10" TC OEM with 104sq in of port

[audioholic 5,000+ posts]

Rashaddd, I think you took my original comments in the previous thread abit too literal. If that's my fault... my bad. Yes, the port can/will/does affect total air displaced. I thought this was obvious, if you build a new box with a 1/4" diameter port, the port will affect total air moved (air displacement will be choked down).

I thought the discussion had evolved into why there is a difference... for example, our discussion on surface area of the ports and the friction it causes.

 

[tommyk90 5,000+ posts]

Where is the delta of air if there is more air coming out of the port than being visibly moved by the sub? It would have to be pressure inside the box right? Would it be added pressure or lack thereof?
And I agree, if I had a meter on hand, I'd have had numbers before I even thought about posting any of this.

Yes, the pressure is contained within the enclosure. Which is why my single 10" box would meter MUCH higher inside the enclosure than your box. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Which is also why a larger box is usually more efficient (read: louder) given the same port area and power. There is a law of diminishing returns here though. At some point the added enclosure size becomes a hinderance. That point is largely dependant on the sub, power, and setup though.

 

[Rashaddd 5,000+ posts]

Yes, the pressure is contained within the enclosure. Which is why my single 10" box would meter MUCH higher inside the enclosure than your box. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Which is also why a larger box is usually more efficient (read: louder) given the same port area and power. There is a law of diminishing returns here though. At some point the added enclosure size becomes a hinderance. That point is largely dependant on the sub, power, and setup though.

I'm confused. Are you saying a smaller or a larger box will meter louder? Assuming you are not reaching mechanical limits, and power/tuning/port area are the same. (disregarding diminishing returns)

 

[tommyk90 5,000+ posts]

I'm confused. Are you saying a smaller or a larger box will meter louder? Assuming you are not reaching mechanical limits, and power/tuning/port area are the same. (disregarding diminishing returns)

Theres no set answer. A larger box CAN have the ability to meter louder with less power, HOWEVER a smaller box and more power usually leads to a higher score.

While a larger box will be louder with say, 500 watts, it will run out of steam as more power is added because of the decreased power handling/inability to pressurize the enclosure (and thus air displacement will not increase).

A smaller box will increase mechanical power handling and raise internal pressure, so if you can find the best balance of port area, power handling, and enclosure pressure, that=best SPL.

Honestly, there's no way to tell without building and testing. There's far too many variables.

 

[Rashaddd 5,000+ posts]

Theres no set answer. A larger box CAN have the ability to meter louder with less power, HOWEVER a smaller box and more power usually leads to a higher score.
While a larger box will be louder with say, 500 watts, it will run out of steam as more power is added because of the decreased power handling/inability to pressurize the enclosure (and thus air displacement will not increase).

A smaller box will increase mechanical power handling and raise internal pressure, so if you can find the best balance of port area, power handling, and enclosure pressure, that=best SPL.

Honestly, there's no way to tell without building and testing. There's far too many variables.

I think I understand what you're saying.

Just wondering, can you explain the physics of internal pressure and how it affects external pressure? Also again it'd be nice if we could talk on an IM, just easier to say more, if you're up for it

 

[tommyk90 5,000+ posts]

I think I understand what you're saying.
Just wondering, can you explain the physics of internal pressure and how it affects external pressure? Also again it'd be nice if we could talk on an IM, just easier to say more, if you're up for it

A very simple answer would be to tell you that creating higher pressure inside the enclosure can lead to increased air displacement through the ports as well as air velocity.

Higher pressure inside the enclosure will in essence "force" more air through the port, at an increased pressure as well. And, as we know, more pressure can lead to a higher SPL score, generally speaking. This, of course, is a best case scenario where the enclosure size and port size/length is optimal.

 

[Rashaddd 5,000+ posts]

A very simple answer would be to tell you that creating higher pressure inside the enclosure can lead to increased air displacement through the ports as well as air velocity.
Higher pressure inside the enclosure will in essence "force" more air through the port, at an increased pressure as well. And, as we know, more pressure can lead to a higher SPL score, generally speaking. This, of course, is a best case scenario where the enclosure size and port size/length is optimal.

So how does port area play in to this? Are you saying a higher velocity is better (assuming there's not a ton of turbulence)? vs making the port big enough that it has relatively low velocity, but is moving the same amount of air?

 

[tommyk90 5,000+ posts]

So how does port area play in to this? Are you saying a higher velocity is better (assuming there's not a ton of turbulence)? vs making the port big enough that it has relatively low velocity, but is moving the same amount of air?

Port area is crucial in determining the pressure at which the air is leaving the port(s) and also the amount of air that is leaving.

Like I said, there's an optimal range at which the pressure and volume is at the correct levels. Having one without the other won't really benefit you at all.

Right now you seem to have a lot of velocity but not a lot of pressure. While this makes for a convincing visual effect, without some numbers behind it this is merely a theory.

Also, the enclosure itself will dictate how the port acts as well.

The bottom line is you can't make any generalities about how something will act/perform.

 

[Rashaddd 5,000+ posts]

Port area is crucial in determining the pressure at which the air is leaving the port(s) and also the amount of air that is leaving.
Like I said, there's an optimal range at which the pressure and volume is at the correct levels. Having one without the other won't really benefit you at all.

Right now you seem to have a lot of velocity but not a lot of pressure. While this makes for a convincing visual effect, without some numbers behind it this is merely a theory.

Also, the enclosure itself will dictate how the port acts as well.

The bottom line is you can't make any generalities about how something will act/perform.

Gotcha. So, to summarize, essentially the reason what I posted probably wouldn't do well, is because of a lack of internal pressure, or in other words a lack of force in the port, regardless of (at least 'apparent') velocity, correct?

And I understand in the real world it tends to all be a guessing and testing game, but I want to make sure I understand a few things:

Some people have gained, simply by dropping sub size or number of subs, this would be explained likely by there being above optimal internal pressure, right? So if you gain by increasing sub size/number, it would indicate that you likely didn't have enough internal pressure, right(or at least not too much)?

I see my mistake now, the ignorance to the role that pressure inside the box plays, would you agree? And yes I understand a car environment changes everything, just ignoring that for now.

Actually all makes alot more sense when that is thrown into the 'equation' so to speak. And this is why I really made the thread in the first place, to discuss and hopefully get a better understanding of the whole system in general and what I was seeing //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[tommyk90 5,000+ posts]

Gotcha. So, to summarize, essentially the reason what I posted probably wouldn't do well, is because of a lack of internal pressure, or in other words a lack of force in the port, regardless of (at least 'apparent') velocity, correct?
And I understand in the real world it tends to all be a guessing and testing game, but I want to make sure I understand a few things:

Some people have gained, simply by dropping sub size or number of subs, this would be explained likely by there being above optimal internal pressure, right? So if you gain by increasing sub size/number, it would indicate that you likely didn't have enough internal pressure, right?

I see my mistake now, the ignorance to the role that pressure inside the box plays, would you agree? And yes I understand a car environment changes everything, just ignoring that for now.

Actually all makes alot more sense when that is thrown into the 'equation' so to speak. And this is why I really made the thread in the first place, to discuss and hopefully get a better understanding of the whole system in general and what I was seeing //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Sounds good to me.

Sorry if I seemed a bit hostile before, it just seemed like you were being a little hard-headed over the situation. It just seemed as though you wanted to understand the concept a little bit better.

Anyways, yes you are correct that it all comes down to a lot of building and testing. If it was as easy as typing in some formula and BAM getting numbers, then everyone would be loud. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Rashaddd 5,000+ posts]

Cool, and thanks for taking the time