PORT QUESTIONS Truck center console w/ dual opposed 12” NVX 20-25hz

[066]

Hi my name is Dylan. Thanks for looking at my thread. Like the title says, I’m working on a center console. I have some probably basic questions but I haven’t been able to find what I’m looking for on Google. I am using WinISD btw.

Vehicle : 06 F250 Crew Cab

Location in the vehicle: center console w/ subs firing into rear passenger footwells

Space available (Length x Width x Height): ~15x15x47 outer

Subwoofer make and model:NVX VCW122

Subwoofer Size:12”

Number of Subwoofers:2

Type of Port (Kerfed, Slot, Aero, etc.): diy aero

What type of music do you like?: everything except country

Is your goal SPL or Everyday Music?: 90% everyday listening

Tuning Freq (Hz): 20-25 hz

Volume : mid to high

Questions

1) What would be the preferred port location in a situation like this? Would it be bad to face it towards the dash?

2) My plan is to integrate either 4” or 6” PVC into the 3/4” MDF box and roundover the ends. Is 1/2” roundover enough?

3) Tuning to 25 hz, port velo is peaking at 31ms. Is this acceptable with the flare? I hear 36ms is the number, just double checking what the consensus here is.
It peaks at 25ms when tuned to 20hz.

4) I also hear that when tuning in WinISD, you generally end up with lower tuning than what you expected. Is this still true?

I’m sure I have more questions but I’ll leave it there for now. I appreciate any help.

Click to read more...

 

[winkychevelle 10+ year member]

Don't tune that low and you need 7-12sq inches of port per cube for aero ports.

The lower the air speed is the lower the chance of port noise. Sub 40m/s is what I shoot for.

I honestly would not fire subs opposite directions. I would rather do 2 10s down firing front port than what you are doing. Opposing subs have the possibility of cancelation the further they are away from each other. And in your case you have to measure center of box to window back to sub which is a rather long path.

From what I've seen when I modeled the nvx vcw104v3 the factory recommended box specs work well.

 

[066]

I appreciate the input. So my box as planned is 4.2 cubes. Cross area is what you’re referring to right? 6” is 28.27 so on the very low side of what you said.

I’ll model the 10s for kicks. I can still return the 12s.

For now, I already have the 12s and I like how they sound but the sealed box they’re in won’t let them dig. It plays a 30hz test tone well but there are a few songs I listen to that they won’t hit at all.

Keeping in mind these subs have an fs of 24. I’m happy with output even in sealed right now but not below 30hz. Why is that the wrong tuning? The graph looks good to me? My goal is to get lowest, not loudest

I’m open to face them upwards. Port direction shouldn’t matter as long as air velocity is right i guess?

I understand the dual opposed should cancel box vibrations, but you’re thinking I’ll have sound cancellation?

Is this a road you went down before lol? Everything I can find has been about home audio. Anything you can point me to focused on car audio?

Thanks again.

 

[066]

Sorry I didn’t make that clear at first but that is my main goal, to get really low.

 

[winkychevelle 10+ year member]

Sorry I didn’t make that clear at first but that is my main goal, to get really low.

I would not tune below 28hz even to get stupid low. Remember the lower you tune the more you give up higher. And door speakers can sometimes play to 60hz but it's more likely the 80hz will be their limit. Tuning so low will likely make you drop off around 50hz and you are likely to be around the same volume or lower considering the loss at higher frequency. But I think it will work out ok.

And yea sound cancellation is always possible it's the primary reason door speakers struggle at 60hz the distance between the speakers in most cars lines up nearly perfectly to be 180° out of phase around 60hz.

This distance increases the lower the freequency so you may find cancellation in the sub range considering the nearly doubled distance between the sub cones. This is frequency dependant so it won't be total cancellation.

7in² per cube is the minimum I would go I ran both a single 6inch and dual 4 inch in a 3ft³ box with good results but that's the minimum I would go without fear of port noise.

