Conical Reflex Ports?

[Guido]

When I want to work with conical reflex ports, how I calculate the Length?
Is it the air volume inside an reflex port that makes the helholtz resonance?

[Tom Loizeaux]

I asked this question when I was trying to come up with port measurements when faced with tuning a bass cabinet with a slanted port. Everyone I asked didn't know. I was told there weren't formulas for slanted ports!
I wound up doing sweeps with a variety of port restrictions until I came up with a size and flare that tuned the cabinet to 40 Hz and sounded nice.
I am curious to see if someone offers you get a formula for slanted ports!

Tom

[whgeiger]

Originally posted by Guido
When I want to work with conical reflex ports, how I calculate the Length?
Is it the air volume inside an reflex port that makes the helholtz resonance?

G,

To a first approximation, treat as a cylindrical port of radius [r]=([r1]+[r2])/2. Use [r] to calculate end corrections also. For optimizing the port contour see the referenced article.

Regards,

WHG

Title: Maximizing Performance from Loudspeaker Ports
Author: Alex Salvatti
Author: Allan Devantier
Author: Doug J. Button 19
Publication: AES-J, Vol. 50, No. 1/2, p. 19 (Jan/Feb-2002)
Abstract: The low-frequency performance of a loudspeaker is significantly enhanced by the use of tapered ports, but there are numerous trade-offs involving the size of the port and the input and output tapers. Design issues include the effectiveness of heat transfer, amount of turbulence created, air velocity, smoothness of the taper, symmetry of the two tapers, effective mass in the port, and the contribution to the frequency response. Suggested design rules are based on extensive empirical studies.

[whgeiger]

Originally posted by Tom Loizeaux
I asked this question when I was trying to come up with port measurements when faced with tuning a bass cabinet with a slanted port. Everyone I asked didn't know. I was told these were not formulas for slanted ports!
I would up doing sweeps with a variety of port restrictions until I came up with a size and flare that tuned the cabinet to 40 Hz and sounded nice.
I am curious to see if someone offers you get a formula for slanted or flared ports!

Tom

TB,

Use average tube length and radius, and then treat as if normal to the baffle to calculate end corrections. As usual, be prepared to adjust tube length for tweaking system resonance. For port optimization see reference given in earlier post.

Regards,

WHG

[Guido]

Thanks for help!!

[Claus K]

Hi Guido,

I have the program "AJHORN" which allows to simulate that. No sure how accurate it will be in that case but if you want me to run some simulations for you I could do that.