What's new

Port length for shiva? (1 Viewer)

DorianBryant

Screenwriter
Joined
Apr 14, 2004
Messages
1,555
I built a 85 liter Shiva with a 4" port. I must have ordered the wrong port from Parts Express or they sent me the wrong one. The one I received is 11.5" totall length and flared on both ends. The numbers i came up with indicate the port length should be 13.87" to tune to 20-22 hz.

Does this sound right? I tried the 11.5" port but it seems to be a bit boomy.

Should i get the longer port? I tried to plug the port but it really effects the output. It somewhat tighter though.

What length 4" port should i be using?
 

Stephen Hopkins

HW Reviewer
Senior HTF Member
Joined
Jul 19, 2002
Messages
2,604
Sounds like they sent you their clearance 3" x 11.5" port. I would send it back and have you send the correct 4" port because that's what you paid for or refund you the difference. That said, the 3" x 11.5" port is giving you a tune of around 21.5hz which should give a prety gradual rolloff w/ an F3 of around 25hz. What you're perceiving as boominess is probably due to room peaks or nulls. I would experiment with placement to see if you can minize this, or it may be neccesary to add some kind of EQ to combat the peeks.
 

minhG

Stunt Coordinator
Joined
May 6, 2004
Messages
82
just to be clear, is that 11.5 with the flares or only the center section?
 

DorianBryant

Screenwriter
Joined
Apr 14, 2004
Messages
1,555
Actually it is a 4" port with flares on both ends and a total length of 11.5".

I have gotten conflicting results from a couple of different programs. Thought I would pose the question to those in the know. Since the hole is cut, what length 4" port should i use to get down in the 20's? Does 13.87 sound reasonable?

I may look into an EQ. Most seem to be using the BFD.

I was also using a 120watt RMS amp which may or may not have a bass boost. I sold it and will be getting a 250 watt amp from PE without a boost.

when i demoed the sub upstairs in my living room i played around with placement but was getting some serious resonance from the windows. I want to get the port length and amp straightened out first.

Thanks for the help.
 

Ryan Schnacke

Supporting Actor
Joined
Feb 5, 2001
Messages
876


Not particularly. I assume you mean 13.87 inches TOTAL (including flares). This would get you to around 26-27Hz tune with about 1.5dB bump around 40Hz.

In 85L even using the full 18" length of the 4" flared port you'll only tune it down to about 23-24Hz. So I'd want to use at least this much. And perhaps you could mate some other 4" tubing to the flares to get more length. You'd need 25-26" total to achieve the "Adire alignment" and get 20Hz tune.
 

DorianBryant

Screenwriter
Joined
Apr 14, 2004
Messages
1,555
yes, 13.87" inclusing the flares. 11.5 seems just too short. hopefullt this, and a better amp will allow me to ge the performance I am looking for.
 

Users who are viewing this thread

Sign up for our newsletter

and receive essential news, curated deals, and much more







You will only receive emails from us. We will never sell or distribute your email address to third party companies at any time.

Latest Articles

Forum statistics

Threads
357,029
Messages
5,128,989
Members
144,279
Latest member
acinstallation402
Recent bookmarks
0
Top