Port location shouldnt matter much, but it at least in my thought process, I haven't tested it out personally, shouldn't be 180° opposite the speaker cone for the same issues of cancellation.

I do know that some competition style boxs are sub and port opposite but they are playing a very narrow frequency range where cancellation is less of an issue.

Personally I'd face the subs up or down and port to the front or rear.

 

[winkychevelle 10+ year member]

This is my design for 2 10s isobaric in a parallel 6th order. I think your box is actually smaller than my planned box. But I'm planning to be flat as possible 30-65hz

 

[winkychevelle 10+ year member]

Ad I don't think you need to return the subs I just don't like the particular way your subs were facing in the design.

Up will be louder but in my experience down will be lower. But if you are tuning so low I don't think playing low will be the issue.

Porting forward will shove the low notes up front which would make it easier to blend if you decided to go the sq route

 

[066]

Thanks for the thought out response.

That’s awesome, what subs are you using? What’s it going in?

Well I really wanted to regain the top deck for “activities” lol but I’ll shelf the dual opposed idea for now. How much room between sub and floor would I need to downfire? How would you mount the box in this location, being over the transmission hump?

Ive started playing with tuning near 30hz. Cool part is shorter tubes hehe.

I’m thinking this probably isn’t enough room to fire 3 4” ports lol. The framing square is where the new box will end, leaving about 7inches there.
If I fire ports backwards, the seats will block it which isn’t a huge deal because it’s usually just me in the truck anyway. = fold the seats up.

 

[winkychevelle 10+ year member]

Thanks for the thought out response.

That’s awesome, what subs are you using? What’s it going in?

Well I really wanted to regain the top deck for “activities” lol but I’ll shelf the dual opposed idea for now. How much room between sub and floor would I need to downfire? How would you mount the box in this location, being over the transmission hump?

Ive started playing with tuning near 30hz. Cool part is shorter tubes hehe.

I’m thinking this probably isn’t enough room to fire 3 4” ports lol. The framing square is where the new box will end, leaving about 7inches there.
If I fire ports backwards, the seats will block it which isn’t a huge deal because it’s usually just me in the truck anyway. = fold the seats up.

A 6inch aero is likely enough.

My design is for a 13 Silverado 3500hd and will fit similarly to your box but shorter because I'm gonna add 2-3inch of foam padding on top.

Box is designed for 2 nvx vcw104v3. low end is tuned to 28hz, high end 55hz and gross outside dimensions are 4.3ft³ so a big box for what's only gonna sound like 1 10 in a 6th order.

I need to bust out the pen and paper and see if I can just use 1 10 instead of 2 isobaric. That makes my chamber size double but I currently have 2ft³ of just port displacement and the coupling chamber. 1 10 would need 3.5ft³ plus port displacement which would need to be less than .3ft³ to be smaller and that's doubtful. Might be worth making the box a touch longer to save money and power requirement though.

As far as how to mount over the transmission hump feet going down further than the box and some strapping material to bolt to the factory seat mounts.

How much higher to down fire? Probably 2.5inch
They make grills for these subs so as long as the grills fit they should be fine

 

[066]

I hear you on power. How big of an alt does that Duramax have? Mines only 130, will likely be the next thing I upgrade. Stock dual batteries ftw.
I was surprised how much space the slot port takes. This is my first ported build, so I didn’t know what to expect.

I’m gonna play with the idea of downfiring. The low fs combined with the fact these speakers have grilles is why I went for this sub. I do have the grilles.

I know you don’t like this placement but can we expand a little on dual opposed? It happens to be the best way I can think to utilize the space and I’m in favor of canceling box vibration. You say measure from center of box (or speaker cone?) to window (door panel okay?) and back to center of box to find the distance between speakers correct?

If I use the door panels and speaker cone as reference, I get about 10’ which seems would cancel
~90 hz

If I use the center of box to top of window, I get about 13’ which seems would cancel ~75hz

I assume the answer is somewhere in the middle?

