Sub bottoming out, port too big?

[KittyCow]

Rockford r1 12 bottoming out SUPER EASY. Like, gain knob set to 3 and 1/4 amp power, extreme bottoming. Really hoping I'm missing something obvious that you guys can help out with!! very new to box building.

basic setup info for all yall to look at and examine,

1.78 Cubic Feet not including port

28 inch long 3.5x17.5 inch L port

rockford 250.1 amp

tuned to 45hz

My current thoughts:

I am honestly completely lost as to why this is happening, my first thought is that the port is just way too large and the lack of back pressure is letting the sub bottom out, but I'm not even sure it should bottom out this bad free air. My second thought is that the tuning is just too high, but it's bottoming out at reasonable frequencies like 35hz, not just the 15hz bops. This box has taken me 2 months to build (fairly ornate design, acrylic window, led's,vinyl wrapped etc etc) so rebuilding the box isnt really an option, I could try to block off the port by gluing stuff in the port, this would make my port essentially useless but ill take that over constant bottoming. I've heard of people gluing weights to the subs cone to decrease it's effective resonance, could this be a possible solution?

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[Jeffdachef 5,000+ posts]

Easy. Its a combination of horrible box design along with improperly set gains. Should have asked and confirm with others if you are new to building and designing. What you built is a one note wonder burp box.

Depending on your preout voltage, you could be well overdriving the amp. Just because the settings are low doesnt mean you are only getting 1/4 power. Doesnt work that way. You could very well be clipping the living sh*t out if your sub right this moment.

 

[Boomin_tahoe 5,000+ posts]

Rockford r1 12 bottoming out SUPER EASY. Like, gain knob set to 3 and 1/4 amp power, extreme bottoming. Really hoping I'm missing something obvious that you guys can help out with!! very new to box building.basic setup info for all yall to look at and examine,

1.78 Cubic Feet not including port

28 inch long 3.5x17.5 inch L port

rockford 250.1 amp

tuned to 45hz

My current thoughts:

I am honestly completely lost as to why this is happening, my first thought is that the port is just way too large and the lack of back pressure is letting the sub bottom out, but I'm not even sure it should bottom out this bad free air. My second thought is that the tuning is just too high, but it's bottoming out at reasonable frequencies like 35hz, not just the 15hz bops. This box has taken me 2 months to build (fairly ornate design, acrylic window, led's,vinyl wrapped etc etc) so rebuilding the box isnt really an option, I could try to block off the port by gluing stuff in the port, this would make my port essentially useless but ill take that over constant bottoming. I've heard of people gluing weights to the subs cone to decrease it's effective resonance, could this be a possible solution?

I've never heard of that before. Who have you been listening to? And pics of this weights on cone'd subs or lies.

45Hz is way too high tbh...typically 35Hz is the popular target.

Post up pics of said 2 month long sub enclosure....which is way too long and find out it's trashed.

 

[wew lad 5,000+ posts]

I've never heard of that before. Who have you been listening to? And pics of this weights on cone'd subs or lies.
45Hz is way too high tbh...typically 35Hz is the popular target.

Post up pics of said 2 month long sub enclosure....which is way too long and find out it's trashed.

if you understand that increasing moving mass lowers fs then you'll see why adding weight would help bottoming out. problem is it's going to just make it inefficient and useless vs building an appropriate enclosure.

i mean its actually physics, generally more mass = lower resonance. not getting into super high frequency ****

 

[Boomin_tahoe 5,000+ posts]

if you understand that increasing moving mass lowers fs then you'll see why adding weight would help bottoming out. problem is it's going to just make it inefficient and useless vs building an appropriate enclosure.
i mean its actually physics, generally more mass = lower resonance. not getting into super high frequency ****

Ok well said. I just never seen weights added to subs....never.

Better off with a freshly built enclosure. Forgot to mention a proper one.

 

[mazdakid 5,000+ posts]

Are you saying you've got over 60" of port area in a box under 2 cubes? Holy shit lol

 

[garychoffmann 10+ year member]

Looking at the numbers real quick I get that you are tuned to 51hz. Now to salvage your box if you shrink the port to 1.5x 17.5 x 28. You can make that look decent by using 1 inch mdf and rounding over the edge and painting it on each side of the port. You would be tuned to roughly 31 hz with adding that. Sub may have mechanical damage from bottoming out and going past it's limits. But it may just work.

 

[wew lad 5,000+ posts]

Ok well said. I just never seen weights added to subs....never.
Better off with a freshly built enclosure. Forgot to mention a proper one.

sorry i wasnt clear, this is like designing speaker theory, not every day go throw fishing weights on a cone for them lows theory lol although ive seen people add tape on midranges ******* around

 

[Jeffdachef 5,000+ posts]

I'd get something and chop off the port wall and shrink it down

 

[shredder1 10+ year member]

Looking at the numbers real quick I get that you are tuned to 51hz. Now to salvage your box if you shrink the port to 1.5x 17.5 x 28. You can make that look decent by using 1 inch mdf and rounding over the edge and painting it on each side of the port. You would be tuned to roughly 31 hz with adding that. Sub may have mechanical damage from bottoming out and going past it's limits. But it may just work.

Good advice above.. Looks easy as well.. and it should not look bad if done right... Adding mass to subs? To change the resonance? IDK... I've seen an L7 separate the coil from the cone where they come together above the spider and get fixed using way too much epoxy with Dynamat underneath (It is what he had available at the time)... There was some pretty significant weight added in this instance and it sounded pretty much the same... (I asked specifically)... Re-port the box correctly

and if the sub is not damaged you'll be allright

 

[BOOMINGRANDPA 5,000+ posts]

yeah i bet it's just tuning.. u do have ss filter set to like 42hz i hope.. if u did a 2-2.5" wide port tuned to 35hz probably be fixed.. i need wider port lol..