Subwoofer Unloading Issues

[TRTC360]

I have an American Bass XFL 12" in a dual 12" ported box built for my transam, there's a dividing wall that separates both subs which is why I can run only one sub while I wait to buy the 2nd one. I plan on building a new box eventually, but for the time being I have to keep this box, the issue i'm having is that the box is tuned to 36hz but the sub unloads on anything below 32hz, I know playing below tuning shouldn't be done but i'm not even running rated power to the sub so it shouldn't unload as bad as it is, my question is when I rebuild the box with a bit more cubic feet and a much bigger port to get the proper port area still tuned to 36hz will the sub still unload since the box is bigger and the port is bigger? or will the properly designed port keep the sub more under control? the ports the box has now are very tiny but are indeed tuned to 36hz.

[Joe X]

Post the external dims of the box and the ports, and really not sure what you mean, the sub bottoms out? or you can't listen the lows? maybe some pics?

[TRTC360]

Let me rephrase my question.

For all you box builders out there, i've always wondered, can insufficient port area cause a subwoofer to unload before it should? for example a prefab box that is indeed tuned to 36hz vs a good custom built enclosure tuned to 36hz will the sub unload less in the better built box simply because it has proper port area?even though the well built box is a bit bigger and tuned to the same frequency?

Edited August 4, 2012 by TRTC360

[P4killer_]

it depends what you mean by unloading.. and loading is kinda a vague subject for me, but usually "unloading" or loss of cone control or bottoming out has to do with tuning/ port area. too much port usually make the setup more sensitive in regards to playing below tuning. Which means running alot of port and playing below tuning will cause more mechanical stress \on the sub.. same thing with running too much air space.. you will gain efficiency with larger enclosures but it will be more sensitive to doing less than ideal things ie:. playing below tuning.

running too much port kinda makes the sub act like it playing free air, as it cant build up enough pressure in the enclosure. running too little port chokes the sub and makes it act like your running a sealed box, too much pressure and it cant get out fast enough.

generally speaking, playing below tuning isnt ideal, but it can be done without too many problems i mean i kinda consider 10hz max below tuning to be safe to a point.. more than that and your asking for issues, but thats not to say i havent seen it or done it.

you mostly see loading issues when you have multiple subs and they are different distances from the port where there is a significant difference in how the pressure builds throughout the box.

what youre hearing depends on the specs of the box.. if its alot of port and or airspace below tuning is just gonna sound muddy like shit. usually bottoming out ppl hear metal noises like the coil hitting the bottom of the motor usually caused by too much power too far below tuning..

and how do you know its tuned at 36hz.. how did you verify that? or maybe you just typed in the box specs, i guess that works.

[bassface]

whats your subsonic filter set at?

[Crandis16]

I believe that if you increase the volume you will have more unloading issues. More volume = more efficiency and less power handling

Edit: someone correct me if I'm wrong.... noob still learning

Edited August 4, 2012 by Crandis16

[TRTC360]

it depends what you mean by unloading.. and loading is kinda a vague subject for me, but usually "unloading" or loss of cone control or bottoming out has to do with tuning/ port area. too much port usually make the setup more sensitive in regards to playing below tuning. Which means running alot of port and playing below tuning will cause more mechanical stress \on the sub.. same thing with running too much air space.. you will gain efficiency with larger enclosures but it will be more sensitive to doing less than ideal things ie:. playing below tuning.

running too much port kinda makes the sub act like it playing free air, as it cant build up enough pressure in the enclosure. running too little port chokes the sub and makes it act like your running a sealed box, too much pressure and it cant get out fast enough.

generally speaking, playing below tuning isnt ideal, but it can be done without too many problems i mean i kinda consider 10hz max below tuning to be safe to a point.. more than that and your asking for issues, but thats not to say i havent seen it or done it.

you mostly see loading issues when you have multiple subs and they are different distances from the port where there is a significant difference in how the pressure builds throughout the box.

what youre hearing depends on the specs of the box.. if its alot of port and or airspace below tuning is just gonna sound muddy like shit. usually bottoming out ppl hear metal noises like the coil hitting the bottom of the motor usually caused by too much power too far below tuning..

and how do you know its tuned at 36hz.. how did you verify that? or maybe you just typed in the box specs, i guess that works.

thanks for the response man, my problem is that I think not having nearly enough port area for what i'm tuned at is causing my sub to unload below tuning before it should, my friend's box is tuned to 30hz and he can play 22hz with ease, but his box has lots of port area. I know i'm tuned to 36hz because i've ran lots of test tones through my sub and it moves the least at 36hz. Just as an example, box A is 4 cubic feet tuned to 36hz with 8 sqin of port per cubic foot, box B is also 4 cubic feet tuned to 36hz but with 14sqin of port per cubic foot, will the sub unload more below tuning in box A or box B?

[bdog]

for now your just going to have to adjust your ssf and no one can tell you how you next box will react but yes with the ldea port and volume u will have better cone control

[bkolfo4]

When you play a sub below tuning, it is like playing it sitting out on a table, unless the port is so small the sub acts like a leaky sealed box.

Either way, most subs will not handle anywhere near their THERMALLY rated power handling in one of these conditions.

Edit - changing the port size is not going to help. Either tune lower to play the lower notes, or set the subsonic filter higher to control the excursion.

Edited August 4, 2012 by bkolfo4

[bassface]

You may be able to try stuffing it with polyfill also.