Subwoofer unloading?

[ChrisB4]

So I heard to be careful with unloading issues with the sub closest to the port in a 3 common wall subwoofer box (subwoofers on one side port on the other) and I was just wandering what this is and how I can avoid it. I do not want to damage newly rebuilt subs. Or should I change the box design and go with a single slot port down the center of the box. It will be sealed off from the trunk.

Here is the box joe x designed for me and is the one in question http://www.stevemeadedesigns.com/board/topic/157840-can-someone-design-this/#entry2268577

[bkolfo4]

Pretty common problem.

Sometimes you can baffle behind the subs to help.

Every box I have run like this I have one amp per sub, so I could just use the SSF to control them. You can also just turn the SSF up high enough on a single amp setup to control the sub that is unloading.

For daily music, port in the center is the best solution.

[ChrisB4]

Pretty common problem.

Sometimes you can baffle behind the subs to help.

Every box I have run like this I have one amp per sub, so I could just use the SSF to control them. You can also just turn the SSF up high enough on a single amp setup to control the sub that is unloading.

For daily music, port in the center is the best solution.

By SSF you mean sub sonic filter? I will be tuning to 32hz, to correct the issue would I have to raise the SSF past the tuning frequency of the box or lower than 28hz which is where I was planning on setting it? Or just play around with it until its right?

If a center port is best for a daily ground pounder then I'll get that. I have never tried a 3 common wall box, and since I was sealing my system off I looked around the forum and saw almost all of the sealed trunks with the 3 common wall box.

[Joe X]

So I heard to be careful with unloading issues with the sub closest to the port in a 3 common wall subwoofer box (subwoofers on one side port on the other) and I was just wandering what this is and how I can avoid it. I do not want to damage newly rebuilt subs. Or should I change the box design and go with a single slot port down the center of the box. It will be sealed off from the trunk.

Here is the box joe x designed for me and is the one in question http://www.stevemeadedesigns.com/board/topic/157840-can-someone-design-this/#entry2268577

The port in the middle definitely helps with that, in fact I had done it port in the middle but you request it changed port to the side and so I did. The other thing that you didn't mention is that the subs were rebuilt, manufacturer specs may be no longer adequate in many cases.

Edit: Anyways I'm guessing you have not tested this setup yet, have you built the box? where are you at.

[Hugh G. Rection]

So I heard to be careful with unloading issues with the sub closest to the port in a 3 common wall subwoofer box (subwoofers on one side port on the other) and I was just wandering what this is and how I can avoid it. I do not want to damage newly rebuilt subs. Or should I change the box design and go with a single slot port down the center of the box. It will be sealed off from the trunk.

Here is the box joe x designed for me and is the one in question http://www.stevemeadedesigns.com/board/topic/157840-can-someone-design-this/#entry2268577

subwoofer unloading occurs in multiple situations, but it is all relevant to the back pressure on the sub. this is one reason you dont want to run gargantuan ratios of port area, unless you are tuning rather high for a burp type spl setup. however, this can also occur with normal ratios of port area as well, such as when you are playing well below port tuning. it is basically when there is no back pressure on the sub to keep it under control mechanically, and it starts acting as if it is running free air. youll hear people reference the term "bottoming out" alot when this happens.

as for what you mention about the sub closest to the port, "powered 4 sound" used to build a box that would do this called a "servo" box, which i really only saw as an atempt to capitalize on a design flaw. when i do a side port enclosure, i usually mount the subs away from the port to help alleviate this.

[ChrisB4]

So I heard to be careful with unloading issues with the sub closest to the port in a 3 common wall subwoofer box (subwoofers on one side port on the other) and I was just wandering what this is and how I can avoid it. I do not want to damage newly rebuilt subs. Or should I change the box design and go with a single slot port down the center of the box. It will be sealed off from the trunk.

Here is the box joe x designed for me and is the one in question http://www.stevemeadedesigns.com/board/topic/157840-can-someone-design-this/#entry2268577

The port in the middle definitely helps with that, in fact I had done it port in the middle but you request it changed port to the side and so I did. The other thing that you didn't mention is that the subs were rebuilt, manufacturer specs may be no longer adequate in many cases.

It was rebuilt by the same manufacturer which allowed more efficiency and an increase in power handling by 300 watts rms. Joe X if could change it back to center port? My Max demensions are 16.5Hx33.5Wx23.5D tuned to 32hz.

[Joe X]

Changed back to port in the middle.