Port Placement

[Thawach]

Originally Posted by Helmuth

@ Thawach,

As I explained earlier for a good functioning port it is important to have a good coupling with the woofer.

You can place the port any where you like, the loudspeaker will always make sound. When you want the optimal result place it near the woofer.

Helmuth i think that why u did not understand my english in thai version. the last post of sreten. the port is away from the woofer about 2-3 inch on pdf file. u meant that the port away about 2-3 km from the woofer?

[Scott L]

The better choice for placement is directly behind the tweeter. You'll want to
place sound absorbent material on the back of the cabinet wall directly behind the woofer. Ports get a baad raap because they are often too small, and placed incorrectly. The function of a port id the load the woofer at a certain frequency, but NOT allow mid range information to escape from same said port. In a little speaker box like that, it's best located on the back. If it was a larger box: a dedicated woofer/ or sub, then the best location would be on the front panel.

[Richard Ellis]

I always thought woofer placement and port placement on say....the front of the baffle should be odd multiples.......The thinking is that even multiples makes for reinforcement/stacking of mode points within the enclosure.
Not sure how to say it.........

__________________________________________________ Rick.............

[Scott L]

Originally Posted by Scott L

The better choice for placement is directly behind the tweeter. You'll want to
place sound absorbent material on the back of the cabinet wall directly behind the woofer. Ports get a baad raap because they are often too small, and placed incorrectly. The function of a port is to the load the woofer at a certain frequency, but NOT allow mid range information to escape from same said port. In a little speaker box like that, it's best located on the back. If it was a larger box: a dedicated woofer/ or sub, then the best location would be on the front panel.

[Syzygies]

Ok, after getting a port education in a different thread, I've decided to port my Zaph Audio ZA-SR71 kit build. (The complete kit shows "out of stock" at Madisound because their enclosures don't have the port hole.)

Everything I've read says that one wants to stay clear of the woofer, but exact placement can vary by a small fraction of resonant wavelength. Yet Zaph's port placement is so close to the top of the speaker enclosure that one can't place a full thickness of acoustic foam between the port and the top. Move the hole down 1/2", not even to directly behind the tweeter, and there's room for 1" acoustic foam.

Enclosure drawing with baffle layout

By training I try to be very sensitive to the slightest anomaly. That is for example how impossible-to-find bugs get discovered in computer programs. Here, it disturbs me that, without explanation, Zaph notes that the port is too close to the top for full insulation, but he doesn't move it down. I can't find any supporting explanation that a half inch would matter.

Any ideas?

[fatmarley]

I always thought the port placement on the Royd minstrel was a good idea - They were ported in the side (I'm not a big fan of ports though)

[weltersys]

Originally Posted by Syzygies

By training I try to be very sensitive to the slightest anomaly. That is for example how impossible-to-find bugs get discovered in computer programs. Here, it disturbs me that, without explanation, Zaph notes that the port is too close to the top for full insulation, but he doesn't move it down. I can't find any supporting explanation that a half inch would matter.

Any ideas?

The port is close to the top wall of the cabinet, which lowers tuning slightly compared to the same port a half inch further down.

Since the port is flared, the proximity difference would make less difference than it would with a straight tube port.

At any rate, moving the port down a half inch would probably raise the tuning by less than 1Hz, not a big deal.

The type and quantity of fill would have more affect on Fb than moving the port 1/2".

That said, 1" fill compressed a bit by the port flares won't make a bit of difference, as long as a bit of fill by the flare is removed to keep the flare clear of fill.

[Syzygies]

Originally Posted by weltersys

moving the port down a half inch would probably raise the tuning by less than 1Hz, not a big deal.
...
as long as a bit of fill by the flare is removed to keep the flare clear of fill.

Great answer, thanks, just what I wanted to understand. I had been thinking of sculpting the foam in that area.

[liasom]

Originally Posted by Syzygies

Ok, after getting a port education in a different thread...

Curious, Which thread? Was thinking it would be a good read.

[Syzygies]

Originally Posted by liasom

Curious, Which thread?

ZAPH ZRT 2-way sealed cabinet option
The ZRT woofer has much lower bass sealed, than for the SR71. There's also excursion...