Speaker build, port tuning question

[subynube]

I am getting ready to build Zaph's ZD3C, which is the center channel version of the ZDT3.5.

http://www.zaphaudio.com/ZDT3.5.html

I will be building this in the 1.0 cubic foot parts express enclosure. He has 2 options for the center channel, one using the SEALED parts express cabinet, and the other PORTED version of a DIY built cabinet. I am wondering why he did not build the Parts express pre-fab cabinet vented.

I have a set of Nat P mains, and they are ported and tuned to about 34 Hz, using a Precision 2" flared port, ~ 9" long using the parts express pre fab cabinet, as stated in the Nat P build in the missions accomplished section. Is there a reason why I can't go ahead and do this for the center channel ZD3C build that I am doing now in the same pre-fab cabinet?

Thanks all!

[Not2Evil]

Sealed enclosures are rather forgiving as far as slight changes in enclosure size.

Ported enclosures are tuned to a specific frequency. Changing the size of the box, or the port will change the resonant frequency. It's the same as adding or removing water and blowing across the top of a pop bottle.

Zaph said to use a 1.38 cubic foot custom built ported enclosure or a 1 cubic foot sealed. I'd follow his advice to a T.

[ThomasW]

I am wondering why he did not build the Parts express pre-fab cabinet vented...... Is there a reason why I can't go ahead and do this for the center channel ZD3C build that I am doing now in the same pre-fab cabinet?

Where would you put the port?

[subynube]

Where would you put the port?

I would put the port outlet in the back of the cabinet, in the center of the cabinet.

[subynube]

Sealed enclosures are rather forgiving as far as slight changes in enclosure size.

Ported enclosures are tuned to a specific frequency. Changing the size of the box, or the port will change the resonant frequency. It's the same as adding or removing water and blowing across the top of a pop bottle.

Zaph said to use a 1.38 cubic foot custom built ported enclosure or a 1 cubic foot sealed. I'd follow his advice to a T.

Thanks.
The reason that I am inquiring about porting Zaph's design is because the Nat P's use the same mid drivers, in the same enclosure.

[subynube]

Thanks so far for the responses. I'm going to build this speaker this weekend. Any other input?

[ThomasW]

The only reason to port any of these is if you aren't running a sub. If you have a sub don't bother porting since none of these designs qualifies for the 'large' speaker setting in a receiver.

[subynube]

The only reason to port any of these is if you aren't running a sub. If you have a sub don't bother porting since none of these designs qualifies for the 'large' speaker setting in a receiver.

Thank you very much Thomas. I am definately running a sub, and will probably call this a "small" speaker. However, this is the center channel, and was concerned that maybe this might be treated a little differently. Would you still consider this a "small" speaker in the center channel mode?

[ThomasW]

My center channel has 2-15" drivers and I still run it as small so the lowest frequencies are sent to the IB sub.

[subynube]

My center channel has 2-15" drivers and I still run it as small so the lowest frequencies are sent to the IB sub.

Showoff :W

Thanks for all the input!

[ClosetSciFiGeek]

Build the enclosure yourself. The ported on looks so much cooler than the sealed one.

[ThomasW]

Build the enclosure yourself. The ported on looks so much cooler than the sealed one.

His only options are rear mounted ports, so they'd only look 'cool' to someone sitting between the wall and the rear of the box..

[Not2Evil]

There are different opinions, but it seems like the concensus is that you don't need as much bass from a center. It would seem like the 1 cu ft sealed cube would do what you need.

If you really feel the need to port it, you're safest bet is to build it as designed in the 1.38 cu ft box.

I've been struggling with port issues in another thread, but I believe if you port in a smaller box than designed, you should adjust the port diameter and length, tuning the box to a higher frequency. You may actually hurt yourself as far as bass extension vs a smoother roll off. Run some models and see what you come up with. The price is right, it's free!

I am curious though. The Zaph center had two front firing ports, and it sounds like you would have one rear firing port. Did you have a specific port diameter and length planned?

[Bent]

Thomas, you're gonna hate me, but this pdf shows 2 front mounted ports on the ZD3c

[ThomasW]

There are different opinions, but it seems like the concensus is that you don't need as much bass from a center. It would seem like the 1 cu ft sealed cube would do what you need.

I am curious though. The Zaph center had two front firing ports, and it sounds like you would have one rear firing port. Did you have a specific port diameter and length planned?

He doesn't need the port nor does he necessarily want one. Standard XO point for sub out on a receiver is 80Hz. So who cares if the center has a port tuning in the 30Hz range since it's useless....

Also there's a better potential match between the mains or center and a sub since a sealed box has a more advantageous natural roll-off than a ported box

Thomas, you're gonna hate me, but this pdf shows 2 front mounted ports on the ZD3c

I'm aware of that so is the OP, and he's using smaller PE assembled box

[Doug Fraser]

Here is a link to a member that built the 3.5

http://www.htguide.com/forum/showthread.php4?t=30793

Doug

[Bent]

Ok - my appologies.
I didn't read the whole thread well enough first - and once again, shot my mouth off.