Help with trunk wall design for SP4 v2+15 on two DC 2ks

[Joshdashef 0]

Lots of info in this post, but I will bold the important bits and questions I have. Feel free to read it all but my main questions stem from box design perspectives. I can create another thread about electrical if needed so try to limit the discourse to enclosure related topics, cheers!! 

 

After much trial and error the only reasonable design choice left is to go for a slot port. I have tried and tried to fit an aero port however I have come across two problems. 1. I have to make my box far too large for my power >5 cubes net or 2. my port becomes feasibly too long to fit inside my box or outside (>28") along with airspeed issues with an 8 inch port (50 ish square inches of port area).

 

On the other hand after dicking around in WinISD and Excel I have come across what I feel is a good starting point I can work with and shrink down as necessary albeit at the expense of port area. 

 

Background Information:

• My desired tuning is around 32 Hz and I will be powering the SP4 15 v2+ off two DC 2ks gain matched (not strapped...) P600x4 on mids/highs. 
• Electrical if your curious will be Mechman 240 A, D5100R (under hood), Titan 8 RSV 5S, XS SB1000-31, and maybe an extra D3400 if it fits (but probably not). Will experiment with bypassing under hood battery eventually to gauge voltage drop. 

 

Summary so you can skip the lower half if you want

• f3 point at 27 Hz, lose cone control below 25.5 Hz on 4k input, so infrasonic filter at 27 Hz and low pass filter around 80 or 100 Hz.
• peaks at 34.5 Hz with 4 cubes net box tuned to 32 Hz 
• with a port (14.5 x 5.25) port area equal to 76.125" and basically 19 inches of port per cubic foot.  Oh the port is 43.84 inches long too. 
• with either 2 or 3 baffle design, any opinions on what leads to a sturdier box? more baffles or more internal bracing?

 

Any opinions on the box design so far? My aim is for a daily build, not a SPL hunter so I suppose bandwidth would be better than a higher peak but I think a hybrid approach might be beneficial for my case. Bandwidth and Peak. 

 

 

 

Rest is just pics of my excel sheet and WinISD graphs

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Volume Calculations

• Here are my volume calculations in Excel. H, W, and D all account for wood thickness under "number of exterior walls" so when it says 2 it means the sides of the box, when it says 4 under depth it means the back of the box and a triple baffle. (I am debating on having a double baffle with more internal bracing or just a triple baffle with less internal bracing, opinions?)

 

WinISD Graphs:

• Here are my WinISD graphs for a box that has an interior volume of 6.48 before displacements (for sub, port, bracing). After these displacements I have 3.96 cubes net.

• The f3 point is at essentially 27 hz and have the highest peak at 34.5 hz. 

 

• Given a power input of 4000 watts my cone remains under its xmax until 25.4hz 

 

 

• Here is where it gets interesting. Air velocity. Now if I use input power of 4000 watts I see up to 32 m/s. However, if  I only use 60% of my two amps ratings (2200 watts) then my air velocity is 23.5 m/s. 

 

 

Any opinions on the box design so far? My aim is for a daily build, not a SPL hunter so I suppose bandwidth would be better than a higher peak but I think a hybrid approach might be beneficial for my case. Bandwidth and Peak. 

 

I would set an infrasonic filter at 27 hz to avoid any loss of cone control on lower songs. 

 

Edited April 17, 2020 by Joshdashef