Shiva Help Please !!!

[mkellym]

I would like some advise/help on tuning an enclosure I have built for the Shiva MKIII. The box is 6138cu inches/100.584 liters. I am using a 250w plate amp. The driver is mounted verticaly, and the port will be firing downward on to a deflection base. I will be using it mostly for movies, but want it to play music as well as possible, mostly modern jazz/classic rock/country. The room it is in is about 16' x 17' with 10' ceilings, which vault up to about 14'. There is no wall on the opposing wall of the sub. Iam not sure as to use a 3" or 4" port. I understand that if I use a 3" port, I can keep the space between the port outlet and the deflection plate a little closer? If this is true, and the 3" port will work well, then I would prefer to use the 3". My question is what freq. should i tun to (21-22hz?) and then what would be the port dimensions. Thank you for any and all help.

Sincerely,
Matt Kelly
mkellym@aol.com

[Pete Mazz]

21" x 4" port would tune to ~20 Hz. 3" is a little small, unless you use a flared port.

Pete

[FrankDIY]

Even 4'' will be probably too small. I always use 4'' and if I drive the sub hard, I hear the port noise.

[leadbelly]

Try it with no port first. I have a Tempest + 250W amp. Even in a 12' x 33' room, sealed 165L, downfiring on carpet, I only turn up the gain on the sub amp to 50% to balance my speakers. You can always add a port later.

[FrankDIY]

Originally posted by leadbelly
You can always add a port later.

ported box have a bigger volume so that's not a good idea. Going from ported to sealed is less error prone.

[kelticwizard]

Originally posted by François



ported box have a bigger volume so that's not a good idea. Going from ported to sealed is less error prone.

Generally, when a speaker is put into a ported box, the box is considerably larger than when the same speaker goes into a sealed box. The ported speaker will give much more bass in it's new size.

However, this speaker in a 100L box just happens to fit into a range where you can go either ported or sealed. Most subs, you have to decide one way or the other.

The red line is the speaker in a closed box of 100L.

The blue line equals the same speaker with two 3" flared ports tuned to 22 Hz in a 100 L enclosure. The ports are 19 5/8 inches long.

The port flares are available from Parts Express or Madisound. Maybe even Adire-not sure on that one.