ported enclosure volume

Home / the12volt's Install Bay / Car Audio / ported enclosure volume (

Topic Closed)

Welcome Guest :)

Members

Next Page > < Prev Topic Next Topic >

audiomaninc

Copper - Posts: 108

Joined: April 18, 2007

Location: United States

Posted: July 28, 2007 at 10:28 AM / IP Logged

Alright, I have a question...I hope it's understandable. Say I have one subwoofer and the recommended vented enclosure volume is 2.0 cu. ft. If I want to add another subwoofer and build a new enclosure, using a single chamber with a slot port in the middle, does the volume of the enclosure double to 4 cu. ft., or does it stay the same at 2 cu. ft.? I'll disregard the port and sub displacement, just looking for a general answer! Thanks!

2003 Dodge Neon R/T

Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4

140.7 @ 28Hz

DYohn

Moderator - Posts: 10,741

This member has made a donation to the12volt.com. Click here for more info.

This member has been recognized as an authority in Electrical Theory. Click here for more info.

This member has been recognized as an authority in Mobile Audio and Video. Click here for more info.

Joined: April 22, 2003

Location: Arizona, United States

Posted: July 28, 2007 at 12:15 PM / IP Logged

In general, if the recommended volume for one speaker is 2 cuft then for two you'd use 4 cuft, but this will not always give you the same sort of performance so your best bet is always to use modeling software like WinISD or Unibox or BassBox and see what will happen The port geometry, on the other hand, is not so simple as simply doubling the recommended size. You need to calculate a new port for the same tuning frequency in your new larger enclosure, and realize that two woofers will move more air than one so the port opening might need to be larger.

Support the12volt.com

audiomaninc

Copper - Posts: 108

Joined: April 18, 2007

Location: United States

Posted: July 30, 2007 at 11:21 AM / IP Logged

Thank you very much! Assuming that the port opening itself might need to be larger, the length shouldn't change, correct? I've been playing with bassbox lite and find it a little more user friendly than WinISD. What do you think?

2003 Dodge Neon R/T

Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4

140.7 @ 28Hz

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: July 30, 2007 at 12:07 PM / IP Logged

Post opening size needs to be large enough to minimize noise of air rushing through it. I am not familiar enough with BassBox to know if it calculates port velocity, but you need to size the opening to keep port air velocity below about 17 m/sec. Once you have the opening sized appropriately, you can calculate the necessary length to tune the enclosure volume to the target frequency.

Support the12volt.com

audiomaninc

Copper - Posts: 108

Joined: April 18, 2007

Location: United States

Posted: July 30, 2007 at 12:16 PM / IP Logged

I remember reading about 2 years ago an article in Car Sound and Performance about calculating the resonant frequency of any car, and that for pure SPL, the idea is to have the tuning frequency match the resonant frequency of the vehicle. I've since lost the magazine, and am unable to find the article online. There were a few equations used, and if I remember correctly, the tuning frequency of the box used to achieve max SPL would change depending on where, in the vehicle the box was located. Does this make sense?

2003 Dodge Neon R/T

Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4

140.7 @ 28Hz

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: July 30, 2007 at 12:27 PM / IP Logged

Yes it does. And if you are going for pure SPL, port air velocity is a non-issue. I do not have the equations you mention right off hand, but most passenger car-sized vehicles have cabin resonant frequencies in the 60Hz range.

Support the12volt.com

audiomaninc

Copper - Posts: 108

Joined: April 18, 2007

Location: United States

Posted: July 30, 2007 at 12:51 PM / IP Logged

you say port air velocity is a non-issue, but doesn't port noise damage a speaker? Also, generally speaking, when the cabin's RF is matched by the enclosure, max spl is achieved? How does changing the woofer affect this? I understand that a physically larger woofer will move more air, increasing SPL, but does a different woofer of the same size and power input change the output? Is there a way to "max out" in terms of SPL and vehicle, assuming the vehicle is a daily driver with none other than basic electrical system modifications?

2003 Dodge Neon R/T

Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4

140.7 @ 28Hz

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: July 30, 2007 at 12:59 PM / IP Logged

audiomaninc wrote:

Wow, lots of questions. OK, here's my 2 cents.

Port noise does not damage anything. It's just if you are building a system you plan to listen to (ie: not just for SPL comp) then you want to make sure any port noise is minimized so you don't have to listen to it.

In general if you are trying to build an SPL competition vehicle, you want to maximize SPL from all available sources, so matching a subwoofer system resonance frequency to the vehicle's resonance frequency can get you a few extra dbs.

Yes, all woofers will perform differently, even two different woofers of the same size and power input. It is not just about cone size and power, it is also about displacement (Xmax) and about the enclosure. Indeed, the enclosure is by far the biggest contributor to big SPL numbers, much more so than simply large power numbers.

Finally, I am not certain what you mean by "max out" a system, but sure you can design a system for max output given the parameters of the woofer and the available system and electrical power. But for a "daily driver," unless you are building a boom car it is not about SPL, it is about sound quality. Build a system that sounds good and you will be far happier a lot longer than you will be with one that just gets loud.

Support the12volt.com

audiomaninc

Copper - Posts: 108

Joined: April 18, 2007

Location: United States

Posted: July 30, 2007 at 1:45 PM / IP Logged

Thanks for all the input! It's been a pleasure talking with you. What I mean by "max out", is simply put, is it possible to achieve the maximum spl potential of a car, or can it always be louder? I suppose it would be possible to achieve the limit of any given system, but as soon as you introduce new equipment, everything changes! I think I just answered my question!

2003 Dodge Neon R/T

Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4

140.7 @ 28Hz

aznboi3644

Gold - Posts: 2,600

This member consistently provides reliable information

Joined: May 01, 2006

Location: United States

Posted: July 30, 2007 at 2:43 PM / IP Logged

it can always be louder...but it just takes more time, more money, some more time, and even more money lol

Next Page >

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.