8" sonotube too big for a 4.5 box with a single 15

[ManzKea 152]

Hey guys I built a box for my zv5 15 and used an 8" sonotube because of the port area and how aero port don't take up as much air space as a slot. A buddy of mines saw my set up and questioned if that port was too big for my box.

 

i came to the conclusion of using and 8" port by doing some math and finding the port area. Which is 50" a little less than the recommended port area on the sundown website. But I'm assuming that's a slot port and I've read areonports require less port area than a slot so I guessed I was in the green. But after my friend brought it up I researched and found a site that said 6" is good for a 3.5 to 4.5 box. So I'm here asking for your guys input.  Thanks 

[Notorious97200 339]

How do you like the sound, the output ?

6" is on the small side, and 8" seems good for yoour setup. 
When you wtite 3.5 to 4.5 box, you must be talking of net volume, because an 8" port will take a lot of space in that volume. And a ZV.5 is a huge sub.

I'm waiting on what others will tell you.  (I'm not an expert at all!).

 

 

[Triticum Agricolam 15]

How much port area  you need depends on the size of the box, the tuning frequency, and the amount of input power.  What is your tuning frequency and how much power are you running?

There really isn't such a thing as "too much port area", what can happen is a port can get so long that you begin to have pipe resonance issues, but that usually doesn't become a consideration until the port gets up past 40" long.  

Be wary of anyone who gives port area recommendations based purely on box size, that's like saying "if you are 6' tall you wear a size 10 shoe".  It may not always be wrong, but it isn't always going to be right.  The BEST way to determine how much port area you need is using simulation software (WinISD, etc) and seeing what port velocities you get.  If you can't do that, here is a port area calculator that takes into account box size, tuning, and input power:

[ManzKea 152]

1 hour ago, Notorious97200 said:

How do you like the sound, the output ?

6" is on the small side, and 8" seems good for yoour setup. 
When you wtite 3.5 to 4.5 box, you must be talking of net volume, because an 8" port will take a lot of space in that volume. And a ZV.5 is a huge sub.

I'm waiting on what others will tell you.  (I'm not an expert at all!).

 

 

I like the sound of it. Hits all the notes but has a roll off on higher bass notes which I've read is normal for the zv4 and x series . Yes I'm referring to net volume .

 

i was looking at flared ports and I saw a persons review and that's what got me questioning if the port is too large. 

 

https://www.parts-express.com/precision-port-6-flared-port-tube-kit--268-354

 

its down by the questions and answers part. He says 8" would be good for an 18.

[ManzKea 152]

32 minutes ago, Triticum Agricolam said:

How much port area  you need depends on the size of the box, the tuning frequency, and the amount of input power.  What is your tuning frequency and how much power are you running?

There really isn't such a thing as "too much port area", what can happen is a port can get so long that you begin to have pipe resonance issues, but that usually doesn't become a consideration until the port gets up past 40" long.  

Be wary of anyone who gives port area recommendations based purely on box size, that's like saying "if you are 6' tall you wear a size 10 shoe".  It may not always be wrong, but it isn't always going to be right.  The BEST way to determine how much port area you need is using simulation software (WinISD, etc) and seeing what port velocities you get.  If you can't do that, here is a port area calculator that takes into account box size, tuning, and input power:

That's a lot of port area to hit the recommended amount for a 6ft3 box ran off of 4K. 

 

For me me I was tuned to 32hz it sounded great hit the lows like never before. But the upper notes sucked so I cut off a few inches and I'm at 34hx now. Using a taramps 5k to push it. I clicked the pic is there a link for it or do I need an app to open it properly? Im using my iPhone right now. And that's a perfect example you given with the height and shoe size. 

 

Ive also read that subs with too big of a port area will result in the sub bottoming out easier. So im curious as to if the 6" will make a noticinle difference in sound and loudness and all that. But sounds like my port isn't too big for the sub 

[Triticum Agricolam 15]

4 minutes ago, ManzKea said:

That's a lot of port area to hit the recommended amount for a 6ft3 box ran off of 4K. 

 

For me me I was tuned to 32hz it sounded great hit the lows like never before. But the upper notes sucked so I cut off a few inches and I'm at 34hx now. Using a taramps 5k to push it. I clicked the pic is there a link for it or do I need an app to open it properly? Im using my iPhone right now. And that's a perfect example you given with the height and shoe size. 

 

Ive also read that subs with too big of a port area will result in the sub bottoming out easier. So im curious as to if the 6" will make a noticinle difference in sound and loudness and all that. But sounds like my port isn't too big for the sub 

Its just a link to a web page.  The calculator was created in Google Docs so I think it should work fine from your phone.  