My Door speakers are 4x Kicker ds 6x9 and 4x Kicker ds 6x8 running on a JL M600/6

I’m thinking I might be able to fill that gap?

 

[winkychevelle 10+ year member]

I hear you on power. How big of an alt does that Duramax have? Mines only 130, will likely be the next thing I upgrade. Stock dual batteries ftw.
I was surprised how much space the slot port takes. This is my first ported build, so I didn’t know what to expect.

I’m gonna play with the idea of downfiring. The low fs combined with the fact these speakers have grilles is why I went for this sub. I do have the grilles.

I know you don’t like this placement but can we expand a little on dual opposed? It happens to be the best way I can think to utilize the space and I’m in favor of canceling box vibration. You say measure from center of box (or speaker cone?) to window (door panel okay?) and back to center of box to find the distance between speakers correct?

If I use the door panels and speaker cone as reference, I get about 10’ which seems would cancel
~90 hz

If I use the center of box to top of window, I get about 13’ which seems would cancel ~75hz

I assume the answer is somewhere in the middle?

My Door speakers are 4x Kicker ds 6x9 and 4x Kicker ds 6x8 running on a JL M600/6

I’m thinking I might be able to fill that gap?

I'm not sure on the math one it but I know that when 3 speakers face each other at various distances you can get cancellation.

You may be very close to correct using your numbers. You also have cabin gain that will affect frequency response but no way of knowing what cabin gain is without doing measurements with a calibrated mic.

You also have to remember that opposing them with the magnets facing one another means you need double mounting depth plus some space between. I don't recall mounting depth on these but I would assume they are around 6.5inch which should fit.

It's may very well work fine I just shy away from that technic and try and mount subs in different ways.

 

[066]

Well I’ve thought on it more and I figured out how to downfire. Now I’m back to port questions lol

I’m gonna fire the ports to the rear. If I space them out an inch from the walls and each other, I can put a big flare on each port but the lower 2 will be slightly obstructed with the rear seats down.

If I put them all in a line, I can’t put as big of a flare but they can all clear the back seats. I assume this becomes a weak spot though. They would have about 1/4” between each pipe and each end of the board. This is a back panel and will be covered on every side. What if I double up that panel on the inside?
Or triple/quadruple just that area?

 

[winkychevelle 10+ year member]

Well I’ve thought on it more and I figured out how to downfire. Now I’m back to port questions lol

I’m gonna fire the ports to the rear. If I space them out an inch from the walls and each other, I can put a big flare on each port but the lower 2 will be slightly obstructed with the rear seats down.

If I put them all in a line, I can’t put as big of a flare but they can all clear the back seats. I assume this becomes a weak spot though. They would have about 1/4” between each pipe and each end of the board. This is a back panel and will be covered on every side. What if I double up that panel on the inside?
Or triple/quadruple just that area?

I'd do the triangle configuration and likely wouldn't bother with the flares.

 

[Ridinhi 5,000+ posts]

Well I’ve thought on it more and I figured out how to downfire. Now I’m back to port questions lol

I’m gonna fire the ports to the rear. If I space them out an inch from the walls and each other, I can put a big flare on each port but the lower 2 will be slightly obstructed with the rear seats down.

If I put them all in a line, I can’t put as big of a flare but they can all clear the back seats. I assume this becomes a weak spot though. They would have about 1/4” between each pipe and each end of the board. This is a back panel and will be covered on every side. What if I double up that panel on the inside?
Or triple/quadruple just that area?

Can you share a pic of the entire enclosure ?

 

[066]

I made the total height a little taller so I can space these ports a little more and they should clear the back seat. I’m gonna flare them at least for the looks lol. This is with a 1/2” roundover.
If the ports end up being an inch away from the sidewalls, is that gonna change the tuning? Or should I try to get them further away? They’ll be plenty far away from the front wall

This is the best picture I could do lol. I know the subs are lopsided hehe