[wildfire99]

I'm rebuilding the cabinets for my 1801 HT setup, and I had a question about the port. This is the old plan, mind you, with the (from what I could find out) 5" long, 2" PVC port (non flared).

I went into Unibox and did a quick model on the W18E001 woofer in a 22l box, and it said to use an 11" long port for optimum extension. That sounds a bit odd to me, considering the plans call for a 5" long port, and people here seem to be interested in making the thing even shorter! Of course, the longer port seems to show airspeed issues down low, but then so does the 5" to a lesser degree (and I don't recall ever hearing chuffing on them before).

Dave (or anyone), do you have any input on the advantages/disadvantages of using a longer port? My room has VERY little bass reinforcement, due to size.

Of course, if the flares make a huge difference I guess I could order some.

[David Ellis]

I went into Unibox and did a quick model on the W18E001 woofer in a 22l box, and it said to use an 11" long port for optimum extension. That sounds a bit odd to me, considering the plans call for a 5" long port, and people here seem to be interested in making the thing even shorter! Of course, the longer port seems to show airspeed issues down low, but then so does the 5" to a lesser degree (and I don't recall ever hearing chuffing on them before).

This is a very keen insight.  My answer to the 11" port is twofold.

1.  Folks like more bass bump from their ports, so shoter is preferrable.

2.  The cabinet WILL soak/transfer bass in the 30-40hz zone.  There is tremendous energy in these low frequencies and some of this energy will travel directly through the cabinet walls.  This energy is "lost" from a port-reinforcement perspective.

I also don't hear any chuffing from the 5" non-flared port.   It was a good port, and very inexpensive.  The new port is @ $10x more expensive and does the same thing (essentially).  

A longer port will sound leaner due to a lower frequency bass reinforcement from the port.  A shorter port will sound boomier due to a higher frequency bass reinforcement from the port.  I suggest you... experiment.  If you accidentally cut the port too short, you can always tape it back-together.  Sure, this will look cheesy, but it'll be inside the cabinet.