vote... good luck!

 

[Joe X]

Here are the same plots as above using generic cabin gain to illustrate the low end boost of in- car performance:

 

Here's group delay (related  to sound quality) for the 3 designs, it's low enough on all designs so this should not be an issue, JL's reference design (in yellow) still gets lower than the alternatives:

 

 

Here's D also : 2.5 @ 32Hz just to show there's life beyond A, B; or C :

 

 

 

[strreamix]

2 hours ago, Triticum Agricolam said:

Hello strreamix!  Unfortunately, no one can tell you what you are going to like the best, there are just too many variables and how people like their music to sound is very subjective.  What I can do for you is give you some more information so you can make a more informed decision.  

So you have three designs you are considering,  I call them design A (2.49 cu ft @ 30 Hz), B (2.78 cu ft @ 31 Hz) & C (2.375 cu ft @ 34.6 Hz).  The first thing you need to realize is there isn't going to be much difference in performance between the three.  Design A and B are so close that they will be completely indistinguishable from each other.  Design C has a little higher tuning, so you will get a bit more output around 40 - 50 Hz and a bit less below 40 hz, but we are only talking about 2 dB of output difference, which is only barely going to be noticeable, if its noticeable at all.  Here is a graph of the raw output of these three boxes so you can see what I'm talking about:

Design A is the green line, design B is the yellow line, and design C is the orange line.  I included your 50 hz 24 db low pass filter in the graphs.  Please note that cabin gain is going to boost the low frequency output of all of these enclosures significantly when they are in your vehicle so the actually frequency response you are going to get is going to be significantly different than what's shown here.  Cabin gain is somewhat unpredictable so its difficult to simulate it in software, however the graphs should accurately show the relative differences (or lack there of) in output between the different designs.  As you can see there aren't a lot of difference in the graphs.  Since you want good output down to below 30 Hz, I don't think design C is going to be what you want.  Between design A and design B, its not going to matter which one you pick.  

I looked at the port velocities you would be getting with the different designs.  Design A has the larger port and thus the lowest port velocities, so that would be the design I'd lean towards, but it won't make a huge difference either way.  

If you want to have more control over how your system sounds, I would highly recommend adding a DSP to you system.  A DSP can't make your system any louder, but it can give you quite a bit of control over the frequency response you will get.  Since you don't play your system at max volume a DSP should work quite well for you.  

Thank you very much for your detailed input and explanation. I definitely understand it is tough to know what I will like, but to me the advice is very valuable just to hear more input. Everything is very clear from your post, I appreciate your time.

1 hour ago, shredder2 said:

Design A gets my vote for the same reasons as stated above.

A smaller volume will lose a touch of output (less peaky) but I'm sure that was considered since you wanted a "SQish" response, and still some great lows.

 

Here's another I did, the guy wanted to cover the box face with a fabricated removable grille,  it's targeted for a little less power, a slightly flatter response with greater extension but really should be  pretty much the same once in-car.

Once again "A" gets MY vote... good luck!

 

Thank you for your input Shredder, appreciate it.

32 minutes ago, Joe X said:

Here are the same plots as above using generic cabin gain to illustrate the low end boost of in- car performance:

 

Here's group delay (related  to sound quality) for the 3 designs, it's low enough on all designs so this should not be an issue, JL's reference design still is lower than the alternatives:

 

 

Here's D also : 2.5 @ 32Hz just to show there's life beyond A, B; or C :

 

 

Thank you Joe. In regards to your group delay post (I am unfamiliar with this term), which box would you recommend? I see above you say this is not an issue, but being an avid percussionist I very much want everything to be "in time" as much as possible. It looks like the red line box is the worst of the bunch in that regard, which box is that?

Also, you speak of life beyond A, B, or C, I'd be very interested if you had a box recommendation or design you would be interested in sharing with me or which of the 3 boxes you would personally pick if you had "my sound preferences".

Once again, thank you all for your time and responses.

[strreamix]

Just discovered that I made some errors in measurement / prediction on what would work in the trunk.

New max dimensions I could work with are: 15 H x 28 W x 23 D (yes the 1 1/2 inch from Box A is going to make a difference as I tested today with wood, half inch shorter would have made it inside and not require any changes to the trunk layout.

Not sure if there's a simple fix or I need a new design. 

My apologies for the error guys, the advice is all still very valuable.

 

edit: changed to 28 W for an extra inch of safety
 

[shredder2]

Available space measurements are always key... including what'll go thru the opening not just what'll fit once in there. It's not the 1st revision I've had to do due to this issue... lol... if you'd like a new design OP, email me and I'll see what I can come up with.

30-32hz tune around 2.5ft3 net IIRC... correct?

[strreamix]

10 minutes ago, shredder2 said:

Available space measurements are always key... including what'll go thru the opening not just what'll fit once in there. It's not the 1st revision I've had to do due to this issue... lol... if you'd like a new design OP, email me and I'll see what I can come up with.

30-32hz tune around 2.5ft3 net IIRC... correct?

Yes, the space is actually available but it would require me to level out the floor of the trunk somehow (its uneven on the sides) and I really don't want to add more weight to the trunk.

 

Emailed

[Joe X]

So here is option "D" as in the plot I left you above and within your max dimensions, power: to sub rated, amp subsonic filter to 27Hz, minimum port clearance 2 1/2", figure is just an assembly guide:

NOTE: If building outside you need to build a cardboard dummy box to test fit in it's way inside.

 

 

 

Group delay will be as in the orange curve above if you are curious to know.

[strreamix]

On 11/2/2018 at 3:04 AM, Joe X said:

So here is option "D" as in the plot I left you above and within your max dimensions, power: to sub rated, amp subsonic filter to 27Hz, minimum port clearance 2 1/2", figure is just an assembly guide:

NOTE: If building outside you need to build a cardboard dummy box to test fit in it's way inside.

 

 

 

Group delay will be as in the orange curve above if you are curious to know.

Thank you Joe X, I appreciate it.