Do front firing ports = self cancellation?

4-stringB · #1 12-28-2010, 04:03 PM

Looking at charts of sound propagation, I began to wonder, would side, top or rear firing ports on a given cabinet be more efficient? Or is it a lot of work for not much return?? Would side ports just blow out the drummer and singer, who already think I'm too loud? I need all you smart speaker guys to chime in, I'm just the DA bass player...Tnx

billfitzmaurice · #2 12-28-2010, 04:04 PM

Port location is moot. Their radiation is omni-directional.

RoboChrist · #3 12-28-2010, 04:06 PM

Quote:

Originally Posted by billfitzmaurice

Port location is moot. Their radiation is omni-directional.

Then why do rear firing cabs sound better?

(not being a smartass, just curious)

mcapote · #4 12-28-2010, 04:08 PM

Quote:

Originally Posted by RoboChrist

Then why do rear firing cabs sound better?

(not being a smartass, just curious)

probably because most people have the rear facing a corner such as is recommended for PA subs placement

JimmyM · #5 12-28-2010, 04:09 PM

they don't always sound better. you just happened to play a couple rear firing cabs that you thought sounded better than a couple front firing cabs. move the port to the front and you will hear no difference whatsoever.

JimmyM · #6 12-28-2010, 04:11 PM

Quote:

Originally Posted by mcapote

probably because most people have the rear facing a corner such as is recommended for PA subs placement

corners work the same way on cabs whether rear or front ported. you don't want to stuff a rear port into a corner and hinder its effectiveness, but move it out 6 inches and a front ported cab will behave exactly the same way in a corner.

s_mcsleazy · #7 12-28-2010, 04:13 PM

what about mixing ports aka frount ported and rear

even if the speeker size is the same

billfitzmaurice · #8 12-28-2010, 04:14 PM

Quote:

Originally Posted by RoboChrist

Then why do rear firing cabs sound better?

(not being a smartass, just curious)

They don't.

Johnny Crab · #9 12-28-2010, 04:15 PM

Billfitzmaurice speaks the truth as does JimmyM.

Andy, who works closely with his speaker manufacturer also says it doesn't matter. Don't want to copy the whole article and the direct link doesn't function as one, so go here: http://www.acmebass.com/

Click "PRODUCTS" on the left sidebar
Scroll to the bottom and click the link titled
"An explanation of the (un)importance of port placement"

Andy's cabinets work. The math, physics, and real-life use verify what he says.
Billfitzmaurice designs work(brother-in-law's students fill a stadium with 2 used for a marching bassist in marching band)

Note: If you position any ported cabinet with the ports obstructed(i.e. jammed into a wall on rear-ported cabinets), all bets are off on what you'll get.

mcapote · #10 12-28-2010, 04:15 PM

Quote:

Originally Posted by JimmyM

corners work the same way on cabs whether rear or front ported. you don't want to stuff a rear port into a corner and hinder its effectiveness, but move it out 6 inches and a front ported cab will behave exactly the same way in a corner.

but im saying his comment of why do rear facing sound better. its probably because most people have the front facing forward which has the rear ports coming off the corners. Im aware front facing can do the same but most people dont face their speakers towards the corners. my subs are front ported too, i just turn em around

Zooberwerx · #11 12-28-2010, 04:16 PM

Quote:

Originally Posted by RoboChrist

Then why do rear firing cabs sound better?

(not being a smartass, just curious)

I've been told it has something to do with the enclosure's orientation / placement....walls, reflective surfaces, etc. I can neither confirm nor deny this tidbit. Andy Lewis (Acme) pretty much says that port placement was based on whatever space was available.

Riis

JimmyM · #12 12-28-2010, 04:34 PM

Quote:

Originally Posted by mcapote

but im saying his comment of why do rear facing sound better. its probably because most people have the front facing forward which has the rear ports coming off the corners. Im aware front facing can do the same but most people dont face their speakers towards the corners. my subs are front ported too, i just turn em around

you can take the same exact cab except make one rear ported, one front ported, and put them each 6 inches away from the corner, and you won't be able to tell the difference. and if there's a difference by putting them closer than 6 inches, it's because the rear port will be too stopped up to be effective. this has been proven time and time again by pro sound experts and audio engineers with actual data to back it up. dude from acme says it and puts his ports wherever they fit the best...he knows his stuff.

RoboChrist · #13 12-28-2010, 05:50 PM

I like rear ports better.

Zooberwerx · #14 12-28-2010, 06:58 PM

Quote:

Originally Posted by RoboChrist

I like rear ports better.

Is that a llama in your avatar and, if so, why does she look so nervous? She is kinda purty.

Riis

RoboChrist · #15 12-28-2010, 08:02 PM

Quote:

Originally Posted by Zooberwerx

Is that a llama in your avatar and, if so, why does she look so nervous? She is kinda purty.

Riis

You calling her "purty" sure doesn't help her any.

KJung · #16 12-29-2010, 03:49 AM

Quote:

Originally Posted by RoboChrist

Then why do rear firing cabs sound better?

(not being a smartass, just curious)

I think you are making the mistake of attributing the sound differences among cabs to port location. It would not surprise me if you happen to like the tone of some cabs that have rear ports better than some cabs that have front ports. However, you are misattributing the tonal differences of those cabs to port location.

A good example of this is the Bergantino AE line of cabs. Due to, I assume, nothing more than the size of the box requirements, Jim uses a front shelf port for his AE410, and rear tube ports for his AE210. If you A/B the 410 with 2 x 210, the tone and performance are VERY similar.

Another example is the Low Down Sound custom cab approach, where Don will appropriately tune a cab using ports that will best fit the box size and configuration. I've played a number of similarly tuned and spec'd versions of LDS cabs that differ only in format (i.e., tall and thin versus short wide) and port location, and they sound literally identical.

**Rune Bivrin** · #17 12-29-2010, 04:18 AM

There is of course the possibility that highs (relatively speaking) come out of a rear port if it's improperly located, and then they bounce of a rear wall and land in your ears. Thus changing the sound slightly.

KJung · #18 12-29-2010, 04:55 AM

Quote:

Originally Posted by Rune Bivrin

There is of course the possibility that highs (relatively speaking) come out of a rear port if it's improperly located, and then they bounce of a rear wall and land in your ears. Thus changing the sound slightly.

+1 The assumption of 'doesn't matter' is based on a properly placed and designed port, versus, for example, that big hole cut right behind the driver in the Bag End 115.

wmheilma · #19 12-29-2010, 08:25 AM

This is a great question and one I have wondered about a lot! Recently I had Don (at LDS) build be a custom cab which is rear-ported. It sounds great for club dates, and it's very compact which is a plus. I always like my old SWR Goliath II which was rear ported also. On the other hand, I use an SWR Henry the 8x8 for outdoor shows where the back wall is far away.

billfitzmaurice · #20 12-29-2010, 12:09 PM

Quote:

Originally Posted by wmheilma

This is a great question and one I have wondered about a lot! Recently I had Don (at LDS) build be a custom cab which is rear-ported. It sounds great for club dates, and it's very compact which is a plus. I always like my old SWR Goliath II which was rear ported also. On the other hand, I use an SWR Henry the 8x8 for outdoor shows where the back wall is far away.

The distance to the rear wall is moot. Low frequencies radiate omni-directionally.