Rear Port / Front Port

[Dave44]

As per my sound man he would prefer me to use the front ported speaker cab I plan to buy. Fears of low end leaking into open mics from being reflected off of back walls etc. Question is, does it make a diffrence?

[stflbn]

I think he has way more frequencies to worry about reflecting into mic's than bass frequencies.

[T-Bird]

Hi.

Originally Posted by Dave44

Question is, does it make a diffrence?

On bass frequencies, no, it doesn't make a difference.

On mids, front ports are easier to locate so the mids won't leak through the port(s).

OTOH too small ports on front may produce unwanted sounds as well, and if the cab is miked it'll sound strange.

Buy quality, and it won't matter either way.

Regards
Sam

[JohnMCA72]

Ask him if he knows what "HPF" means.

[Marko5657]

I’m wondering why a rear-ported cab would hit the mics less than a front-ported.


Pretty sure those frequencies are omnidirectional anyways.

[Phendyr_Loon]

Sound guys are funny.

I think this guy is forgetting the radiating (I think that's the right word) properties of low frequencies.

Front mount or rear mount, if low frequencies were to posed a problem in this instance port placement would make no difference.

[DukeLeJeune]

The only difference I can think of is based on this: SPL falls off by 6 dB with each doubling of distance (I'm making a couple of simplifying assumptions). So if a front-ported speaker puts the ports significantly farther away from the mics, it might make a difference. Otherwise, I don't think it matters.

[testing1two]

It's more of a theoretical argument than a practical one. Yes, any sound directed backwards is going to reflect off of the back wall and return several milliseconds later to combine with the direct sound. But it's also going to reflect off the side walls and the ceiling and the floor and the results vary with frequency, temperature, humidity, as well as diffusion, reflection and absorption factors in the room. In other words the "sonic ecosystem" is much more complex.

But in practice, choosing your gear based on the direction of the ports borders on absurd. Try telling guitar players they can't use open back cabinets or organ players that they can't use Leslie cabinets. And don't forget to tell the vocalists they can't use wedges either. And make sure your drummer brings his front-firing kit (back-firing kits are only good for metal).

I do understand and share the desire to minimize low frequency leakage in cabinet mics, especially drum and bass cabinet mics where typical HPF's are impractical (virtually all mixing consoles under $5k do not have a sweepable HPF. They are fixed somewhere between 70Hz and 100Hz which doesn't flatter kick drums, floor toms and bass cabs). But that low frequency energy is omnidirectional so the challenge exists no matter where your cabinet ports are.

All that to say this: choose the cabinet your ears like best. Your engineer will make it work or he shouldn't be your engineer.

[Never_grew_up]

Originally Posted by testing1two

(back-firing kits are only good for metal).

I had a '64 Oldmobile that backfired an it was ALL metal.

But I would rather have a front ported cab. I know it doesn't make any difference in regards to the cabinet's tuning frequency, but when I play a rear ported cab and feel all that air coming out the back, I can't help but feel that if it were coming out the front it would be more acoustic energy going in the direction I want it to.
When I'm hot I point a fan AT me to cool off rather than pointing it up, down, sideways or away from me so I can feel the secondary effect of it bouncing off walls or moving an entire room full of air. Once it blows on me I know it's going to go all over the room, I just want to get all I can for me first.

[Bassamatic]

I have had this debate with 2 acoustic engineers that we work with and the answer is definitely that IT DOESN't MATTER, contrary to what our common sense is telling us.

The low frequencies immediately spread out 360 degrees around the cab like sticking your hand into a pond. By the time such frequencies could become directional, they are cut off by the cab design.

[MNAirHead]

What they could be warning about is putting a rear port flush against a wall

[JustDavid]

I think you should use whichever type of cab he buys for you.