Rear Ported Cabinets - Good? Bad?

[bobalu]

Well, you could aways go to Guitar Center and ask to play the cab in the parking lot...

L.O.L. ! Can you imagine the sales dudes face if you actually asked that!

 

[Rick Auricchio]

I had an old Peavey 410TX cab...Best placement for that one was in the corner, about 2 feet away from each wall. I don't have the knowledge to even attempt that explanation, all I can tell you is how it sounded... which was suprisingly good for how cheap I picked that cab up.

It's fairly simple to explain:

Cab in free space, away from all surfaces: "normal" volume.

Cab on the floor, middle of the room: +3dB.

On floor, against a wall: +6dB

In a corner, you get floor + 2 walls: +9dB

 

[billfitzmaurice]

Best placement for that one was in the corner, about 2 feet away from each wall...I don't have the knowledge to even attempt that explanation.

It's called Boundary Reinforcement, which boosts bass sensitivity by 6dB in the low end when you have the cab close enough to one wall, and by 12dB in a corner. The distance required to get these free dBs is approximately 2.8 feet or less from the front of the cab to the boundary/boundaries. With placement further away you get room cancellation modes that actually suck out the bass. Boundary reinforcement and cancellation modes affect every type of speaker equally, be it sealed or ported or horn, and in the case of ported front or rear makes no difference.

 

[billfitzmaurice]

It's fairly simple to explain:

Cab in free space, away from all surfaces: "normal" volume.

Cab on the floor, middle of the room: +3dB.

On floor, against a wall: +6dB

In a corner, you get floor + 2 walls: +9dB

Not quite. 'Free space' is suspended in the air, at least 1 wavelength up, which at 100 Hz is eleven feet, and at 50 Hz 22 feet, so for all intents and purposes bass cabs are never in free space. As noted above quarter space (wall loading) and eighth space (corner loading) get you 6 and 12 dB respectively. But that's only in the low end. Where the cabinet baffle size is one wavelength or more (above 500Hz on average) radiation is directional, so you get nothing additional from a rear wall, but you do get 6dB in a corner.

 

[X Wolf]

I'm not an engineer but after playing many cabs over many years I have always preferred the sound of front ported cabs, especially in my small studio. for large venues I've gotten the best results from folded horn types as well as traditional front ported cabs, mostly with fifteens. Technically I don't know why, I just trust my ears and the feedback I get from the people out front who I trust to tell me how it all sounds. With regard to "Front Port" vs. "Rear Port" I don't think it's a question of "Good" or "Bad" just use what sounds best to you. Just my 2 cents.

George

 

[Curtybob]

It's called Boundary Reinforcement, which boosts bass sensitivity by 6dB in the low end when you have the cab close enough to one wall, and by 12dB in a corner. The distance required to get these free dBs is approximately 2.8 feet or less from the front of the cab to the boundary/boundaries. With placement further away you get room cancellation modes that actually suck out the bass. Boundary reinforcement and cancellation modes affect every type of speaker equally, be it sealed or ported or horn, and in the case of ported front or rear makes no difference.

That last sentence.... in redneck terms, are you saying that I can get the same bottom "boost" with a front ported cab (or any cab, I think) in the corner? Because that's something I had not tried. And if that's the case, then the 410TX I had just lost a little magic in my feeble little brain. And my TVX just gained a little experiment time...

 

[fdeck]

I'm not an engineer but after playing many cabs over many years I have always preferred the sound of front ported cabs, especially in my small studio. for large venues I've gotten the best results from folded horn types as well as traditional front ported cabs, mostly with fifteens. Technically I don't know why, I just trust my ears and the feedback I get from the people out front who I trust to tell me how it all sounds. With regard to "Front Port" vs. "Rear Port" I don't think it's a question of "Good" or "Bad" just use what works for you. Just my 2 cents.

George

One possible reason is that the rear port is a solution to the problem of finding a place for the port on the front of a very small box, so the front ported ones tend to be in bigger boxes and hence have more low end.

All other things being equal, YMMV, etc.

 

[billfitzmaurice]

One possible reason is that the rear port is a solution to the problem of finding a place for the port on the front of a very small box, so the front ported ones tend to be in bigger boxes and hence have more low end.
.

That's precisely the case with Markbass. Their front ported cabs go lower, because they're larger. The rear ported cabs are rear ported because the cabs are too small to fit them on the front. The size of the cabs make them sound different, the port location does not.

in redneck terms, are you saying that I can get the same bottom "boost" with a front ported cab (or any cab, I think) in the corner?

Yes.

 

[SubXero]

I've never really thought there was THAT much of a difference between them...

I'm not sure how any of the people with the front ported cabs are managing to place your bass cabs directly against the wall, wouldn't you be bending/crushing the cables coming out the back? Unless you start putting the connectors in some weird place as well. I think realistically most cabs aren't really being placed literally right up against a wall anyway so this is likely not that big of a deal...I've used all kinda speakers that can't be placed up against a wall (like bi-directional magneplanar speakers) and generally the most space you ever need with those is only a foot or two. I can't imagine you'd need more than a foot for a rear ported cab, but maybe I'm crazy...it just doesn't seem that anything more than a foot is going to make a difference in terms of how much air can move in and out of the hole...

for reference I currently have a front ported cab but was considering a rear-ported bag end for a long time, but eh, then I saw a bergantino in the classifieds and the price was right...lets just say the front/rear ported thing was not a concern to me in either case.

 

[Stumbo]

I'm not sure how any of the people with the front ported cabs are managing to place your bass cabs directly against the wall,

Read above^^^. Not directly against a wall.

 

[Turn Em Loose]

I've used rear ported cab on and off for the last 17 years.... indoor and out and I've NEVER had an issue with fulling a room and or field.

I've got Bag Ends 1x15's with the big ol' rear port. And they sound the same inside or out, IMO. In fact, the indoor and outdoor tone from my BE's, to me, is more consistant than with my front ported speakers. (But then we're talking different brands. So apples and oranges.)

Just use youre ears. And go used!

 

[nordic27]

Port placement makes no difference unless you place your cab against something that would obstruct the port ( such as a port in the back). Inside the cab the air is a pressure wave and once it exits the cab it becomes ommidirectional. My port is on the side and sounds every bit as good as a front or rear port enclosure.

 

[Supertanker]

I've got Bag Ends 1x15's with the big ol' rear port. And they sound the same inside or out, IMO...

That's been my experience with my 8 or 10 cabinets I've used over the years and with my current rear ported Aggie S210 & S410.

They sound great indoors or out.

Actually all my gigs since May have been outdoors (1 or 2 per week), with no PA support.

And I've been kicking a$$ with em...

 

[Brad Johnson]

I've used rear ported cab on and off for the last 17 years.... indoor and out and I've NEVER had an issue with fulling a room and or field.

Me neither.