Sub and Port Firing Direction

[B1GR3DDD]

I've been going over several different sub box renditions for the 2 HDS312's I will be ordering soon on a SQ 2200.2 amp. My biggest problem that keeps occurring is port area and length. I have always thought that it is best to have both the subs and port firing toward the rear is the best route. However, the designs I am coming up with that have proper port area have too long of ports, or the ones with proper lengths, have too little port area. The best solution I seem to have for this is to do a side firing 8 inch aeroport with subs facing toward the trunk.

What are your guy's thoughts on the orientation of the subs and the port?

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[Umbra]

Port and sub orientation is vehicle dependent. Ideally you'll want to experiment to find the ideal configuration, but since ain't nobody got time for that go for both subs and port firing towards the trunk lid (assuming you're doing this for a trunk setup, as per your sig). If you don't mind sacrificing trunk space have it close to the lid, like a few inches (play with the positioning). Also deaden the hell out of the lid, wrap some tape around the latch to keep its snug, and stick some foam under your license plate because it's going to rattle like a mofo.

Alternatively have everything forward firing into the cab and wall it off.

If you don't have adequate port area you'll have port noise, so don't skimp on it. What constitutes adequate varies from builder to builder. A rough guideline is 9-11 square inches for aero ports and 12-16 for slot ports.

If you're a slot port just have the port bend to fit the extra length in there. If you're doing PVC aeros you can buy right angle PVC couplers to get enough length. Either way, make sure you're subtracting the volume of the ports from your gross volume (unless they're outside the box) or it'll skew your tuning.

 

[Boomin_tahoe 5,000+ posts]

@CSCStang this guy can help ya out with a design.

 

[CSCStang]

Holler

 

[Papermaker85 5,000+ posts]

its important to understand phasing and loading when building a designing a box.. most times firing up and back works good but ive had good results with sub forward and ports back as well..

 

[Jeffdachef 5,000+ posts]

its important to understand phasing and loading when building a designing a box.. most times firing up and back works good but ive had good results with sub forward and ports back as well..

I've seen that configuration in a few loud CRXs Just not sure how that actually works phase wise.

 

[Papermaker85 5,000+ posts]

its like this.. from the hip to the hop to the hippiti hop hop.. and bam perfect phase at the dash..

 

[SimulatedZero 10+ year member]

How wide is the frequency bandwidth that plays from a port?

If it plays higher notes, then phasing and placement would be very important. If it only resonates with the lower frequencies, then it's not as detrimental to have some distance in between.

Another thought, what about having the port come back and fire onto the subwoofer? I've seen a couple of builds like that, but it's not real common. My thought would be it would help with phasing by making the driver and port appear as one acoustical driver instead of two separate points.

 

[Umbra]

I've seen that configuration in a few loud CRXs Just not sure how that actually works phase wise.

Pure speculation here, but I'm guessing whatever is firing against the back of the car is reflecting back towards the cabin in such a way as to not cause phase issues with the other source (port/sub). If the notes are low the wavelengths are long enough to stay in phase.

Another thought, what about having the port come back and fire onto the subwoofer? I've seen a couple of builds like that, but it's not real common. My thought would be it would help with phasing by making the driver and port appear as one acoustical driver instead of two separate points.

I'd be interested in seeing that.

 

[SimulatedZero 10+ year member]

I'd be interested in seeing that.

Yeah, of I had enough spare MDF around I'd make teo SQ boxes for one of my subs. One with the port firing on to the cone and one with the port firing the same direction as the cone and put them on the far side of the box. Just to see what happened.

I doubt you'd see too much of a difference in a single driver set up, but multi aib setups might see benefit

 

[Papermaker85 5,000+ posts]

depends on the box driver and port. the larger ports peak harder around tuning. the larger the box/port the harder it peaks at tuning. some drivers handling this better than others.

there is a point of diminishing returns.. you can load hte box and port too much where you dont have enough compliance to control the woofer.. you can overload the port(box to big port to small) where you don't have enough port area and the port acts like a resistor and vice verse with the box you cna have the port to big and box to small. you have to find that balance.

if you say for instance want a shitload of output you can go really small of the box and work your way up with the port area this alllows the port to peak hard and the subs tiny box still has enough compliance to control the woofer. and vice verser you can get a shitload of cone area and get a port just big enough to not act like a huge resistor..

personally for a daily setup i use just enough port area to not make any noise and then use the apporate box size for the response im looking for.. with the SPL drvers though. wit hthe really stiff suspension you cna sometimes use alot of port area and use a faily small "net" box size and get good results because the suspension can handle the demand.

as far as phasing regardless the port and woofer interact throughout the bandwidth. so phase is important. the backwave should always be 2x longer than the from wave to a given location. and that is determined by the frequency your playing and the position your trying to get the coupling..

 

[B1GR3DDD]

This is going to be a daily driver setup, so I'm really not trying to squeeze every drop of DB's I can out of them. I want a box that will slam pretty hard and sound alright too.

 

[Boomin_tahoe 5,000+ posts]

This is going to be a daily driver setup, so I'm really not trying to squeeze every drop of DB's I can out of them. I want a box that will slam pretty hard and sound alright too.

So basically just a daily ground pounder

 

[Boomin_tahoe 5,000+ posts]

The biggest problem in trunks....is the bass gets "trapped" in there. Nowhere to go.

What about the ski hole, or port thru the rear deck?

Had a Cavalier one time and a single 15 I couldn't figure out why I was getting no bass. Finally took a trip to the car audio place and the guy there was nice enough to show me the rear deck there's some speakers there remove those and the sub was able to "breathe" thru those holes.

 

[B1GR3DDD]

So basically just a daily ground pounder

If you want to call it that lmao

 

---------- Post added at 08:52 PM ---------- Previous post was at 08:51 PM ----------

 

The biggest problem in trunks....is the bass gets "trapped" in there. Nowhere to go.
What about the ski hole, or port thru the rear deck?

Had a Cavalier one time and a single 15 I couldn't figure out why I was getting no bass. Finally took a trip to the car audio place and the guy there was nice enough to show me the rear deck there's some speakers there remove those and the sub was able to "breathe" thru those holes.

I wouldn't be opposed to doing something like that, I just don't want to tear up the interior of my car