Question for AI Ray and other Sub/Enclosure Experts

[Mobile Chassis Dyno]

Guys,

I have used both the search function and google to try and educate myself about the differences in displacement requirements for sealed and ported enclosures. Why is it that a ported enclosure is typically double the displacement compared to a sealed enclosure for any given subwoofer. Obviously this is the way it works. I just want to understand how a ported enclosure needs so much more displacement over a sealed enclosure. My only guess is it has something to do with how the sound waves travel inside the enclosure.

Also when talking about RMS power. Is this rating typically the same for both ported and sealed or can we figure on an increased power handling for a sealed enclosure providing we do not overheat the coil?

Be easy on my guys. I tune 1000 horsepower twin turbo mustangs and vettes. When it comes to enclosures I admit the only thing I know how to build is sealed enclosure.

[Freshman6969]

holy fuck an actual intelligent question? wow free bump for you sir

[Mobile Chassis Dyno]

holy fuck an actual intelligent question? wow free bump for you sir

I am trying. When it comes to something I do not understand it is better to ask those who have been doing this for a long time and have a good reputation regarding the question being asked.

[AMI CUSTOMS]

You have to account for the port in the displacement. That is as simple as it gets. And sealed allows the sub to load properly so you get an increase in handling, this is why 4th orders are so damn loud. LOL

[AMI CUSTOMS]

What I mean to as you might not realize is in a ported enclosure, lets say then inter dimensions of the port are 12 x 12 x 12 so that is 1 cubic ft, that subtracts from the displacement along with the subs and bracing.

[nCOMP1337]

I wish I could help ya, but it is a relief when there is a question that isnt a person fairly new to car audio trying top get others to do work for them

[Mobile Chassis Dyno]

You have to account for the port in the displacement. That is as simple as it gets. And sealed allows the sub to load properly so you get an increase in handling, this is why 4th orders are so damn loud. LOL

Damn,

I can not believe I did not think of taking port displacement into account. That makes a world of sense to me.

Thank you for the reply. Care to explain more why a 4th order is "loud"? If not I will get back to google and put my fingers to work to find the answer. Not sure what Transmission Line is considered. I had a customer come to my shop who had 4 8's in a T line and was blown away how much louder it was then my 4 12's sealed.

Thank you again.

[AMI CUSTOMS]

You have to account for the port in the displacement. That is as simple as it gets. And sealed allows the sub to load properly so you get an increase in handling, this is why 4th orders are so damn loud. LOL

Damn,

I can not believe I did not think of taking port displacement into account. That makes a world of sense to me.

Thank you for the reply. Care to explain more why a 4th order is "loud"? If not I will get back to google and put my fingers to work to find the answer. Not sure what Transmission Line is considered. I had a customer come to my shop who had 4 8's in a T line and was blown away how much louder it was then my 4 12's sealed.

Thank you again.

4th order? It is basically both boxes combined, it is a sealed chamber that the subs are in and on front of that is a ported chamber, the ratio of ported cubes to sealed cubes determines the output and it is basically the best of both worlds, only thing is a 4th order for just one 15 is huge generally 15+ cubes. And T-line is just a box with a very long ass port more or less.

Edited January 30, 2011 by AMI CUSTOMS

[Mobile Chassis Dyno]

A friend of mine who is pretty sharp in building ported enclosures is offering to both design and build an enclosure for me for free so I can see the difference between ported vs sealed. All I have to do is buy the materials. This is really tempting considering the fact my answer to increased SPL is to add cone area and more power. I have been telling him I want to go from my 4 12's and 1000 watts of RMS power to 4 15's and 3000 watts of rms (Staying sealed). He said why bother spending that kind of money when I can get you louder with just an enclosure. I think I am going to give him the green light and build me an enclosure. I am probably the only dyno shop in the country who owns a twin sensor term lab and does not do any car audio installs. LOL.

[Ray]

Sorry I missed this..

In a sealed box you are only hear the front wave of the speaker..

Kind of like how a piston on has compression at tdc

Imagine if a piston would build compression on both the up and down stroke..

Same theory, kind of.. With porter you are able to "hear" both the front and back wave.

In theory, 2 of your 12's in a potted box, will be just as loud as 4 in your sealed box.