Cab tuning assistance reqd. please

[MoonBassAlpha]

Ok, I'll try not to waffle on too much, but here's the background:
About 25 years ago, I got a nice new Electrovoice EVM12L for a bargain price and put it in a little cabinet to use as a bass and guitar extension cab.
It sounded fine for guitar but was always a bit farty for bass.
I looked at it yesterday and realised that there was no gasket between the speaker and baffle (for all these years!) so I fitted one and bingo! no farty even on a 5 string.
So now it is capable of making a decent sound, I think it could use tuning.
Internal dimensions are 38x35x19 cm and there is a 3" hole in the baffle, no porting (hole for a tweeter?)
Given the smallish volume, should I block the hole off, or add a port tube to tune the cab? There seems enough top end to not need a tweeter.
Any suggestions re tuning length etc. welcomed, cheers.
Jules

[Mr. Foxen]

Find some pipe to fit in the hole and try a few lengths, or sleeve two bits so they are telescopic and try a few tunings.

[Bill Fitzmaurice]

Add a four inch duct to the port.

[MoonBassAlpha]

Thank you very much Bill, much appreciated. And thanks Mr. F, good idea, I should have thought of that one!
How is the cab volume?, just about enough? (not that I can do anything about it anyhow!)

[MoonBassAlpha]

Just found out a tennis ball tube is about the right diameter!
I'll keep you updated once I've fitted it.