Any problems with this design?

[IonSQL 10+ year member]

That calculator is too easily manipulated... stick with 14-16sq in per cf or usable area as a good rule of thumb...

 

[dan5505 10+ year member]

Here is my previous design. It has a port area of 78 square inches. So you guys think i should go even smaller?

 

[dan5505 10+ year member]

I think i see the flaw in my calculation now. The calculator on this site is for minimum USABLE port area. http://www.carstereo.com/help/Articles.cfm?id=31

 

[BrianChia 10+ year member]

Too much port area results in bad sound quality. You will lose sound through the port itself, and it starts to blur the line between a ported design and a transmission line design. The port should only produce sound at the tuned frequency and sound shouldn't leak out at other frequencies or you will have "muddy" bass. I would choose your original design but reroute the port so it makes as few turns as possible (ie. run it lengthwise against the back wall of the box).

 

[dan5505 10+ year member]

ok, cool. So something like this one then. Do you think ill be ok with a port area of 78 or do you guys think i should go smaller.

 

[Crodski 10+ year member]

if u dont mind me asking....what software are u using?

 

[dan5505 10+ year member]

if u dont mind me asking....what software are u using?

These were all modeled in solidworks.

 

[Hintzyboy 5,000+ posts]

Too much port area results in bad sound quality. You will lose sound through the port itself, and it starts to blur the line between a ported design and a transmission line design. The port should only produce sound at the tuned frequency and sound shouldn't leak out at other frequencies or you will have "muddy" bass. I would choose your original design but reroute the port so it makes as few turns as possible (ie. run it lengthwise against the back wall of the box).

Umm... What???

The port has a peak in output at the tuning frequency, but it produces sound at other frequencies. Otherwise, there would be no point in building a ported box.

 

[dan5505 10+ year member]

With the top on....

so... safe with 78 sqin port area?

 

[BrianChia 10+ year member]

Umm... What???
The port has a peak in output at the tuning frequency, but it produces sound at other frequencies. Otherwise, there would be no point in building a ported box.

The port should produce frequencies from the air resonating within the port which peaks at the Fb. However, it shouldn't produce any sound from the backwave of the speaker itself. The backwave of the speaker should be damped within the main chamber and it should produce port resonance at the tuned frequency. The actual port should not be used to damp the backwave of the speaker. That would be a transmission line design (which requires stuffing within the line to dampen any harmonics). With too much port area and no stuffing it would be like building an open baffle speaker with shitty sound. Also a larger port causes phase cancellation issues and group delay which further affect sound quality.

Dan, 78 in^2 should definitely be plenty enough for 1 single 15". I would go with the deflectors in the corners, though, and use a roundover bit on all of the port's square edges.

 

[dan5505 10+ year member]

Dan, 78 in^2 should definitely be plenty enough for 1 single 15". I would go with the deflectors in the corners, though, and use a roundover bit on all of the port's square edges.

ok, thanks. ill add the deflectors. Im assuming that i need to add the volume displaced by the deflectors to the end of the port right.

 

[tommyk90 5,000+ posts]

Personally, I still think that 78 sq. inches is too much.

For a daily driving enclosure thats tuned low (like yours), 50-60 is the max that I would do.

If you decided to use aeroports you could get away with even less.

 

[IonSQL 10+ year member]

^^ agreed

 

[dan5505 10+ year member]

k, i reduced the port width to 4" giving me a port area of 66 sqin. i could also go 3.5" wide and have port area of 57.75 sqin. is it really going to matter though?

 

[dan5505 10+ year member]

here it is with 57.75 sqin port volume. i think this one is the winner (i hope). This is working out good though cus its decreased the size of this thing alot.