Port bracing question

[JCsAudio]

Save yourself some queef and don’t mess with the grinder or you might get chewed to pieces, lol.

[Surfer J]

The sub is a Stereo Integrety HST-15. I am tuning to 25 Hz. The slot port needs to be about 64” or a 6” round port needs to be about 55”. The box is 16” wide and 26” deep. I can go as tall as needed.

[Grinder]

The sub is a Stereo Integrety HST-15. I am tuning to 25 Hz. The slot port needs to be about 64” or a 6” round port needs to be about 55”. The box is 16” wide and 26” deep. I can go as tall as needed.

I think 64" and 55" are too long. Not sure what the outer practical limits are (or why), but I seem to remember reading somewhere that ~48" is the limit.

A shorter port (at the same 25 Hz Fb) would require reduced port area and/or increased cabinet volume.

How much power do you expect to be using? Port area requirement is largely based on power.

How have you arrived at your required port area? I'd be happy to model it for you.

[Surfer J]

I used a couple box building programs and that is the port length that was recommended.

[Surfer J]

I will be running 3000 watts. I have never designed a ported enclosure before. I have no idea how to calculate port area or length. Only what I could find online. If you would model it for me I would be very grateful.

[Grinder]

The sub is a Stereo Integrety HST-15. I am tuning to 25 Hz. The slot port needs to be about 64” or a 6” round port needs to be about 55”. The box is 16” wide and 26” deep. I can go as tall as needed.

Your numbers look sound. Looks like you're basing this on the recommended 2.0 ft^3 @ 2000 watts. If you really want 119 dB or thereabouts, I'd recommend increasing cabinet volume, for a shorter port. If you haven't done so already, you might look into port resonance, as it seems that the longer the port, the more that audible port resonance can become an issue. If you can give up some output, you can simply decrease port area to reduce port length.

[Grinder]

I will be running 3000 watts. I have never designed a ported enclosure before. I have no idea how to calculate port area or length. Only what I could find online. If you would model it for me I would be very grateful.

You done good.

I've modeled it in WinISD ( http://www.linearteam.org/ ) based on SI's 2000 W RMS spec ( https://stereointegrity.com/product/hst15-15-subwoofer/ ).

I always use this calculator for flared ports (looks like you might have too): http://www.psp-inc.com/tools2.html

[Queef]

SurferJ,
Which ohms ? Dual 1ohm or 2ohm ?

[Grinder]

<edit> Based on 2 DVC @ 1 ohm

2.0 ft^3, 25 Hz, 6" vent tube x 57" @ 2kW = 32 m/s peak vent velocity

22 m/s or less is said to be ideal for maximum output, as higher velocities lead to vent compression.

My limited experience suggests that velocities as high as 42 m/s (or higher?) produce no port noise/chuffing in straight flared vents such as these: https://www.parts-express.com/brand/precision-sound/285

FWIW (in my amateur opinion), I doubt that output suffers appreciably at 42 m/s vs 22 m/s.

2.5 ft^3 drops vent length to 45" while slightly increasing (SPL) and lowering (Hz) the mild ~30 Hz hump.

3.0 ft^3 drops vent length to 37" while further increasing (SPL) and lowering (Hz) the hump, to a total of +3 dB at 29 Hz.

[Queef]

Awesome Grinder !