It does take a lot of port area for these higher power systems.  Its just like the exhaust on a car though,  if you make a lot of horsepower you need to flow a lot of exhaust.  I think the "9-12 sq in per cube" guideline for aero ports is robbing a lot of folks of a LOT of output.  The nasty part about an undersized port isn't so much the port noise (which is annoying) its the port compression.  Its the silent killer,  it robs you of output but you don't hear the output you aren't getting.  Its hard to notice the absence of something.  It can easily rob you of 3 dB or more of output around tuning, that like throwing half your amplifier power (or more) out the window.  

As far as a port being too big and resulting in a sub bottoming out easier, that's at least 90% false.  If the port ISN'T big enough it will actually result in MORE cone excursion around the tuning frequency, not less.  Much below tuning I can see where a larger port MIGHT result in higher cone excursion, but at those frequencies you are at the point where the box is no longer providing mechanical control regardless of port size and you should be using something else to prevent mechanical damage (like a high pass filter AKA subsonic filter).  

[ManzKea 152]

19 minutes ago, Triticum Agricolam said:

Its just a link to a web page.  The calculator was created in Google Docs so I think it should work fine from your phone.  

It does take a lot of port area for these higher power systems.  Its just like the exhaust on a car though,  if you make a lot of horsepower you need to flow a lot of exhaust.  I think the "9-12 sq in per cube" guideline for aero ports is robbing a lot of folks of a LOT of output.  The nasty part about an undersized port isn't so much the port noise (which is annoying) its the port compression.  Its the silent killer,  it robs you of output but you don't hear the output you aren't getting.  Its hard to notice the absence of something.  It can easily rob you of 3 dB or more of output around tuning, that like throwing half your amplifier power (or more) out the window.  

As far as a port being too big and resulting in a sub bottoming out easier, that's at least 90% false.  If the port ISN'T big enough it will actually result in MORE cone excursion around the tuning frequency, not less.  Much below tuning I can see where a larger port MIGHT result in higher cone excursion, but at those frequencies you are at the point where the box is no longer providing mechanical control regardless of port size and you should be using something else to prevent mechanical damage (like a high pass filter AKA subsonic filter).  

Wow! Great information. Thanks for your input. You made a lot of sense with all the examples you've provided. Maybe if I want more out put I ahould make the box larger. 

[Triticum Agricolam 15]

5 minutes ago, ManzKea said:

Wow! Great information. Thanks for your input. You made a lot of sense with all the examples you've provided. Maybe if I want more out put I ahould make the box larger. 

Glad I could help!

Making the box bigger will get you more output, but only around the tuning frequency.  You mentioned previously that you noticed output rolled off on the higher notes.  Making the box bigger will make that effect more pronounced.  If you want to get louder overall, you need to add power and/or add cone area (along with box size).  

[ManzKea 152]

14 hours ago, Triticum Agricolam said:

Glad I could help!

Making the box bigger will get you more output, but only around the tuning frequency.  You mentioned previously that you noticed output rolled off on the higher notes.  Making the box bigger will make that effect more pronounced.  If you want to get louder overall, you need to add power and/or add cone area (along with box size).  

More pronounced? Hmmm I can't fit another sub. Could I shrink the box so it can handle more power ? 

[Triticum Agricolam 15]

6 hours ago, ManzKea said:

More pronounced? Hmmm I can't fit another sub. Could I shrink the box so it can handle more power ? 

Yes, and shrinking the box will reduce the peak in output around tuning and flatten your frequency response. This does come at the price of reduced peak output though (before you add more power). 

 

Sizing a box is is all about balancing the trade off between getting max peak output (a large box) and getting a smooth frequency response and good sound quality (with a smaller box). There isn't a single "best" size. It's always going to depend on what kind of performance is most important to each person. 

[Notorious97200 339]

OK, now you're talking to a serious guy !

 

I bought a PSP port a few years ago. It was nice, but I will never do that again : now, I use PVC tubes, and I can flare both ends.

It's not perfect as a PSP port, but it's MUCH cheaper, I can found what I need locally, ready to use.

With a good looking paint, I can even show it outside the box (to save box volume).

 

[ManzKea 152]

7 hours ago, Notorious97200 said:

OK, now you're talking to a serious guy !

 

I bought a PSP port a few years ago. It was nice, but I will never do that again : now, I use PVC tubes, and I can flare both ends.

It's not perfect as a PSP port, but it's MUCH cheaper, I can found what I need locally, ready to use.

With a good looking paint, I can even show it outside the box (to save box volume).

 

Yea he had great info. And yea the pvc works well, just need a bowl or something and a heat gun.  Flare it with no problem.