Ported Home Theater Sub Build Procedure - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 4 Old 05-14-13, 04:03 PM Thread Starter
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Sub Icon Ported Home Theater Sub Build Procedure

Since getting hooked on all the amazing sub build threads here, I've tried to slowly acquire a 'procedure', if you will, of how to successfully build a HT-oriented ported sub from info found here and all over the interwebs. I figured I would put this out here and hopefully get more or less a group consensus on what does and doesn't work when building a ported HT sub.

I like finding tips scattered here and there from the experts, but thought a beginners (such as myself) guide would be useful. Let me know if it's not! Or if it's totally wrong! Or if this is all common sense! Feel free to let out an exasperated sigh of consternation at the end of my incoherent ramblings!

It is utterly incomplete, I know, but I hope to gain as many ideas as I can so when I finally get the chance to have my own build, I will be confident I worked to best of everyone's ingenuity, expertise and knowledge.

I hope to maybe see enough input to put together other quasi-procedures for other alignments as well; sealed, horns, IB, etc...

Ported HT Sub Build Procedure

1. Choose Driver - (Low Fs (<25Hz), Xmax>15mm, >20mm ideally), Qtc of 0.70 optimal. >0.70 is "boomy", <0.70 for music

2. Decide on VC config. Dual vs single - 1 ohm? 2, 4, etc. Reference HTS Driver Wiring Diagrams

3. Port Sizing ROT – Driver Size Dia (in)/Min port Dia (in): 8/3; 10/4; 12/5; 15/6; 18/8. Or - port area should be <= 30% of driver's Sd.

4. Quoting Mike P, “Model Driver in WINISD Pro; tune <=15Hz and there is no need for HPF. Port speed <=20 m/s. WinISD defaults a specific box size depending on what you select from the Available Alignments tab. From there you adjust the box size, tuning frequency, power input, and in the case of ported a HPF and port size. You switch back and forth between the SPL, Port Air Speed, and Cone Excursion graphs and make adjustments until it all comes together for that specific driver.

For a HPF click on the EQ/Filter tab, Click on Add and the Filter Editor pops up. For Filter Type select Highpass from the drop down menu. Leave the Subtype as Butterworth. Leave the Order as 2, the Q of 0 and change the Cutoff to the frequency of the amp. For example the Bash 500 is 18 Hz.

When modeling check the cone excursion and port air speed. You can model the same driver more than once so you can do comparisons."

5. Determine Target Net Volume through modeling.

6. Interior port openings shall be >= port diameter away from any wall.

7. Bracing should be asymmetrical to eliminate multiple panels resonating.

8. Subtract internal bracing, driver, and port volumes to reach Target Net Volume ±5%.

9. Determine Panel List – remember to account for double or triple thick baffle.

10. Use cut list program to determine number of panels needed and cut list for panels.

11. Buy panels at ? Have them do rough cuts that allow transport of stock.

12. Perform final cuts for panels and bracing.

13. Cut holes for driver(s), port(s) using router with jig and several passes or jigsaw (router preferable); drill driver mounting holes and glue T-nuts in place.

14. Dry fit everything.

15. Glue panels/bracing using brads/screws and/or clamps to hold panels in place. Use square clamps to keep everything lined up - beware brads/screws on edges that will be rounded over.

16. Seal, prime, or paint interior to mitigate off-gassing of MDF. MDF off-gasses, right?

17. Caulk all seams for air tightness - allow 3 (?) days minimum cure time for silicone caulk before driver installation or testing.

18. Install Port(s); Grill (optional) – AT cloth, woven wire, wire mesh, wire cloth for the grill? Get from Grainger, MSC, or McMaster Carr.

19. Roundover edges. Reduce standing waves with roundovers on baffle edges? (radius >= thickness)

20. Fill all holes, gaps, dents, etc. (with Bondo? Wood filler?) and sand smooth all edges/faces.

21. Seal and prime; prime edges multiple times in addition to multiple priming of all surfaces with sanding in between.

22. Paint; multiple coats with sanding in between or do liner coating or other covering and skip 23.

23. Clear coat (4 coats, wet sand between coats, then polish).

24. Install Batting: ROT - 1/2 to 1 lb polyfil per cu ft as built box volume.

25. Install Binding Posts and necessary internal wiring (12AWG inexpensive and more than capable).

26. Install Driver with gasketing (closed cell window weather stripping).

27. Setup, EQ, etc. (Entire procedures on their own!)

Last edited by BD55; 05-14-13 at 04:26 PM. Reason: .
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post #2 of 4 Old 05-15-13, 05:39 AM
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Re: Ported Home Theater Sub Build Procedure

That's a comprehensive list you have. A couple of points though.

1. Since this is for ported then QTC is irrelevant and would apply to a sealed build.

3. Ideally port air speed should not exceed 26 m/s peak or 18 m/s rms.

5. Determine Target Net Volume and tuning frequency through modeling.

16. Off gassing is non issue for MDF.

18. Allow clearance for cone excursion when installing a grill.

19. Not required.

24. Polyfil applies to sealed enclosures.
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post #3 of 4 Old 05-15-13, 07:59 AM Thread Starter
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Re: Ported Home Theater Sub Build Procedure

Awesome, thanks Mike!

As for the polyfil, some type and amount of batting or fill in ported enclosures is desirable, right? I know I see quite a few ported builds put something in (eggcrate, fiberglass (which I don't think is a good idea for a ported design anyways), etc.)
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post #4 of 4 Old 05-15-13, 01:52 PM
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Re: Ported Home Theater Sub Build Procedure

Some say lining a ported sub works, other say it does nothing. I always do.
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build , home , ported , procedure , theater

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