2x18 Cabinet Help

 

New member
Username: Crother316

Post Number: 1
Registered: May-11
Hello, I am new to this but a am attempting to make a 2x18 subwoofer cabinet that I can use for my bass guitar. I am going to use eminence sigma pro 18a-2 speakers.
power rating: 650watts rms; 1300watts music program
resonance frequency (fs): 28Hz
usable frequency range: 41Hz-2.4kHz
mechanical Q (qms): 8.28
Electromagnetic Q (qes): .30
Total Q (qts): .29
Compliance equivalent volume(Vas): 441.2 liters
peak diaphragm displacment: 695cc
Maximum linear excursion(Xmax): 6.1mm

I play alot of music that I want deep, booming, massive, loud, clear, Bass.
I have used a few online calculators for the enclosure and and came up with...
Height: 28.5 in.
Width: 46.1 in.
Depth: 17.6 in.
This makes the total volume of the enclosure 379.8 liters or 13.4 Ft cubed. the recommended enclosure volume is 3.3-7.5cu. ft for one so im guessing 6.6-15 cu ft. for 2?

My biggest trouble is tuning the ports. I have heard that the best balance between SPL (getting loud as possible) and SQ (sound quality) is about 32Hz so here are a few calcuation a i came upon on the web and said the minimum port diameter size should be 8.73 in. which seems a little big to me.....
but if i tried two 6inch ports the vent legths would have to be 6.71 in. in length. why is it the less quantity of ports & smaller diameter ports need to be shorter?

my questions are...
what kind of porst should i use?
how should I brace the inside for stability?
Will I need high pass or low pass filters? or crossovers?
should I have a fabric on the inside?
should i make the box the maximum manufacture recomended }volume(15 cu. ft.) to increase deepness?
should i consider bandpass?

i am looking for rediculously deep, clear, loud, massive booming bass, for reggae, hip-hop, rock music. any help or recomendations would be greatly appriciated. thank you.
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 391
Registered: Oct-10
The port area is the breathing room, and the port length changes the tune, think of it as more port length = more port being utilized. The longer the port the longer the tune. The only ways to get a lower tune is to either increase box volume or use less port area.

Use slot port. Brace with .75" MDF or a 2x4. Try to use 45 degree corners, and sand the edges so air travells smoothly over them. High and low pass yes, just like any other instrument amp, those are crossovers. Fabric on the inside is to make the box perform larger than it really is, and you don't need it. The bigger the box, the lower the tune. Do the calculations, set a goal, and then decide the box volume. Maybe you'll need that space to get your low tune with enough port area (stay to within 10 to 15 inches of port per cubic foot of volume). Don't consider bandpass, you won't need it, nor sound experienced enough to toy around with two different boxes as one, those are hit & miss.

I would do 15 cubes @ 20 Hz, it would be nice as a HT system too, and it could play any music without being damaged.

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