front port vs. rear port

simsalabim · « **on:** 8 Jul 2003, 01:20 pm »

Newbie question: In a very experimental DIY (25 litre/.88 cu. ft. ceramic garden pots) I'm wondering whether to port front or rear. What's the wisdom/pro-cons of both?

Thanks.

randytsuch · « **Reply #1 on:** 8 Jul 2003, 06:36 pm »

The arguments I have seen against rear porting is that you must keep the speakers away from the rear wall, or it will sound boomy with rear ports. This would not bother me, I like to keep my speakers away from the wall anyway, soundstage is better if the speakers are not too close to the walls.

The only argument I can think of against front porting is size, you can make a rear ported speaker smaller than a front ported speaker.

Randy

markC · « **Reply #2 on:** 8 Jul 2003, 08:44 pm »

I have also heard that a front ported design will allow a certain amount of midrange through the port, (on a two-way design), which you do not want.

simsalabim · « **Reply #3 on:** 9 Jul 2003, 08:43 am »

Thanks gents,
Care to elaborate on the reasons why front porting would increase cabinet size?

Also, when looking at port tube length/diameter recommendations for various drivers, do they assume rear porting or does that size remain constant?

Cheers, Ken

JohnR · « **Reply #4 on:** 9 Jul 2003, 12:10 pm »

Just that you have to have space on the front panel for the port. If you put it on the rear then you can make the baffle smaller, if that's what you want to do.

Ports also resonate. The latest version of Unibox will show this to you, it's a bit scary actually

markC · « **Reply #5 on:** 9 Jul 2003, 01:25 pm »

Recommended port length/dia. would remain constant whether front or rear mounted.

WerTicus · « **Reply #6 on:** 6 Aug 2003, 04:36 am »

your more likely to hear air movement noise through front ports
at high volumes.

_scotty_ · « **Reply #7 on:** 22 Sep 2003, 06:53 pm »

Quote from: simsalabim

Newbie question: In a very experimental DIY (25 litre/.88 cu. ft. ceramic garden pots) I'm wondering whether to port front or rear. What's the wisdom/pro-cons of both?

Thanks.

Mount it on the front the bass impulses from drums or explosions are directional and should be kept in phase with the rest of the frequency range.
Also it is easier to achieve a flater frequency reponse at the listening
position with a front firing port.

JoshK · « **Reply #8 on:** 22 Sep 2003, 07:31 pm »

scotty, I have one question though, since air coming from the front port is air being moved by the back of the cone it is necessarily out of phase, so from the rear seems to keep more phase consistency that from the front, or am I missing something?

P.S. I will refrain from my childish sexual comments about this thread title.

jackman · « **Reply #9 on:** 22 Sep 2003, 08:16 pm »

Dave Ellis gives a good explanation as to why he uses rear ports in his speakers. Dave's earlier speakers used front ports, however, he soon learned from trial and error.

Link:

http://ellisaudio.com/porthole.htm

Like many things in audio (and life!), there are positives and negatives to both designs. Dave's reasoning for using rear ports seems pretty solid.

Jack

_scotty_ · « **Reply #10 on:** 23 Sep 2003, 05:20 am »

Quote from: JoshK

scotty, I have one question though, since air coming from the front port is air being moved by the back of the cone it is necessarily out of phase, so from the rear seems to keep more phase consistency that from the front, or am I missing something?

P.S. I will refrain from my childish sexual comments about this thread title.

JoshK,you can always cut and mount a port on the front and rear and pick the one that sounds the best to you and put a foam plug in the unused one.The ports output is in phase with the woofers output until system resonance then it gradually goes out of phase with the woofer radiation.
Dave ellis was unsuccessful in eliminating objectionable midrange output
from his front port. Pipe resonances also interfered with the quality of his bass reproduction. You maybe luckier than he was with your design.Deflex panels inside the enclosure and a couple of bookshelf type acoustical labyrinth braces maybe all that is needed to eliminate both problems.Don't let the woofer see port directly, make the midrange go around a couple of corners first, the bass frequencies won't care about the the internal baffles and the midrange won't see a straight path out the port. The port may reproduce all of the bass impact at some frequencies, by aiming this energy away from you detract from the realism
that these instruments should have.Kickdrums are not aimed away from the intended audience or the recording microphone.